Casio MD-910 Technical Manual
TECHNICAL MANUAL
(without price)
DOT PRINTER
MD-910
JAN. 1997
Features
The MD-910 series is a dot matrix compact printer that uses two serial print heads.
This printer has been developed as an output terminal for various applications such as POS terminals,
measuring/analyzing equipment, medical equipment and communication data equipment, and has
been designed to be as compact as possible.
• Compact and lightweight
• High-speed printing of up to 2.5 lines/sec. (for MD-910) or 1.8 lines/sec. (for MD-911)
• Clear printout with high resolution of 8 dots/mm
• Paper width of print head
• Longer life of print head
• Simple mechanism for high-reliability
Contents
1 Printer usage and Care..................................................................................................................... 1
2 Specifications/Operating principles ................................................................................................... 2
2-1 Specifications............................................................................................................................ 2
2-2 Outline of mechanism ............................................................................................................... 3
2-3 Mechanism and operation principles ........................................................................................ 3
2-3-1 Power transmission mechanism ................................................................................... 3
2-3-2 Sensor mechanisms ..................................................................................................... 4
2-3-3 Print head mechanism.................................................................................................. 5
2-3-4 Paper feed mechanism................................................................................................. 8
2-3-5 Ribbon cartridge drive mechanism ............................................................................. 11
2-4 External connection terminals................................................................................................. 11
2-4-1 Terminal arrangement ................................................................................................ 11
2-4-2 Terminal mechanism .................................................................................................. 12
2-4-3 Terminal circuit diagram ............................................................................................. 12
3 Disassembly/Reassembly............................................................................................................... 13
3-1 Tools .................................................................................................................................... 13
3-2 Disassembly procedure .......................................................................................................... 13
3-3 Assembly procedure ............................................................................................................... 14
3-3-1 Setting paper feed solenoid assembly........................................................................ 14
3-3-2 Setting the head assembly ......................................................................................... 15
3-3-3 Setting the paper feed assembly ................................................................................ 16
3-3-4 Setting the main body assembly................................................................................. 18
4 Parts list .................................................................................................................................... 26
5 Exploded view................................................................................................................................. 28
1 Printer usage and Care
(1) Use recommended register paper. Otherwise, printing quality and the life of the print head will not be
guaranteed. The width of paper must meet the specifications.
(2) Never allow a mechanical impact (including the entry of foreign matter) to the print head surface.
(3) Any dust on the print head surface must be wiped off by an applicator soaked in ethanol or the
equivalent.
(4) The dedicated ribbon cartridge should be taken off when the printer is carried or not used for a long
period.
(5) Do not feed current to the print head if it is wet or moist. If current is fed, the print head may be
damaged. If the print head is wet or moist, dry it fully and then start printing.
(6) Inserting register paper
• Cut the top end of the register paper
straight (it should never be fluffed or bent)
and insert it.
• When the top end of the register paper
comes out of the print head, check that it
is set straight and then pull it.
(7) Removing register paper
• Before removing the register paper, be sure
to stop feeding current to the print head.
• Pull out paper straight in the direction of
paper exit.
— 1 —
2 Specifications/Operating principles
2-1 Specifications
Item Specifications
Printing method Dot matrix system
Printing direction Unidirectional printing
Printing speed 2.5 lines/sec. ± 20 %; DC 5.0 V, 25 °C in
continuous printing
Printing format Number of dots 144 dots/line
Character configuration (5 + 1) × 8
Number of columns 24
Paper feeding Paper feeding pitch 3.52 mm (10 dots/line)
Rapid feed rate 5 lines/sec. ± 20 %; DC 5.0 V, 25 °C in
continuous printing
Inking Dedicated cartridge (black or purple)
Detection Dot pulse Photointerrupter
Reset pulse Leaf switch detector
Paper feeding solenoid Drive voltage DC 5.0 V
Resistance 7 h ± 3 (temperature: 25 °C)
Printing solenoid Drive voltage DC 5.0 V
Resistance 1.7 h ± 0.3 (temperature: 25 °C)
Motor Type DC brush motor
Drive voltage DC 5.0 V
Max. current Approx. 1 A
Average current 0.3 A or less; DC 5.0 V, 25 °C in continuous
printing
Paper Type Plane or recommended paper
Paper width 57.5 mm
Cut sheet 45 to 55 kg
(thickness: 0.06 to 0.085 mm)
Copies Original paper (34 kg) + single copy (34 kg)
(Total thickness: 0.13 mm or less) Non-carbon
paper
Life of print head 1,500,000 lines
Exterior dimensions 90 (w) × 45.5 (d) × 15.8 (h) ± 0.5 mm
(excluding paper feeding nob and feet)
Weight 105 g ± 10 %
— 2 —
2-2 Outline of mechanism
This printer mechanism is divided roughly into the following seven blocks:
• Power transmission
• Sensor
• Print head
• Paper feed
• Ribbon cartridge drive
• Frame
• Motor
For example external control circuits attached to this printer, please see the appropriate operating
manuals.
2-3 Mechanism and operation principles
The mechanism and operating principles are described for five blocks out of seven (i.e., excluding
the frame and motor).
2-3-1 Power transmission mechanism
This mechanism transmits a motor driving force to the head assembly, paper feed roller and ribbon
cartridge.
The head assembly is driven by the cylinder cam assembly connected to the gear box assembly
which encloses the motor.
The driving force transmitted to the cylinder cam assembly is sent to the PF cam
gear and PF6D cam through the paper
feed gear. Either the driving force transmitted to the PF cam gear or the driving
force transmitted the PF6D cam can be
selected, depending on the operation status, and is sent to the clutch gear through
the sector gear assembly.
The driving force of the clutch gear is
transmitted to the clutch wheel connected
to the paper feed roller, driving the paper
feed roller.
The driving force of the PF cam gear is
transmitted to the worm, worm gear and
ribbon drive pin respectively, so that the
ribbon cartridge is driven by the ribbon
drive pin.
— 3 —
2-3-2 Sensor mechanisms
This mechanism has two sensors for detection, a dot pulse sensor and a reset
pulse sensor.
(1) Dot pulse sensor
The dot pulse sensor consists of an
encoder (slit disk) directly connected
to the motor and a photointerrupter
reading the rotation. The rotation read
(number of slits counted) is treated as
the DP signal that is the core of the
printing control.
(2) Reset pulse sensor
The reset pulse sensor uses a leaf switch which turns ON/OFF according to the head assembly position.
This sensor detection signal represents the RP signal that specifies the print head home position and printing start base position.
— 4 —
2-3-3 Print head mechanism
This printer has two print heads arranged at intervals on the left and right, so that the left half and
the right half of the register paper can be printed simultaneously as it is moved from left to right.
One movement causes the upper part of one line to be printed and the next movement causes the
lower part of the line to be printed. Therefore, two print head movements complete printing of one
line. The print heads, however, print the register paper only when they move from left to right.
(1) Printing control
Each print head has four printing solenoids and each solenoid is turned
ON/OFF according to the printing data
and the corresponding printing pins
are activated to form character dots.
This printer, however, does not have
a serial/parallel conversion circuit.
Therefore, ON (L level)/OFF (H level)
signals are directly provided to the
eight data lines for each printing solenoid.
Printing timing is controlled by the DP
signal which is detected by the dot
pulse sensor and is treated as a clock
pulse and the RP signal which is detected by the reset pulse sensor and
is treated as a starting point.
— 5 —
(2) Printing data and printing position
The number of printing columns and
one character dot matrix vary , depending on whether the printer is the MD910 or MD-911.
For the MD-910, the number of printing columns is 24, and each 12 columns of printing on the left and right is
performed by each print head. 4 dots/
line is produced by one print head
movement.
6 (5 + 1) horizontal dots make up one
character and the total number of horizontal dots in the printable area is 144
(12 columns × 2 × 6 dots).
For the MD-911, the number of printing columns is 40, and each 20 columns of printing on the left and right is
performed by each print head. 4 dots/
line is produced by one print head
movement. 4.5 (4 + 0.5) horizontal dots
make up one character and the total
number of horizontal dots in the printable area is 180 (20 columns × 2 × 4.5
dots).
5 mm 47.5 mm 5 mm
Home Position
12 (20) Columns
One Line
2/2 Line 1/2 Line
Direction of
Paper Feed
Printing Position
Printable Area
144 (180) Dots
1st Print Head 2nd Print Head
12 (20) Columns
72 (90) Dots
Printing Solenoid A
Printing Solenoid B
Printing Solenoid C
Printing Solenoid D
Printing Solenoid A
Printing Solenoid B
Printing Solenoid C
Printing Solenoid D
72 (90) Dots
Printing Solenoid E
Printing Solenoid F
Printing Solenoid G
Printing Solenoid H
Printing Solenoid E
Printing Solenoid F
Printing Solenoid G
Printing Solenoid H
Printable Area
4 Dots/Line 4 Dots/Line
— 6 —
2 Dots/Line: LFHome Position
Printable Area in Detail
(Values parenthesized are for MD-911)
(3) Head drive mechanism
The head assembly is connected to the cylinder cam assembly via a shaft pin. The shaft pin is
inserted in a scribed groove on the outside of the cylinder cam assembly and moves along the
groove when the cylinder cam assembly is turned to drive the head assembly.
When the head assembly travels beyond the home position, the shaft pin
goes through a sharp curve in the
scribed groove, so it moves slowly.
At this time, printing is performed.
When the head assembly travels beyond the printable area, the direction
of movement is changed to the home
position because the direction of
groove is reversed and the head return spring tension is activated.
At this time, the head assembly travels at high-speed because the groove
is turned to the slow curve.
Register paper feeding is performed
when the head assembly returns.
When the head assembly travels to
the home position, it returns to the
original groove position, and the operation is repeated.
— 7 —