Quick release belt tensioner ( x-carrier i3 )

It´s just a baby step forward for Prusa i3, but I haven´t seen anything like it on thingiverse.

I have to tweak the design a bit and see if it stands the test of time.
I´ll post the final version on thingiverse.
-Olaf

I think having a big lever sticking out like that is going to be a problem. It's just begging curious fingers to push or pull on it or for it to get bumped when moving the printer around, and since it tensions the belt against the vertical guide rails, over tightening will flex the rails and cause the Z axis to bind.

Here's what I use- it's designed for a 6-32 screw/nut. Turning the screw pulls the pulley and tensions the belt. The screw head only rotates- it pulls the nut toward it, so it never sticks out where it can snag on anything. The design is easily adaptable to any sort of mounting.
I would change the design a little if I were making it again. The sliding part that holds the pulley has a wider base so it can't pull out of its slot. The problem is that as the tension on the belt increases, the slide pushes hard on the stationary piece and wedges it open a little, allowing the pulley to tilt outward. An improved design would have a straight slot in the stationary piece with a matching straight flange on the slide, but it might not be very printable as a single piece if designed that way. Hmmm.

Yes, it already happend, while I was changing filament during a print. I accidently brushed against the lever and it snapped loose.

I will change the round excenter part to an octagon, which has some flats on it. This way the tension isn´t stepless anymore, but I´m not tuning a guitar, right?
Also the lever can be smaller, I don´t need so much force.

That´s what rapid prototyping is good for
-Olaf

Edited 1 time(s). Last edit at 06/03/2015 10:46AM by o_lampe.

V3 is here!
Changed the excenter surface and the lever. Turned it around and now it´s completely hidden on the back of the frame.

The last 3 faces snap into position really well. A nice secure feeling.
-Olaf

It´s now on thingi
[www.thingiverse.com]

Edited 1 time(s). Last edit at 06/04/2015 09:53AM by o_lampe.

Nice work man. Fun making these things better eh? Tonight I redesigned and installed my Y axis belt tensioner.

For me it is mainly a worm up lesson with openSCAD.
I started to design a cable guide, but I have to redesign it again.
-Olaf

Quote
the_digital_dentist
Here's what I use- it's designed for a 6-32 screw/nut. Turning the screw pulls the pulley and tensions the belt. The screw head only rotates- it pulls the nut toward it, so it never sticks out where it can snag on anything.

Nice design. I did something very similar for my M90 variant.

---

New browser from the creator of Opera: [vivaldi.com]

So Why must you release the tension on your belts?

Do you release the tension on your inkjet printer? precise positioning
Do you release the tension on the belts in your car? timing and power transmission

Many timing belts (positive power transmission belts) have cord inside (rayon, fiberglass, kevlar)
that stretch very little, and set the size (length) of the belt and tooth profile and spacing
--- only a tension tweek needed occasionally.

Mismatch to pulleys and low angular contact with pulley adds much more to the angstroms of error?
By releasing the tension on the belts you may be just ruining the tension and positioning you set up!

Perhaps forming of semi-permanent bend in one place may be a problem
--- do you rotate rest the position of the belts all the time

Oh--- you always release the tension on your bandsaw -- steel different material doesn't recover welded joint

It is more about the smooth rods and the crappy lm8uu bearings that could benefit from a loose belt on the x-axis. The plastic x-ends will love a little rest too...
Also the y-stepper is held by a printed plastic part. Constant tension on that part will cause problems over time.
-Olaf