Various molds and molding tools

Molds, various molds, and tools used in industrial production to obtain the required products by injection molding blow molding, extrusion, die casting or forging, smelting, stamping, and other methods.

In short, a mold is a tool used to make shaped articles. This tool is composed of various parts, and different molds are composed of different parts. It mainly realizes the processing of the shape of the article by changing the physical state of the formed material.

Under the action of external force, the blank becomes a tool with a specific shape and size. Widely used in punching, die forging, cold heading, extrusion, powder metallurgy parts compression, pressure casting, and engineering plastics, rubber, ceramics, and other product compression molding or injection molding processing.

The mold has a specific contour or cavity shape, and the use of a contour shape with a cutting edge can separate the blanks according to the contour shape (punching). Using the shape of the inner cavity can make the blank obtain a corresponding three-dimensional shape.

The mold generally includes two parts, a movable mold and a fixed mold (or convex mold and concave mold), and the two can be divided and combined. When separated, the product is taken out, and when closed, the blank is injected into the mold cavity to form.

Molds are precision tools with complex shapes and withstand the expansion force of the blank. They have high requirements for structural strength, stiffness, surface hardness, surface roughness, and processing accuracy. The development level of mold production is one of the important signs of machinery manufacturing.

Mold types

There are many types of molds

According to the processing object and processing technology, it can be divided into:

①Mold for processing metal.

②Processing non-metallic and powder metallurgy molds.     

Including plastic injection molds (such as two-color molds, compression molds and extrusion molds, etc.), rubber molds, and powder metallurgy molds. According to the structural characteristics, the die can be divided into flat punching die and cavity die with space. The mold is generally a single piece, small-batch production.

Mold classification

According to the different materials

Hardware molds, plastic injection molds, and their special molds.

Hardware molds are divided into: including stamping dies (such as punching dies, bending dies, deepening dies, turning dies, shrinking dies, undulating dies, bulging dies, shaping dies, etc.), forging dies, extrusion die, die casting die, etc.;

Non-metal molds are divided into plastic molds, inorganic non-metal molds, sand molds, vacuum molds, and paraffin molds.

Among them, with the rapid development of polymer plastics, plastic molds are closely related to people’s lives. Plastic molds can generally be divided into injection molding molds, extrusion molding molds, gas-assisted molding molds, etc.

Mold composition

In addition to the mold itself, it also needs a mold base, a mold frame, a mold core leading to a part ejection device, etc. These parts are generally made into a universal type. Mold companies need to be bigger and more refined. According to market demand, technology, capital, equipment, and other conditions, product positioning and market positioning should be determined.

These practices are especially worthy of learning and learning from small mold companies, and concentrate on gradually forming their own technological advantages and product advantage. Therefore, China’s mold companies must actively strive to learn from the experience of these advanced foreign companies in order to better their future development.

Mold material

The most important factors for mold materials are thermal strength and thermal stability. Commonly used mold materials: working temperature, molding materials, mold materials

<300℃ zinc alloy Cr12, Cr12MoV, S-136, SLD, NAK80, GCr15, T8, T10.

300～500℃ aluminum alloy, copper alloy 5CrMnMo, 3Cr2W8, 9CrSi, W18Cr4V, 5CrNiMo, W6Mo5Cr4V2, M2.

500～800℃ Aluminum alloy, copper alloy, steel titanium GH130, GH33, GH37.

800～1000℃ Titanium alloy, steel, stainless steel, nickel alloy K3, K5, K17, K19, GH99, IN100, ЖC-6NX88, MAR-M200, TRW-NASA, WA.

>1000℃ Nickel alloy Copper-based alloy mold, cemented carbide mold.

Classification of mold pouring system

According to the different casting systems, plastic molds can be divided into three categories:

• Large gate injection mold: the runner and gate are on the parting line, and the product is demolded together with the product when the injection mold is opened. The design is the simplest, easy to process, and the cost is low, so many people use the large gate system to operate.

The plastic injection mold structure is divided into two parts: moving mold and fixed mold. The active part of the injection machine is the moving mold (mostly the ejection side), and the general inactivity at the injection molding end of the injection machine is called fixed mold. 

Because the fixed mold part of the large gate injection mold is generally composed of two steel plates, this type of structural injection mold is also called a two-plate mold. The two-plate mold is the simplest structure in the large gate injection mold.

• Small gate injection mold: runner and gate are not on the parting line, generally directly on the product, so it is necessary to design an additional set of gate parting line, the design is more complicated, the processing is more difficult, and it is generally selected according to the product requirements small gate.

The fixed part of the fine small gate injection mold is generally composed of three steel plates, so this type of structural mold is also called a three-plate mold. The three-plate mold is the simplest structure in the small gate injection mold.

• Hot runner mold: The structure of this kind of mold is roughly the same as the small gate injection mold. The biggest difference is that the runner is in one or more hot runner plates and hot mouths with a constant temperature. There is no cold material demoulding, runner and pouring the outlet is directly on the product, so the runner does not need to be demolded.

This system is also called a waterless system, which can save raw materials. It is suitable for the situation where the raw materials are expensive and the product requirements are high.

It is difficult to design and process, and the mold cost is high. The hot runner system, also known as the hot runner system, is mainly composed of a hot gate sleeve, a hot runner plate, and a temperature-controlled electric box.

Our common hot runner system has two forms: single-point hot gate and multi-point hot gate. The single-point hot gate is to use a single hot gate sleeve to directly inject the molten plastic into the cavity.

It is suitable for the plastic mold with a single cavity and single gate; the multi-point hot gate is to branch the molten material to each through the hot runner plate The split heat gate sleeve then enters the cavity, which is suitable for single-cavity multi-point feeding or multi-cavity molds.

Molding classification

(1) Injection molding

The plastic is first added to the heating barrel of the injection molding machine, the plastic is heated and melted, and driven by the screw or plunger of the injection molding machine, it enters the injection mold cavity through the gate and the mold pouring system, and is hardened and shaped into injection molding due to physical and chemical effects products.

Injection molding is composed of injection, holding pressure (cooling) and plastic parts demoulding process constitutes a cyclic cycle, so injection molding has a periodic feature.

Thermoplastic injection molding has a short molding cycle, high production efficiency, low wear of the melt on the mold, and can mass-produce plastic parts with complex shapes, clear surface patterns and marks, and high dimensional accuracy; but for plastics with large wall thickness changes Parts, it is difficult to avoid molding defects.

The anisotropy of plastic parts is also one of the quality problems. All possible measures should be adopted to minimize them.

(2) Compression molding

Commonly known as compression molding, it is one of the earliest methods of forming plastic parts. Compression molding is to add plastic directly to an open mold cavity with a certain temperature, and then close the injection mold, the plastic melts into a flowing state under the action of heat and pressure.

Due to physical and chemical effects, the plastic is hardened into a plastic part with a certain shape and size that remains unchanged at room temperature.

Compression molding is mainly used for molding thermosetting plastics, such as phenolic molding powder, urea-formaldehyde and melamine-formaldehyde molding powder, glass fiber reinforced phenolic plastic, epoxy resin, DAP resin, silicone resin, polyimide, and other molding compounds.

It can also process unsaturated polyester pellets (DMC), sheet molding compound (SMC), prefabricated integral molding compound (BMC), etc.

Under normal circumstances, the compression mold is often divided into three types: overflow type, non-flood type, and semi-flood type according to the matching structure of the upper and lower molds of the compression film.

(3) Extrusion molding

It is a molding method to make plastics in a viscous flow state through a die with a specific cross-section shape under high temperature and certain pressure, and then form a continuous profile with a desired cross-sectional shape at a lower temperature.

The production process of extrusion molding is to prepare molding materials, extrusion molding, cooling, and shaping, traction and cutting, post-processing of extruded products (tempering or heat treatment).

During the extrusion molding process, pay attention to adjusting the temperature, screw rotation speed, traction speed, and other process parameters of the heating section of the extruder barrel and the die of the die in order to obtain qualified extrusion profiles.

Pay particular attention to adjusting the rate at which the polymer melt is extruded from the die. Because when the extrusion rate of the molten material is low, the extrudate has a smooth surface and a uniform cross-sectional shape; but when the extrusion rate of the molten material reaches a certain limit, the surface of the extrudate becomes rough and tarnished, Sharkskin, orange peel pattern, distorted shape, etc.

When the extrusion rate is further increased, the surface of the extrudate is distorted, even splitting and breaking into melt fragments or cylinders. Therefore, control of the extrusion rate is crucial.

(4) Injection casting

Also known as casting. The plastic raw material is added into the preheated charging chamber, and then the pressure column is placed in the charging chamber to lock the mold. The pressure is applied to the plastic through the pressure column.

The plastic melts into a flowing state under high temperature and high pressure and enters the cavity through the pouring system. Gradually solidified into plastic parts. This molding method is also called transfer molding.

Pressure injection molding is suitable for plastics that are lower than solid plastics. In principle, plastics that can be compression molded can also be molded by pressure injection. But the molding material is required to have good fluidity in the molten state when it is lower than the curing temperature, and a larger curing rate when it is higher than the curing temperature.

(5) Hollow molding

It is to fix the trend of tubular or sheet-shaped blanks made by extrusion or injection, which are still in a plasticized state, in the forming mold, and immediately pass compressed air to force the blanks to expand and stick to the wall surface of the mold cavity.

After cooling and setting, the mold is demolded to obtain a processing method of the hollow product required. Plastics suitable for hollow molding are high-pressure polyethylene, low-pressure polyethylene, hard polyvinyl chloride, soft polyvinyl chloride, polystyrene, polypropylene, polycarbonate, etc.

According to different parison molding methods, hollow molding is mainly divided into extrusion blow molding hollow molding and injection blow molding hollow molding.

The advantage of extrusion blow molding hollow molding is that the structure of the extruder and the extrusion blow mold is simple, but the disadvantage is that the wall thickness of the parison is inconsistent, which is likely to cause uneven wall thickness of plastic products. The figure on the right is a schematic diagram of the principle of extrusion blow molding hollow molding.

The advantage of injection blow molding hollow molding is that the wall thickness of the parison is uniform and there is no flash. Because the injection parison has a bottom surface, the bottom of the hollow product will not be stitched and seamed, which is not only beautiful but also high in strength.

The disadvantage is that the molding equipment and molds used are expensive, so this molding method is mostly used for mass production of small hollow products, and there is no extensive method for extrusion blow molding hollow molding in use.

(6) Die-casting mold

Die-casting molds are also called transfer molds. Plastic material is added to the preheated charging chamber, and then pressure is applied to the pressure column. The plastic melts under high temperature and pressure and enters the cavity through the casting system of the mold. It is gradually hardened and molded.

This molding method is called die-casting molding. The mold used Called die-casting mold. This kind of mold is mostly used for molding thermosetting plastics.

In addition, there are foam plastic molding molds, glass fiber reinforced plastic low-pressure molding molds, and so on.

Other categories of mold

(1) Hot runner mold

With the help of the heating device, the plastic in the pouring system will not solidify, nor will it demold with the product, so it is also called a runner less mold. Advantages:

1) No waste

2) Can reduce injection pressure, can use multi-cavity mold

3) Can shorten the molding cycle

4) Improve product quality Features suitable for hot runner molding plastics

5) The melting temperature range of plastics is wide. At low temperatures, the fluidity is good, and at high temperatures, it has good thermal stability.

6) It is sensitive to pressure and does not flow without pressure, but can flow when pressure is applied.

7) The specific heat is good, so as to cool down quickly in the mold. Available hot runner plastics are PE, ABS, POM, PC, HIPS,

1. There are two commonly used hot runners

1) Heated runner mold

2) Adiabatic runner mold.

(2) Hard mold

The steel plate used for the inner mold requires heat treatment after being bought, such as quenching and carburizing, to meet the requirements of use. Such an injection mold is called a hard mold. For example, the inner mold uses H13 steel, 420 steal, and S7 steel.

(3) Soft mold (below 44HRC)

The steel used for the inner mold parts can be used without heat treatment after being bought. Such an injection is called a soft mold. For example, the inner module adopts P20 steel, ace steel, 420 steel, NAK80, aluminum, beryllium copper.

Double injection molding principle

Fundamental:

Double injection molding mainly uses two injection tubes of a double injection molding machine and two sets of molds to form a double injection product through two moldings in order.

Work steps:

1. The raw material A is injected into the molding tube A once to form a single shot product A.
2. After periodic mold opening, product A remains in the male mold, and the forming motorized template rotates to B mold clamping.
3. The raw material B is injected into the molding tube twice through the B tube to form a double shot product, which is ejected after the mold is opened.

Main points of mold design

1. Review items before the design

      2.Work steps

1. Mold material
2. Molded products
3. Molding machine selection
4. The basic structure of a mold base
5. Important items of mold design
6. Multi-color injection combination
7. Sprue system

(1) The injection pressure is low.

(2) The rapid filling is completed, which can increase the output.

(3) It can be shot evenly and the product quality is good.

(4) Reduce waste materials and shorten injection time.

3. Molding equipment:

(1) The injection volume of each injection cylinder determines which cylinder is used for which color.

(2) The position and stroke of the striker.

(3) The configuration of water, oil, and circuit on the rotating disk.

(4) The bearing weight of the rotating disk.

4. Mold base design: mold core configuration design

First of all, considering that the male side of the mold must be rotated by 180 degrees, the mold core must be arranged symmetrically, otherwise, the mold cannot be closed.

(1) Guide pin: It has the function of guiding male and female molds. It is necessary to maintain concentricity in multi-color molds.

(2) Return pin: Because the mold must rotate, the ejector plate must be fixed, and spring is added to the return pin to keep the ejector plate stable.

(3) Positioning block: ensure that the two mold bases are not offset due to the problem of screw clearance when fixed to the large fixed plate.

(4) Adjustment block (wear-resistant block): It is mainly used when the mold height z coordinate value error occurs during mold clamping.

(5) Ejection mechanism: The design of the ejection method is the same as the general mold.

(6) Cooling circuit design: The cooling circuit design of mold one and mold two should be as same as possible.

Mold production inspection

The control of the raw materials of the mold is carried out from the following aspects:

1. Macro inspection

The chemical composition is decisive for ensuring the performance of the steel, but the composition is qualified and cannot fully explain the performance of the steel. Due to the unevenness of the internal organization and composition of the steel, the macroscopic inspection largely supplements this deficiency.

Macroscopic inspection can observe the crystallization of steel, the continuity of steel, and the non-uniformity of certain components.

Standard “Structure Steel’s Low Power Defect Rating Chart” GB1979

There are 8 common defects in the macro: segregation, looseness, inclusions, shrinkage holes, bubbles, white spots, cracks, and folding.

2.1 Evaluation of the annealed structure

The purpose of annealing is to reduce the hardness of the steel and facilitate machining, as well as to prepare for the subsequent heat treatment.

The annealed structure of carbon tool steel is evaluated according to the first-grade rating chart of GB1298.

2.2, Carbide unevenness

Cr12 type of austenite steel contains a large number of eutectic carbides in the structure. The non-uniformity of carbides has a very important effect on serviceability, so the distribution of carbides must be strictly controlled.

All in all, due to the cumbersome production objects of the mold production plant and workshop, and the number of single parts and small batches, it brings certain difficulties to the establishment and management of mold production quotas, plus the production methods of various factories and workshops.

The equipment and technical qualities are not the same, so when formulating quotas, it is necessary to find appropriate methods according to the actual conditions of the factory and the workshop to work out advanced and reasonable quotas for working hours to improve labor productivity.

Mold production process

The mold is a model, and the products are made according to this model, but how the mold is produced may not be answered by most of the mold professionals.

The mold has played an irreplaceable role in our lives, our daily necessities Most of them are inseparable from molds, such as computers, telephones, fax machines, keyboards, cups, and other plastic products.

In addition, the covers of cars and motorcycle engines are also made of molds. More than 20,000 kinds of molds are used. So the role of modern life molds cannot be replaced. As long as mass production cannot be separated from molds.

So how is the mold made?

The following is a brief introduction to the modern mold production process.

1) ESI (Earlier Supplier Involvement early participation): This stage is mainly a technical discussion between the customer and the supplier on product design and mold development, etc.

The main purpose is to let the supplier clearly understand the product The designer’s design intention and accuracy requirements also allow product designers to better understand the mold production capabilities and product process performance, thereby making a more reasonable design.

2) Quote (Quotation):   

Including the price of the mold, the life of the mold, the turnover process, the tonnage required by the machine, and the delivery time of the mold. (More detailed quotation should include information such as product size and weight, mold size and weight.)

3) Order (Purchase Order):  

Customer order, deposit issuance, and supplier order acceptance.

4) Mold production planning and scheduling arrangement (Production Planning and Schedule Arrangement): 

At this stage, it is necessary to reply to the customer for the specific date of mold delivery.

5) Mold design (Design): 

The design software that may be used includes Pro/Engineer, UG, Solidworks, AutoCAD, CATIA, etc.

6) Procurement materials

7) Molding (Machining): 

The processes involved are roughly turning, gong (milling), heat treatment, grinding, computer gong (CNC), electric spark (EDM), wire cutting (WEDM), coordinate grinding (JIG GRINDING), Laser lettering, polishing, etc.

8) Mold assembly (Assembly)

9) Trial Run

10) Sample Evaluation Report (SER)

11) Approval of model evaluation report (SER Approval)

Principles of mold design

Because different molding molds have been applied in many fields, and the manufacturing technology of professional molds has also undergone certain changes in these years, so in this part, the general design rules of vacuum plastic molding molds are summarized.

The design of the vacuum blister forming mold includes batch size, forming equipment, precision conditions, geometric design, dimensional stability, and surface quality.

1. For batch size experiment, the mold output is small, and it can be manufactured with wood or resin. However, if the experimental mold is used to obtain data about shrinkage, dimensional stability, and cycle time of the product, a single cavity mold should be used for the experiment and can be used under production conditions.   Molds are generally made of gypsum, copper, aluminum, or aluminum-steel alloys, and aluminum-resin is rarely used.
2. Geometric shape design. When designing, it is often necessary to comprehensively consider the dimensional stability and surface quality. For example, product design and dimensional stability require the use of female molds (female molds), but products with high gloss on the surface require the use of male molds (male molds). The point, so that products can be produced under optimal conditions. Experience has shown that designs that do not meet actual processing conditions often fail.
3. Dimensional stability. During the molding process, the surface of the plastic part in contact with the mold is better than the dimensional stability of the part leaving the mold. If the thickness of the material needs to be changed in the future due to the rigidity of the material, it may cause the male mold to be converted into the female mold. The dimensional tolerance of plastic parts cannot be less than 10% of the shrinkage rate.
4. On the surface of the plastic part, as far as the molding material can be wrapped, the surface structure of the visible side of the plastic part should be formed at the contact with the mold. If possible, the smooth surface of plastic parts should not be in contact with the mold surface. It is like the case of using a female mold to make a bathtub and a laundry tub.
5. Retouching. If a mechanical horizontal saw is used to saw off the clamping edge of the plastic part, there must be at least 6 to 8 mm of margin in the height direction. Other dressing work, such as grinding, laser cutting, or jet flow, must also have a margin. The gap between the cutting lines of the blade die is the smallest, and the distribution width when the punching die is trimmed is also very small. These should be paid attention to.
6. Shrinkage and deformation, plastic is easy to shrink (such as PE), and some plastic parts are easy to deform. In any case, the plastic parts will deform during the cooling stage. Under this condition, it is necessary to change the shape of the forming mold to adapt to the geometric deviation of the plastic parts. For example: Although the wall of the plastic part remains straight, its reference center has deviated from 10mm; the mold base can be raised to adjust the amount of shrinkage of this deformation.
7. The amount of shrinkage, the following shrinkage factors must be considered when manufacturing the blister forming mold. ①Shrinkage of molded products. If the shrinkage of the plastic cannot be clearly known, it must be sampled or obtained by testing with a similarly shaped mold. Note: This method can only get the shrinkage, not the deformation size. ②Shrinkage caused by the adverse effects of intermediate media, such as ceramics, silicone rubber, etc. ③ The shrinkage of the material used in the mold, such as the shrinkage when casting aluminum.

Mold design

According to the national occupational definition, mold design is: personnel engaged in the digital design of enterprise molds, including cavity molds and cold punching molds. On the basis of traditional mold design, fully use digital design tools to improve the quality of mold design, and shorten the mold design cycle.

Mold design concept

The overall structure of the stamping die can be divided into two parts:

(1) Common parts.

(2) The part that changes according to the product. Common parts can be standardized or standardized, and parts that vary according to products are difficult to standardize.

Specification

1. The composition of the template

The composition of the stamping die will be divided into two types: collocation configuration and inverse configuration structure according to the type and composition of the die. The former is the most commonly used structure, and the latter structure is mainly used for stretching forming molds, or matching special molds.

2. Mold specifications

(1) Mold size and locking screw

The size of the template should be larger than the work area and select the standard template size. The position of the template locking screw is related to the type of mold and the size of the template. Among them, the single engineering mold is most often configured with locking screws at the four corners, and the most standard form of the work area can be widely used. Long molds and continuous molds are most often placed at the four corners and in the middle using locking screws.

(2) Thickness of template

The thickness of the template has an absolute relationship with the structure of the mold, the type of stamping processing, the force of stamping processing, and the accuracy of stamping processing. It is difficult to determine the thickness of the mold based on theoretical calculations. Generally, it is obtained from experience. The thickness of the template used in the design should be as few as possible. It should be standardized with the mold height and clamping height to facilitate procurement and inventory management.

Template design

The main templates of continuous molds include punch fixing plate, pressure plate, concave template, etc. The structure design is based on the accuracy of stamping products, the number of production, the processing equipment and processing methods of the mold, and the maintenance methods of the mold. Form: (1) monoblock, (2) yoke, (3) inset.

1. Monolithic

The monolithic template is also called an integrated structure, and its processing shape must be closed. The monolithic template is mainly used for molds with a simple structure or low accuracy. The processing method is mainly cutting (no heat treatment is required). The template using heat treatment must be subjected to wire cutting or electrical discharge machining and grinding. When the template size is long (continuous mold), two or more integrated models will be used.

2. Yoke

The central part of the yoke template is processed into a concave groove to assemble a block product. Its structure depends on the application requirements, and the concave groove can be formed by other templates. The advantages of this yoke template structure are easy processing of the groove, the width of the groove can be adjusted, and good processing accuracy. But low rigidity is its disadvantage.

The design considerations of the yoke template are as follows:

(1) The fitting of the yoke plate structural part and the block parts adopt the middle or light fitting method, such as strong press fit will change the yoke plate.

(2) The yoke plate has both the holding function of the block parts and must have sufficient rigidity to withstand the side and surface pressure of the block parts. In addition, in order to make the yoke plate groove and the block parts be closely combined, the groove corners of the yoke plate are made to escape processing. If the yoke plate groove corners cannot be made to escape processing, the block parts must be made to escape processing.

(3) The division of block parts should also consider the internal shape, and the reference plane must be clear. In order to prevent deformation during stamping, attention should also be paid to the shape of each block-shaped part.

(4) When the yoke plate is assembled into many block parts, due to the cumulative processing error of each block part, the pitch changes. The solution is to design the middle block parts in an adjustable manner.

(5) The block parts adopt the mold structure of a side-by-side combination. Because the block parts will be subjected to side pressure during punching, the gap between the block parts will be generated or the block party will be inclined. This phenomenon is an important cause of poor stamping dimensions such as defective stamping dimensions and chip clogging. Therefore, adequate measures must be taken.

(6) The method of fixing the block parts in the yoke plate, according to its size and shape, there are the following five types: A. fixed with locking screws, B. fixed with keys, C. fixed with snap-shaped keys, D. with shoulders Fixed, E. Press the above pressing parts (such as the material guide plate) to press firmly.

3. Built-in

The circular or square concave parts are processed in the template, and the block parts are embedded in the template. This template is called a built-in structure. This structure has a small cumulative tolerance of processing, high rigidity, and the accuracy of reproducibility during assembly and assembly good. 

Due to the advantages of easy machining, machining accuracy determined by the working machine, and few final adjustments, the embedded template structure has become the mainstream of precision stamping molds, but its disadvantage is that it requires a high-precision hole processing machine.

When the continuous stamping die is constructed with this template, the empty station is designed to make the template have high rigidity requirements. The precautions for the construction of the embedded template are as follows:

(1) Machining of embedded holes: The processing of embedded holes of template uses vertical milling machine (or jig milling machine), comprehensive processing machine, jig boring machine, jig grinder, wire-cut electric discharge machine, etc. The machining standard for embedded holes is to perform a second or more wire-cutting process to improve the machining accuracy when using a wire-cut electric discharge machine.

(2) Fixing method of inserts: The deciding factors of fixation methods of inserts are not to change the accuracy of its processing, the ease of assembly and decomposition, the possibility of adjustment, etc.   

There are four ways to fix the insert: A. Fix it with screws, B. Fix it with shoulders, C. Fix it with toe blocks, D. Press the upper part tightly with a plate. The fixing method of the insert of the concave template also uses press-fitting.

At this time, the relaxation result due to the thermal expansion of the process should be avoided. When the circular mold sleeve insert is used to process the irregular holes, the rotation prevention method should be designed.

(3) Considerations for assembly and disassembly of inserts: The machining accuracy of inserts and their holes is required to perform assembly operations. In order to obtain even small dimensional errors that can be adjusted at the time of assembly, it is advisable to consider solutions in advance.   

The specific considerations for the processing of inserts are as follows:

A. There is a press-in introduction part.

B. The insert is adjusted by spacers The press-in state and the correct position of the part.

C. The bottom surface of the insert is provided with a hole for pressing-out.

D. It is advisable to use screws of the same size when tightened with screws to facilitate locking and loosening.

E. To prevent assembly direction Mistakes should be designed for foolproof chamfering.

Mold designs 　

1. Unit

The mold alignment unit is also referred to as the alignment guide device of the mold blade. In order to maintain the alignment of the upper mold and the lower mold and shorten the preparation time, according to the requirements of product accuracy and production quantity, the mold alignment unit mainly has the following five types:

(1) Non-guided type: when the die is installed on the punching machine, it directly performs the cooperation of its blade parts, and no guide device is used.

(2) External guide type: This device is the most standard structure. The guide device is installed on the upper mold base and the lower mold base and does not pass through each template. It is generally called the mold base type.

(3) Combined use of an external guide and an internal guide (1). This device is the most commonly used structure for continuous molds, and an internal guide device is installed between the punch fixing plate and the pressure plate.   

The combination of the punch and the die uses a fixing pin and an external guide device. Another function of the inner guide device is to prevent the pressure plate from tilting and protect the small punch.

(4) Combined use of an external guide and internal guide (2): This device is a high-precision high-speed continuous mold use structure, the internal guide device penetrates the punch fixing plate, the pressure plate and the die fixing plate, etc.   

The inner guiding device itself also has the function of the die-cutting piece to align and protect the small punch. The main function of the outer guide device is that the mold is disassembled and can be smoothed when installed on the punching machine.

(5) Inner guide type. This structure does not use an outer guide device. The inner guide device penetrates the punch fixing plate, the pressure plate, and the die fixing plate, etc., and correctly maintains the positional relationship of each plate to protect the shower.

2. Guide pin and guide bushing unit

There are two types of guide modes and accessories for the guide column and guide unit: (A). Outer guide type (mold base type or main guide), (B). Inner guide type (or auxiliary) lead). In addition, to meet the requirements of precision molds, the use of an external guide and internal guide types is highly demanded.

(1) External guide type: generally used for molds that do not require high precision, most of which are sold as a unit with the mold base. The main function is to match the blades when the mold is installed on the punch, and there is almost no stamping. Dynamic accuracy keeps the effect.

(2) Internal guide type: Due to the progress of the mold processing machine, it has been rapidly popularized. The main function is not only to match the blade parts when the mold is installed on the punching machine but also to maintain the dynamic accuracy of the stamping process.

(3) The combined use of an external guide and internal guide: a pair of molds uses both an external guide and an internal guide.

3. Punch and die unit (round)

(1) Punch unit: The round punch unit depends on its shape (shoulder type and straight type), length, and convenience of maintenance. The use of the punch unit should be matched with the pressure plate guide sleeve unit.

(2) Female die unit: The circular female die unit is also called a female die guide sleeve unit, and its form is in one-piece type and separate type. According to the production quantity, service life, and disposability of products or punching chips, the female die unit.   

The combined series are:

(A). Use the template to directly process the shape of the die,

(B). The escape section with a two-stage bevel,

(C). Whether to use the backplate,

(D). The shape of the irregular die must be There is a rotation prevention design.

4. Pressure bolt and spring unit

(1), pressure bolt unit: the types of pressure plate bolts are: (A). External screw type, (B). Sleeve type, (C). Internal screw type. In order to keep the pressure plate parallel to the specified position, the stop method of the pressure bolt (shoulder contact part):   

(A). The cavity receiving surface of the die base,

(B). The top surface of the punch fixing plate,

(C). The top surface of the punch backplate.

(2). Pressing spring unit: movable pressing platen pressing spring unit can be roughly divided into:   

(A). Single-use type,

(B). Combined with pressing bolt

When selecting the compression spring unit, it is best to consider the following points before deciding:

(A), to ensure the free length of the spring and the necessary amount of compression (spring with a large amount of compression should be placed in the cavity of the pressure plate).

(B) It is necessary to adjust the initial spring compression (pre-compression) or load.

(C) Consider the ease of mold assembly or maintenance.

(D), consider the relationship with the length of punch or press bolt.

(E), consider safety (to prevent flying out when the spring breaks).

5. Guide
   

   pin unit (positioning of the feeding direction of the bar)

(1) Guide pin unit: The main function of the guide pin is to obtain the correct feeding pitch during continuous stamping. There are two types of guide units for stamping die: indirect type (the guide pin is used alone) and direct type (the guide pin is installed inside the punch).

(2) The assembly method of the guide pin is the same as that of the punching punch (installed on the punch fixing plate). The spring is used to restrain it to the punch fixing plate.

(3) The guide pin is additionally installed on the pressure plate. Because the amount of the guide pin protruding from the pressure plate is required to reach a certain level and prevent the mold from rising easily to bring the processed material, the rigidity of the pressure plate and It is necessary to pay attention to the guidance form.

(4) The guide pin unit has a direct type, which is installed in the punch and is mainly used for outline punching (cutting processing) or trimming processing of the extension project. Its position is determined by using the product hole and extension part of the inside diameter.

6. Guide unit

(1) When the shape is punched (cutting processing) or continuous stamping processing, in order to guide the width direction of the processed material and obtain the correct feeding pitch, the guide unit is used.

(2) The guide device in the width direction of the strip, the guide methods are:   

(A). Fixed plate guide pin type,

(B). Movable guide pin type,

(C). Plate tunnel guide type ( Single board),

(D). Board guide type (two pieces),

(E). Lifting pin guide type (there are movable type, fixed type, and both.

(3) The guide device for starting and stopping has two forms:   

(1). Slider type,

(2). Movable pin type, etc.

The main function is to position the material at the initial starting position of the mold.

(4) The feeding stop device can correctly determine the feeding pitch. It is mainly used for manual feeding.   

Its forms are:

(A). Fixed stop pin,

(B). Movable stop pin,

(C ). Side cutting stop mode,

(D). Hook stop mechanism,

(E). Automatic stop mechanism.

(5). Side-pushing material guide mechanism, the material is pressed to one side during the stamping process, which can prevent the material from being snaked due to the difference between the width of the material strip and the width of the material guide.

(6). Positioning and guiding mechanism of blank material, its forms are:   

(A). Fixed pin guide type (using the shape of the blank),

(B). Fixed pin guide type (using the hole of the blank),

(C). Material guide plate (for large parts),

(D). Material guide plate (integrated),

(E). Material guide plate (split shape).

7. Lifting and topping unit

(1). Lifting pin unit: its main function is to lift the bar to the die during continuous stamping (the position height is called the feeding height, and to achieve the purpose of smooth feeding, its form is: 

 (A). The pin type (round, for pure lifting) is the most common lifting pin unit.

(B). The lifting pin type (round, with holes for guide pins), the lifting pins are equipped with guide pins Using holes can prevent the material from undergoing the deformation of the guide pin and make the guide pin actually work.

(C). The material lifting and material guide pins have both the material guiding function. The material of the continuous mold is most often used in this form. 

(D). Lifting pin type (square) If required, air blow holes are provided. (E). Lifting and guide pin type (square).

(2) Feeding unit: during automatic stamping, it is necessary to prevent punching products or chips from jumping on the surface of the die to avoid damage to the die and the occurrence of bad stamping parts.

(3). Ejection unit: The main function of the ejection unit is to eject the product or waste material from the concave mold each time it is punched.   

There are two installation sites for the ejection unit: (A), the reverse configuration mold is installed on the upper mold part, and (B). The co-configuration mold is installed on the lower mold part.

8. Fixed pin unit

The shape and size of the fixed pin unit are designed according to the requirements of standard specifications.   

The precautions during use are:

(A). The fixed pinhole should be a through-hole. If it is not possible, consider a design method that is easy to remove with screws.

(B). The length of the fixing pin is the best, not longer than necessary.

(C). The fixed pinhole should have the necessary escape part.

(D). When placed on the upper mold part, a mechanism to prevent falling should be designed to prevent it from falling.

(E). When one side press fits and one side slide fits, the fixing pinhole on the sliding side is slightly larger than the fixing pin.

(F). The number of fixed pins is based on the principle of two, and try to choose the same size.

9. Pressure
   

   plate unit

The particularly important point of the pressure plate unit is that the pressure surface and the die surface have the correct parallelism and the buffer pressure requirements are balanced.

10. Misfeed detection unit

When stamping with a continuous die, the die must be designed with an error detection unit to detect whether the change in feed pitch exceeds its reference and stop the operation of the punch. The error detection unit is installed inside the mold.   

According to the detection method, there are the following two installation forms:

(A). The detection pin is installed in the upper mold. When it deviates from the hole of the material strip, it will be connected with the material strip. Detected by contact.

(B). The detection pin is installed in the lower mold. It is detected when a part of the material strip contacts the detection pin.

11. Scrap cutting unit

During the continuous stamping process, the strip (scrap) will leave the mold one after another. There are two processing methods: (A). Take it up by the coiler, (B). Use the mold cutting device to refine it.   

There are two ways of the latter:   (A). Use a special waste cutter (installed outside the stamping machine), (B). A cutting unit installed in the final project of the continuous mold.

12. Height stop block unit

The main function of the height stop block unit is to correctly determine the position of the bottom dead point of the upper die, which has the following two forms:   

(A). The method of frequent contact during stamping,

(B). Contact only during assembly, stamping Way of not touching.

In addition, in order to prevent contact between the upper mold and the lower mold when the mold is transported and stored, it is best to place a spacer between the upper mold and the lower mold.

When the accuracy requirement is not necessary, the use standard can adopt a screw adjustment type.

Main mold components

1. Standard parts and specifications

The selection method of standard specifications for injection molds is best to consider the following items:   

(A). When the content of the specifications used is not limited, it is best to use the highest level.

(B). In principle, standard numbers are used.

(C). When the standard parts of the injection mold do not have this size, the nearest one will be used for processing.

2. Punch

   design

The punch can be roughly divided into three parts according to its function:       

(A). The cutting edge of the processed material (cutting edge, its shape is irregular, square, round, etc.).

(B). The contact part of the fixed plate with the punch (fixed part or shank, the cross-sectional shape of which is irregular, square, round, etc.).

(C). The connecting part (middle part) of the blade and the shank.

The design criteria of each part of the punch are briefly described from (A). Length of cutting edge, (B). Grinding direction of cutting edge, (C). Fixing method of punch and shape of shank.

3. Design of the punch fixing plate

The thickness of the punch fixing plate is related to the size of the die and the load, generally, it is 30-40% of the punch length, and the length of the punch guide should be higher than 1.5 times the punch diameter

4. Design of guide pin (punch)

The diameter of the guide part of the guide pin (punch) and the gap between the material guide hole, the size, and the amount of the protruding pressure plate is designed according to the thickness of the material.   

The shape of the leading end of the guide pin is roughly divided into two types: A. shell Shape, B. conical (push-pull shape).

(1). The shell shape is the most common form, and there are also standard parts on the market.

(2). The cone has a certain angle, which is very suitable for high-speed stamping of small parts. The determinants of the pushing angle are the stamping stroke, the material of the workpiece, the size of the guide hole, and the processing speed.   

When the pushing angle is large, it is easier to correct the position of the processed material, but the length of the pushing part will become longer. The connection between the pushing part and the cylindrical part should be smooth.

5. The design of the die

(1). Design of punching dies

The main considerations for the shape design of the die-cutting die are: A. die life and shape of escape angle, B. shear angle of the die, C. division of the die.

(A). Die life and shape of escape angle: This design is a very important matter. If the design is incorrect, it will cause damage to the punch, blockage or floating of the punching chips, and the occurrence of undesirable stamping processing phenomena.

(B). The shear angle of the concave die: to reduce its punching force when the shape is punched, the die can be designed with a shear angle. When the shear angle is large, the reduction of punching force is also large, but it is easy to cause product curvature and deformation.

(C). Splitting of the concave mold: the concave mold must be subjected to finishing processing such as forming and grinding. Because it is concave, the grinding tool is not easy to enter, so it must be divided.

(2). Design of curved concave die

The design of the concave die for bending is to prevent the occurrence of spring back and excessive bending. The shape of the U-shaped concave die is a combination of double R and a straight part (with a slope of 30 degrees). It is best to approximate the R shape. The shape of the R part should be polished after being shaped and ground or NC electric discharge machined.

(3). Design of extension die

The corner shape and escape shape of the extension die are very important design issues. The shape and characteristics of the corner and escape angle are as follows: when the R-value of the extension die is large, it is easier to extend the process, but it also produces the surface of the extension product.   

Wrinkle phenomenon occurs, and the thickness of the sidewall of the extension product is greater than the thickness of the board. For thick plate parts and difficult ejection, the R-value of the die should be small, about 1-2 times the thickness of the plate.

Generally, most of the extension parts of the cylinder and square cylinder extension dies are made into straight sections to prevent For the purpose of burning occurrence, the destruction of the lubricating oil film and the reduction of ejection force, the escape section (stage-shaped or push-out) design should be provided below the straight section.

Especially in the case of shrinking and shrinking processing, it is necessary to have a few straight sections as possible.

6. Countermeasure of side pressure of the punch

It is the best ideal state to bear the equal load on the left and right of the punch during the stamping process (that is, the side pressure is zero). When the punch is subjected to the lateral pressure, the upper die and the lower die will be laterally offset, causing a part of the die gap It becomes larger or smaller (the gap is not uniform) and the punching process with good accuracy cannot be obtained. 

Regarding the countermeasures for the side pressure of the punch, there are the following methods: 

(A). Change the processing direction, 

(B). Products with single-side processing (punching, bending, stretching, etc.) should adopt a two-row arrangement, 

(C). The head or the die is provided with a side pressure stopper, and the side of the cutting edge is provided with a guide part (especially for cutting and breaking processing).

7. Design of backpressure plate

During the stamping process, the main parts (punch, pressure plate, die) will bear the surface pressure afterward. When the pressure is higher than the surface pressure, the backpressure plate (especially the back of the punch and die sleeve) should be used. There are two ways to use it: partial use and full use.

Mold design software

The modern industry is developing rapidly, basically, all use computers to design and process, and its accuracy can be guaranteed at 0.002~0.01. There is a boundless vast world for mold design work. If you can use a computer for auxiliary design, your opponent, behind you, is behind you. Common mold design software is AUTOCAD Pro/E UG SW CImatron, missing, and so on.

Impact of mold on life

Design is the key step in mold production, the initial link of production, and controls the entire process of mold production. Therefore, the design also has a great impact on the service life of the mold. The design mainly affects the service life of the stamping mold from the following two aspects.

(1) The precision of the guide mechanism of the mold. Accurate and reliable guidance is very effective for reducing the wear of the working parts of the mold and avoiding the bite damage of the convex and concave molds, especially the blanking and small gap punching dies, compound dies and multi-station progressive dies.   

In order to improve the life of the mold, the design must be based on the requirements of the nature of the process and the accuracy of the parts, the correct selection of the guide form, and the accuracy of the guide mechanism.

(2) The geometric parameters of the cutting edge of the mold (convex and concave). The shape of the convex and concave dies, the matching gap, and the radius of the fillet not only have a great influence on the forming of the stamping parts but also have a great influence on the wear and life of the die.  

For example, the fit-gap of the mold directly affects the quality of the blanking parts and the life of the mold. For higher precision requirements, the smaller gap value should be selected in the design; otherwise, the gap can be appropriately increased to increase the life of the mold.

Common mold software

Plastic injection mold

PTC’s EMX, Siemens’ NXMold Wizard, CimatronE, Delcam Moldmaker, Missler’s Topsolid Mold, Think3’s Mold Design, Manusoft’s IMOLD, R&B’s MoldWorks, etc.

Hardware stamping mold

PTC’s PDX, Siemens’ NXProgressive Die Design, Logopress’s Logopress3, 3D QuickTools Limited’s 3DQuickPress, R&B Mold & Die Design’s MoldWorks, Missler’s Topsolid Progress, etc.

Mold manufacturing

The requirements for mold design and production are: accurate size and smooth surface; reasonable structure, high production efficiency, and easy automation; easy manufacturing, high life, and low cost; design meets the needs of the process and is economical and reasonable.

Factors such as rigidity, directionality, unloading mechanism, positioning method, gap size, etc. must be considered in the design of mold structure and parameter selection. The wearing parts on the mold should be easy to replace.

For plastic molds and die-casting molds, it is also necessary to consider a reasonable pouring system, the flow state of molten plastic or metal, and the position and direction of entering the cavity. 

In order to improve productivity and reduce the pouring loss of the runner, a multi-cavity mold can be used, and multiple same or different products can be completed in one mold at the same time. High-efficiency, high-precision, long-life molds should be used in mass production.

The stamping die should adopt a multi-station progressive die, and a progressive die with carbide inserts can be used to increase the service life. 

In small batch production and new product trial production, simple molds with simple structure, fast manufacturing, and low cost should be used, such as combination punches, sheet punches, polyurethane rubber molds, low melting point alloy molds, zinc alloy molds, superplastic alloy molds, etc. 

The mold has begun to use computer-aided design (CAD), that is, through a computer-centric system to optimize the design of the mold. This is the development direction of mold design.

According to the structural characteristics, die manufacturing is divided into flat punching die and cavity die with space. The punching die uses the size of the punch die and the die to precisely match, and some even have no clearance. 

Other forging dies such as cold extrusion dies, die casting dies, powder metallurgy dies, plastic dies, rubber dies, etc. are all cavity dies and are used to form three-dimensional workpieces. The cavity mold has size requirements in the three directions of length, width, and height, and the shape is complicated, making it difficult to manufacture. 

Mold production is generally a single piece, small batch production, manufacturing requirements are strict and precise, and most of them use precision processing equipment and measuring devices.

The plane punching die can be initially formed by electrical discharge machining and then shaped grinding, coordinate grinding, and other methods to further improve accuracy. 

Forming grinding can use an optical projection curve grinder, or surface grinder with miniaturization and repairing grinding wheel mechanism, or it can be grinded on a special surface grinding machine with a special forming grinding tool. 

The coordinate grinder can be used for precise positioning of the mold to ensure precise aperture and hole distance. It can also be used to grind any curved and convex punches and concave dies with a computer numerical control (CNC) continuous track coordinate grinder. 

The cavity molds are mostly processed by copy milling machines, electric discharge machining, and electrolytic machining. The combined application of copy milling and numerical control and the addition of a three-way translation head device in EDM can improve the processing quality of the cavity. 

The addition of aerated electrolysis in electrolytic processing can improve production efficiency.

Selection of mold

Mold material selection is a very important part of the entire mold making process.

The selection of materials for the mold needs to meet three principles. The mold meets the work requirements of wear resistance and toughness. The mold meets the process requirements. At the same time, the mold should meet economic applicability.

Requirements for mold material selection

1. Wear resistance

When the blank is plastically deformed in the cavity of the mold, it flows and slides along the surface of the cavity, which causes intense friction between the surface of the cavity and the blank, resulting in the failure of the mold due to wear.   

Therefore, the wear resistance of the material is one of the most basic and important properties of the mold.

Hardness is the main factor affecting wear resistance. In general, the higher the hardness of the mold parts, the smaller the amount of wear and the better the wear resistance. In addition, the wear resistance is also related to the type, number, form, size, and distribution of carbides in the material.

2. Strong toughness

Most of the working conditions of the mold are very bad, and some often bear a large impact load, which leads to brittle fracture. In order to prevent the mold parts from being brittlely broken during work, the mold should have high strength and toughness.

The toughness of the mold mainly depends on the carbon content, grain size, and microstructure of the material.

3. Fatigue fracture performance

In the mold working process, under the long-term effect of cyclic stress, it often leads to fatigue fracture. Its forms include low energy multiple impact fatigue fracture, tensile fatigue fracture contact fatigue fracture, and bending fatigue fracture.

The fatigue fracture performance of the mold mainly depends on its strength, toughness, hardness, and the content of inclusions in the material.

4. High-temperature performance

When the working temperature of the mold is higher, the hardness and strength will decrease, resulting in early wear or plastic deformation of the mold and failure. Therefore, the mold material should have high stability against tempering to ensure that the mold has high hardness and strength at the working temperature.

5. Cold and heat fatigue resistance

Some molds are in the state of repeated heating and cooling during the work process, which causes the surface of the cavity to be pulled and the stress of the pressure changes, causing surface cracking and flaking, increasing friction, hindering plastic deformation, and reducing dimensional accuracy, resulting in Mold failure.   

Hot and cold fatigue is one of the main forms of hot work die failure. This type of mold should have high resistance to cold and hot fatigue.

6. Corrosion resistance

Some molds, such as plastic molds, when working, due to the presence of chlorine, fluorine, and other elements in the plastic, after heating, the strong corrosive gases such as HCI and HF are resolved, eroding the surface of the mold cavity, increasing its surface roughness, and exacerbating wear failure.

Process performance of the mold

The manufacture of the mold generally goes through several processes such as forging, cutting, and heat treatment. In order to ensure the manufacturing quality of the mold and reduce production costs, the material should have good forge ability, cutting workability, hardenability, and grind ability; it should also have small oxidation, decarburization sensitivity, and quenching Deformation and cracking tendency.

1. Malleability

It has low hot forging deformation resistance, good plasticity, wide forging temperature range, low forging cracking, and a low tendency to precipitate network carbide.

2. Annealing processability

The spheroidizing annealing temperature range is wide, the annealing hardness is low and the fluctuation range is small, and the spheroidizing rate is high.

3. Machinability

A large amount of cutting, low tool loss, and low surface roughness.

4. Sensitivity to oxidation and decarburization

The anti-oxidation performance is good when heated at a high temperature, the decarburization speed is slow, it is not sensitive to the heating medium, and the tendency to produce pitting is small.

5. Hardenability

After quenching, it has a uniform and high surface hardness.

6. Hardenability

After quenching, a deeper hardened layer can be obtained, which can be hardened by using a mild quenching medium.

7. The cracking tendency during quenching deformation

Conventional quenching has small volume changes, slight warpage and distortion, and a low tendency to abnormal deformation. The cracking sensitivity of conventional quenching is low, and it is not sensitive to the quenching temperature and the shape of the workpiece.

8. Grindability

The relative wear of the grinding wheel is small, and the maximum amount of grinding without burns is large. It is not sensitive to the quality of the grinding wheel and the cooling conditions, and it is not easy to cause scratches and grinding cracks.

The performance of the mold

1. Small density: The low density of plastics is of great significance to reduce the weight of machinery and equipment and save energy, especially for vehicles, ships, aircraft, and spacecraft.
2. High specific strength and specific rigidity: the absolute strength of the plastic is not as high as metal, but the density of plastic is small, so the specific strength (σb/ρ) and specific rigidity (E/ρ) are quite high. In particular, reinforced plastics made of various high-strength fibrous, flake and powder metal or non-metal as fillers have higher specific strength and specific stiffness than metals.
3. Good chemical stability: Most plastics have good resistance to acids, alkalis, salts, water, and gases. Under normal conditions, they do not chemically react with these substances.
4. Good electrical insulation, heat insulation, and sound insulation performance.
5. Good wear resistance and self-lubrication: plastic has low friction coefficient, good wear resistance, and good self-lubricity, plus high specific strength, low transmission noise, it can be rubbed in the liquid medium, semi-dry or even dry Work effectively under conditions. It can be made into machine parts such as bearings, gears, cams, and pulleys, which are very suitable for occasions with low speed and low load.
6. Strong bonding ability.
7. Good forming and coloring performance.

Economic requirements

In the selection of materials for molds, the principle of the economy must be considered to reduce manufacturing costs as much as possible.

Therefore, under the premise of satisfying the use performance, first, select the lower price, carbon steel can be used without alloy steel, and domestic materials can be used without imported materials.

In addition, the production and supply of the market should also be considered when selecting materials. The steel types selected should be as few and concentrated as possible and easy to purchase.

Mold repair

According to incomplete statistics, the annual die consumption value in the machining industry is five times the total value of various machine tools.

It is conceivable that the die market in the machinery, metallurgy, light industry, electronics, and other industries is so huge.

Another example: In the metallurgical industry, the annual consumption of hot-rolling rolls alone is more than 300,000 tons, and the value of hot-rolling rolls accounts for more than 5% of steel production costs.

The large consumption of molds not only directly increases production costs but also results in frequent economic shutdowns due to frequent production shutdowns due to frequent mold replacements.

In fact, the failure of the mold is actually scrapped due to the local material wear on the surface layer, and the processing cycle of the mold is very long and the processing cost is extremely high (especially the manufacturing and processing costs of precision complex molds or large molds are as high as hundreds of thousands or even millions yuan).

Therefore, it is undoubtedly a method with important economic significance to strengthen the surface of the specific parts where the mold really bears the wear, so as to greatly extend and improve the service life of the tool and mold.

In addition, most of the molds are invalid and scrapped only after a thin layer of material is worn out.

Therefore, only the local areas of the surface wear of the mold and key metal parts need to be repaired, and the mold surface is actually subjected to wear during the repair process.

The surface is coated with a metal layer with high hardness and high wear resistance, which can turn waste into treasure.

Not only will the mold be repaired, but the service life of the repaired mold will also be greatly improved compared with the original mold, and the economic benefits are huge (such as It takes only a few days to repair a large shaft of a power plant motor including various preparation times, but it can create economic benefits of millions of yuan).

Mold repair machine is high-tech equipment for repairing mold surface wear and processing defects. The principle of the mold repair machine is to use the principle of high-frequency electric discharge to carry out heatless surfacing welding on the workpiece to repair the surface defects and wear of the metal mold. 

The main feature is that the heat affected area is small, and the mold will not be deformed or annealed after repair. 

There is no stress concentration and no cracks, which ensures the integrity of the mold; it can also use its strengthening function to perform surface strengthening treatment on the molded workpiece to achieve the wear resistance, heat resistance, and corrosion resistance of the mold.

The mold repair machine strengthens the mold with long life and good economic benefit. It can apply various types of iron-based alloys (carbon steel, alloy steel, cast iron), nickel-based alloys, and other metal material molds and workpiece surface strengthening and repair and greatly improve the service life.

Applications: Machinery, automotive, light industry, home appliances, petroleum, chemical, power, and other industrial equipment manufacturing departments and user departments, key wear parts for aero engines, hot extrusion dies, warm extrusion dies, hot forging dies, steel rolling Guides, rollers, automobile engine camshafts, and other parts and molds

Mold maintenance

1: The mold must be sharpened after a long period of use.

After grinding, the blade surface must be demagnetized, and it must not be magnetic, otherwise, it will be prone to blockage. The mold-using enterprise shall make detailed records, statistics on its use, care (lubrication, cleaning, rust prevention) and damage, according to which parts and components have been damaged and the degree of wear and tear can be found to provide information for finding and solving problems.

And the molding process parameters of the mold and the materials used in the product to shorten the test run time of the mold and improve production efficiency.

Under the normal operation of the injection molding machine and the mold, the various performances of the mold should be tested, and the size of the final molded plastic part should be measured. Through this information, the existing state of the mold can be determined, and the cavity, core, cooling system.

And According to the information provided by the plastic parts, the damage state of the parting surface, etc. can be judged to determine the damage state of the mold and the maintenance measures.

2: Springs and other elastic parts are most susceptible to damage during use, and usually break and deform. The method adopted is to replace it. During the replacement process, you must pay attention to the specifications and models of the spring.   

The specifications and models of the spring are confirmed by the three items of color, outer diameter, and length. Only when the three items are the same can you replace them. The quality of imported springs is better.

3: During the use of the die, the punch is prone to break, bend and nibble, and the punch sleeve is generally nibble. The damage of the punch and the sleeve is generally replaced with parts of the same specification. The parameters of the punch mainly include working part size, installation part size, length size, and so on.

4: Fasten the parts, and check whether the fastener parts are loose or damaged. The method adopted is to find parts with the same specifications for replacement.

5: Pressing parts such as pressing plate, Youli glue, etc., unloading parts such as stripping plate, pneumatic ejector, etc.

During maintenance, check the relationship of parts and whether there is damage, repair the damaged parts, check the pneumatic ejector for leaks, and take measures for specific situations.

Replace if the trachea is damaged. Several important parts of the mold should be tracked and inspected: the function of ejection and guide parts is to ensure the opening and closing movement of the mold and ejection of the plastic parts.

If any part of them is stuck due to damage, it will lead to the stop of production, so it should be kept frequently. Lubricate the guide bush and guide pin of the mold (select the most suitable lubricant), and regularly check the guide bush and guide pin for deformation and surface damage.

Once found, they should be replaced in time; after completing a production cycle, the mold work surface should be, Sports and guide parts are coated with professional anti-rust oil, especially the protection of the elastic strength of the bearing parts of the gears, rack molds, and spring molds to ensure that they are always in the best working state; as the production time continues,

The cooling channel is prone to deposit scale, rust, sludge, and algae, etc., Making the cross-section of the cooling flow channel narrows and the cooling channel narrow, greatly reducing the heat exchange rate between the coolant and the mold, increasing the production cost of the enterprise.

So the cleaning of the flow channel should be paid attention to; for the hot runner mold, the maintenance of the heating and control system is helpful to prevent the occurrence of production failures, so it is particularly important.

Causes of mold loss

1) The material of the main working parts of the mold is not properly selected. The material has poor performance and is not wear-resistant; the die steel has not been refined and has a large number of smelting defects; the convex and concave die, the forging blank forging process is not perfect, and there are hidden dangers of heat treatment.

2) The design of the die structure is unreasonable. The slender punch is not designed with a reinforcement device, the discharge port is not smooth, and the discharge force is too high.

3) The mold making process is imperfect, mainly manifested in the inherently poor quality of the male and female forging billets, and the heat treatment technology and process are problematic, causing the male and female molds to be hardly penetrated, and have soft spots and uneven hardness.   

Sometimes micro-cracks, or even cracks, grinding, and polishing are not in place, and the surface roughness value is too large.

4) No lubrication or lubrication but the effect is not good,

Mold industry status

Mold development

According to the Basic Situation of National Mold Professional Factory compiled by the Management Committee of my country Mould Industry Association, my country’s mold is growing at an average rate of more than 15%, which is more than double the average increase in domestic GDP.

Among them, casting molds account for about 5% of the total output value of various molds, and the annual growth rate is as high as 25%, and the development is very active.

The development of my country’s mold industry has given strong support to the manufacturing industry.

At the same time, the development of the manufacturing industry has also promoted the development of the mold industry. my country has also become a major mold production country.

The number of domestic mold manufacturers has increased to more than 20,000, and the number of employees is about 1 million. The annual output value of molds has reached 55 billion yuan.

However, my country’s mold machine tool industry is still big but not strong. Although China’s mold industry is currently hailed as a global manufacturing country due to its huge annual import and export volume, due to the constraints of technical personnel and other factors, it is relatively concentrated in the low-end field. Therefore, the high-end market is economical for domestic mold companies. The temptation is undoubtedly huge.

An industry association is an economic association established by related companies for their own development. Under market economy conditions, as an important intermediary organization, industry associations have the function of coordinating the interests of market subjects and improving the efficiency of market allocation.

Therefore, promoting the construction of industry associations has become a subject that cannot be ignored. If the mold industry is to achieve great development, it is essential to promote the construction of the mold industry association.

Some high-level molds have accounted for about 40%, and these molds are characterized by complexity, precision, large size, and long life.

For example, some molds can reach a single set weight of 125t? Some precision multi-station progressive die life reaches 300 million strokes and an accuracy of 0.001mm.

With the increasing precision requirements of the mold parts industry and the progress of science and technology, some of the machining accuracies of the parts will be within lμm.

The company’s innovation and R&D capabilities have been improved, and new technologies and processes have been widely promoted. For example, the self-processing technology of the mold and the flexibility and integration technology of the mold?

The structural design system of the mold, the development of the large-scale progressive mold, the advanced mold manufacturing technology, and the three-dimensional design technology?

The stamping process design system, reverse engineering, and the digital manufacturing system of the body mold, etc. These are inseparable from the vigorous development and promotion of digitalization and information technology.

Problems with the mold

my country’s mold industry continues to develop, but at the same time, there are many problems that need to be solved. China’s mold industry has been busy expanding, ignoring market surveys, and understanding customer need, resulting in high-end molds becoming the shortcomings of China’s mold industry.

Most of the high-end molds required in the Chinese market rely on imports, but a large number of domestic mold products are out of stock There is no door and a lot of squeezing, causing a serious situation of supply and demand misalignment.

Types of mold processing

1. Roughing

The roughing strategy needs to be determined according to the type of blank and the molding profile. If the blank is a forged or steel part, it is best to use the area removal model for roughing , then remove most of the blank to obtain a uniform blank margin, which is convenient for subsequent processing.

2. Semi-finishing

The main purpose of semi-finishing is to ensure that the margin is uniform during finishing. The most common method is to first calculate the boundary contour of the residual material (refer to the 3D contour of the unprocessed area of the tool), and then select a smaller tool to process these 3D contour areas Without reprocessing the entire model.

3. Local finishing

Local finishing generally refers to angle-clearing processing. Clearing angle processing should use multiple processing or series of tools from large to small processing methods.

4. Finishing

In the finishing process, unless the height of the mold surface changes greatly, it is best to choose parallel finishing.

Prospect of the mold industry

my country is gradually moving from a major mold production country to a powerful mold manufacturing country. As far as the domestic market is concerned, the production and demand of the mold industry are booming, the investment enthusiasm of enterprises is rising, and larger technological transformation projects and new construction projects are constantly emerging.

In addition, the construction of industrial clusters is continuously accelerating. With the support of government preferential policies, there are already more than 100 mold cities (or mold parks, agglomerated production bases, etc.) with a considerable scale in the country.

Others are under construction, planning, or planning construction. more than ten. Some areas are still developing mold complexes and virtual manufacturing, which also has some advantages similar to cluster production.

For foreign markets, my country’s mold industry also performed well. The mold industry actively explores emerging markets while steadily advancing in traditional markets, and even marginal markets that have been neglected in the past have also been developed.

Driven by the development of LED lighting and display, rail transit, medical equipment, new energy, aerospace, automobile lightweight, rail transit and other fields, the level of my country’s mold industry has been significantly improved. These factors have made the mold market development remarkable.