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980541-001 Rev. A
P640i Card Printer User Guide
47
K (Black) Panel Printing 
Black Panel - Compensation: 
Overlay - Panel Speed: Speed at which the “OP” 
overlay panel, if any, is printed (rarely used in printers 
with laminating capability). If a Uv ribbon is selected, 
the text changes to say “Uv Panel Speed”. 
Overlay Panel - Compensation: Mainly used 
with Uv ribbon to optimize the appearance of ultra-
violet-visible text. 
Ribbon - Position (mm): This has to do with 
positioning the color ribbon relative to the print head 
such that when the head descends it lands solidly 
within
 
the panel, not too early, not too late. Keep in mind the 
following: 
While the head is down and printing, ribbon 
motion is controlled by the card itself, not by 
the ribbon takeup (which at this time serves 
only to peel the ribbon cleanly off the card). 
The color panels are about ½" (12 mm) 
longer than the image printed on the card. 
This means that between one color printing 
pass and the next, when the head briefly lifts, 
the takeup drive has to shift the ribbon 
rapidly to bring the next color panel under the 
head. 
The transition from one panel to the next in 
the color ribbon is marked by a black stripe 
which activates the ribbon sensor below the 
supply roll. It is used, together with a count of 
pulses from the motion sensor, to determine 
ribbon position. 
Unlike YMC color printing, which is required only 
to deliver realistic portraits and pleasing graphics, 
the K panel serves a more quantifiable purpose, 
namely machine readability. In practically all 
instances of K panel usage, there is a requirement 
both for bar codes and well defined text - and 
sometimes for signatures, which can be ìspideryî in 
appearance unless compensated for. Unfortunately, 
these requirements are in opposite corners.
The P640i provides three controls for K panel 
printing: these are:
1.
Black panel compensation (Adjustment 
screen, this page TN4 - x)
  If a line of black dots 
is printed along the card motion axis, the 
heating element  (pixel) in question doesn’t 
cool down completely between adjacent dots. 
Without compensation, the steadily increasing 
residual heat would cause the printed dot to 
increase noticeably in size (“bloom”), below 
left. Properly compensated, the dot size is 
reasonably constant, below right.
2.
Black panel density (Color Calibration screen, 
page TN4 - x) This control the amount of heat 
energy applied to any pixel required to be 
“black”. A higher value gives darker printing, 
but can cause undesirable blooming (indefinite 
edges).
3.
Black panel preheat (Color Calibration 
screen, page TN4 - x)
 Think of this as a 
temperature offset applied across the entire 
head, specifically for K panel printing. A higher 
value results in better resin transfer on the 
leading edge of graphics and text than you 
would get with a “cold start”, but it may lead to 
undesirable blooming (indefinite edges) 
overall.
The following default values deliver a good 
compromise between barcode readability and the 
appearance of text and signatures: Compensation 
55Density 117Preheat 15
Without compensation
With compensation
Ribbon sensor
Motion sensor
Supply 
arbor
Takeup 
arbor