Acrylic Haze all all around, don't know if I'm comin' up or down

[andrew zen]

I have been cutting and etching 1/4" extruded Acrylic. I can get pieces cheap so I use the extruded. I have a 75W Legend EXT. I am able to cut using 80P, 20S 5000HZ via 2 cuts.

I am getting a haze form on the top side of the acrylic when I cut. It gets everywhere and can get slightly crusty albeit thin and opaque. I try Windex to clean but it doesn't come off. I tried Goof Off and it works but causes the edges of the acrylic to crack. What is the fastest, best way to get rid of this Haze? Polish it off? With what method do you suggest?

[Chris DeGerolamo]

In short, denatured alcohol. Just a tidbit: the cracking you experienced is known as crazing.

[Gary Hair]

First thing I would do is to mask with vinyl transfer tape. This will reduce the amount of hazing you get. Next, I use Novus 2, fine scratch remover, to get whatever is left. Finally, I'll use Novus 1 to clean and shine it.

You never want to use anything with solvent to clean acrylic, it will always craze - maybe not right away, but it will always happen.

Gary

[Gary Hair]

In short, denatured alcohol. Just a tidbit: the cracking you experienced is known as crazing.

denatured alcohol will cause crazing as well, in fact, it seems to craze faster than most other chemicals.

Gary

[Rodne Gold]

Your issue is caused mainly by the 2 cut process , the first pass is problematic cos the melt and vapours are not being ejected thru the cut cos there is no cut , it just gets "splashed" everywhere.
You need to do it in one pass , and with 50+ watts this should be a snap.
You must use air assist at quite a high pressure directed downwards into the single pass cut , raise your table by about a 1/3rd of the thickness of the pex if its thicker than 6mm (1/4")

[andrew zen]

Thanks,

I lowered the power and increased speed to prevent flames from flaring up because I was getting burned smudges along the edges and I have small squares I am cutting out. I also received advice to cut this in 2 cuts.

I am using air assist as about 25 psi from a GAST air pump. It seems that my air assist is pointed straight down about 1 inch away from where the laser hits the substrate.

Luckily Tap Plastic has the Novus and I have to go find Transfer Tape, I was using clear packing tape for a few things but not for these.

I guess I should add that I'm going off the rails on a crazing train.

[Joe Pelonio]

I will always engrave, then apply transfer tape before cutting. It peels off real easily, and saves a lot of time over having to clean. When I do have to clean laser cut acrylic for any reason the stuff I use is from Costco, the Sprayway window cleaner contains no solvents.

[Lee DeRaud]

Ok, I'm sitting here scratching my head...
I've got a 25W ULS machine, cuts 1/4" extruded acrylic in one pass with no air assist: no haze, no smoke, no problem.
Am I missing something in this discussion?

[Robert Walters]

Ok, I'm sitting here scratching my head...
I've got a 25W ULS machine, cuts 1/4" extruded acrylic in one pass with no air assist: no haze, no smoke, no problem.
Am I missing something in this discussion?

What settings if I may ask?

[Gary Hair]

What settings if I may ask?

Robert,
My 30 watt machine cuts at 100% power and between 4% and 6% speed. I do use air assist and transfer tape and have virtually no cleanup. I can also cut 1/2" acrylic at 100% power and 1% speed - it takes f o r e v e r to cut, but it's pretty clean.

Gary

[Gary Hair]

I lowered the power and increased speed to prevent flames from flaring up because I was getting burned smudges along the edges and I have small squares I am cutting out. I also received advice to cut this in 2 cuts.

I think you got bad advice to cut in 2 passes, there is no need. I would start with 100% power and maybe 5% speed, air assist and transfer tape. Increase your speed until it won't cut all the way through in 1 pass. Do your testing on long lines, curves will slow down the laser and effectively reduce your speed and then you'll have a tough time cutting on longer straight lines.

The goal for me is to use 100% power and as much speed as I possibly can. Anything less than 100% for things like cutting acrylic and cermarking metal is a waste, you almost never want to use less than 100%.

By using less than 100% power you are wasting the capability of your machine. The transfer tape and air assist will eliminate the flareups and will help tremendously with cleanup.

Gary

[Joe Pelonio]

Ok, I'm sitting here scratching my head...
I've got a 25W ULS machine, cuts 1/4" extruded acrylic in one pass with no air assist: no haze, no smoke, no problem.
Am I missing something in this discussion?

My 45 watt Epilog does too, at speed 8, but then I got used to the transfer tape because I left it on for shipping after a problem with the parts getting scratched up during shipping. I never tried it without air assist simply because it's there and recommended for cutting by the manufacturer.

[Lee DeRaud]

My 45 watt Epilog does too, at speed 8, but then I got used to the transfer tape because I left it on for shipping after a problem with the parts getting scratched up during shipping.I use transfer tape (bottom side only), but that's just to keep reflections from the cutting grid off the back side.

[Lee DeRaud]

What settings if I may ask?IIRC, it's 100P and something under 1S...about the same as I use for MDF. Yes, it's very slow, but the cut quality is excellent. (The settings aren't on this computer, I'll verify them in the morning.)

EDIT: 100P, 0.7S, 1000PPI.

[Michael Hunter]

Thanks,
It seems that my air assist is pointed straight down about 1 inch away from where the laser hits the substrate..


I'm not sure if I have read this right but .... from your description quoted above and that you are getting spoilt edges, it appears that you need to sort out your air-assist.

It is important that the air-assist blows into the cut made by the laser beam, VERY close to the beam itself.
That way any molten stuff gets blown out of the cut and also topside flareups are minimised.

Edit - just noticed that you have a 24EX : the little air-assist pipe on these is easily knocked out of alignment. Just twiddle it round until it is pointing towards the focus point.

[Mike Christen]

I'm not sure if I have read this right but .... from your description quoted above and that you are getting spoilt edges, it appears that you need to sort out your air-assist.

It is important that the air-assist blows into the cut made by the laser beam, VERY close to the beam itself.
That way any molten stuff gets blown out of the cut and also topside flareups are minimised.

Edit - just noticed that you have a 24EX : the little air-assist pipe on these is easily knocked out of alignment. Just twiddle it round until it is pointing towards the focus point.
Not sure what everyone does to align the air assist on epilog but what I do is put water in a small cap or anything else that would work. Turn on red pointer and air assist and its easy to see where the air hits the water. You do need to feed the air assist directly since you can't turn it on through the control panel if the laser isn't running.

[Robert Walters]

...about the same as I use for MDF.
EDIT: 100P, 0.7S, 1000PPI.

Hey Lee,

Thanks for the acrylic settings.

How thick of MDF are you cutting?
Have you tried cutting Masonite (Tempered hardboard)?

[Lee DeRaud]

How thick of MDF are you cutting?
Have you tried cutting Masonite (Tempered hardboard)?I use both 1/8" and 1/4" MDF for various applications, like router templates or prototyping things I want to make from acrylic. Haven't tried the tempered stuff as yet.

[Martin Boekers]

I too use masking as it does save time with clean up.

I cut slots into .25 black acrylic bases to add a shaped, engraved
clear cut-out into. For whatever reasons the black takes about 5 passes
at sp 5 pwr 100 freq 5000 with 75 watts, it's 1 pass with .25 clear.

Masking works great even with 5 passes!

Marty

[Kevin Groenke]

Ditto the single pass at 100% power advise. If it's not working, there is some other problem.

Why buy masking? We just throw a piece of waste paper beneath the acrylic, the blow-back from the honeycomb sticks to the paper so the acrylic is clean-as-a-whistle, it's basically free and no peeling required.

Our 120W X-660 X2 cuts 1/4" at 100%P, 5%S, w/air assist @ ~15psi, the 60W X-660 is maybe 1.2%S.

We're currently shopping for a waterjet, that's going to be fun.

-kg

[Gary Hair]

Why buy masking? We just throw a piece of waste paper beneath the acrylic, the blow-back from the honeycomb sticks to the paper so the acrylic is clean-as-a-whistle, it's basically free and no peeling required.

I'm going to have to try that, it's a briliant idea!

Gary

[andrew zen]

My air assist has a pivot that faces down andthe tube rotates like a hand on a clock. I can not find how the air assist can be pointed towards the point where the laser hits the acrylic. The air stream hits about a 1/2" from the point where the laser hits the acrylic. Do I bend the tube?

I got this laser second hand.

There is a sign supply store here in San Jose, CA. They supply TRANSFERRITE 582U 30"x300' APPLICATION TAPE MEDIUM TACK FACTORY CUT (http://www.productsignsupplies.com/index.jsp?path=product&part=23202&ds=dept&process=search&ID=,Vinyl...Accessories,TransferRite.Application.T ape,TransferRite.Paper.Application.Tape,TransferRi te.582U.Standard.Paper.Medium.Tack.). Is that an acceptable tape?

[Lee DeRaud]

Why buy masking? We just throw a piece of waste paper beneath the acrylic, the blow-back from the honeycomb sticks to the paper so the acrylic is clean-as-a-whistle, it's basically free and no peeling required.That loud sound you just heard was my palm hitting my forehead...

[Mike Null]

Kevin

How could you keep this secret for so long?;)

I'm with Lee-----------duh!

[Michael Hunter]

Andrew

The air-assist tube on mine moves fairly easily if knocked, but does not swivel about on its own so I have not investigated how it is fixed in.

Here is a picture of how it should look -

[Martin Boekers]

Ditto the single pass at 100% power advise. If it's not working, there is some other problem.

Why buy masking? We just throw a piece of waste paper beneath the acrylic, the blow-back from the honeycomb sticks to the paper so the acrylic is clean-as-a-whistle, it's basically free and no peeling required.

Our 120W X-660 X2 cuts 1/4" at 100%P, 5%S, w/air assist @ ~15psi, the 60W X-660 is maybe 1.2%S.

We're currently shopping for a waterjet, that's going to be fun.

-kg

Mine does fine on clear acrylic, it's just the black bases that takes more passes.
I imagine it's the pigment they use on the bases. The sheet cast acrylic
black is fine. I cut letters out all the time.

The marking I get is on the surface, I've adjusted the air assist because
I think I'm getting it from the air blowing the hot vapors across the surface.
I haven't found a setting or adjustment that relieves it. Masking is cheap as
the box I cut is roughly .25x1 inch. On the bottom I cut a piece of felt as
it makes it nicer and covers the epoxy holding the inserted piece in.

Marty

[Robert Walters]

Why buy masking? We just throw a piece of waste paper beneath the acrylic, the blow-back from the honeycomb sticks to the paper so the acrylic is clean-as-a-whistle, it's basically free and no peeling required.

Geeeze, why would you do something so complicated?! ;)

[Robert Walters]

As I'm still in the process of determining if my 30W tube is on it's last leg...

I see some here have 60-120W lasers, but still have to use like 5-8 Speed for 1/4" acrylic???

That doesn't sound right to me for some reason. :confused:

Wouldn't that be a reason to have a higher power laser, so you can do things faster?

[Lee DeRaud]

I see some here have 60-120W lasers, but still have to use like 5-8 Speed for 1/4" acrylic???

That doesn't sound right to me for some reason. :confused:

Wouldn't that be a reason to have a higher power laser, so you can do things faster?That is quite a bit faster: if my 25W runs at 0.7, a 60W would be around 1.7, and a 120W would be around 3.5. (Percentage speed settings seem to run about 1.5X-2X higher for Epilogs, but I think that's just because Epilog's unrealistic max speed is lower than ULS's unrealistic max speed.)

[Robert Walters]

Lee,

Fair enough :)

I guess I just want RAMMING SPEED!!!
4" acrylic @ 120 IPM (with no tapering)

Yes, yes, I KNOW we're not in Kansas anymore...
But they promised us hovercrafts by year 2000!

[andrew zen]

Transfer Tape fixed it.

I get a little browning from underneath from the laser cutting through and heating up the honeycomb (Epilog stock). A faster speed prevented this.
Did a whole speed / power matrix.

Will investigate putting paper underneath, but I remember that paper underneath catches fire. Maybe put wet paper


For my air assist, Epilog suggests getting an air assist tube for 4" focal length and bending it to point towards the point where the laser hits the material.

Epilog's standard air assist tube points about .5" from that point which is what mine is set at.


Thanks all.

Basic Lasering 101 I know.

[Martin Boekers]

There are a few manufacturers of "pin tables" that elevate the piece off the table, you can make one too if you like, just don't have the pins spaced too far apart.

Marty

[Nick Michalares]

I liked your little "Acrylic Haze" comment. You WOULD be from the bay area, huh? Isn't that where Hendrix is from?

[Lee DeRaud]

I liked your little "Acrylic Haze" comment. You WOULD be from the bay area, huh? Isn't that where Hendrix is from?Uh, Seattle actually.:cool: