Granular extruder, good news and bad.

I did some testing this afternoon on the granular extruder I recently put together. Things didnt go so well..

The disassembled extruder after testing. Note the solder plug has been pushed out and some HDPE has flow back out the seal.

It turns out that the ‘high temperature’ solder I used to seal the end wasn’t up to the task. I first tried to extrude the HDPE at a lower temperature, around 140°C, but I wasn’t able to get it flower. Once I turned the temperature up a bit hight, around 180°C, it started to extrude quite well for 15 seconds or so until the solder melted. At this point molten plastic was extruded from every opening, ruining the barrel.

On the up side, I now know for sure that the auger drill bit can provide enough pressure to extrude successfully. However, at this point the rotating of the auger drill bit was still done by hand. My next attempt will be to try and braze on a flat section on the end end of the pipe with silver brazing rod. Silver brazing rod doesnt even begin to melt until well over 450°C so it should be well up to the task.

Also today, my good friend who supplied the original HDPE granules stopped by and dropped off a slightly bigger batch.

A 30kg box of HDPE granules.

This 30Kg box (66 pounds) of food grade HDPE granules is all the motivation I need to press on and find a workable way of extruding it. That is until my Mendel parts start to arrive and I get distracted by its construction.

About Richard

I am a Materials Engineering working in the field of Magnetic Materials in Melbourne, Australia. This blog covers my personal interest in all things CNC.
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2 Responses to Granular extruder, good news and bad.

  1. nophead says:

    HMP solder melts at 300C, it looks like you used ordinary leaded solder if it melted at 180C.

  2. Richard says:

    The solder I used was labeled ‘High temp’ written on a strip of masking tape.. So it was hardly a sure thing. I had a feeling from the start this may have been normal solder as it it seemed too easy to melt with the heat shrink gun.

    If I went and bought some true high temperature solder I may be able to use the same process to work. However having now dug out a propane torch and obtained some silver brazing rod off a friend I will give that a go.

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