CNC Toolhead screws coming lose

Snapmaker 2.0
1

Hi all,

I am using rotary CNC to mill a POM cylinder into a bust, and it seems like the V-Straight Cut bit running through the material created vibrations that loosened 3 of the 4 CNC tool head screws, making the toolhead tilt sideward by 90 degrees, with the screws falling down clanging through the workspace.

I reset everything and repeated this process several times, and it reoccured (each at a later stage in the model, because the first few lines were merely air-cutting in the latter runs).

Neither screws nor toolhead threading seem to have any visible damage, and laser/3dp toolheads stay in place perfectly even for very long (100+ hrs) prints. The screws were put back and tightened by hand to maximum after each fail.

Did anyone else encounter this? Any suggestions how to counter? Should I lower spindle speed to counter vibrations maybe? If yes to which percentage and how will this impact cutting strength and overall work speed?

2

That’s going to break those little bolts. “Maximum” torque is always almost always too much torque.

Use a thread-locking compound when you mount the milling head. You want the low strength version; that one’s designed for easy unbolting later.

3

Just to be sure, what is your work speed and step down? (how many passes are you using at what depth?)

This sounds like you’re cutting (a lot!) deeper than 1mm.

4

I would agree with @brvdboss that there’s something wrong with your work speed and step downs. I’ve pushed my machine pretty hard (too hard at first and ended up causing play in the x-bracket) and never had the toolhead screws loosen up in the slightest.
Is it running smoothly or is it straining and chattering and shaking?
The proper loctite can be used as @eh9 suggests.

-S

5

POM cylinder (55mm diameter) in rotary module, rotary mode (not linkage), stock V-Straight Grove Bit, 300mm/s plunge, 300mm/s work, 1mm depth per pass.

Issue occured first about 10 min into first pass. It did not seem like the motor was overly exerting itself, rpm was always > 11k. Process was quite loud though. Bit looks unharmed and sharp after whole process and did not get excessively hot (after pausing, and waiting 30 secs, it felt lukewarm to touch).

Lotite seems to help (and only makes head changes slightly less comfortable).

Thanks all!

6

I’ll assume that’s 300mm/min and not per second? (300mm/s is way too fast)

You could try to get it on video and maybe contact support. This shouldn’t be happening. (even though the thread locking loctite might solve it for now, it shouldn’t be a requirement)