Re: [CAD_CAM_EDM_DRO] Metric measurements.

Hello Keith,

Some Gcode executing software uses G70 and G71 and others use G20 and
G21 to indicate that the program length units are inches or millimeters.
Check your owners manual or just try them and see which ones do not give
error messages.

At the top of your Gcode file, or at least before any length units can
be misinterpreted, insert G20 or G70 to indicate that the length units
are to be performed as inches. Use G21 or G71 to indicate that the
length units are millimeters.

You can also change units within the program. You might millimeters for
most of your program but have some subroutine that uses inches. Just
make sure to insert G20, G21, G70 or G71 to tell the Gcode interpreter
that the length units have changed.

In the absence of these commands the Gcode interpreter will assume that
the length units are whatever your defaults are set for or whatever was
last used on a job. it appears that your default is inches.

I ALWAYS use one of these codes near the start of my program since I
might use either on any job and can never be sure how my last job left
off.

Tom Hubin
thubin@...

***************************

kbucklitch wrote:

>
> Hi folks
>
> This is my first posting to the group, in the hope that someone will
> be able to assist me.
>
> I create my CAD drawings with TurboCAD. For several years, I have
> produced my drawings using metric (mm) measurements. Before I
> started experimenting with CNC, if I printed the drawing full size,
> then it was printed almost exactly the size of the item (within the
> accuracy of the printer).
>
> To use the drawing to create a toolpath for the CNC cutter, I export
> the drawing initially as a .dxf file. I have then converted the
> file to G-code using two programs - KCam or Simsoft Mach 2. Both
> of these will produce a G-Code script. I then use the software to
> drive the CNC controller. At present, because I am driving my CNC
> control with KCam on an old laptop under Windows 98 (Mach 2 requires
> WinXP.) However, I have found a problem. The CNC driver seems to
> work in imperial units (inches). Hence, a component that should be
> say 20mm long, becomes 20 inches long. This is a little difficult
> on a milling machine which only has around 12" of travel.
>
> In the KCAm Setup/Table Setup menu, it asks if you want (are using?)
> imperial or metric measurements. However, choosing metric in this
> dialogue box does not appear to make any difference to the finished
> size of the article.
>
> Does anyone with experience of these programs - Mach 2 or KCam know
> how I can set them up so as to convert metric .dxf files to metric
> machine codes?
>
> Thanks
>
> Keith
>
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