Materials which can be used

Hi,

What materials can the RepRap use?

I've seen references to CAPA and HDPE.

Cheers
Joe

Vik uses PLA (polylactic acid)

we're working on getting ABS working, and Adrian has some designs for a support extruder which would extrude anything you can get in a paste form.

Cheers,

Just to confirm that the current list is,

CAPA
HDPE
ABS
[Anything in a paste form]

Which out of CAPA, HDPE and ABS is the best - dare I say - all purpose material?

Yup.

A quick overview of the pros/cons:

CAPA - expensive, low melting point, low shrinkage (few curling issues, easier to extrude)
PLA - expensiveish, hard to source, low shrinkage, stiff (see: offset extruder design)
HDPE - cheap, medium melting point, relatively large shrinkage (curling issues)
ABS - cheap, high melting point, basically untested with RepRap. the current extruder is not designed to handle this.

So, what's our "ideal" material, then? Something cheap with, say, the consistency of nylon at room temp, a melting point slightly above 100C and zero shrinkage?

yeah, i'd say we could even go up as high as 150C. to me, it seems that the shrinkage is the biggest technical hurdle, and price/availability is the biggest economic hurdle.

I am finding a melting point of 105C for ABS and 102C for PLA so HDPE is actually the highest melting point material as well as the most shrinkage.

Bruce Wattendorf seems to having success with ABS with an extruder largely to the current design. Why did we think we needed a new extruder for it?

I expect it is more viscous than HDPE but so is PLA. That just seems to require more pressure and a slightly bigger motor.

---

[www.hydraraptor.blogspot.com]

Someone could make another thread for this, and the math is complicated, but to prevent some of the curling, could we use an arced stage?

---

Jay

If you consider the simple case of a rectangular block then yes you could extrude it onto an arched stage. When you remove it it would curl upwards so you would have to make the top curved downwards by the appropriate amount. The head would have to move in 3d arcs to follow the curve all the way up the object. You may even need to lay down filament with a thickness that varies across it length.

Apart from being very complicated to calculate the shape of the base, I think it would vary from one shape to the next so you would have to form it from support material.

---

[www.hydraraptor.blogspot.com]

I have to use a little bit more clamp pressure it is a little bit harder then HDPE so I need more pressure on the clamp to bit into it better.

it does act differently at the 130 C.(kind of like toothpaste) range then at the 170 C range but it doesnt seem to stick to it's self at 130 C.
I have also noticed that it extrudes a smaller filament at 130 C then at 170C
but I know it works fine with the older extruder (direct drive not cable)

Bruce

Hey Guys I am interested in using PLA once I get a RepRap but one thing I am familiar with is growing crops. I was wondering where I could find out how to make PLA from crop to material. If you know of any places that would be grand or do I need to venture into this with no preset tutorial. If there isn't a place I could find out how to make PLA it would be greatly appreciated if you know of any chemist that could help me out.

-Rich

I think there is a previous thread on this issue in these forums. Dunno if a search will pop it up.
Bottom line is that it's not easy to synthesize, it's more of a factory process.

Check out this for a hunch: [en.wikipedia.org]