# Straight line curves down at top of the sheet (solved)

One more My partner covered the error in video 2 at 1:44. All the rest is irrelevant.
V1
V2

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one interesting thing (not related to this problem) in the v1 video, it looks like the sled consistantly tilts to the right when in the bottom corner (the chains look like they are still pointing at the bit so it shouldn’t affect accuracy)

check that the chains are moving freely on the arms

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I’m going to get metal fine grain wet sanding paper and polish the arm shiny. The kit ‘snaps’ inwards in both low corners, close to where the corner cut is. I have space to move the motors out, that will solve it.

Update: Reducing the sled weight by 4.8 kg let me push the feed rate up to 1000 again
No visible (eyeballing) curve at the top any more.

Reduced weight

Conclusion:
A sled with a weight of 15.9 kg = 35.0535 lbs produces a sag in direction of the cut at the top of the sheet. It can be partly compensated with lowering the feed rate, but to eliminate the curve you would have to go turtle speed.
Reducing the weight of the sled by 4796 gr = 10.57337 lbs seems to have eliminated the error and enables feed rate of 1000 again.
I would say that we have a stall that is not caught, or better we found the max weight of the sled

ToDo: A horizontal straight line cut along the top of the sheet, once from left to right and once from right to left. Any remaining curve should become visible.

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When you say the kit snaps, is it similar to the jump that I saw in the linkage evaluation tests? I wouldn’t have expected that because your linkage mounting blocks look so rigid. The following gif is a rather extreme example:

That is such good news. I’ve been watching this thread, worried that updating to 1.06 would have given me similar results. Good to know that its probably the weight of the sled which was the culprit. I might also have to lighten my sled to avoid similar issues. Right now it weighs somewhere around 40 lbs (~18kg)

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It does exactly that what is shown in the gif. Only on the extreme low corners and when I force a twist that it would never reach on its own.

I took the kit off and are working on a spacer extension. It was to wiggly and not save, as there was not much tread left in the wood after adding spacer circles and washers. I just wanted to figure out the hight needed and will now add the second block of hardwood on top to make it rock solid…

We still have the arch-bug Velocity slow down and arced cut that I believe now is not related to this here. 1.03 is said to not have that issue.

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Okay, that’s good, I’m glad to hear that this isn’t an issue that would arise during regular use. It has been one of my concerns with the top-mount system since it started happening to me during the evaluation tests.

From what little testing I’ve done with this issue, keeping the bolts positioned correctly is key to preventing the linkage slips. I’ve been able to drastically reduce them myself by adding a spacer to keep the bolts aligned to each other. My guess is that you’ll have similar results once you solidify that riser assembly.

That’s unfortunate. I’ll keep using 1.03 until the bug is fixed.

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Hi, I’m not sure what you mean by quide pulley.Has there been a post on adding a guide pulley?

Thanks

Perhaps something like this?

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no more like this

Topic
“How to Avoid Chan Wrapping”

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I have the sewing machine bobbins from start, no need to replace found.

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I like that a lot
looks a perfect setup
going to swap them asap
Thanks

Or this? Sorry, bit of a shameless plug for my own stuff

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And within a few minutes we have putt together the “Chain Guide Wiki”. I love this place.

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I’d be really careful about how you source those bobbins, at least wait until the owner isn’t home.

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Maybe ‘Maslow’ a sewing box in exchange?

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I think ->Jackie<- deserves a mention here. I was going through my scrap and/or collectables when she asked “What are you looking for?” and I explained that I need something round that can turn, to help guide the chains. She disappeared and came back with bobbins. Not so easy to change them now, even if I wanted to.

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and it’s obsoleted by running the chains acros the top beam

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That is correct. The new solid riser assembly eliminated any ‘snapping’ of the kit.
Sanding and polishing of all parts and washers got rid of ‘the rough edges’, providing smooth move. Tightening the screws needs a sensitive touch, hard enough not to wiggle and loose enough not to block. Note that all my parts have a slight bend. For the horizontal arms I made sure they all ‘curve’ in the same direction while mounting. The vertical arms are mounted mirrored, so one would curve down and one would curve up. A little hammering with a rubber hammer straightened them.
After moving around with the arrow buttons, I would say I have nice and solid kit and am ready to explore the unknown depths of triangular kinematics.

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Not necessarily, it’s motor mounts can still extend beyond the beam, or the counterweight pull at an angle. Watching the way the chain meets the sprocket is still important, and positive control is not a bad idea.