Odd inches to MM conversion on post process

[ncluthier]

Hi All,

  I am making a simple part out of 1/2" MDF (Fusion 360) that is about 3" x 4". After I post process it and load it into the GRBL program the dimensions change to MM but in an obnoxious quantity. It converts to 544 x 356mm. I must be doing something silly and missing something. Any ideas how I have messed this up?


Thanks! 

[Bruce]

So you had Fusion 360 design mode setup in inches and then you ran the post process in mm, for example GRBL(MM)?

[ncluthier]

I figured out the MM part. GRBL was set to MM (by the jog controls). What was throwing me off is it thinks the overall dimensions of the stock are 18” by 16” by 21 inches thick. I have to figure this one out. The Z axis drives straight into the stock.

[mirthmgr]

That sounds like it could be your setup in Fusion. There are a couple of different ways that Fusion lets you define the stock, either by absolute dimensions or as an offset of the model. If you entered absolute dimensions when it thought you were entering offset dimensions, I think you might end up with numbers like what you're seeing.

[ncluthier]

I redid the piece in MM and I got the almost similar results. The X and Y look good but the stock is 13mm thick in Fusion but when it shows up in GRBL program it shows it as 28mm. XY looks good it’s just the Z axis that is odd. Punching holes in my new spoil board.

[Bruce]

Can you post your g-code file for us to take a look?

[ncluthier]

May 18, 2019 4:33:25 GMT Bruce said:

Can you post your g-code file for us to take a look?

%

(Made in : Autodesk CAM Post Processor)

(G Code optimized for OpenBuilds OX CNC 1000 x 750 with GRBL V0.9j controller)



(Program Name : LPCavity5)

(1 Operation

(1 : 2D Contour1)

( Tool : Flat End Mill 4 Flutes, Diam = 6.35mm, Len = 19.049999999999997mm)

( Spindle : RPM = 15000, set router dial to 2.6)

( Machining time : 5 min 57 sec)



G90 G94

G17

G21



(Operation 1 of 1 : 2D Contour1)



G53 G0 Z-10

G0 Z10

S15000 M3

G4 P1.0

X82.1924 Y28.0863

Z15

Z4

G1 Z3.135 F762

X82.1847 Y28.0849 Z3.0357

X82.1618 Y28.0806 Z2.9388

X82.1243 Y28.0736 Z2.8467

X82.0732 Y28.064 Z2.7618

X82.0095 Y28.0521 Z2.686

X81.9351 Y28.0382 Z2.6213

X81.8516 Y28.0225 Z2.5692

X81.7611 Y28.0056 Z2.5311

X81.6658 Y27.9878 Z2.5078

X81.5682 Y27.9695 Z2.5

X80.944 Y27.8528 F355.6

G3 X80.4366 Y27.1118 I0.1168 J-0.6242

G1 X83.1846 Y12.4226 Z1.9781

G2 X65.6468 Y-2.3506 Z1.0067 I-12.9504 J-2.4226

G1 X10.6468 Y18.0784 Z-1.0421

G2 X2.0961 Y29.4438 Z-1.5667 I4.5874 J12.3505

G1 X-0.9729 Y70.3719 Z-3

X-3.1381 Y99.2478

G2 X16.3099 Y111.7982 I13.1379 J0.9851

G1 X64.5918 Y85.4573

G2 X71.2322 Y76.3144 I-6.31 J-11.5657

G1 X83.1846 Y12.4226

G2 X65.6468 Y-2.3506 I-12.9504 J-2.4226

G1 X10.6468 Y18.0784

G2 X2.0961 Y29.4438 I4.5874 J12.3505

G1 X-0.9729 Y70.3719

X-3.1381 Y99.2478 Z-4.0112

G2 X16.3099 Y111.7982 Z-4.9981 I13.1379 J0.9851

G1 X41.4961 Y98.0575 Z-6

X64.5918 Y85.4573

G2 X71.2322 Y76.3144 I-6.31 J-11.5657

G1 X83.1846 Y12.4226

G2 X65.6468 Y-2.3506 I-12.9504 J-2.4226

G1 X10.6468 Y18.0784

G2 X2.0961 Y29.4438 I4.5874 J12.3505

G1 X-0.9729 Y70.3719

X-3.1381 Y99.2478

G2 X16.3099 Y111.7982 I13.1379 J0.9851

G1 X41.4961 Y98.0575

X64.5918 Y85.4573 Z-6.9187

G2 X71.2322 Y76.3144 Z-7.3266 I-6.31 J-11.5657

G1 X80.044 Y29.2105 Z-9

X83.1846 Y12.4226

G2 X65.6468 Y-2.3506 I-12.9504 J-2.4226

G1 X10.6468 Y18.0784

G2 X2.0961 Y29.4438 I4.5874 J12.3505

G1 X-3.1381 Y99.2478

G2 X16.3099 Y111.7982 I13.1379 J0.9851

G1 X41.4961 Y98.0575

X64.5918 Y85.4573

G2 X71.2322 Y76.3144 I-6.31 J-11.5657

G1 X80.044 Y29.2105

X83.1846 Y12.4226 Z-9.5964

G2 X65.6468 Y-2.3506 Z-10.5678 I-12.9504 J-2.4226

G1 X42.5293 Y6.2361 Z-11.429

Z-11.4125

X33.7643 Y9.4917

Z-11.7555 F762

X27.2008 Y11.9296 Z-12 F355.6

X10.6468 Y18.0784

G2 X2.0961 Y29.4438 I4.5874 J12.3505

G1 X-0.1714 Y59.6839

Z-11.4125

X-0.8706 Y69.0077

Z-12 F762

X-3.1381 Y99.2478 F355.6

G2 X16.3099 Y111.7982 I13.1379 J0.9851

G1 X36.3467 Y100.8668

Z-11.4125

X44.5547 Y96.3888

Z-12 F762

X64.5918 Y85.4573 F355.6

G2 X71.2322 Y76.3144 I-6.31 J-11.5657

G1 X76.3487 Y48.9637

Z-11.4125

X78.068 Y39.7731

Z-12 F762

X83.1846 Y12.4226 F355.6

G2 X65.6468 Y-2.3506 I-12.9504 J-2.4226

G1 X42.5293 Y6.2361

Z-11.4125

X33.7643 Y9.4917

Z-12 F762

X27.2008 Y11.9296 F355.6

X10.6468 Y18.0784 Z-12.6167

G2 X3.0087 Y25.5179 Z-13 I4.5874 J12.3505

X2.0961 Y29.4438 I12.2255 J4.911

G1 X-0.1714 Y59.6839

Z-11.4125

X-0.8706 Y69.0077

Z-13 F762

X-3.1381 Y99.2478 F355.6

G2 X16.3099 Y111.7982 I13.1379 J0.9851

G1 X36.3467 Y100.8668

Z-11.4125

X44.5547 Y96.3888

Z-13 F762

X64.5918 Y85.4573 F355.6

G2 X71.2322 Y76.3144 I-6.31 J-11.5657

G1 X76.3487 Y48.9637

Z-11.4125

X78.068 Y39.7731

Z-13 F762

X83.1846 Y12.4226 F355.6

G2 X65.6468 Y-2.3506 I-12.9504 J-2.4226

G1 X42.5293 Y6.2361

Z-11.4125

X33.7643 Y9.4917

Z-13 F762

X10.6468 Y18.0784 F355.6

G2 X3.0087 Y25.5179 I4.5874 J12.3505

G3 X2.1828 Y25.8704 I-0.5892 J-0.2367

G1 X1.5936 Y25.6337

X1.5014 Y25.5967 Z-12.9922

X1.4115 Y25.5606 Z-12.9689

X1.326 Y25.5263 Z-12.9308

X1.2472 Y25.4946 Z-12.8787

X1.1769 Y25.4664 Z-12.814

X1.1169 Y25.4422 Z-12.7382

X1.0685 Y25.4228 Z-12.6533

X1.0332 Y25.4086 Z-12.5612

X1.0116 Y25.3999 Z-12.4643

X1.0043 Y25.397 Z-12.365

G0 Z15



G53 Z-10

M5

G4 P1.0

G53 X-10 Y-10

M30

%

[Derek the Admin]

May 17, 2019 22:44:30 GMT ncluthier said:

I redid the piece in MM and I got the almost similar results. The X and Y look good but the stock is 13mm thick in Fusion but when it shows up in GRBL program it shows it as 28mm. XY looks good it’s just the Z axis that is odd. Punching holes in my new spoil board.

It is going down 13mm and raising above Z 0 by 15 mm. That's why your rendering shows 28mm.

[ncluthier]

Well, after all of this I rebooted my pc and it works fine. No idea why a reboot solved the issue. The only changes I made was MM to inches in fusion and GRBL.

[Bruce]

Most likely if you design the work piece in inches you should output the CAM in inches also.