Five bar Parallel SCARA print area problem

JoergS5 · 5 Nov 2021, 13:36

@rutku said in Five bar Parallel SCARA print area problem:

=> Please comment out the G0 Y0 Y0 line at the end of the homing file, so the values when the endstops are triggered can be controlled.

Then start Duet, and run the homing file. Both endstops must be triggered. Please report M114.

ThetaL and ThetaR should be 30 each at the homing position.

I suspect that the G0 X0 Y0, which is at the end of the homing file, is not reachable. My documentation in https://duet3d.dozuki.com/Guide/Five+Bar+Parallel+SCARA/24#s92 is only a draft of the printable area.

ThetaL: 249.5 (= 180 + 69.5) ThetaR: 69.45.
mean the both arms are nearly in opposite positions, and singularity example 1 of my explanation above is met:

rutku · 11 May 2021, 14:28

@joergs5 How could it be? I have printed almost all values in the FiveBarScaraKinematics.cpp file. I am adding all my settings and outputs again. I am adding the video of the process steps.

config.g

; General preferences
G90 ; Send absolute coordinates...
M83 ; ...but relative extruder moves
M552 S1 ; Turn network on

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

; Drives
M569 P0 S1 ; Drive 0 (X) goes forwards
M569 P1 S1 ; Drive 1 (Y) goes forwards
;M569 P2 S1 ; Drive 2 (Z) goes forwards
;M569 P3 S1 ; Drive 3 (E0) goes forwards
M584 X0 Y1 ; set drive mapping

M350 X16 Y16 I1 ;S3 ; Configure microstepping with interpolation
M669 K9 L1 X-95:95 Y0:0 P130:130 D210:210:0:0 B30:30 A15:165:0:360:0:360 C-90:270:-90:270 
M92 X115.555556 Y115.555556 ; Set steps per mm

M203 X10000 Y10000 ; maximum speeds mm/minute

M566 X15 Y15 ; Set maximum instantaneous speed changes (mm/min)
M201 X40 Y40 ; Set accelerations (mm/s^2)
M906 X1200 Y1200 ; Set motor currents (mA) and motor idle factor in per cent

M84 S0 ; Set idle timeout

; Axis Limits
 M208 X-1000:1000 Y-1000:1000 ; set axis minima and maxima

; Endstops
M574 X1 S1 P"xstop"   ; X min active high endstop switch
M574 Y1 S1 P"ystop"   ; Y min active high endstop switch
;M574 Z0 S1 P"zstop"   ; Z min active high endstop switch

home5barscara.g

G91              ; relative positioning

G1 H1 X100 Y300  F900 ; move quickly to endstop and stop there (first pass)
G1 H1 X300 F900
G1 H1 Y300 F900
G1 H2 X-2 Y-2 F900      ; go back a few degrees
G1 H1 X100 F90  ; move slowly to endstop once more (second pass)
G1 H1 Y100 F90  ; move slowly to endstop once more (second pass)
G1 H2 X-5 Y-5 F900      ; go back a few degrees

G92 Z0
G90              ; absolute positioning
G0 X0 Y0 ; move to a reasonable position

outputs:

m115
FIRMWARE_NAME: RepRapFirmware for STM32F4 based Boards FIRMWARE_VERSION: 3.2.2_2 ELECTRONICS: STM32F4 FIRMWARE_DATE: 2021-05-02
ok
WiFi module is connected to access point Utku, IP address 192.168.1.3

MotorStepsToCartesian => thetaL:224.27=MotorPosX:25916.00/StepsPermmX:115.56 
MotorStepsToCartesian => thetaR:224.27=MotorPosY:3467.00/StepsPermmY:115.56 
getForwad->getIntersec(distalL:210.00,distalR:210.00,xL:-188.08,yL:-90.75,xR:207.58,yR:65.01)
getIntersec firstRadius: 210.00 secondRadius: 210.00 firstX: -188.08 firstY: -90.75 secondX: 207.58 secondY: 65.01
MotorStepsToCartesian => MachinePosX:nan MachinePosY:nan XYZ_AXES:3 numVisibleAxes:3
MotorStepsToCartesian => thetaL:224.27=MotorPosX:25916.00/StepsPermmX:115.56 
MotorStepsToCartesian => thetaR:224.27=MotorPosY:3467.00/StepsPermmY:115.56 
getForwad->getIntersec(distalL:210.00,distalR:210.00,xL:-188.08,yL:-90.75,xR:207.58,yR:65.01)
getIntersec firstRadius: 210.00 secondRadius: 210.00 firstX: -188.08 firstY: -90.75 secondX: 207.58 secondY: 65.01
MotorStepsToCartesian => MachinePosX:nan MachinePosY:nan XYZ_AXES:3 numVisibleAxes:3
MotorStepsToCartesian => thetaL:30.00=MotorPosX:3467.00/StepsPermmX:115.56 
MotorStepsToCartesian => thetaR:30.00=MotorPosY:3467.00/StepsPermmY:115.56 
getForwad->getIntersec(distalL:210.00,distalR:210.00,xL:17.58,yL:65.01,xR:207.58,yR:65.01)
getIntersec firstRadius: 210.00 secondRadius: 210.00 firstX: 17.58 firstY: 65.01 secondX: 207.58 secondY: 65.01
MotorStepsToCartesian => MachinePosX:112.58 MachinePosY:252.29 XYZ_AXES:3 numVisibleAxes:3
MotorStepsToCartesian => thetaL:30.00=MotorPosX:3467.00/StepsPermmX:115.56 
MotorStepsToCartesian => thetaR:30.00=MotorPosY:3467.00/StepsPermmY:115.56 
getForwad->getIntersec(distalL:210.00,distalR:210.00,xL:17.58,yL:65.01,xR:207.58,yR:65.01)
getIntersec firstRadius: 210.00 secondRadius: 210.00 firstX: 17.58 firstY: 65.01 secondX: 207.58 secondY: 65.01
MotorStepsToCartesian => MachinePosX:112.58 MachinePosY:252.29 XYZ_AXES:3 numVisibleAxes:3
MotorStepsToCartesian => thetaL:30.00=MotorPosX:3467.00/StepsPermmX:115.56 
MotorStepsToCartesian => thetaR:30.00=MotorPosY:3467.00/StepsPermmY:115.56 
getForwad->getIntersec(distalL:210.00,distalR:210.00,xL:17.58,yL:65.01,xR:207.58,yR:65.01)
getIntersec firstRadius: 210.00 secondRadius: 210.00 firstX: 17.58 firstY: 65.01 secondX: 207.58 secondY: 65.01
MotorStepsToCartesian => MachinePosX:112.58 MachinePosY:252.29 XYZ_AXES:3 numVisibleAxes:3
MotorStepsToCartesian => thetaL:28.00=MotorPosX:3236.00/StepsPermmX:115.56 
MotorStepsToCartesian => thetaR:28.00=MotorPosY:3236.00/StepsPermmY:115.56 
getForwad->getIntersec(distalL:210.00,distalR:210.00,xL:19.78,yL:61.04,xR:209.78,yR:61.04)
getIntersec firstRadius: 210.00 secondRadius: 210.00 firstX: 19.78 firstY: 61.04 secondX: 209.78 secondY: 61.04
MotorStepsToCartesian => MachinePosX:114.78 MachinePosY:248.32 XYZ_AXES:3 numVisibleAxes:3
MotorStepsToCartesian => thetaL:28.00=MotorPosX:3236.00/StepsPermmX:115.56 
MotorStepsToCartesian => thetaR:28.00=MotorPosY:3236.00/StepsPermmY:115.56 
getForwad->getIntersec(distalL:210.00,distalR:210.00,xL:19.78,yL:61.04,xR:209.78,yR:61.04)
getIntersec firstRadius: 210.00 secondRadius: 210.00 firstX: 19.78 firstY: 61.04 secondX: 209.78 secondY: 61.04
MotorStepsToCartesian => MachinePosX:114.78 MachinePosY:248.32 XYZ_AXES:3 numVisibleAxes:3
MotorStepsToCartesian => thetaL:30.00=MotorPosX:3467.00/StepsPermmX:115.56 
MotorStepsToCartesian => thetaR:30.00=MotorPosY:3236.00/StepsPermmY:115.56 
getForwad->getIntersec(distalL:210.00,distalR:210.00,xL:17.58,yL:65.01,xR:209.78,yR:61.04)
getIntersec firstRadius: 210.00 secondRadius: 210.00 firstX: 17.58 firstY: 65.01 secondX: 209.78 secondY: 61.04
MotorStepsToCartesian => MachinePosX:117.53 MachinePosY:249.69 XYZ_AXES:3 numVisibleAxes:3
MotorStepsToCartesian => thetaL:30.00=MotorPosX:3467.00/StepsPermmX:115.56 
MotorStepsToCartesian => thetaR:30.00=MotorPosY:3236.00/StepsPermmY:115.56 
getForwad->getIntersec(distalL:210.00,distalR:210.00,xL:17.58,yL:65.01,xR:209.78,yR:61.04)
getIntersec firstRadius: 210.00 secondRadius: 210.00 firstX: 17.58 firstY: 65.01 secondX: 209.78 secondY: 61.04
MotorStepsToCartesian => MachinePosX:117.53 MachinePosY:249.69 XYZ_AXES:3 numVisibleAxes:3
MotorStepsToCartesian => thetaL:30.00=MotorPosX:3467.00/StepsPermmX:115.56 
MotorStepsToCartesian => thetaR:30.00=MotorPosY:3467.00/StepsPermmY:115.56 
getForwad->getIntersec(distalL:210.00,distalR:210.00,xL:17.58,yL:65.01,xR:207.58,yR:65.01)
getIntersec firstRadius: 210.00 secondRadius: 210.00 firstX: 17.58 firstY: 65.01 secondX: 207.58 secondY: 65.01
MotorStepsToCartesian => MachinePosX:112.58 MachinePosY:252.29 XYZ_AXES:3 numVisibleAxes:3
MotorStepsToCartesian => thetaL:30.00=MotorPosX:3467.00/StepsPermmX:115.56 
MotorStepsToCartesian => thetaR:30.00=MotorPosY:3467.00/StepsPermmY:115.56 
getForwad->getIntersec(distalL:210.00,distalR:210.00,xL:17.58,yL:65.01,xR:207.58,yR:65.01)
getIntersec firstRadius: 210.00 secondRadius: 210.00 firstX: 17.58 firstY: 65.01 secondX: 207.58 secondY: 65.01
MotorStepsToCartesian => MachinePosX:112.58 MachinePosY:252.29 XYZ_AXES:3 numVisibleAxes:3
MotorStepsToCartesian => thetaL:25.00=MotorPosX:2889.00/StepsPermmX:115.56 
MotorStepsToCartesian => thetaR:25.00=MotorPosY:2889.00/StepsPermmY:115.56 
getForwad->getIntersec(distalL:210.00,distalR:210.00,xL:22.82,yL:54.94,xR:212.82,yR:54.94)
getIntersec firstRadius: 210.00 secondRadius: 210.00 firstX: 22.82 firstY: 54.94 secondX: 212.82 secondY: 54.94
MotorStepsToCartesian => MachinePosX:117.82 MachinePosY:242.23 XYZ_AXES:3 numVisibleAxes:3
constraintsOK->cachedInvalid:0 cachedX0:0.00 cachedY0:0.00
getInverse not cantilevered proximalL:130.00 distalL:210.00 xOrigL:-95.00 yOrigL:0.00 x_0:117.82 y_0:242.23
getTheta
getIntersec firstRadius: 130.00 secondRadius: 210.00 firstX: -95.00 firstY: 0.00 secondX: 117.82 secondY: 242.23
getTheta use: 2 x2: 22.82 y2: 54.94 thetaB: 25.00 x1: -55.68 y1: 123.91 thetaA: 72.39
getInverse not cantilevered proximalR:130.00 distalR:210.00 xOrigR:95.00 yOrigR:0.00 x_0:117.82 y_0:242.23
getTheta
getIntersec firstRadius: 130.00 secondRadius: 210.00 firstX: 95.00 firstY: 0.00 secondX: 117.82 secondY: 242.23
getTheta use: 2 x2: 212.82 y2: 54.94 thetaB: 25.00 x1: -10.49 y1: 75.98 thetaA: 144.24
getInverse cachedInvalid 0 => cachedX0:117.82 cachedY0:242.23 cachedX1:117.82 cachedY1:242.23
cachedXL:22.82 cachedYL:54.94 cachedXR:212.82 cachedYR:54.94 cachedThetaR:25.00 cachedXR:212.82
cachedYR:54.94 cachedThetaL:25.00 cachedXL:22.82 cachedYL:54.94
getInverse => cachedInvalid:0 x_0:117.82 y_0:242.23 xL:22.82 yL:54.94 thetaL:25.00 xR:212.82 yR:54.94 thetaR:25.00 x1:117.82 y1:242.23
constraintsOK->cachedInvalid:0 actuatorAngleLMin:-90.00<0 && thetaL:25.00>actuatorAngleLMax:270.00
constraintsOK->cachedInvalid:0 thetaL:25.00 < actuatorAngleLMin:-90.00 || thetaL:25.00 > actuatorAngleLMax:270.00 return false
constraintsOK->cachedInvalid:0 actuatorAngleRMin:-90.00<0 && thetaR:25.00>actuatorAngleRMax:270.00
constraintsOK->cachedInvalid:0 thetaR:25.00 < actuatorAngleRMin:-90.00 || thetaR:25.00 > actuatorAngleRMax:270.00 return false
constraintsOK->cachedInvalid:0 headAngle:53.79 < headAngleMin:15.00 || headAngle:53.79 > headAngleMax:165.00 isnan(headAngle):0 return false
constraintsOK->cachedInvalid:0 angleProxDistL:218.10 < proxDistLAngleMin:0.00 || angleProxDistL:218.10 > proxDistLAngleMax:360.00 isnan(angleProxDistL):0 return false
constraintsOK->cachedInvalid:0 angleProxDistR:271.90 < proxDistRAngleMin:0.00 || angleProxDistR:271.90 > proxDistRAngleMax:360.00 isnan(angleProxDistR):0 return false
constraintsOK->cachedInvalid:0 cachedX0:117.82 cachedY0:242.23
CartesianToMotorSteps => motorPosX = cachedThetaL:25.00 * stespPermm[X_AXIS]115.56
 motorPosY = cachedThetaR:25.00 * stepsPermm[Y_AXIS]115.56
CartesianToMotorSteps => machinePos[0]:117.82 machinePos[1]:242.23 motorPosX:0.00 motorPosY:115.56
CartesianToMotorSteps => XYZ_AXES:3 numVisibleAxes:3
constraintsOK->cachedInvalid:0 cachedX0:117.82 cachedY0:242.23
CartesianToMotorSteps => motorPosX = cachedThetaL:25.00 * stespPermm[X_AXIS]115.56
 motorPosY = cachedThetaR:25.00 * stepsPermm[Y_AXIS]115.56
CartesianToMotorSteps => machinePos[0]:117.82 machinePos[1]:242.23 motorPosX:0.00 motorPosY:115.56
CartesianToMotorSteps => XYZ_AXES:3 numVisibleAxes:3
constraintsOK->cachedInvalid:0 cachedX0:117.82 cachedY0:242.23
getInverse not cantilevered proximalL:130.00 distalL:210.00 xOrigL:-95.00 yOrigL:0.00 x_0:0.00 y_0:0.00
getTheta
getIntersec firstRadius: 130.00 secondRadius: 210.00 firstX: -95.00 firstY: 0.00 secondX: 0.00 secondY: 0.00
getTheta use: 2 x2: -190.66 y2: -88.03 thetaB: 222.62 x1: -190.66 y1: 88.03 thetaA: 137.38
getInverse not cantilevered proximalR:130.00 distalR:210.00 xOrigR:95.00 yOrigR:0.00 x_0:0.00 y_0:0.00
getTheta
getIntersec firstRadius: 130.00 secondRadius: 210.00 firstX: 95.00 firstY: 0.00 secondX: 0.00 secondY: 0.00
getTheta use: 2 x2: 190.66 y2: 88.03 thetaB: 42.62 x1: 190.66 y1: -88.03 thetaA: 317.38
getInverse cachedInvalid 0 => cachedX0:0.00 cachedY0:0.00 cachedX1:0.00 cachedY1:0.00
cachedXL:-190.66 cachedYL:-88.03 cachedXR:190.66 cachedYR:88.03 cachedThetaR:42.62 cachedXR:190.66
cachedYR:88.03 cachedThetaL:222.62 cachedXL:-190.66 cachedYL:-88.03
getInverse => cachedInvalid:0 x_0:0.00 y_0:0.00 xL:-190.66 yL:-88.03 thetaL:222.62 xR:190.66 yR:88.03 thetaR:42.62 x1:0.00 y1:0.00
constraintsOK->cachedInvalid:0 actuatorAngleLMin:-90.00<0 && thetaL:222.62>actuatorAngleLMax:270.00
constraintsOK->cachedInvalid:0 thetaL:222.62 < actuatorAngleLMin:-90.00 || thetaL:222.62 > actuatorAngleLMax:270.00 return false
constraintsOK->cachedInvalid:0 actuatorAngleRMin:-90.00<0 && thetaR:42.62>actuatorAngleRMax:270.00
constraintsOK->cachedInvalid:0 thetaR:42.62 < actuatorAngleRMin:-90.00 || thetaR:42.62 > actuatorAngleRMax:270.00 return false
constraintsOK->cachedInvalid:0 headAngle:180.00 < headAngleMin:15.00 || headAngle:180.00 > headAngleMax:165.00 isnan(headAngle):0 return false
constraintsOK->cachedInvalid:1 cachedX0:0.00 cachedY0:0.00
getInverse not cantilevered proximalL:130.00 distalL:210.00 xOrigL:-95.00 yOrigL:0.00 x_0:0.00 y_0:0.00
getTheta
getIntersec firstRadius: 130.00 secondRadius: 210.00 firstX: -95.00 firstY: 0.00 secondX: 0.00 secondY: 0.00
getTheta use: 2 x2: -190.66 y2: -88.03 thetaB: 222.62 x1: -190.66 y1: 88.03 thetaA: 137.38
getInverse not cantilevered proximalR:130.00 distalR:210.00 xOrigR:95.00 yOrigR:0.00 x_0:0.00 y_0:0.00
getTheta
getIntersec firstRadius: 130.00 secondRadius: 210.00 firstX: 95.00 firstY: 0.00 secondX: 0.00 secondY: 0.00
getTheta use: 2 x2: 190.66 y2: 88.03 thetaB: 42.62 x1: 190.66 y1: -88.03 thetaA: 317.38
getInverse cachedInvalid 0 => cachedX0:0.00 cachedY0:0.00 cachedX1:0.00 cachedY1:0.00
cachedXL:-190.66 cachedYL:-88.03 cachedXR:190.66 cachedYR:88.03 cachedThetaR:42.62 cachedXR:190.66
cachedYR:88.03 cachedThetaL:222.62 cachedXL:-190.66 cachedYL:-88.03
getInverse => cachedInvalid:0 x_0:0.00 y_0:0.00 xL:-190.66 yL:-88.03 thetaL:222.62 xR:190.66 yR:88.03 thetaR:42.62 x1:0.00 y1:0.00
constraintsOK->cachedInvalid:0 actuatorAngleLMin:-90.00<0 && thetaL:222.62>actuatorAngleLMax:270.00
constraintsOK->cachedInvalid:0 thetaL:222.62 < actuatorAngleLMin:-90.00 || thetaL:222.62 > actuatorAngleLMax:270.00 return false
constraintsOK->cachedInvalid:0 actuatorAngleRMin:-90.00<0 && thetaR:42.62>actuatorAngleRMax:270.00
constraintsOK->cachedInvalid:0 thetaR:42.62 < actuatorAngleRMin:-90.00 || thetaR:42.62 > actuatorAngleRMax:270.00 return false
constraintsOK->cachedInvalid:0 headAngle:180.00 < headAngleMin:15.00 || headAngle:180.00 > headAngleMax:165.00 isnan(headAngle):0 return false

M114 outputs:

m114
X:117.819 Y:242.226 Z:0.000 E:0.000 E0:0.0 Count 2889 2889 0 Machine 117.819 242.226 0.000 Bed comp 0.000
ok

VIDEO OF PROCESS STEPS

JoergS5 · 5 Nov 2021, 16:46

This post is deleted!

JoergS5 · 5 Nov 2021, 17:20

@rutku the values seem to be all ok for me.

Homing works, debug tells that the actuators move back 5 degree to 25 like planned, then trying to move to X0 Y0 is not possible because of restriction of parameter A maximum value:

From https://duet3d.dozuki.com/Guide/Five+Bar+Parallel+SCARA/24#s90 :
Annn:mmm:ppp:qqq:rrr:sss nnn is the minimum angle between the distal arms (constr in the first image) in degrees, mmm the maximum....

Your setting is 165 degree maximum angle of distal arms, and X0 Y0 is only reachable with distal arms nearly straight line.

line 131 confirms this check:
constraintsOK->cachedInvalid:0 headAngle:180.00 < headAngleMin:15.00 || headAngle:180.00 > headAngleMax:165.00 isnan(headAngle):0 return false

rutku · 11 May 2021, 19:53

@joergs5 Yes! Worked!

Work Mode 1 but the arms worked at different angles. They work in a very limited area. Could it be from the location of the endstops?

VIDEO

config.g

M669 K9 L1 X-95:95 Y0:0 P130:130 D200:200:0:0 B30:30 A0:180:0:360:0:360 C0:270:0:270

debug_output.txt

JoergS5 · 5 Nov 2021, 20:47

@rutku your actuators are 190 away (X -95 to X 95), the proximal arms have length 260, distal arms have length 400, so you cannot rotate to the position of horizontal arms 180/0 degree, because the distance of proximal+distance is 190+260 = 450, and your distal arms are not long enough "to close the gap". ~~Your video starting at 1:16 the angle of the distal arms is again near 180 degree and violates the A max value parameter.~~ (I see you changed A to 180. The limit will be the arm lengths). A "secure" area is when the arms are forward, like 90 degree both.

To clarify: you place the endstops at one location and the B parameter must tell the firmware the correct angle for this endstops. Because when you turn on the Duet, he doesn't know at what position the arms and steppers are. Homing has only one task: tell the firmware at which arm/stepper position the endstop is triggered, then set a value. Kinematics like Cartesian/CoreXY set the value of G1 H1 movements to the M208 value, but here it is set to the value of the B parameter.

The procedure I follow when I am not sure where the print area is:

home with both actuators endstop 30 degree
move to an area which is "secure" like G1 X-50 Y20 (relative) (or measure where the absolute coordinate is where both proximal arms are 90 degree)
from there mark where you can move with small G1 in every direction

I assembled a pen as "hotend" and draw on a sheet of paper.

JoergS5 · 5 Nov 2021, 21:28

@rutku with your position in video at 1:11:

When you try to move X10, this is not possible: you could turn the left arm up (to a lower angle) and right arm to a low one, but this movement crosses the singularity of unprintable area (the 400 too short for the 450). When a G0/G1 move is done, the kinematics checks whether the movement path is reachable the hole path.

BTW: you could reach your destination if you move the hotend to a high Y value first, then approaching the goal. This is a risk later, when printing an object, because reachability depends on where you start. In other words it depends on how the slicer wants to draw the lines. Later for printing it is better to restrict M208 to a safe rectangular print area and print only in this area.

Please see
https://forum.duet3d.com/topic/10409/joergs5-parallel-five-bar-scara/30
for the complex print area, where some areas on the Y0 line or near it is not printable.

rutku · 13 May 2021, 15:33

@joergs5 Hello, I did what you said. I set the right arm to 90 degrees and the left arm to 45 degrees. I used optical endstop. It worked great. G0 X0 Y0 position is not wrong?

Is @bondus repository up to date? I tried but there was no change.

config.g

M350 X16 Y16 I1 ;S3 ; Configure microstepping with interpolation
M669 K9 L1 X-95:95 Y0:0 P130:130 D200:200:0:0 B45:45 A0:180:0:360:0:360 C-180:270:-180:270 
M92 X115.555556 Y115.555556 ; Set steps per mm

debug_output2.txt

VIDEO

JoergS5 · 13 May 2021, 16:41

@rutku G0 X0 Y0 is probably not reachable.

Do you have a question for the debug_output or video?

rutku · 13 May 2021, 20:23

@joergs5 Hi, working mode 1 is selected but the levers like working mode 2 are moving. I made the angle of Constr "0: 180" degrees "15: 165" degrees. Nothing changed. I wanted to show it with video and output.

I wanted to draw 20x20 squares. But very different shape appeared. What is the reason?

Thank you so much for your patience. You have been very helpful.

JoergS5 · 13 May 2021, 21:26

@rutku there must be something wrong with the setup, because your X0 is close to the first wheel, but should be in the middle between the wheels. This change in coordinates produces the curved lines.

Maybe your homing didn't work like before, please check the angles and position when you finished homing (without the last G0 X0 Y0 line).

After homing please try to go to absolute coordinate
G90 G0 X0 Y50
and verify that the position is in the middle between the two big wheels.

If you homing angles are correct, but the X0 Y50 is at the wrong place, you can check

whether the gear ratio and M92 are correctly calculated
the arm lengths are correct. The length is always from the middle of a hinge to middle of the other hinge
whether the endstop positions are 45 degree, like is set in config now

o_lampe · 22 May 2021, 06:30

I followed this thread with great interest, but it got stuck in the middle...are all problems solved?
What was the solution and final layout?

I ask, because I look for an excuse to build a fancy Capstan geared drive, either for a SCARA or robot arm.
I'd use Aramid fishing line instead of steel cable and spur and pinion gear hardware from the orbiter/BMG extruder.

JoergS5 · 23 May 2021, 10:22

@o_lampe I didn't hear from rutku, but the firmware is ok so far, bondus has made a working scara here: https://hackaday.com/2020/03/18/a-practical-dual-arm-scara-3d-printer/ And if you find a bug, tell me, I'll fix it.

The Capstan is interesting for robot gear also, but 1:30 is difficult to achieve with one stage, because you need a very big wheel. Therefore I use 2 stage gears 1:3 (or 1:2) and 1:10. Please go ahead!

rutku · 23 May 2021, 19:43

@joergs5 @o_lampe
Hi, I didn't get the calibration. I've been dealing with a week calibration but draws the same shapes. @bondus had not shared a detail about calibration. I didn't mean to bother @JoergS5 on that.

I didn't understand the "Step Calibration" portion in the file where the bond is shared.

https://forum.duet3d.com/post/138052

JoergS5 · 23 May 2021, 20:16

@rutku the step calibration in the link mentioned is to calculate the M92 values.

What is the number of teeth of your small and big pulley, is it a standard 200 step stepper and the microstep settingis 16? The goal is to calculate how many steps are needed to rotate by 1 degree. Please tell the numbers, then I will help calculating.

The google calc provided in the link is readonly, but the formula is:
microsteps / stepperdeg * bigwheelteeth / smallwheelteeth
The result is the M92 value.
Example: 16 microsteps, stepper 1.8 degree for one step (= stepper with 200 steps, 360/200 = 1.8), 200 teeth bigwheel, 20 teethsmallwheel => 16/1.8*200/20 = 88.88888

rutku · 25 May 2021, 05:50

@joergs5

microsteps = 128
stepper Degree = 1.8
Teeth bigwheel = 260
Teeth smallwheel = 20

M92 = (128/1.8) * (260/20) = 924.444444

square.gcode

G90
G1 X0 Y90
G1 X0 Y140
G1 X50 Y140
G1 X50 Y90
G1 X0 Y90

JoergS5 · 25 May 2021, 06:01

@rutku there are some ideas you can check:

after your tests, please make M122 and check for hiccups. 128 microsteps could mean you loose steps => correction: I remember you're using hardware which will not report hiccups. You can try to reduce microsteps, but then changing M92 also. You can reduce speed with F parameter (eg G91 G1 H2 X10 F100) also without changing the values and check whether the lines are better then. Reducing speed gives your controller more time to calculate the segments.
you can verify that your setting are correct by testing:

Home axis 1 to let's say 45 degree (to verify: M669 B first value is 45, arm is at 45 degree position after homing). Make M114 and check the first value of the Count values. This must be M92 value * degree, i.e. 924.4444 * 45 = 41600. Please rotate the axis to example 90 degree (with G91 G1 H2 X90)and make M114 again, the Count value should now be 83200 and the arm should be at 90 degree position.

You can verify additionally the resulting position: verify that the (0,50) position is 5 cm away from your x axis and in the middle of the two wheels. I cannot see it in your image, but the (50,90) and (50,140) must be on the vertical line between the wheels.

Having correct angles is critical for your line precision (straight or curved), so please measure exaclty. I used this idea:

https://forum.duet3d.com/topic/14996/five-bar-parallel-scara-prototypes/10

Another thing to check is whether your arms lengtsh are correct, please verify the lengths:

The red lines are the lenghts, from middle of hinge to middle of other hinge. The green line is the starting point of the first line.

o_lampe · 25 May 2021, 06:37

@joergs5 said in Five bar Parallel SCARA print area problem:

The Capstan is interesting for robot gear also

The good thing about Capstan is, you don't have to print a big wheel with precise teeth. I also had good experience with Aramid line in a non-slipping config. I think it will run really smooth (no tooth-mesh problems)
I should start a new thread about it.

rutku · 29 May 2021, 11:02

@joergs5 Hi, I have done the steps you say. But I have received different results.

m122

m122
=== Diagnostics ===
RepRapFirmware for STM32F4 based Boards version 3.2.2_2 running on STM32F4
Used output buffers: 1 of 40 (11 max)
=== RTOS ===
Static ram: 32296
Dynamic ram: 60988 of which 380 recycled
Never used RAM 18200, free system stack 214 words
Tasks: NETWORK(ready,144) HEAT(blocked,369) MAIN(running,572) IDLE(ready,19)
Owned mutexes: WiFi(NETWORK) USB(MAIN)
=== Platform ===
Last reset 00:11:55 ago, cause: [power on/off]
Last software reset at 2021-05-19 00:16, reason: User, GCodes spinning, available RAM 18200, slot 2
Software reset code 0x0003 HFSR 0x00000000 CFSR 0x00000000 ICSR 0x00454000 BFAR 0xe000ed38 SP 0x00000000 Task MAIN Freestk 0 n/a
Error status: 0x00
Aux0 errors 0,134218187,134218187
MCU temperature: min 31.6, current 42.0, max 42.5
Driver 0: position 48996, standstill, SG min/max 0/32, error r/w 0/0, ifcnt 16, cnt r/w 61932/16, timeout 0, failedOp 0xff
Driver 1: position 83200, standstill, SG min/max 0/40, error r/w 0/0, ifcnt 17, cnt r/w 61931/17, timeout 0, failedOp 0xff
Driver 2: position 0, standstill, SG min/max 0/0, error r/w 0/0, ifcnt 9, cnt r/w 61938/9, timeout 0, failedOp 0xff
Driver 3: position 0, standstill, SG min/max 0/0, error r/w 0/0, ifcnt 9, cnt r/w 61938/9, timeout 0, failedOp 0xff
Driver 4: position 0
Driver 5: position 0
Driver 6: position 0
Driver 7: position 0
Driver 8: position 0
Driver 9: position 0
Driver 10: position 0
Date/time: 2021-05-29 13:37:04
Slowest loop: 17.76ms; fastest: 0.07ms
=== Storage ===
Free file entries: 10
SD card 0 detected
SD card longest read time 2.8ms, write time 0.0ms, max retries 0
=== Move ===
DMs created 83, maxWait 328438ms, bed compensation in use: none, comp offset 0.000
=== DDARing ===
Scheduled moves 6, completed moves 6, hiccups 0, stepErrors 0, LaErrors 0, Underruns [0, 0, 0], CDDA state -1
=== Heat ===
Bed heaters = -1, chamberHeaters = -1
=== GCodes ===
Segments left: 0
Movement lock held by null
HTTP is idle in state(s) 0
File is idle in state(s) 0
USB is ready with "m122" in state(s) 0
Aux is idle in state(s) 0
Trigger is idle in state(s) 0
Queue is idle in state(s) 0
LCD is idle in state(s) 0
Daemon is idle in state(s) 0
Autopause is idle in state(s) 0
Code queue is empty.
=== Network ===
Slowest loop: 7.11ms; fastest: 0.00ms
Responder states: HTTP(0) HTTP(0) HTTP(0) HTTP(0)
HTTP sessions: 1 of 8
- WiFi -
Network state is active
WiFi module is connected to access point 
Failed messages: pending 0, notready 0, noresp 0
WiFi firmware version 1.25-01S-D
WiFi MAC address 50:78:b3:f3:41:84
WiFi Vcc 3.38, reset reason Turned on by main processor
WiFi flash size 4194304, free heap 36832
WiFi IP address 192.168.1.20
WiFi signal strength -73dBm, mode 802.11n, reconnections 0, sleep mode modem
Clock register 00004002
Socket states: 0 0 0 0 0 0 0 0
ok

config.g

M350 X128 Y128 I1 ;S3 ; Configure microstepping with interpolation
M669 K9 L1 X-95:93 Y0:0 P126:133 D210:213:0:0 B53:90 A15:165:0:360:0:360 C-90:90:-90:90 
M92 X924.444444 Y924.444444 ; Set steps per mm

m114

m114
X:-24.654 Y:310.557 Z:0.000 E:0.000 E0:0.0 Count 48996 83200 0 Machine -24.654 310.557 0.000 Bed comp 0.000
ok

924.444444 * 53 = 48.995,55532 OK....!

G91 G1 H2 X90

G91 G1 H2 X90

MotorStepsToCartesian => thetaL:143.00=MotorPosX:132196.00/StepsPermmX:924.44 
MotorStepsToCartesian => thetaR:143.00=MotorPosY:83200.00/StepsPermmY:924.44 
getForwad => getIntersec(distalL:210.00,distalR:213.00,xL:-195.63,yL:75.83,xR:93.00,yR:133.00)
getIntersec firstRadius: 210.00 secondRadius: 213.00 firstX: -195.63 firstY: 75.83 secondX: 93.00 secondY: 133.00
getTurn => turn:-44706.59 = (x2:-82.95 - x1:-195.63) * (y3:133.00 - y1:75.83) - (y2:253.04 - y1:75.83) * (x3:93.00 - x1:-195.63)
getTurn => turn:44706.59 = (x2:-23.91 - x1:-195.63) * (y3:133.00 - y1:75.83) - (y2:-45.05 - y1:75.83) * (x3:93.00 - x1:-195.63)
getTurn => turn:-26376.60 = (x2:-195.63 - x1:-95.00) * (y3:253.04 - y1:0.00) - (y2:75.83 - y1:0.00) * (x3:-82.95 - x1:-95.00)
getTurn => turn:23401.72 = (x2:93.00 - x1:93.00) * (y3:253.04 - y1:0.00) - (y2:133.00 - y1:0.00) * (x3:-82.95 - x1:93.00)
getForwad => workmode:1 turnLeft:-26376.60 turnRight:23401.72
MotorStepsToCartesian => MachinePosX:nan MachinePosY:nan XYZ_AXES:3 numVisibleAxes:3ok

MotorStepsToCartesian => thetaL:143.00=MotorPosX:132196.00/StepsPermmX:924.44 
MotorStepsToCartesian => thetaR:143.00=MotorPosY:83200.00/StepsPermmY:924.44 
getForwad => getIntersec(distalL:210.00,distalR:213.00,xL:-195.63,yL:75.83,xR:93.00,yR:133.00)
getIntersec firstRadius: 210.00 secondRadius: 213.00 firstX: -195.63 firstY: 75.83 secondX: 93.00 secondY: 133.00
getTurn => turn:-44706.59 = (x2:-82.95 - x1:-195.63) * (y3:133.00 - y1:75.83) - (y2:253.04 - y1:75.83) * (x3:93.00 - x1:-195.63)
getTurn => turn:44706.59 = (x2:-23.91 - x1:-195.63) * (y3:133.00 - y1:75.83) - (y2:-45.05 - y1:75.83) * (x3:93.00 - x1:-195.63)
getTurn => turn:-26376.60 = (x2:-195.63 - x1:-95.00) * (y3:253.04 - y1:0.00) - (y2:75.83 - y1:0.00) * (x3:-82.95 - x1:-95.00)
getTurn => turn:23401.72 = (x2:93.00 - x1:93.00) * (y3:253.04 - y1:0.00) - (y2:133.00 - y1:0.00) * (x3:-82.95 - x1:93.00)
getForwad => workmode:1 turnLeft:-26376.60 turnRight:23401.72
MotorStepsToCartesian => MachinePosX:nan MachinePosY:nan XYZ_AXES:3 numVisibleAxes:3

m114

m114
X:9999.900 Y:9999.900 Z:0.000 E:0.000 E0:0.0 Count 132196 83200 0 Machine 9999.900 9999.900 0.000 Bed comp 0.000
ok

132196 / 924.44444 = 143,0004814567331 degree .Why?

JoergS5 · 29 May 2021, 11:23

@rutku said in Five bar Parallel SCARA print area problem:

G91 G1 H2 X90

ok, first, I made a fault for testing: G91 means relative, but I wanted the arm to rotate to the 90 degree position, so this must be G90 G1 H2 X90.

The relative rotation means 53 degree plus 90, which is your 143 degree (the Count value is about 132T). But the arm seems to rotate into the wrong direction, so 53-90 = -37 degree, which looks correct of the arm position in the image*). Please change the S0 / S1 value for the stepper definition and retry.

If it's
M569 P0 S1 ; Drive 0 (X) goes forwards
then please change to
M569 P0 S0
or other round.

*) on the image the arm rotated to position 141, but it should be 143, so you can make the M92 value a bit higher. But I don't know the reason, can be some error in arm length or hinge play.