Scara support ?

dc42

Ok, so what i have assumed is +X is your +Y, and what I have assumed is +Y is your -X. Thinking about it, there are 4 possible orientations of the bed if we only consider the obvious ones, and I guess the firmware should allow any of them in a configuration option. Or maybe it should allow an arbitrary bed rotation angle.

For now, if you define the top left corner of the bed in your diagram as (0,0) and the axis directions as I have assumed them, then you should be able to print

Regarding homing, I was assuming there will be a limit switch at one end of the travel of each joint.

frafa

Of course I'm stupid, I did not think about it
I test this afternoon

frafa

Hi
define the top left corner of the bed, change on M669 x/y
and print…
ok

Video, sorry the machine is under development all is not clean ...
http://www.openhardware.eu/tmp/DuetWifi/VID.mp4

I still have to solve the same vibrations as with Smoothie …

My M669
M669 K4 P200 D200 A-175:175 B-175:175 1:0:0 S200 X118.0 Y-150;

My reduction motor and pulley
Motor 400 step/revolution 0.9°
Pulley 80/16
Microstepping 256
Calcul Step/° X/Y (Réduct 80/16) ==> 400256(80/16)/360=1422,2222222222222222222222222222

What can be the cause in your opinion not enough mechanical reduction, or other ?

Thank you very much !

dc42

I'm glad you are making progress.

Have you tried adjusting the segments/sec and minimum segment length in the M669 command, to see whether it affects the vibration?

frafa

I am also pleased !
Not tried, i test tomorrow.

frafa

Hello,

I've done a lot of testing, and the best configuration seems to be
M669 S200 T0.5
It's not perfect, but it's better

But on another piece the result is not satisfactory

Saturday I tried on cubes and diamonds to try to understand,
Because the vibrations seem to be present only on the diagonals of the bed …
If you have an idea to improve ...

I will redo the arm to pass in reduct of 160/16
And GT2 belts 10mm high to see if it improves
http://www.openhardware.eu/tmp/DuetWifi/VID_20170713_181706.mp4

frafa

Hello,
I'm Happy
It is almost perfect there are still some vibrations but I think I can further refine the firmware settings

I completely redraw the arms of scara
Now reduction 160/16
pulley DIY gt2 lasercut and Wide belt 10mm high
New experimental firmware 1.19beta10

http://www.openhardware.eu/tmp/DuetWifi/new/VID_20170721_171557.mp4

number40fan

I can't help to think how a set of shock absorbers would help. You have so much mass hung out so far that you are trying to stop and start. Am I wrong in thinking that something that could help dampen the movement would help?

dc42

I'm glad you are making progress! You are the first person to use RRF or a Duet on a Scara printer.

I'll try to implement Scara homing before the 1.19 release. You will need a microswitch at one end of the movement range of each joint.

frafa

Thanks to you for your reactivity !

The endstop will be hall effect 3v logic / v+ on 5v (banggood model)

dc42

Is your SCARA printer home designed and built, or is the mechanics built from a kit? We're looking for some SCARA mechanics to use as a test bed for the SCARA support in RRF.

frafa

Hello
This is a model designed by me being created,
It will be open-source when finished
Download Sketchup 2016 model of the current model being developed: http://www.openhardware.eu/tmp/DuetWifi/scara-v5.skp
humm … google translate ...
Evolutions in progress not final model, but functional...

frafa

Hello,
A big thank you for the support of Scara and end stops on version 1.19RC1
I test tomorrow

My end stops are not exactly on X0/Y0 M206 is supported ?
and move in X0/Y0 after homing ?

frafa

Hello,
Is it possible that you explain how to set up Homing on Scara
https://duet3d.com/wiki/Configuring_RepRapFirmware_for_a_SCARA_printer

dc42

I've just done that.

frafa

Hello
A big thank you for all your work!

My end-stop limit is not exactly in X0 / Y0
Before with smoothie I used M206 to specify offset and move on real X0/Y0 after homing

How to do with ReprapFirmware?

dc42

Your endstops need to be at one end of each of the proximal and distal joint limits as described in the wiki. They detect the limits of movements of the joint angles. Those limits are wherever you say they are in the M669 command.

frafa

ok I understood
I test tomorrow the scara is at the fablab

It is posible to move x / y after homing on scara and to redefine origin with with G92 x0 y0? (I wish to work only in the square of the bed)

In the documentation the command M669 I no longer see the X and Y parameters
https://duet3d.com/wiki/Configuring_RepRapFirmware_for_a_SCARA_printer

Example for me
K4 P200 D200 A-175: 175 B-175: 175 1: 0: 0 S200 T0.1 X84.0 Y-150.0;
How the calculation is done if we do not specify or is X0 / Y0 with respect to the axis

dc42

No you can't redefine the origin with G92. However, you can use the M669 X and Y parameters to set the origin wherever you like, as we discussed previously.

The way the calculation is done is as follows:

The X axis is the direction that the proximal arm points along when its angle is zero. You can choose where you consider the zero angle to be, however it would generally be sensible to have it near the middle of its range of movement. When you have chosen the position that you consider to be zero angle, that determines what the minimum and maximum angles are, which you specify in the M669 D P parameters (and either the minimum or the maximum one is the trigger point of the proximal joint homing switch).
The zero angle of the distal joint is defined as the angle when both arms are lined up.
If you specify X and Y offsets of zero in the M669 command, then X0 Y0 will be the position of the axis of the proximal joint (which is an unreachable position in most SCARA architectures). So specify X and Y in the M669 command relative to that. I would expect that in a typical case, the X offset will be positive by an amount somewhat smaller than the square printable X range, and the Y offset will be negative by about half the square printable Y range.

I will add this info to the wiki.

There is a SCARA printer kit on its way to me, so I should be able to test all of this in a couple of weeks.

HTH David

EDIT: I've corrected the above text, and added it and a Calibration section to the wiki page.

frafa

OK
So for the moment I am obliged to declare in M669 xxx / yyy exactly at the position of the endstops

No way to shift the origins to have x0 / y0 at the exact angle of the bed?