What do you do when your laser cuts out of square?

[John Blazy]

I finally discovered one reason why not to buy Chinese. Although, I still like its value. My bed was out of focus in the front, coupled with some warpage in the 6mm BB plywood, and it did not cut all the way through on first pass, but didnt know it til I took the panel out.

Rather than set it back in and recut the file, I set it in upside down and cut a mirrored file over the panel, and indexed the panel exactly over the new file. On the front and back straight line that did cut all the way through, I parralleled the beam exactly to these two lines, then when test firing the laser, I lined it up on the start point. Couldnt figured out why it would not cut exactly on the first cutout, so I indexed it to its start cuts - lined up well, then 20 minutes later and other fussing gone by and looked at the y axis cut, and if the laser was cutting perfectly square, all four outside rectangular lines should have lined up - maybe not 100% perfect, but you would think it would be pretty close. 3/16" deviation in 35" in the flipped panel offset, meaning the laser is cutting 3/32" out of square (top of parallogram shifts 3/32" to the right).

Anyone know of an adjustment I can make before I call Rabbit? The shift isn't that bad, but it bums me out.

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[Kev Williams]

That problem's not confined to Chinese lasers. I've had to realign both my old ULS and Gravo machines. Getting the gantry square in all directions including mirrored-Z is pretty tough to do...

You have the 2 Y axis rails, which must be bolted to the machine parallel and square to each other and to the machine, and the X rail which must be squared to the Y rails...

This is the ideal situation (easy in Corel, lol)
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--but if the X axis is squared to the table, but the Y rails are canted slightly, then the Y axis will have runout.
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--and, if the Y rails are straight, but the X rail isn't aligned square to the Y travel, then the X axis will have runout--
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---which is the problem I believe you have. And this is very common. All it takes is one loose screw ANYWHERE in the Y axis drive train for the X axis to move on one side or the other. putting it out of square to the Y axis.

But it's an easy adjustment, as long as the Y axis runout is near zero. Just pick one of the Y drive rod set screws- let's say the right drive rod- and loosen it, until the rod will turn freely within the sleeve. If you had 3/16" of mirrored runout, that means your actual runout is half that, or 3/32 , about .093" (or 2.4mm). You need to adjust the right end of the X gantry up or down that amount to compensate, tighten the set screw(s), then test...

Find something you can cut thru that's long enough and has a nice straight edge. Cut a line thru it, flip it end over end and cut from the other side. Determine the runout direction, and adjust. Keep testing and adjusting until both lines cut dead on---

Then hope the Y axis does the same... ;)

[John Blazy]

Thanks a ton Kev!!!

THat is an elegantly simple and perfect solution. Ill have to send you some Dichrolam for your help.