The 5 year old Shapeoke XXL at our local MakerSpace has stopped cutting deep and rather skates over the material to cut after a few passes (even with softwood), after which the depth setting is completely of. What is wrong and how can you fix it ? I suspect it is related to the height control suspension mechanism.
Insufficient belt tension, worn belt, lost steps due to electrical issue (loose connection, failing stepper driver).
Thanks. Can these errors be visually inspected ? I suspect a mechical error (it is like it is not pushing hard enough into the material to cut)
It is really annoying when you have to make pockets, and the different passes gets different depth
Belt tension is usually tested by plucking the Z-axis belt when the machine is powered up.
Z-axis belt condition is pretty much a matter of pulling the belt and replacing it.
Wiring can be tested w/ a multimeter while powered off — just make sure to test connectivity through the full range of motion for each axis.
Thanks. Will check the belt. What does the springs on the height mechanism do ? Could they be too tight or loose ?
The springs prevent the Z-axis from dropping all the way to the bottom and breaking a delicate tool when power is cut.
Some folks will remove one so as to reduce the spring tension (and to keep it as a spare), but that should not be necessary.
Thanks. I will check the tension of the belt and the springs.
The belt drive Z on an SO3 can work but it has several problems. The main one is the belt gets loose and/or gets teeth missing. On my SO3 I have had the same X and Y belts on my machine for 6 years and have never had any problem with them. However when I started out I had a belt Z and that always had something wrong with it. I eventually replaced it with an HDZ. That may not be in your budget but it is worthwhile upgrade. However the belt Z is what you have and you can make it work.
The main things to check if it is in a multi user space is to do periodic maintenance because multiple users wont do any maintenance.
- Check belt tensions on all belts.
- Check eccentrics are clean and adjusted.
- Check that the pulleys on each stepper motor has tight set screws and one of the two are on the flat spot of the stepper motor.
- Clean the rails of the Z and you can put some light oil just rubbed on and not soaking.
- Power off the SO3 and slowly push the Z axis side to side fully and it should run smoothly. If you go too fast it sounds like the belts are coming off. That is simply EMF created by the stepper motor. Then push the gantry front to back and back to front slowly and it should move smoothly. If you find any rough spots address it. There may be debris on the v shaped rails the axis’s run on. You can clean them with a stiff brush or the white (fine) 3M finishing pad. The Z axis can be pushed up and down but is a little harder than the X and Y axis to push up and down.
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Removing the 2 springs seemed to solve the problem
Make sure to always put a block of foam underneath the Z-axis to support it when power is turned off.
Ok. I just put the springs back on.
Rule of Z: Don’t change the cutting depth if the CNC cuts incorrectly. Just do the following and you will eventually get there: probe Z, run same cut, repeat 
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