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Model 20A Frequently Asked Questions



Where can I get a custom made mold?


Contact   WWW.BENCHTOPMOLDS.COM  

Contact   WWW.HOBBYMOLDS.COM  



Do I have to purge the machine before turning it off?


No, purging is not required.   The machine can be turned off with plastic material still in the barrel.   The plastic material in the barrel will re-melt when the machine is turned back on.

Purging can be helpful when switching to materials of different colors.   Purging with a natural color material will allow you to see when the previous material has been completely purged from the barrel, but is not required.



Can Polystyrene be injected with the machine?


Polystyrene has been tested and it can be successfully injected with this machine.   However, Polystyrene parts will be VERY difficult to remove from the mold.   Since all of our molds are aluminum, the mold will likely be damaged when trying to remove Polystyrene parts.   Therefore, we do NOT recommend injecting Polystyrene if you are using aluminum molds.



Why are Acrylic, Nylon, Polycarbonate and PVC materials listed as unsuitable?


The maximum temperature that this machine can operate at is 440 deg F.   Acrylic, Nylon, and Polycarbonate plastics typically require higher temperatures than 440 deg F. for injection.

PVC plastic can emit TOXIC vapors when heated and PVC can corrode the metal parts of the machine.   Never use PVC plastic with this machine!



Can recycled plastics be used in this machine?


Yes! Rejected parts can be cut into small pieces and placed back into the barrel.   Also, clean recycled LDPE or HDPE bottles can be cut into small strips and used in this machine.



I set the recommended temperature, but the material is difficult to inject.


Every thermoplastic polymer has a Melt Flow Index (MFI) value.   The MFI is a measure of how easily the material will flow when melted.   Plastic pellets with a high MFI value will be easier to inject than the same type of pellets with a low MFI value.  

Also, the recommended temperatures for a polymer should be used only as a starting point.   If the material does not melt and flow, then gradually increase the temperature setting in 5 to 10 degree increments until you get satisfactory results.   But never attempt to set temperatures above 440 deg. F. on this machine.   Note: the temperature is TOO HIGH if the material from the nozzle is discolored, emits fumes or contains gas bubbles.



What is the best way to pre-heat the molds?


A simple, economical & repeatable way to pre-heat the mold is to use a hot plate with adjustable temperature settings (see photo below).   Using protective gloves, place the mold flat on the hot plate for a fixed time or use a thermometer to determine a more precise pre-heat temperature.   Alternatively, a hair dryer or hot air gun can be used to pre-heat the mold by blowing hot air onto it.



Hotplate heater for plastic injection molds


What happens if I add a mix of different color pellets?


The colors do not mix uniformly. (see photo below).   Instead, they create beautiful rendomly swirled patterns!



Swirled plastic colors in injection molds