[trung999]

I was doing a simple job using imperial units but when posting the machine barely moves, it interprets inches as mm it seems. The post processor I am using is Axiom-MADcam-Postv5_2.txt. There is a scaling function but scaling everything to 25.4 seems to move the initial distance may be correctly but then barely moves again. Do I need to modify the pp to include both a G20 command and the scaling to 25.4? In Rhino I set up the units as inches, there does not seem to be a similar setting for MadCAM.

I have the following setup: Axiom Autoroute AR8 CNC machine that uses the RichAuto A11 controller. Software are Rhino 5 latest version & and MadCAM latest version 5.0.2015.417. The RichAuto controller only understands metric but that should not be a problem since I have used Vectric Aspire software with imperial units and it posts fine. The pp for the Vectric software is AXIOM_HHC_CNC_VCPASPIRE.pp. I had done all the previous jobs using Rhino/MadCAM with metric units and the Axiom post processor I have works fine for that. I prefer to standardize on Rhino/Madcam but would like to be able to use imperial units. Please advise.

Thank you for your help.

[Louis_Cannell]

ITs all in the G code G20 and G21, the role of G20 and G21 is to tell your controller what units the numbers in the program are in. If the program starts with a G20, it will assume the program uses inches for coordinates. If it starts with G21, it will assume millimeters.

[svenakela]

ITs all in the G code G20 and G21, the role of G20 and G21 is to tell your controller what units the numbers in the program are in. If the program starts with a G20, it will assume the program uses inches for coordinates. If it starts with G21, it will assume millimeters.

And with that said, change your post processor accordingly. It's just a text file so make a copy in the same folder and edit the content to fit your need.

[trung999]

ITs all in the G code G20 and G21, the role of G20 and G21 is to tell your controller what units the numbers in the program are in. If the program starts with a G20, it will assume the program uses inches for coordinates. If it starts with G21, it will assume millimeters.

Thank you Louis. As a test I tried to execute a pocketing of a 2" hole .5" deep. I tried with a G20 only but the numbers are small and nothing moves.

(I added G20 for inches here)
N1 G20
N2 G0G17G40G80G90M5M90
N3 G00X-0.011Y0.095G54S18000M3
N4 G01Z0.145
N5 G01 Z0.128F2500
N6 G01Z0.003F50
N7 G01X-0.059Y0.080Z-0.006F50
N8 X-0.080Y0.059Z-0.011
N9 X-0.099Y0.000Z-0.022
N10 X-0.080Y-0.059Z-0.033


If I try G20 together with 25.4 scaling the numbers are big but the machine reports out of bounds and won't run the code. I looked inside the Vectric pp but not knowledgeable enough to understand how they communicate with this controller. It has no lines with G20/G21. I do know that their CAM part specifies the units separately from the CAD.

%O1
(This code is from madCAM for the Axiom)
(This is path #1)
(Added G20 here)
N1 G20
N2 G0G17G40G80G90M5M90
N3 G00X-0.287Y2.424G54S18000M3
N4 G01Z3.683
N5 G01 Z3.251F2500
N6 G01Z0.076F50
N7 G01X-1.494Y2.033Z-0.148F50
N8 X-2.033Y1.494Z-0.282
N9 X-2.517Y0.000Z-0.559
N10 X-2.033Y-1.494Z-0.836
N11 X-1.494Y-2.033Z-0.970
N12 X0.000Y-2.517Z-1.247
N13 X1.494Y-2.033Z-1.524
N14 X2.033Y-1.494

[svenakela]

Is your Rhino 3D model in imperial or metric units?

[Dan B]

Also, if the control is older it may not support G20 and G21. You might need to use G70 and G71. I ran across that scenario on an old Okuma.

Dan

[trung999]

Is your Rhino 3D model in imperial or metric units?

My model is in imperial. As Dan alluded in his post, I suspect that even though this series of Axiom machines is brand new (2015) the controller ignores G20/G21. It expects everything in metric. I thought it was strange that at the Axiom website they only suggest/support Vectric software but I guess that's because the software does the model conversion before posting in mm.

As a work around - to emulate what the Vectric software is doing, after designing in inches, I switch units in Rhino from inches to millimeters. Rhino then asks if I want the model scaled by 25.4. I answer Yes then everything works fine because now everything is in metric. That's OK until I have to modify something then the model is now in metric which is inconvenient. I was hoping the SCALE_X/Y/Z would do the same thing but it doesn't.

I just ran a test to see if in Rhino I can switch units back and forth between imperial and metric. I don't know what the effect on accuracy is but it seems to work so I can live with this work around but it would be nice to have a units setting in MadCAM separate from Rhino.

[trung999]

Also, if the control is older it may not support G20 and G21. You might need to use G70 and G71. I ran across that scenario on an old Okuma.

Dan

I think you are right that the controller does not support G20/G21. I looked up the meaning of G70/G71 they don't seem related to units so not sure how to use that. In my answer to Sven I described a work-around. That may be the only safe way right now.

[RCaffin]

. That's OK until I have to modify something then the model is now in metric which is inconvenient.

You could consider catching up with the rest of the whole world - by going metric full time.
Really, it does not hurt a bit, and is ever so easy. No more 64ths of an inch, no more bushells and furlongs...

Cheers
Roger
(I could not resist. :-) )

[trung999]

You could consider catching up with the rest of the whole world - by going metric full time.
Really, it does not hurt a bit, and is ever so easy. No more 64ths of an inch, no more bushells and furlongs...

Cheers
Roger
(I could not resist. :-) )

Hello Roger, I hear you :-) Metric is my system of choice. I did not realize there was a problem with imperial units until this project since everything I had done with Rhino/MadCAM uses metric. Unfortunately in the US a lot of things still come in imperial units. I prefer 5mm but would rather deal with 3/8" than 4.763mm. I am comfortable in either system but mid-stream conversion is a problem. Once I think in mm I don't have a good feel for the size in imperial, and vice versa. I don't know if that makes sense but for a lot of us who still use the imperial system I suspect it's not as a matter of preference.

[RCaffin]

I prefer 5mm but would rather deal with 3/8" than 4.763mm.

I used to agree about the ease-of-use thing, but then the thought occurred to me that what '5 mm' really meant was '5.000 mm'. So I changed my thinking and practices so that I always use 2 or 3 decimal places in metric regardless. The mental problem went away.
In practice, the only hassle is with hex brass bar, which seems to be still in imperial. Even so, it is rarely accurate!

The advantage is that I don't make Hubble-class mistakes with fractions any more - 3/8" => 9.525 mm, not 4.763 mm !

Cheers
Roger

[trung999]

I used to agree about the ease-of-use thing, but then the thought occurred to me that what '5 mm' really meant was '5.000 mm'. So I changed my thinking and practices so that I always use 2 or 3 decimal places in metric regardless. The mental problem went away.
In practice, the only hassle is with hex brass bar, which seems to be still in imperial. Even so, it is rarely accurate!

The advantage is that I don't make Hubble-class mistakes with fractions any more - 3/8" => 9.525 mm, not 4.763 mm !

Cheers
Roger

Right. My bad, 4.763mm is the radius to provide a 3/8" hole.