I was recently running a CNC tool path and at 85% complete the work origin appeared to have been lost and the next pass was about 4cm offset causing the bit to carve deeply into the already completed work. I had loaded the G-code to the printer via wifi and then ran it locally. I was using a 20 degree V bit at the maximum spindle and travel speeds. 0.15mm overlap with a 0.001mm stepdown for each pass. I was carving bamboo. This project had been running for nearly 6 days when the work origin appeared to have been lost. Has anyone else experienced a similar failure? Thoughts on the causes for this are that perhaps the internal memory of the printer may have been exceeded and the origin was lost as a result.
Why do you think the origin was lost?
Whenever I had a failure with the same symptoms, it has always been because the bit got stuck (too agressive cut, a part of the work that came loose, a hard spot in the wood etc) that caused the steppers motors to skip steps and thus everything shifting in a certain direction.
However, if it’s taking that long I think you’re way of working could be optimized (doing a roughing pass first, with a bigger bit, and fine details with a smaller bit afterwards)
2 Likes
If that’s not a typo…lol. You need to have some engagement with the workpiece, otherwise you just burn through the material instead of cutting.
Bits are not infinitely sharp, they have a small rounded cutting wedge. You have to have a large enough step down (axial engagement) and step over (radial engagement) to cut well and minimize heat in the cutter.
The maximum travel speed is in the ballpark of 9000mm/min. That’s way too fast. I don’t know if Luban limits it to something less than the machine’s maximum speed.
What were your settings again?
Regarding your original question
There are some suspected issues with this machine involving very long runtimes. Possibly something to do with compounding rounding errors. Many many very small movements could cause an issue. Your theory with printer memory is probably not far off the truth.
There’s probably not a good fix for making the printer stable for a days long job. Adjust your settings and split the jobs up into smaller pieces, like suggested above.
I have attached a photo of what occurred below. Which is why I thought my origin had been lost. It looks as if the starting point for the tool path had shifted. I’m not sure how a screw driven linear rail slips therefore introducing an offset into the build, but I suppose that may have been another cause. What seemed to make the most sense to me was that the long run time of the build ate up the memory of the device and caused an overwrite due to the need for more.
I do not know how to make the snapmaker do multiple tool paths with a roughing pass followed by a finishing pass. I have been 3D printing for years, and this is my first attempt at CNC milling. Additionally, I don’t think snapmaker supports nonplanar milling, but instead mills in layers like a reverse of 3D printing.
It’s not the rail that slips, it’s the motor itself that thinks it has move forward, but because it was blocked actually didn’t. A stepper motor doesn’t counts the number of steps it takes, it just tries to do the number of steps it’s commanded to do. When it’s blocked, the it will be stuck in a place, but the program will think it actually made these steps
That’s still possible, based on personal experience not something I have seen, but then again I’ve never done a single toolpath that takes more than 10 hours or so. So it’s definitely possible.
With Luban that’s a challenge, and apart for some simple relief carving I would recommend other tools. Fusion is the most popular one for users on the forum here. But it does come with a learning curve, but once you’ve got the basic setup covered, it’s relatively easy for standard toolpaths.
That’s actually a limitation of Luban that isn’t able to generate those type of toolpaths. The device itself is perfectly capable of that.
Looking at the picture, assuming thats a 15x10cm (6"x4") rectangle, a job like that shouldn’t take more than a few hours on the SM2 with the right toolpaths and milling bits.
To get started, this topic contains some useful info:
There are some really nice tutorials you can find on youtube about Fusion 360 CAD/CAM as well
Could you post the output of M503, I want to look at a couple settings that have known issues.