Stepcraft 840 not cutting to depth

[CommandaZ]

Hello All,

I apologize if this is not the correct forum. I'm trying to diagnose (or get troubleshooting ideas) so that when I'm in front of the machine tomorrow I can try some suggestions. We are using a Stepcraft 840 to cut some guitar bodies out of 1.75" stock material. Currently we're using MDF so that we can make sure the gcode is correct and get our process down before spending money on nice wood.

Our issue is when the toolpath is run, the depth is incorrect. If I set the toolpath to cut to a depth of 1" it seems to only cut about 1/2" over the expected passes (8mm depth per pass and the tool really doesn't seem to move more than 2-4mm per pass - I haven't measured it exactly). I've tried recreating the toolpaths in VCarve in metric and imperial and the gcode it outputs appears to be correct. I went so far as to recreate the whole drawing in metric (was originally in imperial) to no avail. After we make a cut that doesn't cut as deep as we expect and "GOTO ZERO" the machine returns to the home position flawlessly, so I don't think it's losing depth because of a plunge speed issue or anything like that, but I'm brand new to using a CNC so maybe that is wrong?

Also, when I tested running some codes in MDI field to set the Z height from 0mm to 25.4mm the travel is exactly 1" so I don't think it's an issue with the step calibration.

Any troubleshooting thoughts would be greatly appreciated - I have about two hours with the machine tomorrow to figure out what's going on - if I don't solve tomorrow it will probably be a couple weeks before I can get more time with it. I've attached the GCode for just the neck pocket toolpath for your review. In this case the neck pocket should be cut to a depth of .625" (~15.88mm) but it appears to only be cutting to a depth of maybe .35"

Thanks!

[cncdrive]

Hi,

From your description it looks to me that your Z axis calibration (steps per setting) is wrong.
I remember a similar issue when somebody has the same problem with a Stepcraft machine and then the issue was that he installed the wrong profile file with the Stepcraft profile installer.
Please note that the Stepcraft profile installer includes both the Stepcraft V1 and Stepcraft V2 profiles, so maybe you have a different machine version which you installed the profile for.
The different machine versions has different step per value settings!

So, please verify that you've installed the correct profile file.

You may also try to recalibrate the Z axis step per value, but the easiest is probably just to install the correct profile file, because that has the proper settings for your machine.

[cncdrive]

And if it is not the calibration then check your g-code file, I mean check what Z coordinates are in the code, because maybe the g-code file has the wrong depths.

[martin54]

If you have checked that it is not a calibration issue are you using the right post processor when saving the file?
Are you setting your z zero to the top of the material or the machine table? When you select go to zero after the machine has finished moving is the bit either at the same level as the top of the material or touching the machine bed (position will depend on your initial set up) If it isn't then you are probably either losing steps on your z axis or the bit is slipping in the collet & being pushed up.