Laser cut steel.

Now they have lasers powerful enough to cut steel? Well now.
So what are the specs? How thick and how fast does it work? And how clean? I’ve heard guys say “Laser Cut Steel”, as though it was something really special.

I didn’t find a lot on such cutters. I can’t see why thickness should be a problem. You can always makes several passes just like any other cutting tool.

There might be a problem with thick slabs of things like copper that can conduct the heat away rapidly. The machine works by either melting or vaporising the metal in a localized spot.

My son-in-law had a broken off stud removed from and engine block and it was done with a laser. Beautiful job. Looked just like a new thread.

Laser cut steel is pretty common now in architectural applications to make decorative panels for handrails, gates, etc. The steel plate used is commonly about 1/8" thick. I think water-jet cutting is used for thinner sheet metal.

Laser cut steel
Steel break mirror
Mirror reflect laser

Has there been some sort of story about his recently? Because there have been metal-cutting lasers around for decades now. a spin-off from the Avco Everett Research Labs that made carbon dioxide lasers for metal cutting has already had time to have a career and go out of business.

Not a story, really. I heard a guy mention it about some sort of structural piece today on one of those “home” shows.
I’ve been away fron the construction game for over 20 years. Way too much hard work in that game. :wink:
So, no chopping up I-Beams, huh?

You could chop up I beams. It would require extensive jigs and fixtures to hold the beam in place so the laser could cut it but diamond or tungston carbide saws are cheaper. Laser cutters are most useful in the computer controlled cutting of intricate parts from sheet.

I’m not sure how long laser cutting tools have been readily available in commerical manufacturing, but it goes back to at least the mid-Eighties. Before that, plasma cutting torches were used; however, the problem with plasma is that it leaves a kerf (a slight bevel on the edge) and the amount of excess heat tends to degrade material properties. On older torches, it would also leave a rough edge, even on sheet metal, but newer technology has reduced that somewhat. You also have to leave a spot on the base material to start a cut for the plasma jet to bore through before starting its cutting path.

Laser cutting, on the other hand, leaves a pretty clean edge–you can definitely tell the difference between a piece that is laser cut and one that was cut on a plasma table–and because the energy is much more finely directed it creates a much smaller heating zone, so it is more appropriate to thinner materials. This is good, because it’s not a good process on thick materials; 0.38" is about as thick as I’ve seen them go where I’ve worked, but there are some that’ll cut 0.75" or deeper at maximum. David Simmons, I suppose you could make multiple passes but I’ve never seen it done in practice, though I have seen laser output varied in speed and pulse modulation to create relief surfaces for appearance. Part of the problem with deep cuts on thicker material is that there is a lot of mass to absorb the heat and the cut then isn’t as clean. Generally, once you get past a certain thickness it’s just not worth the time it takes for the laser to cut at reduced speed. (Again, in my experience the MEs don’t like to go past 0.25" and anything above 0.38" they’ll shift to a plasma table)

Why use a laser or plasma torch instead of a saw, a shear, or a water jet (collectively called “cold cutting”)? Saw cuts and water jets are pretty clean cuts, but create a lot of waste–at least a much as the thickness of the saw or jet plus however much it varies in rotation. Water jets are also very messy, and if used to cut precious or toxic metals the residue has to be collected and filtered/reduced. Shears are essentially lossless, if you don’t mind the fact that your material is distorted at the cut line. Shears and circular saws cut straight edges, you can cut more elaborate shapes with continuous band saw, but you’re still limited in turn radius by the depth of the band.

Plasma cutters, and to an even greater degree laser cutters, allow you to make almost any flat shape you can imagine, and the manufacturing engineer or CNC technician can nest these as closely on a plate as the cut groove will allow, permitting you to make a batch of parts with minimum setup time and scrap. “Laser cut steel” is nothing all that special; you can call up Ryerson and have them burn you sillouette targets out of 0.25" steel for a few nickels a pound on top of what they’ll charge you for the material. I don’t know what they charge now, but waybackwhen when I worked in a manufacturing environment I recall the cost being about US$0.10/lin. ft. plus some nominal setup charge, which made it about 1/3 the price of having something cut on our own manufacturing floor even with delivery costs factored in.


Thamks, Stranger.
Isn’t a plasma cutter the one that makes a loud roar? I remember hearing that sound when working in refineries around Bakersfield. I was an electrician.

The kerf of a water jet is around .04", give or take some, depending on the age of the orifice. Is a laser kerf that much skinnier?

I’ve seen water jets cutting 2" and beyond, (Flow claims some people have been able to cut as thick as 15" but 8" is a typical maximum) and also having little trouble with thin stock.

It sounds like laser cutting has a fairly narrow niche of usefulness - under about a third of an inch that you don’t want to get wet.

Depending on your material and thickness, the groove width on a laser is around 0.01". I’m not sure what the kerf angle is–that probably depends on the intensity and spectrum of the laser–but it isn’t nearly as much as a plasma cutter. You can typically take a small laser cut plate and stand it on edge without having to balance it.

I don’t have any experience with water jet, so I can’t really speak to it beyond generalities. At the manufacturing facilities I’ve worked at, laser and plasma were the dominant methods of cutting flat plate, with laser being preferred for its consistancy and low tolerances. I’ve only rarely dealt with flat plate in thicknesses greater than 2"–any thicker and the part is either laminated (in the case of counterweights), cast, or assembled together as a weldment to remove excess weight where structure is not needed.

I’m a structural analyst and design engineer so my experience, such as it is, comes from what I’ve been told by manufacturing engineers. This comes typically in the guise of why my genius design is totally unmanufacturable; curiously, we generally come to a compromise which is suspiciously similar to what was initially presented with mild adjustments in tolerances. (I suspect much of this has to do with MEs exterting their perrogatives, but no doubt they’ve said the same about me.)

mangeorge, plasma cutters do make quite a bit of noise, but not nearly as much as a large brake press or millwrights on a coffee break.


I had looked into doing water cutting work when I was looking for a business to get into. One thing to remember in laser vs water cuts is also that because lasers heat the workpiece thay tend to anneal metals along the cut line, water jets do not. They can also be used to cut very heat resistant materials like ceramics and mixed with abrasives like garnet to cut even tougher materials. IIRC many tank armors are cut that way.

Laser cutting (and welding, for that matter) are routine industrial processes when it comes to sheet metal.

Regarding reflectivity, that depends on the color of your laser, but for practical purposes it wouldn’t matter if you had a mirror. It gets so hot so fast that the reflective surface is gone before you can think about it. From the laser safety standpoint, though, you still have to worry about reflected and other radiation sources.

Laser cutting is also how they make stents.

Slight deviation, but since it came up…

In the late eighties I had a job for a few months waterjet cutting. At the time waterjet could produce a cleaner cut than laser in metals, but I know that has changed since.

We routinely cut steel up to 12mm and could go a lot thicker. We did a bit of experimenting. Biggest cuts I saw done were 40mm titanium, 75mm mild steel, 110mm aluminium, 100mm concrete, 15mm dense rubber with steel embedded.

Difficulties with cutting thick materials is that the jet would lag – curving backwards in direction opposite to travel. This meant flaring at corners and loss of dimensional tolerance. Usually we cut at much lower speeds than maximum possible in order to keep to tolerances.

Waterjet is very fine at speeds of around Mach2, however water alone is limited to relatively soft materials. For steel a garnet sand is added to the jet. The resultant cut is around 0.2mm. The noise for this kind of cutting is pretty horrific.

Cutting was good for brittle materials, but you did need to either start at an edge or penetrate at low pressure well away from the required start point in order to allow for some cracking when initial hole is penetrated.

Operating pressure was 50 000 psi and the water was compressed 12% at that pressure.

Reading this thread makes me want to say…
“Do you expect me to talk, Goldfinger?”

When they started making that movie they didn’t have a laser that would dpo that. And a laser is a pretty stiupid way to cut polished gold (In the book, it’s a saw). The movie laser is pretty clearly a scaled-up Ruby Laser, right down to the spiral flashtube and red color.

They added a whipcrack sound and a background “whirr”, because, you know, these things can’t be silent. Even the Enterprise, in airless space, goes “Whoosh”.

The lack of laser speckle on that red beam is disturbin to laser jocks. As is the weird flame burning away the metal (A propane torch wielded from underneath, I’ll bet.)

But it served its purpose – it made things cutting edge (har!) and futuristic. And they actually did end up using that laser for a practical purpose, later.

I snipped the quote for brevity.
I want to know more about compressing water. It’s been a long time since high school physics, but one thing I took away with me is that you can’t compress water.
Could somebody please explain the above to me, or is it just a figure of speech?

Heh, I checked this thread for precisely this reference. I could have sworn I read the skinny on this once – although it might have been a commentary track or something. IIRC, it was an acetylene torch, but I could be wrong. It was definitely a torch applied underneath the slab, though.

From the wiki page:

Basically, for normal type pressures, it doesn’t compress enough to make a difference. 4000M is 400atm of pressure, or about 5880psi (400x14.7psi), with only that 1.8% decrease in volume. 2.48 miles under water is a long way to go, and only lose 1.8ml in a Liter of water. Compare that to gasses, and you see the confusion at “normal pressures.”