Fully Calibrated but Oblong Circles

Regarding the separate chain tolerances, how would that be calculated? For instance, on the left side, the ruler-measured distance is now 3006.012, with the Maslow measurement at 3001.8 I am assuming the value would be entered into the Chain Tolerance section for the left chain. And, what value should be used for the motor spacing? Seems like it would need to be the actual number.

do the motor spacing measurement twice, once with each chain. Each time you also
measure manually (the manual measurement should be the same if everything is
going right :slight_smile: )

Then you calculate the error between the measurement-by-chain and
measurement-by-tape for each chain, enter the tolerance for each chain.

Then if you re-run the motor spacing measurement, you should get the same result
by chain as you do manually (using the tolerance for the appropriate chain)

That is the motor spacng measurement you should enter.

This change made adjusting the 12 O’clock position impossible (large
movements, often in the wrong direction.)

Explain this more, tolerance values should have no effect on rotating the
sprocket to the 12 o’clock position.

David Lang

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This tidbit needs to be in the wiki if it’s not!

Regarding the “12 O’clock” adjustment problem, I entered the error percentage calculated as the first physical measurement (3009.9) divided by the Maslow measurement of the left chain (3001.9), getting (1.002365)… Used this value in the chain tolerance section for both left and right chains. After doing this, when trying to rotate the gears to get to 12 o’clock, they moved several inches with each click, even with the 1 degree buttons. When I reset the chain tolerances to 0, this problem was fixed.

David, how is the tolerance expressed? For instance, if the Maslow says the spacing is 3001.8 for the left motor, and I measure it as 3006.02, the error is 4.94mm… As a percentage, 4.94 / 3006.02 = .00164337
.1643%? because the Maslow is less that the measurement, I am thinking it should be positive?!?
If it were the other way around (Maslow larger than the measurement), would it be negative?

I don’t think there’s a valid reason for the chain measurement to be larger than
the measured amount.

Correction… the man-measured motor spacing is 3006.012
3006.012 - 3001.8 = 4.212
4.212 / 3006.012 = .00140119
1.00140119 x 3001.8 = 3006.0061, pretty close to 3006.012
So, for the left chain, use the 1.00140119 (or just .00140119?) as the left chain tolerance, and use the Maslow to remeasure this chain, hopefully getting the correct number.

Doing all of the above, the chain pitch would be returned to the default 6.35, right?

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Is the 3006.012 measurement under tension? Are you measuring this at the same time as the Maslow measurement?

No, I am not measuring while the system is under tension. I imagine there might be a slight change, but I see no flex in the 2x4. When I built the frame, I attached a 8’ x 6” x 1/2” piece of particle board across the top edge of the 2x4 to keep it from flexing. In the interest of precision, I see your point… how long do you think the system can sustain the tension. Not sure I am comfortable messing with the tape while all this is going on. Have you done it?

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I have not tried it. I am in a similar boat as you and wondering the optimal way to measure. On an 18" circle I am measuring 17 7/8in horizontal and 17 27/32in vertical

I’ve not been involved in the development of this, but based upon my read of the code, you would enter it as a percentage. So for 0.00140119, you would enter 0.140119. The code divides the value you enter by 100 and adds its to 1 to become a multiplier. So 0.140119 would become 1+(0.140119/100) = 1.00140119.

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Cool! I will give it a try if I do not hear anything better to do. Thanks for checking for me!

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Regarding the manual measurement of the motor spacing, since I am presently in Limbo, I checked the distance from the gearbox casing to the center of the drive-shaft…

IMG_9912

I am getting 27/32" or .84375"… x2 = 1.6875", or 42.8625 mm

This makes my motor spacing now 3043.5495.

With the Maslow measurement of 3001.8, the error has dropped to 1.7495 mm for the left chain, and 6.3995 mm for the right chain,

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you want to measure under tension to be testing apples to apples, the system
should be able to sustain the tension for days without problems.

The sled was in place when I did the measurement.

Thanks!

Question about your measurement of 42.86mm. So I using the drawing found from vendor, I previously calculated this number as (11.15 + 9.05) * 2 = 40.4 Which is a bit off from your number. I haven’t actually measured mine, but how confident are you with your number? I will measure mine tonight.

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

Hi LakeWorthB!

At this point I am pretty paranoid about all measurements. I am operating out of boxes in my shop, as I hope to build some cabinets using the Maslow, but I found my caliper measuring tool yesterday, which is pretty accurate. What you see is what I did with it, first clamping a flat piece of plywood to the outside edge of the gearbox to anchor one side. I repeated the measurement on the other side, with the same result. The challenge is trusting the eyeball… I looked around for the source of the 40.4 measurement on the forum, couldn’t find it, so I measured it. If I had found your post with the part diagram, I would have gone with the 40.4 value. Now that I have seen it, I have gone back and checked… First I plugged the measurement from the drawing into my caliper… 20.2 mm = 51/64"…

During the process, I noticed there is a center mark on the spindle… I remeasured to that mark…

So, my initial measurement was off… It is 13/16", or 20.6375 mm. So, measuring outside of motor to outside of motor, the correction for me will be -41.27 mm

I do take this stuff seriously… I apologize for the error. Sadly, it won’t be my last.

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And we all benefit and appreciate it!

I’m still tracking down what’s going on with the chain distance measurements, I know what’s happening, but not why yet

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Alright, just last night I was able finally button up all the changes I needed to make to my Maslow. I adjusted the CoG on the sled, I changed the tensioning system and got new stretchy string, beefed up my top beam, raised my motors up another 1.5 inches, and got all updated to 1.15.

We all know I had some issues with out of round circles and my first test cut after only 1 calibration finally came out ROUND! I didn’t even adjust the chain pitch tolerance yet or put my new ring sled on the machine. I wanted to prove to myself that it was an issue with my build.

I am working on a little project right now that I hope I have the time to cut this weekend and then I’ll post it. Just wanted to say thank you everyone for the help!

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I don’t know if this will be any help to anyone, but I just put this on thingiverse based off roselea’s design. I moved the holes, redid the sprocket hole so on my printer with no scaling it fits the sprocket perfectly with 0 play, and added a slot for a tape measure to sit in, slightly offset so that the inner side of the L thingy on the tape will be perfectly centered on the spindle. I was having a hell of a time measuring my motor distance on a 12’ beam that is really high!

Should really help measure motor distance accuretly. I am printing 2 so i can measure to the slot on the other end too, so long as i turn the second print 180 degrees before putting it on the sprocket, it should be 100% accurate. Shame my eyes not that accurate :slight_smile:

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Awesome! I have been using a framing square, this will help a ton! Thanks!