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Revision as of 08:43, 2 February 2012 by Whosawhatsis (talk | contribs)
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I am currently building this model and will release some build instructions and directions on how to correctly cut the rods to get the dimensions you would like.

Jan 31- Second build night. Parts printed- 1 base, 1 Y idler, 1 set of 4 feet, 1 set of 4 bearing idlers, 1 x carriage, 1 x motor end and 1 x idler end.


Base- Bug: The base wasn't tall enough for my NEMA 17 motors and was a bit loose in the mounts. Fix: Measured the NEMA 17 motors and adjusted the openscad file to fit. 50mm base height, 43.5 motor casing.

Y Idler- Bug: I only have 608 bearings on hand as do most Prusa builders. The idler was designed for 623 bearings. Fix: Measured the GT2 pulleys I will be using at 26.2mm and the 608 bearings at 22mm OD. An idler that fits would need to have a hole spacing of 48.20mm with 8mm holes. I'm not sure if this will get in the way of the current threaded rod spacing joining the two bases together.

Feet- Bug: None really. I printed them at M6 settings and they won't fit my design. Fix: Print at M8 and use threaded rods twice as long as the Y rods. This will basically out line the foot print of the machine, ensuring nothing is bumped by the bed.

Bearing Idlers-

Bug: They won't fit the 608 bearings I plan on using. Fix: I will see if I can adjust the scad file to scale them up. Or design my own.

X-Carriage Bug: The bearing fittings went in fine but were a task to remove. Also, the belt clamp system is a bit confusing. Fix: Adjust the file to loosen the bearing space by 0.25mm. Write up a belt mount instruction with photos.

X-Idler Bug: Again the bearings were incredibly tight. I couldn't even get one in. Next, the hex nut was loose. Fix: Loosen the bearing space, tighten the hex space.

That’s all for now.

The bearings slid right in for me with just enough friction to keep them from falling back out. If you have some Z wobble or your flow rate is a little too high, it may constrict the holes. Shaving a little plastic off of the edges at the ends of the channels may make it easier to get them in if the problem is just getting the end of the bearing in and the part will bend a bit to make it fit once you get it started. The X and Z bearing channels have slits in the sides to take up the slack. You can also push a screwdriver into that slit to force the sides apart a bit, thus widening the circle in order to get the bearing in more easily. Worst case scenario, you can add that .25mm fudge factor to the bearing size parameter before exporting the parts for printing. The channels are supposed to be tight, though, and I intentionally did not add these types of fudge factors in the code because the amount of fudging required, if any, is COMPLETELY different for different machines and gcode generator settings, and compensating for miscalibrations that make parts too tight on one machine will make them too loose on another. Drill or ream your parts after printing if necessary.
BTW, please sign and timestamp your posts on talk pages. You do this by ending with four tilde marks (~), and the wiki software will insert the proper information. There's also a button for it above the edit box. It comes out looking like this: --Whosawhatsis 18:43, 1 February 2012 (UTC)

I'm building this myself at the moment, here's my own feedback:

  • Feet: Personally I think these should be a bit thicker to make it easier to put felt strips on the bottom.
  • X Ends: I suggest allowing the bars to extend through the end pieces. The separation of the end pieces is already fixed based on the size of the print bed, so having to cut the length of the bars to fit adds an extra thing that can go wrong during construction i.e. cutting them too short or too long. The two bars that hold the base pieces together do just this, if you're in any doubt you can just cut them a bit longer than you think you need.
  • X carriage: the M4 holes are really close to the diagonals, a potential problem with poorly calibrated machines (or hand-cut pieces).
  • Y bearing retainers: the M3 holes on one side (the same side as the bearing loop) don't quite have enough free space for an M3 washer.

Other than that, great design! I struggled getting most of my linear bearings in place but that was mainly due to printing the pieces on a poorly calibrated machine. Nothing a dremel wasn't able to fix.

--Myndale 02:23, 2 February 2012 (UTC)

Feet: I could probably add a parameter for that.
X Ends: I had them that way at first, but it made them a lot weaker and allowed the tension of the X belt to bow the Z rods inward. I might experiment with it again now that the top is braced.
X Carriage: That part needs some work, and I'm thing of getting rid of the 45-degree-rule friendly angles and switching to something that takes advantage to the ability to bridge gaps.
Y bearing retainers: They're intended to be used without washers. I wanted to keep the inset for the head small to avoid compromising the integrity of the arch.
--Whosawhatsis 12:43, 2 February 2012 (UTC)