Z9M3 Rear belt Alignment and Tensioner CoreXY by gallaghersart

Last crawled date: 3 years, 1 month ago

Z9M3 Rear belt Alignment and Tensioner CoreXY (OLD)
** Zonestar now has a metal part for this
**As of Aug. 6th 2018 I’m printing new and better versions of this, so as long as no print failures I’ll post those in @40+ hours. Teaser picture included of new "Dial it in" beta…
Working with what I have, My goal was to be able to leave 5m belt uncut and only the ends that attached to front of hotend carriage would be damaged from zip ties and cut if need. The other ends wrap around spacers then into a belt tensioner. Any excess belt can be wrapped around tensioner and left uncut. I also wanted to be able to fine tune the tension, Zip ties around object basically only gave you the resolution of a single belt tooth to work with. This allows very small changes thought out @10--15mm of belt movement with a turn of a screw
Right know I do not have the funds or ability to do the metal work to make this smaller, for the time being I damaged some LEGO brinks to give me some more space in the back to extend the Y end stop. To give way to over large belt tensioner
Ideally unit would be half as big. The 2 aluminum belt bocks would be cut @ the 40% mark and have nuts welded to the larger parts, so once made only the bolt, belt and belt blocks would need space cut out for them.
Currently the bolt lays at the bottom and pushes up the blocks as the bolt is turned. So the hole cut out is rather big and includes all parts in single hole. With cut belt block and welded nut on top, the only holes needed for each part needs made. And with that a more stable and smaller unit.
Currently this tension needs to work with my Z9M3 back end and belt alignment. As the large washers on the bolts that attach to the back of hotend carriage, are the placement of the belt tensioner screws. As the belt tensioner is held in place with tight belts the bolt that applies the pulling force lays on top of the washers. Without washer I would think the bolts would just go thought the belt alignment module.
So how to use it.
1St CoreXY unit needs to be square, and I mean it.
Once all screwed sown parts are in place, take long 5m 6mm (worked for my 300mmx300mm) and feed belt equally though back of belt tensioner.
Run belts though correct layout of your unit.
Place front ends of belt though their locations that they will be ziptied to. Leave very little though the hole about as much as you need to tighten belt as before.
Pull excess belt though the back of the belt tensioner
You want unit to basically be loose tight. Mark with non damaging marker the location of the belts on the back of tensioner.
Remove ends from front unit to give you some space to work with
Carefully pull belt out while marking or keeping track of location, one belt at a time.
Pull a belt out long enough to apply the belt blocks and bots and nuts. One nut at bottom and washer / locknut above belt blocks. The idea is once you slide all parts back into place the belt will be at a location that very little loss of belt will take place on the front.
Do the other belt as above.
Make sure belt tensioner is lined up and flush with belt alignment module.
You should not be able to pull any additional belt from the back.
Now pre tight the belts.
Now for the fun part.
My lower belt is the left of the nozzle.
Tight temporally with your hands with each belt and notice how your square drive carriage will go out of alignment as you tighten a belt. In the end the unit needs to be square.
SO with the lower belt tighten to a loose belt, not something you would want to print with. Clip it and notice carriage should be 5-10mm off on one side.
Now tight the top belt so unit is as square as you can get it. As you tight the top belt the lower belt will also get tighter.
Basically tighten the belts so they end up as square and all most as tight as you want it, BUT not too tight. As the belt tension can only tighten.
Now with your hand move the hotend around the bed (should have motor cabled discounted already). Makes sure things move easily. Personally, I like steel cables and things tight, and I Also changed my XY motors to some more powerful and 400spteps.
With the unit at the back and center with your hand in the center of the unit as not to favor a side. Move the drive carriage to the very front. With my unit I measure the distance between Y carriage’s and front support on both sides.
If the Space is same on both side you’re done, lucky you! Skip to verification steps
If not..
Now again with your hand pull on a belt and make it tighten to see one side shrink in distance. The goal is to only tighten one belt.
Once you know what belt needs tightening, unlock bolt from turning as you screw top screw to make room for belt blocks to raise up, I used lock nuts for this part. Slowly adjust this single bolt, if you go to far you will have to push alignment block and belt back in and then pull on belt outside of carriage to get slack back.
Move carriage around and re measure, repeat until square.
Once all is good tighten down the locknuts on the back of the belt tension to keep unit secure. Wrap uncut /unused belt around belt tension, tie off with ziptie to secure it. Move carriage around again to make sure things are still square.
Print of a skew test to verify if you want, and then tighten belts to correct the print. I did a 250mm x 250mm test and was unable to see any difference that would show unit is out of alignment or askew. The idea is not to modify software or firmware to correct askew alignment.