Any guesses as to discrepancy in arm length vs. measured arm length?
-
I had another look at data I collected yesterday and collected some more data today.
Yes, I agree, there is an influence of the springs, but I guess it is not very relevant.
What I did yesterday was checking probing speed / motor power vs. deviation of testresults.
So I did a log of G32 runs with S-1 to collect the data. I varied probing speed and current for the motors, I saw a big influence of the motor current with the default probing speed of F120 when choosing 1.5 or 2A current, but with the default of 1A there was not much to see at different probing speeds.
What is relevant in this context is that I measured the deviation of the results of each probing point, if springs have a huge impact that deviation in the points should be higher than the measured 5-7.5 Micrometers, shouldn't they? unless of course that because of the quite repetitive movement pattern the effect of the springs is always the same, but I kind of doubt that.
Today I also did some more measurements with moving the head arround and then probing x0 y0, here the numbers are also quite close:
Probe with moves on Bed Probe with moves on 60mm Probe without Moves 60mm Probe without moves 20mm 0.07 59.914 59.939 19.97 0.077 59.914 59.927 19.977 0.07 59.914 59.933 19.977 0.07 59.895 59.92 19.97 0.064 59.914 59.914 19.97 Avg 0.07 59.91 59.93 19.97 Dev 0.00 0.01 0.01 0.00 -
The effect of heavier sprints is to pull up on one corner of the effector at the point when it's between towers. This is easily observed - if you take a set of barbells off your printer and put your arms on them (with springs in place) you'll find the springs pull things into a square naturally. If you push it into a parallelogram, the springs will pull it back square. The weaker the springs, the less the effect. When your effector is beween towers the arms are in this parallelogram position, and the springs are fighting it. Something has to give. It flexes the outer arm - the longer your arms are, the more they flex, and it pulled up on that corner of your effector.
The effect actually is very repeatable and measurable.
If you build one of the effector tilt measurement probes I made, you can observe this effect in real time, and how much it tilts the effector on your delta. Info on that here: https://www.duet3d.com/forum/thread.php?id=1306
That said, the springs are NOT the cause of this issue, they just muddy it up and amplify it some. I'm running magball arms which don't need linkages or springs, and still see the "taco bowl" shape to my probe output.
Here's a brief list of things I've tried to diagnose this:
Seemecnc stock effector, 713Maker aluminum effector, custom aluminum magball effector
Seemecnc 292mm stock ball cup arms, Trick Laser 300mm CF ball cup arms, Haydn Magball arms (304mm)
Seemecnc Accelerometer probe, dc42 IR probe, Piezo Probe
Seemecnc injection molded carriages, Trick laser aluminum carriages (current version)And then I've also made the electronic tilt measurement, so I could measure and eliminate tilt in my effector to rule that out. (I have no measurable tilt at this point, either digitally with the accel/gryo, or with a bubble level).
I have loads of spreadsheets of data gathered, but have yet to find anything other than increasing the arm length that gets rid of the "taco bowl" shape.
Big clarification on that last statement: Several of these have reduced the issue. Anything that adds tilt to your effector seems to really amplify the incorrect measurement of the arm length. The biggest improvement so far was going to magball instead of arms with springs between them)
-
All, please bear in mind that I do not advise the use of 7 or 9 factor calibration. If you can't resolve the problem by using weaker springs or whatever, then I suggest you use mesh bed compensation to handle the residual deviation.
FWIW, my large Kossel with PCB effector and carriage adapters and Haydn's magnetic arms calibrates to a deviation of about 0.025mm using 8-factor calibration and AFAIR 13 probe points.
-
Thanks for clarifying that, David. I should say I only use a 6 factor calibration for actual printing, and enable a mesh for larger prints. I'm mostly just interested in this from a "puzzle solving" perspective at this point. Though the majority of my time is now invested in my corexy project.
-
So it appears that I got rid of my "ridges and valleys" problem.
I'm swapped carriage, effector, and arms to the following 325mm length ones from Trick Laser (I guess for a short while the 325mm length was in vogue):
http://www.tricklaser.com/300-MM-Carbon-Fiber-Tube-Arms-for-Rostock-MAX-RM-ARM-CFTX300.htm
The new arms narrow the "ridges and valley" problem down to either the arms being too short, the springs being too tight, or something associated with the movement of the newer ball joint arms.
I do have another pair of 300mm rods of the same style, so I will try those tomorrow to see if the results change or stay the same so we can remove or keep rod length as one of the contributing factors.
I'm running 6 point 140mm calibration with 6 midpoints all at the same H-0.10 FSR height. Deviation ranges from about 0.02 to 0.05, which seems to be good.
I did notice previously on the ball cup arms with springs, a ~0.05 deviation of layer height on very small circles (almost as if the springs were causing the effector to shift), so I may retry that calibration print on this setup and see if that was a symptom of the ball cup arms and springs as well.
-
There's been speculation between a couple of us that long enough arms paired with either very weak or no springs would end the issue, so your results are interesting. There have been people with Traxxas ends who've reported the calibration oddity as well, but your follow up test with the 300mm arms will be good to see as well.
-
There's been speculation between a couple of us that long enough arms paired with either very weak or no springs would end the issue, so your results are interesting. There have been people with Traxxas ends who've reported the calibration oddity as well, but your follow up test with the 300mm arms will be good to see as well.
I also specifically put the bands on the very, very end of the traxxis rods this time, nearly right on top of the joints around the plastic end pieces. That may minimize some of the warping of the carbon fiber rods. I might try with the bands in the very middle of the rods as well and see if I can maximize any warp effect from the carbon fiber rods.
I'll try to get the 300mm rods tested later tonight and post any visual results from printing the 0.2mm height large circle test.
-
Also, I'm tempted to try 360mm magball Hadyn's arms from Ultibots.
Any downside to having vastly longer arms like that? I would imagine the accuracy is slightly less for small movements, but I could perhaps offset that with 0.9 degree steppers.
-
The longer arms give up a ton of Z, which sucks.
-
Just posting some results for reference from a 22 point bed calibration, 325mm traxxis ball joint arms, and FSR sensor setup, using the past generation Trick Laser carriages, effector, and arms made for the Rostock Max v2 kit as upgrades.
Also, note how closely it calculates the correct delta radius (which is listed at 133mm).
[c]M561; clear any bed transform, otherwise homing may be at the wrong height
G31 X0 Y0; don't want any probe offset for this
M116 ; wait for all temps to reach set values
G28; home; 3 points at 140mm
G30 P0 X0.00 Y140.00 Z-99999 H-0.05
G30 P1 X121.24 Y-70.00 Z-99999 H-0.05
G30 P2 X-121.24 Y-70.00 Z-99999 H-0.05; 3 points at 130mm
G30 P3 X0.00 Y130.00 Z-99999 H-0.05
G30 P4 X112.58 Y-65.00 Z-99999 H-0.05
G30 P5 X-112.58 Y-65.00 Z-99999 H-0.05; 3 points at 120mm
G30 P6 X0.00 Y120.00 Z-99999 H-0.05
G30 P7 X103.92 Y-60.00 Z-99999 H-0.05
G30 P8 X-103.92 Y-60.00 Z-99999 H-0.05; 6 points at 75mm
G30 P9 X0.00 Y75.00 Z-99999 H-0.05
G30 P10 X64.95 Y37.50 Z-99999 H-0.05
G30 P11 X64.95 Y-37.50 Z-99999 H-0.05
G30 P12 X0.00 Y-75.00 Z-99999 H-0.05
G30 P13 X-64.95 Y-37.50 Z-99999 H-0.05
G30 P14 X-64.95 Y37.50 Z-99999 H-0.05; 6 points at 50mm
G30 P15 X0.00 Y50.00 Z-99999 H-0.05
G30 P16 X43.30 Y25.00 Z-99999 H-0.05
G30 P17 X43.30 Y-25.00 Z-99999 H-0.05
G30 P18 X0.00 Y-50.00 Z-99999 H-0.05
G30 P19 X-43.30 Y-25.00 Z-99999 H-0.05
G30 P20 X-43.30 Y25.00 Z-99999 H-0.05G30 P21 X0 Y0 Z-99999 H-0.05 S6
M500; Save print settings to config-override
[/c]Calibration console output:
[c]Calibrated 6 factors using 22 points, deviation before 1.810 after 0.019[/c]
And then the new config output is here:
[c]; This is a system-generated file - do not edit
; Delta parameters
M665 L325.000 R132.978 H332.047 B140.0 X-0.012 Y0.268 Z0.000
M666 X-0.491 Y0.820 Z-0.330 A0.00 B0.00[/c] -
The longer arms give up a ton of Z, which sucks.
So get longer verticals.
Deltas have massive Z dimension which I am sure almost no one ever uses.
-
Those are good #'s, Saffi. Makes me think I need to try some longer magball arms, just to see what the results are. Really didn't want to have to spend that money!
-
-
I now replaced the springs with rubber bands, pressure on the balls is a lot less now.
But this change showed close to no effect , the S6 and S8 results are nearly identical. One very interesting thing I realized was that the effector moves a little bit when I roll one of the rods arround it's axis, i did not expect that.
I also compared calibration with your points to the results with the standard config generated by the bed.g generator (both at 140mm radius):
Calibrated 6 factors using 22 points, deviation before 0.088 after 0.087
Calibrated 6 factors using 16 points, deviation before 0.103 after 0.102
The numbers are way off compared to yours…. sniff.....
I have a set of 304mm Haydn rods, will try those. Have now also ordered 360mm version of them from Haydn.
By the way, did the mounting distance of the rods/effector size change between the last generation tricklaser rods and the generation before?
And another question, it seems your bed is more or less the same size as mine (330mm), what is roughly the distance between the center of the bed and the ball's center on the carriages? Are there any rules for that?
On my printer this distance is approx. 190mm -
@MiR:
I have a set of 304mm Haydn rods, will try those. Have now also ordered 360mm version of them from Haydn.
By the way, did the mounting distance of the rods/effector size change between the last generation tricklaser rods and the generation before?
And another question, it seems your bed is more or less the same size as mine (330mm), what is roughly the distance between the center of the bed and the ball's center on the carriages? Are there any rules for that?
On my printer this distance is approx. 190mmThe Delta Radius for the old Trick Laser Carriages and Effector was about 133mm.
The Delta Radius for the new Trick Laser Ball Cup Carriages and Effector is about 141mm.The Rostock Max (at least the metal frame) has a printer radius of 200mm, it's referenced here:
http://www.tricklaser.com/Trick-Truck-X-Mini-Carriages-TTRUCK-XMINI.htmI'm considering either trying a 360mm set of the Hayden's mag ball arms or possibly a 360mm set of the ball cup arms - I'm curious if I can get a length long enough to compensate for the weird calibration of the ball cup current generation setup.
Or I could just wait on the PCB effector sets and go all out and put linear rails and mag ball arms all on at the same time for my gold standard build.
-
I have now mounted my 304mm Haydn Rods. Guess what happend:
6-factor calibration:
Calibrated 6 factors using 22 points, deviation before 0.032 after 0.030
8-factor calibration (after quite some itterations)
Calibrated 8 factors using 22 points, deviation before 0.017 after 0.013that's a lot better than the 0.87 I got before with the tricklaser rods. Probing Radius was kept same as with the old measurement, 140mm, which is perhaps a little too much for the 304mm rods, the rod angles get a little extreme at that radius
The 360mm Haydn Rods are already on their way to Switzerland, I hope the numbers stay about as good as they are right now….
-
Nice results. I have some printing to catch up on this week, but once that is done I will do some more tinkering to see what changes between arm lengths. The 325mm Trick Laser last generation arms are working very well though, so I'm running all my prints with those. I was worried a lot about the FSRs because they didn't seem to behave like I thought they would, but the arm swap definitely makes them much more reliable and easy to use.
@MiR:
I have now mounted my 304mm Haydn Rods. Guess what happend:
6-factor calibration:
Calibrated 6 factors using 22 points, deviation before 0.032 after 0.030
8-factor calibration (after quite some itterations)
Calibrated 8 factors using 22 points, deviation before 0.017 after 0.013that's a lot better than the 0.87 I got before with the tricklaser rods. Probing Radius was kept same as with the old measurement, 140mm, which is perhaps a little too much for the 304mm rods, the rod angles get a little extreme at that radius
The 360mm Haydn Rods are already on their way to Switzerland, I hope the numbers stay about as good as they are right now….
-
Today I received my 360mm Haydn Rods. After a few rounds of 8-factor calibration I ended up with this:
Calibrated 8 factors using 16 points, deviation before 0.013 after 0.008
So it is definitely the Tricklaser Rods that are causing the calibration issues, I will ask the tricklaser guys if they have an idea why… (Or did anybody already contact them?)
-
@MiR:
Today I received my 360mm Haydn Rods. After a few rounds of 8-factor calibration I ended up with this:
Calibrated 8 factors using 16 points, deviation before 0.013 after 0.008
So it is definitely the Tricklaser Rods that are causing the calibration issues, I will ask the tricklaser guys if they have an idea why… (Or did anybody already contact them?)
What radius did you probe at?
What arm length did it auto calibrate to, does it match real rod length?
Does it print parts at true scale now?What did you change to go from ball-cup pivot balls to mag-ball pivots?
-
I did not notice if anyone is using the "h" parameter in their G30 probing?
This value is a height correction for probe trigger height.
What I understand is that your probe triggers at different heights depending on location of bed.
So, unless you measure actual trigger height at each probe location (and put those values in bed.g) I do not believe you are getting true calibrations, especially when tweaking down to such small deviations like you all are chasing after.
Furthermore, I suspect those trigger values change when you change arms, joints, or any other part of your mechanical linkage.If you think you need to get closer than what auto calibration probing does, why not use mesh bed height compensation on top of the auto calibration??
If you know your real arm length, I don't think you should let auto calibration change that value.!
Also, probing at extremes of travel (140 mm radius) does not help, I feel the geometry out there is to unstable to be reliable (and worse the shorter the arms are) I get more predictable results at 125 mm radius.
