Post by bLouChip on Dec 15, 2023 16:09:46 GMT
Just sharing a Lesson Learned...
Maybe this is stated somewhere in the assembly doc I don't recall, but don't be hasty if you ever have to re-adjust the X or Y rack and pinion on the original MegaV model, or any model for that matter. Take your time. What I do recall from the assembly instructions and videos was that the procedure should be performed with MOTOR POWER OFF. I should have done that.
Well, I got into a hurry, and of course bad sh*t happened with powerful machinery, go figure 
., but thank goodness it wasn't worse. While I was laser etching and cutting some 2" square wood medallions, I noticed the X dimension of some of the cut parts measured up to +0.005" over, while Y was always dead on. This was inconsistent down the X row of parts, so I figured I had some backlash going on in a few places along X. After a few "damits", I thought 'what the hell, let's adjust it', it's been 2 years since I last tuned it. So I interrupted my job at a good place where I could resume at the next part, and I proceeded to check for all points of backlash. I did that by moving the X carriage, under power via controller, to points of interest; then while the carriage is at rest and power applied to hold it frozen, I apply left and right pressure to the X carriage with my hands to check if I can see and/or feel any movement, it should be rock solid with no backlash, any backlash will be seen and felt with moderate hand pressure otherwise. So I marked the places along the rack where I felt backlash.
., but thank goodness it wasn't worse. While I was laser etching and cutting some 2" square wood medallions, I noticed the X dimension of some of the cut parts measured up to +0.005" over, while Y was always dead on. This was inconsistent down the X row of parts, so I figured I had some backlash going on in a few places along X. After a few "damits", I thought 'what the hell, let's adjust it', it's been 2 years since I last tuned it. So I interrupted my job at a good place where I could resume at the next part, and I proceeded to check for all points of backlash. I did that by moving the X carriage, under power via controller, to points of interest; then while the carriage is at rest and power applied to hold it frozen, I apply left and right pressure to the X carriage with my hands to check if I can see and/or feel any movement, it should be rock solid with no backlash, any backlash will be seen and felt with moderate hand pressure otherwise. So I marked the places along the rack where I felt backlash. Because I didn't want to loose precise indexing to my work material, I then moved the X carriage, again under power, to those locations to perform the adjustments while leaving the machine under power. BAD IDEA in general, REALLY BAD IDEA for this procedure. I then loosened the nearest rack screw in the direction of the next backlash position, and I applied a little hand pressure towards the pinion gear and tightened the rack. Check for backlash again, repeat with more pressure until backlash not present. Move to next position and repeat. Although I noticed some additional gear mesh noise after the [incorrect] procedure, I thought that was to be expected since I was adjusting out backlash. Of course again, not wanting to loose precise indexing to my work material, I didn't power down the machine to check the finished (aka readjusted) tension of the rack and pinion gear mesh up and down the X axis. Rather, I resumed my job. Although I remained in the shop while it finished to run the job (of course, safety first right 
, I didn't keep a close eye on the motion. Several of the parts at the end of the X axis where obviously cut after many lost steps in the motion commands- ut oh. I power down the machine and attempt to move the X carriage by hand and its nearly frozen, DARN, what did I do? Hasty, that's what I did. Lesson learned, again. The bad news is the resumption of the job still had some raster etching that it did under these conditions, so that concerns me long term. But anyway, I proceeded to re-adjust X rack and pinion AGAIN, but this time the right way, with motor power off, AND I started on one extreme end and worked my way down the line. I checked for backlash when finished and found none, so perhaps I dodged a bullet and didn't ruin the rack and pinion precision, only time will tell. So far so good.
, I didn't keep a close eye on the motion. Several of the parts at the end of the X axis where obviously cut after many lost steps in the motion commands- ut oh. I power down the machine and attempt to move the X carriage by hand and its nearly frozen, DARN, what did I do? Hasty, that's what I did. Lesson learned, again. The bad news is the resumption of the job still had some raster etching that it did under these conditions, so that concerns me long term. But anyway, I proceeded to re-adjust X rack and pinion AGAIN, but this time the right way, with motor power off, AND I started on one extreme end and worked my way down the line. I checked for backlash when finished and found none, so perhaps I dodged a bullet and didn't ruin the rack and pinion precision, only time will tell. So far so good. This sure speaks to the raw power of the MegaV, it takes a lot to stall those motors.