Rotary indexing table is a widely used machinery in automated assembly. This article focuses on reviewing one of the very popular devices – the cam indexer – that can be used for rotary indexing.
A cam indexer, also referred to as the cam splitter or rotary indexer, is a ubiquitous mechanism for intermittent motion of rotary tables. The cam indexer is characterized by the large transmission torque, stable operation, high indexing accuracy, compact structure, self-locking capability, small size, low noise, high speed and superb longevity. It serves as an ideal replacement for the traditional mechanism, such as the groove wheel mechanism, incomplete mechanism, etc.
Cam indexers are suited for applications in which the same angles are indexed and high precision position is required at a very affordable cost. A cam indexer utilizes a mechanical cam to position the load by providing motion control. It is coupled with a mathematical motion curve in order to provide exceptionally smooth and repeatable motion.
A cam index can typically be switched between two modes of operation: the cycle-on-demand mode and continuous mode.
In cycle-on-demand mode, the output is advanced one position at a time as the camshaft is cycled one revolution at a time. Usually, this is accomplished by using an inexpensive camshaft sensor kit to detect the location of the camshaft and a VFD to stop and start the engine. The camshaft dwell period provides a large window for the camshaft to halt without impacting the position of the output.
To cycle the rotary indexer is this mode, the VFD receives a command from a PLC to speed up the drive motor to a pre-programmed speed, the cam rotates one revolution to index the output, the sensor delivers a signal to the PLC, and then the PLC communicates with the VFD to stop the camshaft during the cam dwell position. The table will remain in dwell position for as long as the work is completed at each station.
Following the above, the dwell time can vary from a few seconds to several minutes or our based on the application. This leads to an outstandingly accurate positioning paired with an affordable drive system.
In the traditional continuous mode, the camshaft of the rotary indexer spins at a constant speed, while the dwell time and indexing are controlled exclusively by the cam motion profile. Continuous mode is useful when the indexer is required to run at cycle rates faster than a motor can be started or stopped, or when the other equipment are to be synchronized mechanically with the camshaft timing.
Using an easy-to-understand language, in the world of machine design, cam indexing basically the movement from a primary position to a new position, start and ending in rest. So what kind of applications does a cam indexer actually entail?
Cam indexers are essential in manufacturing, namely mass production, wherein a well-defined cycle of motions are required to be repeated quickly and precisely for each interchangeable part that is produced.
Without a rotary indexer, all manufacturing operations would be undertaken using the fundamental crafting methods. Just imagine how much unit cost would be incurred for all the time and expertise invested into producing each unit of interchangeable parts.
Some of the major advantages of cam indexers include:
● Inertia and Weight Capacity: Cam indexers have adequate weight capacity and are capable of handling the highest inertia systems.
● Repeatability: Cam indexers are known for being exceptionally repeatable and the ability to offer consistent result. As aforementioned, cam indexers specially excel in situations where motions need to be repeated quickly, easily and precisely.
● Simplicity and Cost Effectiveness: Cam indexers are also known for their simplicity from both configuration and operation point of view. First and foremost, cam indexers are structurally simple, composed of only two parts – a stereo cam and a split disk. Also, cam indexers are easy to maintain and operate, which eliminate need for a highly skilled worker to manipulate the machine.
● Stability: Cam indexers are characterized by the stable transmission. The three-dimensional cam curve yields smooth and continuous transmission, small vibration, hence the low noise level.
● Speed: Cam indexers feature superb high-speed performance. They are known for being able to move heavy loads at a fast speed compared with most electronic systems. The splitter stereo cam and the split wheel constitutes the non-gap meshing transmission, which translates to minimal vibration while being able to achieve a high speed of 900 RPM.
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