My review of buying a Triumph laser.

[Dave Sheldrake]

Lemme see Kev,

Leaving aside higher power lasers (1Kw +)

RF = Radio Frequency tubes, they use the same/similar gas as a DC tube but the beam is generated by an RF signal
DC = Direct Current tubes, they are excited (the beam is generated) by a very high voltage arc inside the tube (circa 20,000 to 45,000 volts)

DC tubes (in general) do not have the availability to have their number of pulses per inch varied, RF tubes do.

Your ULS and Gravo are "likely" RF tubes.

Different materials have different values at which they absorb radiation (the beam) a CO2 laser provides a beam of 10,600nm (in rough terms) a YAG and a Fiber laser generate beams in the 1064nm wavelength.

Aluminium for example is highly reflective to the 10,600nm wavelength but absorbs 1064nm wavelength very well. Therefore aluminium will require far far higher power to cut/mark if you use a CO2 laser compared to low power for a Fiber or YAG.

A 20 watt YAG/Fiber will outperform a 200 watt CO2 on aluminium because of this.

Wood absorbs radiation (the beam) in the 10,600nm wavelength very well, but does not in the 1064nm wavelength so the CO2 laser will outperform a YAG or a Fiber on wood.

Wavelength:

This controls the smallest possible size of your laser spot/dot.

A YAG or Fiber can in theory produce a dot 10x smaller than a CO2 making them very good for fine detail work (depending on the material type etc) as well as being able to mark directly on most metals.

Chinese YAG / Fiber Galvo markers start at around $10k and go upwards. (be aware they are pretty poor if you want to cut items though)

A triumph machine with an RF source is like fitting a Ferrari engine to a Skoda, you can do it but do you want to? you would end up with a $5k machine with a $10k laser in it if you wanted 100 watt or so.

My apologies if this comes over as overly simplistic but I'm not sure quite where your level of knowledge is of Lasers in general.

cheers

Dave

ps:Z series tubes have better internal mirrors and slightly higher peak powers but past that in real terms not much different. To be honest I prefer EFR tubes as they seem to be more stable.

[Joseph Belangia]

Hey Dave,Thanks for breaking that down for us. My wine-level was at the perfect spot, and I followed it through....pontificated...maybe had another sip, and then considered myself a bit smarter leaving the day than I came into it.

[Dan Hintz]

If you want high quality marks on aluminum, you are better off with YAG or Fiber.

I disagree. A large part of my business has been marking anodized parts, and I wouldn't do so well if my parts came out fuzzy. Yes, you can certainly get finer detail with a YAG/fiber, but most would be hard-pressed to know the difference unless they were looking for 2-pt fonts.

[Robert Silvers]

Well, both of us are correct. You can sell C02 marks to people and they will be happy with them - I have bought products that have C02 marks on aluminum, and while I wondered why they were soft, I didn't mind. If you show them next to a fiber mark, the fiber will be clearly better to just about anyone. So I guess it depends on what level of quality you are going for.

I would bet a lot that a $15,000 Chinese fiber laser will produce much higher quality marks on aluminum than a $20,000 Epilog C02 laser.

[Dan Hintz]

Here's one I did years back... it was not dialed in, but it's a reasonable sample.
Anodized Aluminum Mark.jpg

Now, feel free to pontificate on how much better a YAG/fiber will do compared to this, but those arguments have been bashed again and again here. If the above is not acceptable to most customers (this is an automotive engine part), then they'll pay the price for a more expensive fiber machine to do the work, simple as that.

[Kev Williams]

Hey, oversimplistic is fine by me! And I do understand (to a point) the basics of electronics, just never learned the nuances of my lasers- or lasers in general. It's nice to learn something about them!

OK then, since I can set the X-axis dots-per-inch on both my machines, I'll assume I have RF lasers...

Next-- regarding DC tubes aren't 'typically' able to vary their firing pulses per inch-- question, if the pulses can't change, then wouldn't the correct static measurement be pulses per second? And then wouldn't the laser head speed then be the deciding factor in actual pulses per inch? Meaning, the slower the head speed, the higher the dots per inch resolution...? And if so, then slower speeds should render better results? Yes, no?

Below is a couple of pics of another piece of anodized I just did, with the letter heights, down to .025" tall letters, and while the smaller letters do get fat and a bit fuzzy, they're still easily readable with even my old bi-focaled naked eyes! I wonder if Robert (or anyone else too?) would mind running a similar sample(s) and posting a photo of the results? I'm very curious about this now-- As much as I'm ready to break out my checkbook and get one of these, I'd really love to see some unbiased samples of some small text engraving! (sorry if I'm being a pain!)

[Dan Hintz]

Meaning, the slower the head speed, the higher the dots per inch resolution...? And if so, then slower speeds should render better results? Yes, no?

You have to keep in mind that each pulse of the laser (RF or DC) has a finite size... a circle of material will be bleached, vaporized, etc. For a 2" FL lens, that spot size is typically around 5 mils for a good beam (RF tubes), maybe 7-9 mils for a lesser quality beam (generally DC tubes). That sets the max resolution you can truly have. Overlapping those dots will give you a smoother edge, but in the end the resolution of the final image is relatively limited to the minimum dot size you can achieve. For a 5 mil dot, that's roughly 200dpi if the dots don't touch, at half overlap that's closer to 400dpi... but as you can see, the smallest feature you could hope to create would be 5 mils.

You can play tricks, so to speak, however... setting the print resolution to 1000dpi will allow you to print an 8 mil wide line (two dots almost completely overlapping), but you can still go no smaller than a 7 mil thick line. Keeping this in mind will help you set an appropriate print resolution, allowing you to trade speed for final image quality. For example, when printing to wood, I could print a decent image at 333dpi. Jumping up to 1000dpi doesn't really gain me any extra detail because the substrate itself is fairly low resolution... but it would gain me a deeper (or darker) engraving at the expense of more time.

[Dave Sheldrake]

Sit on your money for a bit longer Kev, quick decisions on lasers usually end up being bad ones

DC tubes as mentioned above tend to use a PWM control (Pulse Width Modulation) if effect meaning you vary the length of the Pulse (laser on time)
RF tubes tend to use PRF (Pulse Repetition Frequency) in effect meaning you vary the number of pulse in a given time (distance when related to speed)

PWM = Length of pulse in a given time
PRF = Number of pulses in a given time

It is possible to vary the frequency of a DC tube but is a bad idea, the electronics / physics behind it is quite complex but it can lead to a far shorter lifetime on the tube if you do.They are designed to run within a small variation on frequency for 99% of Chinese tubes. Some western tubes like GSI Slc's can be varied but a 200 watt GSI Glass tube is just short of $25,000 for the tube alone compared to $3,500 for a 200 watt Chinese tube.

The 0.025" lettering you have posted is below the 1mm size a typical Chinese DC laser will produce, YAG and Fiber Chinese machines will go to 0.5mm but a DC Gantry (plotter type) will rarely give good results below 1mm x 1mm font sizes.

Be aware also China is very good at making some rather *generous* claims about what their machines will do, such as cutting 30mm acrylic with a 100 watt tube etc, yes 99% of what they say is true but rarely includes the caveats we all really need to know. 30mm acrylic WILL cut on a 100watt DC tube but at 0.1mm per second and the quality will be terrible.

Often the statements are true but the meaning behind them isn't.(you get given just enough information to come to the wrong conclusion)

Don't get me wrong I love Chinese lasers (and have/have had) quite a few of them, just don't be fooled into thinking they are everything that is sometimes claimed.

I have Chinese, Western, German and Japanese lasers and they all have their place but none of them are a "one size fits all" kind of solution.

cheers

Dave

[Kev Williams]

I assumed a fatter dot with a Chinese machine, but wasn't aware of why exactly until now! So should a assume a tighter dot result should be able to be had using 'tighter' 1.5" or so lens? I realize focus is more critical with a tighter lens but that shouldn't be an issue with flat aluminum panels. Realistically, if I can get crisp lettering down to .050" tall characters, that would be sufficient...

[Robert Silvers]

Kev - the spot size mostly has to do with the emitted beam diameter. You may want to find out the emitted beam diameter of any tube or unit that you are considering, because then you can calculate how small the size the spot may be. I am sure RECI will tell you their beam diameters if you email them.

Here is a spot size calculator:

http://www.buildlog.net/cnc_laser/laser_calcs.htm

And here is some info:

http://tinyurl.com/ksnvlch

http://www.parallax-tech.com/faq.htm

[Kev Williams]

Thanks for all the good info Robert, Dan and Dave, much appreciated! As I said in my previous post, if I can get basic lettering to look good down to .050", then I'm good to give it a shot. The price of the machine is about what I spend every 3 months on materials, so it's not a huge gamble for me. And hey, biz was so good this year I need a tax deduction!

I have plenty of work I know the machine is definitely capable of doing nicely, and I have a new wood customer with jobs that require a high-power machine capable of engraving 8' long boards. The work it WILL do will free up the other 2 lasers at the very least. My utmost hope is the increased production the bigger laser (and the IS7000 I'm getting next week) will jog my biggest customer into sending me a few of the 6000+ jobs someone across the pond is doing for them.. Just a small piece of that pie will allow me to buy WHATEVER I need later.

[Dave Sheldrake]

Beam modes vary between tubes Rob, RECI are usually good but TEM01 - TEM08 isn't unusual. (the shape of the beam the tube produces)

Kev, yup shorter focal length = smaller spot but not always better spot quality. Focussing a big incident beam (the incoming beam from the tube) to a smaller spot also increases aberration (a straight beam going through a curved surface).

I'd probably look at going with an EFR ZX series 80 watt tube and a 38mm focal length lens.A Meniscus lens from II-VI InfraRed will give better quality without costing an arm and a leg (China tend to supply Plano - Convex lens's)

cheers

Dave

[Robert Silvers]

My attempts at cutting 1 inch acrylic.

Is there any way that I can improve this? The focus was a bit below the surface. I also tried surface focus, but I didn't like the taper.

So far I have not been able to get better edge quality by using lower power.

[Scott Shepherd]

My attempts at cutting 1 inch acrylic.

Is there any way that I can improve this?

My educated guess would be "No". That's wayyyyyy too thick for that power laser with that lens setup. I have a 3/4" piece that looks awesome and it was cut on a 400W laser.

[Robert Silvers]

Can anyone explain why more power at a faster speed is better than less power at a slower speed?

If it is heat transfer causing distortion - I get it, except that yesterday I was told to turn down my power to get better cuts.

This test seems to show that more power is better.

Would a four inch lens make a big difference?

How long does it take to switch between lenses?