CET print skew/stepping

[artbot]

this one has me really confounded. we have this issue lately/permanently where our prints are stepping to the left about 1/8" per every two feet. the bottom and top of the print are perfectly
plumb to the printer. (image attached)

the encoder reader was cleaned, then replaced, the encoder strip was cleaned, then replaced. still stepping exactly the same as before.

we then swapped out a carriage motor (used, but tested). still stepping.

we then swapped out a servo driver (used, but okay). still stepping.

a motion control tech looked at the machine and advised that the data cord may be an issue.

a very experienced CET engineer noted that the belt may be getting old and stretching under deceleration.
one observation is that when the carriage changes direction, the motor pully seems to pass up it's stop point. then it quickly couter rotates to reposition, then it is jerked into the next
thread of printing. it's as if watching the pully, it's bouncing to a stop. i feel that i should film this and upload for viewing.

has anyone experienced such a persistent stepping issue with their printer (flatbed or roll to roll)? this one is getting to me a bit in that we may be rebuilding the thing and it's just an adjustment.

thanks in advance!

aa

 

[Gino]

We had something similar last week. I wrote about it.

Seems our printer was skewing off also. The encoder strip and eye were both relatively new and no matter how much we cleaned it or turned it around, it kept doing the the same kinda skewing. turned out the last tech we had in here to fix that, had put the wrong parts in the machine. They fit properly and worked, but not 100% as time went on and it just got worse and worse. when the tech came out, she right away said, you have the parts to such and such machine and they aren't supposed to work at all. Well, they did, but not for ery long.

I'd try checking your numbers and cross referencing them to make sure you do indeed have the right things in there, if nothing else makes sense. It's worth a try.

 

[MrNick86]

#Artbot
I had a slightly similar issue last week. Not that drastic, just a light alignment issue only on the origin side of the print bed. I lubed up all of the slides and spiral gears and it improved. It seems like it randomly doesn't home exactly the same on the step alignment. We had one instance about 6 months ago that the step alignment was not traveling at the same rate and the gantry literally when crooked and gashed itself on the side of the printer. YIKES! Just keep everything well lubed at all time. That is my advice.

 

[artbot]

@mrnick86 i get what you are saying. our gantry is dead on 90 degrees all the way down the table. i'm going to shoot a video of my pully behavior. maybe if you have a minute you can look at yours and see if this bouncing to a stop is normal.

@gino the replacement motor is the same motor.

this one has me stumped so far.