# Rotary indexing table and moment of inertia

A rotary indexing table moves your payload on a "disc" by pneumatic accelerating. For the later on locking, e.g. to enable the following operation on the workpiece, the retard of kinetic energy also is a valid player in each cycle.

When chosing the rotary indexer,  not only "pure load "is the topic, but the position of the load and the location of load compared to the center. The valid pyhsical size is the moment of inertia "J".

Every workpiece inerts turning around a center and inerts every change of angle speed! The moment of inertia depends on the distrubution of mass in relation to the turning center. That means: shape, material (density) and mainly the distance to the rotation axis affect the situation.

Harmful: distance to rotation axis has a quadratic relationship in this formula of physics. In other words: if the mass is near to the center, there is less moment of inertia to handle.

As most often your workpiece is a stated fact, the moment of inertia can be influenced in the construction by

• distance to rotation axis
• design of workpiece-holder
• design of table / disc, the workpiece holder is fixed on

Example 1

Table/disc * partition 4

 kind of disc, material thickness diameter weight moment of inertia full slice, steel 10mm 200 mm 2,45 kg 122,5 kgcm² full slice, steel 10 mm 250 mm 3,83 kg 299,1 kg cm² full slice, steel 10 mm 300 mm 5,51 kg 620,3 kg cm² full slice, aluminium 10 mm 300 mm 1,91 kg 214,7 kg cm² full slice, PA6 GF15 10 mm 300 mm 0,87 kg 97,8 kg cm² cross, steel 10 mm 300 mm, B=25mm 1,17 kg 88,4 kgcm²

Example 2

workpiece, cylinder D = 30mm, length = 100 mm, full material

 material weight distance to rot. axis J cross rot. axis J along rot. axis steel 0,55 kg 0 mm (central) 4,91 kgcm² 0,62 kgcm² steel 0,55 kg 50 mm 18,7 kgcm² 14,4 kg cm² steel 0,55 kg 100 mm 60,1 kgcm² 55,8 kg cm² steel 0,55 kg 200 mm 225,4 kgcm² 221,2 kg cm² steel 0,55 kg 300 mm 501,1 kgcm² 496,8 kg cm²

A low monet of inertia can maybe be handled by the smaller rotary indexer  - less space and less costs!

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