QCAD.org Forum

Posted: **Thu Jun 10, 2021 11:48 am**

Hello,

in the Cam configuration i can set the Home position from x and y. Unfortunatley, if i set the coordinates for x and y (as my millingmaschine works from 0,0 in the left upper corner), the exported Gfile doesnt calculate the coordinates from this relative point. If i move the whole drawing to absolute 0,0 (the left upper corner from the drawing) the Gfile is correct. Is there a way to get the right coordiantes in Gfile without moving the whole drawing.

thanks
Mature

Posted: **Thu Jun 10, 2021 12:14 pm**

For all support requests, please:
- Indicate the operating system you are using and the version thereof (e.g. Windows 10 32bit, Windows 8.1 64bit, Ubuntu 14.2 64bit, macOS 10.12, etc.)
- Indicate the exact version of QCAD/CAM you are using (see "Help" > "About" or "QCAD" > "About QCAD" or indicate the name of the file you have downloaded and installed)
- Attach original drawing files (DXF, DWG, ...) if appropriate
- Attach exported files (SVG, PNG, PDF, G-Code, ...) if appropriate
- Include screenshots if appropriate
- If there is an error message, indicate the exact message or include a screenshot of the message
- Indicate what post processor you are using

Note that there is a special forum for QCAD/CAM at:
viewforum.php?f=74

I will move your posts to that forum.

Posted: **Fri Jun 11, 2021 9:54 am**

Hello Andrew,
QcadCAM Professional 3.26.4.0
Postprocessor: adpted G-Code Offset[mm]
Win 10

I have to repeat my question, maybe there is a conceptual missunderstood:

In Cam-Configuration-Menu (KK) there you can set a Home Position. For my understanding this seted Home Position is the new origin for the workpiece and generated g-code. But it isnt. Attachment 1.png shows the Path in blue which started from Home Position. workpiece lower left corner absolut 0,0.

But what I need:
When moving the whole drawing (upper left corner to absolute 0,0;) then obviousley the generated g-code is as i need to have it. See attachment 2.png.

My question: Is there a way to set the origin of the workpiece for Cam output?

thanks
Martin

Posted: **Fri Jun 11, 2021 1:02 pm**

The home position is simply an absolute coordinate that can be used as starting point, tool changing point, etc.

Changing the home coordinate does not affect other coordinates in any way or change the coordinate system in any way.

To flip the Y axis, you could re-register all Y variables in the constructor of your post processor. For example:

Code: Select all

function GCodeOffsetMM(documentInterface, camDocumentInterface) {
    GCodeMM.call(this, documentInterface, camDocumentInterface);

    this.outputOffsetPath = true;

    // option for negated values:
    var negated = { factor: -1.0 };

    // re-register Y variables with negated option:
    this.registerVariable("yHomePosition",       "YH",                   true,  "Y", "DEFAULT", negated);
    this.registerVariable("yFirstPosition",      "YF",                   true,  "Y", "DEFAULT", negated);
    this.registerVariable("yStartPosition",      "Y1",                   true,  "Y", "DEFAULT", negated);
    this.registerVariable("yPosition",           "Y",                    false, "Y", "DEFAULT", negated);
    this.registerVariable("yRelPosition",        "YR",                   true,  "Y", "DEFAULT", negated);
    this.registerVariable("jArcCenterInc",       "J",                    true,  "J", "DEFAULT", negated);
    this.registerVariable("jArcCenterAbs",       "JA",                   true,  "J", "DEFAULT", negated);
    this.registerVariable("yMin",                "Y_MIN",                true,  "",  "DEFAULT", negated);
    this.registerVariable("yMax",                "Y_MAX",                true,  "",  "DEFAULT", negated);
}

Posted: **Fri Jun 11, 2021 4:48 pm**

Hello Andrew,

-1 is useless its a mirror mapping, thats not the same as an offset to y.
lg
Matura

Posted: **Sat Jun 12, 2021 9:42 am**

Sprung wrote: ↑
Fri Jun 11, 2021 4:48 pm
-1 is useless its a mirror mapping, thats not the same as an offset to y.

Correct.

This issue resurfaces in several topics.
As far as I have followed the QCAM topics, one has to move the drawing as per your solution.
The drawing origin is the absolute origin for your G-code.
A CAM should supply in a manner to set a relative origin, a UCS for that matter.

... Or one has to zero the machine setup like it is drawn.

The home position
The parking position
The pausing position
The tool change position
The drawing origin
The relative G-code origin
The zeroing position

All are independent things.

It is not correct to state that the homing position should always be equal to the G-code origin.
Nor the drawing origin, nor the zeroing position.
But, off course, they all can be.

Taking my setup as an example, a moving bed engraver with a fixed gantry:
The home position is Left-Far-High. A position only needed once at start-up for mechanical synchronization.
My parking position is 5mm away from that so my initial homing at very low & safe speeds doesn't take forever.

Also, I can traverse at very high speeds to my park position without any danger hitting the mechanical ends.
My driver only allows the high speeds after proper homing. My mechanical ends are fractions away from homing.

I always draw my designs in the first quadrant. All positions are then positive in X & Y what is rather handy for a human.

I position my stock or work piece on the moving bed where I want it

or where it is best suited.

Then I zero my setup Left-Near on my work piece. Only then I zero in Z.
The pausing position is chosen so that A) the tool retracts and B) the piece comes to me so that I can examine it up close under manification.

There are some exceptions like with flat round pieces, then zeroing on the center with a machine macro is more handy.
On top the piece may even be positioned slanted and then I slant/shift the X/Y working plane accordingly.

Bottom line: Nothing in my drawing reflects on how it sits on my moving bed engraver.

Regards,
CVH

Posted: **Sat Jun 12, 2021 9:04 pm**

Hello CVH,
thanks for your explanations. Despite iam wondering there is no "set origin" in QCAD/CAM, for a computer program it should not be a big thing to calculate the coordinates from any starting point.
regards
Matura

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