Cutting Wedding Invites

[Brent Ramsay-Boyd]

Hi all

I am hoping someone can help me out with some advise.

I am trying to laser cut some wedding invites on 300gram white card stock, and I am getting a lot of charing (soot settling on the surface). Does any one have any tips that they use to reduce/eliminate marking of the card while cutting. I am using a 80W Reci Shenhui Laser.

Regards

Brent

[Dan Hintz]

Your best option is fast and powerful. You want to instantly vaporize the material at the cut site, not slowly burn through it. You'll want good fume extraction so it doesn't have a chance to stain. You also want to minimize stray beam reflections (backflash) to avoid burn spots on the back.

[Guy Hilliard]

Do not use air assist and use the lowest PPI setting that still gives an acceptable edge finish.

[Mike Null]

If you have a ppi setting experiment with reducing that until you get almost a dash line then increase gradually.

I would suggest that you use a cutting grid to raise your work above the table by 3/4 to 1 inch so that the smoke is properly exhausted and you reduce or eliminate bounce back from the table. I have some acrylic grids which I use for paper--they are actually fluorescent light grids that I've cut down. They eliminate flashback from the grid altogether. They must also be raised above the table.

I used about 15 watts of power at a 3.0 speed setting.

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[Josh Borlovan]

Low PPI and max power and speed that you can produce acceptable work with. As Mike stated, raising it off the table with a plastic flourescent light grid from Lowes is an excellent and inexpensive tactic to eliminate backflash and spotting on the backside.

[Kev Williams]

Just me, but I've found LOW power and fast speed with multiple passes works best. I get mixed results with high power when cutting paper and plastics..

[Michael Reilly]

What paper are you using? Some papers are really bad, while others are quite good. Mohawk Superfine paper is particularly prone to the sooting, as is Finch Fine Brite White 130#. I believe the bad papers have a coating that is designed to hold ink at the surface for good print reproduction, but it creates a slightly tacky surface that grabs and holds the soot. Metallic papers like Stardream and Curious Metallics are particularly good for laser cutting. Cranes Lettra is 100% cotton, commonly used for letterpress and cut quite well. We always encourage clients to send us samples before printing because we haven't identified which qualities make for a good vs. bad paper.

As others have said, using very little air assist prevents it from blowing the soot onto the sheet. A low frequency puts down fewer, hotter pulses. Get it off the grid, we prefer clean slats. If you only have only have a grid, you can go to Home Depot and get this:
http://www.homedepot.com/p/Schluter-Reno-T-9-16-in-Wide-Transition-Profile-in-Satin-Anodized-Aluminum-T9-14AE/100494686

It's anodized so it's non-reflective (for the most part) to laser. It's T-shaped so it sits up in a stable manner. You could put it on the grid, but I created a frame and put them on it so it was high enough to focus on. That gets you slats in an Epilog and slats with paper lets the material fall through so you can do sheet after sheet without vacuuming in between.

Once you have slats, if it's marking, try turning the power down, then just move the slats out of the way of the cut.

[Mike Null]

Michael

My findings differ from yours in that anodized aluminum is only temporarily non reflective. The beam will quickly remove the anodic surface and you're then dealing with bare reflective aluminum.

Air assist aids in keeping the smoke and soot off the paper by blowing it through the cut where it can be evacuated by the exhaust system.

Your comments about paper are quite interesting since my experience deals with paper and card stock from places like Office Depot.

[Michael Reilly]

Anodized does still reflect, but I think less so than other metals.

Air assist does provide that function in theory, but mostly if you have a coaxial air assist, meaning that the air and the laser beam go through a nozzle directly over the cut. Epilogs have tube on the side that points at an angle to the material. This is not nearly as effective as a coaxial version. Even with a good nozzle, some papers will perform worse with high levels of air assist than without. I always run with at least some because otherwise the lens will get residue on it.

There is definitely a lot of papers out there. I don't know what nationwide paper resellers are... Olmstead Kirk (OK Paper) might be one. Xpdex is another. The one we use is Clampitt Paper, but they are definitely regional. They are unique in that they have a sample room we can go to that has over 3,000 trays of paper samples we can pick from. http://www.clampitt.com/sample-room/

[Henri Sallinen]

Also there might be a problem with air assist. Sometimes I get small bits of paper flying around instead of dropping down when they are cut and they might end up at a place that is soon to be lasered and you would get two layers of paper instead of one. Not using air assist also allows the possible smoke to rise a bit upwards instead of blowing onto the surface of the paper. There might be some residue left on the lenses/mirrors on a long run, but I've never found them to be a problem since it would take a whole lot of cutting to even produce a small amount of residue (when cutting paper).

Probably the biggest problems with cutting paper have allready been mentioned them being the flashbacks from the grid (raise the material) and the sooting of the surface of the paper (reduce air assist+adjust power/speed).

Good luck!

[Jiten Patel]

Low power - just enough to get through and just enough speed to get a smooth cut. We use air assist on, true that you get some interfering rogue pieces messing with cut, but doesn't happen enough to worry about.

If your power and speed settings are right, you should have almost zero soot that will stain the card-stock, just brush it off with a brush. As Michael mentioned, some types of stock cut better with a cleaner cut. We use over 180 different colours and types and we can achieve a perfect cut with zero smoke or soot damage on 98% of them.

With regards to flashbacks, clean your honeycomb and you should get none. We do this day in day out and very rarely get flashback damage...usually happens when the honeycomb has a kink in it (slightly bent) so the beam reflects back.

Someone mentioned multiple passes - I personally wouldn't recommend it, time consuming and can cause smoke damage. Some of our work can take 40 minutes to cut a piece, so doing a second pass would not make commercial sense.

[Michael Reilly]

Some people on the Epilog Laser Forum asked for pictures of my home made slat idea. I didn't have pictures but did a quick drawing. It shows an Epilog tray without the grid, the light blue illustrates a spacer of some sort and the red are the T-slats. I would have liked indents to hold the slats in position as it was easy to bump them. I didn't develop it very far as my use of the Epilog EXT was temporary but I had used slats before and found them to be very useful. I included pictures of that as well. I've not had any problem letting scrap drop into the tray as long as I continue to cut the same type of material. But if I cut a bunch of paper and need to cut something like 1/2" wood, it would be necessary to clean it out because the high power, slow movement is enough to potentially ignite the scrap.

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[Brent Ramsay-Boyd]

Hi Jiten. What do you use to clean your honey comb table. I have alot of residue on mine from cutting mdf.

Also it is a big table, 1300 x 900, so is a bit of a mission to clean daily.

Regards

Brent

[Brent Ramsay-Boyd]

Hi Michael

This looks very much like the aluminium knife table that comes with the machine I have. I have been using the honeycomb, because I thought I would not get enough support from the knife table, But i will definitely give it a try.

[John Bion]

Hi Jiten. What do you use to clean your honey comb table. I have alot of residue on mine from cutting mdf.
Also it is a big table, 1300 x 900, so is a bit of a mission to clean daily.
Regards Brent

I use floor polish stripper and a pressure washer, followed with a quick wipe of paper towel on the knife blade table, or on the honeycomb table - compressed air, the Chinese honeycombs have a remarkable tendency to hold onto water. In the UK I use a product called Evans Sure Strip, diluted ‘a bit’ and applied via a garden type pressurised chemical applicator. This method deals very well with MDF and Baltic Birch residues. I use a steam cleaner to clean the main base of the cutting table, with liberal use of paper towel, machine is spotless after this (use with your noggin screwed on though regarding electronics etc).
Kind Regards, John

[brian saban]

If all else fails try painters tape as a mask, I would suggest the thickest width you can find, I believe home depot or lowes has 3" (so your not there all day.)

B

[Michael Reilly]

Brent, do the parts you're cutting require the honeycomb to keep from falling through? We did some jobs that required cutting hundreds of sheets of 1/8" mdf and our metal slats looked like this after:
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So we got some masonite and made disposable slats to use instead. Over time they developed some really cool patterns in them.
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And of course we could let the scrap fall through into the bottom tray to be shoveled out later.
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