Fixing limit switch clearing and sloppy axis movement

[profexorgeek (Justin)]

I’m a new Shapeoko 5 owner and new to CNC but have done a lot of 3D printing and general trouble-shooting with 3-axis systems. I wanted to post a problem and a fix in case it helps others.

TLDR Problem: My machine cut sloppy circles and then started failing to initialize. It wouldn’t clear the X limit switch and threw GRBL errors.

TLDR Solution: the ball screw shaft was loose for the X axis introducing some play in the X movement, especially when switching directions. Tightening the shaft nut fixed all problems.

The first problem I noticed was that some small circles I cut for magnets were sloppy and inconsistent:

Later, when I started up my machine, it wouldn’t initialize. I don’t remember the exact error but basically it wasn’t clearing a limit switch. I turned off the machine, manually moved the gantry to clear all limit switches, then turned it on and checked all switches with a piece of metal. They all lit up fine. In the diagnostics menu, they also showed the correct status when testing. I figured out it was the X limit switch that needed clearing and noticed a jerk when the X axis was changing directions. Turning the machine off again, I manually moved the gantry on the X axis and noticed it had sloppy play when changing directions. The shaft was loose and the motor would turn for a bit before the shaft engaged, causing it to not fully clear the limit switch when initializing.

I figured out it was the ball screw shaft but it took me awhile to figure out exactly which thing needed tightening. Here’s how you do it:

Remove the X axis stepper motor and coupler, which requires loosening both the collar screw and a set screw. Once the motor and coupler are removed you can access the shaft bolt:

Once those are off, you can tighten the shaft bolt using a 16mm (I think) socket with an extender. You should have a tool that came with your machine that prevents the shaft from turning when you tighten it:

Reinstall the the coupler (tightening both the collar and set screws), the motor, and make sure all screws are nice and tight and you should be good to go!

Note that this can happen on any axis. I have had issues with the couplers and shafts coming loose on all three axis! Make sure these screws stay tight over time and use the temporary lock tight between the couplers and the shaft to save yourself some headaches.

[jlfletcher (jimmy fletcher)]

Thank you so much for this information, same problem here! I done what you said, up and going again!! I got my 5 pro 4 days ago,this is all new to me. Thank you again!!

[profexorgeek (Justin)]

Glad it was helpful! In general you should expect bolts, wires, and other things to come loose or otherwise act up as you break your machine in. I recommend checking these regularly in your first couple of cuts. Setup, vibration, and movement are guaranteed to make a slightly loose bolt become very loose! Here are some other things mistakes I’ve made that maybe you can learn from:

• One of my Y Axis motor couplers came loose and the Y Axis got misaligned. I had to tighten the coupler’s collar screw because the motor wasn’t properly spinning the ball screw shaft.
• I pulled a motor wire loose from it’s connector when securing the wiring, causing Y Axis misalignment again - motor wasn’t turning at all.
• I didn’t make the tabs thick enough on an early cut, the piece came loose and damaged my 1/4" downcut endmill when it cut into a hold down bolt.
• I didn’t know you should flatten your spoil board. Mine is only about 1/16th over 36" and I mostly cut small parts so I haven’t flattened mine but if you are going to cut big things, make sure your board is flat! An easy way to check is to lower your bit to about 1/8" from the spoilboard and jog it around slowly, checking the gap. There are more sophisticated ways to check but this is a simple way.
• The default tool speeds are REALLY conservative. I often run my cuts at 130% or manually change the feed speeds. If you do this, start slow and listen to your router RPMs.
• I have a sort of “pre-flight checklist” that helps remember all the things to do when starting a cut so I make fewer mistakes.

[pcperks (Phil Perks)]

Looks like I’m having a similar issue right now as well. Found things loose but after tightening it all up it still seems like my right Y axis is still moving different then the left. Going to keep at it I guess. I’ll figure it out eventually.