SM74 offset printing machine application experience: three cases of failure
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Three troubleshooting
1. Weekly version of the motor does not work
The circumferential version of the SM74 offset printing machine will often fail during production, and it will be good or bad, and it will not work at all.
Troubleshoot, remove the circumferential plate-making motor from the machine, open the plastic protective cover of the motor, and find that there is more oil inside. Unscrew the nut on the carbon brush mounting hole and pull the carbon brush outward to feel some resistance. Carbon powder was deposited in the commutator (commutator) through the carbon brush mounting hole. Flush the carbon powder on the surface of the commutator with gasoline, and clean the carbon brush and the oil and carbon powder on the inner wall surface of the mounting hole to make the carbon brush move freely in the mounting hole. It works fine after reinstallation.
Analysis of the cause: The circumferential plate-making motor is installed in the transmission side shield. The sprayed oil enters the motor along the wire. Once the carbon powder milled by the carbon brush meets the oil entering the carbon brush mounting hole, the carbon is added. The friction between the brush and the inner wall of the mounting hole counteracts the force of the spring pressing the carbon brush against the surface of the commutator. As the carbon brush wears, the carbon brush eventually comes out of contact with the surface of the commutator, and the motor does not work. After cleaning, the carbon brush is in full contact with the surface of the commutator under the action of the spring, and naturally resumes normal operation.
2. Water bucket roller head and transmission gear shaft wear
When the SM74 offset press is shipped from the factory, the fastening bolts connected to the water roller and the transmission gear are galvanized bolts instead of the usual stainless steel bolts. The bolt is used in a humid environment for a long time, and the surface is completely rusted, resulting in a tight connection between the water roller head and the transmission gear shaft. If it is not found in time, the axis of the water bucket roller and the metering force are not parallel, and the water output is unstable, which affects printing. quality.
Trouble shooting, the key to the repair of the bucket roller head and the transmission gear wear surface is to repair the axis of the surface of the part, so that the coaxiality error with other working surface axes is restored to the permissible range.
Resolve parts, clean, and weld the worn surface. When processing the water bucket roller head, first rough a cylindrical tire with an outer diameter of 58mm and a length of 30mm, and machine three M6 tapped holes on the end face. The position and the diameter of the water bucket roller head are three. The counterbore of mm corresponds. The tire is mounted on the lathe chuck, the end face and the inner hole of the finishing wheel, and the processing size of the inner hole forms a transitional fit with the size of the unworn surface of the other end of the water roller head. Install the end of the bucket head with no wear on the inner hole, bolt it to the tire, and weld the surface to the required size.
When machining the transmission gear shaft, the first outer diameter is 30mm. A cylindrical tire with an inner diameter of 17.5 mm and a length of 50 mm was uniformly machined with three M4 tapped holes on a circumference of 15 mm from one end. The tire is mounted on the chuck of the internal grinding machine, and the inner hole is ground so that the size of the inner hole forms a transitional fit with the size of the bearing mounting position on the transmission gear shaft. Insert the transmission gear shaft into the inner hole of the tire, and evenly tighten the three M4 fastening bolts to prevent the transmission gear shaft from rotating relative to the tire during processing. Grind the inner hole of the transmission gear shaft to the required size, and then repair the excess part of the welding gear shaft opening part with the shaping grinding wheel, so that the water bucket roller shaft head can be smoothly disassembled from the opening.
3. Tooth bar spring guide is damaged
On the rear end of the SM74 offset press, the two rows of rollers are used to achieve the closing action of the rows of teeth. A spring guide in the device is coupled to the row of teeth via a needle bearing and a small shaft having a diameter of 10 mm to transmit power. One corner of the spring guide has a chamfer of 6mm*45°, and the chamfered slope has an oil hole with a diameter of 3mm, which becomes the weak link of the spring guide. If the guide rod of the transmission side spring device is found to be damaged from use during use, it needs to be replaced.
Replacement method: first remove the open tooth ball on the tooth row, clean the outermost tooth pads on both sides; then install the magnetic table seat, manually turn the car, measure the height difference of the tooth pad surface relative to the roller surface with a dial indicator And make a record; the relative position of the tooth row assembly and the drum in the axial direction should also be marked; remove the 12 M8 bolts, remove the tooth row assembly from the drum, disassemble the spring device, and replace the spare parts.
When installing, first adjust the axial position of the row assembly and the roller in place according to the mark, and tighten the 12 M8 bolts slightly. The difference in height of the surface of the dental pad relative to the surface of the roller was measured with a dial gauge, and the height of the dental row assembly was adjusted in comparison with the recorded value. Tightly and evenly tighten the 12 M8 bolts, and then use a dial gauge to measure the height difference between the surface of the pad and the surface of the snowball. It is required that the value error difference before and after disassembly and assembly is within the allowable range, otherwise it will be reinstalled. Finally, put on the open ball.