Chain jumping off on "Pull Chain Tight" calibration step

Hi All! I have been trying the step where I run the chain over the motor and connect to the right side then pull it tight. The problem I keep having is it is jumping off, even when I hold onto the chain at the right side.

I am up for any suggestions on this step or an alternative method.

Jumping off the left side? If so, check that the left motor mount is secure and carfully aligned so that the sprocket is parallel with the worksurface and the chain feeds straight toward the right motor.
If it’s jumping off the right side, is the right motor sprocket aligned with a tooth at 12 o’clock, and have you put the end link as shown in the picture?


Mine was doing this too, jumping off the right sprocket? Start the tighten operation with more slack and be really quick to hit the stop button when it’s looking taught is my current solution.

I held down on the loose end of the chain to keep it more engaged in the gears. Our motor(s) or something beeped a bunch of times when it was taut and seemed to stop themselves.


So when you get the left chain onto the right sprocket, it looks like this… correct?

And when you “pull chain tight”, it comes off the right sprocket? I’ve yet to have mine come off the right sprocket when wrapped like this.


This happened to me. Make sure it didn’t slide your motor mount when pulling the chain tight.

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If the chain comes off when you pull it tight, feed it a little further so you
have more wrapped around the sprocket.

In operation, you will be pulling as tight as this step, so you want to be sure
nothing moves under this stress.

Is this the motor measuring step? Wouldn’t feeding more chain make that measurement wrong? Not sure I am thinking of the right thing as I haven’t calibrated in a long time, but thought I’d ask.

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New build here and I just battled my way through this same “chain jump” issue. I double and triple checked all alignments and ensures the sprockets were perfectly vertical. Seems to me if the sprockets are installed properly on the shaft. Meaning the setscrew is centered on the flat shaft area. The chain will not stay as the above picture shows. Look close, the sprocket pictured is a few degrees past vertical. Thus holding the chain as desired but not exactly accurate.
Simple fix
Purchase a 2$ spring style clamp, precisely position both sprockets vertical, extend the chain about 3" past sprocket, place the chain as stated in instructions “3 links”. Now place the clamp at 45° with bottom jaw on the sprocket and the top on link #2. Allow the chain to tighten an once it loosens, remove the clamp and then the chain from the right sprocket… continue the calibration


Also if you get past this… Don’t remove the chain from the left sprocket. Instructions aren’t clear about this. The step after measuring the distance between the motor sprocket teeth at vertical is to press the button and the chains will move to really close to center of the work area. The programming and chain movement here knows the chain is already extended to the right motor. Even if your sled chain mount selection is attached from the bottom of the sprocket.

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I’ve had my right sprocket aligned at 12 o’clock and have done this step numerous times and don’t recall the chain ever slipping off the sprocket over the last 6 months. I don’t doubt you are having a problem and it seems your fix would work. I’m curious as to why we are having different results… are the sprockets the same? Maybe the sprockets in the last shipment are slightly different?

You’re right, different manufacturers or design could surely cause this.
Are there detailed measurements of the sprockets floating around?

I know most know this but what harm could come from being 10 deg off vertical as long as you set both sprockets identical? Perpindicular is key here.

no, because what you are doing is measuring out how much you are feeding out
from the first motor, then measuring how much you are wrapping around the second
motor (you attach to the 12 o’clock pin and rotate the second motor), and then
measure how much you pull back

so the system keeps track of all this no matter how much you rotate the motors.

Ah, gotcha, that is new since I calibrated. Thanks.

I don’t think you can feed out more chain and get an accurate measurement… your measurement will be off by the extra amount you feed out. The current calibration routine subtracts two links from the measurement so if you feed enough to wrap three links, your measurement will be by 6.35 mm.

I don’t think it works this way unless it’s something in development that I’m not aware of. Only the left motor moves in this step (or at least that was the case when I calibrated a couple weeks ago)

you spin the right motor to wrap the links, not just hang more links over the
right sprocket.

the system takes into account the motion of both motors

So perhaps this is new in GC 1.10 or 1.11?

The right motor must be set to 12 o’clock before running the motor measurement to help hold the extra links in place. The right motor does not move during the measurement, though, only the left motor moves.

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