Axis Tensioner - X axis
by MakerBlock, published
Description
Make sure your X pulley is assembled as shown to the left and is adjusted to the correct height so that the X belt is totally level all the way through ( wiki.makerbot.com/cupcake-xy-stage-installation#toc3 ). The tensioner may work if you have your pulley assembled differently, but you'll have to make sure the pulley doesn't rub against the tensioner.
Special thanks to SSD ( thingiverse.com/ssd ) for testing and feedback. Version 3 has a slight change suggested by SSD which may help some people.
If you're trying this for the first time, use Version 2.
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Instructions
Fit the tensioner around the M5 nut still on bolt.
Replace the X axis pulley with the M5 nut around the assembly.
Drop an M3 nut into the slot in the tensioner.
Drill a small M3 hole in the side of the MakerBot in line with the pulley.
Insert a M3x? bolt and tighten. (I am not positive as to the length of bolt required. This may differ slightly)
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Anybody tried this on a recent-batch cupcake?
On my batch 12, if I put the tensioner right up against the left wall of the cupcake, the belt is way too loose. For reference, if I turn it around so the end with the captive nut is towads the X motor, there's about a 1/2 inch of open space between the Thing and the left wall of the cupcake..
Ok, I've made one of these and installed it. A few problems, not sure if it is my machine's calibration or the part. First, it was too close to the pulley and was preventing it from turning, so I took the assembly apart and reordered it. Instead of bolt pulley/bearing nut washer it is now bolt pulley/bearing washer nut tensioner washer. This moves the nut out a bit more for the tensioner to grab it without too much rubbing on the pulley. The makerbot supplied washer's outer diameter is uncomfortably close to the pulley inner diameter, so I sanded that a bit so it didn't grab when tightened. Also, I sanded the top of the tensioner so it is totally smooth, no nubs to grab the pulley.
I've had the tab that retains the m3 nut lift up a couple of times during installation. It seems to have grabbed now, we'll see if it holds. The big bolt is just barely finger tight. I've put a second nut on the bottom and locked the two nuts together so it doesn't rattle loose.
I now have my
belt within 1/4 of the M3 screw's turn from slipping...very close!
And now my X axis (with tensioner) is quieter than the Y axis (without tensioner), and the gentle whir of the extruder motor is clearly audible and almost louder. The X belt still buzzes every now and then...might try the spring nex
t before I try the Y axis tensioner. I managed to get Y almost perfect, don't want to mess with it yet.
I sware I only posted once. My browser must have gone insane. Hope some admin moderator can fix this.
Ok, I've made one of these and installed it. A few problems, not sure if it is my machine's calibration or the part. First, it was too close to the pulley and was preventing it from turning, so I took the assembly apart and reordered it. Instead of bolt pulley/bearing nut washer it is now bolt pulley/bearing washer nut tensioner washer. This moves the nut out a bit more for the tensioner to grab it without too much rubbing on the pulley. The makerbot supplied washer's outer diameter is uncomfortably close to the pulley inner diameter, so I sanded that a bit so it didn't grab when tightened. Also, I sanded the top of the tensioner so it is totally smooth, no nubs to grab the pulley.
I've had the tab that retains the m3 nut lift up a couple of times during installation. It seems to have grabbed now, we'll see if it holds. The big bolt is just barely finger tight. I've put a second nut on the bottom and locked the two nuts together so it doesn't rattle loose.
I now have my
belt within 1/4 of the M3 screw's turn from slipping...very close!
And now my X axis (with tensioner) is quieter than the Y axis (without tensioner), and the gentle whir of the extruder motor is clearly audible and almost louder. The X belt still buzzes every now and then...might try the spring nex
t before I try the Y axis tensioner. I managed to get Y almost perfect, don't want to mess with it yet.
This appears to not be manifold. Skeinforge left a big triangle out of it between the hexagon and the handle, nearly makes it two parts instead of one. The manifold fix trick in blender didn't help. This gives me an excuse to play with meshlab I guess.
Okay - I just fiddled with it and uploaded a new version. Let me know if this works...

I tried this on a batch 15 cupcake cnc and when the tensioner is against the wall it is WAY too loose.
I imported the model into Sketchup and made it shorter... love it now :-D