Figure Platen Gap Setup Sequence

Figure 2-25 shows the platen gap setup conceptual diagram. Symbols used in the diagram are as follows:

PG : Gap between the printhead and platen (should be constant)

A : Distance which varies in accordance with the difference in the printhead dimension

B : Distance which varies in accordance with the difference in the dimension of a mechanism other than the printhead x : Amount of PG motor rotation equal to 70 steps (constant value)

PGEND : Position which limits the PG motor rotation (The PG motor cannot rotate beyond this position.) (constant value)

The PG mechanism is composed of the shaft which moves the PG motor, platen, carriage, printhead, and carriage forward and backward and the gear connected to the shaft. Since the dimension of each part is different depending on the product, the PG value also varies depending on the product. Therefore, in order to make the PG value constant among all the products, the values which are not constant (A and B) are adjusted.

These values are alpha, used to adjust for the difference in printhead dimensions, and beta, used to adjust for the difference in PG mechanism dimensions. They are actually numeric data used by the software to determine the amount of PG motor rotation.

The adjustment values are written to the SRAM (5C) on the main board, which is maintained by a backup circuit when the printer power is turned off.

When the printer power is turned on, the CPU reads these values as part of the initialization sequence, and adjusts the PG.

Platen

Surface

PG

A

B

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