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Old 09-09-2018, 11:10 AM
JGIBBS JGIBBS is offline
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Default inaccurate laser

I have a Panther PT-408. It has been used as a “hobby” machine so far. I am still learning the machine and design software. I have recently noticed my laser is very inaccurate so this morning I decided to check it out.

I started by drawing a dot on my table, then turned the laser on, positioned the crosshair on the dot with the tool nearly touching the table. I then raised the router roughly 5 ”. By doing this I noticed the laser is now about 1/16” off the dot towards X-. This tells me the Z axis assembly is not going strait up, but running at an angle in the X direction.

The next thing I tried. With the tool close to the table, I repositioned the laser crosshair on the dot. Then I hit the Laser X0 Y0 button. My tool moved to position and turned the laser off normally. The center of my tool is now close in Y but roughly 1/8” off towards X-.

Looking at the “command” box in WINcnc I see the macro, L91X-3.450Y-1.280. Then the Gcode to reset X&Y 0s.


At this point my questions are, should I be concerned with the Z axis moving at an angle, and how do I edit the L91 macro to move the correct distances? Never mind the macro editing question. I figured it out.

Last edited by JGIBBS; 09-09-2018 at 11:43 AM.
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Old 09-09-2018, 12:00 PM
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Gary Campbell Gary Campbell is offline
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Surely getting the laser beam more orthogonal to the motion cannot hurt.

That said, the laser is calibrated and designed to work at only one height. As long as it is operated at the height is calibrated at it should be accurate to within half the beams width at that height.
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Old 09-09-2018, 01:39 PM
JGIBBS JGIBBS is offline
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Gary,
Thanks for the input. I think the post title is misleading. I don't think the laser itself is inaccurate.

I was trying to figure out why the center of my tool didn't go to the same XY position on the table marked by the laser.

By editing the positions in the Laser X0 Y0 macro, I was able to help that issue.

The problem I am still seeing is, I turn the laser on. Z at .05 then move only Z up to 6.25. I can watch the crosshair move .05 in a X+ to
X- direction.

To me this, (along with my digital angle meter) show the linear rails for my Z axis are not running perpendicular to the rails for my X axis. Doing the math, it is off by less than half a degree. Is this considered within spec for this machine?
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Old 09-09-2018, 01:52 PM
CosmosK CosmosK is offline
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Your laser it probably not parallel to your Z axis. You'd need to shim the laser mount in two directions to get it dialed in which would take some time and iterating. I would think your Z axis is not that far off, but I wouldn't say that based on what the laser is telling you. A 12" speed square will tell you if there is a major issue with your z axis. I think it's just the laser mount.

EditL now seeing you have digital angle meter. Not sure how accurate that is. You should be way out of tram if that's the case which is easy to check.
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Last edited by CosmosK; 09-09-2018 at 01:54 PM.
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Old 09-09-2018, 02:32 PM
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Gary Campbell Gary Campbell is offline
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Cosmos is spot on. Laser is not orthogonal to the Z travel.

Most of the "Laser_On.mac" files lift the head to the machine Z zero (G53 Z0) and are calibrated there. They should be both focused at that height and calibrated (the relative move distances) at that height. Does yours have that line in it? Has it been changed?

There is no reliability, consistency or accuracy assumed for any other location, especially if moved vertically. You can if you wish waller out (N. Georgia technical term) the holes and shim, if needed the laser mount bracket to get it orthogonal in both the X and Y planes.
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Old 09-09-2018, 02:37 PM
JGIBBS JGIBBS is offline
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Thanks Cosmos,

It's funny how one can overlook the obvious some times. I will have to bring a good solid square and indicator from work tomorrow.
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Old 09-09-2018, 02:42 PM
JGIBBS JGIBBS is offline
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Gary,
I considered remaking the laser mount from aluminum. Your thoughts?
and Yes it moves to machine Z zero when laser is turned on.

Last edited by JGIBBS; 09-09-2018 at 02:46 PM.
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Old 09-09-2018, 03:30 PM
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Gary Campbell Gary Campbell is offline
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2 thoughts...

I believe the laser mount is made from an insulating material for a reason

Is there a reason that you cant just focus and calibrate it at the G53 Z and simply use it?
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