A: The lens that should be used is Ophir P/N 60616 LA. There is no need to use thicker lens since the 60616 is suitable for any pressure which can be used on the laser machine. When cutting mild steel, usualy oxygen at low pressure (< 5 bar) is used so that a lens with E.T. 3.0 mm should be sufficient.

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A: There are two different "types" of lens used in industrial laser machines: meniscus and plano-convex. The correct type is usually specified in the machine manufacturer's manual.
For a technical explanation about the differences between the two types please refer to the Duralens™ section of our catalog.
Basically, Plano-Convex lenses are usually found in workshops which cut thicker materials and are more popular in American and Japanese machinery. European customers and machine manufacturers (OEM's) traditionally use the meniscus range.

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A: Obviously the number of lenses used per year depends on the machine workload and the type of metal it is processing. Our studies show that in average, lenses are replaced 4-5 per year while mirrors are usually replaced once a year.

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A: The higher the pressure at which the machine cuts, the thicker should the lens be.
Please refer to the table showing the recommended operational pressure for each lens.

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A: No, each laser machine has its own parameters. The machines differ in laser power cut different applications depending on the application and the quality of the work piece. However, most parameters are similar for all laser machines so these values could be used as a basic guideline for other machines.

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A: When cutting mild steel thicker than 4mm it is best to use oxygen with a maximum pressure of 3.5bar. If thickness is 15mm use gas pressure of 1bar and a small nozzle (=1mm).

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A: When cutting mild steel (thickness up to 5mm) the focal position should be about 1/3 in the workpiece. When cutting thicker steel the focal point is moved up.

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A: When cutting stainless steel use nitrogen. In this case the focal position is always under the sheet surface.

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A: When cutting thin materials (less than 2mm) you can use shop air. However, shop air could be contaminated with oil and water or other impurities requiring a high level of filtering.
When cutting Aluminum, Oxygen can be used. Note: For a quality cut proceed slowly. Nitrogen can also be used for Aluminum (cut quality improves when cutting slowly).

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A: In order to check the beam quality, check the sparks under the sheet: they should follow the input laser angle to make one line. If it is lagging the focal position needs to be adjusted.
Also, pay attention to the color of the plasma in the cutting area - it should not be blue. If the plasma is blue - stop the cut and re-adjust machine constants.

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A: 7.5" length is placed far from the workpiece so there is less chance for it to damage - for a longer lifetime. However, the laser power density reaching the workpiece decreases. When cutting thin material (5mm and less) one should use 5" focal length since the spot diameter is smaller.

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A: These lenses absorb less heat and therefore their performance (i.e. focusing efficiency and lifetime) is better.
The reduced absorption in the black-coated lenses affects lens operation as follows:

1.	Thermal Lansing is reduced, and therefore the focus position during operation with a high-power-laser is more stable.
2.	Since thermal effects also increase lens aberration, increasing the spot size, the spot size of a black-coated lens during operation in a high-power-laser is smaller than the spot size of a conventional lens.Therefore when using a black-coated lens the energy concentration is higher and enables a better and faster cut using less gas.

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A: Ophir's unique product, the Black Magic Duralens lens, was created using a revolutionary black coating technology. The Black Magic lens has achieved the lowest absorption on the market - lower than 0.15%. The Black Magic lens has achieved the lowest absorption rates on the market - lower than 0.15%. The black coating is much harder, has better ability to withstand back splatter, requires less maintenance (i.e. extended lens cleaning intervals) and is RADIOACTIVE FREE.
In most applications, the Black Magic increases the cutting speed, save up to 20% of gas consumption and lasts twice the lifetime of a standard lens.
The black magic is the best solution for cutting thicker metals in high power laser cutting machines.

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A: Ophir Optronics understands that beam alignment is crucial for a clean cut. We suggest operating the laser machine leaving the gas off and turning on the focus manually. After finding the right focus the laser machine can be used regularly.

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A: No. The machine constants need to be re-adjusted in order to ensure its best results.

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A: After some experiments Ophir found that the following values for different applications increase cutting speed and extend the lifetime of the optics:
The lens used was Ophir P/N 60616LA (Diam 1.5", FL 7.5", ET 9mm)

Make	Model	Config.	Laser resonator	assist gas type	gas pressure	app.	nozzle	Nozzle standoff
Bystronic	Bystar 4025	Flying optics	Bystronic up to 4 KW	Nitrogen N2	18 bar	304 SST, 15mm	3mm	0.6mm
Bystronic	Bystar 4025	Flying optics	Bystronic up to 4 KW	Nitrogen N2	14 bar	304 SST, 15mm	2.5mm	0.6mm

	type of lens	lens diameter	Focal length	Edge Thickness	working lifetime	focal position	Dwell time	speed
Bystronic / Bystar 4025	Meniscus LA	1.5"	7.5"	9mm	5 months	17mm	3 sec	290 mm/min(was 250)
Bystronic / Bystar 4025	Meniscus LA	1.5"	7.5"	9mm	5 months	6.5mm	3 sec	2500 mm/min(was 2000)

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A: Clean the lens using a liquid soap and a soft tissue. Follow our cleaning instructions (found on our web site).

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A: Please perform the following steps:
Check lens mounting direction, realign the laser beam, check the focus spot size and check the color of the plasma (should be blue).
If the problem remains check for dust in the machine.
A final step is replacing mirrors (turning mirrors or resonator mirrors). Normally mirrors are replaced once a year - by a qualified person only!

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A: Yes. There is always a possibility that a focusing lens will explode.
Many parameters are involved in operating laser machines and some influence the performance of the optics.
Ophir optics is checked and their quality assured before shipped. Rarely do we hear about lenses that exploded in the machine. However, in about 95% of them the explosion has nothing to do with the lens itself.
The reasons could be:

	Dust that drops on the lens from the inside develops pressure on the lens and eventually breaks it.
	Wrong focusing of the beam on the workpiece might cause the reflected beam to focus on the lens and burn it or make it explode.
	Bad beam profile - instead of having TEM "0" Gaussian profile, the beam has a wrong profile (i.e. 2 narrow peaks). In this case the lens goes through thermal shocks and non-radial heat transfer causing pressure and micro cracks in the substrate and its coating.
	High assist gas pressure (no in accordance with the specifications sheet). A big nozzle exit-hole diameter (bigger than 1.5mm) might let back-spatter and other hard particles to penetrate and hit the lens, resulting in its chipping and cracking.

Ophir optics do no fall short of those of any other maker and our Black Magic lenses have even better quality (as they are hard coated and therefore more resilient).
In extreme conditions, when machines are poorly maintained and due to the fact that parameters are so sensitive and difficult to tune - optics of one maker do better than another's due to tolerances on the optics.

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