Folger Tech Kossel Delta 2020 Full 3D Printer Kit w/Auto-Level
Posted by Kasahabo
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Re: Folger Tech Kossel Delta 2020 Full 3D Printer Kit w/Auto-Level November 02, 2015 11:02PM |
Probably you have activated Eeprom that overrides your default settings 
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Re: Folger Tech Kossel Delta 2020 Full 3D Printer Kit w/Auto-Level November 03, 2015 01:49AM |
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paul_delta
Koenig, I respect your patience but I'm really tired of your RADII
Again, I'm talking about per axe size disproportion of printed item. This is what DIAGONAL correction does (Corr. diagonal A/B/C in Repetier). I don't care what is the reason of such disproportion - I just know that diagonal rod corection per tower is the way to handle it, with minimum AVR computation power. I don't need ABC/XYZ delta radius compensation because I have no gaps with Z0 across A/B/C towers - everything is flat enough to forget about delta radius correction PER TOWER.
PS: and it's not correct to use "tower offset" in this matter, because it's linked to endstop adjustment - both in Marlin and Repetier.
And what you fail to comprehend is that by adjusting each towers radii (tower offset towards a middlepoint (Something called delta_smooth_rod_offset in the picture I posted earlier) you are also correcting per axe size disproportion of printed item.
but it would be the correct way to do it if you know your rod lengths are the same.
Why go trying to correct something that is correct from the get go is beyond my understanding + that trying to do so introduces other errors.....
You just won't take anything in of what other people write right...?
Here's the base for my claims:
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Perhaps the most common problem with Delta printers is dimensional inaccuracy. I am not sure if this calibration method produces other undesirable results, and your milage may vary. My Rostock had a discrepancy of ~0.3mm in Tower A, and this is how I corrected it. It took me a few iterations of this process before I was able to print an asterisk that is symmetrical to 0.05 - 0.1mm, which should be good enough to produce parts for another printer (an oversized Kossel is my next project).
Here is a test object that I use for calibration. It's quite simple. It's an asterisk with the diagonal lines running parallel to each tower, with a horizontal line through the centre. It should be rotated so that the diagonal lengths are parallel to Towers A and B.
The purpose of this shape is to try and isolate movement from each tower to determine whether the 'lines' each one draws is equal. Inevitable inaccuracies in the build (radial positioning of towers, distance from centre and rod length) will produce distortions in the X and Y axes.
These errors are best accounted for by assigning individual DELTA_RADIUS values for each tower. If you happen to have uneven rods, I recommend remaking them.
In order to allow for individual DELTA_RADIUS values for each tower, add the following lines to your Marlin Configuration.h file:
// Tower position correction
#define DELTA_TOWER1_CORRECTION 0.0 // front left tower
#define DELTA_TOWER2_CORRECTION 0.0 // front right tower
#define DELTA_TOWER3_CORRECTION 0.0 // back middle tower
And find these lines in Marlin_main.cpp (2 places):
float delta_tower1_x = -SIN_60 * delta_radius; // front left tower
float delta_tower1_y = -COS_60 * delta_radius;
float delta_tower2_x = SIN_60 * delta_radius; // front right tower
float delta_tower2_y = -COS_60 * delta_radius;
float delta_tower3_x = 0; // back middle tower
float delta_tower3_y = delta_radius;
And alter them to look like this:
// Effective X/Y positions of the three vertical towers.
float delta_tower1_x = -SIN_60 * (delta_radius + DELTA_TOWER1_CORRECTION); // front left tower
float delta_tower1_y = -COS_60 * (delta_radius + DELTA_TOWER1_CORRECTION);
float delta_tower2_x = SIN_60 * (delta_radius + DELTA_TOWER2_CORRECTION); // front right tower
float delta_tower2_y = -COS_60 * (delta_radius + DELTA_TOWER2_CORRECTION);
float delta_tower3_x = 0; // back middle tower
float delta_tower3_y = delta_radius + DELTA_TOWER3_CORRECTION;
You'll need a pair of calipers for this part. I find that it's best to use them as a kind of feeler gauge, rather than relying on the reading they give. You'll probably find that the length changes a little depending on where you measure and how much pressure you apply. With any luck, the lengths of the lines will be very close to one another. If you have large discrepancies (> 1mm), I suggest backtracking and looking for errors in the build. It is important that you measure test prints once they have properly cooled. ABS will shrink more than PLA, so it might be a good idea to do this with PLA.
Measure each length of the asterisk, taking note of the differences between them. Pick the two lengths that are closest to one another, or the length closest to your target size and use that as your reference point.
Start by adjusting the tower correction value for your innacurate tower(s) by twice the negated value of the difference. If you have two towers that are out of kilter, just start by adjusting one of them. For example, you have a difference of -0.3mm in Tower A, set the correction value to be 0.6mm.
Adjusting the radii of each tower will affect the endstop calibration for that tower (if you increased DELTA_RADIUS, it'll raise the effector at the base of the tower). You might also need to tweak the overall DELTA_RADIUS value (start by making a +/- 0.25mm adjustment to DELTA_SMOOTH_ROD_OFFSET).
In any case, get the effector moving flat once more (again, it shouldn't matter if it's not perfect, as you'll be tweaking things again) and perform another test print. Measure and repeat.
Once you're happy with the symmetry of your asterisk, work on getting each tower perfectly level and the effector moving dead flat. You should be able to send it moving all over the build platform without having it lift or dip.
Now these lines are included in newer version of Marlin but not the version from FT.
They are also included in thevisad's repo
davidf01 can add them himself the the FT version if he prefers that one.
The instructions were taken from a delta calibration instruction that has been referred and linked to hundreds of times on this forum, unfortunately it's no longer online, this is the link: [delta-calibration.s3-website-us-west-2.amazonaws.com]
For davidf01: This also includes a small guide as how to use your measured inaccuracy and implement it in the firmware.
Edited 3 time(s). Last edit at 11/03/2015 02:25AM by Koenig.
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Re: Folger Tech Kossel Delta 2020 Full 3D Printer Kit w/Auto-Level November 03, 2015 12:37PM |
I have my next problem. When I try to move the printer head to a specified location in the Z-axis only, it doesn't move any where near straight down.
The guy here that knows a tiny bit about 3D printers stated that it might have something to do with the steps. I currently have them set as:
#define DEFAULT_AXIS_STEPS_PER_UNIT {80, 80, 80, 100}
It seemed to me that if the three axis are set the same, then it should move the same? I can see that I might be thinking about this incorrectly too though. Is this a possibility, that they're just set incorrectly?
Another (more mechanical guy) says that it might be drag on a couple of the axis (an answer I better understand). I will mention one caveat: When I assembled the roller sliders onto the rails, they were so tight that they cause the three rollers to be flexed out. There is a screw that goes thru the two sides which you would use to bring the rollers closer together, but that will never be used because the slider unit was so tight. Did I get a bad set of printed parts? Is it supposed to flex out when assembled? The rollers will move but they're pretty stiff.The part I'm talking about is this one:
The guy here that knows a tiny bit about 3D printers stated that it might have something to do with the steps. I currently have them set as:
#define DEFAULT_AXIS_STEPS_PER_UNIT {80, 80, 80, 100}
It seemed to me that if the three axis are set the same, then it should move the same? I can see that I might be thinking about this incorrectly too though. Is this a possibility, that they're just set incorrectly?
Another (more mechanical guy) says that it might be drag on a couple of the axis (an answer I better understand). I will mention one caveat: When I assembled the roller sliders onto the rails, they were so tight that they cause the three rollers to be flexed out. There is a screw that goes thru the two sides which you would use to bring the rollers closer together, but that will never be used because the slider unit was so tight. Did I get a bad set of printed parts? Is it supposed to flex out when assembled? The rollers will move but they're pretty stiff.The part I'm talking about is this one:
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Re: Folger Tech Kossel Delta 2020 Full 3D Printer Kit w/Auto-Level November 03, 2015 02:37PM |
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Legrand
I have my next problem. When I try to move the printer head to a specified location in the Z-axis only, it doesn't move any where near straight down.
The guy here that knows a tiny bit about 3D printers stated that it might have something to do with the steps. I currently have them set as:
#define DEFAULT_AXIS_STEPS_PER_UNIT {80, 80, 80, 100}
It seemed to me that if the three axis are set the same, then it should move the same? I can see that I might be thinking about this incorrectly too though. Is this a possibility, that they're just set incorrectly?
Another (more mechanical guy) says that it might be drag on a couple of the axis (an answer I better understand). I will mention one caveat: When I assembled the roller sliders onto the rails, they were so tight that they cause the three rollers to be flexed out. There is a screw that goes thru the two sides which you would use to bring the rollers closer together, but that will never be used because the slider unit was so tight. Did I get a bad set of printed parts? Is it supposed to flex out when assembled? The rollers will move but they're pretty stiff.The part I'm talking about is this one:
Are you homing it prior to trying to move the Z axis? Not sure if it is normal behavior, but if I try to doa Z move right after power up it acts very strange. If I home it first, then all is well.
As for the roller carriages, the ones that came with my kit were tight. I printed new ones on my other printer that came out beautiful, and they were tight as well. I found that after running them up and down for a while (both manually and after the printer was working) they loosened up nicely. I used the tensioning screw to then lock in the good setting.
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