Grinding the Plastic - TechforTrade/Thunderhead-Filament-Extruder GitHub Wiki

After many attempts at using low cost commercially available granulators, we have found that that we get much better results using our own bottle chopper. The downside is that our chopper is very tedious to operate. Comercially available granulators are typically designed to produce flake that will be made into pellets using large pellet extruders. These extruders are very different than our small scale filament extruder. Issues we have had with other granulators:

• The flake produced is too large.
• There are too many fines mixed in with the flake.
• Three phase power is often required for operation.
• Even the lowest cost equipment is too expensive.
• The granulator capacity is typically much greater than needed. Wasted capacity.
• Granulators used for other jobs are often contaminated with other plastics. They can take lots of time to clean.

For the Thunderhead extruder to work properly, the plastic needs to be cut into flakes that are around 6 mm in length and width. The flake should be as free of fines and dust as these will cause feed problems by clogging the grooves in the feed throat. Below is an image of clean and uniform flake produced by our bottle chopper:

If you are using a grinder other than the one we have built, here are a few tips that might help:

• If the flakes are too large, grind them twice, install a finer screen on the granulator, or both.
• Before grinding, clean the granulator thoroughly.
• Before drying the flake, remove any fines and oversize flakes by running the flake through a coarse then fine screen.