I’ll give it a shot sometime this week. It did “reliably” cut 6 passes in a row after the chain slipped. Everything looks ok with the motor mounts? The picture was with the sled in center position.
It’s also conceivable that the sled got hung up on on edge (I need to round out my sled’s edge more) and got off kilter and that led to the chain slip. That blue painters tape is what I use to keep edges down if needed.
So while I was recalibrating length, I noticed that the chain slippage is happening on the slack chain side. https://photos.app.goo.gl/2rgkBdZYpQRE9RDx2
Should the chain tensioners be moved out away from the frame a bit to straighten this out?
Instead of moving the tensioner, I added a thing that directs the chain onto the teeth from the best angle. In the picture see a piece of split tubing I slipped over the fairlead supplied with the kit. This piece is ~3/8" long, just long enough to match the distance from the face of the motor mount to the inside face of the sprocket. Nothing magic about the material, it’s what was on hand.
That’s a great idea! I’m also considering an idler pulley from a bike shop.
I ould try to add tension on the slack side, and/or move the stretchy cord mount
on the bottom out so that it pulls away from the sled a bit more (to counter the
effect of gravity that will tend to angle it towards the back)
I made the recommended checks and things seem to be looking good again. These letters turned out great other than the fact that I forgot to program tabs so they were nicked at the endpoint. I’m thinking about getting a bike tensioner to replace the bungee cord, has anyone tried that modification?
The tensioning assembly needs to store 9 feet of chain and be able to pay almost all of it out, but should try to avoid creating enough tension to counteract the way the weight of the sled pre-loads the gear train to avoid gear backlash.
Your idler pulley is an interesting idea, those are more forgiving of feed angle, so might be a good way to train the chain to the best feed angle for the motor sprocket. It doesn’t take much to set the chain onto a straight path.
I had issues with the chain jumping from the backside of the sprocket too. It would literally jump chain links because the “stored” chain was out of plane with the motor sprocket. I made a guide component similar to @blurfl’s, except bigger and out of plywood. It’s only a prototype, and I intend to make some out of derlin when I get my hands on some.
This has the advantage of being adjustable:
I can share the G-code if you’re interested, but I’m at work right now and don’t have access to it. I can post it when I get home tonight.
[quote=“MeticulousMaynard, post:27, topic:1249”]
I can share the G-code if you’re interested
[/quote]That’s a great optimization! How about putting it in the Community Garden?
That’s a good idea. I’ll post it there tonight. I keep forgetting that’s the best place for these kinda things
That looks great will build one when I get back from traveling.
Man oh man, that is pretty!!!
And that frame… that has to be as stable as they come!!! Also, it looks like you are pretty vertical, do you think that has helped you expand your accuracy across the board?
Thanks! I still need to do a full write-up on it. It’s a top-beam style frame model mostly from 1 1/2" 14ga steel tube welded into a rectangle to get it rigid as possible. I have not had any issues with deflection in the frame. Sometimes I didn’t tighten down a bolt for one of the brackets well enough and they slip, but that’s entirely my own fault.
I think that the angle you’re seeing is a trick of the camera. I made angle frames to keep it at 15 degrees from vertical, which I believe is the stock angle. On my to-do list is a new set of frames that are foldable, that way I can adjust my angle AND tuck in the Maslow when it’s not in use to get a little more floorspace back when its not in use. My Maslow lives in a 7x14 enclosed trailer that serves as my hobby shop, and right now it’s more than a little crowded in there.
The expanded accuracy really comes from the linkage kits. I also would like to try to make a derlin skin to reduce the amount of friction between the sled and the workpiece, which may help my accuracy in the lower corners of the bed.
Oh man is that pretty! Awesome.
Piecing it together, let me know if this is accurate. When the sled is at the top, there is a lot of slack chain and the stretchy string applies very little tension. Because there’s very little tension, the chain will tend to drop more to the vertical than to the 15 degrees that the frame is tilted… and when the sled is at the top, there’s less chain making contact with the sprocket and the portion of the chain between the sled and sprocket are at it’s highest tension. All of this leads to the situation where the chain is more likely to skip. Correct?
So ideally, the chain guide would be such that it tries to keep the slack portion of the chain parallel to the sled portion of the chain and would be positioned such that it maximizes chain to sprocket contact without interfering with the sled portion of the chain when the sled is at its lowest and closest to the particular motor.
That’s the idea. One beta tester fed the slack chain, sprocket, and stretchy string through a 4’ piece of 3” tubing oriented parallel to the work surface. Lots of ways to manage slack and align the chain.
Thanks . What do you think about adding your pictures to that?
Done. Sorry, I kinda rushed my way through uploading those files. This was my first time doing a pull request so I had to figure out what I was doing.
I made a more thorough write-up here, in the projects topic. Didn’t want to hijack this thread.