Cam Indexing Drives & Rotary Indexing Tables

A cam indexing drive converts continuous input rotation into precise intermittent output motion with a defined dwell, using a globoidal or roller-gear cam. VR Automation supplies and integrates cam indexing drives and rotary indexing tables in 4, 6, 8 and 12 station configurations for special purpose machines and assembly automation, from Bhosari, Pune.

How a cam indexer works

The input shaft carries a barrel cam with a helical rib machined into it; the output shaft carries a turret with cam followers around its circumference. As the input rotates, the rib engages successive followers and drives the turret through one station — then the rib runs flat and the turret dwells, held positively between followers, while the input keeps turning.

Two things follow from that, and they are why cam indexers remain standard in high-rate assembly despite servo alternatives. First, the motion profile is machined into the cam, so acceleration and deceleration are inherently smooth — no shock into the mechanism or the part. Second, the dwell is a mechanical lock, not a held servo position, so the table cannot be pushed off station by the force of a press or welding operation acting on it.

Cam indexer versus servo indexing

Cam indexing drive Servo indexing
Station positions Fixed by the cam Freely programmable
Dwell Mechanically locked Held by the servo loop
Repeatability at high rate Excellent, unaffected by cycle rate Good, degrades as rate rises
Resistance to process force High — positive lock Depends on holding torque and brake
Changing station count Requires a different cam Software change
Control complexity Single motor, no feedback loop Drive, feedback, tuning

The short version: choose a cam indexer when the station count is fixed, the cycle rate is high and the process pushes on the table. Choose servo when station positions must change between products.

Types and mounting styles

  • Globoidal (barrel) cam index drive — the standard high-precision arrangement, with the cam rib fully enveloping the follower turret.
  • Roller gear cam indexer — roller followers running on a cam rib, giving low friction and long life at high cycle rates.
  • Flange model indexer — output flange facing up, for mounting a rotary table or dial plate directly.
  • Table model cam index drive — supplied with the rotary table integrated, ready to receive fixtures.
  • Sandwich model indexer — compact housing where vertical space is restricted.
  • Parallel and right-angle shaft arrangements — selected to suit the drive motor position in the machine layout.

Selecting an indexer

Stations Index angle Typical application
4 station 90° Load, two operations, unload
6 station 60° Assembly with in-process check and reject station
8 station 45° Multi-operation assembly, higher output
12 station 30° High station count, short dwell, packaging and high-rate assembly

Beyond station count, sizing depends on the inertia of everything the table carries — dial plate, fixtures and components — the index time required, and the overhung and axial loads applied by the process stations. Under-sizing an indexer shows up as follower wear and position drift long before it shows as failure, so the inertia calculation is worth doing properly at design stage.

Cam indexing drives are integrated into our rotary SPM systems, index riveting machines and auto screwing cells.

Cam indexing drives and indexed machines

Frequently asked questions

What is a cam indexing drive used for?

A cam indexing drive produces precise intermittent rotary motion with a locked dwell period. It is the drive at the centre of rotary indexing tables in assembly automation, special purpose machines, packaging machinery and multi-station riveting, welding and screwing cells.

What is the price of a cam indexing drive in India?

VR Automation cam indexing drives are currently listed from around ₹1,05,000, with price driven by unit size, station count, mounting style and the table inertia it must handle. Send your station count, index time and the mass and radius of gyration of the dial plate and fixtures for a firm quotation.

What is the difference between a globoidal cam indexer and a roller gear indexer?

Both use a barrel cam driving follower rollers. In a globoidal indexer the cam rib envelopes the turret over a wide arc, engaging several followers for high rigidity. A roller gear indexer emphasises low-friction rolling contact for long life at high cycle rates. In practice most industrial indexers combine both principles, and selection is driven by load, speed and available envelope.

How do I choose the number of stations?

Count the operations in your sequence, then add a load station, an unload station and any inspection or reject station. Choose the next standard station count at or above that total. Adding a spare station is usually cheap at design stage and expensive to retrofit later.

Can a cam indexer be driven by a servo motor?

Yes. Driving the cam input with a servo or a VFD-controlled motor keeps the mechanical dwell and motion profile while allowing the index time and cycle rate to be adjusted in software — a common arrangement on machines that run multiple products at different takt times.

Send us your component drawing

VR Automation, Bhosari, Pune — riveting, clinching, press and special purpose machines. We quote against your part, not a catalogue.

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