Then check all the mechanical aspects — the basic points of adjustment for a machine are:
(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 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.
Thanks. I am testing powered on: I know that when power is off, I can move the machine around freely.
It turns out that the left side does not move at all, while the right side has the play in the video. And the stepper is turning on the right side, so the link from the belts to the stepper appears to be solid. It is as if the right stepper simply does not care to hold position. Is this a possible failure mode? It functions properly otherwise (I can do CNC runs), so I doubt that the wires are not hooked up properly.
.150" offset is miles off… coming from a 3XL owner.
Since the machine is powered on… It seems as Josh was alluding to. I’m willing to bet the pulley is rotating on the motor shaft. It’s difficult to tell from the video, but the shaft doesn’t seem to be moving, only the pulley. I would ensure the set screw is tight on the shaft flat.
I had an issue not too long ago where my cuts started to drift and noticed as you did, one side of the gantry was rock solid where the other side could be moved when the machine was powered on. The pulley set screw backing out was the issue for me.
OK. I am dumb. Not a stepper problem. Thanks Will and Brian and Josh. One of my set screws was missing, and two were loose. With that fixed, there is no more play in the machine.
I see no reason why not. I have a standard-sized SO3 which uses flip machining without issues. Workholding is key… can you hold the workpiece in the same place every time you place it on the baseboard? You could make the workpiece an exact dimension to butt up to a straight edge/right angle you have placed. Alternatively, a jig that will hold your workpiece and that you fix into place on the baseboard will assist you to machine in the same place. Belt tension is a useful thing to address. I tune my belts with a vibrating guitar tuner attached to the machine endposts until they all read C3 [130.8 Hz.] The Hz value is derived from the informative work by @LiamN (Measuring belt tension, squaring and calibration)
Remember that many end mills will often only be nominally sized. This fact may be responsible for you not getting the accuracy you desire. I attach a couple of images of my baseboard with a workpiece that I can orient in any direction (North, East, West and South on both sides). Consider this the minimum accuracy you must achieve if you are to successfully mill on both sides. Add in belts that may be pulling unevenly, with uneven tension issues, along with end mills that are not the size you thought they were. Add inaccurate and insecure workpiece holding, aided and abetted by baseboard-to-gantry inaccuracies, then you can see that there is a lot to consider before undertaking two-sided milling.
We’ve all been there.
