Chain + sprocket issues

After quite some time using the Maslow with good success, I now have a problem where the chain will get caught and start wrapping around the sprocket. This is close to the center of the sled’s travel, and it happens on the left side when the sled is moving toward the upper left. And now it happens very repeatably, every time at this spot, so essentially my system is down until I resolve the issue. I am using a bungee tensioner which has been working reasonably well to this point. But I am ready to build a better tensioner.
I just printed the shown chain aligner and cleaned/lubricated the chain but it hasn’t resolved this issue.
There is quite a bit of grip from the sprocket teeth to the chain at this point. I am tempted to try and file the grippy teeth down.
But I am wondering if it’s possible my chain and/or sprocket are just worn / stretched / damaged. Or if I need a different alignment / tensioning system. It seems like the slight rotation of the chain on the slack side is causing much friction on the tooth to chain edge interface (on the tooth edge away from the motor).
I know that chain stretch is an issue with bicycle chains (there are even tools designed to measure this, one guide says to measure the chain by measuring the distance between n links with a ruler and compare actual to theoretical.). I have had a couple of chain wrap incidents recently.

I work on bikes quite a bit and those chains stretch over time as the rollers wear and the pin tolerances get sloppy. It is easy to check with a ruler. I’m not sure what the measurement should be for this setup. Also, the teeth get sharp with wear. Can you show a picture of just the sprocket? Maybe short of replacing the sprocket, you could put a “roller” in so the chain comes off at a different angle and put a bit more tension on the slack side?

A "roller " could be something like a wood screw with a plastic sleeve to let the chain slide by. Just some ideas. I’m interested in finding out how to fix it because we all will likely see this at some point.

Thanks, yeah I have tried a few rollers (nylon standoff with wood screw), problems did start after moving one for another reason (was interfering with the motion). But the position you indicate could be a good idea.
Not easy to get a good pic of the sprocket but here’s an attempt. I will probably pull it off to take a look and consider filing down the sharp edges. It would be good to have a reference measurement for the distance say 20 links of chain should be to measure stretch (from the bicycle world I think 0.5% is the desired tolerance).

Definitely some scarring on the sprocket and some sharp edges. I will try and sand / file down for now and probably order some new sprockets and chains just for good measure.

Sanded the sprocket and outside edge of the teeth with ~200 grit to smooth the rough edges and scars and now it is at least getting past the problem area (chain still catches slightly in one spot but does not wrap).

I do feel like more of a fillet on the outside sprocket edge would be helpful for avoiding this problem. Still, maybe there is chain wear also.
Also, what material are the sprockets? Maybe they are a bit soft if the chain is damaging them, stainless steel might be better?

Here’s a pic after sanding.

Stainless steel is very soft and will gall very easily.

One link still sticks enough to cause new chain wraps. New chain and sprockets have been ordered.

My diagnosis is wear on the sprockets mostly due to too soft sprocket material caused excessive friction then several chain wrap incidents which caused further sprocket and chain damage.

Suggestion for improvements: more durable sprocket material (hardened steel or similar), and slight change to sprocket design to reduce sharp edges on the outside face. Possibly improve mounting guidelines for motor mount alignment to reduce any potential for chain related sprocket wear.

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the sprockets are designed to have the chains very aligned with them (IIRC the
spec allows < 3 degrees of error in the alignment)

so it’s really important to get your chains parallel to the workpiece.

remember, these are stock off-the-shelf components, and the amount of use that
they get on a maslow is trivial. These are the same sprockets/chains that a
go-cart of small motorcycle would use.

David Lang

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