Finally got a crown. Used F-Egrave to generate gcode file. The GRBLcrown gcode I downloaded from the Milling Basics docs seems to be incomplete. So here it isā¦
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That is making some legitimate robot noises. My grandkids would LOVE it.
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How did I not realize the Y axis had ring and pinion? 
All of the parts being the same on all axis is pretty slick.
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Yeah, modularity was a goal. The original MPR&P had these linear stages but ultimately a different gantryā¦ and more unique parts. When @MakerJim and I started talking about āwhat if we put a LR4 beam and lift setup on the MPR&P Y-axis linear stagesāā¦ it actually simplified the gantry and made for fewer unique parts required.
It initially ātarnishedā the idea of R&P on all three axis (which was an original goal)ā¦ but I was never really happy with the R&P Z-axis on the original MPR&P anyway. I like the modularity of V2 betterā¦ even if the Z-axis is leadscrew driven. LR4ās beam and lift setup and reputation for rigidity swayed my thinking.
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Benchmarking with Jamieās rulersā¦
Larkbox Pro miniPC running Jamieās test pattern gcode in UGS and connected to inexpensive GRBL controller through USB. Y and Z motors are series-connected and itās all running on 12 voltsā¦
MPR&P-V2!
Printed rulers with commercial metal rulerā¦
Pretty pleased with the way this machine has come togetherā¦ Iām really starting to like it. I donāt know what a threshing machine sounds like but this surely must sound like oneā¦ and itās interesting to hear what sound each axis contributes to the mix.
Later.
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This. Me too.
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So impressive. Amazing.
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Right proper robot noises.
What a great refinement of the MPR&P.
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Looks like it is just about ready for publishing?
That is fantastic.
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Iām curious, at the seam between the rack segments, if there is any discernable anomaly in the ruler. Theoretically there could be print defects that affect the length at the butt joint but they might not manifest in your instance.
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Are you talking about putting it out on Printables? Thatās on the agenda for ā hopefully ā sometime today.
In that second ruler test video above, it looks like the 100mm mark stopped just short of a rack seam. I have all that set up stillā¦ should be able to move the origin slightly right and print another ruler that has to cross the rack seam. Should be able to do that today as wellā¦
Thanks, guys, for all the kind words, encouragement, and ideas for further testing.
This has truly been a fun project. Iām printing a tool plate right now and should be able to show a router mounted on it soonā¦ though Iāll not try to do any cutting today.
Later.
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Hereās a 100mm ruler plotted while running across a seam on the X-axis rackā¦
Shown here is the pinion about 8-9 teeth from the seam at the ruler start positionā¦ and a little over 5mm (actually 5.236 mm) between teeth.
Any seam-related anomaly should show up somewhere between 40 and 50mmā¦
See anything?
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Looks perfect to me. Anything about 0.1 mm or maybe 0.05 mm would show up for sure.
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Love that ruler test
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I do, too. Thank @jamiek for that!!!
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Iām calling it good for a first cut. I think this is pretty complete but is still obviously subject to changeā¦
Iāve omitted the bottom and side panels/boards/stiffeners since they are probably not gonna be printed and are cut to length to accommodate whatever the dimensions for desired footprint or work area. I suppose I could/should provide printable jigs to help locate holes relative to the ends of those panelsā¦ itās difficult to match-drill through wide plastic parts that are probably already bolted in place. Also, with the round spacers and holes through the end supports Iāve thrown in, the side plates could be extended all the way down to form a debris wall on any/all sides.
Please āholler upā if you see something Iāve missed or have questions.
I appreciate all the kind words, encouragement, comments, and ideas that have been sharedā¦ not only for this project but for the entire time Iāve been a part of this forum. You are a fun bunch of folks to be around and as Iāve said beforeā¦ this is āhomeā for me. Yāall are by far some of my finest friendsā¦ even though in most cases weāve never met face-to-face. Funny how that works! 
Have fun!
ā David
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First thanks for posting this, its really interesting. Couple of questions:
The files named āCarriage-V12 - Y-end_support-rightā and āleftā
- Are they also used for the ends of the X carriage?
- Theres a keyhole shaped cutout which from the picture looks like its for the Rack. Should there be a through hole?
- Are the tubes friction fit or is there some other retention. I see thereās a hex cut-out, are you threading the ends of the tubing for a giant nut?
- Whatās the other round cutout on the carriages for?
Thanks again for this - Iām printing a rack piece now.
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What would be the maximum build size?
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Yes, the same end-supports ā left and right ā are used on all linear stages.
The ākeyholeā was originally rectangular just like the other side to accept the ends of the rack and have a single symmetrical part that could be used on either end. That changed with V2. The round part of the recess was added so that the 1/4" nut (and washer?) can be fully recessed into the part and still be tightened to pull the end of the rack tightly into the rectangular recess on the other side using a socket. There is a 1/4" hole there but has a one-layer bridge to allow cleaner printing without supportā¦ most all holes on the printed parts will need to be finished/āreamedā with a drill bit, depending on how dialed in your printer is.
Print these parts with the rectangular recess upā¦
The hex recesses receive the ends of the conduit with a slip fit until it fully seats against the stop. Printed āhex holesā is a printing ātrickā that allows far easier precise fitting than trying to print precise āround holesāā¦ thereās less area of contact and a little āgiveā in the plastic to make allowance for different printers.
Print the rack sections on their sideā¦
Start assembly with the end supports, rack sections and threaded rod.
Draw the rack sections and end supports firmly together, setting the overall length of the axis. Carefully measure through the hex holes from end stop to end stop with a tape measureā¦ or maybe better, a dowel āstory stickā. Cut your 3/4" EMT rails as precisely as you can to that length.
Now you are ready to start printing and assembling the carriage.
Hope that helps.
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It does, thankyou.
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