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.
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.
2 Specifications/Operating principles Specifications Item Specifications Printing method Dot matrix system Printing direction Unidirectional printing 2.5 lines/sec. ± 20 %; DC 5.0 V, 25 °C in Printing speed continuous printing Printing format Number of dots 144 dots/line Character configuration (5 + 1) × 8 Number of columns Paper feeding Paper feeding pitch...
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.
2-3-2 Sensor mechanisms This mechanism has two sensors for de- tection, 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.
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.
Paper Feed ing on whether the printer is the MD- 910 or MD-911. Home Position For the MD-910, the number of print- Printable Area ing columns is 24, and each 12 col- umns of printing on the left and right is performed by each print head.
(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 be- yond the home position, the shaft pin goes through a sharp curve in the...
2-3-4 Paper feed mechanism Since this printer completes one line of printing by dividing it into upper and lower halves, two types of paper feeding are provided; one is paper feeding without LF (line feed) because the lower half is printed after the upper half.
(2) Paper feeding without LF (line feed) mechanism The PF cam gear that drives paper feeding turns one time per head assembly shuttle. The cam inside the PF cam gear presses down the protrusion (part A) of the sector gear assembly when the head assembly returns.
(3) Paper feeding with LF (line feed) mechanism In paper feeding with LF mechanism, only the protrusion pressing down mechanism is different from that of paper feeding without LF mechanism. Two cotter pins are set on the outside of the PF cam gear and turn together with the PF cam gear.
2-3-5 Ribbon cartridge drive mechanism The PF cam gear that drives paper feed- ing is also used to turn the ribbon cartridge. The driving force of the PF cam gear is transmitted to the worm where the direc- tion of operation is changed 90 °. The driving force converted is transmitted from the worm to the worm gear and the ribbon cartridge is turned by the ribbon...
2-4-2 Terminal mechanism Terminal No. Terminal name Remarks Motor (–) Motor is ON with GND Phototransistor emitter Dot pulse sensor Phototransistor collector LED cathode LED anode Printing solenoid D (–) 1st print head Printing solenoid B (–) Each solenoid is ON with GND Printing solenoid A (–) Printing solenoid C (–) Common (+)
3 Disassembly/Reassembly Prior to maintenance work, be sure to observe the following caution: CAUTION (1) When the printer is operating satisfactorily, do not unnecessarily disassemble, reas- semble or adjust the printer. In particular, do not loosen any screws on the compo- nents.
Assembly procedure The assembly procedure is described by major assembly blocks. Part names in text are the same as those in Parts List. 3-3-1 Setting paper feed solenoid assembly (1) Place the core in core base as- sembly. At this time, align the pro- trusion of the core with the hole of the core base assembly.
(3) First apply Froil G-311S to the arma- ture pivot of the bobbin assembly, then install the armature spring and the ar- mature assembly. At this time, check the direction of armature spring. (4) Secure the armature assembly with the E-ring and attach the armature spring to the hole of the armature as- sembly.
(2) Place the ribbon mask in the head as- sembly. At this time, align the holes of the ribbon mask with the protrusions of the head assembly. Note: The ribbon mask is very thin, so take care not to bend it when in- stalling it.
(4) Install the PF bracket bushing in the bushing groove of the paper feed bracket and secure the paper feed roller. (5) Install the brake spring in the brake groove of the paper feed roller. (6) Attach the platen to the paper feed bracket with two platen spacers and two screws (M2 ×...
3-3-4 Setting the main body assembly (1) Apply Froil G-311S to the gear of the gear box assembly, the shaft of the cylinder cam assembly and the teeth, the opposite of the shaft. (2) Combine the cylinder cam assembly with the gear box assembly and install the cam shaft bushing in the shaft of the cylinder cam assembly.
(5) Apply Froil G-311S to the pivot of the PF cam and the cam of the PF cam gear. (6) The cam faces inside. Insert the PF cam gear in the pivot of the PF cam. Note: 1) When inserting the gear, turn the cylinder cam assembly beforehand so that the claws of the paper feed gear are horizontal.
(9) Apply Froil G-311S to the upper sur- face of the PF cam gear. (10) Install the return ring and the PF6D cam in the PF cam gear and secure it with the E-ring. (11) Apply Froil G-311S to the outside and surfaces of the PF6D cam.
(13) Mount the paper pressure guide on the back of the frame assembly. (14) Set the PF clutch spring and the clutch spacer in the clutch gear of the paper feed and then put it in the frame as- sembly from over the paper pressure guide.
(18) Apply Froil G-311S to the bushing of the sector gear assembly and then in- sert the worm and secure it with the E-ring. (19) Set the sector gear spring between the sector gear assembly and the frame assembly. (20) Apply Froil G-311S to the fitting hole of the ribbon drive and then insert the ribbon drive pin from under the bot- tom of the frame assembly.
(22) Apply Froil G-311S to the upper sur- face of the worm gear and then install the ribbon drive latch and the latch spacer and secure them with the push nut. Note: When installing these, check the direction of ribbon drive latch. (23) Secure the solenoid assembly to the right of the frame assembly with a single screw.
(26) Apply Froil G-311S to the tip of the re- set arm and the two shaft bushings of the head assembly. (27) Set the shaft pin in the head assem- bly. (28) Hang one end of the head return spring, which is set in the head assem- bly, on the notched section of the right of the head assembly.
(30) Insert the two carriage guide shafts from the left of the frame assembly and pass them through the head assem- bly and secure them with the E-rings. (31) Apply Froil G-311S to the groove of the cylinder cam assembly. (32) Solder the following terminals on the PCB terminal assembly: FPC terminals (ten) to the head as-...