Sorry for the late reply. Kids, study and work had sapped what little spare time I’ve had.
The surface finish is some sort of hot dip I think (AN 5-7um BRIGHT DIP CLEAR) is what is on the invoice. I really cant see the machine exerting enough force on the tube to deform the alloy (plastic parts after all) and the alloy tube in my current MPCNC is still in perfect condition (the surface of the tube is barely marked) after perhaps 20-25hrs run time so far.
I have other issues to contend with. The abhorrent weather conditions we’ve been having here have melted/deformed all the parts of my current MPCNC to the point that it unusable for any real milling at the moment. I have been playing around 3d milling some high density foam for learning purposes while I reprint my parts in PETG.
That is an epic print time. 31hrs straight is ambitious! Kudos. May I ask what printer you use? Nozzle? Layer height? I’m reprinting my PETG parts at 0.2mm layer height, with a 0.4mm nozzle.. My K8200 prints very nice parts after all the upgrades I’ve done, but it is very slow. One roller F takes about 8hrs with my current settings.