The Rotary Indexer

The rotary indexer is a popular method, used in assembly automation, as a part transfer device. It consists of an aluminum dial plate, that is indexed in increments, very accurately, by a modular cam indexing unit.

Rotary Indexer

Aluminum is used for the dial plate, to minimize weight and inertia. To keep cycle times to a minimum, the index time needs to be at a minimum. Fixture weight also has to be minimized and aluminum is once again generally used. Hard anodizing the fixture can be done to keep wear to an acceptable level.

The Photo shows a rotary table, designed and built by the author. The part being assembled, is an automotive electronic assembly and combines a manual loading station with many automatic stations.

The auto-stations are ultrasonic welding, part testing and dot matrix marking and a pick and place robot unload, with an automatic reject feature.

Cycle times for this type of rotary indexer are generally at about 10 seconds per part, minimum and table diameter is usually less than 10 feet.(3.048M)

Automatic Stations

Auto stations can be whatever technology is required to assemble the part. Orbital riveting, pressing, robot soldering, direct part marking and bowl feed and pick and place robot stations are very popular.

Automatic testing of the completed part is also frequently accomplished. It is usual to automatically reject failed parts and ensure that only passed parts are allowed to progress further along the assembly path.

Manual Stations

Operators can be used wherever an automatic station is not used, due to technology restraints and/or economic justification. Remember to leave enough space for the operator as well as part storage.

Operator safety must always be paramount! Adjacent automatic stations must be non-accessible and protection must be given to ensure that operators are not injured by moving fixture or parts.

If you look carefully at the photo above, you will notice clear Plexiglas guarding, around the manual station (Closest to the camera). 

CAD Drawings

The general arrangement drawing, shown above, was designed by the writer and shows a typical rotary index application. If you click on the image you will see a PDF file, that can be printed, for your reference.

Modular Cam Indexing Units

The photo here shows a Sankyo Rotary Indexer. This is the unit that drives the table that is bolted to the output flange.

The unit itself is bolted to a base frame. On nice feature of this Sankyo 7AD unit, is that the overall height is low and nothing protrudes above or below, meaning that no holes need to be cut in the base plate or packing blocks added, to give clearance.

There is also a stationary flange. in the center of the rotary indexer, where a plate can be added for inside station mounting.

To size a unit, you must know the diameter of the table, it's total weight, the weight of the fixtures and parts and the radius of the approximate center of gravity of the fixtures and parts. The index time and dwell time must also be estimated. Note that the dwell time is the dial stop time.

This is the maximum time for all of the stations to complete their tasks. It is possible to stop the motor, to increase this time, but there is a limit to the number of stops and starts per minute, that a motor can take.

Fortunately, the rotary indexer manufacturers will help with the selection of one of there units. They do have the vast experience and usually have software, that makes this task simple.

Provision should be made, for a protection device, to safeguard the cam and drive. Obviously all automatic stations must be safely at "Home" position, before a table index can start. Despite all the safety provisions that are built in,

Murphy's Law says that what can go wrong, will go wrong, at some point! This is where a mechanical protection device can save a lot of destruction! Some kind of shear pin or mechanical clutch will disconnect the drive from the table.

Manufacturers of Rotary Index Units

Camco Ferguson have been manufacturing drives, in the USA, for a number of years.

They offer a comprehensive range of units and can offer assistance with unit selection, on a world wide basis.

Sopap is a French company, that make an excellent product. Units, selection assistance and service are available world wide.

International exchange rates can sometimes make these units very competitive, so take a look!

New! Comments

Have your say about what you just read! Leave me a comment in the box below.