Clamshell safety and markets.

1. Clamshell Diecutting
ROBERT WEIDHAAS, JR. AND The clamshell diecutting press arguably has its
NICHOLAS CRABTREE OF MY roots in the corrugated industry and was once
considered the workhouse of most sheet plants.
PRESS NEEDS EXPLORE THE The challenge initially for most sheet plants was
LOVE-HATE RELATIONSHIP keeping up with the volume of production. The
BETWEEN THE CORRUGATED clamshell was, let’s face it, considered slow and
labor intensive. The solution was the automatic
SHEET PLANT AND THE
high-speed diecutter. As a result, many thought
CLAMSHELL DIECUTTING PRESS. the days of the clamshell were over.
Today, the long runs are not as plentiful and
REBIRTH OF THE the focus is shifting to quick turnaround, which
is to get the corrugated board diecut, off press,
and out the door as quickly as possible. Despite
CLAMSHELL the notion that the clamshell’s days are over,
they remain in many sheet plants and are in fact
contributing to productive diecutting more now
46 Corrugated Today May/June 2012

2. Clamshell Diecutting
than even just a few years ago. prevents press action if the
Why? Because the clamshell operator is in the hazard area.
press remains the most The scanner is particularly
efficient and profitable short important on “jumbo” clamshell
run solution for today’s sheet presses, such as a 60- x 120-inch
plant. because the operator may not
be able to reach a traditional
mechanical safety device if he or
What About Safety? she is adjusting the die in the
If this is the case, why then do press. The scanner protects the
some companies want to operator like no other safety
eliminate their clamshell device or technology, making
presses in favor of less efficient the press extremely safe to
systems, such as roller presses operate while not interfering
and the like? One word: Safety. with productivity.
The clamshell has a stigma of not being ABOVE:
THE CREST
a safe press to operate. Let’s be honest.
CLAMSHELL Expanding into
Many of the old clamshell presses, namely DIECUTTER
those manufactured in the 1940s, had WITH THE
P-O-P
AUTOMATED
limited or no safety devices. In the 1950s With larger and safer
SHEET FEED
and 1960s, however, air clutches were AND DELIVERY clamshell presses many
introduced along with improved safety STACKING sheet plants are
SYSTEM..
guards. Today’s presses, on the other hand, diversifying into the
RIGHT: THE
feature additional safety circuitry and ANSI SAFETY growing point-of-purchase
devices that quickly and safely stop the REQUIREMENTS markets. In fact, over the
FOR GRAPHIC
press action. last several years, the large
TECHNOLOGY
Interestingly, the automobile has a very EQUIPMENT format market exploded
similar past. Early models were often AND SYSTEMS in packaging, P-O-P and
STANDARD,
considered unreliable and even harmful. As SPECIFICALLY
digital print. Therefore,
with today’s presses, cars evolved to THE B65-5:2011 how does today’s P-O-P
include improved safety devices and PART 5: STAND- and corrugated sheet plant finish work
ALONE PLATEN PRESSES, IS A “HOW TO,” TO
technology, such as crumple zones and ACHIEVE OPTIMAL CLAMSHELL PRESS SAFETY.
coming off a high speed printer? What
advanced engineering to make the about the trending digital printers that run
automobile lighter and safer than the old circuitry that creates a redundancy in the sheet sizes as large as 62- x 102-inch at
heavy-gauge steel models. safety circuit, much like the redundant speeds up to 175 an hour, and gaining
Yet another example is the aircraft systems on airplanes. Today’s sheet plants speed seemingly every quarter? Initially
industry. While Wilbur and Orville Wright have access to the ANSI Safety many thought the digital diecutter (laser
achieved flight in 1903, air travel would Requirements for Graphic Technology and plotter) would meet this demand;
not have been defined as safe. Today, due Equipment and Systems Standard, however, the average digital diecutter runs
to advances in safety technology, air travel specifically the B65-5:2011 Part 5: Stand- only 15-30 sheets an hour, creating a
is indeed the safest way to travel. alone platen presses. This standard is bottleneck in this high speed, large format
Today the clamshell press is safer than essentially a “How To,” to achieve optimal production environment.
ever and offers the fastest setup times, clamshell press safety. In many instances, diecutting teams
high-tonnage, and precision registration One new technology described in the returned to traditional steel rule die
for the ever increasing demand from ANSI standard and found on the large technologies that allowed them to cut an
printed corrugated packaging. Presses, such clamshells is laser scanner technology, entire sheet with multiple parts in one
as the Crest Clamshell, have safety relay which scans the moving platen area and impression, moving away from slower
Corrugated Today May/June 2012 47

3. continued
Clamshell Diecutting
ability to handle awkward materials that
may be flimsy or warped. To coin the
phase, if it’s not broke don’t fix it; hand
feeding is fast and efficient when dealing
with today’s short runs.
Setting up the machine is also very
simple. This is because the operator has
immediate access to the entire work area:
the die, the cutting area (referred to as the
platen), the feed pile as well as the delivery
or stack pile. The operator quickly installs
the steel rule in the press either with a
chaseless die system (typically screws) or a
more automated system such as an
automatic die chase found on the Crest
Clamshell. Once the die is installed, the
operator aligns the sheet to be diecut,
mounts the register / sheet stops and
BECAUSE THE OPERATOR HAS ACCESS TO THE WORKING AREA, THE MAKEREADY AND SPOT UP begins a makeready process. Because the
PROCESS IS SIMPLE AND FAST.
operator has access to the working area
digital systems. As a result diecutting IT IS THE ABILITY TO DIECUT and many presses have hinged or
departments realized significant IN REGISTRATION THAT pneumatically actuated cutting plates, the
production gains when they installed a makeready and spot up process is simple
MAKES IT SUPERIOR TO
clamshell or flatbed diecutter, where the and fast. The operator simply adds
ALTERNATIVE TECHNOLOGIES
issue then becomes how fast can the press makeready tape to an area or two within
setup, run, and start the next job. This IN THIS SHORT RUN CLASS. the die that is not cutting and the job
environment of more jobs per shift lends meters) to 120 inches (3 meters). The moves directly into production.
itself to the clamshell diecutter. most common Crest Clamshell is the 40- x This unique access to the work area is
56-inch used in sheet plants; however, you what has some concerned with safety;
will also frequently find the Thomson 38- x however, it is this access that offers the
Productive & Versatile 54-inch and 44- x 66-inch clamshell in incredibly fast setup and operation of the
Clamshell diecutting is one of the most corrugated plants. The clamshell can cut press. This fact is why advances in safety
versatile forms of diecutting available to very thin or very thick materials to precise such as the laser are so valuable for new
any converting plant. It cuts a wide range tolerances; it is the ability to diecut in presses being installed and also for existing
of materials from warped corrugated registration that makes it superior to presses.
sheets, heavy duty grades, P-O-P displays alternative technologies in this short run Safety is not the only technological
and just about any job found within a class. improvement with today’s clamshell.
corrugated sheet plant. To give you an idea of the types of Valley Container in Bridgeport, Conn.,
With the ability to diecut, crease, and materials and products cut on these purchased the Crest Clamshell to replace
score sheets as well as emboss or machines, below is a sample list: its Thomson press. At the time, the sheet
physically imprint sheets, there is no press • Foam Core plant was looking for a quality press that
more versatile than the clamshell. Add to • Corrugated (all flutes) offered the same level of reliability but
this versatility ease of setup, high tonnage • P-O-P Displays with improved technology and setup
capabilities, and minimal operator learning • Folding Cartons times. The Crest Clamshell is known as the
curve and the clamshell stands out as a • Plastic corrugated cut and sealed “No More Make-Ready” Clamshell as a
valuable tool for today’s sheet plants. The These machines are generally hand fed for result of new technology in press design
machines range in size from 28 inches (.75 ease of operation with large sheets and the and manufacturing processes. Specifically,
48 Corrugated Today May/June 2012

4. continued
Clamshell Diecutting
the anti-deflection platen on the Crest is using heat to cut plastic is the added knife Heat can also be added under the steel
engineered using a science called finite penetration into the material and the cutting plate, which helps some materials
analysis, which measures the deflection of improved cut quality as a result. to lay flat during the cutting process.
the press at full load. From this data, it is Using heat along with a timed dwell in Cintra is a good example because it cuts
engineered using a proprietary design, the cutting action can greatly increase the without fracturing when warm.
honey-comb steel construction, and possibility of a clean cut. The dwell simply The clamshell press has been a solid
welding techniques. Valley Container means physically stopping the press on choice of diecutters for many years. It offers
purchased the press because it will set impression for a predetermined period of fast, efficient operation and versatility
up and begin production within 10 time to allow added heat transfer from the found in no other press technology. Today,
minutes. die to the material — another unique the clamshell has undergone significant
benefit with the clamshell press. This developments in engineering. Mechanical,
option can also be used to seal or fuse the electrical, operational, and safety
Automation edges of materials together; plastic engineering advances in the clamshell press
While hand feeding the clamshell is fast corrugated or plastic laminated foam core have set the stage for the rebirth of this old
and efficient, today you can have the best can now have a cleanly sealed edge. This is workhorse.
of both worlds, which is the ability to hand helpful in preventing moisture from
feed short runs and automate medium- entering the fluted edges or the softer Robert Weidhaas, Jr. is President and
long runs with one press system. For inner cores for certain indoor and outdoor Nicholas Crabtree is Vice President of
example, the Imperia and the Crest packaging applications. Technical Sales of My Press Needs LLC.
clamshell are both available with automatic Weidhaas has spent 23 years in the
sheet feed and delivery stacking systems TODAY YOU CAN HAVE converting industry with a special emphasis
— one press, two methods of operation. on clamshell press technology. He is an
THE BEST OF BOTH
active observing committee member for the
WORLDS, WHICH IS THE ANSI B65 safety standard for stand- alone
Plastic Corrugated ABILITY TO HAND FEED platen presses. Crabtree has more than 30
The clamshell diecutting presses also come SHORT RUNS AND years of converting industry experience. He
with other features that assist operators in contributes to a technical blog
AUTOMATE MEDIUM-
cutting a variety of substrates. Most www.mydiecuttingblog.com about die
clamshell manufacturers offer the option LONG RUNS WITH ONE design, applications and helping to solve
of a heated platen; this allows the back of PRESS SYSTEM. today’s diecutter challenges.
the die to be heated. By heating the die,
the heat is conducted through the steel
rule resulting in a hot knife edge to
improve the quality of the diecut. It should
be noted that when diecutting, you are
actually compressing the material under
the knife edge to the point of explosive
penetration, not actually cutting in the
true sense of the word. When cutting
plastics, the challenge is developing
enough knife penetration to prevent
cracking prior to this explosive separation.
Heat assists with penetration and thereby
improves the quality of the cut edge by
helping to reduce cracking. This process
also reduces tonnage, or the force required
to cut the plastic, but the key benefit in
50 Corrugated Today May/June 2012