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RepStrap project

Posted by rienafairefr 
RepStrap project
July 31, 2015 04:07AM
Hi all,
I'm starting into 3d printing, from scratch. I could buy a kit but I'd say what's the fun. I did robotics during my college years, using mostly salvaged parts so I'm not reeeally starting from scratch experience-wise. I salvaged some stuff going to the bin at work. Goal is to have a printer able to print some parts for a more advanced build afterwards. I have some questions to decide which drives and structure I can start and make from what I have.

-I got Aluminum smooth rods axes. They are 16 mm diameter. I'd go with plastic bushing, not ball bearings of course. I'd be afraid of static friction-induced "backlash" hysteresis, but if all lubrificated well I think it's OK?

- Freestanding rods? The rods are 55 cm long (can be cut ofc) They are tapped both ends and I can screw/nut them pretty tightly onto a 10 mm plate aluminum. Would wobble be a problem at these sizes? I'm not going to put a lot of mass up there, only an X axis with a gantry-style of printer. If it's out of the question I'd just add mdf to make a single plate prusa i3-like.

- Asymmetric delta? The rods and plates I got can be put into a delta-like position with plates on the bottom/top and three rods going up, but the triangle is not equal-sided, more like 25-27.3-27.3 cm. From what I briefly looked in the delta firmwares, I think it's hardcoded symmetric, but I'm not sure. I could just drill another set of holes (or slits, so I can correct misalignements). Add to that, a delta with a single rod, ain't gonna work
eye rolling smiley

I'll probably post pictures so you guys can better see what's going on.
Cheers
Re: RepStrap project
July 31, 2015 05:17AM
Quote
rienafairefr
- Asymmetric delta? The rods and plates I got can be put into a delta-like position with plates on the bottom/top and three rods going up, but the triangle is not equal-sided, more like 25-27.3-27.3 cm. From what I briefly looked in the delta firmwares, I think it's hardcoded symmetric, but I'm not sure. I could just drill another set of holes (or slits, so I can correct misalignements). Add to that, a delta with a single rod, ain't gonna work
eye rolling smiley

I believe most delta firmwares support asymmetric deltas internally (i.e. towers not in an equilateral triangle), but some make it easier to configure the asymmetry than others. The version of RepRapFirmware I just released allows the positions on the X and Y towers to be adjusted by small amounts in the config.g file, which would be sufficient for your purpose. You would still need to make the diagonal rods all the same length - I don't know of any delta firmwares that support different diagonal rod lengths.

You need two lightweight parallel rods from each tower to the effector, so as to constrain the tilt of the effector in 2 directions and also its rotation.


Delta printer calibration calculator, mini IR Z probe, and colour touch screen control panel: [escher3d.com]

Large delta printer, and other 3D printer blog postings: [miscsolutions.wordpress.com]

Disclosure: I have a financial interest in sales of the Panel Due, Mini IR height sensor, and Duet WiFi/Duet Ethernet [www.duet3d.com].
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