What can a reprap print?

From what I know of 3D printing, if I want to print a hollow part with protrusions from the body of the part (for example, printing a hollow letter "H"), the standart 3D printing machines uses a second polymer which is used for supporting the protrusion and is washed off after the part is done. Can a reprap machine cope with such parts?

Yes, but the answer gets complicated from there. The answer is machine specific. There are overhang tolerances, and if those must be succeeded: there are strategies to cope.

If you mean specifically: "can mendel print support material?"
-PLA is supposed to be an acetone soluble support material for ABS but this calls for a multi extruder print head.

Is the Mendel's official release capable of support material without modification?

No

Is such modification relatively straighforward?

Yes.

Has anyone done it yet?

Not that I know of.

Edited 1 time(s). Last edit at 05/12/2010 03:22PM by JohnnyCooper.

JohnnyCooper Wrote:
-------------------------------------------------------
> Yes, but the answer gets complicated from there.
> The answer is machine specific. There are overhang
> tolerances, and if those must be succeeded: there
> are strategies to cope.
>
> If you mean specifically: "can mendel print
> support material?"
> -PLA is supposed to be an acetone soluble support
> material for ABS but this calls for a multi
> extruder print head.
>
> Is the Mendel's official release capable of
> support material without modification?
>
> No
>
> Is such modification relatively straighforward?
>
> Yes.
>
> Has anyone done it yet?
>
> Not that I know of

Although I have been occasionally looking at 3d printers since 2008 I have just recently gotten involved with the reprap models. Look at the BFB 3000 at rapman.com. It looks like this printer is made with two heads so you can build with SST or soluble support technology. The process of using the supports is called FDM or Fused Deposition Modeling.

Check out this website for more info on how the 50k machines do it. Shouldn't be hard for a reprap model to be modified to do it.

[www.youtube.com]

The letter H is probably printable without support depending on the size of the bridge. On the other hand, the letter T cannot be printed without support since you cannot form a bridge to support the overhang.

Note that the support can be printed of the same material as the desired part. It works with ABS but I don't think it works well with PLA. The Skeinforge software that is most commonly used in Reprap printers support this feature. The UP! printer does this really well. They may have even pioneered this method, but I'm not sure. Anyway, this method is used a lot with mixed success. Here are some good examples: [www.thingiverse.com] and [www.flickr.com].

Acetone will dissolve both PLA and ABS so it can't be used to dissolve PLA support from ABS. Caustic sode can be used to dissolve PLA and leave ABS intact. I think Stratasys uses a method along this line.

Most of the firmware and hardware for the Reprap Mendel doesn't support a second extruder but there's probably a version floating around that does. The old Gen 3 electronics support additional extruder controllers but most fw doesn't support it anymore. There are a number of approaches that would work for adding more extruders to the Mendel. Some are in Thingiverse.

Most reprap printers use FDM. This refers to the method of printing by extruding molten plastic, not the process of using support.

Makerbot sells a filament made of PVA that can be dissolved in water and can be used as support. It's quite expensive and I haven't seen a lot of report in this forum on its use.

What does Stratasys use for support material anyway?

I know they use ABS as main material, and the support is able to be broken away...

The break away support material stratasys uses is HIPS (high impact polystyrene)

Reapraps only work with one material at the moment, and still require significant amounts of development in hardware and software before dual material types can be used for body/support.

The current same material break away support works alright, but there is usually a lot of tinkering required to make it work nicely for each model.

Well polystyrene is available as welding rods as far I know. And it is really easy to work with, it has a very sharp glass transition and doesn't require a lot of heat to melt. In fact is is the easiest material to weld from my experience.
Welding rods should also be very common and should be cheap, lets go for it.

Also there is quite a large potential to recycle Styrofoam, there a masses of this sort of waste...