RAMBO Board Problem Printing Circles

I have had a RANBO 1.1b configured and running for a couple of weeks on a MendelMax1.5

It ran great for couple of weeks. I was printing ornaments and peace signs and they were printing great.

Last knight I ran some peace signs and the circles which were printing great are now printing with a slight irregularity which is messing up the entire print.

I checked all of the mechanics and everything is smooth. I tried printing on different sections of the bed and still the same.

I re-flashed the firmware and still the same.

I tried varying the Slic3r setting and still no change.

I checked the belts tension and the belts seem OK.

No changes were made to the Marlin config which worked great fro a couple of weeks and a lot of prints.

Then problem is repeatable and consistent. Pretty much the same regardless of size.

Any ideas?

If the prints in the picture are oriented as they appear on the printer - it's likely your X axis is slipping. The set screws that attach the drive gear to the stepper motor are the most likely cause.

Printing the traditional hollow cube is a quick(er) way to diagnose most of these things. If you print it as a spiral vase, it goes quick and does not use a lot of filament. Quick feedback is a good thing.

The most likely causes are all mechanical:

1) Loose belt
2) Loose drive gear
3) Loose carriage (yes I've had that one)
4) Sticky carriage bearings.

Put a mark on the drive gear and the motor shaft, run the printer a bit and see if they move relative to each other.

If the print is rotated and it's the Y axis slipping, you can include various bits and pieces of the Y carriage on the list.

Thanks, uncle_bob, it was a loose drive gear.

Pull the gear and make sure the motor shaft isn't messed up. If it's chewed up, at least knock down the big chunks. You might also consider ordering a backup motor if it's messed ....