Operation |
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| The complex geometry of the internal mechanism of an indexing table allows the transmission of motion from the drive shaft to the output flange accurately and without play. There are 3 main types of mechanisms and their endless varieties: | ||||||||||||||||||||||
Mechanical indexed cam – short-indexing |
Mechanical indexed cam – long-indexing |
Conitinuous cam |
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| The short indexing cam is typically used in processes where the drive is a conventional electric gear motor, which is turned off at each indexing, keeping it off until all processes are performed on the automation. These processes usually take much longer than the indexing time of the table, for instance, 1 second of rotation and 20 seconds of indexing.
The inductive sensor of the indexing table signals the optimal time for the PLC to turn off the gear motor, so that when the gear motor fully decelerates, the output flange is in the indexing position, which is visibly observed by the yellow pointer within the green range. The geometry of this camshaft will be responsible for the smooth acceleration and deceleration ramps, as well as the angular distance and accuracy of the output flange. The animation above represents a camshaft of 12 stations (indexing every 30 degrees) with a time ratio of 85% rotating and 15% indexed. |
The long-indexing cam is typically used in processes where the drive is a conventional electric gear motor, and it does not turn off after each cycle. In this way, the “indexing zone” is a proportion of the time of each cycle.
Some industrial processes, like food filling, allow for this type of mechanism since the rotating time and indexed time are known and unvarying. The animation above represents a camshaft of 12 stations (indexing every 30 degrees) with a time ratio of 40% rotating and 60% indexed. |
The continuous cam is usually used in processes where the drive is a servo motor, where the table’s function is to transmit the drive’s rotation proportionally to the output flange, with extreme precision and free from play. The reduction of tables varies between 1:10, 1:12, 1:14, or 1:16.
Implementations often use variable angular distances, and the acceleration and deceleration ramps are under the responsibility of the servo motor and driver’s programming. The animation above represents a continuous camshaft with a 1:10 reduction. |
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| Advantages:
– Allows individual control of rotation time (using an inverter) and indexed time (keeping the motor off). – No need to create acceleration/deceleration ramps since these ramps are mechanically embedded in the camshaft geometry. – No need to program angular distances to be covered. – Smoother camshaft geometry. – Typically uses a conventional electric motor (single or three-phase). – Simple implementation. |
Advantages:
– Allows the gear motor to remain always on. – No need to create acceleration/deceleration ramps since these ramps are mechanically embedded in the camshaft geometry. – No need to program angular distances to be covered. – Typically uses a conventional electric motor (single or three-phase). – Simple implementation. |
Advantages:
– Allows programming of the angular distances to be covered, as well as the acceleration and deceleration ramps. |
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Legend |
Legend |
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