What are the characteristics of plastic mold ABS injection molding process
ABS, commonly known as acrylonitrile butadiene styrene, is made by
copolymerizing three monomers of acrylonitrile-butadiene-styrene. Due to
the different ratios of the three monomers, they can have different
properties and melting temperatures. If ABS with fluidity is blended
with other plastics or additives, it can be expanded to ABS with
different uses and properties, such as impact resistance and heat
resistance. , Flame retardant, transparent, reinforced, electroplating,
etc.
The fluidity of ABS is between PS and PC, and its fluidity is related to
injection temperature and pressure. The influence of injection pressure
is slightly greater. Therefore, higher injection pressure is often used
in molding to reduce melt viscosity and increase mold filling.
performance.
1. Plastic processing
The water absorption rate of ABS is about 0.2%-0.8%. For general grade
ABS, use an oven to bake at 80-85°C for 2-4 hours or use a drying hopper
at 80°C for 1-2 hours before processing. For heat-resistant ABS
containing PC components, the drying temperature should be appropriately
increased to 100°C, and the specific drying time can be determined by
air extrusion. The use ratio of recycled materials cannot exceed 30%,
and electroplating grade ABS cannot use recycled materials.
2. Injection speed
Use slow speed for fireproof grade and fast speed for heat resistant
grade. If the surface requirements of the product are high, high-speed
and multi-stage injection rate control should be used.
3. Post-processing of products
Generally, ABS products do not need post-treatment, only electroplating
products need to be baked (70-80℃, 2-4 hours) to passivate the surface
traces, and the products that need electroplating cannot use mold
release agents, and the products should be packaged immediately after
being taken out. .
4. Retention time
At a temperature of 265°C, the retention time of ABS in the melt
cylinder cannot exceed 5-6 minutes at most. The flame-retardant time is
shorter. If the machine needs to be shut down, the set temperature
should be lowered to 100℃ first, and then the general-purpose ABS should
be used to clean the plastic melt cylinder. The cleaned mixture should
be put into cold water to prevent further decomposition. If you need to
change from other plastics to ABS, you must first use PS, PMMA or PE to
clean the melt cylinder. Some ABS products have no problems when they
are just demolded, and they will only change color after a period of
time. This may be caused by overheating or the plastic staying in the
melt cylinder for too long.