giraffneck

well, I found it, the top set screw on the short belt was loose, I thought I tightened them all, I must have missed that one (embarrassing). Thank you for your help.

The y axis belt was actually rubbing the frame, I did see the belt twisting and added washers and it didn't change anything. I will try the end caps. That's the only thing I haven't messed with yet Lol. I appreciate your help.

Maybe a clearer way to state it is layer shift.

The print sticks nicely to the bed and none of the rods are slipping I cranked on all of them and marked them with a marker, they don't move. Each layer is offset by about .5mm. It prints the layer out perfect it just shifts toward the front of the build platform a little every layer. What I don't know understand is its only on large prints and the larger the print it seemsthe larger the shift but its still an even amount every layer. Small prints come out perfect.

I am relatively new to 3d printing. I have a UM original with 1.5.7 board. My problem is that when I print large prints the y axis slides toward the front of the build platform. It starts to slide from the very start of the print and every layer seems to slide an even amount. I let a big print go till it hit the front limit and it started to slide to the left along the x axis in the same even amount. I can print small prints flawlessly, even several small prints at the same time taking up a large area, but the larger the print the larger the slide I get. I have greased all the rods, made sure the set screws were tight and that they were not slipping using a marker, reloaded cura and the firmware, tried a different stepper driver for the y motor, and tried a different arduino. Please help!!!! I have no idea what it could be.

Try Matterhackers. they have a huge selection and reasonable prices.

I am relatively new to this, I bought an ultimaker original that was a few years old from somebody and put the newest version of the electronics in (1.5.7), I also upgraded the extruder and hotend. It prints small objects perfectly every time, but when I tried to print a larger object every layer from the start of the print to the end slides down the y axis (about .5mm) each layer. I have tightened the drive belts, lubricated all of the shafts, and tightened all of the set screws, reinstalled the firmware. I don't understand what else it could be and it doesn't make sense to me that its only on prints that take up a large portion of the bed. Any advise would be greatly appreciated.