PC/ABS Polycarbonate and acrylonitrile-butadiene-styrene copolymer and polymer
PC/ABS Polycarbonate and acrylonitrile-butadiene-styrene copolymer and polymer raw materials main application scope: computer and commercial machine shells, electrical equipment, lawn gardening machines, auto parts dashboards, automobile interior parts, ventilators, air conditioners, vacuum cleaners, color TVs, lighting equipment, computers, telephones and hair dryers, aircraft, automobiles, scientific research equipment, instrument frames, instrument panels, knobs, switches, steering wheel shells, air conditioners, shock absorbers, gardening tools and equipment, power tool shells, etc. In the interior decoration and wheel cover and other products, plastic products are widely used in this raw material.
Injection mold process conditions: Drying treatment: Drying treatment before processing is necessary. The humidity should be less than 0.03%, and the recommended drying conditions are 90~110℃, 2~4 hours.
melting temperature: 230~270℃. Mold temperature: 70~100℃.
PC/ABS plastic chemical and physical characteristics: PC/ABS has the comprehensive characteristics of both PC and ABS. For example, the easy processing characteristics of ABS and the excellent mechanical characteristics and thermal stability of PCs. The ratio of the two will affect the thermal stability of PC/ABS materials. PC/ABS, a polymeric material, also shows excellent flow characteristics.
Its main features are: extremely high impact strength, good thermal stability, excellent chemical corrosion resistance, better dimensional stability than PA raw materials, special surface soft matte effect, shock absorption and sound absorption performance brought by blending crystalline materials with amorphous materials.
PC/ABS injection molding processing 9 kinds of bad problems and solutions
. The silver wire that occurs during PC/ABS injection molding production and processing
The reason for the poor silver wire on the surface of plastic products is the most common problem of PC/ABS materials. Silver wire, also known as silver patterns, water splashes, and flower flowers, are silver white silk stripes that appear along the direction of injection flow on the surface of the product.
The main reason is that it is disturbed by gas, and the gas produced is mainly divided into three components:
(1) Air: the air involved in the melt glue and the injection stage;
(2) Moisture: the moisture contained in the material itself;
(3) cracking gas : the gas generated by high temperature hydrolysis/thermal decomposition.
Solution: First of all, we should check whether the raw materials are dry enough. When we confirm that the raw materials are drying enough, check whether the back pressure pressure of the process is too low. Generally, the back pressure pressure should be set between 10-15MPa. Then adjust the injection molding process to improve silver wire defects. At the same time, the poor injection molded silver wire is also related to the mold exhaust.
. Flow marks that occur during PC/ABS injection molding production and processing
Product surface flow marks are generated when the material is injected and filled. The reason is that the raw material has poor fluidity. The flow marks are different from silver marks. They are not caused by problems caused by moisture or decomposition of raw materials, and their appearance is also different from silver marks.
Solution: It can be avoided by increasing the raw material temperature, which is what we are talking about, thereby improving the fluidity. Appropriately increasing the mold temperature to increase the fluidity of the raw material in the mold and reducing the injection speed can also be solved.
. The shrinkage and dent problems occurred during PC/ABS injection molding production and processing
shrinkage is caused by insufficient filling and molding of the material in the mold cavity. There are also many reasons for the shrinkage of plastic products, the mold temperature is too high or too bottomed, the injection molding time is too short, the injection molding pressure is too small, the injection molding speed is too slow, the pressure hold time is too short, the pressure hold pressure is too small, and the back pressure pressure is too small, resulting in insufficient plastic density. Problems such as short cooling time will cause shrinkage of plastic products.
Solution: Appropriately increase the mold temperature or reduce the mold temperature and raw material temperature to improve the flowability of raw materials, extend the pressure holding time of injection, increase the injection pressure, increase the injection speed to improve mold filling ability, and also increase the size of gate , and heat the gate runner to reduce and eliminate product shrinkage.
shrinkage is caused by improper temperature control of raw materials and inappropriate product design. When the raw material temperature is too low, not only shrinkage holes will occur, but also dent problems will occur. The material temperature is too high and the mold temperature is too high, which will cause the melt to shrink excessively when cooling, resulting in dents and shrinkage holes.
Solution: Use appropriate processing temperature to increase injection speed and measures.
. Warpage deformation problems occur during PC/ABS injection molding production and processing
warpage deformation of injection molded plastic products is due to unreasonable product design and mold making, improper gate position setting, and unreasonable debugging of injection molding process conditions, resulting in internal stress, uneven shrinkage or excessive, excessive mold temperature, excessive mold temperature, causing difficult decompression of plastic parts, or uneven cooling, which will also cause warpage deformation.
injection molding processing solution:
molding process: lengthen injection molding cycles, reduce the injection molding temperature, appropriately adjust the injection pressure and injection speed, increase the holding time and holding pressure, increase the back pressure pressure, and at the same time slow down the ejection speed, increase the ejection area, and maintain the ejection force balance.
Product design: increasing the wall thickness, adding reinforcement at reinforcement and rounded corners can reduce warping and deformation.
5. Cold material marking problems occur during PC/ABS injection molding production and processing
PC/ABS cold material markings is usually caused by the high-speed injection, the injection nozzle temperature is too low, the mold temperature is too low, the back pressure is too large to produce material flow, the loose and retreat position is too short or too long, and the melt expands into the mold cavity and causes "melt rupture".
Solution:
1 Forming process: raising the raw material temperature, increasing the nozzle temperature, reducing the back pressure pressure, slowing the injection speed, etc. to reduce the occurrence of cold material marks;
1 Mold: raising the mold temperature, adding overflow grooves, increasing gate size, and modifying gate shape.
6. Pig spot problems occur during PC/ABS injection molding production and processing
Here Pig spot problems occur during PC/ABS injection molding production and processing. Generally, the raw materials are poorly dispersed, the material pipe temperature is too low, the back pressure is too low, the mold temperature is too low, the mold steel quality is too poor, the mold rust is also caused.
injection molding processing solution: poor dispersion, add dispersant or diffusing oil, increase the temperature, and increase the back pressure.
Note whether there is a mold problem. Try using other ingredients. Is the baking temperature time sufficient?
mold temperature adjustment.
7. Product peeling problems occur during PC/ABS injection molding production and processing
plastic product peeling problems are closely related to the rupture of fluid caused by high shear force. At low shear stress or low speed, small disturbances caused by various factors are suppressed by the melt; while under high shear stress or rate, disturbances in the fluid are difficult to suppress and develop into unstable flow; when a critical shear force is reached, the rupture of the fluid will be caused.
Injection molding processing solution:
Material: The two components of PC/ABS are partially compatible, so appropriate compatibility must be added during the modification process to improve its compatibility. The raw materials include PP. The peeling caused by PE raw materials. Of course, the peeling defect caused by the mixture is the first step to eliminate;
mold: the principle of mold design must follow the direction of minimizing shear.Generally speaking, products with dense leather patterns are more likely to peel (when we are in the injection molding process, it is caused by friction and shearing of the melt in the cavity and the inner wall of the cavity during high-speed filling); at the same time, in the mold gate design, the gate size is too small, which will cause excessive shear when the melt passes through the gate, which will lead to excessive shear on the product surface;
Injection molding process: the main direction is to avoid excessive shearing. When is difficult to fill in product , it can be improved by high-speed and high-pressure. Therefore, in the actual injection molding process, it is also possible to consider increasing the injection molding temperature/mold temperature and improving material flowability to reduce the flow resistance during the actual filling process, thereby avoiding excessive shear caused by high-speed and high-pressure.
8. Product gas pattern problems occur during PC/ABS injection molding production and processing
PC/ABS injection molding parts processing gate We usually have the most likely defect of gas pattern in injection molding. As mentioned earlier, it is caused by the fast injection molding speed. Therefore, to solve the problem of air marking in the gate, it is necessary to try to reduce the injection speed without causing shock marking and material shortage. To this end, we must first ensure that the melt has a high enough temperature, and try to increase the melt temperature as much as possible without discoloration or burning. It is better to reach 280°C-290°C.
(1) The main reason for the air mark at the gate of the product is that the mold is too narrow to open, and the PC/ABS flow performance itself is not very good, which makes it difficult to fill the cavity during the injection molding process.
(2) The first and second sections ejaculate too fast.
(3) The temperature of the material tube is too low, making it difficult for plastic to inject into the cavity.
(4) The mold temperature is too low, and the mold temperature is too low, it will make it difficult for the plastic to fill.
(5) When debugging the process, the injection position is not grasped correctly and the speed setting is incorrect, which will cause air patterns on the surface of the product.
So how do we solve these problems?
(1) Add glue injection points or improve the glue method, especially the ox horn glue injection is the least substitute glue injection method. The runner adopts an S-shaped runner to facilitate exhaust gas. It is better to use a fan-shaped glue injection method.
(2) Increase the temperature of the material pipe and add the temperature to the situation where the product quality problems do not affect the product and does not cause decomposition of the plastic. Under normal circumstances, 280°C-290°C is the basic one.
(3) The mold temperature is too low. Without affecting the product shrinkage, try to increase the mold temperature to 100°C-120°C, so as to facilitate the plastic flow and injection into the mold cavity quickly during the injection process. Secondly, it is also a relatively important factor, that is, the cavity temperature of the mold must be increased to 90-110°C. In production, molds with cores can usually be turned off by turning off the mold cooling water to achieve the purpose of heating. When the mold temperature rises above 90°C, you can use a very slow speed to debug. The gate marks of the injection molded parts will gradually fade as the injection speed decreases until they disappear.
When the melt flows through the area where the air pattern is formed, it must be converted to high-speed injection immediately, otherwise injection molded parts will produce shock patterns and material shortages. It should be noted that the mold temperature cannot rise too high. Injected parts exceeding 120°C are prone to shrinkage and deformation problems, and the cooling time must be increased. The production cycle of becomes slow. At the same time, the life of the mold is shortened due to the high mold temperature. There may even be dumb color problems on the surface of the injection molded parts. Try not to use oil heaters to raise the mold temperature for the sake of workers' safety. Because if the hot oil temperature is adjusted to above 90°C, the consequences will be unimaginable once the oil leakage problem occurs. Therefore, you must pay attention to safety when using a hot oil machine. Safety production should be put first.
If the production of precision injection molded parts is thin and large, the heat of the melt will dissipate very quickly and the heat is also limited. It is difficult for the mold temperature to rise, and whether the material can be completed is a problem.At this time, it is necessary to heat the heating pipe inside the
mold to achieve the purpose of heating. At the same time, it is also necessary to increase the gate width to increase the flow rate of melt filling and reduce the filling time to facilitate filling the cavity and eliminating air patterns.
(4) When we debug the process, we must first grasp the position of the injection,
Method 1: For example, the position of my storage volume is 100MM. Then the preset value of the first section of the injection is 80MM,
Method 2: We also control the position of the injection end point to maintain pressure at 80MM. First, we can see how much material the material head has, and then debug it. Remember, the position of the first section must be controlled at the position where the material head is at the glue gate where the product comes in contact with the gate. The speed is controlled between 20 and 25 and the pressure is controlled between 90 and 100 MAP. Note that the speed and pressure in the first section cannot be too high or too fast.
Method 3: Then, between the position of the second section and the position of the first section where the position of the first section is 3MM-9MM, the speed is controlled between 5 and 9. The pressure cannot be too high, and the pressure should be controlled between 80 and 90 as much as possible. Too much pressure will cause air patterns to appear and snake patterns to not be eliminated.
Method 4: Back pressure adjustment is generally controlled between 8 and 10MAP, but here the first thing is to control the loosening position. If the temperature of your injection nozzle is too low, the back pressure is too large, and the loosening position is controlled relatively small. Injection of cold material into the cavity here will lead to the appearance of air patterns, so try not to inject cold material into the mold.
Method 5: Then switch the position of the third section and the pressure holding position, and appropriately control it to the product to reach 90%. For example, the position can be controlled at 25MM to switch to the fourth section until the product is full.
Remember that the speed of the third and fourth sections must be fast, try to control it at high speed and inject plastic into the cavity under high pressure. The general speed is controlled between 95 and 99 and the pressure is between 120MPA. Finally, check whether the product still has air patterns. If there is no more, then first produce between 5 and 10 molds to see if there is any change. If there is no change, the time and speed pressure will be maintained.
9. Product snake pattern problems occur during PC/ABS injection molding production and processing
I have already mentioned in my previous article. There are many times when we produce PC/ABS raw materials, we will have some bad problems and are helpless and at a loss. So today, Bochuang talks about management to help you analyze and solve them. The most common problem we often encounter when producing PC/ABS materials is that snake patterns and air patterns appear at the gates, which are the most common. So what causes such problems? Let me make a detailed analysis below.
(1) The main reason for snake patterns at the gate of the product is that the mold is too narrow to open the glue point, and the PC/ABS flow performance itself is very poor, which makes it difficult to fill the cavity during the injection molding process.
(2) The temperature of the material tube is too low, making it difficult for plastic to inject into the cavity.
(3) The mold temperature is too low, and the mold temperature is too low will also make it difficult for the plastic to fill.
(4) When debugging the process, the first thing is that the injection position is not grasped correctly and the speed setting is incorrect, which will lead to snake patterns on the surface of the product.
So how do we solve these problems?
(1) Add glue injection points or improve the glue method, especially the horn glue injection is the least substitute glue injection method, and it is better to use a fan-shaped glue injection.
(2) Increase the temperature of the material pipe and add the temperature to the situation where the product quality problems do not affect the product and does not cause decomposition of the plastic. Under normal circumstances, 270°C-290°C is the basic one.
(3) The mold temperature is too low. Without affecting the product shrinkage, try to increase the mold temperature to 100°C-120°C, so as to facilitate the plastic flow and injection into the mold cavity quickly during the injection process.
(4) When we debug the process, we must first grasp the position of the injection. Method 1: For example, the position of my storage volume is 80MM. Then the preset value of the first section of the injection is 65MM,
Method 2: We also control the position of the injection end point to maintain pressure at 65MM. First, the first mold is produced to see how much material the material head has, and then debug it. Remember, the position of the first section must be controlled at the position where the glue gate in the material head is just at the point where the product comes into contact with the gate. The speed is controlled between 20 and 25 and the pressure is controlled between 90 and 100 MAP. Note that the speed and pressure in the first section cannot be too high or too fast.
Method 3: Then, between the position of the second section and the position of the first section where the position of the first section is 3MM-9MM, the speed is controlled between 5 and 9. The pressure cannot be too high, and the pressure should be controlled between 80 and 90 as much as possible. Too much pressure will cause air patterns to appear and snake patterns to not be eliminated.
Method 4: Back pressure adjustment is generally controlled between 8 and 10MAP, but here the first thing is to control the loose and retreat position. If the temperature of your injection nozzle is too low, the back pressure is too large, and the loose and retreat position is relatively small, it will cause cold material to be injected into the cavity, which will lead to the appearance of snake patterns, so try not to inject cold material into the mold.
Method 5: Then switch the position of the third section and the pressure holding position, and appropriately control it to the product to reach 90%. For example, the position can be controlled at 25MM to switch to the fourth section until the product is full.
Remember that the speed of the third and fourth sections must be fast, try to control it at high speed and inject plastic into the cavity under high pressure. The general speed is controlled between 95 and 99 and the pressure is between 120MPA. Finally, see if the product still has snake patterns. If there is no more, then first produce between 5 and 10 molds to see if there is any change. If there is no change, the time and speed pressure will be maintained.
In short, everything is relative, not absolute, everything has a solution. It is difficult to code. Please like me, masters, please pay attention to Bochuang Talk about Management. Your likes and attention will make me more confident to better provide you with solutions to injection molding technical problems. Thank you.
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