Registering paper for laser cutting (already with art printed)

[Jay Selway]

Anybody have any tips for the best ways to register paper? I'm working on a job to replace die cutting with laser cutting for a series of wedding invitations. I don't have a camera registration system (epilog helix 24) and was having a hard time finding pointers on how to properly register paper for cutting.

I'll be getting the prints from a letterpress studio, then will be cutting them in a specific shape. The prints already have printers registration marks on it.

I was thinking of building a simple frame/jig out of clear acrylic with matching registration marks engraved that I could lay over the paper to match the papers registration. Tolerance doesn't need to be perfect. But at least then I can butt the acrylic into the upper corner of the bed, then shift the paper to match the registration on the acrylic.

Thanks in advance for any help you can give.

[Mark Sipes]

Do you have WYSIWYG . The TROTEC job control show you on the display monitor exactly where the laser head is located on the table. Registration is never a problem. Not sure what Epilog software can do.

[Chris J Anderson]

He has Epilog Mark, so no go...

Jay, can you simply use the centre / centre engraving option in the helix driver ?

Heres what i would try first (not saying its the best method)...

1: Use centre / centre engraving in the epilog print driver.
2: Mark the centre point of your artwork on the test paper.
3: Position the paper top left in the laser.
4: Position the red pointer on the mark and set the home position in the laser.
5: Test the cut is in the centre, and simply adjust the home position as necessary.

Hope this helps, its only how I would approach it first time, so maybe theres better / simpler ways...

cheers,
Chris

[Braden Todd]

Hi Jay,

I made my own wedding invites so I have a good idea of what you're up against.

Im not sure if you'll have this problem, but when I did mine the paper was somewhat shifted from loading and then printing in my printer so a jig didn't work out so well for me. What I ended up doing was use the red dot pointer to line up my first invite (tracing the unique outline to be cut) and when that first one was good I then spot checked the tops of the other invites with the red dot to enure all was well and then ran the actual cut for the sheet. It is somewhat time consuming to check each one but using the red dot you're guaranteed to get it right.

Good luck!

[Mayo Pardo]

If you have a scanner and the invitation will fit on the bed of it, scan it into your graphics program.
Assuming the printers registration marks are identically placed on each invitation, it would be relatively easy to set up a cut file from the scanned image. If the invitation is too large to scan (printed with multiple copies on a sheet) something as simple as masking tape on your cutting grid or laser bed could define where the corners of the paper should be. Make practice cuts on scrap paper and see how it aligns to an actual invitation.

On the other hand, if there is variation on where the registration marks are on each piece of paper, then your idea of using a clear acrylic overlay would work well. You don't necessarily have to use acrylic - if you have or can get clear acetate like they use for transparencies, that would be much less costly than acrylic.

[Jay Selway]

Thanks for the tips. I have some scrap acrylic laying around, so not a big deal to make a registration overlay.

[Richard Rumancik]

Jay, there are probably lots of ways and you will pick what you are comfortable, with but this is what I would probably do:

1. Since you want to cut through the paper "in air" (as opposed to resting on a surface) I would make a wood frame with a piece of acrylic attached to it with a few screws. I have a supply of new scrap cabinet doors which make an already-made frame. But you could make something as well from scratch. It is best if it is truly square and also best if you can screw or clamp it to the table.

2. Get the vector cutting file from the printer WITH registration marks on it (cross hairs, bullseye, or whatever).

3. From this layer create a "fixture" layer. On this layer you will scribe cross hairs centered on the registration marks, and cut through the acrylic in such a way that the paper is supported. The cutouts therefore have to be larger than the shape you are cutting in the paper. It does not have to be a contoured offset, but it could be. Cut the acrylic.

4. Using two small pieces of acetate or clear mylar, scribe a set of crosshairs. Tape these to the acrylic base so they line up with the other cross hairs. The mylar flaps must be allowed to "hinge".

5. Turn off the fixture layer and turn on vector layer. Insert the printed paper sheet under the two mylar flaps and wiggle the paper around so that both of the printed registration marks line up with the ones on the mylar flaps.

6. Tape the paper down and cut the shape.


An easy alternative I have also used if there are cross hairs on the registration marks:


1. Make acrylic fixture as before with two cross hairs for registration points.
2. Using a hand hole punch manually punch out the center of the bullseye on the printed stock, leaving some of the cross hairs. You do not have to be right on center with the punch.
3. Line up the two sets of cross-hairs by looking through the punched hole.
4. Tape down and vector cut.

[Dan Hintz]

When I had a ULS machine, I made a jig with a pin-sized hole in opposite corners that matched up with the registration marks. Push a pin through one registration mark into the hole, then swivel the page until the second hole lines up. This works well for thin paper stock as you can feel the hole underneath.

If you're using thicker stock, make the jig a two-piece... both pieces have matching holes, with the paper sandwiched in between. Line it up by eye according to the top layer. Once the pins are pushed through, remove the top layer and laser.

[Mike Audleman]

Well,

I don't have a lot of experience at this but.... what comes to mind is a jig (typical woodworker eh?). Why not make a jig that fits your bed. Have it with a top and left side rails that are spot on at 90deg that you can index the paper to using the top left corner. Then key it to your table vent slots so the jig drops into the bed exactly the same place every time. Make the rails low so the laser head can pass over them for overscanning on engrave ops but high enough so paper, cardboard and poster board can use them as a guide.

In my software I can specify a job as being relative position (meaning referencing the "Origin" as set on the laser's panel) or bed absolute (it cuts in the same place no matter where I set the origin on the laser). I would go with bed absolute. Define where the top and left edges are for your jig with no-output colors/objects and save that project as your "starter". Then any time you want to put something on paper, open the starter. Position the cut/engrave relative to the edges of the jig and size of paper you are going to run with. Load the paper in the jig so its square and flush against the sides/top of the jig. Then, send the job. Take the done paper out, replace with a fresh piece and print again. Since they will index to a given top and left rail, the paper will always be straight and positioned in the same place.

As for getting the position, I can read the laser head position (x,y) in my software (RDCam/RDWorks). You could manually position the head to the absolute corner of the jig using the red dot and pulse tests on some scrap posterboard. Then go to the software and read the (x,y). Then lock the jig objects to that corner in your "starter" project. If you made the jig right, it will always be spot on, and if you saved the settings in your "starter" project, its all loaded when you load that. It all will match each time. All thats needed is importing a new design to cut/engrave and press the go button.


Seems like a bit of time spent on making a universal jig for this sort of thing would pay off in time saved in the long haul. The same jig (if made big enough) could be used for cutting art out, making invitations, cutting boxes from posterboard, etc. I suppose it could also be used to register other projects like engraving acrylic awards or even nametags. Maybe make the jig with a replaceable bottom so it can be replaced as it takes laser damage over time.

[Dan Hintz]

Mike,

The problem with that solution is the image is rarely printed square on the page. If it was, then choosing an origin each time would solve the problem.

[Richard Rumancik]

Mike, the reason that printers put "registration marks" on a printed items is so that you have a reference for starting the next operation (such as die cutting, folding, foiling or embossing). The outer edge of the sheet is not guaranteed to be accurate in any way - in fact, it could have been rough trimmed on a guillotine cutter in a very crude manner - the printer would not care as the outer edges are not intended to be used as datums. Sure, you might luck out that 100 sheets are all the same, then all of a sudden the next batch is way different.

The point of a fixture is that you pick up on the registration marks, which are known to be in precise alignment to the rest of the graphic and hence the required second operation, in this case laser cutting. You might think we are making this more difficult than necessary, but trust me, this is the way it works.

Just a note - you talked about "jigs" - of course you meant to say fixture. Jigs guide tools and fixtures hold parts. Think "drill jig and holding fixture".

[AL Ursich]

I used a Overlay sheet to register the bottom artwork for a 2nd time in the little CNC.
I would make a overlay to work with the registration marks.

[Ross Moshinsky]

I like Dan's idea of making a jig and pins. Plop the paper down and away you go. I'd probably pre-punch the holes so that it was quicker. Otherwise I'd simply take a straight edge and an exacto knife and cut along the registration marks. That way I know all my paper is square and I can throw it in the laser and it's ready to go.

No matter what, on projects like this, it's smart to give yourself a margin of error. That way if you're slightly off, it won't matter much.

[Mike Audleman]

Mike, the reason that printers put "registration marks" on a printed items is so that you have a reference for starting the next operation (such as die cutting, folding, foiling or embossing). The outer edge of the sheet is not guaranteed to be accurate in any way - in fact, it could have been rough trimmed on a guillotine cutter in a very crude manner - the printer would not care as the outer edges are not intended to be used as datums. Sure, you might luck out that 100 sheets are all the same, then all of a sudden the next batch is way different.

The point of a fixture is that you pick up on the registration marks, which are known to be in precise alignment to the rest of the graphic and hence the required second operation, in this case laser cutting. You might think we are making this more difficult than necessary, but trust me, this is the way it works.

Just a note - you talked about "jigs" - of course you meant to say fixture. Jigs guide tools and fixtures hold parts. Think "drill jig and holding fixture".

Well, simple alteration of the concept. Elevate the upper and left rails so paper/board slides under it. Then place the material in the "fixture" (I have always called them jigs and revert to that shortly after this post :)) so that the registration marks align to the top corner and the lower left (and/or upper right) registration mark(s) align to the rail thus insuring that the piece is square with the laser gantry motions.

In any event the concept is to make something that is in exactly the same place in your bed each time and move the piece relative to that point.