Calibration moving one motor wrong direction in Ground Control V1.20

I received my Maslow CNC kit last week and yesterday I built my frame (Bar’s Bolt Together Design) and attached the motors etc. and am in the process of calibrating. I am using a Mac with High Sierra with Ground Control V1.20.

I successfully measured the distance between the motors using the chain. I did this by measuring the distance between the two axles in MM and then extending the chain that much plus 1 inch (25.4 mm) – in my case this amount was 3040mm. Then I put the chain on then let the motor tighten it and the distance as measured by the motor was found to be 3014.1mm.

The next screen says: Now we’re going to select the direction in which the chains pass over the sprocket." Here is the screen shot:

I looked at my setup (which I built following Bar’s Bolt Together Design) found here. Following these instructions I ended up with left and right chain layouts that look like this:

And a close up of the chain going over the motor.

And here are the same pictures for the left side.

Looking at the Ground Control screen shot and comparing the picture there with the chain travel for my left hand motor I conclude that I have a “Chain off bottom” feed. When I look at the right side, my brain says that I have the same feed there even though the sprocket on the left motor will be going counterclockwise and the sprocket on the right will be going clockwise.

There are a few ground control screens that I am going to skip over until I get to the screen where “Now we are going to adjust the chains to a known length” shown here.

I had previously unhooked my chains so I could measure the distance between the motors so I need to attach the chains and then extend them. Since I have Chain off bottom feed, I naturally attached the left and right chains as though they are being fed out to the sled, in other words, like this.

When I extend the left chain, the motor turns clockwise (and the chain falls off).
When I extend the right chain, the motor turns clockwise and the chain extends properly.

I am confused about how you can define “Chain off Top” and “Chain off Bottom” without taking into consideration the side the motor is on and the direction the motor is going to rotate. Given the image showing “Chain off bottom”, I would expect the left hand motor to turn CCW and the right hand motor to turn CW. What am I missing here?

More importantly, how do I proceed to a point where I have a working system!

I have not gone to v1.20 (using v1.18), but you are placing the chains correctly for the bottom feed configuration. The left motor should rotate counterclockwise. Try exiting Ground Control, restarting the computer, and either advancing through the calibraton steps back to where you are, or using the manual calibration to get to the same place in the process. If the problem persists, you could try v 1.18. (v1.19 has a known bug at start-up when running on Windows.)

Good Luck!

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Did you use ground control to feed out the chain?

That page gives step by step instructions.

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I think the issue is the same as here:

I don’t think that the machine is expecting the chain to be moved back to the first link at that step, it will retract automatically

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I switched to ground control v 1.18 and the motors turned in the correct direction. For me, since I am a bottom feeder, the left motor turned CCW and the right motor turned CW.

This thing is amazing! Before calibration, my distance between cuts 1 and 2 was 75 9/16" and between 3 and 4 it was 75 6/16".

I finished x-y calibration!

Now I have to cut my real sled and attach my Z-axis.