Advice needed: How to laser cut paper or card materials without leaving burnt edges

[James Tan]

Hi everyone,

i would like to seek advice on how to laser cut paper or card materials without leaving burnt edges.
I always get these brown edges and it is very obvious especially on white or lighter colors.
Is it my settings that is wrong? I have an 80W machine with 100 speed , 30 power.

My purpose is to make laser cut greeting cards, and stuffs like that.

Any advise is greatly appreciated, thanks !

[Kasey Maxwell]

wow, don't use 30 power, I cut paper all the time with my 40w at a setting of 100 speed, 8 to no more than 12 power and be sure your frequency is at 500 or so, should work just fine. being that your machine is a 80W id try a power setting of like 5 and increase it slowly as needed.

hope this helps :)

[James Tan]

Thanks Kasey ! Will give it try. I have actually never changed the frequency settings before, it came set as 20000 and i left it as it is. This might be the problem.
And my 80W tube can't fire with a power setting lower than 10, so guess i will have to try the smallest possible power.

[john banks]

What software is driving your laser? If Chinese glass tube consider "dot" mode or similar, this way with 8% power on my 100W RECI I can with a 1:2 or 1:3 mark:space ratio do vectoring over copier paper without going through it.

What type of tube is it?

Air assist nozzle size, distance from work and pressure?

[Rodne Gold]

Don't change your freq setting , Kasey has a different laser and tube to you and its not quite the same thing. On your type of laser , Its meant to be 20 000.
If you use a shorter focus lens , it will help , your lens is in all likeleyood a 50mm or 2" lens , changing to a 40mm or a 1.5" lens will give a smaller spot , the 80w will be concentrated on that small spot and the vaporisation of the paper will be much better because of the increased energy density. This will stop what is called the heat affected zone (HAZ), which is your brown edge. Think of it like this , either use a BIC lighter or a focussed flame like a small soldering torch to burn a hole in some paper , the torch will zap a neat hole with minimal char , the lighter will burn a big hole with lots of char and be slower.

[Martin Boekers]

Are you doing multiple sheets at a time? I have had issues with that and marking.

[James Tan]

Thanks for the input guys!

John: I am running Lasercut 5.3 with a reci tube, i do have air assist but i am not so sure if the pressure is considered enough? I installed a control valve to control it but now i just leave it fully open for everything, there doesn't seem to be benefits of having lower air flow.

Rodney: Mine is a 63.5mm lens on a chinese laser, and what you said made a lot of sense , smaller spot more concentrated lesser char, will switch to a smaller lens for paper , thanks!

Martin: I am just doing one sheet for now since i can't even get it right , i doubt that it will cut well for multiple sheets.

And i realize that cutting it on my honeycomb gets me flash burns on the back as well, but if i cut it on a acrylic, the paper sticks to the acrylic and it's hard to get it of without damaging the intricate designs.
Currently i am working on making my own pin table and hopefully that will solve some of my problems.

[Martin Boekers]

You may run into issues with air assist blowing the paper around, I haven't tried the "sticky mats" that may help with the flash back.
You may want to make a frame out of acrylic or wood that will hold the paper off the table while cutting.

[Rodne Gold]

IMO the 63 mm lens is the issue.. go to a 1.5" or 40mm.

[Chuck Stone]

And i realize that cutting it on my honeycomb gets me flash burns on the back as well, but if i cut it on a acrylic, the paper sticks to the acrylic and it's hard to get it of without damaging the intricate designs.

To me, that sounds like waaaaaaayyyy too much power. You want enough power to just get through the
paper and maybe slightly mark the acrylic.. but not enough to melt it so it sticks to the paper. You want
a little more power than just enough to get through the paper, because you need some margin of error.
Paper thickness and material density can vary from spot to spot

[Jiten Patel]

Hi James,

I would love to help here as we cut paper/card every day, but unfortunately we have two very difference machines. All I can advise, is every type of paper/card stock reacts differently depending on its make up. Some char worse than others and playing with settings is the only way to combat it. We use multiple passes at high speed to avoid any charring - but not sure this would work on a laser like yours.

I would be very interested to see what sort of greeting cards you are creating - you know just to be nosey!

[Richard Rumancik]

I don't think multiple passes is practicable with the x-y moving-carriage machines. Jiten, in another post you said that you use 7 passes on paper - with a conventional machine, one pass can be a job-killer and there's no job in the world that would pay for multiple passes. You can make gavo passes in seconds/pass as opposed to minutes/pass, so it works for you and a galvo machine.

We all try to make do with the machines we have, and stretch their capabilities but in some cases it just won't work.

[Jiten Patel]

Richard,

I completely get that this probably would be impracticable on an XY machine due to the time. Saying this, we know a few companies in the UK who cut card using an XY with exceptional results so it can be done. I have also used an XY to cut card with clean results - but for the life of me cannot remember the setting used. The machine was a Trotec speedy 300.

[James Tan]

Thanks Jiten, i guess the only way really is to change the lens and do lots of testing with the settings, i mainly cut acrylic and wood until recently when this job of cutting greetings card came up that i realized how difficult it is to get clean cuts on paper!
And like Richard said i probably cannot afford to run multiple passes, the pricing doesn't justify. Will post some pictures if i finally get some good results, i am very interested to see your works as well!

[Michael Kowalczyk]

Jiten,
You hit the nail on the head. If James had a Trotec, this would not be an issue:D but all kidding a side I cut 2-3 layers of paper at a time with a bottom layer as a sacrificial one to catch any flash or tics. Small parts do tend to get airborne but I have a blast gate to control CFM and a Vac table to hold most of it down but with multiple layers and a waste sheet it will vary how I approach it.

James,
Show us what you are doing or something similar because all are different, like Jiten said above, and he is the master of card cut outs.

[James Tan]

Hi Guys, i did some test cuts after changing to the smallest FL lens i have (50.8mm) but results are still not good enough. Just ordered the 1" lens hopefully that will perform better.
Attached some pictures of the test cut.
Notice the charring on the edges, very obvious on white color cards.
Another problem is that the dust/chars are dirting the cards, only gets dirtier if i try to wipe it.
Tried to cut 2 layers hoping that the top layer will protect the dust from the bottom layer, ended up both are as dirty.

234465234466234467

[David Fairfield]

Beautiful design. I think certain papers and thicknesses of papers char more than others, which is also an issue. Double layers hasn't worked for me, either. It traps smoke in between and that causes more soot stains. I wonder if adjusting the air flow from the flame damper might help. I see Epilog now offers a cone attachment that blows the air directly downwards through the cut. I guess if all else fails you can spray the white cards with white, or any other color, paint. It does seem like cheating though. :(

Dave

[Richard Rumancik]

Some references will suggest that nitrogen gas assist will reduce charring - I have not tried it myself. It will obviously be an additional expense. Also I don't think that the gas delivery system designs (air assist) with xy CO2 lasers is really optimized to make effective use of the gas. Industrial lasers have very precisely designed nose cones and the gas delievery is an important aspect of the cutting. For laser-engraver type systems air assist seems to be more of an add-on. The GCC use a pressurized cone but some others just shoot gas (air) in the general area of the cut. So if you try to use nitrogen gas you may have to look at your delivery system.

Unfortunately, the added expense of nitrogen might just tip the scales making this unfeasible.

[Glen Monaghan]

I'd think such an intricate design is already economically unfeasible on a gantry style system, except maybe in a very limited niche market or personal use where laser time is immaterial... This is exactly the sort of situation where galvo systems excel.

-Glen

[Joe Hillmann]

Are you setting the paper directly on the cutting table or do you have it suspended some how? If it is sitting directly on the bed it is very hard to prevent charing. I would suggest building some sort of jig that will hold the paper up an inch off the bed that allows air to flow through it that way the smoke can escape from the bottom as well.

[Mary Geitz]

Cutting paper is a huge part of my business. I have an Epilog 45w machine. I have found that you need to place the paper directly on the cutting table without anything underneath. The exhaust system sucks that puppy down. If you use a waste sheet underneath, the piece you're cutting will fly all over the place. My settings are 100s, 25 to 40p, and 900 to 1200 frequency. (Power and frequency settings depend on the paper I use.) I have tested a lot of different paper and now instinctively know the settings, so I don't really get a lot of flash back or charred edges.