Hi everyone, I have been using my Shapeoko 5 Pro for a a few months now. So, I am relatively new to the machine and CNC in general, but I am having an issue with my Z axis.
Background: I was doing a 3d carve with some complex shapes (wave covered panel). After my roughing I used a parallel toolpath for finishing, and I noticed that as the toolpath progressed the z height of my cut had been creeping down lower into the stock. I then tried to isolate the conditions of the issue with some tests.
Material: oak
Test 1:
Stock: rectangle 2in x 7in
Bit: 1/8th Ballnose
Toolpath: Parallel
Profile: none. this was a simple flattening operation with no z engagement.
Cutting Feedrate: 150in/min
Stepover: 0.01in
Result: No Issues. Stock was flat with no noticeable z drop.
Test 2:
Stock: rectangle 2in x 7in
Bit: 1/8th Ballnose
Toolpath: Parallel
Profile: Roundover along the length of the piece.
Cutting Feedrate: 150in/min
Stepover: 0.01in
Result: 0.23 in drop from start to end of tool path. In other words, my stock was 0.79in at the start of the toolpath, and 0.56 at the end of it.
Test 3:
Stock: rectangle 2in x 7in
Bit: 1/8th Ballnose
Toolpath: Parallel
Profile: Roundover along the length of the piece.
Cutting Feedrate: 70in/min
Stepover: 0.01in
Result: Better. 0.12 in drop from start to end of tool path. In other words, my stock was 0.81in at the start of the toolpath, and 0.69 at the end of it.
From the tests, it seems like when there is some z motion along the parallel path, I start losing z height even at moderate loads (70in/min and 0.00175in Feed per tooth).
Am I just stressing the machine too much or is this some issue with the mechanical parts?
It looks like my zero is actually changing. The “after” zero is substantially lower than starting.
Steps I did:
initialize machine, verify expected zero.
run another test with the same parameters as listed in test 2. Observed similar drop in z.
Jogged bit to current x,y,z = 0,0,0
attempted to measure with calipers and roughly 0.2 in drop in zero. (it was tough to get in there with calipers).
Initialized machine again and checked z. Was in expected location.
In both instances, I checked the z in the same manner.
Moved bit to x,y,z = 0 by using the “rapid to current xy”, then “move z to 6mm above zero”. Then jogged it down 6mm to z=0. I took the scrap piece I used to zero and physically placed it next to the bit.
It was roughly 0.2in below the top surface…
After I re-initialized the machine, I did the same procedure and the bit was exactly at the surface of the stock (expected location).
That eliminates something in your program file. If your program file was doing it, then the Z-zero wouldn’t have changed (0.2"). If a setting in the controller was incorrect, Z-zero also wouldn’t have changed.
Do you hear anything different as the carriage moves along its path? It might be hard to hear a 0.2" step loss, though.
Put a black mark at top of bit where it meets collet nut. Bits slipping cause cutting depth variations.
Clean your collet, nut and bit with brake cleaner or denatured alcohol. Let dry. Also clean inside router/Spindle shaft. All that should dry and dust free.
With black mark on bit you can see if bit moved.
SO5 could lose steps but likely bit or mechanical as @WillAdams suggested.