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.
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.
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.
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.
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.
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).
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.
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).
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.
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.
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.
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.
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.
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)
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!
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.
