CMM International 2003 Conference, From Machine to Market:
Using Laser Engraving in Tissue Embossing
Laser engraving is one of the most exciting new ideas to hit the embossing scene
for the tissue industry. Although tissue producers began experimenting with the
use of laser engraved cylinders for embossing almost 20 years ago, advances in
this technology are continuing to drive new developments in tissue embossing
even today. Some of these new ideas may be applicable to other grades of
paper and board, and even to other materials.
The earliest laser engraved embossing rollers were used as research and
development tools to screen potential embossing patterns, primarily on the basis
of appearance. They were not very good models of real embossing rollers,
especially in terms of runnability and product properties, because the laser could
not reproduce the contours normally found in conventionally engraved
embossing rollers. This was called two-dimensional (2D) engraving, because it
produced extremely repeatable and accurate element placement in the two
horizontal dimensions, but much less control in the third dimension (depth).
As laser engraving machines were designed with greater control of the vertical
dimension, and engravable materials were developed that were more durable,
laser engraving became a more prominent force in tissue embossing. Today,
laser engravers use a "3D" engraving process that is much more precise. Laser
engraved rolls are being used successfully in many tissue embossing
- In the production of steel embossing rollers, where the laser engraved
rolls are used as small tooling rolls or as full-sized master rolls.
- Evaluating the performance of new embossing patterns on experimental
embossing lines. In some cases, the laser engraved surface may be part
of a removable sleeve.
- Accelerating the startup schedule of new embossing patterns in
production. These are full sized production embossing rollers with a laser
- Long-term use in production, in very rare and special cases.
There are several advantages and disadvantages of laser engraving, when
compared to conventional engraving of steel. By conventional engraving of steel,
we are including the use of computer controlled machining of steel, which is
usually only applied to the smaller cylinders used as tooling.
| Less expensive, on a per engraving basis.
|| Shorter life, requiring more frequent re-engraving.
| Faster delivery time.
|| Easily damaged – during shipping, handling, and in use.
| Higher accuracy in positioning the
pattern elements on the surface of the roller.
|| Less accurate control of depth,
sidewall shape, and curvatures ("radiusing").
| Complete digital control of the image, computer to computer,
even when engraving large rolls.
|| Easily damaged – during shipping, handling, and in use.
| The ability to use more complex patterns.
|| Poorer quality surface finish.
The Laser Engraving Process
The technology of using laser engraving in the tissue embossing industry has
been mostly an adaptation of the technology that was developed for the printing
industry. However, many advances have been made specifically for embossing.
Some of these were made by the manufacturers of the laser engraving machines
and are commercially available with the purchase of those machines. However,
the individual companies that use these lasers to engrave cylinders for
embossing have made a great number of technological advances as well. This
information is generally highly proprietary, which gives the older companies a
significant advantage over newcomers in the field.
Most lasers that have been used to engrave rollers for the tissue embossing
industry are CO2 gas lasers that generate an invisible infrared beam. The beam
is focused upon a point just below the surface of the roller to be engraved, while
the roller rotates in a lathe. In some engraving machines, the beam traverses
across the roller while the roller simply rotates. In others, the beam does not
move, and the roller travels axially while it rotates.
The very early 2D engraving process produced a "square" profile, with vertical
sidewalls and sharp corners (see Figure 1 below: "Etch Profiles for Different
Laser Engraving Technologies"). It was similar to the photo etching process, in
that it used a mask to control what areas were etched, and the resulting surface
had only two levels: either fully etched, or not etched at all. In the case of photo
etching, the mask was a thin film of polymer and an acid was used to remove
unprotected areas of a metallic substrate. With laser engraving, the mask was a
thin coating of reflective metal (usually zinc), and a steady laser beam was used
to remove unprotected areas of a polymer substrate (usually polyurethane). The
artwork provided to the engraver to specify the embossing pattern was a
two-dimensional image in just two colors: solid black or solid white (no gray). Black
was used to represent the raised areas (no etching) and white was used to
represent the areas that were to be etched away at full engraving depth. The
only engraving parameter was etching depth. In those days, image processing
was usually done photographically.
The vertical walls and sharp corners of these early laser engraved cylinders
made them unsuitable for engraving steel. In an embossing nip, the sharp
corners would initially cause excessive damage to the paper, and would then
crumble due to the very high stresses at those points.
These older engraving machines were soon replaced with lasers that rapidly
varied (modulated) the power of the beam to control etch depth, and did not
require masking the substrate. For the first time, it became possible to process
the image 100% electronically (from computer to computer), without resorting to
any physical image. This was an enhanced version of 2D engraving, with the
physical ability to create any embossing contour. However, contour engraving
requires 3D image processing, which was sold by the laser machine
manufacturers as a very expensive software option sometimes known as the
"embossing package". Also, the software, computational power, and skills
needed to create 3D artwork was not very available.
Enhanced 2D engraving used the same black-and-white 2D artwork as the old
technology did, but the laser controller on these new machines could be
instructed to create a simple linear transition between the areas that were etched
and those that were not etched. This transition appeared in the engraved
surface as a sloped section or ramp surrounding each raised area, shown in
The ability to control the sidewall angle made these laser engraved cylinders
more suitable for engraving steel. Sloped walls also added strength to the areas
that were compressed in an embossing nip, as in "rubber-to-steel" (R/S)
embossing applications, where the "steel" roller was replaced with an engraved
polymer. This extended the useful life of the laser engraved roller, enough to
make it practical in research applications, and also for some short production
The next generation of laser engraving machines was capable of what is called
three-dimensional (3D) engraving. For 3D engraving, the embossing patterns
were specified graphically as a 2D image in grayscale, which is black and white
and any shade of gray. The etch depth at each point on the surface of the roller
is controlled by the degree of grayness at the corresponding point in the image.
An image format called "8-bit grayscale" provides 256 levels of grayness,
including pure black and pure white, which corresponds to 256 different levels of
engraving depth. For most embossing patterns, this means a step size of
0.0001" to 0.0005". These steps are not detectable in the resulting laser
Materials for Laser Engraving and Embossing
The key to making laser-engraving work in the tissue embossing industry is in the
material that is used on the surface of the cylinder to be engraved. There are 3
- This material must engrave well in the laser, through a special type of
vaporization which is called "ablation". This is where the material is
ejected from the surface at high velocity, and the ejected material carries
away most of the heat energy with it.
- The material must be durable enough to withstand the pressures that the
cylinder will be subjected to, either when used to engrave steel, or when
used to emboss paper.
- The thickness of the material must be greater than the depth of the
engraving, by an amount that depends upon the embossing pattern and
upon the properties of the material. The engraving depth for R/S
embossing can sometimes exceed 0.100".
Steel certainly has the required durability. However, it is currently very difficult to
laser engrave steel cleanly at the depths required for tissue embossing. This will
change as lasers are developed with much higher power and much faster
Ceramics laser engrave well at shallow etch depths. However, when building a
layer of ceramic up to the thickness required for embossing tissue products, it
tends to crack and delaminate. It is also difficult to laser engrave ceramic cleanly
at the greater depths required for tissue embossing. Eventually, someone will
solve these problems as well.
The most successful materials that have been used for laser engraving and
embossing over the past dozen or so years have been various chemical
derivatives of natural and synthetic rubber. Some of these materials have been
unofficially known as "ebonite". Ebonite™ is a trademark currently registered to
Ebonite International, Inc. of Kentucky, and refers to the material used to make
bowling balls. Many companies are actively engaged in developing new
formulations. This is a very competitive and proprietary area.
Pattern Design with Laser Engraving
Laser engraving has opened up new possibilities in the design of embossing
patterns. Many ideas that were very expensive to implement before laser
engraving arrived are now more practical. Two of these ideas are "anti-nesting"
and "anti-ridging". Implementing either of these concepts normally involves
increasing the distance in which a pattern repeats itself in the machine direction
(MD), which increases the diameter of the smallest cylinder that can be engraved
with that pattern. This increase in size of the first tooling roll has a much greater
affect upon the cost of conventional engraving than it has upon the cost of laser
The thinking behind "anti-nesting" is that a roll of product can be made larger by
preventing adjacent layers of product wrapped within the roll from "nesting" into
each other. Nesting is when the embossments of one layer fit into the
embossments of the layer below it, much like bowls can be stacked on a shelf,
thereby taking up less space. Occupying less space is not desirable in a roll of
consumer product, where value is often judged by the consumer based upon the
size of the roll. The only exception to this is at the outside surface of the product,
where nesting would make the embossments less susceptible to damage, and
therefore more visible to the purchaser.
When pattern nesting occurs, it is usually seen in a roll of product as bands of
denser layers alternating with less dense areas (see Figure 2 above: "Bands of
Nesting and Anti-Nesting"). Each of these denser bands has a circumference
that is equal to an integer multiple of the shortest distance in which the
embossing pattern repeats itself in the machine direction. A shorter MD pattern
repeat therefore increases the number of these nesting bands that appear
between the core and the outside of the product. When the MD pattern repeat is
greater than the final circumference of the roll of product, nesting does not occur.
However, this requires that any tooling cylinder that is large enough to hold this
pattern must be greater in diameter than the roll of product.
Another idea made more practical by laser engraving is "anti-ridging". Ridging is
a phenomenon seen on the surface of some roll products, where the roll appears
to be corrugated, as with a tin can, with ridges running circumferentially around
the product roll (see Figure 3 below: "Ridging and Anti-Ridging in a Roll
Product"). This is an example of uneven bulk generation within the product,
where the higher bulk building elements of the embossing pattern tend to occur
at the same axial positions within the product, and these elements do not nest.
As the product is being wound upon the core, the diameter steadily increases,
and so does the length of paper that completely wraps around the roll.
Therefore, the relative placement of elements in the MD, or circumferential
position around the roll is constantly shifting. However, the CD or axial positions
of all of these elements remains the same. The accumulated effect of the higher
bulk building elements within the pattern is to spread this excess bulk around the
roll in the form of ridges. Similarly, areas of low bulk cause valleys between the
The solution is to spread these high and low bulk-building elements more evenly
across the embossing roller. Each pattern element should be placed on the
embossing roller so that it shares the same axial or CD position with very few
other elements. This greatly lengthens the MD pattern repeat. In the extreme
case, where each pattern element has its own unique CD position, not shared by
any other element, the MD pattern repeat is equal to the full circumference of the
embossing roller, and the pattern is called a "once-around pattern". In most
cases, the most practical way to engrave such a pattern is with a laser.
The more evenly the pattern elements are positioned across the CD of the
embossing roller, the better the results. Ideally, the spacing of these elements in
the CD would be perfectly uniform, regardless of the MD positions. For instance,
if there were a total of 1000 pattern elements engraved onto an embossing roller
with a face of 100", then there would be exactly one of those elements centered
at 0.1" from one edge of the face, another element somewhere around the roller
centered at 0.2" from that edge, another at 0.3", and so on all the way across the
roller. A non-uniform appearance can still be achieved by semi-random
placement of the elements in the MD.
Most embossing patterns are composed of repeating elements (or groups of
elements) which repeat at even spacing along straight lines in the product. In roll
products, such as bath tissue and paper towel, these straight lines are often at an
angle with respect to the MD and CD. On the engraved embossing roller, the
repeating elements follow helical paths around the roller, continuously from one
edge to the other, with no breaks in spacing or direction. When the direction and
spacing of these helical paths are selected appropriately, whether by direct
calculation or by trial and error, then the optimum uniformity of CD and/or MD
positions of the elements will be found. Avoiding alignment of elements in the
MD through uniform CD spacing will reduce ridging to imperceptible levels.
Avoiding alignment of elements in the CD through uniform MD spacing will
minimize vibration in the embossing nip.
An additional benefit of anti-ridging patterns is more uniform wear of the rubber
roll cover used in embossing. The same parts of an embossing pattern that
generate higher bulk in the product also cause greater wear in the rubber. When
many of these pattern elements align in the MD (which means that they are at
the same CD position), then the wear pattern appears as grooves in the rubber
cover. Avoiding this alignment by spreading the elements evenly in the CD
dramatically reduces this grooving, which often extends the useful life of the
R&D Embossing with Laser Engraved Cylinders
The routine use of laser engraved cylinders to emboss tissue first appeared in
the experimental or R&D facilities of tissue producers, in support of the
embossing pattern development process. Although the best results were
obtained with steel rolls engraved by the conventional process, the high cost and
long delivery times severely hampered experimentation with new pattern ideas.
In the early stages of the pattern development process, small embossed samples
are made for the purpose of screening patterns on the basis of general
appearance. Very small quantities of samples embossed with each pattern are
required, and it is practical to use photo-etched magnesium plates in a flat press
for this purpose. In the next stages of development, full size prototype rolls of
product are often needed for testing of physical properties and for customer
preference trials. These product rolls must be made in a continuous rotary
embossing nip. In the case of R/S embossing, where one roll is engraved and
the other roll is smooth rubber, laser engraving was often the most cost effective
As the price of the engraving was reduced, a larger proportion of the total cost of
a pilot embossing roller became the steel base, or the core, which was covered
with the engravable material. Although these cores were reusable almost
indefinitely, they could only be reused by destroying the engraved cover, which
many people were reluctant to do. The number of available cores soon became
a limiting factor in the number of embossing patterns which could be kept in
inventory. Also, the time that it took to manufacture a new core often introduced
significant delays in the delivery of a new embossing roller.
The next advance was the use of laser engraved removable sleeves. Again,
tissue embossing development personnel borrowed a technology that had been
developed for the printing industry. A sleeve, usually nickel or fiberglass, was
slid onto a special steel base, using compressed air to expand the sleeve. The
sleeve was then coated with the laser engravable material. The coating was
then prepared and laser engraved the usual way. The finished sleeve was slid
off the base (using air again), and only the sleeve was shipped to the customer.
Since a new steel base was not required, a great deal of money and time was
The slippage of the sleeve relative to the base would sometimes require stopping
the pilot embossing line and repositioning the sleeve, but this was acceptable for
a slow pilot line, especially when pattern registration was not an issue. This
slippage would probably make sleeves unacceptable at production speeds.
Production Embossing with Laser Engraved Cylinders
Using laser engraved cylinders as embossing rollers in production is only
practical in very special conditions at this time. The primary problem is poor
durability of the laser engraved material, especially when attempting to use it in
an environment where steel embossing rollers are customarily used. In these
cases, the useful life of the engraved cover can be anywhere between a few
hours and several weeks.
Laser engraved cylinders have been used to accelerate the startup date for a
product rollout with a new embossing pattern. Once a decision had been made
to proceed with a new pattern, the tissue producer would order enough laser
engraved cylinders to run a few embossing lines, and would order steel cylinders
for the remaining lines. The laser engraved rollers would arrive in 6 to 8 weeks,
allowing early startup, and would be replaced by the steel embossing rollers
when they arrived several weeks later. In some cases, the laser engraved
covers were removed and the steel bases engraved as conventional steel
Another deficiency of laser engraved cylinders is the poor surface finish in the
areas that were etched by the laser. The roughness appears as grooves that are
very pronounced in the more deeply etched areas, and barely visible near the
tops of the raised elements of the embossing pattern. In the case of R/S
embossing with bathroom tissue, this is mostly just a cosmetic defect, because
the paper rarely comes into contact with the deepest areas of the engraved
surface. Even when the paper does contact these grooved areas, it rapidly
polishes them smooth (with most materials used).
What’s In It Today for the Laser Engravers
Several of the laser engravers realized that supplying the embossing rollers used
for trial work would provide many benefits beyond the profits generated from the
small rolls usually involved in the testing process. Some of these benefits are
- Get to know customers within the paper industry and their pertinent
personal involved with embossing.
- Have the opportunity to learn from these contacts the different embossing
applications and which specifications are critical to which embossing
- Also learn from these contacts what aspects of laser engraving needed to
be improved, and the priority of each improvement.
- Learn the size and weight of the production rolls that would ultimately be
required if and when they could make the necessary improvements in their
process. This would assist them in evaluating the need for and the
specifications of new laser engraving equipment.
- Once the changes they had to make were identified, they could be
prioritized. Work could then begin to find or develop what would be
necessary to make the required improvements.
Basically, these improvements were as follows:
- Find or develop an extremely wear resistant roll covering with good laser
- A covering that is as wear resistant as chrome plated steel is
unlikely to be found. This is especially true if the condition of the
chrome plating is monitored for wear and the steel roll is de-plated
and re-plated when it shows spots where it is starting to wear
through. Re-plating is relatively quick and inexpensive.
- While a compound equally wear resistant to chrome plated steel
may be elusive, the material with acceptable wear resistance may
be on the horizon. Acceptance of somewhat shorter production roll
life may be appropriate, especially when you consider equalizing
factors such as trauma and pattern changes, which also limit
emboss roll pattern life.
- Find a method to do more sophisticated contour engraving.
Develop a means to produce a finer finish (smoother surface) on and in
- Most laser manufacturers have now developed special 3D
"embossing" packages. These packages can be provided as
conversions to existing equipment or sold as an option with new
equipment. Most of the laser engravers that are serious about
working in the emboss roll market now have this capability.
The laser engraving process has some associated problems with
element radiuses at the bottom of female cells, tight tolerances of
sidewall angles, etc.
- Tweaking of their procedures, plus Items "A" and "B" above has
already made considerable improvement to the finish on and in the
laser engraved emboss roll patterns achievable. As of this time the
surface finish of a quality laser-engraving job is not as smooth as a
quality conventionally engraved job. This may or may not be a
critical area depending on the requirements of the end products
- Most of these limitations are only critical with matched steel (S/S)
embossing applications but not rubber-to-steel (R/S) embossing
applications. The laser engraving software, and improved process
and compound developments have all given the laser engravers
improved control over this problem.
A laser engraver experienced in pattern development and embossing processes
should be the first to tell you that laser engraving cannot satisfy every
specification. Some pattern specifications require conventional engraving
processes, whereas still other specifications may require a marriage of both
Note: Keep in mind the following rule of thumb: A tool, master, or production
roll engraved from another tool, master, or production roll, can be of no
higher engraved quality than the tool, master, or production roll that it is
engraved from. This is true for either conventionally engraved or laser
engraved tools, masters, or production rolls.
Engraving Steel Directly or Indirectly by Laser
One result of the laser engraved trial rolls is reduction of cost for both the paper
industry and the conventional engravers. In most cases the conventional
engravers were selling tooling and trial rolls at a loss. This was done to help
procure the eventual order for the steel engraved embossing rollers to be used in
Conventional engravers realize a large percentage of their business is in
jeopardy if and when a durable compound suitable for laser engraving is
developed. It also followed that development which would enable direct laser
engraving of steel to normal tissue and towel pattern depths and geometry would
be even worse. They realize they need to reduce the cost of their process to
make the laser engraved rolls comparatively less attractive. Interesting enough,
one of the methods currently used to help reduce costs is to use laser engraved
tooling and/or laser engraved master rolls. Some conventional engravers have
purchased laser-engraving equipment. Others are outsourcing the laser
engraving services, while trying to budget for eventual purchase of laser
Using a Laser plus Acid to Engrave Steel Embossing Cylinders
Some of this laser equipment is used for a process that results in an engraved
steel embossing roller without the use of smaller tooling. Basically this is a three-
- Coat the steel roll with a special thin coating, which will protect the steel
from acid and is capable of being removed by the laser.
- The laser is programmed to burn away the protective coating to remove it
from areas they wish to etch with acid.
- The steel roll is then acid etched to begin putting the pattern into the steel.
This process is repeated until the pattern is fully etched into the steel roll. Some
of the engravers that use this process are still outsourcing laser engraving of
tooling and lab line emboss rolls.
Earlier in this article we mentioned there was development work being done to
enable laser engraving typical tissue and towel patterns directly into the steel
embossing rollers. This is not available today. However, some laser
manufactures and engravers believe it is a fore-drawn conclusion that it will be a
reality in the near future.
Using Laser Tooling to Engrave Steel Tooling
A tool or tooling roll is a small engraved cylinder which is used to engrave
another cylinder through a process called "making a transfer", where a reverse
copy of the engraved pattern is transferred to the new cylinder. The new cylinder
may be another tool, a steel master roll, or the final embossing roller (also known
as the production roll). With the exception of dinner napkin embossing patterns,
tooling rolls are usually smaller than 6" diameter by 8" face.
In most cases of conventional engraving an engraved hardened steel tool is used
to make new steel tooling. Extremely high pressure is used to press a hardened
engraved steel tool into a new non-hardened steel tool blank. As the raised
elements of the hardened tool are forced into the non-hardened tool blank, the
areas of contact become compressed and work-hardened. The work-hardened
contact points cannot be allowed to become too hard. As the contact points
become harder progress slows because pressing is less effective. In addition,
the contact points may become hard enough to damage the hardened tool. To
prevent this from happening, the burrs must periodically be filed off the surface of
the new tool and protective wax rolled on the surface. This protective wax is
applied with a roller onto the new tool so as to protect the roll surface but not get
into the cells being formed at the contact points. The surface of the work-hardened
tool is protected and contact areas are etched with acid to remove the
hardened material from the contact areas. By etching away the hardened
material the pressing action can once again effectively compress the steel at the
contact area. These pressing, filing, waxing, and etching processes are repeated
until the pattern is fully pressed into the non-hardened tool.
When a laser engraved tool is used in place of a hardened steel tool to engrave
steel, the processes used are quite different. The laser tool is much softer than a
new tool blank (regardless if the new tool is pre-hardened or not) and therefore
no pressing can be used. The fact that even the hardest coverings being used
for laser engraving are compressible will cause element distortion if too much
pressure is applied. The covering material also has memory and barring damage
(and given enough time) will return to a like-new condition after the pressure is
removed. If this happens, inspection of the new tool will show the cell openings
in the new steel tool will be wider and shallower than elements on the laser
The new blank steel tool starts the process by having the protective wax rolled
onto the surface. The laser tool is brought into contact with the new tool with
only enough pressure to displace the wax. Excess wax is wiped from the laser
tool until a thin film remains on the new tool with the contact points clean of wax.
The new tool is given an acid bath to start etching the contact points into the
steel. The etch time and acid strength must be monitored to insure the acid is
only etching away material intended to be removed. The cell being formed
should mate with the elements on the laser tool used to squeeze away the wax.
The new tool is then rinsed and fresh wax is applied. These processes are
repeated until the pattern in the new tool reaches full depth and is a reverse
image of the laser engraved pattern.
Laser Engraved Master Rolls Used to Engrave Production Rolls
A master roll is a large engraved cylinder which is used to engrave the
production roll (embossing roller). The master roll is usually wider than the
production roll. See Figure 4 below "Tooling Rolls and Master Rolls".
The process differences between using a laser engraved master roll or a steel
engraved master roll are not as great as when engraving tooling because both
use only etching to engrave the production roll. The pressure used when
engraving with a laser engraved master roll is still considerably less than what
can be applied when using a steel master roll. When using a laser engraved
master it is more critical to avoid a crown from developing in the production roll
throughout the entire engraving process. Some of the techniques used to
eliminate a crown near the end of the engraving process with a steel master
cannot be used with a laser engraved master.
Many engraving operators whom I’ve talked to tell me that once they got used to
laser engraved masters, they actually prefer them over steel master rolls. They
tell me that they can usually complete a production roll in fewer hours with a laser
engraved master roll than with a steel master roll.
The element placement accuracy of the laser engraved master is excellent.
Repeatability when making a second laser engraved master roll is quite good.
There are however still variables that detract from perfect repeatability, such as
variability in the covering compound. The variables when engraving a new steel
engraved master roll are comparatively greater. When engraving production rolls
however, repeatability is more of a function of operator and process consistency
than it is type of master roll. As the saying goes, "The quality of a production roll
can’t be better than the tooling (or master) but it can be worse".
Laser engraved rolls have found a place in today’s paper industry with the
potential of playing an even greater role in the future. Making this potential real
will depend upon continuing developments in several areas:
- Composition of the surface to be engraved.
- Capabilities of the laser engraving machines.
- Laser engraving process technology.
- Using laser engraved rolls to make steel embossing rolls.
- Learning how to reduce the wear on laser engraved rolls when used for
This paper was originally published by Paperloop Inc., and was presented
at CMM International 2003 Conference by Carl Ingalls and Ed Giesler on 15 April 2003.