What must be adjusted to correct out of round circles


After my Aug 28th post, I wanted to do a couple of signs, thinking that they would be relatively easy, and also to show my wife that the Maslow can actually do something other than endless calibration. Well, when the machine is doing pocket cuts. I noticed the sled doing a lot of “bobbing” up and down, rocking as the machine made sudden movements up and down the workpiece. This caused uneven cutting depths. @dlang had commented from a photo I posted that the ring was too high on the sled.

I felt that if the sled was balanced, this would not be a big deal. Of course, David was right. Because of the way I had added my beam, I needed to mount the motors forward on the beam so that the chain cleared the mounting brackets. and to get the chains parallel I needed to raise the ring. So, this issue needed to be addressed. In my mind there was no practical way to change the beam mounting, so I “packed out” the board mounting area to raise the workpiece, adding 2x4’s on all vertical and horizontal board mounting areas. This raised the workpiece 1.5", and made my Maslow even more solid (and heavy!)

With all the turmoil over how folks are going to get kits, parts, etc, I have been getting a few key items so my baby can keep running (spare motor, Router parts). @Bee’s Blue Smoke Herder seemed like a good way to go for back up electronics

so I ordered the Option 2 Maslow Brain (Sheild and Arduino Board, along with enclosure and cooling fan). It arrived just at the time of the frame upgrade (Brandon is finalizing the enclosure and fan, so that is yet to come). The board is too cool to be a back up, so it was installed, V1.21 firm and software was enabled, the ring was lowered, and on to calibration.

To get to the August 28th Calibration, I used the Maslow chain measuring tool to ensure that my new chains (for the new 12’ beam) matched in length (they do). But my steel rule measurement was 13mm longer than the machine’s. I felt that if I got the machine’s number to the correct result, all would be good. So I adjusted the Chain Pitch from 6.35 to 6.37 (getting there was half the fun) and got the machine to agree with my ruler. After a couple of “Triangulation Test” cuts, the following was reported by Maslow, which led to the Aug. 26th result:
Distance between Motors 3605.72
Vertical Offset 578.6
Rotational Radius 136
Chain Sag 42.649137
and the following Benchmark result

Fast forward to the last couple of days…
Using the Manual Calibration process, the ablve values were entered, except for the Rotational Radius, which I changed to 139.1 (the consensus “correct” value). The results were pretty bad…

Ran the Maslow chain measurement, along with confirming my steel rule number, and found an additional correction was needed, which took my chain pitch adjustment to 6.385. Went through the regular calibration process, and got the following numbers after a couple of Triangulation Tests…
Distance between Motors 3606.09
Vertical Offset 556.8
Rotational Radius 126 (Yikes!)
Chain Sag 43.186239
and the following Benchmark result

Deep in the weeds, I retreated and re-read @madgrizzle’s piece on Maslow Precision and Accuracy

This is a MUST READ to get some kind of understanding about how the system works. Also follow

to get an picture about how the calibration software works, and an innovative new approach to the process (a work in process).

From the Accuracy article, “If the controller thinks the motors are further apart than they are, then it will feed out too much chain and will make the vertical distance of your cuts lower, wider, and actually shorter than it should”. For sure, my long vertical measurements have always been too short, and when I made my Paulk Workbench (early version of machine)

the long horizontal cut at the top did just what the simulator shows, bow down.

And from the “Holey” article, that the Maslow calibration uses the Rotational Radius value to correct other problems. The fact that my Benchmark long verticals are short, and the Rotational Radius is radically adjusted smaller, leads me to believe that the Maslow is sending out too much chain. Measuring 10 links of my chain in several places, it was clear that my chain links are pretty close to the correct size of 6.35mm.

So, the chain pitch was reset to 6.35, and I ignored the discrepancy between the machine and steel rule measurement, used “hard” measurements in the manual calibration routine for Distance between Motors and Rotational Radius, and the latest Vertical Offset and Chain Sag values…
Distance between Motors 3606.09
Vertical Offset 541.338
Rotational Radius 139.1
Chain Sag 43.186239
Set the chain length, ran the Triangulation Test, and got the following:
Distance between Motors 3606.09
Vertical Offset 579.4
Rotational Radius 145.4 (again, YIKES, but…)
Chain Sag 10.826962 (smallest number ever seen by me)

Ran the Benchmark Test, and got the following

Which is probably the best result I have ever gotten, especially the long verticals. I ran an 18" circle, but my test board is not real flat, so it did not cut everywhere… But where I can measure it, it is the prescribed 18" diameter.

So, at least for now, I am happy!