Delta cal torture

Delta cal torture Hey all. So I set out to design and build my own printer a while ago. It's been a long, time-consuming process, and I've been stuck here at the finish line for a while now. I've tried everything I could thing of but for the life of me I can't get the damn thing to print flat. It shows some peculiar behavior while calibrating. Quick list of things that seem relevant before I go into the details. It's based heavily off of the 3DR and the Kossel. -Ramps 1.4 -Pololu drivers -Spectra line drive -CF rods/ Traxxas joints -Cerberus pup carriages w/ openbuild wheels -3DR Idlers -Marlin -Heated plate fastened to Kossel-esque frame -Opto-endstops A couple examples of weird behavior. -When I get to M666 calibrating my Y tower, it will be wayyyy lower than it should be and I have to send the extruder to the center and back, or home and back, and it will come back to the Y tower at the right height. Like I had to shake something off or something. Really inconsistent. -Sometimes one the M666 offset values for one of my towers will require an unusually large adjustment and then after adjusting it finer finer, I end up back close to or at the original value. -When all 4 cal points pass the paper test(post-it note folded in half), my prints still seem to come out way off. Like adjusting doesn't have any logical effect on it. I'll attach a picture of one of my cal prints. [img]http://i1161.photobucket.com/albums/q519/Tennysballs/20151007_154636_zpsihaurseg.jpg[/img] I've tried switching surfaces, switching carriages and wheels, switching from magnet joints to the traxxas joints, etc....Does anyone have any advice? I'm about to lose it. Thanks in advanced. https://reprap.org/forum/read.php?178,567957,567957#msg-567957 Mon, 20 Jul 2026 10:08:21 -0400 Phorum 5.2.23 https://reprap.org/forum/read.php?178,567957,573384#msg-573384 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,573384#msg-573384
1. "sticky" carriages. To eliminate this you may need to reduce friction and/or increase motor current and/or apply the decay hack to your drivers (or use drivers that already have it applied). I suggest you start with the decay hack if you haven't already implemented it (warning: applying the decay hack to DRV8825 drivers may fix the problem but tends to make the motors whine).

You need to sort out that issue before you move on to your second problem:

2. Inconsistent heights at points between towers even when the carriages are not sticking, as seen in the calibration print in the first post. I had a similar problem when I built my Mini Kossel - valleys between two pairs of towers, and a ridge between the other pair. This can be caused by various mechanical issues, such as towers not being at the corners of an equilateral triangle, or towers leaning slightly. You can correct for these problems (not necessarily perfectly, but adequately in my experience) by calibrating the tower position offsets in the firmware.

By far the easiest way of calibrating the tower offsets is to use the fast least squares auto calibration in RepRapFirmware. This is how I solved the problem. To run RepRapFirmware, you have to use Duet, RADDS or Alligator electronics. If your electronics runs Marlin, there is a less advanced auto calibration algorithm in Rich Cattel's fork that works for some people. For either of these, you need a good Z probe.

There are also manual calibration techniques for calibrating the tower positions, but I think they are quite tricky to use and I haven't tried them.]]> dc42 Delta Machines Wed, 21 Oct 2015 05:04:33 -0400 https://reprap.org/forum/read.php?178,567957,573341#msg-573341 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,573341#msg-573341 Tennysballs Delta Machines Wed, 21 Oct 2015 02:56:58 -0400 https://reprap.org/forum/read.php?178,567957,573339#msg-573339 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,573339#msg-573339 If you'd have sorted out the inaccuracy issues before starting the calibration marathon, it might have been successful the first time....
It took me a month, before I was familiar with all the variables and related M-codes...only to find out that marlin on an 8bit controller is not the best choice for a delta.
Now I have the same learning curve ahead off me with a duet controller and dc42's RRP config...
-Olaf]]> o_lampe Delta Machines Wed, 21 Oct 2015 02:52:29 -0400 https://reprap.org/forum/read.php?178,567957,573291#msg-573291 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,573291#msg-573291
I'm about burnt out though. It's all calibrated at all the towers but the nozzle still digs into the kapton tape at the same spot that it used to. Not sure if it's the frame that it's mounted to or my print bed. Either way I'm about out of juice on this project.]]> Tennysballs Delta Machines Tue, 20 Oct 2015 19:15:41 -0400 https://reprap.org/forum/read.php?178,567957,572673#msg-572673 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,572673#msg-572673 dc42 Delta Machines Mon, 19 Oct 2015 14:36:33 -0400 https://reprap.org/forum/read.php?178,567957,572661#msg-572661 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,572661#msg-572661
So I ordered the DV8825s over the weekend and just finished installing and tuning them according the the formula given on the reprap wiki page. I left my same jumper configuration on the board(which would make it 1/32 steps) and doubled my steps per unit accordingly. It seems to have done the trick. I'll report again when I start trying to print.]]> Tennysballs Delta Machines Mon, 19 Oct 2015 13:45:44 -0400 https://reprap.org/forum/read.php?178,567957,570121#msg-570121 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,570121#msg-570121

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Tennysballs
So just some points to clarify.

-Got rid of all backlash/free play in the system

-Spectra line is guitar-string tight

-I can confirm that there is definitely a problem with the whole .1mm thing. No movement every other click with the exception of the 11th click

-I did more digging and it seems that he was using 16th stepping. He used 8th steps for a mixing extruder, hence my confusion.

That pretty much rules out the physical stuff, so whats left is the decay hack (although from my understanding the 4988's are not as affected by this as the 8825's) or trying another firmware.
You could flash repetier just to see if it behaves the same.

You could also try to make a macro that moves the effector 0.09mm instead of 0.1, if it would be so that Marlin can't handle the 5.55 steps that it takes to travel 0.1mm well, 0.09mm is more or less exactly 5 steps. (this is based on your previous statement of 55.5 steps/mm)

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macro
G91
G1 Z-0.09
G90

This you can add as a custom button in pronterface.

I'm using belts and pulleys (16t) and I can definitely feel every 0.1mm I try to move, I'm also using 1/16 microstepping, I can actually feel every 0.01mm step, I can go down so that the effector does not grip the paper but I feel the ridges of it when dragging and then I can continue down and feel how the grip hardens for every for every 0.01 step but then I'm also using 0.9° steppers + different firmware + different electronics (Duet) with other drivers (with the "hack).]]> Koenig Delta Machines Tue, 13 Oct 2015 10:46:01 -0400 https://reprap.org/forum/read.php?178,567957,570089#msg-570089 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,570089#msg-570089
-Got rid of all backlash/free play in the system

-Spectra line is guitar-string tight

-I can confirm that there is definitely a problem with the whole .1mm thing. No movement every other click with the exception of the 11th click

-I did more digging and it seems that he was using 16th stepping. He used 8th steps for a mixing extruder, hence my confusion.]]> Tennysballs Delta Machines Tue, 13 Oct 2015 10:01:52 -0400 https://reprap.org/forum/read.php?178,567957,569966#msg-569966 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,569966#msg-569966

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o_lampe
What was Rich thinking, to build a pulley with xx.5 steps? What would the driver do with half a (micro-) step?
-Olaf

What were you thinking now....? All travels are done in steps of 1mm or what?

Couldn't help myself! (:P)

Anyway, to the problem at hand.
If it only moves every other push for 0.1mm, try to confirm that it really is so, put your finger on the spool while pressing the button to see if you can feel it moving (to rule out 0.1mm slack in the spectra lines or somewhere else)
If you can confirm that the motor actually do not turn, you could try with the decay hack for a starter.

EDIT: There might be a reason why he only used 1/8 stepping, the accuracy of this system with spectra lines might not be up for 1/16.
I know to little about it to actually judge it, spectra line might even be better than belts for all I know.]]> Koenig Delta Machines Tue, 13 Oct 2015 05:19:46 -0400 https://reprap.org/forum/read.php?178,567957,569914#msg-569914 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,569914#msg-569914 dc42 Delta Machines Tue, 13 Oct 2015 03:27:00 -0400 https://reprap.org/forum/read.php?178,567957,569912#msg-569912 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,569912#msg-569912 switch over to GT2 belt and 16 tooth pulleys
or
Buy 0.9° steppers

Both options help you to increase accuracy.

What was Rich thinking, to build a pulley with xx.5 steps? What would the driver do with half a (micro-) step?
-Olaf]]> o_lampe Delta Machines Tue, 13 Oct 2015 03:20:10 -0400 https://reprap.org/forum/read.php?178,567957,569829#msg-569829 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,569829#msg-569829
Either way I'm still stuck on my responsiveness issue.]]> Tennysballs Delta Machines Mon, 12 Oct 2015 19:30:23 -0400 https://reprap.org/forum/read.php?178,567957,569763#msg-569763 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,569763#msg-569763

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Tennysballs
18mm diameter spools with spectra line. 16th steps.

I guess your 18mm diameter spools are bigger in diameter than the 16 or 20 tooth pulleys generally used with GT2 belts on Kossels and their derivatives.]]> dc42 Delta Machines Mon, 12 Oct 2015 16:57:34 -0400 https://reprap.org/forum/read.php?178,567957,569752#msg-569752 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,569752#msg-569752 Tennysballs Delta Machines Mon, 12 Oct 2015 16:41:49 -0400 https://reprap.org/forum/read.php?178,567957,569748#msg-569748 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,569748#msg-569748 dc42 Delta Machines Mon, 12 Oct 2015 16:39:54 -0400 https://reprap.org/forum/read.php?178,567957,569739#msg-569739 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,569739#msg-569739
I know nothing is loose because the problem follows a consistent pattern that I previously outlined.]]> Tennysballs Delta Machines Mon, 12 Oct 2015 16:28:53 -0400 https://reprap.org/forum/read.php?178,567957,569694#msg-569694 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,569694#msg-569694

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Tennysballs
Since the problem was persisting, I jumped into the firmware(Marlin) to look around. I'm using 16th steps. Since I am using Rich's spool design from his 3DR(and his default steps per unit), I double checked to see if maybe he was using a different step rate and if changing it would make a difference. I couldn't really find any solid information on it, but it seemed that he might have been using 8th steps. I doubled his 55.5 steps/unit just to see what happened and my problem of inconsistent response went away-it would move every time I would press the .1mm button. The problem was that when I got to what should be Z0 in M114, I was at about half of my total Z height. So I guess I had the right step rates. I'm not sure what to make of all that....

That is pretty much what is expected to happen if you double the steps/mm...

Then the question is, which of the two scenarios match your physical Z-height?

However, when I come to think of it, I had a similar problem a while ago when I changed from 1.8 degree steppers to 0.9.
Turns out I had a slightly loose pulley.....]]> Koenig Delta Machines Mon, 12 Oct 2015 15:02:48 -0400 https://reprap.org/forum/read.php?178,567957,569675#msg-569675 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,569675#msg-569675
Since the problem was persisting, I jumped into the firmware(Marlin) to look around. I'm using 16th steps. Since I am using Rich's spool design from his 3DR(and his default steps per unit), I double checked to see if maybe he was using a different step rate and if changing it would make a difference. I couldn't really find any solid information on it, but it seemed that he might have been using 8th steps. I doubled his 55.5 steps/unit just to see what happened and my problem of inconsistent response went away-it would move every time I would press the .1mm button. The problem was that when I got to what should be Z0 in M114, I was at about half of my total Z height. So I guess I had the right step rates. I'm not sure what to make of all that....]]> Tennysballs Delta Machines Mon, 12 Oct 2015 14:21:47 -0400 https://reprap.org/forum/read.php?178,567957,569412#msg-569412 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,569412#msg-569412

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dc42

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Tennysballs
So this kind of sucks. But in a way it's good because it's something. So I tuned my motors to ~480mv Vref using the following data.

Current/phase of motors = 1.5A
70% of 1.5A = 1.2A

Vref = I_TripMax * 8 * Rs
= 1.2A * 8 * .05ohms
=480mv

...

Did I tune them right?

Check which you have, look under "Current sense resistors" on this page for the how and where to check that.

EDIT: This link will take you directly to the "Current sense resistors" part.]]> Koenig Delta Machines Mon, 12 Oct 2015 03:57:18 -0400 https://reprap.org/forum/read.php?178,567957,569408#msg-569408 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,569408#msg-569408
Oops. That was absent minded. Thanks for pointing that out.]]> Tennysballs Delta Machines Mon, 12 Oct 2015 03:48:23 -0400 https://reprap.org/forum/read.php?178,567957,569404#msg-569404 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,569404#msg-569404

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Tennysballs
So this kind of sucks. But in a way it's good because it's something. So I tuned my motors to ~480mv Vref using the following data.

Current/phase of motors = 1.5A
70% of 1.5A = 1.2A

Vref = I_TripMax * 8 * Rs
= 1.2A * 8 * .05ohms
=480mv

...

Did I tune them right?

You have assumed that your drivers use 0.05 ohm sense resistors. A few do (AFAIR the Pololu Black Edition and T3P3 Ice Blue), but most others use 0.1 ohm resistors. So you may be running your motors at only 40% of their rated current. If you really are running them at 1.2A then the motors will be getting warm and the drivers will be getting very hot. If everything is running cool then try 800mV instead.

In your calculation, I presume you meant 80%, not 70%.]]> dc42 Delta Machines Mon, 12 Oct 2015 03:38:48 -0400 https://reprap.org/forum/read.php?178,567957,569313#msg-569313 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,569313#msg-569313 something. So I tuned my motors to ~480mv Vref using the following data.

Current/phase of motors = 1.5A
70% of 1.5A = 1.2A

Vref = I_TripMax * 8 * Rs
= 1.2A * 8 * .05ohms
=480mv

Here is the interesting thing I noticed. The carriage only moved every other time I clicked the .1mm jogger, with the exception of the 11th time I pressed it. I used M114 to confirm however that each press was being registered as shown by a decreasing of my Z height by .1mm.

So if each character in this string represented one instance of me pressing the .1mm button, and a O = no movement and X = movement of .1mm, it would look like this. Consistently.

X O X O X O X O X X

Did I tune them right? Any ideas what would cause this behavior?]]> Tennysballs Delta Machines Sun, 11 Oct 2015 18:13:36 -0400 https://reprap.org/forum/read.php?178,567957,568931#msg-568931 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,568931#msg-568931 Tennysballs Delta Machines Sat, 10 Oct 2015 14:52:14 -0400 https://reprap.org/forum/read.php?178,567957,568925#msg-568925 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,568925#msg-568925

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Tennysballs
My data sheet doesn't say anything about Max current. Just current per phase. 1.5A. Does that sound right at all?

That would be it.

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Tennysballs
And I'm not sure about the backlash. Maybe I don't understand backlash, but I thought it was only really applicable to gears

Translate it to "play in moving parts", all of that needs to be eliminated to be able to do an accurate calibration.]]> Koenig Delta Machines Sat, 10 Oct 2015 14:46:59 -0400 https://reprap.org/forum/read.php?178,567957,568917#msg-568917 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,568917#msg-568917
And I'm not sure about the backlash. Maybe I don't understand backlash, but I thought it was only really applicable to gears]]> Tennysballs Delta Machines Sat, 10 Oct 2015 14:32:54 -0400 https://reprap.org/forum/read.php?178,567957,568820#msg-568820 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,568820#msg-568820
Do you have any backlash in the traxxas joints?

If I barely touch the effector at Z0 the nozzle will move and change position, I can feel it grabbing the paper harder.]]> s0me Delta Machines Sat, 10 Oct 2015 09:41:34 -0400 https://reprap.org/forum/read.php?178,567957,568719#msg-568719 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,568719#msg-568719

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o_lampe
I don't trust the wiki-formulas regarding the DRV8825 too much. I had a DRV8825 running stable at 2.4V on a 1.7A stepper. Regarding the formula, this would have been 4.8A ?!
IIRC the formula was Vref = Imax *2....
But the A4988 formulas look right to me as long, as you identify the Rs value of your drivers.
-Olaf

Take it from Pololu themselves then: [www.pololu.com]]]> Koenig Delta Machines Sat, 10 Oct 2015 04:32:00 -0400 https://reprap.org/forum/read.php?178,567957,568711#msg-568711 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,568711#msg-568711 IIRC the formula was Vref = Imax *2....
But the A4988 formulas look right to me as long, as you identify the Rs value of your drivers.
-Olaf]]> o_lampe Delta Machines Sat, 10 Oct 2015 04:04:26 -0400 https://reprap.org/forum/read.php?178,567957,568593#msg-568593 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,568593#msg-568593

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Tennysballs
Olampe, Yeah that does sound pretty similar to what I am experiencing. Could be an under current issue. When you say decay hack, is that the same thing as the r4 hack? Should I try and tune the pots before I do that? Because from what I have been reading, I can't really find a solid value for what vref should be.

What Vref you should set is depending of what your motors are rated for, as mentioned earlier you should aim for about 60-80% of your motors rated current.
Wiki about the pololu board, check under "Tuning motor current" for the math to calculate appropriate Vref for your motors.]]> Koenig Delta Machines Fri, 09 Oct 2015 16:05:26 -0400 https://reprap.org/forum/read.php?178,567957,568583#msg-568583 Re: Delta cal torture https://reprap.org/forum/read.php?178,567957,568583#msg-568583 Tennysballs Delta Machines Fri, 09 Oct 2015 15:14:14 -0400