I have paused my machine many times for only a few minutes 2 empty dust collection Etc however when I pause it overnight when I restart the Z height is slightly lower this making it necessary to sand a lot or totally ruining a 3D carve I am asking for help please
Is this a new development for your machine? You’ve also posted regarding the temperature of the Z stepper motor being too hot which could be related to this issue as well. Have you checked the set screws in the coupling between the stepper motor and the ball screw to ensure they’re tight? What is your setup like? Do you have anything adding weight to the Z axis increasing the load on the stepper motor?
The heating of the stepper motor was not me however the problem of it moving after a long pause hours this has been persistent since I’ve had the machine I’ve learned how to shut it down and adjust the g code to that point from Charlie but last night I paused it hoping it would not happen again but sure enough it did I think that’s the definition of insanity
Ah, my apologies I had too many tabs open at once I suppose and thought it was all the same user.
You shouldn’t have any drift of the machine when it’s idle unless the weight on the Z axis is greater than the holding torque of the stepper motor which I doubt is the case. This then points to a cabling issue, loose connector etc or EMI/RFI, or a bad stepper motor. The stepper motors are usually pretty reliable in my experience but it is possible you need a replacement. If all of the connections are tight and in good condition (there were a few users who reported the pin pushed out of the socket on the connector) I would open a case with Onefinity support. I leave my machine on over night and it does not move, I can come back the next day and hit go and it’s right back where it left off - you shouldn’t have this level of insanity 
Amen
Now the temperature where The Machine is if there isa change by about 30 degrees from when I paused it to where I restarted it would that make a difference
Did you ever figure out what was causing the line after a pause? I have the same issue. I pause a long 3d relief program and leave it on overnight, not turning off or cutting power to the controller. When i begin the cut the next day, it always leaves a line. It is probably 5 for 5 now, I can relate to your insanity.
I know it’s crazy
The only logical reason I arrived at was that the wood expanded or retracted do to moisture
Either that or machine moved which is doubtful
So what I do is modify code to start near line I stopped reset z zero and begin there.
Hey Greg,
do you use the hand trim router and you switch it off over night when you pause the program? The steel shaft of the router motor and the milling bit both expand with heat. A steel shaft of 200 mm length expands by 0.14 mm (144 µm)¹ with a temperature change of 60 K. And even if you do not turn off the router, even when not milling (turning idle), the temperature changes compared to milling.
See also
1. The coefficient of linear thermal expansion (CLTE) of steel α is approx. 11–13 · 10−6/K, α of aluminium is 23.1 · 10−6/K
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Yes I’m using the Makita
That sounds like a great explanation
Hey Greg,
wood also expands, but because it is a very poor conductor of heat (unlike metal), while being milled it probably only heats up directly and immediately at the point where it is milled, not as a whole. It expands with moisture of course as you already mentioned but that goes rather slowly
| Wood | CLTE α (in 10−6/K) |
|---|---|
| Oak (perpendicular to grain) | 54 |
| Oak (parallel to grain) | 5 |
| Pine (perpendicular to grain) | 34 |
| Pine (parallel to grain) | 5 |
Aiph5u,
The metal expanding is an interesting theory. I have a water cooled spindle and it runs for 10-12 hours before I pause it for the night and restart the morning. The cut the next day seems to always be higher than the night before, so that would align with the idea that the metal has contracted. I tried measuring the difference in height, and it came out to about .0035in (.089mm), which also aligns with your theory.
I will have to try this warming up process before beginning the cut the next day and see how that goes. Thanks for the suggestion! I will post an update the next time I run a long program.
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Hey Captain,
welcome to the forum!
Do you stop the spindle while pausing the program? Do you accomplish this by having the VFD permanently set to manual control, or does your VFD allow you to temporarily override ModBus control?
Hello Aiph5u, thanks! I stop the spindle, it’s permanently set to manual control. I was thinking of hooking it up to the control box but didn’t end up doing it. Initially it was because of laziness, but now that I’ve done some projects with it being manual, I kind of like having it be manual for reasons such as this.
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Split up a 14hr cut yesterday and today. Tried warming up the spindle for 10 min before running the program this morning, and I still have a pronounced line. A bit of a mystery though, cut is actually deeper into the wood today than it was yesterday (not like previous times), and the difference in height is quite a bit larger (.17mm).
I have a new theory though. The wood itself might not be expanding, but maybe it’s moving. I noticed yesterday that as the cut progressed, there was some slight warping in the wood where it lifted in the center wrt both x and y axis. I normally secure my work piece to the wasteboard with double sided tape and clamping the 4 corners, but I wonder if larger pieces like this (i.e. 20x30in) are still lifting off the table due to relieving the internal forces in the wood while cutting. This gradual warping would probably not be noticeable during the cut the same day, but if it continued warping overnight this could explain why the cut is deeper today.
In the name of science, I think I’ll test this theory by trying a paused cut on a fairly thick (and relatively small) piece of wood. Maybe mill off an inch along the y axis, then pause the program overnight, then mill another inch.
Hey Captain,
I don’t know how the grain goes in your workpiece and how long it was dried, but depending on this it may very well be possible that a piece of solid wood warps from the moment on that you have removed parts of it.