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n today’s fast-paced flexo industry, remaining competi- degree, we have been spoiled by the TIR (total indicated
I tive in terms of mechanical technology is essential for runout)/diameter tolerances that have been the norm on
survival. Recently, I attended a press trial run on a 10- high-quality integral cylinders. Poor diameter and TIR read-
color gearless machine. This was the first time the job was ings are sure to extend the time needed to get the job run-
run on this press. Once the job was in register and the col- ning, and often have your press operator wondering why the
ors matched, the press was brought up to speed (900 fpm) company invested in an automatic registration system. He or
and the first pull inspected. A particular spot color did not she is often forced to bypass the automatic system and set
lay down well, and twice an anilox-roll sleeve was changed register manually.
to achieve the desired ink laydown on a particular spot. The first concern is racking in and damaging plates and/or
The fascinating part is that from the first pull until accept- stickyback. A set of mandrel sleeves that are inconsistent in
able ink laydown was reached on this spot, 22 minutes had diameter, or that have expanded or contracted in reaction to
passed! Can you imagine the time this would have taken on heat and humidity, can give a press operator fits! There is
a conventional geared press with integral anilox rollers? reason for concern here, as the current industry trend is
Progressive pressroom toward using the gear-
managers are over the less press as not only
“efficiency high” of the printing device but
gearless machines and also as the proofing
are now starting to device!
manage the press in Ide a l l y, p o l y me r
component subsets. Of plates should be
all the gearless-press mounted to “top dead
subsets, the plate sleeve center” using a pre-
has created the most cision video-mounting
controversy. Combined, machine and delivered
servo motors and man- to the press where the
drel sleeves (sleeves uti- automatic registration
lized in gearless presses, system takes over. The
mounted directly onto job should rack in to a
the press mandrel or light kiss impression
“bridge mandrel”) are setting that is extreme-
used in mandrel sleeve manufacturing, as well as the method
the two key compo- Chemicals are critical. All photos courtesy of Converting Solutions Inc. of applying them during con- ly close to being in reg-
struction,
nents that fostered the ister. Due to the preci-
introduction of gearless technology in flexographic press- sion of servo-drive systems, minimum adjustment should be
rooms. required to have the job up and running good print with
The significant thing to understand is that servo technol- tight register. For the purpose of this article, we will omit
ogy is not new—just new to flexo. Mandrel sleeve technolo- discussion of color matching.
gy in flexo applications, however, is still in its infancy. Here The “flexo image train” greatly impacts automatic registra-
are some of the prominent sleeve learning-curve issues in tion and impression settings during job setup. It is fair in
pressrooms that have invested in one of these gearless won- rotogravure to refer to the engraved cylinder—a steel cylin-
ders. der with an external copper layer that is engraved and then
chrome plated—as the image carrier. This one-piece image
Mechanical Tolerances carrier is typically delivered at +/- 0.0005 in. in diameter tol-
Poor or inconsistent mechanical tolerances are by far the erance. Contrary to popular belief, it is not fair to refer to
biggest issue with mandrel sleeve technology. To a certain photopolymer plates as the image carrier in flexo printing on
36 FLEXO JUNE 2005 w w w . f l e x o g r a p h y. o r g
By Anthony Foley
gearless or geared presses.
Let’s focus on gearless press-
es. The printing train is your
image carrier and can consist
of either four or five compo-
nents: polymer plate, mounting Verification of finished tolerances on a mandrel sleeve The sleeves you install in the press must be dimensionally
tape, mandrel sleeve and press must be performed without human error. stable and allow the operator to set up the job in a pre-
dictable and repeatable time frame.
mandrel; or polymer plate,
mounting tape, mandrel sleeve, bridge The second issue with instability is advanced drying technology. The com-
mandrel and press mandrel. relative temperature and humidity. bination results in generation of strong
While gearless technology and digital Certain components used on sleeve sur- vapors. Even in a climate-controlled
plates have afforded us great strides in faces are hygroscopic (absorbent) in pressroom, unpredictable sleeve expan-
print quality, the expanded printing nature. This absorbency trait is more sion occurs.
train on gearless presses presents new apparent in the warmer summer Unstable sleeves contribute to
challenges. The ideal situation is con- months, when plate or tape is over- increased scrap, excessive setup times
sistent and repeatable job setup that impressed as a result of decks racked in and less machine throughput from your
ensures an accurate job-costing process automatically. gearless investment. A mandrel sleeve
and minimum scrap numbers. Poor should be delivered in an inert state
mechanical tolerances on mandrel Servo technology is not and remain that way.
sleeves used in gearless presses make
new; it has been used in
job setup unpredictable and drive up Handling & Durability
scrap numbers. various drive systems for “These *#@+*+% sleeves are too
many years. The marriage easy to damage and can’t stand up to
Sleeve Stability of servo technology with the demands of flexo printing.” Anyone
Raw materials (chemicals) used in lightweight demountable who has spent time around a gearless
manufacturing—as well as the method press has probably heard similar state-
sleeves, however,
of applying them during construction— ments from operators and helpers. My
are critical. While some chemicals in is in its infancy. take on this is: You can take the cylin-
flexo-sleeve manufacturing are less ders away from the operator, but it is
costly and are easy to apply with mini- To remedy this problem, the operator very difficult to change the operator’s
mum labor, there is a definite trade-off has no choice but to manually re-set cylinder mentality (as it relates to han-
in stability. the impression(s). This often leads to dling).
First, when a new set of sleeves exceeding the desired repeat length, Mandrel sleeves are not nearly as
arrives with a strong odor, red flags not to mention spending extra down- durable as integral cylinders; they are
should come up immediately. The dis- time manually adjusting decks. In some more vulnerable to the razor knives and
tinct odor (often referred to as sleeve cases, the plate and/or tape is so dam- cleaning solutions in all pressrooms. In
“degassing”) is the byproduct of a aged that the sleeve must be pulled addition, cylinders are almost never
chemical reaction that is still taking and the tape and/or plate replaced, handled by hand, due to their weight.
place. Such sleeves often display a poor resulting in more downtime. Use of the chain and hoist required to
affinity for stickyback in the first few Certain sleeves are susceptible to handle cylinder weight, however,
months in production. They also create expansion resulting from exposure to ensures that operators follow proce-
excessive gas bubbles between the solvent vapors generated by in- dures while jobs are staged to and from
mounting tape and sleeve surface due between-station dryers. Today’s gear- the press.
to vapors released while the sleeve is less presses run at much higher produc- One of the advantages of sleeved
degassing. tion speeds and are equipped with presses is the fact that sleeves can be
w w w . f l e x o g r a p h y. o r g JUNE 2005 FLEXO 37
handled manually, and therefore moved Operators print with lighter impres- plate cylinder is not the weak link, but
much quicker than integral cylinders. sion settings on gearless presses. Print- rather operator restrictions relating to
They are often stood on end, dropped, deck tolerances are tighter, and the installing and removing cylinders from
knocked over and generally abused as control logic has adjustment windows the press.
though they were constructed from that prevent excessive impression, or Precision mandrel sleeves combined
steel! skew. Banding is more apparent on with servo technology have changed
There are numerous opportunities for decks printing solids. It also appears the landscape in terms of flexo press-
sleeve damage to occur. Suppliers have when press speed is reduced to make a room efficiencies. Compare a flexo job
taken steps to provide the most durable splice and then is quickly ramped back changeover to the pit-stop time of a
sleeve product possible while still con- up to cruising speed. Some sleeves sophisticated race car. In both situa-
sidering manageability factors. Press actually band or skip in the transition tions, faster is better; but we must look
OEMs are engineering modifications to stage, almost as though they momen- beyond that! A race car pit stop of less
make sleeve installation more user- tarily galloped on the mandrel and then than 10 seconds is usually deemed
friendly. settled back down. exceptional. It is meaningless, howev-
I am often asked, “How much do your er, if the car is unable to function at its
sleeves weigh?” I respond that there is Get over the gearless-press- full potential once it’s back on the
a ceiling and a basement. The ceiling is efficiency high and start track. Get over the gearless-press-effi-
often dictated by your company’s safe- ciency high and start utilizing the
ty guidelines or federal standards. Some
utilizing the machine to its machine to its fullest capabilities.
sleeve suppliers who have become fullest capabilities! This past year has seen ink and sub-
obsessed with weight ignore such key strate prices rising quickly. The result is
issues as mechanical tolerances, impact A sleeve that is unstable or has printed packages sold at a lower profit
resistance and long-term stability. Any inconsistent layers of construction may margin, which equals one thing for your
new material introduced into the sleeve pass incoming quality control analysis company: fewer profits. The optimiza-
construction must be evaluated over and look fine in the mounting stage. tion of gearless technology will allow
time before being approved. When it is introduced to elevated pro- us to compete in both domestic and
The weight-to-strength ratio of duction speeds on gearless machines, global markets.
sleeves should be considered for the however, the term “beauty is only skin A range of sleeve products is avail-
safety of your operators. Recently, a deep” becomes applicable to flexo able today. Your mandrel sleeve deci-
customer had to modify the sleeve- sleeves! Unlike a steel cylinder, a sleeve sion will have a significant impact on
handling procedure for a large repeat, cannot be dynamically balanced. the speed and efficiency of your gear-
as the sleeve slightly exceeded the You must strive to optimize the less press. Practically everything can be
maximum weight limit for operator potential of the system that is before poorly made and cheaply sold. The laws
handling. For this particular repeat, the you; uptime numbers in the 80-percent of economics prohibit the acquisition
customer implemented the same proce- range are now feasible in flexo press- of high value for low capital outlay. If
dure used for installing and removing rooms. Servo technology is not new; it you accept the cheapest price, you risk
anilox sleeves. The key is knowing that has been used in various drive systems paying more than you bargained for. If
the sleeves you install in the press are for many years. The marriage of servo you can afford to do that, you can
dimensionally stable and will allow the technology with lightweight, demount- afford a high-quality product to begin
operator to set up the job in a pre- able sleeves, however, is in its infancy. with.
dictable and repeatable time frame.
Changing Landscape ABOUT THE AUTHOR:
Banding & Bounce For the most part, our press opera- Anthony Foley is presi-
A noticeable reduction in pressroom tors have been schooled in the flexo dent of Converting
noise occurs when the switch is made process using integral cylinders. These Solutions Inc. (CSI), a
to gearless technology. I have often cylinders display excellent mechanical Tampa, FL, supplier of
stood beside a gearless machine, how- tolerances, are stable and are dynami- flexo pressroom prod-
ever, and wondered what the thumping cally balanced to ensure that optimum ucts. He has been
noise was. One of the big graphic press speeds are achieved. They are involved in the flexo industry for the
advantages of moving to gearless is durable, show good resistance to sol- past 18 years. He can be reached
that the operator never again has to vents and cutting instruments, and toll-free at 888-274-9906.
deal with gear marks. A phenomenon have a predictable affinity to sticky-
referred to as “banding,” however, back. Due to their weight, they must be
occurs on many gearless presses. These handled with the assistance of a hoist.
bands look like gear marks but do not When you look at this closely, it is clear
repeat consistently (and are quieter). that in the flexo process, the integral
38 FLEXO JUNE 2005 w w w . f l e x o g r a p h y. o r g
