Hi all!
I’ve built my MPCNC Primo some months ago, everything works fine except for the truck clamp on every truck. These pieces broke off very easily after some times, even if I do not thighten them too much. Can it be some filament issue? I’ve printed them with Sunlu PLA+…now I’m trying to install some 2.1mm shim between the clamp and the truck, to see if they’ll last more…
Any advice?
Thank you!
Simone
Can you post some pictures of your build?
I’m assuming they are breaking off at the “knee?” If so, here is a version of that clamp with a fillet at the knee to improve strength. I also suggest printing this piece with extra perimeters. I’ve included a .STEP file without the edge fillets (to make it easier to change) in case you want to further modify the clamp. I modeled this piece up for a different mod of my Primo. That is, I’ve not had any problems with breakage, but I did print this piece with four perimeters.
TruckClamp.zip (45.9 KB)
Now the machine is working, after I clean all the mess I’ll post some photos 
Yes, it borkes at the knee… Today I’ve printed mine with 3 perimeter, 50% gyroid fillet… I’ll definetely try out your version! thank you very much!
I forgot to mention, this is the clamp for the 25.4mm (1") tubing. If you are using a tubing of a different size, let me know.
Thank you again! I’m using 25mm pipe, if you also have the file for that measure I’ll give them a try
I’m also using these to hold the Z axis cabla chain:
MPCNC Primo Drag Chain Support by Alfred | Download free STL model | Printables.com
I use that Support as well and it should not break, ever. 
Thank you very much! I’m printing it right now, tomorrow I’ll give it a try
I generally use a minimum of 4 walls on all of my “tooling” prints, and definitely on the higher stress parts like clamps and such. If your 3-wall print breaks, try using 4. Sometimes just one more wall can make a huge difference structurally. You can see how things get beefed up by using the slicer preview as you add/subtract walls. Also for infill, “cubic” is very good structurally (45% is plenty). Further, if you use Cura, be sure to check the “Connect infill lines” box. This makes infill bond much better to the walls, for an appreciable increase in strength. Lastly, layer thickness affects layer adhesion; generally thinner layers will be better bonded together.
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