Zebra Technologies P640i 사용자 설명서

48

P640i Card Printer User Guide

980541-001 Rev. A

Adjusting the ribbon position drives the leading edge 
of the panels forward or backward relative to the 
printhead, the aim being to ensure that each swipe of 
the head is centered in its color panel (this you can 
easily check by inspecting image negatives from on 
the takeup roll). The photos below show the effect of 
incorrect ribbon positioning. 

The arrows show the

direction of card movement. In the example at left, the ribbon
has advanced too far, with the result that the head swipes a
few millimeters of the following panel - see inside the circle.
Reduce the ribbon position parameter to correct this. The
example at right is the exact opposite - ribbon not advancing far
enough, so increase the position parameter to correct. 

Ribbon - Torque Adjust (%): Adjusts the current 
applied to the ribbon take-up motor (more current = 
more torque), thus controlling the ribbon tension 
between print head and take-up. Lowering the value, 
default = 100%, can help reduce ribbon wrinkling (but 
note that there are other factors, see Ribbon 
Wrinkling, inset below). 

The downside of reducing the ribbon torque is an 
untidy, loosely wrapped takeup roll. That isn’t 
important, except aesthetically, but low torque does 
matter if the ribbon fails to advance when it should, 
see Ribbon Position, left. 

Printhead Position - Adjust: Adjusts the 
downward motion of the printhead. The higher the 
number, the greater the amount of overrun following 
sensor activation. Ribbon Wrinkling

Printhead - Resistance (Ohms): This value 
should match what is written on the printhead. Enter a 
new value if the printhead is changed. If you enter a 
lower number than what is printed on the head itself, 
the printed image will be lighter than expected, and 
vice versa. 

The printhead drive train comprises a stepper motor, a 
gear quadrant, and a crank arm directly coupled to the 
printhead bracket, photos below. In the down position, 
the printhead spring is slightly compressed, with the 
crank arm extended (which means that the torque 
demand on the motor is at its lowest). 

Increasing the printhead position parameter does not 
result in a mesurable increase in head pressure, which 
is more or less binary - it is either under spring 
pressure, firmly in contact with the card, or not in 
contact at all. 

 

 : If the printhead doesn’t press 

firmly on the card during the printing “swipe”, there is 
nothing to stop uncontrolled advancement of the 
ribbon due to the takeup drive. To correct this, 
increase the adjust parameter to the point where the 
ribbon ceases to advance freely, then add 

 more to 

the number. 

  

 

Keep in mind the following:
•

The amount  of ribbon drag exerted by the supply arbor is con-
trolled by a friction clutch. This is set for a torque of approxi-
mately 5 oz-ins (36 mN.m), and should not be adjusted unless you 
have a torque gauge.

Ribbon drag exerted by the takeup arbor is controlled by varying 
the current applied to the motor.

Ribbon wrinkling can be caused by one or more of 
the following factors (but always try adjusting 
ribbon torque first):

Takeup torque too high

Supply torque (drag) too high

Too much preheat - ribbon sticking

Dense patches with sharp transitions (text, graphic elements) on a 
dark image

Card thickness not uniform 

Printhead too hot because resistance value in flash memory higher 
than actual head resistance

Printhead angle adjust screwed down too far 

Printhead not pivoting freely

Printhead rattling in frame

Printhead not right-angled relative to card motion (yaw adjust)

Wrinkle control is essentially a balancing act of  
several variables - especially the balance between 
takeup and supply torques.

Example of ribbon wrinkling