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Comparison of primary metal cutting processes
Tesko Laser Division was formed in 1995 to handle the high
tolerance metal cutting that can be achieved using lasers. Depending
on the individual needs of a customer, many different metal
cutting technologies have been required. We operate a number
of Mitsubishi lasers for customer and internal metal cutting,
but certain jobs may require other metal cutting systems. Each
of the major metal cutting systems has inherent advantages and
disadvantages.
Cutting metal is a complex and lengthy task, particularly when
the metal cutting job calls for a tight tolerance or an odd
shape that can’t be cut using traditional sawing. Then,
metal processors or fabricators like Tesko select from four
cutting systems. There is a fifth system that combines laser
cutting and water jet cutting, but we will not describe this
hybrid system. The primary metal cutting systems include:
Laser cutting process
Description
Laser cutting systems have long had the reputation of cutting
component parts with less than a 0.005" tolerance. In gas lasers,
CO2 is mixed with other gases, helium and nitrogen,
to form a lasing medium. Yttrium-aluminum-garnet
(YAG) crystals containing neodymium ions are used as the
lasing medium in solid-state lasers.
Read about the benefits of
the laser cutting process.
Advantages of laser cutting
Lasers cutting is the best metal cutting system if producing
a precise cut and creating the narrowest heat-affected
zone are major concerns. Laser cutting systems can one-inch
thick carbon materials and up to a half-inch thick specialty
metals. Laser cutting systems typically use less consumables
plasma or oxyfuel cutting systems. Precision capabilities continue
to improve.
Disadvantages of laser cutting
Laser systems typically have a higher capital cost than plasma,
oxyfuel, and waterjet systems. They are not normally capable
of cutting material thicker than 0.5 inches and have difficulty
cutting reflective metals like aluminum and copper, where a
major portion of the laser energy can be reflected away form
the cut.
Oxyfuel (flame) cutting process
Description
Previously, metal processors like Tesko only used oxyfuel for
cutting carbon steel. Today, oxyfuel technology is still the
principal process for cutting metal plate for most metal processors.
This process uses gases, acetylene, and oxygen to produce a
controlled flame.
This process is an excellent choice for end-users requiring
inexpensive cutting through carbon steel and most alloys. Oxyfuel
cutting is easily capable of producing near-net shapes. But,
oxyfuel cutting creates a heat-affected
zone (HAZ) around the cut that must be removed by additional
machining. It is possible to remove the HAZ through an annealing
process after the cutting is finished.
Read details about the oxyfuel/flame
cutting process.
Advantages of Cutting Using Oxyfuel
Oxyfuel cutting employs multiple-torch capability that is advantageous
in high production runs. Oxyfuel cutting is an excellent choice
for metal cutting that will be followed by machining activities
since it often requires secondary operations to produce a satisfactory
finished product.
Disdvantages of Cutting Using Oxyfuel
Oxyfuel cutting is slower than the other cutting systems and
materials cut by oxyfuel are easy to spot since they display
a large heat-affected zone. When a processor is looking to be
able to hold tight tolerances on the cut, they will more likely
select plasma, water jet, or the laser cutting processes over
oxyfuel cutting. Oxyfuel cutting is just not capable of holding
the tight tolerances other metal cutting processes can.
Plasma arc cutting process
Description
Plasma arc cutting (PAC) may be the favored cutting technology
for many metal processors, fabricators, service centers, and
toll processors. However, historically, plasma cutting was considered
to be a low cost, low tolerance cutting process. Plasma arc
cutting uses a high-speed electrically charged gas jet to cut
the metal. Plasma cutting is often performed at extremely high
temperatures, sometimes reaching 50,000° Fahrenheit. Currently,
PAC is capable of cutting metal plate up to 6.0" thick.
Plasma arc cutting system components routinely include a cutting
torch, a DC power supply, a cutting gas supply, a control system,
a coolant system (usually water or air) for the torch and torch
parts, and leads that connect the torch, power, gas, and coolant
with each other.
A variation, water-shielded PAC, costs less to operate since water
is cheaper than gas. Water shielding has a number of advantages.
It reduces both top-edge material rounding and the amount of irritating
smoke and fumes generated when cutting without the water.
There is an elevated level of interest in high-tolerance PAC, sometimes
also known as high-definition or fine-plasma cutting. High-tolerance
PAC can be used to cut metals from ~0.035" to 0.375" thick.
Some process users are reporting that high-tolerance plasma
arc cutting produces a cut quality rivaling that of laser cutting
and that it can be produced with less cost. Long-term use will
bear out or refute these claims.
Read details about the plasma
arc cutting process.
Advantages of plasma cutting
Plasma cutting is faster than oxyfuel cutting and is capable
of cutting thicker materials. If cost is a key consideration,
it is typically less costly than both than the laser and water
jet cutting processes.
Plasma cutting systems using nitrogen can easily cut stainless
steel, aluminum, and nickel. Systems using oxygen are more appropriately
used to cut carbon products.
Disadvantages of plasma cutting
Plasma cutting creates a large heat-affected zone in the area
surrounding the cut. Cutting materials under-water cutting minimizes
the size of the heat-affected zone. Dross,
the resolidified metal that forms at the bottom of the cut,
is a potential issue for processors using plasma cutting since
it frequently forms during plasma cutting.
Abrasive water jet cutting process
Description
Water jet cutting machines pressurize a stream of water up
to 60,000 pounds per square inch. This makes the water strong
enough to cut many metals. Abrasive water jet systems introduce
an abrasive, usually garnet, into the water stream as it leaves
the nozzle. Combining the high-pressure water with the abrasive
produces a stream that can cut more materials than the plain
water jet without the abrasive additive. Manufacturers often
develop water jets with the head submerged in a water table
to reduce the noise produced by this process.
Read details about the
water jet cutting process.
Advantages of water jet cutting
Water jet cutting systems cost less than laser cutting machines.
Additionally, water jet cutting produces little heat-affected
zone reducing the need for some secondary finishing. They are
well suited for high-performance metals.
Disadvantages of water jet cutting
Water jet technology cuts slower than both plasma and oxyfuel
cutting processes, reducing material processing productivity.
Additionally, water jet technology has a higher entry cost than
plasma or oxyfuel cutting machines.
Deciding which metal-cutting system is best
There are so many variables to be considered when making a
decision on the right cutting system to use, it is often a difficult
analysis. The metal processor and, to some degree the end-user
of the material, must consider at least some of the following
issues:
- Cutting speed
- Edge cleanliness
- Degree of tolerance required
- Number and types of metal to be cut
- Capital investment
- Operating costs
- Size of heat affected zone
- Access to secondary machining processes
There is no one overall answer to the question “Which metal
cutting system is best?" The factors that are important to
one metal processor will be different from those of another depending
on their customers’ needs. The “best" metal cutting
process depends on the material to be cut and the final application
of the material. No one cutting system is superior to another in
all major comparison categories.
If you would like more information about our laser cutting services,
please use our contact form or email
us at info@teskolaser.com.
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