K. Then disregard what I suggested. X is definitely the issue.
Do you have the idle current setting on? SW4
I’d increase the current to 2.03A.
Then I’d try 1/8 steps and see if it makes a difference.
Neil, I have that DIP switch set to always full current instead of the 1/2 current mode. (didn’t make much sense to me to have that for this kind of machine)
1 Like
Instead move X to the left 30mm, put your indicator up against the right side of the Z axis, then move your X to the right in the smallest step increment you can. Did your indicator show any movement? If so does it match what you told it to do? If not how many steps does it take till it does? Then move X to the right 30mm, put your indicator up against the left side of the Z axis, then move X to the left in the smallest increment you can. Did your indicator show any movement? If so does it match what you told it to do? If not how many steps does it take till it does?
1 Like
What current does the stock controller board send to the motors? Must be much less than 1.7A if I remember the power supply rating correctly. @neilferreri
I still suspect the pulley is lagging a bit behind the stepper or your controller is doing something funky.
Pretty sure it’s still the DRV8811…1.9A.
Interesting. Before I sold the power supply and controller board, the PSU I believe said only 7.5 amp output? Not sure how you could have 1.9 continuous for each motor when other accessories that can be plugged in also need power.
They’re actually DRV8818…2.5A peak. They must be current limited.
(You made me go out to my 15°F garage for that info)
Because that is not how motors work. If you actually measure the resistance of a stepper motors windings you’ll find that they are in the milliohm range. If you applied 24V to say 0.008 ohm winding you would get 3000A flowing. Instead the stepper driver is converting the 24V to a very small voltage to get 1.7A to flow through the stepper winding.
1 Like
Why do we use 48V for more performance then if the resulting voltage that ends up being so small at the business end? Also, the winding resistance seems to be much larger around 0.5 to 1 ohm.
Motor theory is confusing. LOL. I do know that the Stepper driver is using PWM to control the voltage. The pulses in the PWM output are peaking at 48V they are very short pulses though and so the average voltage is MUCH smaller. Why 48V is better than 24V is something I am still figuring out.
Sorry… I am wrong. BLDC motors have low winding resistances. Stepper Motors have relatively higher resistances. 5 ohms seems common. Still 48V through 5Ohms is still 9.6A. So the PWM thing is still correct.
Oh ok! 
I was thinking with the motors completely standstill that 2 amps were continuously flowing through the coils. Anyways, will report back tomorrow on the X axis. Thank you all!
1 Like
Its all about the torque of the motor when you are comparing 48V over 24V.
Sort of like hammering a nail with a 10 pound hammer versus a 1 pound hammer. The nail is going to go the same distance, but it will move more quickly with the 10 pounder.
I went ahead and bumped up motor currents to 2.03 amps RMS. They are still cool enough to touch easily.
Still trying to track down whether this is a software issue, I’ve messed with the belts for probably 3 hours total now so I hope that can’t be it. Side note: we really could use a better belt tensioner design. They slip way too easily when trying to hold an allen key and pushing downard at the same time while holding tongue at right angle.
There was a thread recently about making custom fancy ones:
1 Like
It’d be great if these could be purchased and for the Shapeoko Pro. Running our business we don’t have time to make tensioners unfortunately!
I’m starting to wonder if a flat tipped set screw for the flat portion of the D shaft of the motor would be a better option for securing the pulleys than the standard supplied cup point set screw.
So, that’s what we did today. And it turns out the pulley grub screws are M4 and not M3 now.
Used M4x8mm screws, which are actually about 2mm longer than need-be, however, should the head ever break off you have something to grab on to with a vise grip.
Turns out the X axis is basically impossible to get tight enough, there’s a consistent 0.2mm of backlash which is most likely attributed to the belt clip slipping before the belt is pinched at the end, even with using longer bolts to try and use as an aid. We even exposed a fresh portion of belt that goes through the clip to try and see if that would help; nope.
The only thing I can think of to prevent this would be to super glue the belt together at the end and then tighten it.
Any other simple ideas would be greatly appreciated. We cannot open sales again until this is resolved.
