Acrylic with 30w Galvo

[Jiten Patel]

Hey folks,

Now I know most won't know the answer to this, but I will give it a try. I finally got around to cutting some mirrored acrylic with my galvo. The thing is, the results are, well lets say they are less than perfect. OK lets be honest, they are rubbish. The edge quality it horrific.

I run it 100% power, with 5 kHz frequency, and the slowest the machine will go is 4mm/s. It doesn't cut all the way through, there is a lot of flame (obviously as my machine is a class 4 and doesn't have the joy of air assist) and with multiple passes, I get through, but the edge is really bad. Any tips would be great.

I have tried cutting thick mount-board (1250mic) and I can get through, but with a lot of burning and charring. Most of the mount-board is cream, so any damage it blatantly obvious. It is driving me crazy, not being able to do it clean with such an expensive machine! Surely I should be able to....or am I trying too much!?

[Rodne Gold]

The problem is that the beam is steered over the marking field more or less like this /|\ and not like this ||| , whilst you might achieve enough power density at the focal point , the beam will diverge quite radically from the focal point when its steered lile this / and like this \ ie any point away from dead centre of the marking field and the huge decrease in power density (power spread over area of the spot) due to divergence will make cutting anything with any appreciable thickness a problem.

[Jiten Patel]

So clean edges are not going to be possible?

[paul mott]

Jit,

I obtained some mirrored in the UK which had a Gray coloured, slightly ribbed, backing and this turned out to be polycarbonate not acrylic. Does not cut well at all.
Just a thought.

Paul.

[Doug Griffith]

Not with thicker materials. In a nutshell, the galvo gives you greater speed but limits your applications. Cutting thicker materials being one of them.

[Jiten Patel]

even 3mm arcylic?

[David Fairfield]

Doesn't seem like the right tool for that job, for the reasons Rodne explained. But definitely make sure you have acrylic, not polycarbonate or plastic as Paul mentioned. These materials don't cut well at all in a laser, and its a pretty common mix-up.

[Michael Kowalczyk]

Aha. So finally we have an advantage over you. :D (sinister laugh in the background).

I guess you will just have to outsource it to one of us here in Houston and last time I checked Greg was really busy so I will have to check my schedule and see if I can fit you in. May have to start a 2nd shift for you but we can do it.;)

One must have many tools in there arsenal. When I was doing Kitchens Cabinets and Counter tops back in the 80's, I had 5 cordless drills and 4 different hand held routers. Each one had a purpose, though some could do multiple functions. A 3hp router is not meant to be a trim router and a right angle drill/driver is great for installing drawer slides in a narrow cabinet but not so great for installing hinges or hanging doors.

It was not as painful to buy a $40.00-$60.00 cordless drill as it would be a $150K+- galvo laser.

So you can PM me the files you need cut at your earliest convenience.

[Richard Rumancik]

Rodne, I understand what you are saying, but isn't it the job of the field lens to correct for the angularity?

Jiten, what size of field lens came with your laser? If you are trying to work past it's limit, then that won't work. But are you able to make a decent cut when you are operating right under the beam/lens? You should be able to do this. For example, can you cut a 6mm hole with good edge quality in a piece of acrylic? If that works but you can't cut a 100mm hole, then you probably are being limited by the field lens.

The other possibility is that your spot size is a bit too large to be able to cut acrylic effectively.

I'd suggest you talk to the manufacture of the galvo and see what they say. Perhaps you can get a larger field lens. But of course they don't come cheap.

[Michael Hunter]

To clear up the acrylic v polycarbonate thing -

Polycarbonate will go brown where the laser has cut it and will probably create brown or orange smoke/dust.

Acrylic will melt and may leave a white haze trail where the vapour has re-condensed onto the surface.
Acrylic wont show any browning or blackening along the cut - unless you have managed to set it on fire!

A major problem cutting acrylic on your machine is the lack of air-assist.
Molten acrylic flows down the sides of the cut, following the laser beam, and on a flat-bed is blown out of the cut by the air-assist.
If it is left in the cut, then it will solidify and join the sides together again.

[Rodne Gold]

It does to some extent correct for angularity , but not to the extent of allowing a beam like ||| over the full marking field ,even with flatfield lenses , anywhere from the centre of the lens , the beam gets oval as it diverges from the focus point , i saw this in action at the factory in china , with 80watts they were cutting 3mm acrylic , it was messy and flamed and the sides of the cut were like this / nearer the marking field edge and the bottom kerf was huge. They had to do it in 3 or 4 passes.

[Jiten Patel]

I guess that answers my question. For the application i need it for, the angled edges are not a problem at all and add to the effect trying to be achieved.

As Rodne said, the flame is massive and I can cut through in 2-3 passes, but the edge is unacceptable. I have posted a question to Trotec, see what they come back with.

Richard, I have two lenses 250mm (field size 176x176mm) and a 400mm lens (280mmx280mm). The machine/software will not allow you to cut past those fields, so that can't be the problem.

Michael, I would happily ship of my work to one of you guys, but I am based in London. Shipping charges to probably work out more than buy a nice chinese laser that Rodne bought. Looks like I will have to invest in one of those earlier than I expected to. £5000 isn't too much, so I suppose I might bite the bullet and go for it....

[Rodne Gold]

The 5k quid is nothing compared to what you can do with it to add to your business , get a strip wire bender and learn how to glue acrylic and the sky us the limit , C.R. Clarke in Blighty make some nice (albeit a little pricey) plastic working equipment , you can get a line bender from them , as well as a flame polisher.
The wedding favour market is huge and you can make a lot of em yourself apart from general laser jobbing...
There is another machine that will make you big boodle and that is the new roland digital print and cut machine.
It's this thing
http://www.rolanddga.com/products/printcut/bn/
also about 5k... check what it can do with metallics....
Your Galvo , a nice 900x600 or 1200 x 800 80w flatbed and that printer/cutter is a killer combo ......
the printer will print ont0 1mm thick stuff (like paper or cardstock) , onto self adhesive vinyls , styrene , abs , some cloths , ordinary paper , glossy paper , 0.8mm rowmark type flexibrass engraving laminates and so on ...the big thing is the metallics and pearlescent and textures you can do..

[Jiten Patel]

That Roland is genius. Metallics and pearescent ink is the Holy Grail of printing. To be able to do it yourself it great. Making short runs easy and potentially cheap. No all I need to do is find out how much refills go for and how long they last. Cheers Rodney, you are a legend.

Flatbed first, then maybe the Roland.

[Jiten Patel]

How about one of these instead of a fibre/yag. For £3500 ($5000) it might open up all sorts.

http://www.rolanddga.com/products/impactprinters/mpx90/default.asp#subNavTop

[Rodne Gold]

Its absolute junk , don't even THINK about it ............
The print/cut is about 100x more useful , we have the big brother that doesnt do metallic and its a money spinner.
I got some info , a 220ml normal cartridge is round 40 quid , a metallic is 120 quid , the metallics have opacity enough to print onto dark substrates , there are 512 metallic colours and pearlescents you can print. you can print onto heat transfer paper and transfer to t-shirts , napkins etc. You can either let it do metallics first and overprint colours after or just let it do it all in one pass.
It will do around 2sqm or 20 sq ft an hour with all the colours and metallics. Generally the cost to print in full colour with reasonable coverage and higher dpi is around 2 quid a sq meter or 20 pence a sq ft. the metallics will add a further 4-5 quid a sq meter or at worst , cost you 8 quid a sq or 80 pence a sq ft. A 3"x3" label/decal will cost at worst 5 pence. these are probably EXTREMELY conservative (read high) pricing figures , you would use metallic as a spot or accent and most likely get much more coverage.
Drool away............

[Jiten Patel]

Fair play, Scratch that from the "things to buy" list.

Dude, how much equipment do you have. Those big boys are crazy expensive....! How long have you been established just out of curiosity? Think we should have a post about everyone's background. I would love to read a mini-biography.

Rodne, you are full of temptations arent you. That is brilliant cost per sheet. Also how do you mean 512 metallics? Does it mix with the CMYK to produce coloured metallics and pearls? Printing onto dark stock is exactly what we need.

[Rodne Gold]

it mixes with the cmyk , Corel already has all the Roland metallics and pearlescents and textures as a colour palette.
BTW you can also dome the prints
You can print on your dark cardstock BUT you cannot print colours unless you have a white or metallic background , and considering this printer doesnt do white , you would have to print ONLY coloured metallics on dark..in your game , prolly not an issue.
You could print , align (not too difficult as the printer also will print crop marks) and then laser cut some stuff...
I been around a long time , this year I am 25+years in the business , bought my first cnc engraver/router in '85...
This business started out as a small jewellery shop going bankrupt , I came in and turned it around and got rid of jewellery and concentrated on engraving and trophies..and Im still here , 30 ppl in the business and a whole lot of stress..............

[Jiten Patel]

I might actually get that in soon. Sounds right up my street. And I found if for under £2k! Printing in metallics is what everyone wants, but with litho printing, the set up costs are simply not worth it for the short runs we have to do. Have you seen it in action? Will it print full bleed (to the edge) which would save me cutting cardstock down. Just pre-cut, print and laser. $$$

wow 85", not to make you feel old or anything but I was 2 at the time! Still peeing in my nappies!

Just wish I had started my own business 5 years ago. But I suppose with age comes wisdom and 5 years ago, I probably didnt have the knowledge or the patience to start up.

[Gary Noble 6363]

Just sent you a PM.

[Ian Franks]

I might actually get that in soon. Sounds right up my street. And I found if for under £2k! Printing in metallics is what everyone wants, but with litho printing, the set up costs are simply not worth it for the short runs we have to do. Have you seen it in action? Will it print full bleed (to the edge) which would save me cutting cardstock down. Just pre-cut, print and laser. $$$

wow 85", not to make you feel old or anything but I was 2 at the time! Still peeing in my nappies!

Just wish I had started my own business 5 years ago. But I suppose with age comes wisdom and 5 years ago, I probably didnt have the knowledge or the patience to start up.
Jiten
We have just done invites silver on cream (crystal) stardream. We do this litho and charge for 2 press washes as the operator is instructed to wash the rollers before inking up with silver ink to give a nice look to the print. So that is charged for. The next opportunity is then they want it silver foil, this takes longer and really costs as we send the foiling work out. But the litho side is slowing down.

But we have learnt not to get involved with the artwork, we require ready to print artwork.

[Jiten Patel]

Ian, We do all of our proofs. It's a little long sometimes with the amount of changes but our time is factored into our prices. It's all part of the experience. Weddings are driven by emotion and we try to enhance the experience, so they get the best service we can give. I think this has allowed us to grow at the rate we have.