how accurate are the homing switches? Are the xyz zeros stored in eprom?
It is not the accuracy of what is stored in CM but the accuracy and/or repeatability of the homing position. Every time you machine homes it can be a few thousands off from the previous homing cycle. All origins are an offset from the homing position so if they are off so is our preset origin.
I have an SO3 with proximity switches and I have never noticed any variation in the origin over power cycles. That does not mean it cannot be off a few thousands but for me it has always been very accurate.
Edit: I have seen some people say the origin is stored in EEPROM. Some people say it is stored in CM on your computer. Either way the origin is saved it is t he accuracy of the homing cycle that determines where the origin will be after a power cycle.
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My experience with the S4Pro is that homing is accurate to +/- one step of the stepper motors. That is, +/- 0.025mm or off by as much as 2 thou. For the HDM and S5, I don’t know what resolution a single step equates to but I think it is smaller than that.
For any kind of wood working project, that is more than accurate enough. For multi setup metal machining, that amount is noticeable. If I had to rehome then I will always reset the zero position for x/y but I don’t usually bother for z.
Unless CM is doing something funky, the work zero positions are stored in the eeprom. Whenever you set a zero position in grbl (the software running on the machine) it automatically saves them in the eeprom.
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I’ve noticed that homing cycles are pretty accurate (for average wood jobs), but if the estop gets bumped and you power cycle, the zeros for the material will be noticeably out.
The work offset is held in the PC, not in the machine EEPROM.
There’s no reason an E-stop would cause the next homing cycle to be different unless the machine is mechanically bumped out of alignment in some way.
Fun fact - when we were working on the latest CM beta, we noticed that the probing cycle frequently repeated to exactly the same step as the prior probe on an S5. (Which uses almost the same internal code as a homing cycle. The switch and the feed rate are different.)
We’ve also learned that MANY MANY people set a zero the first time they get a machine and then never set it again.
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It’s close, but last time I did it, I noticed the repeated toolpath was out by ~.5mm in the x plane. z and y were dead on. I can’t remember which axis was out the previous time I bumped it, but I remember it being off a touch. Enough to create extra lines in the work that I had to sand later.
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