Print speed test

So I got my mpcnc up and running, not complete, but running. I need to penetrate the zinc coating for a smoother pass. So I figured I’d get some large prints done and test out the print quality at the same time. I printed out some things at 30mm/s at first then I made it up to 50 before I really started to see any trade offs. but then I said, "hell, let’s push her to 70 just for laughs and see what kind of print we get. i mean obviously the thing is gonna turn out horrible…

I was working on a small remix of a part in tinkercad and figured I’d use it for a test.

It’s 250X50x50mm. so I can get my machine making some big movements. the problem was I had never printed anything this big before and soon realized that at the proper infill I’d have to wait over 30 hours for it to finish. so I dropped the infill to 15% and upped the shell thickness to 1.6mm for some symblance of strength. started off the print at 25mm/s for 2 layers and then cranked it up to 70. it said it would take 10 hours in cura, repetier said 8 1/2………it took 16 1/2 hours. oh well so I documented the “success” on YouTube ever couple hours or so. I’ll put the links down below.

So, how did it come out? well, it wasn’t as bad as I thought. I mean the thin infill barely stuck together. I had originally noticed back at 50mm/s that I had issues with corner turns becoming overextruded a little bit, well at 70 it gets overextruded at the turns alright, but it just keeps oozing all the way around the shell. basically the part is within the size it should be, but every hole is smaller because the walks are thicker. the pipe goes in okay, but the gap at the tension slot is too large. all of this I assumed would happen, it’s just good to see what it can do while also seeing what it can’t. surprisingly, outer shell layer adhesion was, satisfactory?…. But I watched the infill and I can tell you, shoddy at best. basically there is support there, but I don’t think it’s going to withstand any crush force. but all the holes printed nicely aside from the over extrusion, no stringing, no sagging. no z walk, only minimal peeling but that’s more related to the design and the “levelness” of my bed. all in all, the print was a major success, compared to the string cheese I imagined I would get. so I still give this one 4 stars. it’s nice to know that this thing can actually handle a little speed. i should also note that i do have the more rigid z add on.

More pics

Looks pretty good in the XY direction, I was curious as to what kind of speeds a MPCNC can print at. It has so much torque and rigidity since it’s meant mostly as a CNC but a ton of moving mass compared to most dedicated printers, moving motors on all axis. I wonder if you could mount the motors on modified corner blocks like a H-bot or CoreXY without compromising the CNC aspect of the machine.

Pretty nasty Z-ribbing though, possibly due to the US standard screw on the Z-axis? I know that can cause problems with printers. Though Vicious gets nice prints out of his, so it must be solvable. Maybe you need to set layer heights in US increments?

Pretty sure the “ribbing” is because of the vibration of the zinc coating being ripped off the machine coupled with the fact that my layer height is 27.52 and I’m trying to push the machine faster than it was intended to go