Sunday, November 6, 2011

"We can rebuild..."

"We have the technology... we can rebuild..."
It's more like "spot the difference" really, but regular followers will observe that the transition from wood to plastic has commenced. I've replaced my wooden x-axis components with newly printed plastic (PLA) ones. As I've become more fussy about print quality I've realised a little looseness here and there, and tiny wobbles in the z-rods were showing up as patterns in my printing. I've printed quite a few components for a complete new RepRap at this stage, but with the accuracy of some components now being impacted I chose to do an interim rework of my repstrap.

It's got a new x-end idler. This one http://www.thingiverse.com/image:63587, but instead of fitting real LM8UU linear bearings, I've fitted these printable PLA substitutes http://www.thingiverse.com/thing:12238. We'll see how that experiment goes!
Now, just to mix it up a bit I've put the more traditional x-end motor bracket, http://www.thingiverse.com/image:63177, on the far end, but I've modified it slightly. I'm only using one nut on the z threaded rods. Can't see the point of the second nut and the spring between them. I know it's an anti-backlash design, but I've had only one nut in my wooden design and gravity looks after backlash in the vertical direction. I've no plans to print in zero gravity. :-) Also I couldn't bring myself to use that overhanging motor design, so my motor stays inboard for a more balanced look.

 Final update worth a mention has been my move to printed z-rod couplers, the symmetric ones... http://www.thingiverse.com/thing:11220. I had a steel rod coupler, seen here, but was so rigid it exaggerated imperfections in the threaded rod, resulting in motor and x-axis wobble. The new arrangement is much more forgiving and visibly smoother as the x-axis assembly moves up and down.

I've retained my wooden z-motor brackets and vertexes(?). They are solid and accurate.
The x-carriage and extruder is now fully RepRap, and as you can see from the part on the bed, I'm printing a spooler!

But a key part of improving print quality has been a fresh examination and fine tuning of basics like squareness, perpendicular z-rods, frame triangle distances all equal. I've screwed the unit to a base board to increase rigidity also. Finally, the introduction of better belt-tensioning technique such as found on Gregs x-carriage, and this little unit (http://www.thingiverse.com/thing:10274) have been invaluable in removing print quality issues due to backlash. The use of these fine tuners allows belt tension to be adjusted a little at a time without over tightening, that might strain something else out of alignment.

Here's a quick look at two test pieces fresh off the newly rebuild rig. I'm pleased with the current print quality.


Now to make it go faster! :-)

Happy printing!


1 comment:

  1. Nice Job. It will be a shame to see the Oak go, I think it's really nice. That's some good upgrades mind, and your prints are looking great!

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