I am losing my mind, I have a shift that appears when machining on my shapeoko 3XXL.
I always machine the same part from the same file, nothing changes and the zero is set in carbide motion.
I am attaching a photo to better visualize the problem. we can clearly see that on the top piece the holes are offset upwards by a few millimeters.
I thought it was a belt tension problem, but everything’s under tension.
Could it be that the GRBL card is faulty? or tension problems? or electronics?
(for belt drive machines) Pulley set screws — verify that these are in-place and secure — be sure to check all axes/pulleys (including Z on machines w/ belt-drive Z-axis, for an HDZ, check both coupler screws).
(for the SO3/4, X- and Y-axes, and the belt-drive Z-axis on Launch and summer 2016 SO3s) V wheels / eccentric nuts (per assembly instructions)
(for HDZs, and HDMs, and SO5 Pros) check that couplers between the motor and ball screw are secure, for the SO5 check that the DAC which transfers the rotary motion of the ball screw to linear machine motion is secure on the carriage/gantry. See: https://youtu.be/cb9RR2KZTHM?si=gDWPF-ZHFfHAEuQo and note MG and that support has a PDF to send.
(for belt drive machines) Belt tension (see the relevant step in your instruction manual, Note that the X-axis motor is held in place on standoffs and if those bolts are loose this can cause belt tension issues. Also, belt tension for the Y-axis stepper motors needs to be even/equivalent on each side — a significant difference can cause skipping on one side eventually resulting in lost steps on both. Measuring belt tension, squaring and calibration
Naturally, this assumes that all the wiring is in good condition and all connectors secure per the Machine Operating Checklist. Verify that all wiring is in good condition and all connectors are secure, and that all wiring leading into connectors are properly in place and are secured so that the wiring leading into and away from connectors will not shift.
A good video overview on setup:
Tramming the Z-Plus: https://youtu.be/rGOGlNurglE
Ensure that all screws are in place and secure, esp. on the linear rails on a Pro.
After you have confirmed the set screw is on the flat of the shaft, a line as shown, in line with the flat of the shaft will do the same thing visually. Just have to look to see if the flat is still lined up.
To make sure you understand, I make knife handles in series with a handle reversal.
I have an offset that appears during the first machining operations, and consequently also during the reversal, even though it didn’t exist during my previous machining.
Here’s how I work:
I zero the machine at the top right.
I use my macro to bring my milling cutter to my machining zero.
I define my new zero on my stock using the macro.
4 I start machining
When I configured my settings at the very beginning, I made marks at various points on my machining plate with known coordinates.
Today, when I enter these coordinates, my milling cutter comes to rest with a slight offset (the cutter is no longer perfectly aligned).
I therefore suspect that the end-of-stroke sensors must not have positioned my machine correctly when it was zeroed.
Normally, the offset when homing is a function of:
variation in sensor distance activation — this is usually quite small
where the micro-step is in relation to the switch physically when the switch is triggered
In practice, the variability is roughly half the step-distance (1/40th of a millimeter on a belt-drive machine).
Since it is easy to see that circles are not centered, the best practice is to machine all the visible nested holes first so as to ensure that they match up — said holes can then be used to secure the parts onto a fixture which has a suitable mechanism for ensuring that things line up — a metal plate with two holes which may be probed is a good approach (use one for the origin, the other to ensure that the fixture is mounted squarely).
This sort of thing should have been covered in the series:
