Any ideas how to do this?

[Sam Gardner]

I have a job to engrave a circular illustration onto wood that is exactly the width of the laser(740mm but laser height is only 460mm). Any ideas are welcome on how to engrave this in 2 halves, ie engrave the top half, move the piece up and engrave the second half. I was thinking of mounting to plywood and using left ruler as guide. If anyone has successfully done this without overlap problems let me know.
Sam

[Rodne Gold]

If its a continous graphic , it's virtually impossible to do without overlap.
If you can split it into a few parts with "white" space between em , then its easy
The big problem with the overlap is the overlap , we have done big wood items by NOT overlapping , but leaving a space of like .5mm between the 2 halves of the graphic and then manually "gouging" it in , however you then have to use something to stain the lasering and manual gouging so that everything appears even.
Depending on the graphic , we often use a vinyl cutter to make a mask and apply it to the wood and sandblast and stain , but you are limited in that its impossible to cut and weed small complex shapes or letters with vinyl.

[Brent Brod]

Maybe you could use the laser to cut two masks that overlap. Line them up slightly overlapped like you would wallpaper and cut through both layers to get them exactly matched up at the seam. Then sandblast it.

I'm not sure how you'd be able to index it accurately enough to do it in two passes on the same piece.

[James Stokes]

one way to do this would be laser the first half, move the piece where you want, place clear mylar over the piece then using low power, laser the mylar. This will show you exactly where you are.
When placement is critical I will cut 2 blocks just a hair taller than what I am lasering. Tape mylar to these blocks, then laser at low power (just enough to mark the mylar) you should then be able to slide the piece exactly where you want it. Then remove mylar. You will need to turn off your exaust when lasering the mylar.

[Kim Vellore]

Here is a thought,

Place the work piece with a shim covering the bottom half of the work piece and laser it. Now move the drawing up by 1" and move the work piece exactly 1" and flip the shim so it covers the lasered area. Now print the new moved drawing. How well this comes out will be how well you can move the work piece. You can come up with some side guides and end stop, move back by an inch laser and move up 1" to the end stop and the guides will keep it from moving in either sides.


Kim

[Kim Vellore]

Another option would be to do this.

Cover the bottom half with something that the laser does not cut through, now after you move the work piece by 1" cover the top lasered half with a thin glass and print the new file you should be able to see if there are any offsets since the top will start lasering first and you could pause the work and correct it and continue till it is dead on.

[Robert Alexander]

I did a 4 large pieces that were for a cedar chest. And the pieces were 20 x 32. My laser could only hold a piece 18 x 24. So I lasered one half and turned it around ( my laser is an Epilog so the front panel comes off when you need to do larger pieces than the table size). Anyway this is what I did. I split up the image into 2 pieces in Corel. I engraved the first piece with the first half on the image. Then in corel I took the 2nd half on the image and turned it around 180 degrees. Then I took the the panel that had on side already engraved, and on the 2nd half that was not engraved yet, right in the middle on the panel I put a thin piece of sheetmetal (26 gauge) 4inches wide and the width of the panel I was engraving and a piece of paper the same width and length which was taped to the wood on one edge. Then I put it in the laser. I went back to Corel program and highlighted only the part of the piece where the two sections of the image were conecting (this saves time because my machine goes from top to bottom). I lasered the paper on a lower setting and carefully pulled out the metal, checked to make sure everything lined up and finished the 2nd half. I had to do it a couple of times to make sure eveything lined up but it worked.

[Sam Gardner]

Well thanks to suggestions received here I can say the final piece was not too bad. The wood piece was 80cm diameter so I engraved the top half, moved the piece up, masked the joint and lasered at low power to find overlap (used masking tape as I do not have mylar) then lasered bottom half. The customer (Ministry of Finance) supplied the wood and is happy with the result.
Thanks again for all contributions
Sam

[Shaddy Dedmore]

I know it's already solved, but for another suggestion... If you have woodworking tools you can use 2 halves of a rectangle, etch, then assemble/glue then round it. Or whatever order that makes sense to you, the summary is that you make two pieces then glue it together.


Shaddy

[Rodne Gold]

Very nicely done , cant even see a hint of a join.

[Frank Corker]

Sam, fantastic job with a great design, well done