Nophead's CAPA thread revisited...

Sorry nophead. I was trying to post to your CAPA thread when apparently somebody working on the Forums did an upgrade that blew me off the air and trashed your thread.

Recapitulating, I know of nowhere in the UK where you can buy 3 mm CAPA filament. Jim Waring, who owns New Image Plastics in Ohio will make up consignments for you if you ship him the resin. He's done it before for us and has the settings on his filament extruder to do it again.

The problem with that is that CAPA is sold in 20 kg bags. The cost of the filament, the processing and shipping will mean that doing a bag will set you back about US$600 by my estimates. That's roughly $32/kg. You also have to go through all the drama of buying and shipping raw resin.

I saw this bottleneck some months ago and decided to see if I could use off-the-shelf 3 mm filament in several of the plastics that Jim keeps stock for. So far HDPE has worked fairly well in a modified Mk 2 extruder with a 2 amp barrel. I made the traditional shot glass out of HDPE yesterday and will be trying to make replacement parts for my Mk 1 AEM extruder that I cobbled together out of a kit of ABS Mk 2 parts that Adrian was kind enough to print out for me early last year. I'm pretty sure that HDPE is going to work all right.

I've also tested homopolypropylene (HPP) and ABS. I think that my current extruder design will handle HPP, but I think that ABS is going to need a more powerful gearmotor to run the polymer pump than the Mk 2 or the Mk 1 AEM has on board at this time.

Again, sorry that I accidently evaporated your thread. I hope this helps.

Edited 1 time(s). Last edit at 04/15/2007 05:09PM by Forrest Higgs.

Thanks Forrest,
I can get HDPE filament easy enough so I will go with that. I will probably do some home rolled PolyMorph tests first as I can re use it after it has been extruded, something I can not do with HDPE yet.

Ultimately I would like to recycle the free supply of HDPE milk bottles that are coming my way since I mentioned the project to my family. One thing that worries me a bit is that I understand that white plastic chopping boards are made of HDPE. Having just cut some meat on one I noticed it is quite flexible, despite being 10 mm thick. In comparison the PolyMorph I have played with seems a lot harder and less transluscent, more like nylon. Perhaps the chopping board is not pure HDPE.

In your experience would you say HDPE is softer or have I just got a cheap board?

i would say that HDPE is stronger than CAPA. i dont have any hard evidence, but i do tend to chew on the ends of filament. from my experiment the HDPE is quite a bit tougher.

Turns out that the white plastic chopping boards 10mm thick from IKEA seem to be PP not HDPE. I used this flowchart to identify the plastic: [www.texloc.com].

I bought some grey ones 5mm thick from ASDA (UK subsid of Walmart) and they do appear to be HDPE. They are much tougher.

Edited 1 time(s). Last edit at 12/13/2007 04:58PM by nophead.

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[www.hydraraptor.blogspot.com]

Hi Nophead

Adrian has done a 100kg purchase of CAPA should be arriving in the next few days, we will then convert 50kg to filament, on 2kg rolls expect to be about

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Ian
[www.bitsfrombytes.com]

I look forward to trying some CAPA.

Extruding HDPE onto chopping board looks quite promising. It gives the least warping I have achieved so far and you can remove it with a penknife and reuse the board.

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[www.hydraraptor.blogspot.com]