Flesher: Technical Support
System 3 Service Bulletin 003:
Setting System 3 Printwheel Belt Tension
The print wheel belt tension on the System 3 machines must be set to insure accurate positioning of the printwheel. There are several factors that affect the accuracy of wheel positioning. All must be correct for good vertical title base line alignment. Some common problem are:
- Insufficient spindle lubrication
- Worn or stretched belt
- Improper belt tension
Insufficient spindle lubrication causes excessive friction which may prevent the motor from moving the wheel to exact position. The motor, belt, and spindle combination must move with as little friction as possible. Be sure the bearings are lubricated regularly with a good grade of high temperature synthetic oil such as AMSOIL 30 weight motor oil (one CC per week is adequate). A worn or stretched belt may allow excessive free play between the belt teeth and the pulley teeth. If the belt tension is too loose, excessive free play may be created and if the belt tension is too high there may be excessive friction. Each of these problems will cause the inaccurate rotational positioning of the printwheel showing up as letter-to-letter spacing inaccuracies on horizontal titles and irregular appearing base lines on vertical titles. While some irregular spacing on horizontal titles may be unnoticeable, base line irregularities on vertical titles are much more apparent.
Setting the tension correctly sometimes involves several iterations as the tension is critical but cannot be easily measured. If the tension is too low, the belt may not fully engage the teeth of the pulleys leaving some free play. If the tension is too high, excessive friction may prevent the motor from moving the wheel to exact position. In either case, the result will probably be an irregular base line on vertical lettering and uneven character spacing on horizontal lettering.
Belt tension should be adjusted after the machine is thoroughly warmed up so that all spindle components are at operating temperature. The metal components as well as the belt will expand with temperature and affect belt tension. After adjustment, re-tighten the motor mounting screws.
If the belt is old or has been over tensioned and stretched, it should be replaced before attempting to set the tension.
BELT TENSION ADJUSTMENT PROCEDURE
Each time the belt is adjusted, the machine should be first turned off, the foil fingers moved so that they are under the printwheel (and out of the way) and the printwheel tilted to the vertical position or slightly forward of vertical for easy access. Belt tension is adjusted by loosening the four allen head cap screws which fasten the motor to the motor mounting plate and adjusting the screw on the lever arm. Use a hex wrench to loosen all four of the motor mounting screws, make the adjustment, and then re-tighten the three motor screws which are easy to get to. You can 'cheat' by not tightening the upper right screw (which is more difficult to get to) until after the final adjustment has been made.
Begin by setting the tension on the belt so that it is obviously loose; that is, so that the section of belt between pulleys can be pushed inward 5 mm to 7 mm (3/16" to 1/4") without much pressure being applied. Stamp a vertical test title and examine the results. The test title should be sufficiently long to examine a large sample of character combinations. If the base line appears excessively wavy, then increase the belt tension one half turn (clockwise) on the adjusting screw and stamp the test title again. Continue adjusting and testing until satisfactory results are obtained. After the final adjustment is made, be sure to tighten the forth motor mounting screw.
