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For guys with digital cutters, a question.

letterworks

Premium Subscriber
Skip to the end for the question. Here is the setup:

I'm currently workng on one of my least favorite jobs. It involves laser cutting out some acrylic with a printed vinyl face. However, it's not a simple outline, its a "messy" circle or set of sort of round shapes with a lot of intersections. I need to cut out all the bits that don't have a color printed on them (I will follow up with a photo).

Chinese laser using Lightburn software.

For jobs like this, I like to have registration marks (although I have learned how to do without if I have to!).....but on this particular job the client has nicely spaced the reg. marks inside the cut. And, regardless, the laser always wants to work from the extents not the center of the mark. So, here is my typical process:

1) Move the laser into the center of the table a bit.
2) Line up the center of the upper left reg. mark with the dot of the laser, just manually pulsing it.
3) Then, on screen I draw a box on from the center of the mark to past where the extents are so my corner box is the extent position now.
4)Then I move the laser away from the mark on the machine by the size of the box (1.5" x-y+ in this case)
5) On screen, I make an offset contour .25" larger than the reg. marks on screen. This is so I don't laser the crap out of the physical sheet and can't see where the original marks were.
6) I cut one or two or all four of those offset contours out and try and pivot the physical piece to line up the marks with the cuts. I cut on masking tape so I can pen mark the centers of my cut with the mark on the physical piece underneath.
7) Once I have at least two of the marks lined up, then I look at the other marks and start making notes:
i) Do I have to adjust the size of the drawing to match up with the physical part (ie machine differences, could be customer's machine or mine)
ii) Do I have to skew the drawing to match up with the physical part.
8) Since the answer was "yes" to step 7, I export the drawing, work on it in corel and send it back to lightburn.
9) Test again with the reg. offset contour cuts. Now 3 are good, 4th is maybe good enough and it would start to get beyond scale and skew work to correct.
10) Offset a hollow section, which is like the center of an O in this case. Test cut this offset, measure the gap from the cut line to the graphic.

After 10 steps, I deem it ok to cut. I figure out what speed the laser is good for one this piece, test some of those cuts, and off I go.....this might be a lesser issue on better machines.

So, my question is, for those machines with cameras and software for automatic cutting from registration marks....does the software account for possible size variation and possible skew? I would have to think it does if it's any good but I have no idea. I also don't know any camera system for lasers but maybe trotec does something?

If camera systems do handle that sort of thing, I might try to find someone that would cut for others and then I can pass on these jobs. I charge for the time but it's a pita.
 

letterworks

Premium Subscriber
Here are the photos. The overall view. The reg. marks are under the green tape

ec036fd1a950b653160dc530d2303142.jpg


This photo is the final test cut for alignment. I am marking the paper .25" inside of the actual cut and testing for a uniform gap all around.

2da93099ed162b9d1cb2b92393e8f56e.jpg


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letterworks

Premium Subscriber
This photo didn't work on the last try. A close up of the registration alignment work.

5b30ac37d65ea6bb70487bd511e61826.jpg


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dale911

President
My Kongsberg cutter has camera registration. All I have to have is a minimum of 2-1/4” dots to do a location registration. If I set the software to compensation, I need more dots most likely ( I usually have several throughout the art or at least along all 4 sides of the art)

I can put the the material anywhere o want on the table with any skew and even if the material is stretched one way or the other, once the camera reads Al of the marks, it will compensate as well as possible to deal with the skews. The more marks the better but it works perfectly. I used to have a flatbed cutter that only used corner marks and it was mostly accurate but everything had to be placed on the table square or it would miss the mark and we would have to start over. Took forever. I also built a Cnc router previously and had to manually register all of my work and it was extremely time consuming. For a piece like the one you are doing now, I would add some registration dots to the art and on my blank piece, I would cut the dots first. Then I would turn on camera registration and start my cutting process. This way, if there is an issue or I want to run things on the piece at different times or tweak things or whatever, I could do that and not worry about losing registration.


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letterworks

Premium Subscriber
My Kongsberg cutter has camera registration. All I have to have is a minimum of 2-1/4” dots to do a location registration. If I set the software to compensation, I need more dots most likely ( I usually have several throughout the art or at least along all 4 sides of the art)

I can put the the material anywhere o want on the table with any skew and even if the material is stretched one way or the other, once the camera reads Al of the marks, it will compensate as well as possible to deal with the skews. The more marks the better but it works perfectly. I used to have a flatbed cutter that only used corner marks and it was mostly accurate but everything had to be placed on the table square or it would miss the mark and we would have to start over. Took forever. I also built a Cnc router previously and had to manually register all of my work and it was extremely time consuming. For a piece like the one you are doing now, I would add some registration dots to the art and on my blank piece, I would cut the dots first. Then I would turn on camera registration and start my cutting process. This way, if there is an issue or I want to run things on the piece at different times or tweak things or whatever, I could do that and not worry about losing registration.


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Good to know.

I don't know of anyone local with that type of equipment, well at all, but no one that would cut for other shops on their material. Most guys that have the machines seem to use them in house and then you can figure out any machine differences more easily. Good to know that they are as versatile as one would hope.....might need to find a shop with one!
 

letterworks

Premium Subscriber
I don't have the current version. I adopted lightburn early and since it was already better than the Chinese software, I left it as is.

I like it when developers give you good reasons to update!

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henryz

New Member
Sorry, I skipped to the end. Do you apply vinyl to the substrate or print direct. If I cut the shape on router I would apply the vinyl on a light box to center the digital image. If you can't cut accurately after direct printed on material, print it on the table then align the cutout on it to print?
 

letterworks

Premium Subscriber
Sorry, I skipped to the end. Do you apply vinyl to the substrate or print direct. If I cut the shape on router I would apply the vinyl on a light box to center the digital image. If you can't cut accurately after direct printed on material, print it on the table then align the cutout on it to print?
I just get the mounted print dropped off by the sign shop (I'm an acrylic shop, currently looking at getting more into dimensional letters hence the screen name here). Sometimes I supply the piece it's mounted on, but never router cut first.

I get what you are saying, but in this case even off by 1/16" would be a problem.

LOL, I'm also just realizing I can't post the final part photo as customer was waiting by the laser to pick it up.

Greg





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Gene@mpls

New Member
I would definitely upgrade your Lightburn, they are improving it constantly. You should really not cut PVC vinyl [I know it is really thin] but the chlorine gas is poisonous and very hard on the machine parts. We have a member who scrapped his machine after cutting a bunch of vinyl records- it was a ugly mess.
 

letterworks

Premium Subscriber
I would definitely upgrade your Lightburn, they are improving it constantly. You should really not cut PVC vinyl [I know it is really thin] but the chlorine gas is poisonous and very hard on the machine parts. We have a member who scrapped his machine after cutting a bunch of vinyl records- it was a ugly mess.

The general consensus I have read (via sawmill creek) is that sign vinyl is not going to be the thing that does a chinese router in. Sintra or vinyl records, yes that can. kill it but I have to say it's the fumes effects on people I'd be more concerned about as the machines are cheap enough (and could be protected somewhat) they might be worth the wear and tear for the right type of work.
 

letterworks

Premium Subscriber
Ok, I think I'm following, but the biggest issue here appears to be you are not supplying prints, so that much is out of your control.
Could you just have them replace the reg marks with something like cross hairs to line up a drill nicely, drill the holes out on the piece, then cut a jig from some scrap acrylic, add dowels to the holes corresponding to the reg marks, drop the jig in the machine, drop the acrylic with the holes over the dowels, then cut?
That's how I handle router jobs and I suppose I could do that more with the laser (I would just line up the holes however unless it was a lot of pieces), but the lack of hold down leads me not to most of the time. The scale issues would remain on this particular job as the tolerances were so tight.
 

zspace

Premium Subscriber
One way we’ve handled it is by adding a non-printing box the size of the substrate. Then put an oversized sheet of styrene on the laser and cut the box and use the matrix left on the laser as a registration template.
 

letterworks

Premium Subscriber
I didn't think you'd need much in the way of hold down on a laser? Not much experience with them aside from engraving. I'm also not sure how a jig would impact hold down, in my experience making jigs for stuff on the router, it's always larger than the piece and gives me more opportunities to secure it either mechanically or with a vacuum? Honest question.

I don't think that would work here because the print applied to the acrylic is not necessarily placed perfectly center or anything, hence the need to register it otherwise.

I think ideally you'd have someone print onto the acrylic with a flatbed printer instead of print and stick. Less/no deformation, plus I think they can register their prints to the sheet.
You are correct that the hold down issues are minimal. I was just saying that can lead to a different approach on the laser versus router, and perhaps not a better approach.

Greg


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