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View Full Version : Acrylic settings for VLS 3.60?



John Tolman
08-25-2012, 2:05 PM
For the several months that I've had this VLS 3.60 (with air assist and 2.0 lens), when I cut acrylic there are distinct lines running vertical (or normal to the cut edge). They're spaced very close together, less than a millimeter apart.

I've played with dpi, power and speed, with little luck, and I'm looking to get some settings hints on how to reduce this effect if that's possible. I realize it may not be exactly the same for my machine as another, but just hoping to get some guidance. I'm usually cutting 1/8" but sometimes 1/4".

I just remember seeing the perfectly glass smooth acrylic shapes at the vendor's shop. They had said that specific example was cut on a different type of laser (can't remember the type), but that I should be able to get the same results from the VLS.

My other question was in regards to the slight angle on the acrylic (or any other material for that matter), is this minimized by focusing the laser to the top surface of the material. Would it be greatly reduced when cutting thicker (1/4-1/2") acrylic if I were to be using the high density focusing lens kit, as opposed to the 2.0. It seems to me this reduces the cone angle of the laser, just not sure how significant it is for cutting (I was told by VLS the HDFO isn't intended for cutting...).

Thanks for any light anyone can shed on this for me, it's not my main business so I haven't been able to devote a lot of time to testing out settings, but I'd like to be able to get a cleaner edge so I can make really professional looking signage.

-John

Scott Shepherd
08-25-2012, 2:55 PM
Hi John, no, the HDFO would make the angle worse, not better. To make it better, set the focus down into the work, not on top of the acrylic. Try manually focusing and then going .030"-.060" deeper into the work, so the focus is below the surface. That'll help that angle issue.

For the striations you are seeing, that's normal. If someone told you that you should be able to get that polished look right out of the laser, they weren't honest with you. I know of one machine that will do it and it takes their $5000 software package to make it happen.

You can help somewhat by sending the imagine density over at "7" when you send the job. On the PPI, put that at 1000PPI. What you end up with by doing all of that is going to be about the best you can get.

Hope that helps.

Michael Hunter
08-25-2012, 5:21 PM
A friend of mine gets near perfect polished edges - on her TROTEC !

Ordinary mortals have to put up with striations though.

John Tolman
08-25-2012, 10:10 PM
Hi John, no, the HDFO would make the angle worse, not better. To make it better, set the focus down into the work, not on top of the acrylic. Try manually focusing and then going .030"-.060" deeper into the work, so the focus is below the surface. That'll help that angle issue.

For the striations you are seeing, that's normal. If someone told you that you should be able to get that polished look right out of the laser, they weren't honest with you. I know of one machine that will do it and it takes their $5000 software package to make it happen.

You can help somewhat by sending the imagine density over at "7" when you send the job. On the PPI, put that at 1000PPI. What you end up with by doing all of that is going to be about the best you can get.

Hope that helps.

Oh right, now that you mention it, that makes sense that it'd be worse. I will give it a shot focusing it into the work.

Well, at least they didn't tell me that before I bought the laser, and it wouldn't have made much of a difference since I have no commercial use for cutting acrylic (at least not any application that needs to look pretty).

Beyond 1000 ppi, I suppose it's ideal to run it slower at lower power than higher power and higher speed (assuming time is no issue for me). Then again, I seem to remember reading or being told this is ideal for the life of the laser in general, so there's my answer.

I wish I could remember what the laser system they cut that sample on. It wasn't brand name and software that gave it that ability, it was the type of laser, as it was actually a Chinese system and presumably nothing fancy. Maybe it was a YAG laser, although for some reason I have it in my head those were only used for high power applications such as cutting metal.

Anyway, thanks for the info.

John Tolman
08-25-2012, 10:12 PM
A friend of mine gets near perfect polished edges - on her TROTEC !

Ordinary mortals have to put up with striations though.

Good to know. I wasn't willing to spend that much on a Trotec so I'm happy dealing with the imperfections.

Richard Rumancik
08-25-2012, 10:36 PM
John, here's a little article from Synrad that discusses both of your questions.

http://www.synrad.com/search_apps/application_briefs/Copy%20of%203-1.htm

I have a sample of the Synrad puzzle-piece shown the the link and the edge is very nice with minimal striations. I think that if you have 100 watts of power available then you have the potential to minimize the visible striations on say 6mm acrylic. But if you use a 25 or 30 watt laser to cut acrylic you will likely see marks.

Synrad says a 25 watt laser can cut 1" acrylic but it will look terrible and is not really practicable.

John, what laser power do you have available? If you use a longer FL lens, that will reduce angle, but the kerf will be wider (the spot size will increase) thereby reducing effective intensity. If you have excess power then that could help, but if you don't, then a larger spot size will force you to cut slower. It is all about tradeoffs.

I don't think that a YAG would be used on plastics normally so it must have been something else. Some plastics can be marked succesfully with a YAG but it would not be normal to cut plastics with one. You are correct, the YAGs are generally used on metals.

John Tolman
08-26-2012, 3:29 AM
John, here's a little article from Synrad that discusses both of your questions.

http://www.synrad.com/search_apps/application_briefs/Copy%20of%203-1.htm

I have a sample of the Synrad puzzle-piece shown the the link and the edge is very nice with minimal striations. I think that if you have 100 watts of power available then you have the potential to minimize the visible striations on say 6mm acrylic. But if you use a 25 or 30 watt laser to cut acrylic you will likely see marks.

Synrad says a 25 watt laser can cut 1" acrylic but it will look terrible and is not really practicable.

John, what laser power do you have available? If you use a longer FL lens, that will reduce angle, but the kerf will be wider (the spot size will increase) thereby reducing effective intensity. If you have excess power then that could help, but if you don't, then a larger spot size will force you to cut slower. It is all about tradeoffs.

I don't think that a YAG would be used on plastics normally so it must have been something else. Some plastics can be marked succesfully with a YAG but it would not be normal to cut plastics with one. You are correct, the YAGs are generally used on metals.

That article is pretty informative, thanks for that.

It is a 60 watt, so not too weak. That article talks about air assist settings being pretty important, so I'll mess around with that too.

Mike Null
08-26-2012, 8:07 AM
John

The coin edge you're referring to is a fairly common occurrence with most machines. On occasion I can cut acrylic with minimal coin edge but I don't think I've ever achieved a perfectly smooth edge. Power, speed and frequency settings can produce varying results so experimentation will pay off in improved performance.

My supplier of acrylic polishes the edges of thicker material with a buffer to achieve smooth edges.

Zvi Grinberg
08-27-2012, 1:16 AM
Hi John, no, the HDFO would make the angle worse, not better.

A few HPDFO clarifications.
HPDFO's focal distance is approximately similar to 2.0", therefore if it could theoretically cut thick boards, it would have been with similar angle.

HPDFO has smaller point size. 25 microns compared to ~127 microns with 2.0" lens. Another difference is their focal tolertance. While 2.0" lens has plus-minus 2.5mm tolerance (therefore cuts 5mm thickness), HPDFO has only plus-minus 0.75mm tolerance (max efficent cut thickness 1.5mm).

If we're already on lens specs - With VLS3.60 you have the option to use 4.0" lens. Focal point 0.3 mm, and thickness tolerance about 10mm.
The beam's profile angle is obviously smaller.

paul mott
08-27-2012, 2:33 AM
Hi John,

I have found that cutting acrylic well is a process that has to be learned by practice. I use absolutely minimal air assist (just enough to protect the lens from contamination) and relatively slow feed rates. The software used to create part also has to be right, arcs are a lot better than many straight lines when it comes to producing good edges.
My laser was home built so it is nothing really special or expensive but after much experimentation I can now produce excellent edge quality and I posted these pictures on the forum some time back whilst I was learning.

Paul.