Another SCARA build

Hello all. I have been reading these posts for a while and had to try building a SCARA machine. I used the Rob Dobson design, A New SandBot | robdobson.com, and I am running into trouble making it follow the pattern from sandify.

I can run the code: G10, X6 and it will make 1 full revolution clockwise. I can do the same with G10 Y6 for the elbow. But if I just move the X(shoulder) the elbow will also turn a bit just from “walking” around the gear. I have seen a few posts mention this problem but I have not seen if a solution has been discussed. It seems like there are several successful builds and I just dont know what i am doing wrong.

The way it works now, I cannot draw a simple square. I can draw a circle if I use G10 X6 Y6.

Using an arduino uno with CNC shield and grbl on UGS.

Thoughts please?

I think you mean G1, not G10, right?

Looking at a simple square (which moves counter clockwise):

;
; File name: 'sandify'
; File type: scara
;

G1 F60
G1 X1.526 Y-0.026
G1 X1.526 Y-0.042
G1 X1.525 Y-0.057
G1 X1.524 Y-0.072
G1 X1.523 Y-0.088
G1 X1.521 Y-0.103
G1 X1.519 Y-0.119
G1 X1.517 Y-0.134
G1 X1.515 Y-0.149
G1 X1.513 Y-0.165
G1 X1.510 Y-0.181
G1 X1.507 Y-0.196
G1 X1.503 Y-0.212
G1 X1.500 Y-0.228
G1 X1.496 Y-0.243
G1 X1.492 Y-0.259
G1 X1.487 Y-0.275
G1 X1.483 Y-0.291
G1 X1.478 Y-0.307
G1 X1.473 Y-0.323
G1 X1.467 Y-0.339
G1 X1.462 Y-0.355
G1 X1.456 Y-0.371
G1 X1.449 Y-0.387
G1 X1.443 Y-0.404
G1 X1.436 Y-0.420
G1 X1.429 Y-0.436
G1 X1.421 Y-0.453
G1 X1.414 Y-0.469
G1 X1.406 Y-0.486
G1 X1.397 Y-0.502
G1 X1.389 Y-0.519
G1 X1.380 Y-0.536
G1 X1.371 Y-0.553
G1 X1.362 Y-0.569
G1 X1.352 Y-0.586
G1 X1.342 Y-0.603
G1 X1.332 Y-0.620
G1 X1.321 Y-0.637
G1 X1.310 Y-0.654
G1 X1.299 Y-0.671
G1 X1.288 Y-0.688
G1 X1.276 Y-0.705
G1 X1.264 Y-0.722
G1 X1.252 Y-0.739
G1 X1.240 Y-0.755
G1 X1.227 Y-0.772
G1 X1.214 Y-0.789
G1 X1.201 Y-0.806
G1 X1.188 Y-0.823
G1 X1.174 Y-0.840
G1 X1.161 Y-0.857
G1 X1.146 Y-0.873
G1 X1.132 Y-0.890
G1 X1.118 Y-0.906
G1 X1.103 Y-0.923
G1 X1.088 Y-0.939
G1 X1.073 Y-0.955
G1 X1.058 Y-0.972
G1 X1.043 Y-0.988
G1 X1.027 Y-1.004
G1 X1.011 Y-1.019
G1 X0.996 Y-1.035
G1 X0.980 Y-1.050
G1 X0.964 Y-1.066
G1 X0.947 Y-1.081
G1 X0.931 Y-1.096
G1 X0.915 Y-1.110
G1 X0.898 Y-1.125
G1 X0.882 Y-1.139
G1 X0.865 Y-1.154
G1 X0.848 Y-1.167
G1 X0.831 Y-1.181
G1 X0.815 Y-1.195
G1 X0.798 Y-1.208
G1 X0.781 Y-1.221
G1 X0.764 Y-1.234
G1 X0.747 Y-1.246
G1 X0.730 Y-1.258
G1 X0.713 Y-1.270
G1 X0.696 Y-1.282
G1 X0.679 Y-1.294
G1 X0.662 Y-1.305
G1 X0.645 Y-1.316
G1 X0.628 Y-1.326
G1 X0.611 Y-1.337
G1 X0.595 Y-1.347
G1 X0.578 Y-1.357
G1 X0.561 Y-1.366
G1 X0.544 Y-1.375
G1 X0.527 Y-1.384
G1 X0.511 Y-1.393
G1 X0.494 Y-1.402
G1 X0.478 Y-1.410
G1 X0.461 Y-1.417
G1 X0.445 Y-1.425
G1 X0.428 Y-1.432
G1 X0.412 Y-1.439
G1 X0.395 Y-1.446
G1 X0.379 Y-1.452
G1 X0.363 Y-1.459
G1 X0.347 Y-1.464
G1 X0.331 Y-1.470
G1 X0.315 Y-1.475
G1 X0.299 Y-1.480
G1 X0.283 Y-1.485
G1 X0.267 Y-1.490
G1 X0.251 Y-1.494
G1 X0.235 Y-1.498
G1 X0.220 Y-1.502
G1 X0.204 Y-1.505
G1 X0.188 Y-1.508
G1 X0.173 Y-1.511
G1 X0.157 Y-1.514
G1 X0.142 Y-1.516
G1 X0.126 Y-1.518
G1 X0.111 Y-1.520
G1 X0.095 Y-1.522
G1 X0.080 Y-1.523
G1 X0.065 Y-1.525
G1 X0.049 Y-1.525
G1 X0.034 Y-1.526
G1 X0.026 Y-1.526
G1 X0.026 Y-1.542
G1 X0.025 Y-1.557
G1 X0.024 Y-1.572
G1 X0.023 Y-1.588
G1 X0.021 Y-1.603
G1 X0.019 Y-1.619
G1 X0.017 Y-1.634
G1 X0.015 Y-1.649
G1 X0.013 Y-1.665
G1 X0.010 Y-1.681
G1 X0.007 Y-1.696
G1 X0.003 Y-1.712
G1 X-0.000 Y-1.728
G1 X-0.004 Y-1.743
G1 X-0.008 Y-1.759
G1 X-0.013 Y-1.775
G1 X-0.017 Y-1.791
G1 X-0.022 Y-1.807
G1 X-0.027 Y-1.823
G1 X-0.033 Y-1.839
G1 X-0.038 Y-1.855
G1 X-0.044 Y-1.871
G1 X-0.051 Y-1.887
G1 X-0.057 Y-1.904
G1 X-0.064 Y-1.920
G1 X-0.071 Y-1.936
G1 X-0.079 Y-1.953
G1 X-0.086 Y-1.969
G1 X-0.094 Y-1.986
G1 X-0.103 Y-2.002
G1 X-0.111 Y-2.019
G1 X-0.120 Y-2.036
G1 X-0.129 Y-2.053
G1 X-0.138 Y-2.069
G1 X-0.148 Y-2.086
G1 X-0.158 Y-2.103
G1 X-0.168 Y-2.120
G1 X-0.179 Y-2.137
G1 X-0.190 Y-2.154
G1 X-0.201 Y-2.171
G1 X-0.212 Y-2.188
G1 X-0.224 Y-2.205
G1 X-0.236 Y-2.222
G1 X-0.248 Y-2.239
G1 X-0.260 Y-2.255
G1 X-0.273 Y-2.272
G1 X-0.286 Y-2.289
G1 X-0.299 Y-2.306
G1 X-0.312 Y-2.323
G1 X-0.326 Y-2.340
G1 X-0.339 Y-2.357
G1 X-0.354 Y-2.373
G1 X-0.368 Y-2.390
G1 X-0.382 Y-2.406
G1 X-0.397 Y-2.423
G1 X-0.412 Y-2.439
G1 X-0.427 Y-2.455
G1 X-0.442 Y-2.472
G1 X-0.457 Y-2.488
G1 X-0.473 Y-2.504
G1 X-0.489 Y-2.519
G1 X-0.504 Y-2.535
G1 X-0.520 Y-2.550
G1 X-0.536 Y-2.566
G1 X-0.553 Y-2.581
G1 X-0.569 Y-2.596
G1 X-0.585 Y-2.610
G1 X-0.602 Y-2.625
G1 X-0.618 Y-2.639
G1 X-0.635 Y-2.654
G1 X-0.652 Y-2.667
G1 X-0.669 Y-2.681
G1 X-0.685 Y-2.695
G1 X-0.702 Y-2.708
G1 X-0.719 Y-2.721
G1 X-0.736 Y-2.734
G1 X-0.753 Y-2.746
G1 X-0.770 Y-2.758
G1 X-0.787 Y-2.770
G1 X-0.804 Y-2.782
G1 X-0.821 Y-2.794
G1 X-0.838 Y-2.805
G1 X-0.855 Y-2.816
G1 X-0.872 Y-2.826
G1 X-0.889 Y-2.837
G1 X-0.905 Y-2.847
G1 X-0.922 Y-2.857
G1 X-0.939 Y-2.866
G1 X-0.956 Y-2.875
G1 X-0.973 Y-2.884
G1 X-0.989 Y-2.893
G1 X-1.006 Y-2.902
G1 X-1.022 Y-2.910
G1 X-1.039 Y-2.917
G1 X-1.055 Y-2.925
G1 X-1.072 Y-2.932
G1 X-1.088 Y-2.939
G1 X-1.105 Y-2.946
G1 X-1.121 Y-2.952
G1 X-1.137 Y-2.959
G1 X-1.153 Y-2.964
G1 X-1.169 Y-2.970
G1 X-1.185 Y-2.975
G1 X-1.201 Y-2.980
G1 X-1.217 Y-2.985
G1 X-1.233 Y-2.990
G1 X-1.249 Y-2.994
G1 X-1.265 Y-2.998
G1 X-1.280 Y-3.002
G1 X-1.296 Y-3.005
G1 X-1.312 Y-3.008
G1 X-1.327 Y-3.011
G1 X-1.343 Y-3.014
G1 X-1.358 Y-3.016
G1 X-1.374 Y-3.018
G1 X-1.389 Y-3.020
G1 X-1.405 Y-3.022
G1 X-1.420 Y-3.023
G1 X-1.435 Y-3.025
G1 X-1.451 Y-3.025
G1 X-1.466 Y-3.026
G1 X-1.474 Y-3.026
G1 X-1.474 Y-3.042
G1 X-1.475 Y-3.057
G1 X-1.476 Y-3.072
G1 X-1.477 Y-3.088
G1 X-1.479 Y-3.103
G1 X-1.481 Y-3.119
G1 X-1.483 Y-3.134
G1 X-1.485 Y-3.149
G1 X-1.487 Y-3.165
G1 X-1.490 Y-3.181
G1 X-1.493 Y-3.196
G1 X-1.497 Y-3.212
G1 X-1.500 Y-3.228
G1 X-1.504 Y-3.243
G1 X-1.508 Y-3.259
G1 X-1.513 Y-3.275
G1 X-1.517 Y-3.291
G1 X-1.522 Y-3.307
G1 X-1.527 Y-3.323
G1 X-1.533 Y-3.339
G1 X-1.538 Y-3.355
G1 X-1.544 Y-3.371
G1 X-1.551 Y-3.387
G1 X-1.557 Y-3.404
G1 X-1.564 Y-3.420
G1 X-1.571 Y-3.436
G1 X-1.579 Y-3.453
G1 X-1.586 Y-3.469
G1 X-1.594 Y-3.486
G1 X-1.603 Y-3.502
G1 X-1.611 Y-3.519
G1 X-1.620 Y-3.536
G1 X-1.629 Y-3.553
G1 X-1.638 Y-3.569
G1 X-1.648 Y-3.586
G1 X-1.658 Y-3.603
G1 X-1.668 Y-3.620
G1 X-1.679 Y-3.637
G1 X-1.690 Y-3.654
G1 X-1.701 Y-3.671
G1 X-1.712 Y-3.688
G1 X-1.724 Y-3.705
G1 X-1.736 Y-3.722
G1 X-1.748 Y-3.739
G1 X-1.760 Y-3.755
G1 X-1.773 Y-3.772
G1 X-1.786 Y-3.789
G1 X-1.799 Y-3.806
G1 X-1.812 Y-3.823
G1 X-1.826 Y-3.840
G1 X-1.839 Y-3.857
G1 X-1.854 Y-3.873
G1 X-1.868 Y-3.890
G1 X-1.882 Y-3.906
G1 X-1.897 Y-3.923
G1 X-1.912 Y-3.939
G1 X-1.927 Y-3.955
G1 X-1.942 Y-3.972
G1 X-1.957 Y-3.988
G1 X-1.973 Y-4.004
G1 X-1.989 Y-4.019
G1 X-2.004 Y-4.035
G1 X-2.020 Y-4.050
G1 X-2.036 Y-4.066
G1 X-2.053 Y-4.081
G1 X-2.069 Y-4.096
G1 X-2.085 Y-4.110
G1 X-2.102 Y-4.125
G1 X-2.118 Y-4.139
G1 X-2.135 Y-4.154
G1 X-2.152 Y-4.167
G1 X-2.169 Y-4.181
G1 X-2.185 Y-4.195
G1 X-2.202 Y-4.208
G1 X-2.219 Y-4.221
G1 X-2.236 Y-4.234
G1 X-2.253 Y-4.246
G1 X-2.270 Y-4.258
G1 X-2.287 Y-4.270
G1 X-2.304 Y-4.282
G1 X-2.321 Y-4.294
G1 X-2.338 Y-4.305
G1 X-2.355 Y-4.316
G1 X-2.372 Y-4.326
G1 X-2.389 Y-4.337
G1 X-2.405 Y-4.347
G1 X-2.422 Y-4.357
G1 X-2.439 Y-4.366
G1 X-2.456 Y-4.375
G1 X-2.473 Y-4.384
G1 X-2.489 Y-4.393
G1 X-2.506 Y-4.402
G1 X-2.522 Y-4.410
G1 X-2.539 Y-4.417
G1 X-2.555 Y-4.425
G1 X-2.572 Y-4.432
G1 X-2.588 Y-4.439
G1 X-2.605 Y-4.446
G1 X-2.621 Y-4.452
G1 X-2.637 Y-4.459
G1 X-2.653 Y-4.464
G1 X-2.669 Y-4.470
G1 X-2.685 Y-4.475
G1 X-2.701 Y-4.480
G1 X-2.717 Y-4.485
G1 X-2.733 Y-4.490
G1 X-2.749 Y-4.494
G1 X-2.765 Y-4.498
G1 X-2.780 Y-4.502
G1 X-2.796 Y-4.505
G1 X-2.812 Y-4.508
G1 X-2.827 Y-4.511
G1 X-2.843 Y-4.514
G1 X-2.858 Y-4.516
G1 X-2.874 Y-4.518
G1 X-2.889 Y-4.520
G1 X-2.905 Y-4.522
G1 X-2.920 Y-4.523
G1 X-2.935 Y-4.525
G1 X-2.951 Y-4.525
G1 X-2.966 Y-4.526
G1 X-2.974 Y-4.526
G1 X-2.974 Y-4.542
G1 X-2.975 Y-4.557
G1 X-2.976 Y-4.572
G1 X-2.977 Y-4.588
G1 X-2.979 Y-4.603
G1 X-2.981 Y-4.619
G1 X-2.983 Y-4.634
G1 X-2.985 Y-4.649
G1 X-2.987 Y-4.665
G1 X-2.990 Y-4.681
G1 X-2.993 Y-4.696
G1 X-2.997 Y-4.712
G1 X-3.000 Y-4.728
G1 X-3.004 Y-4.743
G1 X-3.008 Y-4.759
G1 X-3.013 Y-4.775
G1 X-3.017 Y-4.791
G1 X-3.022 Y-4.807
G1 X-3.027 Y-4.823
G1 X-3.033 Y-4.839
G1 X-3.038 Y-4.855
G1 X-3.044 Y-4.871
G1 X-3.051 Y-4.887
G1 X-3.057 Y-4.904
G1 X-3.064 Y-4.920
G1 X-3.071 Y-4.936
G1 X-3.079 Y-4.953
G1 X-3.086 Y-4.969
G1 X-3.094 Y-4.986
G1 X-3.103 Y-5.002
G1 X-3.111 Y-5.019
G1 X-3.120 Y-5.036
G1 X-3.129 Y-5.053
G1 X-3.138 Y-5.069
G1 X-3.148 Y-5.086
G1 X-3.158 Y-5.103
G1 X-3.168 Y-5.120
G1 X-3.179 Y-5.137
G1 X-3.190 Y-5.154
G1 X-3.201 Y-5.171
G1 X-3.212 Y-5.188
G1 X-3.224 Y-5.205
G1 X-3.236 Y-5.222
G1 X-3.248 Y-5.239
G1 X-3.260 Y-5.255
G1 X-3.273 Y-5.272
G1 X-3.286 Y-5.289
G1 X-3.299 Y-5.306
G1 X-3.312 Y-5.323
G1 X-3.326 Y-5.340
G1 X-3.339 Y-5.357
G1 X-3.354 Y-5.373
G1 X-3.368 Y-5.390
G1 X-3.382 Y-5.406
G1 X-3.397 Y-5.423
G1 X-3.412 Y-5.439
G1 X-3.427 Y-5.455
G1 X-3.442 Y-5.472
G1 X-3.457 Y-5.488
G1 X-3.473 Y-5.504
G1 X-3.489 Y-5.519
G1 X-3.504 Y-5.535
G1 X-3.520 Y-5.550
G1 X-3.536 Y-5.566
G1 X-3.553 Y-5.581
G1 X-3.569 Y-5.596
G1 X-3.585 Y-5.610
G1 X-3.602 Y-5.625
G1 X-3.618 Y-5.639
G1 X-3.635 Y-5.654
G1 X-3.652 Y-5.667
G1 X-3.669 Y-5.681
G1 X-3.685 Y-5.695
G1 X-3.702 Y-5.708
G1 X-3.719 Y-5.721
G1 X-3.736 Y-5.734
G1 X-3.753 Y-5.746
G1 X-3.770 Y-5.758
G1 X-3.787 Y-5.770
G1 X-3.804 Y-5.782
G1 X-3.821 Y-5.794
G1 X-3.838 Y-5.805
G1 X-3.855 Y-5.816
G1 X-3.872 Y-5.826
G1 X-3.889 Y-5.837
G1 X-3.905 Y-5.847
G1 X-3.922 Y-5.857
G1 X-3.939 Y-5.866
G1 X-3.956 Y-5.875
G1 X-3.973 Y-5.884
G1 X-3.989 Y-5.893
G1 X-4.006 Y-5.902
G1 X-4.022 Y-5.910
G1 X-4.039 Y-5.917
G1 X-4.055 Y-5.925
G1 X-4.072 Y-5.932
G1 X-4.088 Y-5.939
G1 X-4.105 Y-5.946
G1 X-4.121 Y-5.952
G1 X-4.137 Y-5.959
G1 X-4.153 Y-5.964
G1 X-4.169 Y-5.970
G1 X-4.185 Y-5.975
G1 X-4.201 Y-5.980
G1 X-4.217 Y-5.985
G1 X-4.233 Y-5.990
G1 X-4.249 Y-5.994
G1 X-4.265 Y-5.998
G1 X-4.280 Y-6.002
G1 X-4.296 Y-6.005
G1 X-4.312 Y-6.008
G1 X-4.327 Y-6.011
G1 X-4.343 Y-6.014
G1 X-4.358 Y-6.016
G1 X-4.374 Y-6.018
G1 X-4.389 Y-6.020
G1 X-4.405 Y-6.022
G1 X-4.420 Y-6.023
G1 X-4.435 Y-6.025
G1 X-4.451 Y-6.025
G1 X-4.466 Y-6.026
G1 X-4.474 Y-6.026

It moves a total of X-6, Y-6. That matches your circle pattern.

If you put all of this in a text file and name it square.gcode, what happens when you run it? Can you post a picture?

Its a miracle! It makes a square. I have no idea what was different from your code vs mine. I ran another square in sandify to see if the settings were different but that made a square too. Lots of head scratching going on but at least it works!

1 Like

Awesome. Post some glamor shots!