# Ideas for 3d printed part to measure between motors?

I have seen some 3d printed parts on here to align the sprocket to exactly 0 degrees, but after just running through this part of the calibration routine for the first time yesterday, I feel that it would be easier to figure out a way to just use a tape measure to make this measurement, with the help of a 3d printed jig. Here are some ideas, any thoughts?

1. A Part that would slide on to the sprocket, and has a tab on top right over shaft that allows a tape measure to fit in. Its twin would go on other side, and you would use tab as guide to where to measure. Might still have problem of having to line up sprocket to 0 degrees, but maybe less critical.

2. Part that has same tabs to hold tape measure as 1, but instead hooks onto edge of motor, or even uses motor mounting screw.

3. Easier now that motors horizontal on beam, but just measure from outside edge of each motor, and calculate the difference between that and shaft.

5 Likes

I think this is a great idea. In fact, if we trust the tolerances of the motor gearbox (likely significantly less than the tolerances in a tape measure) we could use those as the reference edges and get accurate distances from the edge to the motor shaft center.

(Your #3) Just hook the tape measure to far side flat edge of the gearbox, then measure to the far side of the other gearbox and subtract the known distance from shaft to edge and there you go.

Could go one better to confirm and measure to the inside and outside of the right motor minus the offset and average those two distances.

I like it.

5 Likes

So according to the drawing https://etonm.en.alibaba.com/product/60665360361-803643106/ET_WGM58AE_with_7PPR_encoder_12v_20_6rpm_30kg_cm_CNC_Machine_dc_electric_motor.html?spm=a2700.8304367.0.0.PlKjgw It is 20.2mm from center of shaft to edge. So if you measured from one edge to another you would subtrack 40.4mm from the total. I will give it a shot tonight and see how it compares to the calculated motor spacing using the chain.

5 Likes

This is a great idea. I will give it a shot as well to see how our answers compare

1 Like

I will give it a shot myself. I have, what I believe is an issue with my chain pitch. This could actually help other folks check theirs.

1 Like

I did a quick measurement and from outside to outside my measurement was 3049.5mm so if I subtract the 40.4mm from that total I am at 3009.1mm.

With my chain pitch at 6.359mm my automatic motor spacing comes out to 3009.86mm. Pretty close actually. Based on this I might bring my chain pitch down to 6.3575mm, I think this way of measuring is probably significantly more accurate than estimating the center of the motor shaft visually on each side.

I will be interested to know if others find a discrepancy between their tape measure value and the automatic value.

2 Likes

It would be interesting to hear what using your manual measurement value with the standard chain pitch gives for the calibration benchmark.

2 Likes

I always see a difference between the two. It seems like itâ€™s the result of the very slight looseness of each link of the chain that allows them to pivot and this adds up over ~9 feet of chain to a few mm.

1 Like

Yep. In my case about 4.5-5mm.

@madgrizzle is your machine dialed in the way you want it? I think you had said not yet.

I need to get some time, like @blurfl said, run a test with the stock chain pitch and then my adjusted chain pitch. I have been rushing to put in a patio before my sonâ€™s b-day which has stolen much of my Maslow time.

4 Likes

From motor to motor, I measure 3048mm, then subtract the 40.4mm to get 3007.6mm. Compare that to my chain measurement of 3003.43mm for a difference of about 4.17mmâ€¦ Not too bad.

And thatâ€™s just measurement with a regular tape measurer, by myself (which was hard because of the width of the machine) I could have easily been off by a 1/16th or so. I couldnâ€™t exactly pull it tight either since nobody was holding the other side

3 Likes

Maybe I am wrong but, because that distance is so critical to all of the other maths for the calibration, it seems like those two better be within a few tenths of a mm. If not, then there is either an issue with the encoder steps (I doubt this) or the chain pitch is slightly different than 6.35mm.

As I mentioned, I looked up the length tolerances for the #25 roller chain and it was -0.0% / +0.15% so these would be within spec. Your results are actually very similar to mine, I calculate a chain pitch closer to 6.359mm based on your numbers.

This might be a measurement we need to take. The user could measure from outside to outside of the motors and do the automatic motor spacing measurement then internal to GC it could compute the proper chain pitch. I will defer to @bar and the other folks that came up with the calibration routine to confirm it is worth adding.

2 Likes

I had suggested on github that a calibration factor be added that, in essence, changes the chain pitch based upon what Maslow measures and what a user manually measures. I didnâ€™t get a response, but you can manually do it as you have been. Obviously, if the chain pitch under normal operating conditions is not exactly 6.35 mm, then results will be better using the correct value (as long as the â€ścorrectâ€ť value is used during calibration).

3 Likes

Sorry, I donâ€™t get around on GitHub much. So it sounds like you covered this and the work around is pretty straight forward. Maybe on a light coding week it can be added

different approach to the same problem: Calibration.

I believe that this is now supported under advanced settings.

I agree that we should make it a part of the calibration sequence, but letâ€™s give everyone a chance to catch their breath. It seems like 1.11 is a nice stable build, and letâ€™s enjoy it for at least a week before we rock the boat

4 Likes

Looks awesome! And nearly done. And I feel your pain on time constraints as my Maslow time is also being taken up by a project for my progenyâ€¦

Hoping to do some fun details with the Maslow

6 Likes

Oh man I can think of so many cool details to add with Maslow!

1 Like

Please, feel free to suggest. I have plans for gears to play with, a design for a rotating periscope (to look under the deck), some decorative ideas, etc., but I am always on the lookout for fun ideas to try.

4 Likes

I have yet to get my Maslow up and running, but, unless Iâ€™m misunderstanding, it seems that you could 3D print a little â€śshelfâ€ť for a laser distance meter, that would hit an identical (but mirror image) shelf on the other side. Another advantage of this is that it could be used to get the top sprocket exactly at 12 oâ€™clock with respect to the other sprocket. (getting the laser to hit the corresponding point on the other side would be very accurate alignment)

It would slide over the sprocket like a socket wrench over a nut. The left shelf would look like an â€śLâ€ť as you looked straight on, with the vertical at the centerline of the sproket. (right shelf would be a mirror image)

I have one of those laser distance measuring devices, and they are very accurate!

3 Likes

how accurate? you would be looking to get an accurate measurement to ~0.001" and
you have to mount your marks at least that accurately, or you are wasting it.