The most complete in history: a summary of technical knowledge of plastic molds

Plastic mold

introduction

All kinds of tools and products used in our daily production and life, as large as the base of the machine tool, the body shell, as small as a blank head screw, buttons and the shell of various household appliances, are closely related to the mold. The shape of the mold determines the shape of these products, and the processing quality and precision of the mold also determine the quality of these products. Because of the different materials, appearance, specifications and uses of various products, molds are divided into casting molds, forging molds, die-casting molds, stamping molds and other non-plastic molds, as well as plastic molds.

In recent years, with the rapid development of the plastics industry and the continuous improvement of the strength and precision of general and engineering plastics, the application range of plastic products is also expanding, such as: household appliances, instrumentation, construction equipment, automotive industry, daily hardware and many other fields, the proportion of plastic products is rapidly increasing. A properly designed plastic part can often replace multiple traditional metal parts. The trend of plasticization of industrial products and daily products is increasing.

1 The general definition of the mold:

In industrial production, with a variety of presses and special tools installed on the press, through the pressure of metal or non-metallic materials to produce the required shape of parts or products, this special tool is collectively referred to as the mold.

2

Injection molding process description

A mold is a tool for the production of plastic products. It is composed of several groups of parts, and this combination has a forming die cavity. During injection molding, the mold is clamped on the injection molding machine, the molten plastic is injected into the molding cavity, and cooled in the cavity, and then the upper and lower molds are separated, and the products are ejected from the mold cavity through the ejecting system, and finally the mold is closed for the next injection molding, the whole injection molding process is cyclic.

3

General classification of molds

Can be divided into plastic mold and non-plastic mold:

(1) Non-plastic molds are: casting molds, forging molds, stamping molds, die-casting molds, etc.

A. Casting mold - faucet, pig iron platform

B. Forging die - car body

C. Stamping die - computer panel

D. Die casting mold - super alloy, cylinder body

(2) Plastic molds are divided into: according to the production process and different products:

A. Injection molding molds - TV housings, keyboard buttons (most commonly used)

B. Blow mold - beverage bottle

C. Compression molding die - bakelite switch, scientific porcelain dish

D. Transfer molding die - Integrated circuit product

E. Extrusion molding die -- glue tube, plastic bag

F. Thermoforming die - transparent molding package shell

G. Rotary mold - soft rubber doll toy

Injection molding is the most commonly used method in plastic processing. The method is suitable for all thermoplastics and some thermoset plastics, the quantity of plastic products produced is unmatched by other molding methods, and the injection mold, as one of the main tools of injection molding processing, has a high level of quality accuracy, manufacturing cycle and production efficiency in the injection molding process. Directly affect the quality of products, output, cost and product updates, but also determine the enterprise's response ability and speed in the market competition.

◆ Injection mold is composed of a number of steel plates with various parts, basically divided into:

A Forming device (die, punch)

B Positioning device (guide post, guide sleeve)

C Fixed device (I-plate, mold pit)

D Cooling system (water carrier)

E Constant temperature system (heating tube, heating wire)

F Runner system (sprue hole, runner slot, runner hole)

G Ejector system (thimble, ejector rod)

5 The mold can be divided into three types according to the different pouring system:

(1) Large nozzle mold: the runner and gate are on the parting mold line, and the product is demoulded when opening the mold, the design is the simplest, easy to process, and the cost is low, so more people use the large nozzle system operation.

(2) fine nozzle mold: the runner and gate are not on the parting line, generally directly on the product, so it is necessary to design more than a group of water parting line, the design is more complex, the processing is more difficult, generally depending on the product requirements and choose the fine nozzle system.

(3) Hot runner mold: This kind of mold structure is roughly the same as the fine water mouth, the biggest difference is that the runner is in one or more hot runner plates with constant temperature and hot mouth, no cold material demoulding, the runner and gate are directly on the product, so the runner does not need to demoulding, this system is also known as no water mouth system, can save raw materials, suitable for more expensive raw materials, products with higher requirements, design and processing difficulties, The mold cost is higher.

Hot runner system, also known as hot runner system, is mainly composed of hot gate cover, hot runner plate, temperature control box. Our common hot runner system has two forms of single point hot gate and multi-point hot gate. A single point hot gate is a single hot gate sleeve that directly pours molten plastic into the mold cavity, which is suitable for a single cavity and a single gate plastic mold; The multi-point hot gate is to branch the molten material into each hot gate sleeve through the hot runner plate and then enter the mold cavity, which is suitable for single cavity multi-point feeding or multi-cavity mold.

Advantages of hot runner system

(1) No water inlet material, no post-processing is required, so that the entire molding process is completely automated, saving working time and improving work efficiency.

(2) Small pressure loss. The temperature of the hot runner is equal to that of the injection molding machine nozzle, which avoids the surface condensation of the raw material in the runner, and the injection pressure loss is small.

(3) The reuse of nozzle material will degrade the performance of plastics, and the use of hot runner system without nozzle material can reduce the loss of raw materials, thereby reducing the cost of products. The temperature and pressure in the cavity are uniform, the stress of the plastic parts is small, the density is uniform, and the product is better than the general injection molding system under the smaller injection pressure and the shorter molding time. For transparent parts, thin parts, large plastic parts or high requirements of plastic parts can show its advantages, and can produce larger products with smaller models.

(4) The hot nozzle adopts standardized and serialized design, equipped with a variety of optional nozzle heads, and has good interchangeability. The electric heating ring with unique design and processing can achieve uniform heating temperature and long service life. Hot runner system equipped with hot runner plate, temperature controller, etc., compact design, variety, easy to use, stable and reliable quality.

◆ Shortcomings of hot runner system application

(1) The overall mold closing height increased, due to the addition of hot runner plate, the overall height of the mold increased.

(2) The heat radiation is difficult to control, the biggest problem of the hot runner is the heat loss of the runner, which is a major issue to be solved.

(3) There is thermal expansion, thermal expansion and cold contraction is a problem to be considered when we design.

(4) The increase in mold manufacturing costs and the high price of standard accessories for hot runner systems affect the popularity of hot runner molds.

Injection molding defect solution

1 crack

Cracking is a common defect in plastic products, which is mainly caused by stress deformation. There are mainly residual stress, external stress and stress deformation caused by external environment.

(-) Cracking caused by residual stress

The residual stress is mainly caused by the following three conditions, namely, overfill, stripout and metal inserts. As a crack generated in the case of overfilling, its solution can mainly be started in the following aspects:

(1) Because the pressure loss of the straight gate is minimal, if the crack is mainly generated near the straight gate, it can be considered to use the multi-point distribution gate, side gate and handle gate.

(2) Under the premise of ensuring that the resin does not decompose and deteriorate, appropriately increasing the temperature of the resin can reduce the melting viscosity, improve the fluidity, and also reduce the injection pressure to reduce the stress.

(3) Under normal circumstances, when the mold temperature is low, it is easy to produce stress, and the temperature should be appropriately increased. However, when the injection speed is higher, even if the mold temperature is lower, the stress can be reduced.

(4) The injection and pressure holding time is too long will also produce stress, and it is better to shorten it appropriately or perform Th time pressure holding switch.

(5) Non-crystalline resins, such AS AS resins, ABS resins, PMMA resins, etc. are more prone to residual stress than crystalline resins such as polyethylene, polyformaldehyde, etc., which should be paid attention to.

When the ejecting rod is pushed out, the ejecting force is too large, the stress is generated, and sometimes even whitening or cracking occurs around the ejecting rod because the ejecting inclination is small, the mold type glue and the punch are rough. The cause can be determined by carefully observing the location of the crack.

When inserting metal parts at the same time of injection molding, it is most easy to produce stress, and it is easy to produce cracks after a period of time, which is very harmful. This is mainly due to the difference in the coefficient of thermal expansion of the metal and the resin to produce stress, and over time, the stress exceeds the strength of the gradually deteriorating resin material and cracks. To prevent the resulting cracking, as a rule of thumb, the wall thickness is 7" with the outer diameter of the embedded metal piece

General purpose polystyrene is basically not suitable for adding inlays, and inlays have the least impact on nylon. Because the thermal expansion coefficient of glass fiber reinforced resin material is small, it is more suitable for embeddings.

In addition, preheating the metal insert before forming also has a good effect.

(2) Cracking caused by external stress

The external stress here is mainly caused by unreasonable design and stress concentration, especially at sharp corners. As shown in Figure 2-2, R / 7" is 0.5 to 0.7.

(3) Cracks caused by external environment

Chemicals, moisture absorption caused by water degradation, and excessive use of recycled materials will cause physical deterioration, resulting in cracking.

12 Underfilling

The main reasons for insufficient filling are as follows:

i. Insufficient resin capacity.

ii. Insufficient pressure in the cavity.

iii. Insufficient fluidity of resin.

iv. Bad exhaust effect.

As improvement measures, we can mainly start from the following aspects:

1) The injection time is extended to prevent the resin from counter-current and difficult to fill the cavity before the gate curing due to the short molding cycle.

2) Increase the injection speed.

3) Increase mold temperature.

4) Increase resin temperature.

5) Increase injection pressure.

6) Expand the size of the gate. The height of the gate should be equal to 1/2 ~ l / 3 of the wall thickness of the product.

7) The gate is set at the place where the wall thickness of the product is the largest.

8) Set the exhaust groove (average depth 0.03mm, width 3 ~ smm) or exhaust rod. It is more important for smaller workpieces.

9) There is a certain buffer distance (about smm) between the screw and the injection nozzle.

10) Choose materials with low viscosity grade. 11) Add lubricant.

3 Wrinkle and pockmark

The cause of this defect is essentially the same as underfilling, but to a different degree. Therefore, the solution is basically the same as above. Especially for resins with poor fluidity (such as polyformaldehyde, PMMA resin, polycarbonate and PP resin, etc.), it is more necessary to pay attention to appropriately increasing the gate and appropriate injection time.

4 pit

The reason for the shrinkage of the pit is also the same as the insufficient filling, in principle can be solved by excess filling, but there will be the risk of stress, should pay attention to the design of uniform wall thickness, should be as far as possible to reduce the reinforcement rib, convex column and other places of wall thickness.

5 Overflow edge

The treatment of overflow should mainly focus on the improvement of the mold. In terms of forming conditions, it can be started in terms of reducing liquidity. Specifically, the following methods can be used:

1) Reduce injection pressure.

2) Reduce the resin temperature.

4) Select materials with high viscosity grade.

5) Reduce mold temperature.

6) Mold surface where grinding overflow occurs.

7) The use of hard mold steel.

8) Improve the clamping force.

9) Adjust the joint surface and other parts of the accurate mold.

10) Increase the mold support column to increase rigidity.

ll) Determine the dimensions of different exhaust tanks according to different materials.

6 Weld marks

The weld mark is caused by the front part of the molten resin from different directions being cooled and not fully fused at the junction

Yes. Under normal circumstances, it mainly affects the appearance, and has an impact on coating and electroplating. In severe cases, the strength of the product is affected

(Especially in the case of fiber reinforced resins, especially serious). Improvements can be made by referring to the following:

l) Adjust molding conditions to improve fluidity. For example, increase the resin temperature, increase the mold temperature, increase the injection pressure and speed

Let's wait.

2) Adding an exhaust groove and setting a push-out rod at the place where the weld mark is generated is also conducive to exhaust.

3) Minimize the use of release agent.

4) Set the process overflow material and use it as the generation place of the weld mark, and then cut off and remove it after forming.

5) If it only affects the appearance, the burning position can be changed to change the position of the weld mark. Or the part produced by the weld mark is treated as a dark gloss surface, etc., to be modified.

7 Burns

Depending on the cause of the burn caused by machinery, mold or forming conditions, the solution is also different.

1) Mechanical reasons, such as overheating of the barrel due to abnormal conditions, causing the resin to decompose at high temperature, burn and inject into the product

Or due to the nozzle and screw thread in the material, check valve and other parts caused by resin stagnation, decomposition and discoloration into the product, with black brown burn marks in the product. At this time, the nozzle, screw and barrel should be cleaned.

2) The reason for the mold is mainly due to poor exhaust. This kind of burn generally occurs in a fixed place and is easily associated with the first

A case difference. At this time, we should pay attention to measures such as adding exhaust tank and reversing exhaust rod.

3) In terms of forming conditions, when the back pressure is above 300MPa, it will overheat part of the cylinder, causing burns. Screw speed

When it is too high, it will also generate overheating, generally in the range of 40 to 90r/min. When there is no exhaust tank or the exhaust tank is small, the injection speed is too high, which can cause superheated gas burns.

8 Silver wire

Silver wire is mainly caused by the hygroscopicity of the material. Therefore, it should generally be 10 ~ 15C lower than the thermal deformation temperature of the resin

Dry under conditions. For the PMMA tree wax series with higher requirements, it needs to be dried at about 75t for 4 to 6h. Especially when using automatic drying hopper, it is necessary to choose a reasonable capacity according to the molding cycle (molding amount) and drying time, and the drying material should be turned on a few hours before the injection begins.

In addition, the material inside the material flow time is too long will also produce silver line. When different kinds of materials are mixed, such as polystyrene

Plastic mold

introduction

All kinds of tools and products used in our daily production and life, as large as the base of the machine tool, the body shell, as small as a blank head screw, buttons and the shell of various household appliances, are closely related to the mold. The shape of the mold determines the shape of these products, and the processing quality and precision of the mold also determine the quality of these products. Because of the different materials, appearance, specifications and uses of various products, molds are divided into casting molds, forging molds, die-casting molds, stamping molds and other non-plastic molds, as well as plastic molds.

In recent years, with the rapid development of the plastics industry and the continuous improvement of the strength and precision of general and engineering plastics, the application range of plastic products is also expanding, such as: household appliances, instrumentation, construction equipment, automotive industry, daily hardware and many other fields, the proportion of plastic products is rapidly increasing. A properly designed plastic part can often replace multiple traditional metal parts. The trend of plasticization of industrial products and daily products is increasing.

1 The general definition of the mold:

In industrial production, with a variety of presses and special tools installed on the press, through the pressure of metal or non-metallic materials to produce the required shape of parts or products, this special tool is collectively referred to as the mold.

2

Injection molding process description

A mold is a tool for the production of plastic products. It is composed of several groups of parts, and this combination has a forming die cavity. During injection molding, the mold is clamped on the injection molding machine, the molten plastic is injected into the molding cavity, and cooled in the cavity, and then the upper and lower molds are separated, and the products are ejected from the mold cavity through the ejecting system, and finally the mold is closed for the next injection molding, the whole injection molding process is cyclic.

3

General classification of molds

Can be divided into plastic mold and non-plastic mold:

(1) Non-plastic molds are: casting molds, forging molds, stamping molds, die-casting molds, etc.

A. Casting mold - faucet, pig iron platform

B. Forging die - car body

C. Stamping die - computer panel

D. Die casting mold - super alloy, cylinder body

(2) Plastic molds are divided into: according to the production process and different products:

A. Injection molding molds - TV housings, keyboard buttons (most commonly used)

B. Blow mold - beverage bottle

C. Compression molding die - bakelite switch, scientific porcelain dish

D. Transfer molding die - Integrated circuit product

E. Extrusion molding die -- glue tube, plastic bag

F. Thermoforming die - transparent molding package shell

G. Rotary mold - soft rubber doll toy

Injection molding is the most commonly used method in plastic processing. The method is suitable for all thermoplastics and some thermoset plastics, the quantity of plastic products produced is unmatched by other molding methods, and the injection mold, as one of the main tools of injection molding processing, has a high level of quality accuracy, manufacturing cycle and production efficiency in the injection molding process. Directly affect the quality of products, output, cost and product updates, but also determine the enterprise's response ability and speed in the market competition.

◆ Injection mold is composed of a number of steel plates with various parts, basically divided into:

A Forming device (die, punch)

B Positioning device (guide post, guide sleeve)

C Fixed device (I-plate, mold pit)

D Cooling system (water carrier)

E Constant temperature system (heating tube, heating wire)

F Runner system (sprue hole, runner slot, runner hole)

G Ejector system (thimble, ejector rod)

5 The mold can be divided into three types according to the different pouring system:

(1) Large nozzle mold: the runner and gate are on the parting mold line, and the product is demoulded when opening the mold, the design is the simplest, easy to process, and the cost is low, so more people use the large nozzle system operation.

(2) fine nozzle mold: the runner and gate are not on the parting line, generally directly on the product, so it is necessary to design more than a group of water parting line, the design is more complex, the processing is more difficult, generally depending on the product requirements and choose the fine nozzle system.

(3) Hot runner mold: This kind of mold structure is roughly the same as the fine water mouth, the biggest difference is that the runner is in one or more hot runner plates with constant temperature and hot mouth, no cold material demoulding, the runner and gate are directly on the product, so the runner does not need to demoulding, this system is also known as no water mouth system, can save raw materials, suitable for more expensive raw materials, products with higher requirements, design and processing difficulties, The mold cost is higher.

Hot runner system, also known as hot runner system, is mainly composed of hot gate cover, hot runner plate, temperature control box. Our common hot runner system has two forms of single point hot gate and multi-point hot gate. A single point hot gate is a single hot gate sleeve that directly pours molten plastic into the mold cavity, which is suitable for a single cavity and a single gate plastic mold; The multi-point hot gate is to branch the molten material into each hot gate sleeve through the hot runner plate and then enter the mold cavity, which is suitable for single cavity multi-point feeding or multi-cavity mold.

Advantages of hot runner system

(1) No water inlet material, no post-processing is required, so that the entire molding process is completely automated, saving working time and improving work efficiency.

(2) Small pressure loss. The temperature of the hot runner is equal to that of the injection molding machine nozzle, which avoids the surface condensation of the raw material in the runner, and the injection pressure loss is small.

(3) The reuse of nozzle material will degrade the performance of plastics, and the use of hot runner system without nozzle material can reduce the loss of raw materials, thereby reducing the cost of products. The temperature and pressure in the cavity are uniform, the stress of the plastic parts is small, the density is uniform, and the product is better than the general injection molding system under the smaller injection pressure and the shorter molding time. For transparent parts, thin parts, large plastic parts or high requirements of plastic parts can show its advantages, and can produce larger products with smaller models.

(4) The hot nozzle adopts standardized and serialized design, equipped with a variety of optional nozzle heads, and has good interchangeability. The electric heating ring with unique design and processing can achieve uniform heating temperature and long service life. Hot runner system equipped with hot runner plate, temperature controller, etc., compact design, variety, easy to use, stable and reliable quality.

◆ Shortcomings of hot runner system application

(1) The overall mold closing height increased, due to the addition of hot runner plate, the overall height of the mold increased.

(2) The heat radiation is difficult to control, the biggest problem of the hot runner is the heat loss of the runner, which is a major issue to be solved.

(3) There is thermal expansion, thermal expansion and cold contraction is a problem to be considered when we design.

(4) The increase in mold manufacturing costs and the high price of standard accessories for hot runner systems affect the popularity of hot runner molds.

Injection molding defect solution

1 crack

Cracking is a common defect in plastic products, which is mainly caused by stress deformation. There are mainly residual stress, external stress and stress deformation caused by external environment.

(-) Cracking caused by residual stress

The residual stress is mainly caused by the following three conditions, namely, overfill, stripout and metal inserts. As a crack generated in the case of overfilling, its solution can mainly be started in the following aspects:

(1) Because the pressure loss of the straight gate is minimal, if the crack is mainly generated near the straight gate, it can be considered to use the multi-point distribution gate, side gate and handle gate.

(2) Under the premise of ensuring that the resin does not decompose and deteriorate, appropriately increasing the temperature of the resin can reduce the melting viscosity, improve the fluidity, and also reduce the injection pressure to reduce the stress.

(3) Under normal circumstances, when the mold temperature is low, it is easy to produce stress, and the temperature should be appropriately increased. However, when the injection speed is higher, even if the mold temperature is lower, the stress can be reduced.

(4) The injection and pressure holding time is too long will also produce stress, and it is better to shorten it appropriately or perform Th time pressure holding switch.

(5) Non-crystalline resins, such AS AS resins, ABS resins, PMMA resins, etc. are more prone to residual stress than crystalline resins such as polyethylene, polyformaldehyde, etc., which should be paid attention to.

When the ejecting rod is pushed out, the ejecting force is too large, the stress is generated, and sometimes even whitening or cracking occurs around the ejecting rod because the ejecting inclination is small, the mold type glue and the punch are rough. The cause can be determined by carefully observing the location of the crack.

When inserting metal parts at the same time of injection molding, it is most easy to produce stress, and it is easy to produce cracks after a period of time, which is very harmful. This is mainly due to the difference in the coefficient of thermal expansion of the metal and the resin to produce stress, and over time, the stress exceeds the strength of the gradually deteriorating resin material and cracks. To prevent the resulting cracking, as a rule of thumb, the wall thickness is 7" with the outer diameter of the embedded metal piece

General purpose polystyrene is basically not suitable for adding inlays, and inlays have the least impact on nylon. Because the thermal expansion coefficient of glass fiber reinforced resin material is small, it is more suitable for embeddings.

In addition, preheating the metal insert before forming also has a good effect.

(2) Cracking caused by external stress

The external stress here is mainly caused by unreasonable design and stress concentration, especially at sharp corners. As shown in Figure 2-2, R / 7" is 0.5 to 0.7.

(3) Cracks caused by external environment

Chemicals, moisture absorption caused by water degradation, and excessive use of recycled materials will cause physical deterioration, resulting in cracking.

12 Underfilling

The main reasons for insufficient filling are as follows:

i. Insufficient resin capacity.

ii. Insufficient pressure in the cavity.

iii. Insufficient fluidity of resin.

iv. Bad exhaust effect.

As improvement measures, we can mainly start from the following aspects:

1) The injection time is extended to prevent the resin from counter-current and difficult to fill the cavity before the gate curing due to the short molding cycle.

2) Increase the injection speed.

3) Increase mold temperature.

4) Increase resin temperature.

5) Increase injection pressure.

6) Expand the size of the gate. The height of the gate should be equal to 1/2 ~ l / 3 of the wall thickness of the product.

7) The gate is set at the place where the wall thickness of the product is the largest.

8) Set the exhaust groove (average depth 0.03mm, width 3 ~ smm) or exhaust rod. It is more important for smaller workpieces.

9) There is a certain buffer distance (about smm) between the screw and the injection nozzle.

10) Choose materials with low viscosity grade. 11) Add lubricant.

3 Wrinkle and pockmark

The cause of this defect is essentially the same as underfilling, but to a different degree. Therefore, the solution is basically the same as above. Especially for resins with poor fluidity (such as polyformaldehyde, PMMA resin, polycarbonate and PP resin, etc.), it is more necessary to pay attention to appropriately increasing the gate and appropriate injection time.

4 pit

The reason for the shrinkage of the pit is also the same as the insufficient filling, in principle can be solved by excess filling, but there will be the risk of stress, should pay attention to the design of uniform wall thickness, should be as far as possible to reduce the reinforcement rib, convex column and other places of wall thickness.

5 Overflow edge

The treatment of overflow should mainly focus on the improvement of the mold. In terms of forming conditions, it can be started in terms of reducing liquidity. Specifically, the following methods can be used:

1) Reduce injection pressure.

2) Reduce the resin temperature.

4) Select materials with high viscosity grade.

5) Reduce mold temperature.

6) Mold surface where grinding overflow occurs.

7) The use of hard mold steel.

8) Improve the clamping force.

9) Adjust the joint surface and other parts of the accurate mold.

10) Increase the mold support column to increase rigidity.

ll) Determine the dimensions of different exhaust tanks according to different materials.

6 Weld marks

The weld mark is caused by the front part of the molten resin from different directions being cooled and not fully fused at the junction

Yes. Under normal circumstances, it mainly affects the appearance, and has an impact on coating and electroplating. In severe cases, the strength of the product is affected

(Especially in the case of fiber reinforced resins, especially serious). Improvements can be made by referring to the following:

l) Adjust molding conditions to improve fluidity. For example, increase the resin temperature, increase the mold temperature, increase the injection pressure and speed

Let's wait.

2) Adding an exhaust groove and setting a push-out rod at the place where the weld mark is generated is also conducive to exhaust.

3) Minimize the use of release agent.

4) Set the process overflow material and use it as the generation place of the weld mark, and then cut off and remove it after forming.

5) If it only affects the appearance, the burning position can be changed to change the position of the weld mark. Or the part produced by the weld mark is treated as a dark gloss surface, etc., to be modified.

7 Burns

Depending on the cause of the burn caused by machinery, mold or forming conditions, the solution is also different.

1) Mechanical reasons, such as overheating of the barrel due to abnormal conditions, causing the resin to decompose at high temperature, burn and inject into the product

Or due to the nozzle and screw thread in the material, check valve and other parts caused by resin stagnation, decomposition and discoloration into the product, with black brown burn marks in the product. At this time, the nozzle, screw and barrel should be cleaned.

2) The reason for the mold is mainly due to poor exhaust. This kind of burn generally occurs in a fixed place and is easily associated with the first

A case difference. At this time, we should pay attention to measures such as adding exhaust tank and reversing exhaust rod.

3) In terms of forming conditions, when the back pressure is above 300MPa, it will overheat part of the cylinder, causing burns. Screw speed

When it is too high, it will also generate overheating, generally in the range of 40 to 90r/min. When there is no exhaust tank or the exhaust tank is small, the injection speed is too high, which can cause superheated gas burns.

8 Silver wire

Silver wire is mainly caused by the hygroscopicity of the material. Therefore, it should generally be 10 ~ 15C lower than the thermal deformation temperature of the resin

Dry under conditions. For the PMMA tree wax series with higher requirements, it needs to be dried at about 75t for 4 to 6h. Especially when using automatic drying hopper, it is necessary to choose a reasonable capacity according to the molding cycle (molding amount) and drying time, and the drying material should be turned on a few hours before the injection begins.

In addition, the material inside the material flow time is too long will also produce silver line. When different kinds of materials are mixed, such as polystyrene

. And ABS resin, AS resin, polypropylene and polystyrene should not be mixed.

9 Jet streaks

Jet marks are marks that curve like snakes along the flow direction from the gate. It is caused by the excessive injection rate of the resin from the gate. Therefore, enlarging the four cross sections or reducing the injection speed are optional

. And ABS resin, AS resin, polypropylene and polystyrene should not be mixed.

9 Jet streaks

Jet marks are marks that curve like snakes along the flow direction from the gate. It is caused by the excessive injection rate of the resin from the gate. Therefore, enlarging the four cross sections or reducing the injection speed are optional