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help producing delta robot prototype

Posted by Lawrence Kincheloe 
help producing delta robot prototype
March 07, 2010 04:08PM
I'm having difficulties using the geeksok web forum so I would ask if someone is willing to help print off a test piece for the delta robot design I'm doing.

I've about got the final g-code finished, but I'm in need of someone to print it off. Its highly experimental so I expect it to have problems.

Re: help producing delta robot prototype
March 07, 2010 06:03PM
Can you give some more details, like how big it is, how many you need?

Re: help producing delta robot prototype
March 07, 2010 06:30PM
The lower leg members are ~288.5mm long and ~19mm in diameter.
These are the longest piece.
I'm dividing it into four segments, so the segment length will be a little less than half the total length.

I'm currently breaking up the model into printable segments, although this is going to be a pain and a likely source of mistakes. Once that is finished, I should have g-code that any reprap can print.

The only thing ready to print are the injection couplings on thingiverse. [www.thingiverse.com] I'm using them to break up the legs into segments so I can print them. If the couplings are too weak then I'll have to come up with something else.
Re: help producing delta robot prototype
March 07, 2010 07:32PM
I would need an STL to print, not g-code. There is no such thing as g-code that any RepRap can print. It is machine and plastic specific.

If you post STL's somewhere I can tell you if I will be able to print them.

The easiest way to join ABS pieces is to weld them with pipe cement.

Re: help producing delta robot prototype
March 08, 2010 01:08AM
I've uploaded a stl test file on thingiverse. [www.thingiverse.com]

Its the 1_1 version one. Depending on what kind of machine your using, this model makes use of some small features so it might need to be scaled twice as large to be printable on a reasonably accurate reprap.

One of the goals of this coupling is to test with fastening two different incompatible materials, such as ABS and hdpe. I know they can be heat fused, but the goal of this coupling is to provide mechanical coupling as well as take advantage of chemically coupling if the solvent/adhesive is compatible.

What I would like to know is the pull strength, sheer strength, and torsional strength of two ABS couplings bonded by injecting an acetone ABS slurry into the fill holes. There are more detailed instructions on the thingiverse page.

The pipe cement would work. However, it might require deforming the point of contact. Because of this, I would also like to know how much deformation of the coupling is caused by any of the fastening techniques.

I would also like to know how an ABS and hdpe connector work, under similar conditions.

Worse case, the various solvents undermine the entire structure and there is unacceptable warping in the part. Also, the surface area isn't maximized so the bonds break easily and the planned mechanical linkages are too brittle.

Best case, the various solvents adhere to the walls and pull inward as they evaporate, pulling tightly against the solid plastic walls and providing a strong bond.
Re: help producing delta robot prototype
March 08, 2010 08:43AM
Lawrence I will make you an editor on the forum. That should take care of any problems.

Re: help producing delta robot prototype
March 15, 2010 10:22PM
If anyone is interested in helping prototype a plastic version of the delta robot, I have the stl files.

Otherwise, I've decided to pull the trigger on a Delta-strap design which is going to blow everything else out of the water, or so I hope. Once I get the parts in I'll start blogging it.
Re: help producing delta robot prototype
March 16, 2010 08:56AM
Well Lawrence, that sounds intriguing smiling smiley can you give us one or more sketches/blends/stl files to see?

How do you plan to move it? with servo's or with steppers?
Re: help producing delta robot prototype
March 16, 2010 07:01PM

This is the mock-up image for a delta-strap, I'm building.

Its using geared stepper motors, steel tube that is going to be welded, UHMWPE cup material, rare earth magnets, and soft steel ball bearings.

I'm shooting for a build envelope of 300mm x 300mm and I'm using leg lengths of
Manipulator arm = 288.4995667241113899555444997387mm

Base arm= 135.7645019878171246849621175241mm

I went for steel because I couldn't weld aluminum, and the motors I have came with a 63/64 inch mount slug which makes interfacing with a 1 inch inner diameter steel tube fitting convenient.
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