Wednesday, March 04, 2009


Plastic supply


I am new to builders, but I have been following the Reprap builders blog for some time.

One problem I see is sourcing the plastic, but an idea I had was to use plastic pop bottles (PET), which could be cut into a ribbon and formed into a reel by heating the ends and compressing them together. This would mean a change in the design of the printing head. but may actually make the extrusion of the plastic easier.

This would be easier for people running one of these machines as a hobby and recycle plastics.
The plastic could be cut in a spiral from the bottles maximising the length the ends could be joined in a small press that had been heated, so that a long reel of the plastic could be made.

I sent this idea to Adrian Bowyer and he suggested that I post this on the blog. He aslo suggested that the ribbon could be folded over in width in the extruded to increase the thickness of the ribbon prior to going into the heating element section.

I am currently building a CNC miller / drilling machine to be used for making small components and cutting out foam patterns for castings, but intend to fit a Reprap head to it to convert it to a Repstrap machine. Again this is to make small components but also to make patters from casting in finer detail than achievable with lost foam technique.

I am a long way off trying my suggestion because I am still building the machine, but will try it as soon as I can.



Welcome to our community!

No criticism implied but; this might have been better posted to the forum area for materials, rather then the builder’s blog which I think sees fewer eyes on it.

While there are no hard or fast rules and this group is sort chaos in action. The builders blog area IMHO for something you are actively focused on or for posting progress, successes, progress or failures.

But again; hey welcome!

The extruder is speed bump in the road for a lot of people, which would be further complicated by a non-standard/virgin feed material.

Are you running a standard CNC electronics/tool chain or going to also use RepRep style electronics?
I really like the idea. I'm not sure, but I watch the blogs more frequently nowadays. The forums are often a bit of an information overload if you want to follow everything. Some people manage to do that, but I simply don't have the time.

Anyway. Recycling would be something I'd be interested in too. If we find a good practice for this and show people that it can be done, we wil reduce waste, reduce dependence on externally sourced materials and another great advantage is that we will be printing for free! PET seems like a hard and sturdy material. Your feeding mechanism certainly seems viable. If I get around to it I might also try this and blog the results.

My RepRap blog
One of the problems I see for this is that PET drinks bottles, in particular, at least here in .nl, are generally operated with a refund system, that is if you bring them back to be reused you get your quarter back -- so they're not waste, per se.

The other problem is cleaning the bottles before reuse -- you don't want everything you make to smell of cola, preferably.

This is slightly in the bikeshedding area, though. As a general idea, I really like it.
This is a really cool idea.

I think it'd be pretty easy to modify the new pinch-wheel extruder (see here: to run drink bottle strips.

Now we need to design a reprappable device to cut drink bottles into uniform-width helical strips...
2 razor blade mounted on a board a few millimeters apart would cut the spiral strip from the bottle at a width which, if double or triple layered would form a nice narrow square ribbon which could probably then be fed directly into the current pinch wheel extruder. It would be easy to make a mount that holds a standard bottle with the 2 razor blades at the bottom. A bottle cap with a rod or bolt ran through it to a nylon bushing would make it easy to turn the bottle.
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