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What Are The Limitations of RepRap?

Posted by Anonymous User 
Anonymous User
What Are The Limitations of RepRap?
May 25, 2008 04:27AM
I've been reading up on RepRap for the past few days and I'm excited about building one. However, I have not been able to find any description of the its limitations. I did find where the road map mentions that Darwin 1.0 is not able to print overhangs of greater that 45 degrees. I assume this makes it impossible to print things like spheres, bowls, and other parabolic surfaces.

In addition, many of the objects I've seen pictures of have rough sides/edges. So, I imagine it would be difficult to print interlocking pieces that fit snuggly. For instance, a syringe would probably require printing an oversized plunger and some post-printing sanding to make it all work.

I'm imagining all sorts of things I'd like to fab, and I could use some guidelines to help keep myself in check smiling smiley
Re: What Are The Limitations of RepRap?
May 25, 2008 06:57AM
"It depends"

winking smiley

For constructing spheres and things, you could always fabricate two (or more) parts separately, and then stick them together at the end, though this isn't ideal.

The rough edges is more an artefact of an 'unpolished' toolchain. If your design program exports models with large facets on curved surfaces, the product is going to share those facets even if your CAM and driver software/firmware is perfect.

Poor rendering of curves or non-axis-aligned straight lines is at least partially a software problem. In theory, a reprap should be able to make very high quality smooth curves *in the XY plane*. Better driver software and hardware will make this a reality... this isn't an unsolvable problem. Having smooth vertical curves is much trickier, due to the way that objects must be layered and printed; this may be far harder to resolve and maybe even impossible.

Lastly, it may always be possible to increase the resolution of the fabricator, with a finer filament and smaller XYZ steps. This presents many more problems however, requiring a much higher precision cartesian robot, and inevitably lengthened build times.

Quite often however, these things should not matter too much.

Considering syringes... you could have a square section one, perhaps winking smiley Also remember than in syringes the important bit is going to be a silicone gasket to form a seal betweem the barrel and plunger, and given its squishy nature a less than perfect barrel isn't necessarily going to leak.

As for interlocking components, that I'm less sure of. But recent output from nophead's machine is impressively high quality.

Lastly, we only have the one toolhead right now. Support material extruder will vastly extend the range of things a reprap can make. And there's nothing to stop you sticking a milling head on too, given a strong enough frame. Given time, all things will be possible winking smiley
Re: What Are The Limitations of RepRap?
May 28, 2008 05:17PM
The rough edges thing is relative. At the time of this posting some of Nopheads printed Darwin bits were on the front page and he has very nice prints. Also, note his print of Adrian's door handle. Very nice surface as these things go. Just depends on your machine. My prints are in the middle-lands as far as quality goes. Not Nophead quality but not stringy blobs with massive discrepancies either.

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