Hi everyone I am having a reoccurring issue in my z axis while cutting pockets. After about .30in before the machine repositions for the next step down, it seems that my z axis binds and then the machine assumes that is the retract position and begins driving down the z through the full thickness of the material. I have slowed and increased feed rate with no luck. My belt tension seems good. I am getting some resistance about two inches from the top of the carriage. Any assistance would be greatly appreciated.
Please check to see if there’s something mechanical hanging things up.
We have the following notes on checking things:
- Pulley set screws: http://docs.carbide3d.com/shapeoko-faq/shapeoko-3-how-to-check-the-pulley-set-screws/ — be sure to check all axes/pulleys including Z.
- V wheels / eccentric nuts: http://docs.carbide3d.com/support/tensioning-eccentrics
- 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]
Also feeds and speeds may be a consideration: https://docs.carbide3d.com/support/#tooling-support and see https://www.youtube.com/watch?v=S9bceJxpqG0 for concepts on this and https://www.precisebits.com/tutorials/calibrating_feeds_n_speeds.htm for a testing technique and see the series #MaterialMonday: #MaterialMonday on YouTube
Beyond that it’s usually a matter of Calibration and Squaring the Machine c.f., http://docs.carbide3d.com/shapeoko-faq/how-to-calibrate-the-machine-for-belt-stretch/
I started having the issue more frequently after a belt change. I went ahead and checked all of the v wheels again and readjusted the z belt. I ran the machine again XXL and the first pocket was a success the second was a failure. After your response, I did find the z-axis motor bolts had about 1/8 of a turn to be tight. I will readjust the tension and see if that helps. I also backed the v wheel off a bit as that seems to be causing more of a bind. I will continue to work on this and review the feeds and speed information. Thank you @WillAdams
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Another thing I checked was my z rails for being parallel to each other and they were spot on.
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Check your retract height. The homing switches aren’t limit switches, if your Z retracts further than the physical Z envelope the belt will slip(even if tensioned properly) then the machine has no idea of where it’s at and tries to bore a hole to China (unless you’re in China, then maybe it bores to Wyoming?). This happens most often with thick material, or longish end mills, or just a really high retract height.
Dan
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