Feed rate way to fast

Problems and questions
1

Hi!

I’m using WinPC-NC as Postprocessor and created a 1mm Mill in the database with 15mm/sec feed rate. As I tried to mill a 2D drawing it is way to fast! I changed the feed rate in the tools and/or in the Operations Tab, but none of those are working. Its very fast, almost the maximum of the machine (40mm/sec I guess).

I used the “minimum G-Code” as postprocessor since WinPC-NC is not mentioned in the list.

I tested the same dxf in deskproto and it worked fine but the 2D function in deskproto is horrible so I had a glance on the Sheetcam TNG demo, but I cant get it to work :-/.

-regards

tsaG

2

In the operation set the feed rate very low and try again. Does it still feed too fast? Look at the generated G-code. You should see the feed rate. Does it look correct?

3

I tried it with 3mm/sec, no difference.

Here is the GCode from DeksProto

%%
T1 M6
M3
G00 X647.591 Y78.321 Z5.000
G01 X647.591 Y78.321 Z-3.000 F15 S16000
 X647.553 Y78.033 Z-3.000
 X647.591 Y77.746 Z-3.000
 X647.702 Y77.479 Z-3.000
 X647.879 Y77.249 Z-3.000
 X648.108 Y77.072 Z-3.000
 X648.376 Y76.962 Z-3.000
 X648.663 Y76.924 Z-3.000
 X642.484 Y0.078 Z-3.000
 X636.216 Y0.078 Z-3.000
 X635.259 Y0.128 Z-3.000
 X634.309 Y0.274 Z-3.000
 X633.371 Y0.518 Z-3.000
 X632.453 Y0.857 Z-3.000
 X631.561 Y1.289 Z-3.000
 X630.700 Y1.811 Z-3.000
 X629.876 Y2.419 Z-3.000
 X629.096 Y3.110 Z-3.000
 X628.364 Y3.878 Z-3.000
 X627.685 Y4.718 Z-3.000
 X627.064 Y5.626 Z-3.000
 X626.506 Y6.593 Z-3.000
 X604.733 Y70.951 Z-3.000
 X603.513 Y71.734 Z-3.000
 X602.454 Y72.724 Z-3.000
 X601.592 Y73.890 Z-3.000
 X600.956 Y75.193 Z-3.000
 X600.565 Y76.589 Z-3.000
 X600.433 Y78.033 Z-3.000
 X600.565 Y79.477 Z-3.000
 X600.956 Y80.874 Z-3.000
 X601.592 Y82.176 Z-3.000
 X602.454 Y83.342 Z-3.000
 X603.513 Y84.333 Z-3.000
 X604.733 Y85.116 Z-3.000
 X626.506 Y149.474 Z-3.000
 X627.064 Y150.441 Z-3.000
 X627.685 Y151.348 Z-3.000
 X628.364 Y152.189 Z-3.000
 X629.096 Y152.957 Z-3.000
 X629.876 Y153.648 Z-3.000
 X630.700 Y154.256 Z-3.000
 X631.561 Y154.778 Z-3.000
 X632.453 Y155.210 Z-3.000
 X633.371 Y155.549 Z-3.000
 X634.309 Y155.792 Z-3.000
 X635.259 Y155.939 Z-3.000
 X636.216 Y155.988 Z-3.000
 X642.484 Y155.988 Z-3.000
 X648.663 Y79.143 Z-3.000
 X648.376 Y79.105 Z-3.000
 X648.108 Y78.994 Z-3.000
 X647.879 Y78.818 Z-3.000
 X647.702 Y78.588 Z-3.000
 X647.591 Y78.321 Z-3.000
G00 X647.591 Y78.321 Z5.000
M5
M30

And here is the Sheetcam code

N0000 G21
N0010 M6 T1
N0020 G00 Z1.0000
N0030 M03
N0040 G00 X48.0434 Y77.3716
N0050 G00 Z0.5000
N0060 G01 Z-4.0000 F100 S3000
N0070 G02 X47.6326 Y78.0832 I0.1846 J0.5810 F900.0
N0080 G01 X47.7038 Y78.2552 F900
N0090 G01 X47.8000 Y78.3806
N0100 G01 X47.9254 Y78.4768
N0110 G01 X48.0714 Y78.5373
N0120 G01 X48.2933 Y78.5665
N0130 G03 X48.7264 Y79.1023 I-0.0653 J0.4957 F900.0
N0140 G01 X42.5478 Y155.9452 F900
N0150 G03 X42.0495 Y156.4052 I-0.4984 J-0.0401 F900.0
N0160 G01 X35.7817 F900
N0170 G01 X35.7561 Y156.4045
N0180 G01 X34.7991 Y156.3554
N0190 G03 X34.7484 Y156.3502 I0.0256 J-0.4993 F900.0
N0200 G01 X33.7980 Y156.2033 F900
N0210 G03 X33.7485 Y156.1930 I0.0764 J-0.4941 F900.0
N0220 G01 X32.8111 Y155.9492 F900
N0230 G01 X32.7637 Y155.9344
N0240 G01 X31.8456 Y155.5954
N0250 G01 X31.8146 Y155.5828
N0260 G03 X25.6230 Y149.6112 I5.1706 J-11.5567 F900.0
N0270 G03 X25.5981 Y149.5508 I0.4487 J-0.2206
N0280 G01 X3.8825 Y85.3614 F900
N0290 G01 X2.8096 Y84.6731
N0300 G03 X2.7380 Y84.6173 I0.2700 J-0.4208 F900.0
N0310 G01 X1.6794 Y83.6265 F900
N0320 G03 X1.6190 Y83.5586 I0.3417 J-0.3650 F900.0
N0330 G01 X0.7571 Y82.3927 F900
N0340 G01 X0.7318 Y82.3549
N0350 G03 X3.8897 Y70.5225 I7.2512 J-4.4024 F900.0
N0360 G01 X25.5981 Y6.3543 F900
N0370 G03 X25.6387 Y6.2646 I0.4736 J0.1602 F900.0
N0380 G01 X26.1972 Y5.2970 F900
N0390 G01 X26.2176 Y5.2646
N0400 G01 X26.8410 Y4.3535
N0410 G03 X35.7641 Y-0.4997 I9.3226 J6.5109 F900.0
N0420 G01 X35.7817 Y-0.5000 F900
N0430 G01 X42.0495
N0440 G03 X42.5478 Y-0.0401 I0.0000 J0.5000 F900.0
N0450 G01 X48.7264 Y76.8029 F900
N0460 G03 X48.2933 Y77.3387 I-0.4984 J0.0401 F900.0
N0470 G01 X48.0434 Y77.3716 F900
N0480 G01
N0490 G00 Z1.0000
N0500 M05
N0510 M05
N0520 M30
4

In Deskproto you have a feed rate of 15. In SheetCam it is set to 900.
Looking at the numbers I think the issue is due to a difference in units. Is WinPC-NC using mm/sec? Most controls use mm/min. 15mm/sec is 900mm/min. For the time being set SheetCam to use mm/min (in options->application options->units) but enter the values as if they were in mm/sec.

Note that the feed rate in the tool definition is just a recommendation and is used as teh default when you select that tool. The feed rate in the cut operation is the one that is actually used.

5

It works fine! I set it to mm/min and used the mm/sec value.

One more thing. Is it possible to invert the GCode for the Z-Axis?
I dont know why but our mill works fine with manual control but for the mill process we have to invert the Z-Axis since the G-code uses positive variables and our machine negative (anyhow).

I already tried to edit the function “Edit post” in the Post processor section but I dont know hat to change exactly. could you give me a hint?


regards

Patrick

6

It is unusual for Z- to be up but if you want to modify the post, look for lines like this:

post.ModalNumber (" Z", (endZ + toolOffset) * scale, “0.0000”)

Change them to:
post.ModalNumber (" Z", -(endZ + toolOffset) * scale, “0.0000”)

There will probably be around three lines that need changing, depending on the post.

By the way, if you want to fix the feed rate properly, look for lines like this:

post.ModalNumber (" F", feedRate * scale, “0.0###”)

and change them to:

post.ModalNumber (" F", feedRate * scale / 60, “0.0###”)