[rutexus]

Gentlemen,

I am slowly building my first laser machine. I want to cut thin mild steel 18 ga sheet metal for our company. I am still working on the XY table at this point, but am planning for the optics now. Someone posted that the typical gold plated Si mirrors have an 80 Watt max power rating. I wondered about that.

Three different Chinese distributors of the Reci W8 170 Watt laser tubes will sell me the laser tubes, but admit that they have no experience with specifying the optics. Neither can they specify the appropriate focal length for the lens.

Will I need to use some other type of mirrors and lenses to handle this kind of power?

Will they need to be water cooled?

Can anyone estimate the appropriate focal lens for this application?

Thanks,

Tom Eldredge

[cinematic2]

Is thnat a joke?
Who told you to use Reci to cut steel?

[Exsecratio]

Hi Tom,

a 170 watt tube is going to do a terrible job of cutting steel shim let alone 18Ga steel

Fiber would be the way to go possibly but that gets expensive.
You would do better to get a real metal cutting laser from Mazak or suchlike, expensive but at least they cut properly.

best wishes

Dave

[Melody-gweike]

Hi, Tom,

It is possible but it has high demand for setting up skill and machine parts.

We have a similar machine as what you are buiding for cutting metal. But only for within 1.5-2 mm thick steel and stainless steel. If you want to cut metal, your machines must reach following demands:

1. high power steady Co2 tube
2. Servo Motor and Ball Screw to get higher cutting ability
3. Very good quality mirriors and lens. And they need water cooled.
4. With the help of Oxygen
5. The beam alignment must be very accuracte
6. Focial length, common 63.5 is OK.


------
Melody
[email protected] [email protected]
skype: melody.gweike

[Exsecratio]

I'm not a fan of budget Oxygen assisted lasers at all if you don't have your game face on and something goes wrong they can relocate your building and anybody in it.

It's one area of the laser cutting industry where saving money can genuinely cost lives.

best wishes

Dave

[rutexus]

Hi Dave,

I appreciate your comments. Could you be more specific on the issues that one needs to be careful with in using oxygen as an assist.

We do not plan to do this on a production basis, only a job here and there. As it seems to me, some of the O2 would be burned, and some would not. If the machine has a strong forced air draft above and below the sheet metal it seems that the little bit of O2 that would remain would be pretty well diluted. What other concerns are there. I'm not tying to be smart in this response. I really want to know.

Tom

[rutexus]

[QUOTE=Melody-gweike;1230776]"
Hi, Tom,
It is possible but it has high demand for setting up skill and machine parts."

Hi Melody,

Thank you for your thoughtful response. I would like to ask you some more specific details, that others might also want to know.

The price of Fiber laser is out of the question. Kern Laser, in the USA, sells a 150 watt CO2 machine that cuts 18 guage steel sheet metal. I figured I could maybe get it done with the 170 Watt Reci tubes. Kern uses a metal laser tube. I have asked a couple of people what is the real truth behind the "metal/glass laser tube debate" and sometimes they chuckle first, then they seem to indicate that it is mostly hype. I don't really know. The price of a metal CO2 will also probably knock out this idea for the present time, so I want to hear what Melody says about that.

Melody, does the machine that you make and you refer to have a metal laser tube? Does the Reci W8 tube not have a "stable" enough output to do this?

I am using belt drive, with servo motors and a 10:1 gear reducer on each servo motor, so I am thinking that my motion should be smooth enough for laser cutting steel, and I do not need the torque supplied by ball screws. Please comment.

Can your company supply appropriate mirrors and lenses, and do you water cool them with coolers mounted on the back side of the mirror?

How about the lens? Does it need to be water cooled? Are there fixtures available to hold the lens and sufficiently cool it too? Can your company supply them?

I am hoping that I can use care and align the optics. I have been looking at tips supplied by various users on You tubes to see different methods of aligning them.

I have a capacitive torch height control that I can use to keep the proper distance of the laser head from the sheet metal.

I have asked Dave, who commented that Oxygen assisted cutting laser is dangerous to please provide more details of how to insure safety.

I have posted my request on Alibaba for suppliers of lenses and mirrors for this application, and received a number of responses, but I do not know who to trust, as they just say they can supply them and give me a price. I want to be a more informed buyer than this.

The fact that Melody has provided this much detail makes me more interested in looking to them as the supplier of choice, so I hope to hear more from her.

Actually, I am planning to build my machine with two laser heads: both an 80 watt laser tube for engraving and cutting acrylic and thin wood, and the same xy table and a different set of optics and laser tube to do the sheet metal cutting and the higher power coming to the laser head from the opposite direction. For the sheet metal cutting I would use Mach3 or Mach4 (we are an OEM and Mach4 will be available very soon.) For the engraver, we will probably use one of the aftermarket raster circuit boards referred to in other parts of this forum.

I would think others would be interested in cutting steel sheet metal, so I hope to hear more from Melody.

[cinematic2]

"Metal" lasers are RF excited.
"Glass" lasers are DC excited.
Difference is like a pony and horse.

[Exsecratio]

RF excited laser beams are polarised, DC excited are not.

RF can hold TEM00 modes while DC rarely do.

RF sources run from around 24 volts, DC run up to 40,000 volts.

RF are usually air cooled, DC are usually water cooled.

RF have to be re-gassed every two years or so, DC are usually just thrown away and replaced.

Re-gassing an RF tube could cost up to $3,500, around twice the price of a 150Watt DC tube costs to buy complete.

In the real world the differences aren't really that noticeable, a Chinese tube running RF isn't really a great deal different from say an Epilog running an RF tube.

Best wishes

Dave

[Exsecratio]

Oxygen:

Lasers in the low power classes (150 to 240 watts) basically heat the metal to red / white heat then rely on the injection of Oxygen to cause an exothermic reaction. The metal is oxidised and blown away by the gas jet itself ergo the metal is cut

Oxygen itself isn't actually flammable, what it does do (very well) is supports combustion and increases fire / flame temperatures, there are also some hazards when working with Oxygen bottles / gas. If combined with mineral oils Oxygen can cause the oil to combust without warning and while there is little chance of the "flame" getting back into the tank it can run up the gas line using the rubber in the line as fuel if a blowback arrestor is not fitted. Extinguishing an oxygen fire is bloody hard, it burns at such a heat water is a waste of time. (OxyAccet torches burn underwater) so your fire suppression has to be first line stuff and not just a crappy bottle hung on the wall.

The biggest concern I have is quality control, while I am an outspoken advocate of Chinese machines their quality control can be a little suspect at times (machine do arrive not working on occasion) so when a potentially deadly combination of a high pressure explosive support gas is introduced into something build on a budget then shipped overseas it leaves me with quite a few concerns.

I've only ever been party to one Oxygen bottle explosion, it levelled the building (both floors) and killed 3 people. I used Oxy assist in both my bigger metal cutting machines but both were in the £250,000 ($400,000) and made to a standard and not a budget.

A sobering example is the deaths of Roger Chaffe, Chris White and Virgil (Gus) Grissom in Apollo 1's launch pad fire Jan 27th, 1967. That was an Oxygen assisted fire

Parts wise there is nothing in an Oxy supported low power laser that isn't in the non Oxy versions really, all the action is taking part at the cut point and the delivery method for the actual beam is no different. It's just making sure the gas arrives safely really

best wishes

Dave

[Exsecratio]

Hiya Tom,

The fact that Melody has provided this much detail makes me more interested in looking to them as the supplier of choice

I'm a huge fan of G Weike, their support is legendary and the level of after sales is second to none (even compared to many in my own country) The ladies that post here are some of the most helpful both on and off the forums I have come across in any industry. The machines I've seen and played with are excellent quality and very well made.

I still would never consider buying a budget Oxygen assisted laser from ANY Chinese company.

best wishes

Dave

[cinematic2]

[quote=Exsecratio;1231478]RF excited laser beams are polarised, DC excited are not.

RF excited laser beams are Linear Polarized or Random Polarised (not polarised)

Chinese DC excited are not

RF can hold TEM00 modes while DC rarely do.

RF can hold NEAR TEM00 modes

Well done DC keeps REAL TEM00

RF are usually air cooled, DC are usually water cooled.

RF are usually air cooled up to 30W

DC are water cooled.

RF have to be re-gassed every two years or so, DC are usually just thrown away and replaced.

RF have to be re-gassed every two years = FALSE

DC are usually just thrown away and replaced = TRUE

Re-gassing an RF tube could cost up to $3,500 ????, around twice the price of a 150Watt DC tube costs to buy complete.

In the real world the differences aren't really that noticeable, a Chinese tube running RF isn't really a great deal different from say an Epilog running an RF tube.

We are not talking about 30-50W lasers. Tom wants to cut steel with RECI.
This is not real world.

/quote]


Best wishes

[rutexus]

RF excited laser beams are polarised, DC excited are not.
......
In the real world the differences aren't really that noticeable, a Chinese tube running RF isn't really a great deal different from say an Epilog running an RF tube.

Best wishes

Dave

Thanks, Dave.

I did a little reading about the transverse modes (TM00). I have a lot to learn. Considering this, I guess you are suggesting that since the DC excited Reci glass laser tubes are not polarized, and they don't get this nice round focus, they are not able to transfer enough of their power to one spot, and cut the steel cleanly.

However, I don't mind the high voltage if it gets the job done. Water cooled does not bother me either. What bothers me is the high cost of the RF tubes and power supplies!

The Reci W8 tube is relatively new. I was assuming (or hoping) that people were not using them in this application because of this.

Someone asked, "Who told you a Reci W8 could cut sheet metal 1.2 mm thick? A sales rep from the Reci company told me this. However, he declined to offer me any advice on the optics required.

Tom

[rutexus]

Hi Dave,

Of course we have used Oxy-acetelene for cutting and many other fab shop uses in our shop for years, loosening bearings, cutting off bolts etc. I believe our equipment is equipped with a blow back protection device, but the standard warning is to turn off the oxygen first, if I recall. If blowback is the main concern, I think we can cover that. I'll look into this. Thanks for clarifying.

Tom

[Exsecratio]

Hiya Tom,

Sort of, while the beam quality of an RF unit is better it's not really too much of an issue and can be made up for by brute power, (a 150 RF or a 180 DC).
For fine decorative cutting on say paper or crafting stuff then RF is noticeably better but when you are just trying to blow through metal the Transverse Mode doesn't make any real world difference.

It's like comparing DeWalt power drivers to Walmarts own, they both get the job done but one looks better doing it, is a little more reliable but costs a boat load more

I had an RF unit in the past and all the claims you hear about "Greater reliability" and "Lasts 30,000 hours" are just that.....claims.... I've seen RF gennys go tilt in 500 hours and DC tubes of the std type last 5,000 hours but as a rule RF do last longer.

Another make to look at is Bejing EFR tubes, I'm hearing a LOT of good things about them of late for both TEM modes, reliability and power delivery. Cost wise they seem to be a little lower than RECI and use US made optics (II-VI Infrared) and German glassware. I should have a 120 watt EFR to test this week so will pass back anything I find out

This was a few words I wrote up a while ago on tubes in general.

There is also a few words on RF VS DC Here

Same section there are bits about DOF (Depth Of Field) and PD (Power Density)

Hope that helps

best wishes

Dave

[rutexus]

We are not talking about 30-50W lasers. Tom wants to cut steel with RECI.
This is not real world.

Sir,

Yes, I am not talking about 30-50 watt lasers.

I guess you are saying that thinking of doing this with even a 170 watt laser is still not the "real world."

I humbly ask, how do you think Kern laser is able to do this with 150 watts and not Reci, when Reci says they can? Melody says they can too? I'm not being a smart alec in asking this. I am truly puzzled.

Thank you all for contributing. I hope I am not just one of those suckers that has to learn the hard way. That's why before I put my money down on the table I decided to post my questions here. The people who sell this stuff tend to not be as forthright as I'd like.

Thanks again,

Tom

[Exsecratio]

Hi Dave,

Of course we have used Oxy-acetelene for cutting and many other fab shop uses in our shop for years, loosening bearings, cutting off bolts etc. I believe our equipment is equipped with a blow back protection device, but the standard warning is to turn off the oxygen first, if I recall. If blowback is the main concern, I think we can cover that. I'll look into this. Thanks for clarifying.

Tom

I figured you probably knew your stuff Tom but I don't tend to assume when anything dangerous is involved The fact you are building a machine tells me you know what your doing

best wishes

Dave

[Exsecratio]

Hiya Tom,

how do you think Kern laser is able to do this with 150 watts and not Reci,

The flashout suggests the presence of Oxygen, without Oxygen no 150 watt source is going to cut 22 gauge like the video I just watched. It also looks to have adaptive optics, that's also a huge plus point.

Oxygen injection really does make a MASSIVE difference, especially on carbon steels.

best wishes

Dave

[cinematic2]

:bat:

I humbly ask, how do you think Kern laser is able to do this with 150 watts

That is simple.
Just ask Kern what exactly laser source they install (chair)

And why its not Reci

We say in Poland: Do not wipe your ass with the glass.
That means; Every work need appropriate tool.
Not cheapest.
You are trying to wipe with glass.

.

[Exsecratio]

From Kerns pages:

By using oxygen assist gas the 150 watt laser will cut up to .090" mild steel and .075" stainless steel. The 400 watt laser will cut up to .1875" mild steel, .125" stainless steel, .060" aluminum and .040" brass. The 400W laser is also capable of using a nitrogen assist gas to cut up to .080" stainless steel with a shiny and dross free cut. Other metals such as brass, titanium and nickel can be processed. However, we ask that you send in these metals to determine the machines capabilities.

best wishes

Dave