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Jeff Chumbley
01-06-2008, 7:32 PM
I have a project from a customer. I need help in how to position the cust file on the cust provided wood. Attached is the wood with his file placed on it the way he wants it. The second file is what i need to laser into his wood. I attached the test file there are 3 others that are different but the same basic format.

Any help would be appreciated.

Joe Pelonio
01-06-2008, 7:37 PM
You have to charge for this extra time, but I'd trace it with felt pen, scan it,
then vector cut out of cardboard. Use the cardboad as a jig. Each is unique so that would have to be done over and over.

Bruce Volden
01-06-2008, 8:02 PM
Jeff,

Here's how I'd go about it. 1- place tape over ""center" ring. 2- using a plus sign (converted to curves) find the point at which you want to start. 3- do a test burn @ low power (to mark tape). 4- adjust til all is well. 5- burn your file. 6- charge accordingly. I do this often with gun stocks as well as other stuff~works good. I'm a big fan of the NUDGE tool and often use this to locate centers. When I find my centers I nudge and all is well, hope this helps.

Bruce

Chad Voller
01-06-2008, 8:52 PM
Woah, talk about lining things up. Just being off a little bit would result in the rings not lining up. I like the jig idea, but I guess I can't vision myself getting the wood squared up with the image to be lasered. I also like Bruce's idea with tape in the center to line it all up.

Now I'm just throwing an idea at ya here....

If you have any thin clear acrylic scraps laying around, couldn't you just lay that on the wood. Using just vector paths, low power and high speed. Laser on the acrylic. Now look from directly above and see if it lines up with your tree rings that you are pointing out. If it's off, move the acrylic and wood together for corrections. Laser again. Check, and repeat. When lined up; remove acrylic, re-focus laser, burn, and hopefully success.

If your laser has X, Y coordinates visible on the readout, and you know what the X, Y coordinates are for the core of the tree slice you have in your vector art, you could move your red beam to the center core position. Use that as the pivot point of your work, so you know that your center ring is staying center as you rotate your piece. (But do not run the file with this as your 0,0 of course....) Maybe I'm making it more complicated than it actually is, but it's how this newb would do it.

Scott Shepherd
01-06-2008, 9:19 PM
I'm kinda with Chad on this one. Place the wood on the table, then manually position the red dot pointer over the right areas. Write each coordinate down, go into Corel and enter the lines/circles based on those dimensions. Really easy to do and quick. Go with a piece of scrap clear acrylic over it and low power to double check, and then you should be all set. Never move the wood until it's done, which should be easy, since it looks like a heavy piece.

Entire thing should only take a few minutes.

Mike Null
01-06-2008, 11:12 PM
If you can persuade your customer to use a full acrylic shield I would mark the shield with a Speedy, scan it as Joe says and engrave the acrylic.

Jeff Chumbley
01-06-2008, 11:22 PM
Well I started out with the idea of moving the xy coords to the center of the ring and then run the job from there. I use a mask to do the testing before the burning of the wood. The file that is used is a bitmap file so it is hard to try and center the center dot where you want the laser to start firing. Maybe I need to have a vector file where I can center it more to where I want it without the "white" background making it a square.



Jeff

Darren Null
01-07-2008, 7:53 AM
The way I do stuff like this is draw an outline for simple shapes (square, circle etc), burn the outline onto plywood and then place the object in the outline.

This is a little more complex and it's an irregular shape, so I'd photograph it (getting the photo square with the centre of the object and using as much zoom as possible to eliminate lens curvature in the image), import into corel, trace (removing background) and make an outline.

That'll leave you with
The photo (adjusted to actual size)
A vector trace- don't need- delete
An outline.

So. Line up your outline with the photo and burn it onto some sacrificial material. Place your wood on the outline. Use the photo to get your artwork exactly where you need it (optionally adding brightness to the image so you can see your work more clearly), then delete the photo when you've finished. Burn.

Chad Voller
01-07-2008, 11:36 AM
I think Scott hit the nail on the head. Create the vector art from the coordinates that you get from the readings of your red beam. This guarantees, as long as you don't move your work after taking down the coords, that it will be exactly on.

Creating work from a photo, that has to be very accurate, is kind of hard. As Darren pointed out, the camera lens actually distorts the photo. I run into this kind of problem when modeling in 3D with photos taken as reference. Two views rarely line up 100% because of perspectives. You can lose alot of error by taking the picture from far away, and zooming in on the work piece. But it's not a true orthographical reference. Unless you scanned the piece, then forget what I just said.

So, if you have Corel, Illustrator, or what I use when I need to be accurate, Rhino 3D, creating this should be fairly easy now using some rulers and guides and the coordinates that you have provided yourself.

Gary Hair
01-07-2008, 2:07 PM
Scott's idea is one I have used many times and it works great.

A better way to use the acrylic to get alignment is to laser the acrylic and move the wood only until it is aligned properly - how, you say?

Cut a 1/4" piece of acrylic and mount it on 3/4" dowels that will hold it above the wood, ensure the acrylic is against the rulers forcing the upper left corner to be 0,0. Laser your image on the acrylic and then move the wood until it's aligned. Now you have an alignment tool that can't be beat!

Gary

Chad Voller
01-07-2008, 2:25 PM
Gary, that is a killer idea. You could modify that idea even more, with legs that are adjustable in height, so you could use it for future projects with varying heights. A light frame to support the acrylic when you've marked up the sheet so bad it needs to be replaced without having to build a new rig. Or each adjustable leg could attach to the acrylic with set screws so you could attach it to any shape and thickness scrap piece of acrylic you have. I will need to build me something like this...

Jeff Chumbley
01-07-2008, 3:29 PM
I use inkjet transparency film, that you can occasionally find in the bargin bin, and tape it to the rulers so it covers the item to be engraved. 100 s 25 p on the rough side and it leaves an image of your laser project. Then if off I can move the piece under it accordingly. Only problem is that this piece is about 3 inches thick.

I think I will try Chad's method with acrylic.

Thanks.

AL Ursich
01-07-2008, 4:06 PM
Even though I was an electronic guy, in my Navy days we got stuck doing Evaluations on Carbon forms to turn in. At first in the 80's we manually typed them and any errors caused the scrapping the expensive form. When computers printers became the norm in the office I came up with a novel method of doing the alignment while doing the typing in Word.

I made a document in Word and numbered left to right 0-9 and top to bottom 0-9 over and over along the top edge and left edge.

Printed a hard copy on a carbon form and just set each line of text to the block or grid coordinates. Worked great once the master was made. Did an auto load of the paper and it worked every time.

SO.... Back to the log.... I would mount the log to a square piece of wood to allow you to remove the log from the laser and be able to place it back in again at the same place up against your rulers.

I would cover the log with something you can laser at low power and still see the rings. Laser mask or something.

I would make a Corel grid pattern of dots with a 01234 etc reference along the perimeter. Mark the log with the grid without damaging the log.

Remove the log and transpose the dots grid points to a new layer in Corel at the specific rings of the log.

Place the log back in using the wood to locate it and run the job printing the new layer only and get PAID....

AL

You could even laser a 1/8 inch grid pattern on a removable film. This trick would work on many one item jobs....