MPCNC – Long-term testing and material decisions

1. Long-Term observations on the XYZ part

I found a small crack in the XYZ gantry today. This is the second time that I´ve seen this. I milled some aluminum as you may know and I had a mild crash when setting up the endstops but I thought I was fast enough switching it off before it took damage. I printed some parts in the meantime and re tightened the XYZ assembly.

This is obviously a weak spot in the construction, at least if you over tighten the gantry. This is hard to measure as it will break sometime after tightening even without use. It was printed with the suggested high infill and outer wall settings but with a line infill instead of grid. That also could have influenced the partstrength.

The first time it happened on the upper XYZ part. I printed the replacement part out of PETG. It seems much stronger and surprisingly it is not bending the tiniest amount. I expected PETG to be tougher but more flexible but in direct comparison with the PLA part underneath in a tightened state on the machine this is way stiffer. (grey)

2. Conclusion

I´m reprinting the bottom XYZ part with PETG.
Thomas Sanladerer tested the same PETG in his filaween series and he confirmed the toughness of the material. The flexibility of PETG can be neglected in my opinion.

MPCNC filament spool holder

My Hobbyking Fabrikator prints just nice but there are times when the build volume is just not big enough. So why not use the capabilitys of the MPCNC for that? I used the MK8 Extruder and mount from Ryan and designed a compact spool holder that uses leftover parts I had from the CNC build. In my case those are two M8 metric screws with a length of 70mm, a nut and two 608 bearings. Combined it looked like this:Spool holder postion

MPCNC spool holder

The clamp for 25mm tubes is fastened with four M3 *16 and nylock nuts. It can be rotated to aim at the printhead. For now it is available for center holes of 53mm and a width of 53 mm spools.

It can be downloaded here: