Home' FLEXO Magazine : September 2016 Contents different holder as-
sembly on the press,
then use that partic-
ular OEM’s specs as a
guideline for proper
sizing. The most criti-
cal dimension is the
doctor blade’s width
It can be surpris-
ing how frequently
wiping or score line
issues are caused by
an incorrect blade
size. Sometimes as
perhaps because of a
change in suppliers
rooms find someone
ordered or changed
the blade width from
1.5-in. to 1.563 -in.
and as a result, the
printer began expe-
riencing score line issues. So, it is very important to make sure your
sizing is exactly correct.
Next, speak with operators and ask why they are using the current
blades. Do they like them? If so, what do they like best—and is it
appropriate for the desired application? If operators are not satis-
fied with the current blades, what do they think could be changed
to achieve better performance? The input of the day to day users of
blades and other print products is invaluable. These honest answers
under real world conditions enable the collection of proper facts and
data for the next step in the decision making process.
With all the information and specifications on hand regarding the
current blade setup, it’s time to begin an in depth evaluation of actual
performance vs. intended outcome.
Start the evaluation by creating a document or system to track day
to day doctor blade usage. Try to make it as simple as possible for
the operators, as too much paperwork may discourage them from
recording data. If possible, let the press crews take part in creating this
form or have input on its final draft. Gather the most important data
needed, such as:
• Blade type, deck or unit
• Ink color
• Date in/date out
• Anilox linescreen
• Length of run time
Use feet, meters, impressions or whatever is currently used to measure
job run length—but be consistent so results are easily compared.
When possible, on a long running job, keep print samples, measure
density, and check for dot gain, dirty print and color shifts. Your goal
is to capture as much data as possible on the performance of your
current doctor blades; therefore, when you start trials with others, you
will have a benchmark.
Use this information to set targets and goals for process improve-
ments. You can also use the information collected to identify when
your blades start to fail. With this data, you can put in preventative
measures to keep your quality constantly at its highest peak. If you
change your blades at a set time before failure, you can effectively
eliminate print defects and unwanted press downtime caused by
Now that all the data is collected, consider requesting a used doctor
blade evaluation to be performed by your supplier. This means gath-
ering a set of used doctor blades, along with all the data containing
information and tracking forms used. The blades should be carefully
cleaned and labeled with press ID, unit or deck number, and color.
Before shipping the blades, do a visual inspection. Make note of any
odd wear patterns or anything that looks out of the ordinary. Mark
the blades or put notes in the report for the supplier to look into any
oddities. Box all this up and send to your supplier for the proper used
Used doctor blades are the diary of the press. They will tell you all the
secrets of how the press is running, how the press operators are setting
up the chambers and the amount of pressure being applied. This is
only a snapshot of what is happening, but it will give you enough
information to complete phase two of the blade evaluation process.
The critical information at this point is:
• Wear angles: At what angle is the blade coming into contact with
the anilox? Proper doctoring occurs between 35 degrees and 45
• Contact area: The size of the area where the doctor blade touch-
es the anilox. The proper contact area should be between 180-μ .
to 230-μ ., depending on blade base and tip thickness
• Amount of wear: How much of the blade has been removed?
This can be determined by measuring weight or width of a new
blade vs. a used one
Be sure to request photos of the used blade tip. Figure 1 shows how
a blade can wear f rom using the wrong type on an aggressive anilox
roller with large volumes.
Figure 2 shows two blades. They are the same type and ran on the
same roller, for the same amount of time, with the same ink. The
upper blade was incorrectly matched to the application. The lower
Figure 1: Aggressive doctor blade wear
Photos and charts courtesy of Daetwyler
Figure 2: Improper blade choice (top) vs.
proper blade choice (bottom)
58 FLEXO | SEPTEMBER 2016
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