@JoergS5

The M92 Z0 was a mistake, I meant G92 Z0 (set Z axis to zero). I was able to perform the test again with multiple configs; z-axis homed to 0 and another pass with z=1, with no z-axis at all, but still set to zero, all configs yielded the same results. After initial homing my points were 159.2, 0. I then ran G91 then G1 H2 X90 Y90 three successive times. Each time, only the proximal arm rotated and the distral kept inline with with the proximal arm, just as my original image with the blue and red arms. The subsequent x,y coordinates changed slightly, but were similar and in the same quadrants. In order, after homing, the points were (-70.7, 70.7), (0, 15.8) and (-86.5, -86.5) .

I realized the G1 H2 X90 Y90 command is working correctly. Since my cross talk is 0, if I only ran X90 it would look like this.

After the command G1 X90 Y90, both arms would be pointing straight up as in my previous red/blue diagram.

I think that mystery is solved, but the resulting coordinates for x and y still don't make sense for me.

Can you elaborate on your comments on absolute coordinates from a previous reply and how they relate to relative angle moves? Once setup correctly, if I issue the command absolute G1 X50 Y50, the tool head should go to the x,y coordinate specified, yes? And if I issue absolute G1 H2 X0 Y0 then then both arms should go to the absolute zero angles, yes?

Also, I see varying settings from diff posts trying to configure the same. Does it matter which direction the proximal and distral arms rotate (clockwise or counter clockwise) given a relative positive angle? If so, which way should each arm rotate given a positive relative angle command like G91 then G1 H2 X90?

config.g

M929 P"debug.log" S1; turn on logging to web interface

M552 S1                                           ; enable networking/wifi

M84 600 ;idle timeout

M575 P1 S1 B57600  ;Enable PanelDue

; Network
M550 P"SCARA Sandbot" ; Set machine name

M586 P0 S1  ; Enable HTTP
M586 P1 S0  ; Disable FTP
M586 P2 S1  ; Enable Telnet

M584 X0 R1 Y1 R1;  P2 ; drive 1 (x) rotation, drive 2 (y) rotational, P2 hides Z-axis


M569 P0 S0 D2  ; Drive 0 (X) 
M569 P1 S0 D2  ; Drive 1 (Y)


M208 X-160:160 Y-160:160 Z0:0  ; set machine limits
M350 X16 Y16  ; Configure micro-stepping with interpolation

M92 X26.666666667 Y26.666666667     ; Steps per degree. (200 steps/rev * 16 microsteps * 60t/20t) / 360 degree
M566 X25 Y25  ; max instantaneous change in accel/jerk
M201 X250 Y250 ; acceleration
M203 X8000 Y8000 ; max speed (mm/min)
M906 X400 Y400 I20 ; motor current in mA

;Set SCARA
M669 K4 P79 D79 A-185:175 B-178.75:181.25 S1000 T0.01 R0 C0:0:0; X100 Y-50; X112 Y-66

;Endstops 
M574 X1 S1 P"!xstop"   ; X min active low endstop switch
M574 Y1 S1 P"!ystop"   ; Y min active low endstop switch

Thanks!

@JoergS5

Thanks for the Z axis tip, I will test this out tonight and report back.

@JoergS5

Thanks for looking at this. Trying to explain the "180 degrees and opposite". I read in setup that once you hit your homing point, to set the A & B angles so that they place the are in the middle of the full movement of the arm. So after homing, I set A to be -185:175. since my full movement of X is 0 to 360, -180 is approx in the middle of the range of motion and the extra negative 5 degrees is just me trying to line of the X axis with a reference point I have on the machine.

@Imlbrown said in Serial SCARA Configuration Issue:

After homing, if I run G91 then G1 H2 X90 Y90 successive times the points (X, Y) are starting at home with 158, 0 then -79,79 then 0,0 then -79, -79. The Y values make complete sense, but the X values are an issue and I don't see where I went wrong.

You drew what I would expect for the coordinates, but my image is where the arms actually were with the coordinates reported. Note: the 159,0 coordinate should have been 158, 0.

They don't make sense to me given the location of the arms. I have to ask, if I made a relative move, why wouldn't the coordinates reflect the actual position of the tool (end of the distral arm)? This is my first venture beyond Cartesian 3d printers, but I thought if you performed a relative move the x,y coordinates would still be accurate, can you explain the diff between relative angle moves and absolute coordinates in a scara configuration?

I just realized, the command G1 H2 X90 Y90, was not rotating the Y (distral) arm, why does the diagram you drew not reflect what actually happened.

@o_lampe Thanks for taking a look, I read about that issue, but forgot about it while posting. Even if I use G90 then G1 X25 Y0 still looks "off", but G1 X25 Y25 does look reasonable. So looks like any axis that nears zero is a concern. Let me experiment some more.

I have a serial arm SCARA machine that I am trying to configure as a sandbot, so no Z required. I've attached my config.g, homeproximal.g and homedistral.g files.

I have been using this configuration page [https://docs.duet3d.com/en/User_manual/Machine_configuration/Configuration_SCARA](link url)

The sandbot is not constrained and both the proximal and distral arms can rotate fully 360 degrees without hitting an obstruction. Any movement by either arm does not affect the movement of the other arm, so no cross talk.

Also, when I run G91 then G1 H2 X-90 (clockwise) or Y-90 (clockwise) the respective arms looks to move exactly 90 degrees, so I believe my steps per degree appear to be correct.

When I home all, the proximal arm with G1 H2 X-365, the arm rotates clockwise, so the end stop is configured as (X1), the minimum angle.
The distral homing starts with G1 H1 Y-365 and it rotates clockwise during homing, so the end stop is configured as (Y1), the minimum angle.

Since I have full 360 degree rotation, I set the angles in the M669 command to A-185:172 & B-174:186. This puts both arms exactly 180 degrees opposite of their homing point and half way thru their full travel angles.

After homing the proximal arm and distral arm are inline and the X,Y coordinates are X=158 and Y=0, since I did not use the xy offsets. This looks correct to me. Looking down from the top, both arms are fully extended to the right.

When I execute G90 then G1 X0 Y0, I am expecting the end of the distral arm to end up exactly over the proximal arm's fixed joint, but instead X ends up being x=8.3 and Y=0, but the actual coordinate (looking down over the device) appears to be somewhere near X=-79 and Y=-79, the proximal joint angle moved 90 degrees clockwise and the distral angle moved a little less than 90 degrees anti-clockwise. Basically, proximal is pointing down and distral is pointing left looking down from the top.

If everything was configured correctly, should an absolute move of G1 X0 Y0, put the tool (end of distral arm) over the proximal joint?

After homing, if I run G91 then G1 H2 X90 Y90 successive times the points (X, Y) are starting at home with 158, 0 then -79,79 then 0,0 then -79, -79. The Y values make complete sense, but the X values are an issue and I don't see where I went wrong.

Thanks in advance for any assistance.

config.g homedistral.g homeproximal.g

Hi DC42,

I received your email stating that you can't jump directly from 2.x to 3.x without first installing the 3.0 release first. This did not apply to me as I did follow the extensive instructions to get 3.0 installed and config upgrades.

I was able to grab Duet2CombinedIAP.bin from 3.1 RC10 release page, upload it then upload 3.01 RC11 and it flashed ok. That is the first file that dropped from my SD card, if I have any other issues I will look to replace it.

Thanks.

In the middle of a print But will do that first thing when it is completed and respond.

Thanks!

I do not see that file on my SD card looking at the system directory via DWC. If that is the issue, what is the correct process to get it back?