ABS, commonly known as acrylonitrile butadiene styrene, is made by copolymerization of acrylonitrile butadiene styrene. Due to the different proportions of the three monomers, ABS with different properties and melting temperature can be expanded to ABS with different uses and properties, such as impact grade, heat resistance grade, flame retardant grade, transparent grade, reinforced grade, electroplating grade, etc., if it is blended with other plastics or additives.
The fluidity of ABS is between PS and PC. the fluidity of ABS is related to injection temperature and pressure. The influence of injection pressure is slightly greater. Therefore, higher injection pressure is often used to reduce melt viscosity and improve filling performance.
1. Treatment of plastics
The water absorption rate of ABS is about 0.2% – 0.8%. For general grade ABS, bake in oven at 80-85 ℃ for 2-4 hours or in drying hopper at 80 ℃ for 1-2 hours before processing. For heat-resistant ABS with PC component, the drying temperature should be adjusted to 100 ℃, and the specific drying time can be determined by extrusion. The proportion of recycled materials should not exceed 30%, and the recycled materials should not be used for electroplating ABS.
2. Selection of injection molding machine
The standard injection molding machine of Ramada can be selected (the length diameter ratio of screw is 20:1, the compression ratio is greater than 2, and the injection pressure is greater than 1500bar). If the color masterbatch is used or the appearance of the product is high, the screw with a smaller diameter can be selected. The clamping force is determined according to 4700-6200t / m2, which depends on the plastic grade and product requirements.
3. Mold and gate design
Mold temperature can be set at 60-65 ℃. The channel diameter is 6-8mm. The gate width is about 3 mm, the thickness is the same as the product, and the gate length is less than 1 mm. The exhaust hole is 4-6mm wide and 0.025-0.05mm thick.
4. Melt temperature
It can be accurately determined by air injection. According to different grades, the melt temperature is also different. It is suggested to set as follows:
Impact grade: 220 ℃ – 260 ℃, 250 ℃ is better
Electroplating grade: 250 ℃ – 275 ℃, 270 ℃ is better
Heat resistant grade: 240 ℃ – 280 ℃, 265 ℃ – 270 ℃
Flame retardant grade: 200 ℃ – 240 ℃, 220 ℃ – 230 ℃ is better
Transparent grade: 230 ℃ – 260 ℃, 245 ℃ is better
Glass fiber reinforced grade: 230 ℃ – 270 ℃
For products with high surface requirements, higher melt temperature and mold temperature are used.
5. Injection rate
The fire grade should use slow speed, and the heat grade should use fast speed. If the surface requirement of the product is high, the shooting speed of high-speed and multi-stage injection should be controlled.
6. Back pressure
In general, the lower the back pressure is, the better. The commonly used back pressure is 5bar. The dyeing material needs higher back pressure to make the color mixing uniform.
7. Residence time
At 265 ℃, the residence time of ABS in the melt can not exceed 5-6 minutes at most. The flame retardant time is shorter. If the machine needs to be stopped, the set temperature should be lowered to 100 ℃ first, and then the general-purpose ABS can be used to clean the glue cartridge. The cleaned mixture should be put into cold water to prevent further decomposition. If you need to change from other plastics to ABS material, you need to use PS, PMMA or PE to clean the glue cartridge. Some ABS products have no problem when they are just demoulded, and they will change color after a period of time, which may be caused by overheating or too long residence time of the plastic in the melt cartridge.
8. Post treatment of products
General ABS products do not need post-treatment, only electroplating grade products need to be baked (70-80 ℃, 2-4 hours) to passivate the surface traces, and the products that need to be electroplated can not use mold release agent, and the products should be packed immediately after they are taken out.
9. Matters needing special attention during molding
There are several grades of ABS (especially flame retardant grade). After plasticization, the adhesive force of the melt on the screw surface is very large, and it will decompose after a long time. When the above situation occurs, it is necessary to pull the homogenizing section and compression screw out for wiping test, and regularly clean the screw with PS, etc.
About JasonMould Industrial Company Limited
Jasonmould is a China mold maker of plastic molds- injection mold, die casting moulds, plastic blow molding, rotational molding, medical plastic injection molding, two shot plastic injection molding, insert molding, overmolding, metal injection molding, micro injection molding, powder injection molding, ceramic injection molding, liquid injection molding, husky injection molding, household mold, casting mold, die mold tool, custom molds, china moulds, rapid prototyping tooling, plastic prototyping tooling, punch press tooling, die and tooling for mobile/ cell phone parts, automotive parts, vacuum cleaners, rechargeable tools, telephones, copiers, computers, multimedia speakers, and many other electronic products and household appliances. And also a plastic product manufacturer, mold manufacturer China– plastic parts, plastic water tank, plastic balls, plastic containers, plastic buckle, plastic anchor, plastic hanger, plastic spoon, plastic pipe fitting, plastic tumble, plastic tableware, plastic cups, plastic bottles, plastic tray, plastic cosmetic container, plastic case, plastic food container, plastic chairs, plastic caps, plastic cap closure, plastic tubes, plastic water pipes, plastic knobs, plastic tubing, plastic utility boxes, plastic racks and so on.
Person: James Yuan
Company: JasonMould Industrial Company Limited
Add: LongGang Village,LongXi Town,BoLuo County,HuiZhou City,GuangDong Province, China
Email: [email protected]