Hi all, Just curious if others have seen the same amount of backlash that I'm seeing in my stock Mini V 500mm actuator. Regardless of belt tension, on multiple of these actuators, I see .2mm-.25mm of appearant backlash. I have tried to change my microstepping, tried changing motors and varied the belt tension. Nothing is changing the behavior. My test setup: Mitutoyo 1/2" stroke dial indicator on a magnetic base touching off on side of carriage. Test motion: After an initial (+) direction move, zero out dial indicator. Starting at this 0mm position, make consecutive 1mm movements in the same direction to 5mm, then reverse direction and return to 0mm in 1mm incremental steps. Backlash equals the apparent offset in dial indicator. Data looks like this (mm): .001, .969, 1.959, 2.968, 3.979, 4.997, 4.209, 3.206, 2.193, 1.205, .226 V-Slot® Mini V Linear Actuator Bundle Does everyone replace these stock belts for something else? I can't imagine its belt stretch because all of my consecutive direction moves are very close to 1mm.
Check that the pulley is properly set on the motor shaft, and not slipping on the shaft when you reverse direction: - Make sure to have a setscrew on the flat of the motor - A little non permanent locktite between pulley and motor shaft never hurt - Locktite the setscrews too - mechanical vibration can work them loose
Thanks @Peter Van Der Walt, I like the idea and I tried the loctite and that did not seem to help the problem. The stated accuracy of the actuator is .26mm, so I guess i'm just running into the expected backlash with using a belt.
I have seen this with wheels that are set too tight, does the carriage move smoothly and easily with the belt removed? Can you (with some thumb force) spin the wheels against the extrusion? Cheers Gary
Thanks @Gary Caruso, I was able to reduce it from .25mm to .08mm by adjusting the wheel stacks until they all showed the same rolling resistance. The eccentric stacks are borderline too loose as the eccentrics just spun when I turned to tighten them against the rail. This setup does feel almost too fragile, but I can monitor it over time.
You should be able to tighten the bolts all the way, if you can not then the wheels are missing a washer in between the bearings, or the bearings are not set fully in the wheel. Cheers Gary
You were right, the bearings were not fully seated into the wheels. I thought i had pressed them sufficiently hard, but there was a fraction of a mm left to go. Perhaps I should invest in a mini arbor to save my thumbs in the future. Regardless, now each assembled stack shows the same rolling resistance, even when tightened snug.
good find! What I do is place on hard flat work table, place small block of wood on top and press down with hands hard. cheers Gary
