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Punch It...Laser Cut
It...Or Something Else?
by Andrew McCarlie,
Applications Engineer
 Which
machine type – a punch press, a laser cutting machine, or a
machine with dual capabilities – is best-suited to my sheet
metalworking needs? This is a major concern with every
fabricating machine purchase.
A punch press
provides the speed, but is it flexible enough? A laser provides
high-quality cuts, but will it be able to keep up with
high-volume cutting jobs that make so much sense for a punch
press? Does a punch/shear or a punch/laser machine make sense,
or would you be better off with two stand-alone machines? These
are questions that must be thoroughly researched, answered, and
tested before submitting the purchase order.
To be sure,
compounding these sometimes confusing questions is that machine
builders offer many choices, and these technology purveyors
claim to match the right machine to the right production need.
Of course,
matching technology to individual fabricating needs is never
simple. But some basic guidelines might help you decide if a
punch press, a laser, or a combination machine will be best for
working with 2-D sheet metal.
The Machine
Lineup
The machine
choices for punching or laser cutting include:
•
Turret punch press with either hydraulic or servo-electric
punching system, with up to 15 31/2-inch, full-tonnage auto
index or multiple tooling stations. The auto index feature
allows for wheel capability and multiple indexable shapes for
contouring.
•
Flying-optics laser with either AC digital servo or linear
drives.
•
Punch/shear combination machines with AC digital servo or linear
drives.
•
Laser/punch combination machines with hydraulic or
servo-electric punching systems with either AC digital servo or
linear drives.
To obtain maximum
productivity and enable you to pick the machine type that best
achieves this, you must consider all the factors involved with
the production of the sheet metal product that you want to
fabricate. Some of the factors that need to be considered are:
-
Is
the new machine a stopgap just to add more capacity?
-
Will
the decision to purchase a new machine be influenced by
operators’ comfort level with existing equipment and software?
-
Do I
want to improve the quality of my parts?
-
Will
I produce low- or high-volume parts on the new machine?
-
Am I
attempting to reduce work-in-process?
-
Am I
trying to reduce labor costs?
-
Am I
looking to combine several existing manufacturing steps into
one?
Once these
questions have been addressed and quantified, it will become
much clearer to you whether you should purchase a stand-alone
turret punch press, a stand-alone laser, a punch/shear
combination machine, or a laser/punch combination machine.
Let’s take a look
at the capabilities of each machine.
Stand-Alone
Turret Punch Press
 Today’s turret
press (see Figure 1) offers a great deal of flexibility to sheet
metal fabricators. Equipment and tooling manufacturers continue
to make tremendous strides in developing new machines and
tooling that are not only more accurate and cost-efficient, but
also capable of eliminating secondary operations while
performing functions thought impossible just a few years ago.
For example, if
you need a machine to provide fast contouring and forming in a
variety of materials-including aluminum, stainless steel,
cold-rolled steel, and Lexan® – with thicknesses from 0.016 inch
to 0.312 in., a turret punch is a good choice. Some models have
multiple full-tonnage, 3.5-in., indexable stations with a large
tool capacity, which, when combined with modern, fully guided,
high-speed tooling made of wear-resistant M2 steel, allows for
long, narrow parting tools for maximizing material use and
reducing cycle time.
If tool marks on
parts are not a concern and the parts do not have many contours,
a turret punch, coupled with efficient programming software,
often is the best, and most economical, choice. The machine’s
capability to have more than five full-tonnage, 3.5-in.,
high-speed indexing stations allows for quick setup times along
with the ability to index form tools.
When precision
forming is required, the high precision of a servo-electric
turret press is noteworthy. The precise upper and lower ram
movements help to create special flanges and forms, thus
reducing the need for secondary operations.
However,
servo-electric turret punch presses do not offer the tonnage
capacity or the speed of their hydraulic counterparts.
Modern turret
punch presses are designed to be modular and have load/unload
systems to make the machines even more efficient. They also have
special production software built into them to allow unattended
or remote production control.
Operator training
and setup skills are of low to medium complexity.
Costs of
Operation. For a hydraulic turret punch, the costs of operation
include tooling, electricity, labor, and floor space.
Maintenance typically involves oil changes, filters, and normal
wear and tear caused by tooling. For a servo-electric turret
punch, energy costs are considerably lower. No hydraulic oil
maintenance is needed, but mechanical drives and wear items
require maintenance.
Stand-Alone Laser
 A flying-optics
laser (see Figure 2) often is chosen when part quality-not
process time-is the paramount concern, along with very complex
parts with many curves and small features. Part distortion also
may be a factor when processing thick materials (greater than
0.250 in.).
Naturally, you
have to keep in mind the heat effect of the laser cutting
process, which may throw a curveball and prevent certain parts
from being processed effectively, particularly materials with
high or large thermal expansion characteristics.
Programming is
minimal because the laser is the only tool and it doesn’t
perform any forming sequences. Production software, which
enables setup of multiple jobs, is built into the machine.
Depending on part and sheet size, nesting capacity can be very
high, and sheet distortion generally is minimal.
The type and
thickness of material to be cut determine gas use.
Operator training
and setup skills required are of medium to high complexity, and
the operator does not need to perform tooling setups. Cut
quality is determined to a large degree by the operator’s skill.
Generally, every
job must be set up and tested on the laser because of material
variation. This will ensure good quality, especially when the
material type or thickness is changed.
Cutting time
depends not only on the power of the laser, but also on the X/Y
drive system stability, which allows for high accelerations.
Laser power is a factor in cutting thick materials. High-speed
axis travel is advantageous only in thin ferrous materials and
when the cutting head is traveling between cuts.
Costs of
Operation. The costs of operation for a laser include lenses;
tips; and cutting and laser gases; such as nitrogen, oxygen, and
helium, in varying grades and costs. The cost of cutting table
material supports also must be included as they are a frequent
wear item. Longer-term expenses include replacement of turbines,
resonators, and major service maintenance checks on the laser
optics. Mirror alignment also must be checked to ensure the
maintenance time is as brief as possible.
Punch/Shear
Combination
 A punch/shear
combination (see Figure 3) provides a great deal of flexibility
and considerable labor and material handling savings for today’s
sheet metal fabricators. The purpose of the punch/shear
machine’s design is to provide one machine capable of
transforming a full-sized sheet into finished parts ready for
the next operation in a single, unattended step. These parts can
be moved to final production stages for immediate integration
directly into final product assembly.
Material usage is
improved with versatile nesting programs. As loading, punching,
shearing, and unloading of individual parts become automated,
scrap and costs associated with manual labor are reduced. The
level of automation can be customized through flexible, modular
systems for raw material storage, loading, unloading, part
sorting, and stacking. These features can be added later as
budget allows and production demands increase.
If your need is
fast contouring and forming in a variety of materials –
including aluminum, stainless steel, cold-rolled steel, and
Lexan-with thicknesses from 0.016 in. to 0.250 in., the
punch/shear combination machine is a good choice. It offers
multiple full-tonnage, 3.5-in., indexable stations with a large
tool capacity, which, when combined with modern, fully guided,
high-speed M2 tooling and a right-angle shear, allows for parts
with rectangular contours up to 60 in. by 144 in. This helps to
maximize material usage (common-line shearing) and reduce cycle
time.
Tool marks on
parts are minimized where the shear is used to cut external
contours. The combination turret punch press/right-angle shear,
coupled with efficient programming software, is often the best
and most economical choice for high-volume parts. Yet the
ability of this machine to sort its parts with no tab marks or
skeletons makes it a contender for even low-volume jobs,
particularly large parts up to 0.160 in. thick.
These machines
can have more than five full-tonnage, 3.5-in., high-speed
indexing stations to allow for quick setup times along with the
ability to index form tools.
Programmable
blade-gap setting along with sheet lubrication help to extend
blade life. The machine’s flexibility allows it to be used not
only as a punch/shear, but also as a punch only or a shear only
if required. Blanks that are square to within 0.004 in. can be
produced quickly.
A large tool
capacity as well as automated production software minimize setup
time even when both the material type and thickness being queued
up are changed. Often no operator intervention is required.
Automated
programming systems allow for multiple part nesting and the
simple application of specialized tooling for upforming up to
5/8 in. high.
Costs of
operation. The costs of operation for a punch/shear combination
include electricity, tooling, and shear blades. Labor costs are
reduced because manual operations such as loading, unloading,
and scrap removal are eliminated. Floor space needed to perform
various production steps also is reduced dramatically.
Maintenance typically includes oil changes, filters, and normal
wear and tear on items caused by tooling.
Laser/Punch
Combination
 A laser/punch
combination (see Figure 4) integrates punching, forming,
tapping, and laser cutting in a single unit for varied sheet
metal working operations. Optimal use of a laser/punch machine
means that a fabricator can use the turret punch press when it
is easier or faster and the laser when it is most effective.
The latest
laser/punch technology combines the advantages of both the
modern punching machine and laser cutting. With a laser/punch
machine, complete isolation of the laser from the punch provides
for vibration-free, accurate laser cutting. As the sheet is
moved under the laser-rather than remaining stationary laser
cutting speeds tend to be slower unless higher axis drive speed
options, such as linear drives, are used.
To obtain the
greatest production efficiencies from this machine type, you
should use the turret punch press for punching, forming, and
pre-piercing holes for cutting. The laser should be used only
for cutting complex contour parts that require minimal marking
or distortion or for low-run jobs for which tooling is not yet
available, such as in prototype development. Pre-piercing a hole
with a turret punch press eliminates the splatter and sparking
that are typical when piercing with a laser. This actually
reduces part process time when this combination feature is used.
A laser/punch
combination machine can load material automatically and sort
finished parts with a minimum of operator intervention.
Production
control software built into the machine controls allows for
remote setup of work in queues. The programming software allows
for multiple part nests on large sheets and supports the use of
special form tooling.
Costs of
Operation. The costs of operation of a laser/punch machine
include tooling, high electricity use (because the laser must be
kept live even when not cutting), labor, floor space, lenses,
tips, and cutting and laser gases in varying grades and costs.
Long-term expenses include replacement of turbines and
resonators and longer term service checks on the laser (for
example, a 15,000-hour maintenance check).
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710
Remington Road 
Volume
15 Issue 1 -
July 2005