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MoonCactus

Robust and precise NEMA 17 steppers / belt tensioners

by MoonCactus Nov 17, 2012
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Great thing! As I posted in the picture I made, if I the plastic motor spacers are used, the tension is unevenly distributed between the upper and lower bolts, which tilts the motor axis a bit. I prefer the plastic spaces because they provide better aeration and view of the axis. I have tested replacing the spacers with a modified version of this tensioner on the inside wall (printed in PLA). But it gets deformed both by the pressure of the motor against the wall and the belt's tension that deforms the holes.
So could you add a longer version that also holds the top bolts? This should solve the issue.

Wow, are these cylinders part of the official/revised ultimaker kit? It really does not look like an improvement... do they need to spare some wood or what? :D

Anyhow I've just added a "stepper_tensioner_upside_4screws.stl" for you, tell me if it's ok!

They are! (http://wiki.ultimaker.com/Ultimaker_rev.4_assembly:_Frame)http://wiki.ultimaker.com/Ulti... And they even added an injection moulded (!!) part to the extrusion head.
Actually, using the wood assembly and washers you can screw the standard sized bolts only one or two turns into the motor at most. So the new cylinders are 11 mm long (1 mm shorter). You can't do that with any combination of wood. This in theory should reduce the tendency of these bolts to loosen and loosen the belt.
And thanks. I'll print it right away.

Uh. Well, why not... The UM is not a vitamin-free reprap anyhow.
Actually what should have been injection moulded first is the fan duct ihmo, and may be the air duct for the electronics!

This is so nice, works perfectly.
Why Dont Ultimaker include this in their designs? it is so flawless :D

hell yeah, it works like a charm!

I just mounted these on 4 ultimakers, and they are great!
Some things to keep in mind when using these:
-You need 25mm m3 screws for mounting the motor, otherwise the screws won't go deep enough into the motor.
-When your belts are really loose, keep in mind that you need to increase the length of the slots where the motor screws slide in. It's really easy to lengthen them by using a small file.

Nice remarks, I'll update the info. I forgot about the screws because mine were already 25mm (I had to add an nut b/c they were too long). Thanks for the info.

Good idea and nicely done.

Excellent idea. Looks like a good solution to the problem. I usually insert a screwdriver through the top of the opening in the side for the pulley, and lever the motors down to get enough tension then tighten the screws, this looks a lot neater.
Minor tweak but why not reverse the bolt, so it is accessable to a screwdriver from above rather than underneath?

Good remark, I added your "upside" variant. It was a sequel of my very first idea where I thought the stepper would be in the way... but hey, it's not on the same side of the wall!
I kept the holes in the same place so the tensioners can be swapped. 

have a spring below the vertical m3 and the lower fixed part!? would that work?

Spring-loaded NEMA 17 steppers / belt tensioner

Yes, with a very long m3 you could put one between the screw head and the washer against the lower fixed part. I think the belts have enough elasticity by themselves though