Work area offset for Laser mounted to CNC

I have a laser mounted to the spindle bracket of my CNC. The machine is set up in Lightburn (bed dimensions etc.) however, when I home (front left), my laser is overhanging my actual start position (bed) by some 100mm.

Is there some way I can set it up so that my workspace is xmm back from Y home?

I thought about extending my workspace dimensions in Lightburn to account for it and changing from absolute chords to start from the current position (after jogging back), but it would mean I have a ā€˜floatingā€™ front edge and I will have to measure from the back > forward all the time to be sure Iā€™m within what I can fit (front to back) when laying jobs out.

Iā€™m relatively new to this, so please accept my apologies if this is a newby question with a simple answer, but I have tried and looked extensively and canā€™t find anything.

I really appreciate any pointers/guidance on this.

Cheers

James

before we start, how GRBL is your GRBL? My experience does not include the Black Box controllers, so keep that in mind.

You have not provided a sketch or image showing the problem. Not sure why it can Home and it overhangs your work area.

Have you researched the G54 Work Offset command? This might give what you want. Just remember it is modal, meaninf it remains with power down.

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Thanks for chiming in and trying :slight_smile:

Iā€™ve added a graphic of my machine when homed with a laser module mounted (my actual module is larger). Hopefully, this shows the ā€˜overhangā€™.

Yes, I looked at G54> etc. as I use them currently for coordinates in open control for templates/jgs when CNCing but * below.

I currently use the ā€˜saved position(s)ā€™ in lightburn to jog the laser back to line the laser head up with the front of the machine physical bed but **

*** Both of these solutions still mean in lightburn, after homing, I am starting from a point which is back from the base line of my digital bed.

I get around this by having the laser switched on, homed and jogged thus using the red dot as a reference point for importing jobs to the workspace BUT, I plan most of my jobs at home on a different PC so I donā€™t have that available.

Basically what I want is to home the machine and jog xx mm along Y to preset ā€œoffsetā€ which when viewed in lightburn - the laser head is the bottom left ( 0 - 0) of the representative bed.

Thanks

James

Machine looks rock solid. Laser module overhang looks like a diving board. Why not mount the laser on the same axis as the spindle motor? Looks like you created a mechanical problem and are trying to compensate for it with the software.

Any vertical springiness in the mount will translate to Yaxis wobble.

If I understand this correctly, the laser head is chunky enough that the Y axis home position puts the focused beam 100 mm farther away from the edge of the machine platform than youā€™d like and thereā€™s no mechanical way of moving the laser head closer to the home position.

The LightBurn workspace coordinate system should represent the entire ā€œreachableā€ extent of the platform, so that any shapes you put on the workspace can be cut / engraved (paying attention to overscan) without hitting the edges of the platform. Any part of the platform the machine cannot reach is irrelevant to LightBurn, because it cannot do anything there.

Rather than doing that, use Absolute Coordinate mode with the home position at (0,0), so the LightBurn workspace exactly matches the machine platform.

When you import a design, you can position it anywhere on the LightBurn workspace and thatā€™s where the laser will cut / engrave it. You could put the design at a known coordinate, put a fixture on the platform with material in the fixture, and hit the right spot every time on every piece without further thought.

If you must accurately position the material under the design, use Position laser (a.k.a. Click-to-move) to put the laser at a known part of the design, then align the material to suit.

if youā€™re not cutting the perimeter, add a square / polygon / circle on a Tool Layer around your design to match the material, then click to put the laser on the perimeter and shuffle the material.

Or you can use `Print and Cutā€™ to align the design to the material.

Basically, use the coordinate system to your advantage, rather than fighting it.

Also, as @MikeyH points out, if that chunky head isnā€™t rock solid on the gantry, it will wobble and the laser beam will trace all those wobbles on the material!

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I use this one a lot and almost always work in Absolute Coordinates. The exception would be with the rotary.

Another similar thing I do is position the laser centered over the part. Then I click on the Show Last Position button to make the little red ā€œ+ā€ appear. Next, I click in the center of the selected drawing and move that over the ā€œ+ā€ marker. Finally, I Frame to see if I need to resize the drawing. Works every time.