Holy cow, I absolutely love this. Bolts, printed bearings, moving 16lbs with ease!
I think you are fully onto something here. I do not want to sway any design decisions, you are a genius! I love this design so far.
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So true. This thing is great.
I started clearing off the MPR&P version 1 table in my garage to work on an upgrade when ready.
I wish there could avoid every horizontal surface in my garage getting buried in stuff.
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I resemble thisā¦
@dkj4linux your progress on this is amazing. Truly a work of affordable art!
One thing I found interesting when I was making threaded parts before my printer was tuned and it was overextruding a bit: PETG fit really tight, but once I ran the plastic threads a bit, it really became smooth. The part was a belt tensioner on an ender. I wonder if that might be useful for this threaded rod you print in place, notwithstanding the tradeoff with PETG vs PLA.
Me too unfortunately.
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Goodness! You guys are my heroes and youāre making me blushā¦ 
I must admit, it was the Z-axis on the original MPR&P that I was never really happy with. And seeing how the LR4 has such a great reputation for rigidity and power and a low COG with the Z-lift function split out to the ends of the gantryā¦ thatās what set the direction for this project. IIRC it was something @MakerJim and I mused about during the first buildā¦ what if we stacked a LR4 beam on a couple of MPR&P linear stages?
So, take 3 of theseā¦
and add 2 of theseā¦
and stack it up to look something like thisā¦
Iām having fun with itā¦
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Yeah, we kicked that around a fair bit.
Using three identical stage mechanisms makes the machine so modular.
Iām loving seeing you iterate on the design.
The stages could do other things, also. For example, one would make a great camera slider base.
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You are getting into the territory where a couple cheap injection molds could build this thing. The first MPCNC was only a couple parts I planned on injection molding (because 3D printing was still not all that great at the time).
I canāt keep my mouth shut. If that printed leadscrew and nut is working that smooth, think you can make the rails and rack one modular printed part? ?Take out the bearings and bolts and just have some sliding surfaces?
At this point you are at rails, steppers, controller, power supply, couple bolts and bearings.
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Are you talking about something like thisā¦ only scaled up for MPR&P?
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Maybe, that leadscrew seems smoother than I thought. Just wondering if a slide of some sort is feasible or best to just stick with the cheap emt and bearings
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The leadscrew is easily made in Onshapeā¦ and the one for MPR&P is a 2-start, 10mm per revolution, trapezoidal thread. Itās easy to change starts and pitch with helix and sweep opsā¦ with any thread profile.
I thought maybe the dovetail slides replacing the guide rods was what you were asking.
I can send you a link to the Onshape document for this if youād likeā¦
Are you talking about just the lift assembly? Or the linear stages?
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Yeah that might just work.
But then, RapRap has a long love for itās vitamins (mis)using bolts and printed bearings.
A print-in-place stage would be so rad, thoughā¦ Even if you print it in place and then crank it up and shove in some dowels or bolts.
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Iām not sure if you guys are just looking at the Z-lift assembly or, somehow, the whole machine. I been going on the assumption that the MPR&P linear stages are in pretty good shape, needing only minor tweaksā¦ and that the Z-lift setup is what Iām focusing on now. Where are all the ābearings and boltsā that could potentially be sliding surfacesā¦ other than in the Z-lift; i.e. like a scaled-up version of the little laser engraver Z-axis design from a few posts back?
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Thatās how I see it.
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Pretty sure this would be easily printable and last for at least a whileā¦
The previous guide rods now become simple fasteners to strengthen and hold the whole assembly together. The sliding carriage and leadscrew can be printed in place as before. The slider rails easily printed with no supports.
Still no idea of lube requirements. I really donāt think in this application they should be running dry. Iāve thought of petroleum jelly and white lithium greaseā¦ others?
Chime in if you have thoughts or ideas.
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Print in Nylon.
The bolts sound like a better idea to me. Sorry, Ryan 
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agreed
Cāmon guysā¦ Iām already printing some test parts for the all-printed version.
Wussies! 
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Youāre a machine prototyping machine!!!
Canāt wait to see how it plays out.
I had good luck with PLA-on-metal bearings, but never PLA-on-PLA.
Stiction or something.
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Thanks for the kind words.
Iāve done a number of plastic-on-plastic slides but always for slow and/or intermittent movement and light loadsā¦ as with laser engravers, where you most often set focus and then leave it there. Here is a note I wrote from one of those engraver Z-axis modelsā¦
An observation about printed sliding surfacesā¦ it helps if the mating surfaces are NOT printed at the same resolution and with layer lines running in the same direction.
To test I printed two sliding mechanismsā¦printed vertically-oriented, the set hardly slides at all without considerable force applied, printed horizontally-oriented, that set slides better but feels a bit āstickyāā¦ but mismatch either set and it is ājust rightā.
For the āthreadedā parts ā the leadscrew and carriage ā I felt both needed to be printed oriented vertically to insure their cross-section is as round as possible. In this case, I found that if I printed one at 0.3mm layer height and the other at 0.2mm to āmismatchā the layersā¦ I got smoother operating threads than if both were printed at the same resolution.
Iāll go ahead an build a all-plastic lift unit just to see what I can get away with. I still think a light layer of petroleum jelly or lithium grease might be is order as well. I always try to put that off until Iām done assembling/disassembling during testingā¦
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