Round when should be square

Any ideas on what I should look for to see what caused this?
I have cut multiple calibration squares out of the bottom right corner with no problem.
The same shape was cut out right above it.
Nothing was snagged when this happened.
The upside down mountains were my doing, I pushed on the sled to see if there was some sort of sag problem. Which I don’t think was the case. There was a lot of sag in the chain but not anymore then normal at that area. The right motor started pulling up way to soon.

That is a classic sign that the friction between the sled and the workpiece is too high.

what direction was the router moving when doing these cuts?

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Counter clockwise.
Thanks, that makes sense, I’ll work on reducing friction.
I noticed when I rested my hand on the sled lines would cut straighter. This must have made it slide better. Should I use a heavier sled maybe?

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That looks like a misread line of Gcode to me. Would you be willing to share the Gcode file so we can take a look and see if it does the same thing in simulation?


Night (37.8 KB)

so counter clockwise is moving away from the far motor towards the corner.

This is the area and direction where gravity is producing the least amount of

What is happening is that the sled is getting stuckand not sliding into the
corner properly. As that chain starts pulling, the sled starts sliding, and
slides away from the far motor as it starts moving up producing the curve.

slowing down the feed rate may help, sanding/waxing the sled may help, adding
weight to the sled may help (but it will hurt up near the top), making the
machine sit closer to vertical may help.

going from a 10’ top beam to a 12’ top beam will roughly double the force that
gravity is applying here, so that should help a lot.

sanding/waxing the bottom of the sled is the easiest thing to do, so I would
start there.

David Lang

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early on when we were testing L shapes in the corner, we saw this same thing
happen when the sled was sticking due to being angled back too far or too little
weight on the sled.

If the cut were going the other way, what you would get is a squiggly vertical
line as the sled stuck and then dropped.

David Lang

Similar to this?

Same project this was just cut on the left side also moving counterclockwise

The top cut that I barely see in the picture is what I would expect in this
case. the bottom one is a little more odd, but it’s a plausable result, the key
to notice is that the cuts are not straight, but rather wander a bit.

Added to troubleshooting bad cuts table, If anyone has a good picture of the squiggly vertical line, post it so I can put it into the table. Maybe @ScrumdyBum could get a picture of the one above without the odd one below.

This was a pocket cut so I’m not sure it is what your looking for

The gcode runs OK as I can tell so I think I was wrong :grimacing:

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