X and Y axis belt attachment support
Posted: Fri Oct 05, 2012 3:35 pm
If you tension the X axis belt enough, you can pull the carriage apart. If you tension the Y axis at all, or use a heated bed, you will warp the bed due to the leverage on the belt standoffs.
Noticing my Y axis needed tensioning, I did a look over of the whole machine and noticed the issue. Really the belt should be tensioned to itself, and there should be one attachment point to the bed or carriage, rather than tensioning the belt and bed or belt and carriage together.
In order to strengthen the attachment and avoid pulling the carriage part further or bending the bed further, I took some strips of metal, drilled holes into them, and placed them over the two belt holders so that the tension is now across the metal strips, rather than the carriage or bed. I forced the carriage back together, but I didn't straighten out the bed as I have a heated bed on top anyway, so the warping wasn't bad enough to worry about on the heated bed.
Here's the y bed after the fix. The metal strips in this case are springy stainless steel, so while there's a bow in them, they are actually providing a bit of tension themselves, pulling the belt together.
[img]http://i288.photobucket.com/albums/ll16 ... 974059.jpg[/img]
Here's the x carriage before the fix. I used a quick clamp after this picture to force it back together, then put metal strips on like the bottom.
[img]http://i288.photobucket.com/albums/ll16 ... 0C4D8C.jpg[/img]
I used two thinner strips of metal to make installation easier. I could install and tension everything as normal, then detach one side, attach the metal strip, then do the other side, so I don't have to maintain tension and fit screws through several layers at the same time.
What I would have preferred is if the belts were another inch longer each so they overlapped. Then I could clamp the belt to itself, and had only one clamp attached to the bed and carriage. One could also print a part for this. Perhaps two parts, one that attached to each belt, then a screw could be used between the two for tensioning. Something I'll consider if I find I have to retention the machine again - which might be as soon as I put it in a heated chamber.
I also to the opportunity to flip the belt on half its travel so that the smooth side goes over the pulleys on the non stepper end. This provides a tiny bit of smoother travel, versus the teeth clogging slightly over all the pulleys. I haven't noticed a difference in my prints, so I wouldn't recommend tearing the machine apart just to flip the belt, but if you have it apart for any other reason you might as well. You can see the belt is flipped in the y bed picture above. The flip occurs between the motor and the front of the machine, so the belt coming from the front is installed upside down, while the belt from the rear is right side up. I did the same thing on the x axis. The twist starts at the motor and completes at the other side of the machine, continues around those two pulleys and installed tooth side out on the carriage on that side, and tooth side in on the other side of the carriage.
Noticing my Y axis needed tensioning, I did a look over of the whole machine and noticed the issue. Really the belt should be tensioned to itself, and there should be one attachment point to the bed or carriage, rather than tensioning the belt and bed or belt and carriage together.
In order to strengthen the attachment and avoid pulling the carriage part further or bending the bed further, I took some strips of metal, drilled holes into them, and placed them over the two belt holders so that the tension is now across the metal strips, rather than the carriage or bed. I forced the carriage back together, but I didn't straighten out the bed as I have a heated bed on top anyway, so the warping wasn't bad enough to worry about on the heated bed.
Here's the y bed after the fix. The metal strips in this case are springy stainless steel, so while there's a bow in them, they are actually providing a bit of tension themselves, pulling the belt together.
[img]http://i288.photobucket.com/albums/ll16 ... 974059.jpg[/img]
Here's the x carriage before the fix. I used a quick clamp after this picture to force it back together, then put metal strips on like the bottom.
[img]http://i288.photobucket.com/albums/ll16 ... 0C4D8C.jpg[/img]
I used two thinner strips of metal to make installation easier. I could install and tension everything as normal, then detach one side, attach the metal strip, then do the other side, so I don't have to maintain tension and fit screws through several layers at the same time.
What I would have preferred is if the belts were another inch longer each so they overlapped. Then I could clamp the belt to itself, and had only one clamp attached to the bed and carriage. One could also print a part for this. Perhaps two parts, one that attached to each belt, then a screw could be used between the two for tensioning. Something I'll consider if I find I have to retention the machine again - which might be as soon as I put it in a heated chamber.
I also to the opportunity to flip the belt on half its travel so that the smooth side goes over the pulleys on the non stepper end. This provides a tiny bit of smoother travel, versus the teeth clogging slightly over all the pulleys. I haven't noticed a difference in my prints, so I wouldn't recommend tearing the machine apart just to flip the belt, but if you have it apart for any other reason you might as well. You can see the belt is flipped in the y bed picture above. The flip occurs between the motor and the front of the machine, so the belt coming from the front is installed upside down, while the belt from the rear is right side up. I did the same thing on the x axis. The twist starts at the motor and completes at the other side of the machine, continues around those two pulleys and installed tooth side out on the carriage on that side, and tooth side in on the other side of the carriage.