MP3DP V4 build PLOG

I just bought a spool of TPU which I want to use for feet. I have never attempted to print a flexible filament before, hopefully the Hemera lives up to its promise of good filament control and I don’t have excessive trouble.

/* sidetrack to project …

Meanwhile, I’ve been quite distracted with a retro arcade project. Two of them, really. One to replace the existing system, and one to be able to deal with alternate controls. I think that one will need a modular control panel. I still want regular arcade joysticks, but also want a trackball, which the old panel does not have room for. Then there is the GRS flight yoke that I got specifically for Star Wars arcade. I think I can manage with 2 panels, or maybe the flight yoke can be an add-on… I am starting to think of this one as a full sized cabinet, with a relatively large display. I want a 4 player cabinet, but can’t seem to draft up a cabinet less than 3’ wide. Maybe not a problem if I decide to use a 32" or 40" TV as a display.

Now returning to regularly scheduled PLOG */

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I tried TPU recently and had ZERO luck. I am not sure if it was the printer or me. History would point towards it being me. Let me know if you find success with the TPU, I’ll need to pick your brain on it…

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I have a spool of TPU but have been too scared to try it LOL


Apparently, when I fixed the fusion360 glitch with the bed support, I did it the wrong way. :man_facepalming:

Looks like I’d better take another go at it.

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I think I am going to print some TPU feet, but yours gave me some ideas!


That’s more like it!

So I corrected the sketch again, this time making sure to anchor the features to the Z motor mounts. Looks like my LR needs to be re-squared, the center hole is off by a little bit. I suppose that makes sense, I probably tweaked the Y stop switches when I installed the acrylic YZ plates. Must be off by a couple mm to affect the hole at 209mm.

Next I will cut some 12mm foam to make an insulating pad for the heated bed. I think that this part can be left as is, but I’ll probably re-cut it after squaring up the LR3 again, I’ll also make the mounting plate for the 24V PSU and the Duet 3 mainboard out of 1/4" ply.

Still deciding where all the wires will run to.

The Duet 3 has different motor plugs, they aren’t 2.54mm spaced, so I can’t just plug the motors into the board, I have to change the connectors. That was a bit of a surprise. This thing has some heavy duty current load possible, not that I need it for this printer, but it’s not wasted.

Makes me almost want to swap out for the motors that have the 6 pin JST connectors on them and make custom length cables… but not really.

I’ve been putting off trying to print with the TPU, but it’s time to bite the bullet and try it.

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In my original model it is not centered. The Hemera nozzle is not centered on the carriage so the bed is centered to the hemera not the frame. If that makes sense.

I felt the same way…I had zero issues. I think I adjusted the heat a bit but used my standard pla settings for speeds and stuff. Zero issues and prints great. I would say give it a shot and I doubt you will have issues.

I just uploaded some pictures here, Mp3dp v4 bom - #40 by vicious1, with some new wire routing. So far I am loving it.

Yeah, I see that the holes are off center, but where that hole is is off by a bit compared to the hole in the build plate, indicating that the CNC is out of square.

And… success with the TPU.


I tapped M5 threads into the bottom of the uprights and used a T nut as well. The feet make a nice addition to the frame.

I turned down the temp a bit, but still a lot of stringing with the print, so probably could be cooler yet.

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So I got really meticulous with squaring the LR3. It’s now easily within 1mm over a 600mm (well, 597, really) square.

I did up a CAD sketch with 4 parallel lines. The outer 2 are at the distance that my belts are apart, and the inner 2 are 597mm apart, and 597mm long.

I then join them with a line across the top 597mm long anchored to the top of the inner lines and one across the bottom anchored to one corner of the outside parallel line, and the bottom of the 2 inner lines. Note that while the top and bottom lines are parallel, they are not horizontal.

Define a dimension of the 2 inner lines corner to corner.

Cut the square with the CNC and measure the diagonals. The driven dimension of the free end of the bottom line to the base tells me how far to make the adjustment to the Y endstop.

Result, I cut a piece that is as close to square as I can measure. I only have mm markings on the tape, but estimate that it is less than 0.25mm out when measures corner to corner.

What has this to do with the printer?


So I figure that the extrusion will hold the plywood flat and the plywood will hold the extrusion square.

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Music to my ears!

So you are making the extrusions still, but skinning it in ply? I think you are on to something. Using them both makes for a best of both world’s situation…and gets rid of most of the corner braces.

Freaking genius!

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Nice! Look forward to seeing how turns out. What ply thickness?

I’m not doing all of the faces, the top and bottom will remain open, very probably the front, though that remains to be determined. I may just do the lower part on the front below the cross bar.

It’s not a new idea, the Railcore was designed this way, using 1515 extrusion and a skin surface to make the structure more rigid. I don’t remember what material the Railcore was originally specced with, but the idea was the same, like a torsion box, using the skin to reinforce the structure and keep it from deforming.

With just the back plate though the whole frame feels more solid, and the back is like a granite slab. This is with 5.5mm plywood, but I’m pretty sure it would be amazing in 1/8" acrylic, as well.

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Looks good. Do you have any acrylic?

I actually knew the founders of Park Tools 100 years ago!

Great folks, buy more!

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Next trick is the sides. Trying to visualize how I want these to run.

The wires for the alpha/beta motors need to get past the uprights for the Z motors, so I’m thinking a pocket that passes by the pillar to keep them inside the outer skin, but outside the extrusion to keep the wire clear of the Z linear rail. Put it 30-40mm below the top, maybe 50mm wide and 10mm high, 3mm deep. Should be enough room for the motor wires and Y end stop wire that way.

Given the way that the Duet 3 is set up, all 6 motor wires need extensions, or at least new plugs for the board. I’ve got a bit of decision paralysis with this one. Cut the wires and splice in extensions, or put male dupont connectors on extension harnesses… both have merits, and drawbacks. Well, if the main drawback is that I can’t change mainboards, I suppose cut and splice isn’t too bad a choice, but I hate wasting wire, so that means that I need to have all of the wiring figured out before I start with the extensions. Bleah. :face_vomiting:

I also appear to be put of 22AWG wire for the homing switches. More coming from Amazon, but it is yet another delay.

Anyway, next step seems to be figuring out what features I need for the side panels. I put those handles on the Repeat, and used them pretty much once. :rofl: I thought I’d be moving the printer from time to time, but basically I never do.

A camera mount seems like a good idea…

I have a bunch of 10x10 drag chain left over, but no ends. I figure it could be useful for the Z motors, maybe I’ll print up some mounts to connect it to the motors and the Z uprights. Wire sleeve is probably good enough, but I have it and drag chain will 100% guarantee that the wire doesn’t get in the way or get snagged. Same I guess for the heated bed wiring, but it can go in the same drag chain as the 3rd Z motor.

Anyway, these are the ideas I have now. I’m sure things will change.

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Is there a cheaper alternative to the Duet 3?

I run the XY (AB) stepper wires above the Z belt tension block, over the rail on the inside. I thought about making a more elegant screw in piece but, you know me, zip tie if needed.

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I thought as much, but if I’m skinning the box, the pocket seems to make more sense, less that can possibly go wrong. A zip tie slot on the Z belt holder might be a good addition for those who aren’t skinning the frame.

Well, there are the Chinese clones, the genuine ones are pretty spendy, but the 2oz copper is nice. I also like to support the developers when I can. My Duet 3 doesn’t have wifi, just wired network. Mine is also a revision behind current.

The SKR Pro also runs the RRF firmware, just needs an ESP add on, about $10 to add the wifi and DWC. I have a set installed, but haven’t configured it. It’s probably the cheapest ticket to the RRF field with 6 motor drivers.

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Need more plywood…


I cut this piece, you can see the pocket for passing through the motor and end stop wires, and a set of holes for zipties to secure them. I didn’t put any handles on this printer so the side is smooth. The holes for the front and back uprights are 3mm, the rest are 5mm, because that’s the hardware I have left.

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