Im having an issue where when i import in a file from fusion 360 to CM the extent of the Z axis raises by about 1.5mm.
the File i am importing has the model piece at 6mm. the heights i set on fusion are, bottom height 0mm from model bottom, top height 0mm from model top, feed height 1mm from model top, retract height 2mm from model top, and clearance height 3mm from model top.
okay, and then i import into CM and the tool path extent reads 9mm which doest add up. but anyway i ran it to see what would happen and it cut fine to begin with. started at the correct height and used my programmed multiple depths of 1.5mm. and then it cut and extra path too far deep into the waste board.
any ideas on why this is happening would be greatly appreciated. i feel like i’ve combed through my CAM program pretty well but i must be missing something,
CM by itself does nothing to your G-code, so the problem is either in the G-code file, the zeroing procedure, or something mechanical
maybe post the Fusion360 file here, and the generated G-code file, for a quick double check ? (I know you said you did that already, but sometimes mistakes are right there in front of us)
you said it cut fine to begin with, can you confirm it started exactly at the correct Z height after you zeroed ? I would have said it could be an issue with reaching Z limit during initial retract, which usually results in cutting too deep, but in your case I doubt this is the case considering you stock thickness (6mm) and small retract height.
along the same line of thought, did you use a probe for zeroing, and if so is there any chance you probed Z only while overhanging the lip of the probe on the stock corner? the lip is 2mm high, and if you did that would explain an extra 2mm depth being cut, which would look like an extra 1.5mm pass (but then again the first pass would have been 3.5mm deep into the stock, which you would probably have noticed)
mechanical: if your zero was correct and it did start at the correct Z0, then it could be your Z steps/mm that are completely off, but I doubt it because 1.5mm over 6mm is an error that would be an order of magnitude higher than what one usually gets from an uncalibrated Z
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]
@WillAdams I checked all my set screws and bolts and tightened them, I dint feel like they were anything to be concerned about but still good to know that I should check them.
There was some slop in the Z axis eccentric bolts so I tightened them.
@Julien I went back to my programming and raised the Clearance height to 10mm, the Retract height to 5mm, and the Feed height to 3mm, and cut the same File I was having problems on… and it worked!!!
Im not sure these issues fully contributed to my problem but hey, it works now. Grace of God i guess haha.
The G-code file is fine indeed. I suppose it must have been a mix of that Z slop and possibly operator error during zeroing. Anyway, there are too many opportunities to spend time figuring out why a job doesn’t work, to be spending time figuring out why it does !
