1/2" acrylic with Morntech 80watt

[Konrad Birchfield]

Good morning All,
Lately I have been cutting some 1/2" acrylic with a Morntech 80watt laser, I haven't worked with this machine for very long but 100% power and 5mm per sec sounds a little slow for an 80 watt machine from some of the things I've read on this site. I know that this is an easy question for some of you " old hands" at this, but does this sound on par? I've cleaned the lens and mirrors, and experimented with dropping the focal point down about .025 from the auto focus, and this seemed to help. But this still seems a little slow, any advice or pointers or point me to other conversation on this site would be greatly appreciated.
Konrad Birchfield

[matthew knott]

That sounds about right if not pretty good to me, be intresting to see what feedback you get, we cut 5mm at about 9mm Second with an 80 watt chinese laser

[Clark Pace]

I run 2mm a sec 70 percent power. for 1/2

[Bill Stearns]

All -
Maybe, this is 'good chance for me to ask this question; no shortage of things to learn. I use a 35W Epilog 'n Corel Draw X5. I have settings for raster 'n vector speed and power - and, I can adjust "frequency" 'though I have always used auto frequency. Oh, and I have always used "auto focus". When you all talk 'bout "mm" - a second? - what is it that you are referring to? Some adjustment-setting my machine doesn't have? Related to cutting speed I'm gathering? (don't you hate those times you trip over something, after umpteen years, that would've made jobs easier 'n nicer?) Have 'great day guys! ('n gals.)

Bill

[Bill George]

I run 2mm a sec 70 percent power. for 1/2

Without listing your equipment in your signature line, no one knows its 70% of what?

[Brian R Cain]

All -
When you all talk 'bout "mm" - a second? - what is it that you are referring to? Some adjustment-setting my machine doesn't have? Related to cutting speed I'm gathering? (don't you hate those times you trip over something, after umpteen years, that would've made jobs easier 'n nicer?) Have 'great day guys! ('n gals.)

Bill

I suspect this is a consequence of the way laser systems were developed in the West as yours was, Bill, and CNC technology adapted to run lasers in the East.

If you run a machine where a tool is doing the cutting, you need to take into consideration the surface speed of the tool and the feed rate or you can end up wearing tools out or breaking them. Or you can end up with poor quality work if the feed speed for the finishing cuts are too fast. Manually-operated machine tools often gave feed speeds in in/min or mm/min on a chart by the gear box, so when it came to producing CNC machines, it was helpful to engineers to program in the speeds and feeds they were familiar with, especially as to get the optimum out of the particular type of tool being used, it's diameter and what it is made from. i.e high speed steel, carbide etc. needs to be calculated.

Because laser technology is a non-contact cutting process, you don't have things that can break or wear out in the same way. You might find that getting the settings wrong means you end up not cutting through or resulting in poor work, but that's all part of the process of learning how to get the best out of your particular machine. Add to that the fact that the density of the material you are processing and how the material reacts to being heated by the laser means that any formulas that worked with cutting tools no longer apply. By this I mean you could run a CNC milling machine with a solid carbide tool on pretty much the same setting for any plastic and get acceptable results, but not with a laser.

Then it depends on how powerful the laser is. What you think is a 35W tube on your machine is only a nominal power. You might have more, you might have less and over time, tube output will fall off. The settings the manufacturer gives are only a guide.

Further, Western laser cutters adapted plotter and printer technology to drive the machine whereas CNC technology uses G-code, so if you have an Eastern machine that works like a traditional CNC machine with an adapted interface to be used with a laser, you need to program feed speeds as you would a milling machine.

Believe me, you have the simpler interface to use and you would gain absolutely nothing other than grief if you had to set feeds in mm/sec.

[Bill Stearns]

BRIAN -
Thanks for clearing that up for me - my "mm" question - you have just been promoted to "guru" in my eyes. So very thankful I don't have all those issues to worry 'bout. e.g. tool wear or breakage, etc. (I've read guys mentioning "mm"s- and "g-code" all this time and wondered what it was all 'bout.) Makes my laser engraving seem so simple! - like child's play. BTW: interesting what you said 'bout my 35W tube. I am growing concerned, as I am into my 8th year. I've always tested and found my own settings for various materials - 'stead of using the chart - so, wondering how I'll know for sure when it's time for replacement? (just know it's gonna happen in the midst of an urgent project.) Hope it's not rocket-science to replace it. Thanks again for the info.

Bill

[Konrad Birchfield]

Thank you very much guys,
Brian, that is a very astute observation and I appreciate yours and everyone else input greatly.
Bill, the issue with frequency is an issue that I also am trying to find manual control over for cutting. For the longest time I was under the impression that it only had to do with DPI, but this is only manually controllable when in scanning mode or raster. The only way I've been able to figure out how to control frequency is to switch to dot mode and make the dots long and very close together. But I have a lot to learn and I'm sure this is a great place to learn it.
Konrad

[Clark Pace]

Hamna Laser (Chinese). Sorry was in a rush . Is 100Watt. On that machine 80% of my works is done in 1/2" acrylic

[Dave Sheldrake]

5mm P/S on an 80 watt DC pipe is good, 5mm P/S on an 80 watt RF box is pretty normal. Morntech / Shenhui are the same company effectively so spares won't be a problem.

cheers

Dave

[Kev Williams]

My 40w New Hermes LS900 cuts thru 1/4" at around 5mm / 1/4" per second. I can go thru 3/8" in one pass but it's really crawling. So 5mm/sec with 80 watts doesn't seem out of range...

Bill- as for speed increments, just seems to be a who-built-it thing. My Triumph speeds are set in mm/second (or per minute, per my choice)-- but my LS900 and my old ULS/NH Optima's speeds are set in "percent". Percent of WHAT is the $5 question, as I really don't know the actual maximum speeds of these machines. And even if I did, is the machine actually running at the percentage I'm telling it? Don't really know. I just find what works then save the settings!

[Keith Colson]

Is there some reason that people choose to not use 100% power and run the feed at a slower rate? I always run mine at 100% power and set the speed accordingly. Is it something to do with laser tube life?

[Clark Pace]

I only do it because the manufacturer suggested not to run at %100. And I seem to get a smoother cut.

[Dan Hintz]

Is there some reason that people choose to not use 100% power and run the feed at a slower rate? I always run mine at 100% power and set the speed accordingly. Is it something to do with laser tube life?

For glass tubes, you don't want to run at 100% if 100% is above a certain maximum current (around 24mA for 60W tubes, if memory serves)... the "better" factories will detune their power supplies to align 100% with the "safe maximum", others align it to the hottest the tube will go (at reduced service life). For sealed tubes, there's no reason in terms of service life.

That said, if you're cutting thicker plastics (particularly acrylic, since the edge is often visible), slowing down the speed and reducing power to match will typically net you a smoother edge with fewer striations.

[Keith Colson]

Thanks Dan that's really good to know. I have worked with vacuum tubes during my appreticeship many years ago and I remember that running them colder extended their life so this all makes sense. I will re-tune all my profiles for 70% and see how things go. I am interested to see the difference in the acrylic edge too. I also realised that my jobs will take longer so that means I make more money too based on an hourly rate!

Cheers
Keith