Engraving with a RECI tube - what's the general consensus power that actually works?

[Ian Stewart-Koster]

Hi Folks,

Now that our ULS is running, I've been engraving acrylic, and Cermark, but am limited by the 24 x 12" bed area - but it does a beaut job.

Our Chinese Goldenlaser is pretty woeful at engraving - 130w - W4 - Reci tube. Even at low power there are issues, and it's nothing like the quality of the ULS RF tube. I understand that. (nor is it as quick)

My question is which size of RECI tube will do a passable comparison at ENGRAVING, because I'm in the market for a bigger laser (2500 x 1300mm bed), and am considering a 2-head machine, with 2 tubes, one for cutting (W6- 180w) and one for engraving (W1 or W2 - RECI - 80-90 watt).

(I'm not sure I can afford to go to 280 watt with Jongli paired tubes, though it'd be nice, but it's a USD $5k surcharge over the 180watt unit, but I'd still like to be able to engrave on big panels)

Thanks for any opinions...I've been liasing with a fellow in China. (Threecnc machinery co. ) Their big unit has a RD-6442-S controller, Leadshine drives & steppers, CW6000 chiller...

[Ian Stewart-Koster]

P.S. The RECI website is not very encouraging: "Engraving function: Very good. When the working current is 4mA and the tube is in the state of preionization, the laser can be used for high-frequency impulse engraving." applies to ALL their tubes... and I don't believe that in the bigger ones...

[John Lifer]

My engraving is fairly decent. I don't think any glass tube engraves as good as a RF tube, just the nature of the beast. But Mine is only an 80watt, and I do have issues at low power, just won't cycle fast enough. I think if you will read past inquires, there is no one who uses 100 watt and higher for good engraving.
High wattages are for cutting. 130 watt? disappointment will most likely be the result. Just too much power.

[Ian Stewart-Koster]

Thanks, John, that's exactly what I thought - hence my asking those here who might have something in that 80 to 100 watt region, just how or what standard their engraving has been...?

[Kev Williams]

The 80w RECI in my Triumph engraves just fine, and I have the settings dialed in to where the engraving quality is very close to my Synrad powered LS900 and GCC Explorer.

Did these samples awhile back with all 3 machines, black Rowmark,
I believe the plate size is 1/2 x 2-1/2", as you can see, not much difference between the 3 machines-
(btw, "sample" font is Cloister Openface, which is why it has hollow spots missing)
375810
Note the power used is 16%, I can run consistent marking at 8% power, which isn't enough to engrave Rowmark.
FWIW, a 70% setting entered = 26mA (100%) on my meter...


My Triumph did this on aluminum, pretty impressive small detail.
Neither of my Synrads have enough power to fuse Cermark to aluminum at all.
375809

[Bill George]

Kev, When do you have time to work? Or to wind down? Your always solving problems!! Kind of like my new Border Collie pup.

[Dave Sheldrake]

80 watt is the upper limit in reality Ian, above that the tubes won't fire low enough on occasion to be useful. Added to that, the bigger tubes have a bigger exident beam therefore a smaller spot size hence higher power density compounding the problem.

[Ian Stewart-Koster]

Thanks for the replies, and info.
Dave, by 80w, do you mean eg a 100 watt tube that masquerades as 80 watt because you should not go up to 100% - like the Reci W1 ?
Or a lesser 80 watt tube?

The Reci W1 says 80-100w, but the Reci W2 says 90-100... That's weird sort of semi-deceptive marketing ploy, I'm thinking...

[Dave Sheldrake]

That's weird sort of semi-deceptive marketing ploy, I'm thinking...

It is

seen it many times from vendors including Western vendors

"100 watt laser" and it's partly true, when it triggers with it's spike current it may well put out 100 watts but if you tried to use it at that power for any length of time the tube would quickly fail.More often that 90-100 watt Trigger spike will settle back to 85 - 90 on a new tube and 75 - 80 on an older tube.

So yes, it's technically a 100 watt tube as for a split second it was emitting 100 watts, soon after though it was back to 85 :)

[Kev Williams]

FWIW, awhile back I was reading directly from some RECI webpage (that I can no longer locate) that they test their tubes at something like 34mA - don't remember if this was specific to 80w tubes? Anyway- my tube has a 'tested' output noted on the tube of 110w, which sounds feasible if tested at mA's well into the 30's. It also sounds feasible to me then, that at around 25mA my tube should be putting out an honest 80 watts.

But it sounds like many sellers would market my machine as equipped with a 110w tube, just because it tested that high... not a lie, but not exactly true ;)

[Ian Stewart-Koster]

I've just discovered the same thing, Kev.

Our Chinese laser I'd always called "130 watt", and started assuming it was 130w, therefore rated at 100w, a reci W4 tube.
I'm wrong!
I've just put a tapemeasure over it, and the tube is about 1600mm long, plus end caps, 80mm dia, which put it as a W6, 150/160 watt peak, but rated at 130 working watts.

That explains why people keep telling me I cannot cut 20 & 25mm acrylic with it when I have been doing just that.
It also explains the purple band at the negative end - which suggests it's nearing the end of its 5 year life.
When the software is at 100%, it's now putting 19 mA out to the tube, whereas 6 months ago 100% was 21-22 mA.

(I'm going to assume that's a tube problem and not a power supply problem.)

[Ian Stewart-Koster]

Kev, regarding your Triumph: which brand and size tube does it have ?

[Kev Williams]

It's a RECI 80 watt. Model I'm not sure... I've had it since November 2014.

[Rich Harman]

My 80W Reci is much better at engraving than my 130W Reci.

For best engraving you want the smallest tube Reci makes. I don't think Reci has made a tube smaller than 80W.

[Mark Canada]

Sadly, this is more of a case of powersupply than tube. The CO2 arc tubes can fire pretty quickly if the powersupply holds the tube just below its ignition amperage (the pre-ionisation state RECI mention) - but very few CO2 tube supplies have the option to hold a tube there between pulses - so the tube needs to ramp up to an arc then go off, so if you're trying to do super fine dithered engraves it just can't switch on and off fast enough no matter what speed you move the head. This is why RF lasers totally blitz arc tubes for engraving, they can turn on and off in nanoseconds vs milliseconds.


Invest in the best laser powersupply you can - I noticed significantly better results with a genuine RECI P4 powersupply over the cheap chinese ones and I also wasn't blowing the powersupplies every 3 months (over voltage delivery from the utility company wasn't helping).

[Dave Sheldrake]

^^^ Yup the decent RECI and EFR power supplies can do this but not many others

[Ian Stewart-Koster]

tHANK yOU!
tHAT GENUINE POWER SUPPLIES ANSWER IS A GREAT HELP!
(oops, sorry about the caps lock!)

But there must need to be a setting in the software somewhere (RD Works) where you can call up an option to trickle the minimum current like that ?

[Dave Sheldrake]

Yea there is, im at work later, I'll have a look and see where ours are set up to do it

[Mike Lysov]

There was a seller from NSW on eBay recently and he was selling... not sure either his own laser or as its distributor. The specs stated that he has a 260W tube so I assumed he was talking about a DLT-260. He was claming in the ad that this laser can also engrave. I contacted him via eBay messages and asked him how he made it possible as high power tubes cannot do it. He replied with something like "buy lasers from me and I will explain" He also said that he has some special settings to make this tube to engrave. Not sure if he simply lied to make a sale or indeed found a way to engrave with a 130W tube or even both tubes firing at the same time.

[Ian Stewart-Koster]

I saw that ad also, Mike... and shook my head and decided it was an opportunist...

Keen to see if Dave finds a setting in RDworks for setting the minimum orr a trickle current for a Reci tube...

[Rich Harman]

...Not sure if he simply lied to make a sale or indeed found a way to engrave with a 130W tube or even both tubes firing at the same time.
A 130W tube is not the best for engraving, but it surely can do it.

[Ian Stewart-Koster]

My own experiments - not properly tuned - were with our Goldenlaser 150/130 watt - engraving was 'possible' but not worth it, compared with the quality from the little ULS M-300 (50w now) - unless it had to be bigger than i could fit in the ULS - and even then, quality was still iffy with what we had...if You knew how good it should have been.

[Mark Canada]

I did some engravings with a RECI Z6 that i thought were pretty great, the variable power ones looked the best. Its not like you'll get trotec quality, and only a fraction of the speed, but its not like they can't do it!

Bamboo floorboard:
https://photos.smugmug.com/Lasers/1290-Laser/i-b6T6mLN/0/ce729a08/L/DSC_9303-L.jpg

Granite:
https://photos.smugmug.com/Lasers/1290-Laser/i-BwvNTPg/0/310cf8e2/L/DSC00551-L.jpg

Anodised aluminium, about 3" wide:
https://photos.smugmug.com/Lasers/1290-Laser/i-6W2s9J7/0/fb8a7dad/L/DSC_0389-L.jpg

detail of the pilot:
https://photos.smugmug.com/Lasers/1290-Laser/i-n6BMGb7/0/80a63a14/L/DSC_0391-L.jpg
The picture of that wasn't the best, it was a bit low res being an old war photo i found online.

glass:
https://photos.smugmug.com/Lasers/1290-Laser/i-ZJqSPWx/0/4acb9252/X3/DSC_0315_DxO-X3.jpg

When doing dithered pieces, you can definitely see the limits for laser turn on/off time, lots of missing pixels. Dithering strategies can help overcome this, as can lightening or darkening the image in editing software prior to lasering to bias towards more or less pixels.

I forget what the settings were for these, but they are all the same photo:
https://photos.smugmug.com/Lasers/1290-Laser/i-bqxPVDc/0/e054b55c/L/DSC00632-L.jpg
https://photos.smugmug.com/Lasers/1290-Laser/i-zRfMqdc/0/104376a8/L/DSC00631-L.jpg
https://photos.smugmug.com/Lasers/1290-Laser/i-LMv4NXV/0/e040c4cf/L/DSC00633-L.jpg
These are all done with an RDC6332G controller, and the cheap chinese powersupply the laser came with - the P14 helped a lot for the dithers, but I don't have photos. I've just noticed that RECI have a new powersupply out that superseeds the P14, could be worth a look.

[Ian Stewart-Koster]

Thanks, Mark. That's interesting. The anodised Al came up well. The rest of what you said makes sense. Your last lion pic is getting there.
I know our Chinese machine's photo engraving quality is woeful compared with the ULS, but at 150w, it's expected...

[Kev Williams]

So, Mr. Sheldrake-- really dumb (or maybe not) question-- is there such a thing as 'sunglasses' for a C02 laser? As in, a lens or aperture or some other device that could simply block or absorb (which may be a bad thing) some of the incident beam before it gets to the regular lens? As a weird reference, the way Gravograph 'focuses' the red pointer beam on my IS400 to a very narrow point is simply by shining the beam thru a very tiny hole. It does work, the spot is very bright and extremely small...

Out in the garage shop I have 3 laser pointers... I cut a circle out of some .010" brass shim stock, found the smallest drill bit I could find around here (about .015" diameter) and drilled it, then taped it to the front of the pointer, and now the relatively fat beam spot is very tiny and bright, much better for accuracy. I use this pointer thru the lens on my Triumph as it didn't come with one...

Anyway, just wondering if there was some way to temper/buffer/diffuse/reduce the beam intensity, so that higher powered tubes COULD engrave better? Without creating meltdowns, blinding someone or starting fires, of course! ;)

[Mark Canada]

Thanks, Mark. That's interesting. The anodised Al came up well. The rest of what you said makes sense. Your last lion pic is getting there.
I know our Chinese machine's photo engraving quality is woeful compared with the ULS, but at 150w, it's expected...
The thing I didn't realise when I was doing those lion engravings was that you shouldn't use air assist when engraving, as it blows the smoke back onto the work and discolours the wood (or in the case of acrylic, deposits acrylic powder in the engrave). I didn't learnt that until I went on a course at Trotec about 4 years later! Those lion engraves actually look a lot better after being hit with a very light touch of sand paper on a hard block (so it can only take the very surface off) - leaving the engrave dark and the surface light.

The really interesting thing with the CO2 tubes is the lack of shading inthe light areas - this is where the fiber and RF lasers really shine so to speak. In the raw picture where it's varying the power level to do the engrave you can see much more shading and you also get the sky engraved. On the dithered versions, the original image has many black dots in the sky area (you can see on the left on the lion's nose in Gimp2, top and bottom right corners in several images - but the laser can't switch on fast enough to engrave them. Then on the darker areas, the laser gets to turn on because there are several dark pixels in a row or close enough together that the tube does ignite - but the very small pockets of light pixels in those areas are lost as the tube won't de-ionise fast enough - so it's still creating light after its turned off... then comes back on again very fast to keep the dark engrave going. Those images are probably a realistic 500dpi along Y, but across X you probably only get white or dark features that would fit in a 250dpi print - ie: about 0.004"/0.1mm.. maybe even 1.5-2x that.

With a better powersupply, you can do better. That was on the stock powersupplies I blew 2 of (JNMYDY brand).


Kev, I'm not sure that's the solution, a CO2 tube should be able to fire at about 10-12% of it's max power, so a 150W laser should be able to do a 15W engrave which isn't a lot for wood, acrylic or anodised aluminium, at least in my experience (with the Z6 I was always at about 30-40% for wood, 100% for aluminium) - this is purely related to chinese lasers - on a trotec i'd be going 85-100% power for pretty much anything haha. I think the problem is more the tube length if you're having issues, because you need to ignite a much longer tube it takes longer to ionise/deionise? That would be my guess as to why a low power CO2 laser is working better - its faster to arc up and for the arc to break down.

[Mark Canada]

I'm actually thinking for the laser power and pre-ignition (firing the tube a say 8% power), it wouldn't be too hard to make a little bit of microcontroller code to pull up the laser power line to the correct voltage for say 1 second after any laser pulse. I don't have a laser to test on at the moment, but it's certainly something I can look into if anyone's interested in trying?

[Dave Sheldrake]

So, Mr. Sheldrake-- really dumb (or maybe not) question-- is there such a thing as 'sunglasses' for a C02 laser? As in, a lens or aperture or some other device that could simply block or absorb (which may be a bad thing) some of the incident beam before it gets to the regular lens? As a weird reference, the way Gravograph 'focuses' the red pointer beam on my IS400 to a very narrow point is simply by shining the beam thru a very tiny hole. It does work, the spot is very bright and extremely small...

Yup there are Kev, Beam Attenuators, usually quite pricey (I blew mine up when I forgot to turn on the cooling) basically lens's designed to absorb some of the beam energy and dump it as heat into the cooling fluid.

Lower power tubes have a smaller incident beam so in general a bigger spot size hence much lower power density, I won't usually engrave anything plastic using more than an 80 watt at 15% or so power with 2 inch lens (just enough the whiten up the surface)

[Dave Sheldrake]

The problem isn't Voltage Mark, it's current, DC tubes usually fire at well above the operating current just to get them going (hence the *dig in* at the start of the line) pre-ionising reduces rise time but doesn't make any difference to the spike

[Ian Stewart-Koster]

I've been doing some experimenting, engraving an image that's about 24 x 10 inches, on acrylic.
The ULS did a great job except it could not handle the memory size of the BMP (quite small), so I had to drop the resolution down to 105 ppi before it would do it.

The Chinese Goldenlaser did a rough job, but that was with the 4" FL lens. Tonight I changed the lens for a 2" one, and ran some more files.
Very impressive, actually. I got the power down to 20%, and at that level, (speed 800, acceleration 1500) the ammeter was peaking at 4.5 mA or so.
Not perfect, and not as good as the ULS, but totally quite acceptable!

[Clark Pace]

I have a redsail and engraves great. Slower though. I had a uls for years but had to sell it. Engraving on my redsail does not engrave as good but its close

[Doug Fisher]

>>As in, a lens or aperture or some other device that could simply block or absorb (which may be a bad thing) some of the incident beam before it gets to the regular lens?<<

If you have a Ruida controller, when in scan mode (engraving) you can select between "common mode" and "special mode." Special mode might do what you are seeking but the manual seems to warn this mode can shorten the life of the tube.

[Ian Stewart-Koster]

Thanks very much for all the suggestions.
Details so far: I decided that it would be a worthwhile effort to get soime figures down that would be useable, on the big Goldenlaser, because the you-beaut flat-bed machine I've ordered from China is in go-slow mode due to their new year holidays there right now.

I tried the Goldenlaser 150w on assorted settings of power, speed and acceleration, and also resolution. And focus.

Conclusions:
1. get rid of the 4" FL lens and use a 2" lens - that was the best help for starters.
2. I tried power variations from 18% to 32%. Of course the depth or effect of that varies depending on speed and acceleration... coinsidering the firing and turning off of the tube in a hurry.
3. I tried assorted speeds and accelerations - the faster speeds at a set acceleration needed a lot of landing and turning around room, (up to a foot each side) while the slower speeds needed barely an inch of turning space past the image.
The faster speeds gave a more blurred image, and lower accelerations didn't help either.
Changing too many parameters at once was useless as you didn't know what one had the greatest effect.

IN the end, I established that although I could set the acceleration at up to 5000 unspecified units, 1500 worked well. 700 did not.
Speed - I tried at 1600 mm/sec, 800. 600. 400, 200, 100. The slower speeds were a heavier burn to a degree, and to a degree they were not.
They were also a sharper image.
IN the end 400 was nice and clear, but overall too light in tonal density, while 200 had too much white etching blotting the picture more than I wanted, so I went for 300 mm/s speed. (at 1500 acceleration)
I had tried assorted power settings, but settles on 30% as giving me what I liked the look of the most.
It may be a linear scale such that I could go lower, and slower, but I'd put enough time already into it, and the 18-26% trials were just too light for my fussy preferences. And there reaches a time when you don't want to wait all day for it to end...

Resolution: I'd created the original file as a photoshop composite of 6 images,( for various reasons- that's another story not important for now), and made it at fullsize ( 8' x 3') at 144 pixels per inch. After some judicious sharpening (unsharpmask, contrast tweaking, blurring of unwanted JPG artifacts, resharpen edges, blurring background more to remove detail where it would be a distraction, enhance detail where it was going to be appreciated, then fiddle the curves or gamma, for a nicer blend of greys in between the darks & lights that were necessary, and fiddle the curves so there were no 100% blacks or 0% whites blowing out, but instead 92% and 6% at the ends of the range, for detail in the shadows and in the lights... and more fiddling and more... plus I had to fake the train smoke, then delete the background altogether, flip it, and make it a negative. Then convert to BMP with diffusion dither and save. 8.5 meg total size of BMP.

The small 1/4 length samples ( 2' x 8") I had the resolution at 288 ppi, but the laser could not handle the memory needed - weird- as it was only a 2 meg file... so I enlarged the scan gap from 0.088 to 0.167 ( double) and it was happy.
The samples allowed me to test the various power, speed & acceleration options.

As I said I settled on E=30%, S=300mm/s, A=1500, Scangap 0.167.
Later I'll upload some sample photos.
After that I cropped out a 26 x 12" square at fullsize, 144 ppi, and ran it on the above settings - absolutely BEAUTIFUL!
Again the machine's RAM could not handle the 0.088 scangap, but was happy with 0.167

So, for a 150 watt machine, chinese, the engraving standard is/was in my opinion, on this job, phenomenal for what I need- after I'd figured out the best tuning of the variables.

Whether I've damaged the tube or not, I can't say, but the slower speed gave it more time to rise and fall, compared with the higher speeds.
The negative end of the tube is purple - and the RECI website says that is a sign that the tube's life is largely spent, but I'm not to blame for that colouring!
I ordered another tube from the same mob who're putting the big laser together - as freight would be $1k or more on a single tube Reci W6, but freight will be about zero when combined with the big unit. Their price was great - $680 USD, because I'm already buying the rest from them.

In the mean time, this RECI tube has improved a bit, and now runs on about 20-20.5mA when I set the software power at 100% - and it was only on 21-21.5 mA when we took delivery last year. (it had been sitting down around 18mA for a while, cutting).
__________________

So, my next query will be about stitching pictures together to engrave something larger than the bed - but I'll start a fresh thread for that.

I'll add photos here when I get them off the phone.
Thanks!

[Ian Stewart-Koster]

This is the actual FULL-size sample, beside my hand, for scale, of the settings I ended up being most happy with.
378080

Below are steps along the way to achieve those settings:

This is the 1/4 length, 1/4 height sample of what the finished product will be like- this is 2 ft long: I didn't like the train smoke so changed th at part of the file & edited it. Also added subtle detail to the bridge supports.
378081

One of the earlier ones...
Offhand it looks like the good final balance of light and dark, but crummy resolution.

378084

This was a bit too light/faint- at 400 mm/s speed. Not enough whiteness.
378083

This was too slow at 200 mm/s and this was with the 4" FL lens- way too much white/burn and blown out detail)
378085

[Mark Canada]

Nice work!! I think you discovered one thing I forgot to mention - massively over sharpening (unsharp mask) the image really gives massive edge contrast for the laser to work with. It looks horrendous in photoshop but amazing in print - this is something I never learnt before I sold my chinese laser. Even on the Trotecs I had access to in Canada it changed a muddy picture into a work of art pretty quickly. I really like your idea of going 6%-92% on the levels, thats very smart I'll make sure to remember that (hoping to have another chinese laser delivered in 2 months)!

That first pic is definitely something to be proud of. Well worth the time experimenting.

[Ian Stewart-Koster]

Thanks for the compliments, Mark.

Yes, unsharpmask is the key! I learned that when lasering a photo of our clydesdale team in plywood. You need unsharpmask to create detail where there mightn't ordinarily be any. I often go up to 500%, and then a rerun at 180% after that.

The 92% black maximum & 6% white minimum learned when editing photos 18 years ago for halftones for printing in a book.
I apply the same principle to photos when we have to screen print them.
100% black becomes a detail-less puddle of ink when you account for dot gain - so does 95-96%. 92 is dark but allows for detail in the shadows.
(I'll only leave text at 100% black)
0% white is a blowout of nothing- no image- and 5% when you account for screen blockage is often also printed as nothing. 7-8% or so becomes a faint pale grey to show you what you need to see, and that it's not just paper background but actual picture.

Ctrl-M in photoshop edits the curves to apply the percentages most easily, I find.

The actual photo I said was a composite- the best bridge pic was a setting sun one - and anpother of the carriages was the same, but the resolution was woeful - a 65k photo! The train in that pic was running the wrong way, and the clarity was zero. So I git the train from another pic, but had to get the needed detail and needed light and angle. I visited a few trains with the camera to get the right one, and right lighting - many trains are just all black and dirty, and many appear like that in photos too. The best train pic was stationary, so I had to fabricate the smoke for it... The bridge posts/piers were poor in all pictures, so i went and took my own- although the bridge is gone, the posts remain.
Just had to get the light right, and then Photoshopped the shadows in on the lowres pic...

Long story but worthwhile project! Just have to finish it! The attention to detail is appreciated in the end

[Mark Canada]

Thanks for the tips, I'll remember those and try some pieces I attempted last year again once I get my new laser. The trotec just made a big black blob of all the shadow areas, so sounds like your tips will help a lot!

[Ian Stewart-Koster]

The other useful tool in Photoshop, Mark, is the 'dodge' (looks like a lollipop) took. You can set it to just lighten the darks only, and then mouse over areas to lighten and get the extra detail in blackish shadows. Like extreme use of unsharpmask, it does not hurt in this process, but helps.

[Mike Thornbury]

Thanks for the replies, and info.
Dave, by 80w, do you mean eg a 100 watt tube that masquerades as 80 watt because you should not go up to 100% - like the Reci W1 ?
Or a lesser 80 watt tube?

The Reci W1 says 80-100w, but the Reci W2 says 90-100... That's weird sort of semi-deceptive marketing ploy, I'm thinking...

Reci aren't deceptive - they are the most honest and thorough of the tube makers.

They give you four ratings: max, rated, operating and long-term power.

Reci, EFR and SPT are all reliable and honest with their descriptions.

As to 'not go up to 100%', where did you get that nugget of misinformation?

IF you don't calibrate your machine properly, you're bound to have issues.

[Kev Williams]

My Triumph is 'calibrated' by mathematics ;) --

I have NO idea if my power supply can be adjusted to match actual power percentage relative to max mA output to what the software thinks it is, and honestly, I really don't care- From day 2 (day one was a nightmare :D ) I figured out that (a) I should not run my laser at higher than 26-27mA, and (b) 72% as sent to the laser to vector nailed 27mA dead on (and still does). And the down slope is fairly linear, 36% power hits around 13mA, etc., which should equate to about 40 watts, and it's output is very close to that of the 40w Synrad in my LS900...

It's my understanding that most fareast lasers act much the same way, around 70% power hits the safe mA max, and 100% is going to hit the MAX max, with mA's well into the 30's...

That, in my mind, explains the 'not go up to 100%'... :)

[Mike Thornbury]

My Triumph is 'calibrated' by mathematics ;) --

Versus mine being calibrated by tools. I guess guessing is OK for you - for me, not so much.


It's my understanding that most fareast lasers act much the same way, around 70% power hits the safe mA max, and 100% is going to hit the MAX max, with mA's well into the 30's...

That, in my mind, explains the 'not go up to 100%'... :)

Your understanding is flawed. The maximum current you can put into a Reci W6, for example, is 32mA. That is what they call the 'test current', used to calibrate the tube and to QA its maximum power for the rating sticker they put on it. At 32mA that gives you ~160W output. If you put more than 32mA in you will kill your tube in tens of hours.

If you run it at 32mA for any significant length of time, you will run it out in a thousand hours or so.

Their recommended operating current is 30mA, which gives you the power they rate the tube at for marketing purposes - 130W. You can run it at that for ~3000-6000 hours. If you mostly engrave or your cutting needs are less than maximum, you can extend the tube's life significantly by knocking a couple of mA off the maximum operating current and get up to 8,000-10,000 hours operation. For a tube that costs ~$1000, 8000 hours+ operating at ~120W is pretty damned good value for money. At the far end of that period, expect to still be getting 85% of the rated output.

All laser tube makers make tubes and rate them at X power for Y mA input. The '70%' BS has infected the industry from those hundreds of thousands of 'K40' analog-controlled rubber-stamp engravers that have been adopted wholesale by hobbyists and forced to do things well outside their design specification.

Laser power supply manufacturers make PSU's and give them a range of output, adjustable via a potentiometer. Through the use of accurate tools, you set the peak output of the PSU to match your desired tube current. It's not rocket science. It's as complicated as when I set the motor speed on my wife's 30 year old sewing machine.

If you don't match one to the other, then I guess you have to use 'mathematics' to guess at your settings. I prefer the use of a calibrated laser power meter and an accurate RMS Multimeter.

If you use accurate tools to calibrate your tube, you never have to do guess and can safely and reliably use the full range of your tube's output, as well as the full range of power steps from 0-255 to fine-tune your output.

Disparaging those manufacturers that strive to create better products for us to use because you can't or won't be bothered calibrating the equipment you have is, I find, borderline ignorant.

[Kev Williams]

Micro-measuring the power output of a Chinese glass laser whose output changes significantly with cooling water temperature changes is beyond overkill in MY real world. It is absolutely not necessary in the least that I know the exact power output of my supposedly 80w RECI at XX.XX mA... What IS necessary to me is to get the freakin' work out the door so I can get to bed before 3:30am. I've been running C02 lasers since 2001 and fibers for 3-1/2 years. I've never had to replace a single C02 tube or fiber source yet.

[Ian Stewart-Koster]

Thanks for bringing this thread back to life!
The big new 2 head, 2 tube machine has been extremely useful.
Going by a tube current max of 24mA, the w2 tube (100w) fires as low as 5%, and maxes at 100%, on 24mA.
The w8 tube fires at as low as 6% power, and maxes on 24mA at 50% power.
So those are the limits I have set in vendor settings.
Calibrating different substrates took time, for best look versus optimal time, especially in 6 to 8 hour job runs.
(Thanks Kev for waking me up to doing some engraves as vectors instead of as rasters)

The other two machines hardly get much use, but every now and then they earn their keep, or I have all 3 running at once, from 3 different PCs !