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Accumulative error in SCARA ROBOT

Posted by ECortes 
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ECortes
Accumulative error in SCARA ROBOT
September 13, 2015 08:46PM
Hello, I've had trouble calibrating the machine, for printing piece attached photo, use software designed by my work group, but has cumulative error and we decided to use the firmware of marlin for SCARA Robot, I had problems to carry my settings to marlin, please could help me with a drawing or illustration of what to do about how to take offset and other variables (hOME distance, from where they take the origin and others) etc. and you configure the firmware to use this Repetier Host.
please!!!
Thank you!
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Attachments:
open | download - 11998500_10207127450972314_329604785_n.jpg (61.7 KB)
open | download - 12025319_10207127433691882_1914270418_n.jpg (108.3 KB)
open | download - 12016642_10207127434091892_651584466_n.jpg (86.3 KB)
Evil Monkey
Re: Accumulative error in SCARA ROBOT
September 13, 2015 11:01PM
You are definitely not starting at the correct home position from looking at the third picture. What version of the SCARA firmware are you using?, if its Ttsolo's I can help there. The first picture looks as though the stepper motors are either loosing steps or those belts are not tight. The drivers current may need to be increased.

[scara3dprinter.wordpress.com]
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ECortes
Re: Accumulative error in SCARA ROBOT
September 15, 2015 10:06PM
Hi, thanks colleague Evil Monkey appreciate your concern, marlin firmware used morgan, belts are completely tense, and the mechanism has a negligible friction !, have done many tests and finally I managed to print several things, but I must improve, in the attached photos I show that I have problems, I think it is because I should divide more segments from one point to another, excuse my English but I use google translator.
In any case I had problems with this and I hope you can help me,
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Attachments:
open | download - IMG_20150915_120409.jpg (415.4 KB)
open | download - IMG_20150915_150319.jpg (533.6 KB)
open | download - IMG_20150915_204237.jpg (492.6 KB)
open | download - IMG_20150915_204312.jpg (417.9 KB)
open | download - IMG_20150915_204322.jpg (490.6 KB)
open | download - IMG_20150915_204331.jpg (552.3 KB)
open | download - IMG_20150915_204341.jpg (541.1 KB)
open | download - IMG_20150915_204349.jpg (493.5 KB)
open | download - IMG_20150915_204403.jpg (430.7 KB)
open | download - IMG_20150915_204416.jpg (425.8 KB)
Evil Monkey
Re: Accumulative error in SCARA ROBOT
September 17, 2015 11:30PM
Based on the second photo, I would agree that segments are rather large. In what way did you modify the Morgan firmware?

[scara3dprinter.wordpress.com]
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VDX
Re: Accumulative error in SCARA ROBOT
September 18, 2015 03:46AM
... what's your gearing for the 'shoulder' motors? - looks like underpowered motors 'playing' with the elasticity of the magnetic field between the fullstep-positions confused smiley

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]
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ECortes
Re: Accumulative error in SCARA ROBOT
September 19, 2015 12:16AM
Evil Monkey few things have changed with respect to the distance of the links and the offset, which is not how to increase the number of segments in the interpolator, but not if it can do, you know how to do ?, the robot moves super fast, but if segementos are very large wobbles and precision is lost and therefore finish.

VDX have always used the steps to 1/16 that is the maximum that gives me the ramps, the reduction ratio of the pulleys is 1: 2.12 and if you apply some force slide engines, what do you think I should do to improve this ?.
Thank you for your teammates time.

Look what I have achieved varying parameter in Slic3r, still having problems with the segments.
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Attachments:
open | download - Sin título.png (431.7 KB)
Evil Monkey
Re: Accumulative error in SCARA ROBOT
September 19, 2015 12:04PM
That picture looks like the machine is under extruding or the temperature is incorrect.

[scara3dprinter.wordpress.com]
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VDX
Re: Accumulative error in SCARA ROBOT
September 19, 2015 05:23PM
... I think, your gearing/reducing isn't high enough, so the motors don't give enough torque for the needed forces with this level sizes.

My last parallel scara was built with high precisison (1000 fullsteps per turn!) NEMA-36 steppers with 2Nm torque and 1:5 geared - so 10Nm(!) driven torque with 0.0072 degs resolution ...

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]
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Evil Monkey
Re: Accumulative error in SCARA ROBOT
September 19, 2015 05:36PM
dont suppose you have any pictures of it?

[scara3dprinter.wordpress.com]
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VDX
Re: Accumulative error in SCARA ROBOT
September 20, 2015 06:42AM
... no pictures, sorry - this was a customer development under NDA eye rolling smiley

But I have some of this motors and drivers left, so have plans to build a high precise (sub micron) cartesian or delta/par.-scara type machine for me, when needed winking smiley

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]
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ECortes
Re: Accumulative error in SCARA ROBOT
September 20, 2015 12:46PM
hey guys here I show the robot, perhaps what is says Victor, this was a project for undergraduate and that point is not discussed in due time.
Not to do, should be able to increase the segments, but not if it is in config.ho elsewhere, or that name is, and as I run out of time, I have 15 days to support the project, that I can work ?.

My Robot
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VDX
Re: Accumulative error in SCARA ROBOT
September 20, 2015 05:14PM
... it moves really 'shaky' - so the cause seems to be lack of torque and resolution with the motor-gearing-combo ... look, if you can apply a higher gearing ratio.

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]
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ECortes
Re: Accumulative error in SCARA ROBOT
September 20, 2015 09:41PM
Hello Viktor, what if the increase Scara_segments_per_second receiving further division of the segments ?, or what about this ?, until I increase the limit ?, which has negative effects on the robot ?.
Should I increase the current to increase torque ?,
because the mechanical part and remains so for now I can not change that for future changes will take this into account !.
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VDX
Re: Accumulative error in SCARA ROBOT
September 21, 2015 04:04AM
... don't think, shorter segment steps or higher microstepping will help, as this is a mechanical problem with the inherent elasticity while microstepping and lack of motor torque or gearing factors.

You can get a bit more torque with higher current, but this will only add some percents of torque, while you'll need something like 2x to 5x more confused smiley

Edited 1 time(s). Last edit at 09/21/2015 04:11AM by VDX.

Viktor
--------
Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]
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Wangsamax
Re: Accumulative error in SCARA ROBOT
March 17, 2017 10:53AM
Hi, you can try this configuration [www.wangsamas.com]
and download the firmware here [github.com]
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