Y belt orientation to bed
Been looking at the Y axis again, and I am curious about how it would work if the belt were rotated 90 degrees. What do you guys think? Been trying to think up some pros/cons:
Pros :
Cons:
Also to take it a step further, with the three bearing setup the bed is riding on, is it ideal to be pulling from the center of the bed or would there be less potential for rotational friction if the belt attach point was moved off center towards the two bearing pair?
My MK3 Parts: [Bowden] [New Shoes] [TPU Micro Springs]
Re: Y belt orientation to bed
A genius has spoken!
This has to be investigated 💡
Bear MK3 with Bondtech extruder
Re: Y belt orientation to bed
A genius has spoken!
This has to be investigated 💡
High praise from the mod master! I am not worthy. 
My MK3 Parts: [Bowden] [New Shoes] [TPU Micro Springs]
Re: Y belt orientation to bed
High praise from the mod master! I am not worthy.
😀
Yes, it is possible to turn the Y-belt 90 degrees. The front end pulley holder is located here at the top edge of the front frame. Bottom of the Y motor is 3 mm lower than the edge of the rear frame part. There will be a 2 mm gap down to the table, so you do not need to raise the printer.
However, it is not possible to move the belt closer to the two bearings as the belt then scratches against the middle frame part.
This was really a fun idea.
Maybe it's possible to raise the belt a few mm.
But, will gravity pull down the belt so it scratches against the pulleys?
Bear MK3 with Bondtech extruder
Re: Y belt orientation to bed
Also to take it a step further, with the three bearing setup the bed is riding on, is it ideal to be pulling from the center of the bed or would there be less potential for rotational friction if the belt attach point was moved off center towards the two bearing pair?
It's been awhile since I used the statics part of my brain, but I think it would be better moved the "pulling point" towards the single bearing to reduce the moment load on that bearing.
Correct me if I'm wrong, but my reasoning is that the total moment load on the double bearing (Md) is equal to the moment load on the single bearing (Ms), i.e. Md + Md = Ms.
So if you move the move the point closer to the single bearing you will lower the Ms load while increasing both Md loads.
EDIT: And I guess it's a moot point anyway due to the frame restrictions that RHD pointed out.
Re: Y belt orientation to bed
High praise from the mod master! I am not worthy.
😀
Yes, it is possible to turn the Y-belt 90 degrees. The front end pulley holder is located here at the top edge of the front frame. Bottom of the Y motor is 3 mm lower than the edge of the rear frame part. There will be a 2 mm gap down to the table, so you do not need to raise the printer.
However, it is not possible to move the belt closer to the two bearings as the belt then scratches against the middle frame part.
This was really a fun idea.
Dang, forgot about that notch in the Z frame keeping us from moving the belt significantly side to side.
Glad there's clearance. I'm going to go hunt down your recreation of the MK3 and play with this. I have some really faint and unpredictable Z shifting (can only see it when light is shining down the print), and I wonder if this has anything to do with it.
My MK3 Parts: [Bowden] [New Shoes] [TPU Micro Springs]
Re: Y belt orientation to bed
Also to take it a step further, with the three bearing setup the bed is riding on, is it ideal to be pulling from the center of the bed or would there be less potential for rotational friction if the belt attach point was moved off center towards the two bearing pair?
It's been awhile since I used the statics part of my brain, but I think it would be better moved the "pulling point" towards the single bearing to reduce the moment load on that bearing.
Correct me if I'm wrong, but my reasoning is that the total moment load on the double bearing (Md) is equal to the moment load on the single bearing (Ms), i.e. Md + Md = Ms.
So if you move the move the point closer to the single bearing you will lower the Ms load while increasing both Md loads.
EDIT: And I guess it's a moot point anyway due to the frame restrictions that RHD pointed out.
This seems logical to me as well. Beyond the frame restrictions, you'd also need to have a way to rigidly mount the new pull point at its new location (so it's not just transferring it back to the original screw holes) which may require a bit more modification I am willing to do on a hunch. Maybe you could print something that fit around the bed frame itself. 🙂
My MK3 Parts: [Bowden] [New Shoes] [TPU Micro Springs]
Re: Y belt orientation to bed
Whew, sorry for the triple post.
RHD, on this image:
I wonder if an M3 screw is strong enough to handle the tension if securely anchored from one side? Curious if we could raise the idler bearing up quite a bit higher (say another 4-5mm) and have an M3 going through it into a block plastic mount. Could then flip the pulley on the stepper and get it parallel, as well. Would have the belt nearly on the same plane as the smooth rods at that point.
My MK3 Parts: [Bowden] [New Shoes] [TPU Micro Springs]
Re: Y belt orientation to bed
On the motor side, it's no problem, but I think the PET plastic is too soft to fasten the pulley with a screw in just one flange. With a metal mount it would have worked safely.
But you can move up the pulley a few mm and have a thinner flange on the top.
Bear MK3 with Bondtech extruder
Re: Y belt orientation to bed
You could make the idler mount the full height of the frame and bury a shoulder bolt really deep into the PET which I should give it enough strength.
But the head of the shoulder bolt would basically be the same thing as having another flange.
Shoulder bolt example: https://www.mcmaster.com/#90278a438/=1bsp1om
Re: Y belt orientation to bed
Been looking at the Y axis again, and I am curious about how it would work if the belt were rotated 90 degrees. What do you guys think? Been trying to think up some pros/cons:
Pros :
Cons:
Also to take it a step further, with the three bearing setup the bed is riding on, is it ideal to be pulling from the center of the bed or would there be less potential for rotational friction if the belt attach point was moved off center towards the two bearing pair?
Brigandier you old dog. This... I've been going through all sorts of ideas to stiffen the system about x. Any motion about x excites the z frame. The torque moment of the y motor excites about x I did a 2 foot bracket that supported the back plate to absorb the torque and it made no difference. This puts the torque moment about z and stops any input about x being applied to the z plate by the inertia of the y motor armature. You still have to start/stop/reverse the table but the motor is out of the loop...
The Y plate -foot bracket... didn't do anything I noticed in a print.. There are bolts that press the feet down on the table. This applied "some" pressure on the plate. Bolting it solidly would be better but I don't drill holes in things i can't replace..
Re: Y belt orientation to bed
the moments have basically two components: the arm between belt-position and bearings only induces a moment from bearing drag. The main belt loads will come from the acelleration of the heatbed/flexplate/print though. The three share a center of gravity (which is actually rising with the height of the print) and the distance from this c/g to the belt is the leverage at play.
Re: Y belt orientation to bed
Been looking at the Y axis again, and I am curious about how it would work if the belt were rotated 90 degrees. What do you guys think? Been trying to think up some pros/cons:
Pros :
Cons:
Also to take it a step further, with the three bearing setup the bed is riding on, is it ideal to be pulling from the center of the bed or would there be less potential for rotational friction if the belt attach point was moved off center towards the two bearing pair?
Brigandier you old dog. This... I've been going through all sorts of ideas to stiffen the system about x. Any motion about x excites the z frame. The torque moment of the y motor excites about x I did a 2 foot bracket that supported the back plate to absorb the torque and it made no difference. This puts the torque moment about z and stops any input about x being applied to the z plate by the inertia of the y motor armature. You still have to start/stop/reverse the table but the motor is out of the loop...
The Y plate -foot bracket... didn't do anything I noticed in a print.. There are bolts that press the feet down on the table. This applied "some" pressure on the plate. Bolting it solidly would be better but I don't drill holes in things i can't replace..
Nice design! Could you please share the .stl file? Thanks in advance
Re: Y belt orientation to bed
the moments have basically two components: the arm between belt-position and bearings only induces a moment from bearing drag. The main belt loads will come from the acelleration of the heatbed/flexplate/print though. The three share a center of gravity (which is actually rising with the height of the print) and the distance from this c/g to the belt is the leverage at play.
Agreed. It sets up a resonance of the z plate about x. The only equipment I have to test the motion is my cell phone with an accelerometer app set on top of the z plate on the screw locators. The largest amplitude I see is along the y axis so about x. Reducing the y motion seems like an opportunity.