Understanding Rotational Automation
Are you a manufacturer looking for QA equipment and solutions? Cam-driven indexers are a profitable way to ensure precision and improve quality assurance for your products. They take constant input and translate it into intermittent output through cam curvature.
There are several styles of cams, outputs and housings to choose from when designing your application. Choosing the right option can affect features like your application’s dwell periods, operation speed and mechanical indexer strength.
Many rotary index table end users need the flexibility of a fully programmable tool. You can couple a gearhead with an encoder to a servo motor or an AC motor and create your own custom programmable tool. Unfortunately, the physics of this method creates high inertia, making it difficult to achieve high accuracy.
Choosing a cam indexer is a much better option, allowing for full programization, consistency and accuracy. The ideal cam-driven indexer depends on your application.
As the name suggests, this type of cam indexer combines a servo motor with a barrel cam for extremely precise, controlled motion and indexing. The advantage of using an electric servo motor is a high degree of control over movement. This index table’s motion profile is not fixed and can be adjusted through input to the servo motor.
With a servo-driven barrel cam rotary index table, it is possible to deliver a wide range of table sizes with zero backlash and unparalleled accuracy. Servo-driven rotary indexers allow heavy inertial loads to be rotated in a very smooth and controlled manner.
Cam-driven rotary index tables use a mechanical cam system to cause table rotation. They have significant advantages over other types of rotary index systems like gear drives, such as no backlash and high accuracy. These systems are less flexible than servo-driven tables because their motion profile depends on the shape of the cam. To change the table’s speed and indexing, you must create a cam with a new physical shape.
If your application requires precise, repetitive motion and you do not need a flexible motion profile, cam-drive rotary index tables are a good choice. They have significant advantages over other types of rotary index systems like gear drives, such as no backlash and high accuracy.
There are several commonly used cam-driven rotary index table systems:
Indexers with barrel cams offer the greatest strength/size technology available. Depending on the application, a barrel cam can be modified to feature an extended dwell period — how long the machine waits before it moves again — and custom acceleration and deceleration profiles.
Barrel cams are used in conjunction with perpendicularly mounted cam followers. They are used in applications like rotary dial output, where multiple processes happen in sequence as a part moves around the cam’s circular path.
Flat, or disc, cams are valuable for their space-saving attributes and the potential to produce very long dwell periods and operate at high speed. The extremely compact profile and range of possible motion profiles make parallel indexers exceptionally versatile.
Flat cams can also produce one or more of the motions in a multi-axis unit.
The shape of globoidal cams is similar to barrel cams, but they offer different profiles — cam followers are added in a “star” configuration, and there are tapered walls in the cam’s grooves.
This profile leads to significantly less internal inertia than barrel cams. Although the internal workings differ, globoidal indexers can produce the same rotary table output as a barrel cam.
They are ideal for fast-paced applications that require rotary output, offering greater customization flexibility than barrel cams. However, they sacrifice strength to achieve this flexibility.
Cam-driven rotary table indexers are sometimes called “fixed indexers.” With a fixed indexer, the cam drives receive constant power input from the motor. This rotates the cam, which then rotates the output.
Based on the design of the drive, the output will have dwell periods — when the output is stopped — as well as acceleration, deceleration and peak velocity. Cam-driven rotary index tables have many advantages, but they will not meet the needs of every application.
Rotary index tables can also be “flexible” — flexible rotary index tables use a cam that has a constant lead. For these cams, the output is at a constant velocity if the motor runs at a constant velocity. Constant lead cams provide a high-precision mechanical transition of power to the output. Since acceleration and deceleration are still necessary, the logic controller for the index tables motor provides the necessary control.
Contact us at 248-743-9999 and speak with one of Motion’s engineers about your application to find out what cam-driven indexing can do for you.
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