Just updated to V5.24 on my NEMA34 Pro machine.
During homing the Y2 (right) motor makes a “thunk” just at the end of the sequence as it’s micro-tuning the alignment.
I understand there’s been some improvements made to the homing process.
Any insight so I can fix this?
Thanks
That’s normal. It’s the gantry squaring itself.
Huh… it didn’t do that before the upgrade.
Guess my concern is that I associate this sort of “mini-crash-like” noise with wear on the transmission components over the long run - but my imagination tends to exaggerate these things tho 
Nothing to worry about. It does that sometimes when it disengages and reengages the Y2 motor.
It might be a good time to square your machine if you haven’t already
Was thinking the same thing…
Thanks Eric!
FWIW, mine does the same thing – a thunk at the end of homing (stepper motors), and it was new after the prior upgrade (5.22 I think). I figure it is okay, but I never looked into what was really happening.
Depending on how the macro decides it needs to square your gantry it may lock or unlock your Y2 stepper. Sometimes when that happens there’s a bit of a thunk.
So there’s a seemingly random occurrence during homing where after the Y limit sensors are initially tripped both Y1 & Y2 motors jolt rearward 2-3 times in unison like a skipping record before reengaging the limit sensors a second time and finally coming to a rest and claiming “homed”.
And I don’t know if this second issue is related but it feels like it might be….
After homing I send the gantry rearward by 6-8 ft and then return it forward again - during this forward operation the die spring on the Y1 motor drive system will undulate (small compressions) and sometimes compresses enough to release and “clunk” like it’s skipping a tooth.
The Y1 die spring undulation does not always occur, but when it does it only does so on the forward movement on the Y axis.
The Y2 die spring never mimicks this behavior b/c she’s not a troublemaker.
A worn pinion might be a contributing factor but the gantry squaring is suspect b/c the “record skipping” behavior does not always occur.
Another potential clue is that I just remounted a project to the table that was the last to be carved by the machine only to find that its not square as expected. It’s a 30” x 30” piece and when cross-measured from corner to adjacent corner there’s a 3mm differential. The top-left to bottom-right corner measurement is the shorter of the two.
I’ve got a pair of Pro Drive gear sets on the way to eliminate the worn pinion variable but I’m not convinced it’s the root cause.
This is totally normal, it’s the digital auto squaring doing it’s job.
Pinions are consumables and if you suspect they are worn I’d replace them.
Have you squared your machine recently?
From the sounds of it these are all unrelated things, but things you should address. I wouldn’t square the machine until you get those new pinions
Yes, I’d squared it 3 months ago just after your initial response to this post. I’ll have another go at it.
Thanks Eric.
If you have loose pinions squaring is a bit of a fools errand. Make sure you correct that first if you have loose ones.
Just got finished a teardown and rebuild of both Y drives and realized that may have been a contributing factor.
Also removed and cleaned the racks to inspect and rotate between high-use and low-use zones.
The tapering of the inboard side of patches of teeth tells me the pinions haven’t been as tight as necessary.
Lesson learned.
Nice! Well you’re likely in better shape now so you can get that machine squared up. I suspect you’ll see better cut quality too.
She’s back on track.
Thanks again Eric.
You’re welcome!