Information About ABS Injection molding (Moulding)
ABS is generally called acrylonitrile-butadiene-styrene which is copolymerized by acrylonitrile – butadiene – styrene monomer. Due to the different proportions of these three monomers, it may have different properties and melting temperature. If ABS with the flow property blends with other plastics or additives, it may be extended to different uses and performance of ABS, such as an impact-resistance lever, heat-resistance grade, flame retardant, transparent level, reinforced grade, electroplating grade and so on. The fluidity of ABS is between PS and PC, which has relations with the injection temperature and pressure, and a slightly larger influence is the injection temperature. Therefore, when molding, it often uses higher injection pressure to reduce the melt viscosity and to improve filling properties.
1. Plastic processing
ABS’s water absorption rate is about 0.2% -0.8%.For the general level of ABS, it should use the oven at 80-85 Celsius degree for baking 2-4 hours or the drying hopper at 80 Celsius degree for baking1-2 hours before the processing. For the heat-resistance grade of ABS with PC components, drying temperature should be appropriately increased to 100 Celsius degree, concrete drying time is determined by the air extrusion. Use of recycled materials ratio cannot exceed 30%, the plating grade ABS cannot use recycled materials.
2. Selection of Injection molding machine
To make ABS injection molding parts, You can choose the standard injection moulding machine (depth-diameter aspect ratio of 20:1, the compression ratio exceeds 2, the injection pressure exceeds 1500bar). If use masterbatch or require higher products’ appearance, you can choose a small diameter screw. The clamping force follows 4700-6200t/m2 to determine, specific needs depend on plastic grades and products requirements.
3. Mold and gate design
For ABS injection mold, The temperature of mold can be set at 40-65 Celsius degree. Runner diameter is 6-8mm. Gate width is 3mm, the thickness is the same as the products, the gate length should less than 1mm. Vent width is 4-6mm, the thickness is 0.025-0.05mm.
4. Melt temperature
ABS material is one of the easiest molding material. You can use air injection method to determine accurately. Levels are different; the melt temperatures are also different. Suggestion below:
Impact-resistance level: 220 -260 Celsius degree, the best is 250 Celsius degree.
Electroplating grade: 250-275 Celsius degree, the best is 270 Celsius degree. Heat-resistance grade: 240 -280 Celsius degree, the best is 265 -270 Celsius degree. flame retardant: 200 -240 Celsius degree, the best is 220 -230 Celsius degree.
Transparent level: 230 -260 Celsius degree, the best is 245 Celsius degree.
Reinforcedgrade: 230-270 Celsius degree
For the higher requirement of products’ appearance, it can use higher melt and mould temperature.
5. Injection speed
Fireproof grade needs slowness, heatproof grade needs quickness. If the appearance of products requires higher, it should use injection molding control with high speed and multi-stage.
6. Packing
Under normal circumstances, it’s better with lower pressure packing, packing pressure commonly is 5bar, The coloring matters need to use higher pressure packing to make the mixing color uniform.
7. Dwell time
To make ABS injection moulding parts, the barrel temperature is important, at the 265 Celsius degree, ABS cannot stay in the melt barrel within the maximum of 5-6minutes. Retardant time is shorter, if need downtime, you should first set the temperature as low as 100 Celsius degree, and then use general-purpose ABS to clean the melt barrel. The mixture after cleaning up should be placed in cold water to prevent further decomposition, if need a switch from other plastics to ABS material, you should firstly use PS, PMMA or PE to clean the melt barrel. Some ABS products are OK at the beginning of the ejection of the part, however, after a period of time, they will be discolored, which may be caused by overheat or plastic in the long residence time of molten plastic tube.
8. Post-treatment of the article
Generally, ABS injection molded products don’t need the post-treatment, only plating grade products need baked(70-80 Celsius degree, 2-4 hours) to passivate the traces of surface. And the products which need plating don’t use mold discharging agent, products need immediate package after taken out.
9. Special notes on molding
There are several levels of ABS (especially the flame retardant level) and their melt have large adhesion on the surface of the screw after the plasticizing. Therefore, it will break down after a longtime. When above-mentioned condition happens, you need crew homogenization segment and compressing pulled out to smear and use PS and others to clean up the screw regularly.
Contact us if you are looking for ABS injection molding or any other customer injection molding service, HAO YUAN XING MOLD offers the custom molds and molded parts to worldwide.
