Delta Calibration with mini IR probe

kraegar

More details about my printer.

SeeMeCNC Rostock max v2, with their injection molded carriages & ball end barbells. I just installed CF arms from tricklaser, they measure 300.15mm according to tricklaser. I don't know of a great way to precisely measure them, but they do match up and using a common tape measure they appear to be right at that. Aluminum effector platform, again with the seemecnc ball ends. 80 steps/mm belt driven.

The pattern of the high probe height at each tower, and negative number opposite each tower is really odd to me.

kraegar

Updated to 1.17b, ran an 8 point calibration.

Diagonal 300.150, delta radius 143.937, homed height 373.250, bed radius 150.0, X 0.463°, Y 1.232°, Z 0.000°
Endstop adjustments X0.66 Y0.63 Z-1.30, tilt X-0.94% Y-0.28%

Z Z/Y Y Y/X X X/Z Z.5 Y.5 X.5 C mean deviation
0.280 -0.225 0.234 -0.215 0.260 -0.2 0.015 -0.002 0.019 0.019 0.018 0.183
0.255 -0.237 0.209 -0.227 0.235 -0.2 0.015 -0.002 0.006 0.007 0.006 0.177
0.243 -0.237 0.222 -0.227 0.235 -0.2 0.002 -0.015 0.006 0.007 0.003 0.176

dc42

Are you certain that you have entered the correct rod length, as measured between bearing centres? What sorts of bearings do you have, and how are you measuring the rod length? Do you have equal bearing spacings at top and bottom of each pair of rods?

It might be interesting to try 7 factor calibration and see what the firmware thinks the rod length is.

kraegar

I don't have an accurate way of measuring the new rods, as they're much longer than my calipers.

Earlier I had run a 7 factor calibration, and it said they were ~304.5mm, instead of their 300.15 as sold.

They're not bearings, they're ball ends: https://www.seemecnc.com/collections/parts-accessories/products/replacement-ball-joints

The specific rods I got are these: http://tricklaser.com/Carbon-Fiber-Tube-Arms-with-Ball-Cup-Rod-Ends-ARM-BC300.htm

And, unfortunately, the bed on my printer isn't long enough that I'm meeting the "probe well outside the printable area" to get a good measurement on the arms using a 7 factor calibration.

kraegar

Running a 9 factor calibration today, it gives a diagonal length of 310mm. I'm sure they're not that long! (Using a common tape measure and eyeballing it, they're right at 300mm)

(Just to check, from a clean start, a 7 factor calibration also says 310mm)

kraegar

Just for grins, here's a full 9 point calibration result, after 3 iterations:

Diagonal 308.484, delta radius 146.441, homed height 373.347, bed radius 150.0, X 0.146°, Y 0.756°, Z 0.000°

Endstop adjustments X0.30 Y1.24 Z-1.54, tilt X-0.23% Y-0.31%

Bed probe heights: 0.002 -0.002 0.025 0.007 0.020 -0.022 -0.028 -0.014 -0.015 0.069, mean 0.004, deviation from mean 0.027

kraegar

A couple notes:

1 - I resolved the majority of the tilt. It was actually the hotend not sitting level in the groove mount, and since the probe is attached to the hotend… tilt. Didn't take much for it to be off.

2 - I'm also checking with a different probe type now (accelerometer & tapping the nozzle on the bed) and still seeing the same "high at the towers, low opposite" pattern going in the results of an S-1 check after a few rounds of auto calibration.

3 - The amount of error is worse with the longer (300.15mm) CF arms than with my shorter (291.6mm) injection molded arms.

4 - in both cases, if I put in the arms are longer than they are, the error reduces greatly, and can nearly be negates.

5 - Swapping the "barbells" around between positions, or from the carriages to the effector, or switching the location of any of the pairs of arms has zero bearing on this pattern.

kraegar

Testing dimensional accuracy, the 300.15mm arm length for the CF arms (as sold length, and looks accurate by eyeing them) gives dimensionally accurate prints.

dc42

I suggest the following test:

1. Run 6-point auto calibration. Print 2 parallel lines, from one edge of the bed to the other, one half a bed width to the left of centre and one half a bed width to the right. Then test them for straightness with a ruler.

2. Do the same, but this time run 7-point auto calibration first. RRF will adjust the diagonal rod length to even out those height differences.

What will be interesting is which test print has the straighter lines.

Is the 300mm length quoted for the new arms measured between the centres of the balls?

kraegar

Here are the prints:

S6 Calibration:
Endstop adjustments X-0.24 Y1.37 Z-1.13, tilt X0.00% Y0.00%
Diagonal 300.150, delta radius 144.174, homed height 373.490, bed radius 150.0, X 0.126°, Y 0.565°, Z 0.000°

http://imgur.com/GRw04H4
http://imgur.com/sqU84ne

S7 Calibration:

Diagonal 310.832, delta radius 147.461, homed height 373.605, bed radius 150.0, X 0.103°, Y 0.586°, Z 0.000°
Endstop adjustments X-0.26 Y1.37 Z-1.12, tilt X0.00% Y0.00%

http://imgur.com/Wdbz5C1
http://imgur.com/OeusmvF

It may be hard to tell from the photos, but the S7 calibration lines were bowed in the center, slightly curved.

kraegar

Here's a 250mm bed test printed with an S6 calibration. You can see it's thin at the towers, and matches the pattern I see in the S-1 test.

http://imgur.com/MjAIulh

kraegar

Oh, and the new arms are measured center of the pivot point to center, yes.