For those that were not part of the Kickstarter: Where to obtain the main motor/worm gear/encoder

Correct, you always want your CG to be below the center of rotation. A few people have played around with this and confirmed this point. As for how much below, I think the rest depends on how your setup reacts. Some people have problems with it tipping away from the work surface, a higher cg seems to help resolve this.

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Actually, you don’t really want it falling in either direction. You want the
chains (and therefor the linkage) to be at the Z CG

Yes, the CG changes as the router moves (in all cases, the motor is heavy), so
there is no perfect height. you want it in roughly the center of how the CG
moves as you are running the machine (not just cutting, but also with the motor
clear of the workpiece as you move from area to area)

If you have the connection to the chains too close to the sled, the top of the
sled will tend to pull away from the work

If you have the connection to the chains too far from the sled, the bottom of
the sled will tend to pull away from the work.

neither is desirable.

It doesn’t need to be exact, because you have the 18" sled to resist tipping.

Oops, I was thinking of the CG in the plane coplaner to the work surface. Yes, @dlang’s recommendations for the CG axial to the zaxis are correct.

Hi all!

I’m new here.
I’ve been very interested in this project so I decided to sort materials for myself in order to build it faster. I’m actually having a space problem now, to build the Maslow machine.

Anyway, I sorted this motors on Amazon Germany (I’m in Europe, namely Portugal):

And I bought a pair because they do seem to be the same as the originals: same dimensions for the gearbox, motor and shaft diameter.

There is only information about rotational speed: 27rpm so I’m missing:

Pulses per rotation of the encoder
Final gear ratio

Also I could only find 6 mm pitch chain and 13 teeth sprockets.

I got last week the Maslow shield so I connected the motors to the shield/Arduino and tested with Ground Control. The “Test motor/Encoders” button returns Passed for both X and Y motors.

My questions are:

Will I be able to configure the firmware for different teeth number and different chain pitch? How do I do that?
Is there a practical simple way to determine correct pulses per rotation and final reduction ratio for an unknown motor?

Thanks for your help.

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Yes you should be able to use the chains and sprockets that you purchased.

is there a datasheet with the motors when they arrived?

for the final gear ratio, you would have to count teeth, for the encoder, we can
start with guessing that it’s the same and it should be pretty obvious if it’s
not (and we can calculate this out)

Olá LuisP e seja bem vindo!

Yes, there are settings available in the GroundControl software on the Settings panel (or is it Advanced Settings?) for the number of sprocket teeth, chain pitch and pulses per revolution for the motor.

The Wiki has some good info about this type of gearmotor here. There has been much discussion about the gears themselves here.

@stuartri posted some good pictures of ‘counting the teeth’ here.

Finally, if you do decide to ‘count the teeth’ on one of your motors, @mcmiley has a good word of advice here - “A word of advice to anyone taking one apart, make sure the front plate of the box comes out of the bottom of the box, otherwise you’ll end up with a lap full of cogs and silicon grease.”

Adding information to the project about making other motor gearboxes work will help others in the future, let us know what you find and how it is working for you. :smile:

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Hi dlang,

Thank you for your answer.
There was no datasheet. There are some pictures in the Amazon link. One has to do with the encoder signals with a table that I don’t understand:

Could Dmm be the motor diameter, which in this case is 36 mm, meaning that p/rev is 16?

There is also a picture of the wire connections:

Important remark:
Comparing this picture to the shield connector information on the wiki, one can see that the power supply wires for the encoder are inverted. I did invert the blue and green wires before testing and it worked ok.

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Hi blurfl,

Thank you for your reply. I will certainly follow this links before attempting to open the gearbox.

I couldn’t actually find the location on GC to adjust sprocket teeth, chain pitch and pulses per revolution.
On Settings I saw a Z-axis pitch parameter but nothing for L and R motors.

I don’t know what they mean by Dmm either.

but once you have it running, if you run it the number of pulses that we think
should turn the sprocket one revolution, if we are wrong, it will be very
obvious, and we can calculate what the right value is. So don’t stress over it.

Sorry for the misinformation. It’s in the Advanced Settings section. Once you have the ‘Maslow Settings’ page open, click on the title bar ‘Maslow Settings’ to see a drop-down list of other settings pages. The Ones you want are the first three on the ‘Advanced Settings’ page.

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Teeth count for this one is:

Worm gear: 2:25
2nd stage: 10:35
3rd stage: 9:29
4th stage: 17:36

Which makes the final ratio: 1:298:5294

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For an interesting exercise, grab the current version of GC and look at the Automatic Chain Calibration. It allows you to command a motor to turn 1 or 5 degrees. You could check your encoder steps value using that (72 clicks on the 5 degree button might get tiresome, though :grin:). It will use your sprocket teeth and chain pitch values to do the calculation, checking all three.

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I configured Steps per rev with 8358.82 which corresponds to 7*4 pulses per rotation.

I tried 90 clicks because there is only 1º step button.

It seems to have turned the expected 90º. So I think we can conclude it’s 7 pulses per rotation on the motor shaft.

It makes a bit of noise though, until the motor settles on the next position. Is this normal?

Yes, that’s normal. I think its a two-second settling for the PID loops. Of maybe its’ the motors grumbling about having to stop :smile:

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If your GC version only shows 1-degree steps, its out of date. 1 degree is not actually 1 degree in that version. Get the latest GC and FW (1.02) and try. It uses the number of teeth in the sprocket and the chain pitch to calculate how much to turn, so it should work better for non-stock designs.

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I downloaded this file: GroundControl-Windows.Portable.v1.02.zip

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You also need the firmware as well. https://github.com/MaslowCNC/Firmware/releases Get v1.02 (latest) to match your GC.

For the firmware I downloaded this one (on the 6th/Jan): Firmware-1.02.zip.

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These motors I’m testing are also available on Amazon UK:

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My motors seem to be running in the opposite direction.
What should be the normal procedure in this case? Swap positive and negative together with signal A and signal B from the encoder?