How to reduce mold defects by Huaye Precision Moulding

How to reduce defects in Molding Process

In order to improve the mold performance, many manufacturers will properly process their molds. Mold processing refers to the processing of forming and blanking tools. In addition, it also includes shearing molds and die-cutting molds. However, in many cases, the molds are processed. It will also reflect processing defects, resulting in a decline in mold performance. How to build mold processing defects? The following seven measures can reduce mold processing defects.


  1. Reasonable select and dress thegrinding wheels

The white corundum grinding wheel is hard and brittle, and easy to produce new cutting edges. Therefore, the cutting force and grinding heat is small, and the medium grain size is used, such as 46 to 60 mesh. The hardness of the grinding wheel is medium soft and soft (ZR1, ZR2 and R1, R2), that is, coarse-grained, low-hardness grinding wheels, and good self-excitation can reduce cutting heat.

It is very important to choose an appropriate grinding wheel for fine grinding. For the high vanadium and high molybdenum condition of the mold steel, GD single crystal corundum grinding wheel is more suitable. When processing hard alloys and materials with high quenching hardness, organic binder diamond is preferred. The grinding wheel, organic binder grinding wheel has good self-grind ability, and the roughness of the ground work piece can reach Ra0.2μm. In recent years, with the application of new materials, CBN (cubic boron nit ride) grinding wheels have shown very good processing effects. Finishing on CNC forming grinder, coordinate grinder, CNC internal and external cylindrical grinder, the effect is better than other types of grinding wheels.

In the grinding process, attention should be paid to dressing the grinding wheel in time to keep the grinding wheel sharp. When the grinding wheel is passivated, it will slip and squeeze on the surface of the work piece, causing burns on the surface of the work piece and reducing its strength.

  1. Use cooling lubricants rationally

Play the three roles of cooling, washing, and lubrication to keep cooling and lubrication clean, so as to control the grinding heat within the allowable range to prevent thermal deformation of the work piece. Improve the cooling conditions during grinding, such as using oil-immersed grinding wheels or internal cooling grinding wheels. The cutting fluid is introduced into the center of the grinding wheel, and the cutting fluid can directly enter the grinding area to exert effective cooling and prevent burns on the surface of the work piece.

  1. Reduce the quenching stress after heat treatment to a minimum

Because of the quenching stress and the net-like carbonized structure under the action of the grinding force, the phase change of the structure can easily cause cracks in the work piece. For high-precision molds, in order to eliminate the residual stress of grinding, low temperature aging treatment should be carried out after grinding to improve toughness.

  1. Eliminate grinding stress

You can also immerse the mold in a salt bath at 260-315°C for 1.5 minutes, and then cool it in oil at 30°C, so that the hardness can be reduced by 1HRC and the residual stress can be reduced by 40%-65%.

  1. Constant temperature grinding

For precision grinding of precision molds with dimensional tolerances within 0.01 mm, attention should be paid to the influence of ambient temperature and constant temperature grinding is required. From the calculation, it can be seen that for a 300mm long steel, when the temperature difference is 3℃, the material will have a change of about 10.8μm (10.8=1.2×3×3, the deformation per 100mm is 1.2μm/℃), and each finishing process needs to be fully considered The influence of this factor.

  1. Use electrolytic grinding

Improve mold manufacturing accuracy and surface quality. During electrolytic grinding, the grinding wheel scrapes off the oxide film: instead of grinding the metal, the grinding force is small, the grinding heat is also small, and there will be no grinding burrs, cracks, burns, etc. The general surface roughness can be better than Ra0 .16μm; In addition, the wear of the grinding wheel is small, such as grinding cemented carbide, the wear of silicon carbide grinding wheel is about 400% to 600% of the weight of the cemented carbide that is ground. When electrolytic grinding is used, the wear of the grinding wheel only 50% to 100% of the removal of cemented carbide.

  1. Reasonably choose the amount of grinding

Use the fine grinding method with small radial feed or even fine grinding. If the radial feed rate and the grinding wheel speed are appropriately reduced, and the axial feed rate is increased, the contact area of the grinding wheel and the work piece is reduced, and the heat dissipation conditions are improved, thereby effectively controlling the increase in surface temperature.



Molding Clamping Force introduction

What is Molding Clamping Force

Clamping force refers to the force applied to a mold by the clamping unit of an injection molding machine. In order to keep the mold closed, this force must oppose the separating force, caused by the injection of molten plastic into the mold.

Molding Clamping Force introduction

The factors that affect the specific clamping force of the mold are the projected area of the product and the runner on the parting surface, the number and position of the gate, the size of the gate, the viscosity of the plastic, the flow length ratio, the injection speed and other molding conditions.


Here are two methods to calculate the clamping force:

1.Assumed a product is made in PC, 103mm long and 63mm wide, 4 cavities in one mold, the length of the flowing end of the gate is 60mm, and the thickness is 0.8mm

Step 1: Calculate the projected area: 103*63*4=25965mm2=259.65cm2 (projected area)

Step 2: Calculate the flow length ratio: (flow length) 60 / (thickness) 0.8=75

Step 3: Look up the mold pressure table: 75=250

Step 4: 250 (in-mold pressure) *2.0 (check table for material viscosity coefficient) = 500 bar (in-mold pressure of PC)

Step 5: 500bar*1.02=510 kgf/cm2 (1bar=1.02kgf/cm2)

Step 6: The clamping force is 510*259.65=132421kgf=132.4Ton

The above method is more accurate but requires some auxiliary tables to find it. There is another simpler way to quickly calculate the approximate clamping force and combine experience to get it, that is, the projected area is multiplied by the coefficient of the material. The size can be determined empirically according to the thickness and structure of the product.


2. Similarly in the above example, the coefficient of PC material is 0.465-0.775Ton/cm2. Since the flow length value is not large, 0.55 can be taken below the middle, then the clamping force is 0.55*259.65=142Ton, which is actually the simplified version of the above

What we commonly use now is ABS material. The in-mold pressure of ABS material is generally 0.3-0.48Ton/cm2, which is mainly related to flow length, thickness and structure.

If it is not thin-walled molding, the internal pressure of the general product ABS mold can be 0.3Ton/cm2. The theory requires machine = theoretical clamping force * safety factor (the clamping force required for general products is between 30-85% of the machine, so the safety factor is 100/85=1.17)


Hope you have a clear understanding about the clamping force, and as an professional injection mold manufacturer, we will share more information about molding process.

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Material Introduction-Nylon(Polyamide)-Xiamen Huaye Precision Moulding

Material Introduction-Nylon(Polyamide)

Polyamide resin, PA for short, commonly known as nylon, is a macromolecular main chain repeating unit containing amide groups in the polymer of the general name. It is the the largest output, the most varieties, the most versatile species for the five engineering plastics . The main species are nylon 6 and nylon 66, the absolute dominance of nylon 6 for the poly-caprolactam, and nylon 66 for the poly-adipic acid hexanediamine, nylon 66 is 12% harder than nylon 6; followed by nylon 11, nylon 12, nylon 610, nylon 612, nylon 1010, nylon 46, nylon 7, nylon 9, nylon 13, new varieties of nylon 6I, nylon 9T and special nylon MXD6 (barrier resin), etc., a wide variety of modified nylon varieties, such as reinforced nylon, monomer cast nylon (MC nylon), reaction injection molding (RIM) nylon, aromatic nylon, transparent nylon, high impact (super tough) nylon, plating nylon, conductive nylon, flame retardant nylon, nylon and other polymer blends and alloys, etc., to meet different special requirements, widely used as a Metal, wood and other traditional material substitutes.

As a large amount of engineering plastics, nylon is widely used in machinery, automobiles, electrical appliances, textile equipment, chemical equipment, aviation, metallurgy and other fields. It has become an indispensable structural material in various industries and its main features are as follows.

1.Excellent mechanical properties. Nylon has high mechanical strength and good toughness.

2. Self-moistening, good friction resistance. Nylon has good self-wetting, small coefficient of friction, thus, as a transmission components and its long service life.

3. excellent heat resistance. Such as nylon 46 and other highly crystalline nylon heat deformation temperature is very high, can be used at 150 ℃ for a long period of time … … PA66 after glass fiber reinforced. PA66 after glass fiber reinforced, its heat distortion temperature of 250 ℃ or more.

4. Excellent electrical insulation properties. The volume resistance of nylon is very high, high breakdown voltage resistance, is excellent electrical, electrical insulation materials.

5. Excellent weather resistance.

6. Water absorption. Nylon water absorption, saturated water can reach more than 3%. To a certain extent, it affects the dimensional stability of the workpiece.


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Cautions in Mold Tryout

Mold tryout is to test the mold defects through different process conditions and improve it through modifying. For those that cannot be modified for the time being, it is necessary to find out the most reasonable process parameters to guide the subsequent injection molding production.


Pay attention to the following content during the mold tryout:

First: Check the flow balance

Observe the product’s glue feeding by gradually increasing the amount of glue. For a single cavity, flow balance means that the flow front of the melt reaches the end of the cavity. For multiple cavities, flow balance means that the flow front of the melt reaches the end of each cavity . Different product weights or inconsistent shrinkage in multi-cavity molds in injection molding production are generally caused by imbalanced flow.

Second: The inspection of flashing

Check if the parting surface, row position, insert joint line, ejector pin hole and other parts when the product is not shrunk. In this case, more injection molding needs to be adjusted Process, local glue reduction, increase gate or change gate position to improve.

Third: Determination of mold exhaust position

Use a faster injection speed to find the position where the product has scorched, trapped air, water traps, etc., and then set up an exhaust slot at the corresponding position.

Fourth: Determine the key position of the screw of the injection molding machine

By changing the stroke of the screw of the injection molding machine, determine the key position of the screw during product injection. At a minimum, the key positions should include:

  1. The flow channel has just been filled;
  2. From the first gate filling to the last gate filling position (unbalanced gate design);
  3. The location when the water line, burnt, trapped air and other undesirable phenomena that affect the product appear;
  4. The position when the product is 99% filled (that is, the speed and pressure conversion position).

These key positions are the key to adjusting the injection process in the future.

Fifth: Inspection of product appearance
  1. Check the appearance of bad phenomena caused by mold manufacturing, including: piercing, mold surface not smooth, mold surface uneven, mold printing, step difference, poor etching, top white, drag, sticking, etc.
  2. Check the appearance defects caused by the injection molding process, including: air lines, water lines, watermarks, scorching, shrinkage, lack of glue, top white, scratches, material flowers, deformation, etc.
Sixth: Inspection of product size

By adjusting the injection molding process, when the product has a better appearance, a preliminary inspection of the appearance size of the product is carried out. When the size and appearance are restricted, the following principles are followed:

  1. If the product size is too small, the injection molding process should be adjusted until the appearance of the product appears top white, top height, drag, and mold sticking, and find the maximum size that the injection molding process can adjust.
  2. If the product size is too large, the injection molding process should be adjusted until the appearance of the product shrinks, lack of glue, etc., and find the smallest size that the injection molding process can adjust.

As long as this can be done during mold tryout, and the mold problem is discovered and solved. It will provide great convenience for subsequent injection molding production. If you don’t do this during mold trial, the problems in the mold are not found or resolved, and the mold is produced with defects. Not only will the production not proceed smoothly, but the production cost will also be very high.


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Five tips for mold design-Xiamen Huaye Precision Moulding

Five Tips for Mold Design

When producing a plastic part, it is hard to make it perfect. Only after the design in the early stage can more problems be avoided in the later stage. Plastic product design plays a connecting role in avoiding many problems.

1) Comparing raw materials

Choose the right material among many materials, the first thing is to compare their performance, characteristics and cost,etc.

When the material’s use temperature is closer to its melting point, the temperature and time will directly affect the deformation performance of the raw material.

The characteristics of plastics are not only the one of pure raw materials. If the raw materials are processed in the inapplicable range, the best design will fail. Similarly, products cannot solve design weaknesses through processing. Therefore, only an optimized process that takes all factors into consideration can ensure the quality of plastic parts.

2) Design checklist

The goal of new product development or improvement is to make excellent performance at low production costs. The design tasks mainly include raw material and processing method selection, strength calculation and mold design.

Only when these factors are fully considered and systematically followed up can we produce high-quality, commercially-effective molds. We also have to emphasize that the practicality and cost efficiency of plastics are not inevitable, and designers must pay great attention to the selection of raw materials and correct solutions for the processing process.

3) Consider the gate design

The designer not only has to calculate the product design, but also must pay special attention to the gate design of the mold. They must choose the correct gate system and the number and location of gate points. Different gate types and positions will have a greater impact on the quality of products.

The selection of gate location will determine the following properties of plastic products:

Filling effect;

Final size of the product (tolerance);

Shrinkage, warpage;

Mechanical performance level;

Surface quality (appearance);

If the designer chooses the wrong gate, it is almost impossible to correct the consequences from optimizing the processing parameters during the molding process.

Basic design principles:

Do not place the gate in a high pressure area;

Try to avoid or reduce the fusion line;

Try to keep the fusion line away from the high pressure area;

For reinforced plastics, the gate position determines the warpage performance of the part;

Provide adequate exhaust ports to avoid air trapping.

4) Basic assembly process

Some simple assembly techniques recognized by all designers, such as snap assembly, press assembly and thread assembly, etc., can greatly save production costs by simply and quickly assembling components.

The biggest advantage of snap assembly is that no additional assembly parts are needed. In the buckle design, the designer must ensure the geometric dimensions of the accessories to avoid stress relaxation causing loose assembly components.

Press assembly can make plastic components high-strength assembly at the lowest cost.

The thread assembly consists of the use of separate, combined screw or integral screw inserts. In order to avoid the production of unqualified components, ensuring the correct sleeve size is a key part. Screw manufacturers can make many suggestions in this regard.

5)Cost-saving design

Designers bear most of the responsibility for the final cost of plastic parts. Their decision predetermines the cost of production, mold making and assembly. Later corrections and optimizations are usually expensive and infeasible.

Making full use of the advantages of the characteristics of plastic raw materials can save costs in many ways. Multifunctional integrated design, low-cost assembly technology (such as buckle, welding device, fixing device, two-material injection molding technology, etc.), use of self-lubricating properties, and no surface treatment procedures. Paying attention to wall thickness, molds, tolerances, raw materials, etc. can further save costs.

When a product is to be produced, it is mainly for profit, which is to reduce the cost of the product. The designer has an inseparable relationship with the final cost of the part. His decisions, ideas and final design are all related to the cost of the product. Make good use of the characteristics of plastics to control the cost. Considering some technologies in the mold, it can also reduce costs to a certain extent.


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Causes and Solutions of Injection Mold Rust

Causes and Solutions of Injection Mold Rust

Most of injection molds are made of chisel tool steel. During the molding, it encounters corrosive gases, water and other substances that cause rust. And Plastic parts made from rusty molds will have quality problems, so we need to know how to avoid the rust.

Causes and Solutions of Injection Mold Rust

Here are the causes and solutions of the rust:

Gas from melt decomposition

Some raw materials will produce volatile gases when heated or overheated. These gases are corrosive and diffuse around the machine. When injection mold is not working, they will corrode the mold.
In this regard, when the machine stops working, use a soft cloth to clean the mold and close the mold. If it is not used for a long time, the mold cavity should be sprayed with anti-rust agent.

Cooling water in the mold

Cooling water is often used in the mold to wake up and cool, so there is more moisture around the machine. If the mold is cooled below the dew point, the moisture in the air will form water droplets on the surface of the mold. If it is not wiped off in time, it will rust easily.
Especially after the mold stops working, condensed water will soon be generated. Therefore, do not stop molding easily, even if you want to stop, turn off the cooling water and wipe the mold dry.

Carbides produced during molding

After the mold works for a long time, carbides are precipitated and decomposed in the molding material, which often causes the mold to wear, corrode or rust. In this regard, if carbide formation is found, it should be wiped off and wiped off with a dry cloth immediately.


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Injection Parts Size Difference and Remedies from Xiamen Huaye Precision Moulding

Injection Parts Size Difference and Remedies

During the injection molding process, sometimes the change in weight and size of injection parts exceeds the production capacity of the mold, injection molding machine and plastic combination.

Injection Parts Size Difference and Remedies from Xiamen Huaye Precision Moulding

Here are the possible reasons and following remedies:

  1. Possible reasons for the problems

(1) The plastic in the injection cylinder is uneven.

(2) The temperature or fluctuation range of the injection cylinder is too high.

(3) The capacity of the injection molding machine is too small.

(4) The injection pressure is unstable.

(5) The screw reset is unstable.

(6) Changes in operating time and inconsistent solution viscosity.

(7) The injection speed (flow control) is unstable.

(8) Plastic varieties that are not suitable for molds are used.

(9) Consider the influence of mold temperature, injection pressure, speed, time and holding pressure on the product.


  1. Remedies

(1) Check whether there is sufficient cooling water flowing through the hopper throat to keep the appropriate temperature.

(2) Check whether the thermocouple is inferior or loose.

(3) Check whether the thermocouple used with the temperature controller is of the correct type.

(4) Check the injection volume and plasticizing capacity of the injection molding machine, and then compare it with the actual injection volume and the injection volume per hour.

(5) Check whether there is a stable molten material in every operation.

(6) Check whether the non-return valve to prevent backflow leaks, and replace it if necessary.

(7) Check whether the feeding setting is wrong.

(8) Ensure that the screw return position is stable during each operation, that is, no more than 0.4mm change.

(9) Check the inconsistency of operation time.

(10) Use back pressure.

(11) Check whether the hydraulic system is operating normally and whether the oil temperature is too high or too low (25~60℃).

(12) Choose plastic varieties suitable for molds (mainly considering shrinkage and mechanical strength).

(13) Readjust the entire production process.


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The layout principle of ejector pin from Huaye Precision Moulding

The layout principle of Ejector Pin

Ejector pins are the “bouncers” of the injection molding world. They apply a force to eject a part from the mold, and in some cases can leave marks. … Once the mold is opened, the pins extend into the mold cavity, push the part out, and then retract, allowing the mold to close and be refilled.

The ejection of a plastic product is the last step in the plastic injection molding process. The quality of the ejection determines the quality of the plastic product. When the mold opens, the plastic product must be retained on the mold half (usually the core) with the ejector mechanism that is used to release the plastic product.

     1.The ejector pin layout should make the ejection force as balanced as possible

The demolding force for complex structures is relatively large, so the number of ejectors should be increased accordingly.

  1. The ejector pin should be set in effective places

The effective places include the rib, column, step, metal insert and other complex structures. The ejector pin on both sides of the rib and column should be arranged symmetrically as much as possible. In addition, try to ensure the ejector pin on both sides of the column position.

  1. Avoid arranging ejector pinon the inclined surface or overstepping

The top surface should be as smooth as possible, and we should arrange it in the structural part of the rubber with better force.

  1. Flat ejector pin should be chosen in some cases

In the deep rib (depth ≥20mm) or it is difficult to arrange the dome ejector pin, we should adopt flat ejector pins. When we use it, try the insert form to facilitate processing.

  1. Avoid sharp and thin steel

When layout the ejector pin, we should avoid those sharp and thin steel. And the top surface of the ejector pin should not touch the cavity side.

  1. Consider the distance between the ejector pin and the waterway

Avoid affecting the processing and water leakage of the waterway.

  1. Consider the exhaust function of the ejector pin

In order to exhaust during ejection, it should be arranged in the part which is easy to form a vacuum. For example, in the larger plane of the cavity, although the packing force of the rubber part is small, it is easy to form a vacuum, which leads to an increase in the demolding force.

  1. The ejector pins cannot be placed in some places

For plastic parts with appearance requirements, it can not be in the appearance surface, and we should adopt other ejection methods. For transparent plastic parts, it can not be arranged in the part that needs to transmit light.


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Practical Precaution for Using Calipers

Practical Precautions for Using Calipers

The caliper is one of the most common measuring tool in the toolbox. It has many advantages such as multiple measurement modes, easy operation, durability, strong versatility, and low cost. However, there are still many precautions to use calipers correctly. Let’s start with the error factors that affect the measurement results.

Error factor

When measuring with calipers, there are many factors that cause errors, such as parallax, errors caused by the structure not conforming to Abbe’s principle, thermal expansion caused by the temperature difference between the caliper and the workpiece and so on.

In addition, because the caliper has no constant pressure device, it is difficult to grasp a suitable and uniform measuring force when measuring, which is another error factor.

1. The structure of the caliperdoes not conform to the Abbe principle

The reading and measuring axis of the caliper do not conform to the Abbe principle because of the different axes. Therefore, when using the caliper, measuring with the root or tip of the claw may increase the measurement error. When measuring, pay attention to the measured workpiece as close to the ruler body part (reading axis) as possible.

2. Read the parallax of the scale

When checking whether the vernier tick mark is aligned with the main tick mark, look directly at the vernier tick mark.

Practical Precaution for Using Calipers

There is a step height between the vernier ruler and the main ruler scale surface, which is easy to cause reading errors. As shown in the figure below, if you observe the vernier scale line from an oblique direction, the error shown by ΔX in the figure will occur. In order to avoid the influence of such factors, the JIS specification stipulates that the step height (H) should not be greater than 0.3mm.

3. The bending of the reference end face

If the ruler surface that guides the sliding of the vernier is bent, it will cause the error shown in the figure below. This error can be expressed by the same calculation formula as the error that does not conform to the Abbe principle.

Practical Precaution for Using Calipers

Example: Suppose the deformation caused by the bending of the guide ruler surface is 0.01mm/50mm, and the outer diameter measuring claw tip is 40mm to calculate: f=40mm×0.01÷50=0.008mm

4. Relationship between measurement and temperature

Caliper is generally made of stainless steel, which has the same thermal expansion coefficient (10.2±1)×10-6/K as ferrous metals. The material of the measured object, the room temperature and the temperature of the workpiece must be considered when measuring.

5. Notes on operation

The caliper claw is very sharp, so the instrument must be operated carefully to avoid personal injury.§

Avoid damaging the scale of the digital caliper, do not engrave the identification number or use the electric pen to leave other information.

Avoid colliding with hard objects or falling on the stool or floor to damage the calipers.

6. Maintenance of sliding surface and measuring surface

Before using the caliper, wipe off the dust and dirt on the sliding surface and the measuring surface with a soft dry cloth.

7. Check and calibrate the origin before use

Clamp a piece of clean paper between the outer claws, and then slowly pull it out. Before using the caliper, close the measuring jaw and make sure that the vernier scale (or display) returns to zero. When using a digital caliper, please reset (zero button) after replacing the battery.

8. Operation after use

After using the caliper, wipe off water and oil thoroughly. Then, lightly smear it with anti-rust oil, dry it before storing.

Waterproof calipers, in order to prevent rusting after use, also need to wipe off the moisture of the calipers.

9. Precautions for storage

Avoid direct sunlight, high temperature, low temperature and storage in high humidity environment.§

If the digital caliper is not used for more than three months, remove the battery before storing.

During storage, do not allow the outer measuring jaw of the caliper to be completely closed.


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How to solve the difficulty of Demolding by injection mold manufacturer

How to solve the difficulty of Demolding

After the plastic part is injection molded, it is ejected from the mold cavity, whether it is a single or multi-element ejection mechanism, the demolding work is generally completed at one time. But sometimes due to the special shape of the plastic part or the needs of production automation, the plastic part is still difficult to take out from the cavity or cannot fall off automatically after one demolding action. That means we need to make another demold to fall off the plastic part.

And there are some reasons for causing the difficulty of demolding in certain aspects:


(1)Insufficient ejector force.


(1) Unreasonable demoulding structure or improper position.

(2) The draft slope is not enough.

(3) Mold temperature is too high or poor ventilation.

(4) The runner wall or cavity surface is rough.

(5) The nozzle does not conform to the mold inlet or the nozzle diameter is larger than the inlet diameter.


(1) The barrel temperature is too high or the injection volume is too much.

(2) The injection pressure is too high or the holding and cooling time is too long.

4.Raw materials

(1)Insufficient lubricants.

How to solve the difficulty of Demolding by injection mold manufacturer

The traditional demoulding methods of plastic molded parts are roughly divided into four types: ejecting, pushing, pulling and rotating.

Now there is a new demoulding technology that can easily solve the problem of plastic demoulding. In the plastic mold industry, there are many unsolvable problems, especially when a variety of resin compounds are for highly complex designs and high-gloss finish processing.

Nano demoulding coating can form a coating on the surface of the plastic mold or even on the surface of the insert of the plastic mold, which can significantly reduce the friction coefficient of these surfaces, and a highly glossy processing surface can be achieved without using traditional mold release agents. Nano demoulding coating not only improves the smoothness and accuracy of the plastic mold surface, but also greatly improves the productivity of the plastic mold manufacturing industry!

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