Here's the three versions I when changing my bed.g for my delta printer. They use 32 points and it generates a column that I can cut and paste into my bed.g It works for me, my calibration runs in the 0.01 mm range. Feel free to make a copy and do whatever you want with it, I'm just sharing in hopes of it being helpful to someone. Please watch the printer carefully until you're confident it's working for you, while it works for me I'm just throwing it out there to help and don't make any claims to it working flawlessly although I can't see how it'd go bad if you use values reasonable to your machine.

Variables to change are:
-bed size (the outer ring of probe points)
-Calibration Factor
-Oversize factor (only on the oversized one where I use it to dial in my arm lengths)

The first one is my default arrangement
12 points at the bed size distance (perimeter), 12 more at 2/3 the bed size distance, 7-points at 1/3 and one for the center.
https://docs.google.com/spreadsheets/d/1trfFyw2LqvRUeq3WPKtEaKaRGZOVwk4034zErVPo3jE/edit?usp=sharing

The second arrangement I get better calibration numbers from
16 points at the perimeter, 12 inside (2/3 distance), and 3 points (1/3 distance) and a center point
https://docs.google.com/spreadsheets/d/17S-CsZrUSqeNFooCKBznFLhmKTVUeivGca3umMWm86s/edit?usp=sharing

The third is what I use to test / calibrate my arm length. I calculate the oversize factor as the distance to just inside the maximum bed radius over the bed size parameter that I can test within the limits of the towers. Please be careful and watch closely if you use this one.

https://docs.google.com/spreadsheets/d/172jtcU9UQyQi1yUPvm9tagQ7Fl1T8Yxcv_s8HN2PATI/edit?usp=sharing

I will try to update if there is a major flaw, otherwise please treat it as a starting point for you play with generating your own test points.

depending on the repeatability you want, you may want to slow the feedrate which is really because of the worst part of inductive probes. Most inductive probes switch at 500hz until you you break the ~$60 retail price point for industrial sensor to get 1khz to 3 khz ( next price point is like ~$150+ and specs can get to 5khz). So the faster you're probing the larger the distance variation between trigger intervals. i use a ie5390 i grabbed off of ebay for like $30 and it operates at 1khz and i go with 60mm\min to get .003mm repeatability which is only a microstep and it levels (delta printer) to .01mm over a 300mm probe area

@Danal I use the same Motors on my Rostock max for years now and they've held up quite well for the abuse I did on them. I have looked for lower inductance / inertia 0.9 steppers with good torque but I haven't found one I'm confident will perform better for a decent price (I'm looking at you moons' industries...)

If you get a chance, test out my settings I scope tuned for the motors. Mine run 1500ma without getting hot and are as silent as I can expect of them.

https://forum.duet3d.com/topic/13028/my-tuned-tmc2660-settings/2

Following the trinamic tmc2660 manual and spreadcycle guide I busted out my o-scope with a current probe and a helping hands on the sense resistor. The motors I tuned were Wantai 42BYGHM809 and a PG35L-048. I run a delta, and my steppers are running at 1.5 out of the specced 1.7A and they are staying significantly cooler than when I tuned by ear and they are behaving much better for me, it even got my past the .02 bed leveling barrier I was at.

Anyways, thought I'd share my efforts in case it might help someone.

Wantai 42BYGHM809
M569 P0 D2 F2 B2 Y01:09:02

PG35L-048
M569 P3 D2 F3 B3 Y03:07:02

I prefer the contactless approach and just wire in (directly with no extras has worked fine for me) A3144 digital hall effect sensors (~$1 ea.) for my endstops and slap a magnet on the moving part. You can home fast and do a slow back and return and the repeatability has been hands down better over time than contact switches I've tried.

I finally cleared this up on my E3d titan, had moire patterns like the second picture first post. I eliminated the software/ electronics ( changed stepper driver settings, each value individually although it was on the fly during 10mm test towers, and even purposely bad ones), motor current, microstepping high and low, thegolden ratio layer heights, extrusion/flow rate,slicers, motor cables. It confirmed what I suspected in my case which was that it was hardware and top of the list was the titan itself.

I don’t know what fixed it specifically since at that point I wasn’t doing that many disassemblies. I reprinted the motor mount and sanded to try to keep things perpendicular. I drilled out the the old titan cover plate and added a copper sleeve to the motor shaft intending to constrain shift alignment and any deflection from the tensioner. I had lots of spare parts since I swapped everything on the titan but the main body. When arranging the gears, I adjusted the delrin gear on the hobb so the tensioner arm was as close to perfect feeding filament into the center of the hobb. When I was doing that I noticed the both delrin gears had slight issues, one didn't sit perpendicular on the hobb when looked at with an engineer square ( I used it a on anything I could to see who my culprits could be for not being perpendicular when they should) and the other was not truly flat when viewed against the straight edge. Fixed one up and put it in and noticed when I was trying to get the gears flush to a razors edge (literally) that the hobb gear wobbles weird in it's bearing. So I swapped out the hobb's bearing in the body of the titan, (the one in the cover was checked too). I also added so kapton tape where the v6 mounts into so there is zero play even with effort. I finished putting it back together and one or a combination of things fixed it. Going to a hemera was my next move if I didn't get rid of it here, if only for the on motor mount points for my probe and and flex filament performance.

My gut says based on the pattern, it was likely the fact that the gears were not perfectly in line (seriously, I couldn't tell other than the bearing until I got out my good square) and wobbling during rotation either due to the motor shaft not being perpendicular for the metal gear, the delrin gear not being truly flat / crooked on the hobb, or less than stable bearing the hobb gear rode in. With the hemera you have a few parts you out together that could be the source, and it makes it even harder to identify since a few critical ones are small and short so perpendicularity of shaft to gear and round and centered of the rotating parts will Tedious. Still you could get by simply with A printed jig and dial indicator along with some squinting at the part on a engineer / machinist square or at least straight edge in front of a light. .

@fcwilt I got a few of the 10 to 12 mm ones off of amazon and they did fine, until I went down the number chasing rabbit hole. The LJ8/10/12's are all 500hz switching, so you can expect them to vary about +/- 0.033 mm in their response (not including things like microstepping) if you run the feedrate at 1000mm/min. With that though, you'll at least know when it's the switching time or mechanical play which is perfectly usable and still better than I've gotten out of physical switches. For physical switchs, oddly the best repeatability I tested was actually a switch I pulled from a spare sanwa arcade button I had, much better than a limit switch although definitely not as rugged. Makes me want to test a cherry MX red mechanical keyboard switch as a probe when I think about it... I think playing with delta's for 7 years is starting to show....

note: the field coming off the induction probes are typically two lobes (oblong spheres) which isn't labeled in any way. The detection pattern for most of the useful distance would plot in an oval or even a peanut shape, which isn't an issue for their typical use (and why the detection object is usually specified as at least the diameter of the probe). This means the probes will be more sensitive to tilt in some arbitrary axis (well, where ever the center line between the two lobes is) compared to a corresponding perpendicular axis. TL;DR being do you best to mount it as perpendicular to the bed as possible it'll carry the tilt into the measurements like any other probe (and if you're a number chaser like me, incorporate a locking ball joint in the mounting).

I got fed up with something retraction related in Simply3d. So I did some test prints in Kisslicer and Cura (cura definitely has some odd quirks when it comes retraction though...) and the diagonal cross hatch lines that plagued me are smooth as silk in the Cura prints. So I just wanted to put the reminder to rule out slicer quirks occasionally when hunting this down.

Looking at the long spans on the belts remind me of another issue I had (I run a delta though). The constant tension on the motors eventually affected the bearings in the motors. I eventually replaced the motors, but I also added in thrust bearings* between the pulley and the motor, so any lateral pull on the motor shaft is limited by the pulley pushing down on the thrust bearing against the motor. Granted the motors were also like 7 years old so they did good. Still, I'd at least consider these since they are easy to replace, inexpensive, and they worked great for me removing a visible deflection in the motor shaft when the belts were tightened. Tuning after that I tuned for better jerk and accel, but that could have been the motor model changing. Still, these did have noticeable improvement on the hash pattern for the old motors before I replaced them, but the artifacts were not fully resolved until I changed slicers. I had to format my computer recently and didn't deem those pictures as worthy of backup....heh.. and it's kind of hard to describe how it changed to a kind of fainter or less pronounced but crisper or finer lines at the same time.
*- https://www.amazon.com/gp/product/B07QKKYKR8/

@fcwilt Please leave a post with your findings. I use a IE5390 I got off of e-bay for $30 (normally $93), which switches at about 1khz. Seeing the results from higher switching sensors I'd find very interesting, but not so interesting as to see my wife's response to me buying multiple probes to test thoeries...

https://www.ifm.com/us/en/product/IE5390

So... I'm going to go ahead and eat my words here. I checked the profiles by squirting some hot glue into a section and pulling it when it cooled. This let me compare the tooth profiles much better than by trying to peer down in them and judging from a reflection. Overall they were shaped fairly right. Issues I found though: I measured one set (black anodized aluminum) they were about 1mm small on the OD for the belt and the lowest OD was often next to a set screw hole ( consistency suggests it's likely an issue in the manufacturing process). Even the ones that appear like gates ones in every way and had the proper OD, they had sections that when moving set calipers along the OD the calipers would catch near the flanges, basically a straight section was essentially a very squashed U shape only flat in the middle. This occurred among a few out of 3 different sourced pulleys.

I can handle the $13 for powergrip GT3 pulleys from misumi, so I think I'm going to do that for my sanity. This was a fun exercise in giving my gut instinct the bird though

@Phaedrux Yeah I can't find anything obviously off with mine, so it really is just to write it off as good in my mind.. The $20 for an aluminum pulley hits some part of my brain that screams no, buy 30 for the same $60 and pick the best 3 and you'll have spares to play with, thats why I got so many spares.

Anyone have any good methods to verify the quality of your pulleys? Installing each one into my delta is too much, but slapping a motor onto a spare extruder driver and testing them quickly seems reasonable to me. I just want more concrete ways to check things like eccentricity or how well the pulley teeth profiles are meshing with my belts (I got spare belt lengths to test with).

For eccentricity I've thought of just propping up the end of a laser pointer on the pulley and watching the amount the laser point travels on the wall across the room as the motor spins the pulley. My thinking is any eccentricity should show as a repeating vertical movement distinguishable from vibrations and it wouldn't be to bad to sort through my pulleys like that. One possible issue though is the retaining walls don't necessarily match the tooth for roundness although it should in a quality pulley...

I'm still stumped on a quick and easy way that is quantitative in some way to check the profile fit or issues.

@fcwilt Yeah, I figured you'd need a custom bed.g to avoid the magnet locations but never saw anyone say anything about those systems with inductive probes, which kept me from swapping out my PEI covered aluminum disc for a flex (works good enough until I abuse the sheet too much). At least it's easy to generate a custom bed.g just don't go over 32 point (including P0). I posted my google sheet's of mine I did for delta's, but it'd probably be easier to just make one for a cartesian from scratch.

https://forum.duet3d.com/topic/14871/sharing-my-delta-bed-g-spreadsheet?_=1605991873564

@fcwilt Please leave a post with your findings. I use a IE5390 I got off of e-bay for $30 (normally $93), which switches at about 1khz. Seeing the results from higher switching sensors I'd find very interesting, but not so interesting as to see my wife's response to me buying multiple probes to test thoeries...

https://www.ifm.com/us/en/product/IE5390

@Bewaren Recently swapped to Cura, was using S3d before but I found that was one of the causes of my surface patterns.

Yeah... don't know squat about prusa slicer they do things a bit different. They got lots of modifiers and settings that can override perimeters on things like holes (local strengthening, volume modifier, and probably more). I tried looking at Prusa slicer's features and I had a flashback of the frustration I had with Cura in our definition of terms and how things should be related don't match up all that often when it comes to specifics.

@Bewaren That's typical for any printer, you calibrate based on straight lines, so when you start doing a tight curve the inside of the line is basically squished and the outside stretched, making excess material push toward the center reducing the hole.

A common method and the easiest when you made the model yourself, is to address this in the model by adding some tolerance. Since the behavior should be consistent (it sounds like it is for you), at least for horizontal laying holes and vertical ones may be different from those but still the same to each other. For vertical printed holes there's also a technique to make them oval shaped in the model to get circular results in FDM prints. In openscad I leave a variable on hole diameter's (usually named fudge since it's my fudge factor), so I can just set that to add .2mm or whatever to give the clearance I want to all the holes for how the printer is presently behaving.

Cura (and probably other slicers) has a setting to compensate the size for holes as well.

I used kisslicer originally, and compared slicers often ( I had more free time). then during the dark times before its V2 update I swapped to S3D originally thinking they'd be diligent in feature updates ( they didn't and then teased a big update for another purchase... ha). I stopped using it and swapped to cura after testing slicers again a couple months ago when the faint moire / salmon skin that has plagued than i wantme for many upgrades straight up disappeared.

I have a complicated relationship with cura though. We have differences of opinion on what some terms mean, and for all the shiny features and options it has the lack of fine grain control it offers hurts my soul. It just "calculates" more things than I want it to. Example: I tell you cura what the line width I get at a layer height and you determine the infill spacing from that, I don't need it to be a redundant flow rate multiplier that you already have as an option. I don't like having to either just crank up flow rate or try to predict if you'll apply overlap just to clear up infill gaps.

For your own sanity, do a decent length free air extrusion and measure it for roundness. I've chased a similar thing only to have it be that my nozzle had become oval shaped.