Examine some of the solutions on the market today.
Rotary tables for parts placement can also be electronic, stepper-motor driven, or pneumatic. Accuracy and price are determining factors. Electronic and stepper-motor-driven rotary tables are more expensive than pneumatic ones, but they can move weight more accurately. Rotary tables can be of just about any reasonable diameter, allowing anywhere from two to 12 or more fixtures to be attached (Figure 1).
Some manufacturers have modular rotary systems with up to four independently adjustable machine-mounting stations. Depending on the application, one, two, three, or all four machines can be used simultaneously, turned off individually, and even rotated 180º on their mounts to operate alone. This allows more than one job to run at the same time.
Racetrack conveyors are standard equipment on many multicolor machines. Racetracks are pneumatically driven in most cases and can have several nests or fixtures. If necessary, cams can be attached to allow the nests to rotate in between stations for printing multiple sides on a given part. These systems are rarely used outside of the pad-printing industry.
Over-under conveyors are usually chain driven or precision-link mechanically driven. In most cases, parts simply fall off the nests into a container at the end of the line, or are transferred to separate conveyors for subsequent operations.
A few manufacturers use the bottom of under-over conveyors (Figure 2) for secondary operations. One in particular has under-over conveyors that present the part at a 30º angle after printing, rather than upside-down. This allows for easier access for post-print operations such as assembly.
Walking beams are a mechanical means of moving parts from one print station to another. Walking beams are limited in that they usually require that the part be picked up, moved over, and located against a stop of some sort for each printing operation. In most multicolor operations, it is not recommended that the part be moved in this fashion.
Hot-air dryers are common on racetrack conveyors and rotary tables. Even though most pad-printing inks dry to the touch within a few minutes, most people prefer to have the additional drying equipment, especially if they are using two-component ink or printing multiple colors with a lot of coverage, or at high speeds.
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