fwiw i am wondering if my machine is hitting the homing switch and thus homing at a different height than when the job started. i don’t know this for a fact - but i’m going to make a post about this later.
did the router come loose? i had something similar happen today - and i wonder if the router slipped.
i have had the endmill slip before - that has happened to me. human error on that one.
how i wish CM had a preview function.
can i drop gcode into CC and preview it there? i run the simulation on RhinoCAM but it would be cool to see that repreated in CM prior to running a job
Hitting the limit switch in the middle of a job should stop it retracting but not ‘rezero’ the machine. I would have guessed slipping bit, belt, or sliding off the rails. Is the router positioned at the bottom of the mounting collar?
but that doesn’t tell me how CM is interpreting it.
that’s what i’m interested in. seeing what CM will do before it happens.
i dunno - maybe i;m being too picky. maybe seeing it in chilipeppr would be sufficient.
i would def vote for this type of feature to be added to future versions of CM.
FYI: I have the same problem, and chased it for weeks. I finally figured it out to be that the Z axis, on retract was losing its sync with the stepper motor because (sometimes) a large chip (MDF and/or metal) was getting caught between the v-Wheel and the rail.
I didn’t really fix it, because I think it would take covering the wheels, but what I did was lessen the Z retract between cuts from 10 or 12mm (Carbide Create’s default) to just 2mm.
I have been looking for covers similar to this to permanently fix the problem:
Rich, that would make alot of sense. These are the deepest pockets I’ve created and the 1/4" endmill was kicking out bigger pieces. Also, it wouldn’t happen at the same depth each occurrence, so probably not software related. I’ll lessen the z retract when I try again next time and see how it goes. Thanks!
I don’t think Slippage is a problem in general (V-Wheels slip, Belts don’t).
My case is where a large particle gets jammed between the wheel and rail (with the Z going up) and the motor stalls for a moment which throws off the calibration (since this is an open loop system). This means that the Z is not off 1+ mm and will now go lower (1+mm) into your work part. Sometimes it was off as much as 10mm, and it made scrap faster than the speed of dark.
hmm. i got furry bits caught up in between the belt and the tensioner - so i dunno. the v- wheels i’m not worried about. i def get some slippage though - manually jogging - loses a couple mm on any given setup, setting the zero etc. not a biggie - i’m really trying not to mill deeper than 1.75 inches, after that it seems the machine is likely to have issues with the dust boot and such.
I did this once. I had a part with a 1/4" hole in a basin like your part, and I was using some douglas fir. When it bore straight down with the 1/4" bit to create a 1/4" hole, the wood heated up, and the wood clamped down on the bit while being extracted. This made the belt slip even though it was not loose, and then it tried to move to the next area, even thou the bit was still in the 1/4" hole. My solution was to make the hole a 0.28 inch hole, to avoid the swelling hot wood condition. This typically only happens when boring deep straight 1/4" holes near maximum depth. By using 0.28 hole, the bit wobbles around in many circular motions in steps and stays much cooler.
PS I really doubt the belt is slipping (if it’s fairly tight. These Stepper motors only deliver 18 pounds of (magnetic) down force before they (the motor) slips.
The point is, a 1/4 bit boring down to maximum depth in Douglas Fir will heat up nearly red hot, and the bit will be difficult to extract, causing belt slip or motor slip. Even with a hand plunge router you have to plunge in steps to maintain bit coolness and perform chip extraction.
Thanks for the reply Kelly. For this, I wasn’t boring deep, just pocketing slowly. The hole in the center was supposed to be the next layer down in the pocket, but chose to continue into my wasteboard.
I’ve been experiencing the same problem. Out of the blue, the machine will plunge down into the center of the workpiece, around 1/2”. It’s not program related because the program has worked as intended, in previous runs. I did notice some sawdust caked on the rails.
Belt tension — the Z-axis should be guitar string tight (but careful not to bend the motor shaft): http://docs.carbide3d.com/assembly/shapeoko/xxl/step-5-belting/ on deep cuts it may help to remove one spring from the Z-axis temporarily, esp. if one hasn’t added a spoilboard on top of the wasteboard — it also helps to install the router as low as possible (installing the Makita adapter upside down will help). Some folks have found it helps to remove bolts which won’t stay tensioned (M4 Z-axis tension bolt, various V wheels with eccentric nuts), apply a thin bead of threadlock along the length of the threads, then reinstalling. See the video at: https://www.youtube.com/watch?v=_lIIb_PdziA Note that the X-axis motor is held in place on standoffs and if those bolts are loose this can cause belt tension issues.
It is also important to be sure that the collet is correctly tightened, the endmill fits correctly and doesn’t slip, and the router is mounted securely in the mount, and that the mount doesn’t shift. Note than endmill pullout can happen gradually, especially when profiling against tall walls.[4]
If you continue to have difficulties, please send in the .c2d source file, generated G-Code, and step-by-step notes on how you are securing your stock and setting zero relative to it and we’ll do our best to help puzzle things out.
Thanks so much for the feedback Will! Per your recommendation; I increased tension on the “Z” belt, checked the pulley set screws, adjusted the eccentric nuts, tightened the router mounting bracket, and removed one of the springs. I will test it out once I receive some fresh endmills.
After some closer observation, I figured out the root cause of the machine plunging to a “Z” depth that wasn’t intended.
When cutting a deep pocket (1-1/2”), the chips were being evacuated straight up and into the “Z” rail mechanism. Chips accumulated on the track, to a point where the wheels got stuck and the motor could not overcome the interference. Then I’d here the motor make a clunking noise, just prior to plunging out of control. I stopped the machine prior to the erratic plunge and tried to move the slide mechanism by hand. I couldn’t do it until I cleared the track of sawdust debris.
I confirmed this to be the problem after running successful build and ensuring the mechanism stayed clean with compressed air.
I think a good future long term solution is a vacuum dust boot. I’ve got one on order and look forward to trying it out soon!
