Why Choose Cam Drive? Top 5 Advantages of Fixed Multi-station Rotary Indexers

Do you need to choose from the following three driving options for your production line in the field of industrial automation.

Servo Direct Drive – infinite flexibility, but high cost and complex programming

Pneumatic Indexing – lower cost, but limited precision

Cam Indexer – mechanical reliability with excellent cost-performance balance

For dedicated production lines requiring fixed stations-such as 4, 6, 8, or 16 stops-the Fixed Multi-station Rotary Indexer (often called a Cam Indexer) remains the most suitable choice. Because it combines cost and performance, and has excellent mechanical properties that electronic control systems cannot replace.

 

The primary reason for choosing a cam indexer over gear-driven or pneumatic alternatives is its mechanical rigidity and positioning accuracy.

What is Zero Backlash

In gearboxes or chain drives, to prevent jamming, there is a gap between the driving gear and the driven gear. This gap, known as backlash, results in "play" or "slop" at the output. Over time, wear increases this gap, destroying accuracy.

In general,a high-quality Cam Indexer utilizes a pre-loaded mechanism. The input shaft features a globoidal or barrel cam with a tapered rib that engages with cam followers (needle bearings) on the output turret. Because the rib is tapered and pre-loaded against the followers, there is zero mechanical clearance. The input and output are mechanically locked together.

performance metrics

At Hansheng Automation, we define precision by Arc Seconds (1 degree = 3600 arc seconds). For example, an error of 30 arc seconds on a 300mm diameter turntable results in a positioning deviation of roughly 0.02mm at the edge-thinner than a human hair.

Standard Precision: Our off-the-shelf rotary indexers deliver a repetitive positioning accuracy of ±30 arc seconds. This is sufficient for 90% of industrial applications, including bottle filling, pad printing, and general assembly.

Custom Precision: For demanding applications like semiconductor bonding or optical inspection, we offer customized grinding to achieve ±15 arc seconds.

Unlike servo motors, which rely on encoder resolution and feedback loops to "hold" position (often resulting in micro-dithering), a cam indexer mechanically locks into the dwell position. Once stopped, it is rock solid.

note: For applications requiring absolute repeatability without electronic "hunting," the pre-loaded mechanical structure of a cam indexer provides superior stability.

One of the most overlooked aspects of indexing is the motion profile. How the table accelerates and decelerates directly impacts the lifespan of the machine and the safety of the product being transported.

Disadvantages of Trapezoidal Motion

Many basic servo programs or pneumatic systems use a 'trapezoidal' velocity curve (constant acceleration). Although the calculation is simple, the curve will generate significant impacts at the starting and ending points of the motion (i.e., at the moment of switching speed stages, the acceleration undergoes a sudden change, resulting in extremely high impact). This is manifested as physical impact or vibration generated every time the workbench starts or stops.

The Cam Advantage --- The S-Curve

Fixed Rotary Indexers are machined with a specific mathematical law cut directly into the steel cam-typically the Modified Sine Curve (S-Curve).

This motion law ensures that the acceleration starts at zero, builds up smoothly to peak velocity, and tapers back to zero perfectly as it reaches the dwell angle. There are no sudden spikes in force.

No vibration: The smooth transition prevents shock loads, allowing the indexer to achieve cycle rates of up to 200 indexes per minute (depending on station count and load).

Although high-end servo systems can be programmed to simulate S-shaped curves, this requires complex tuning and high bandwidth processing. However, for Can Indexer, there is no need for additional processing, which is a unique hardware advantage.

In heavy industry sectors like automotive manufacturing or hardware stamping, the turntable is often subjected to significant external forces during the dwell phase. For example, a pressing station might exert vertical force, or a riveting station might exert side loads.

Mechanical Structure

Cam Indexer is completely different from belt drive or direct drive systems in terms of structural integrity.

Output Turret: The output flange is supported by massive, widely spaced bearings (often cross-roller or tapered roller bearings) designed to handle high axial and radial moments.

The Locking Effect: During the "dwell" (stop) phase, the straight portion of the cam rib sits between the cam followers. This creates a mechanical lock.

Comparison of Load Handling

Belts/Chains: High elasticity. Under load, they stretch, causing positioning errors.

Direct Drive (DD) Motors: While accurate, DD motors rely on magnetic field strength to hold position. If an external force (like a drilling operation) exceeds the motor's peak torque, the motor will fault or move.

Cam Indexer: A standard DF (Flange) series indexer can easily support substantial loads.

For example, our DF-110 model specifications include:

• Axial Load Capacity: Up to 700 kgf (approximately 7,000N or 1,540 lbs) on the output shaft
• Maximum Indexing Torque: 700 kgf·m, suitable for heavy-duty applications like automotive part assembly or stamping stations
• External Shaft Load: Up to 480 kgf for peripheral fixtures

This mechanical strength far exceeds belt-driven or direct-drive systems of comparable size, making it best for applications involving machining forces during the dwell phase.

 

 

One of the strongest arguments for the Cam Indexer is its simplicity of integration.

The "Mechanically Programmed" Solution

A servo-driven rotary table requires:

• A Servo Motor & Drive.
• A PLC with motion control capabilities.
• Cabling for power and encoder feedback.
• Time: Programming homing sequences, defining acceleration/deceleration parameters, tuning PID loops, and debugging following errors.

In contrast, a Fixed Multi-station Rotary Indexer is mechanically programmed.

If you buy a 6-station indexer, one revolution of the input shaft will always result in a 60-degree output movement.

Simplicity in Operation

To run a cam indexer, you simply need a standard AC induction motor (with a Variable Frequency Drive for speed control) or a simple gear motor.

Input rotates continuously: The indexer cycles automatically.

Input cycles: Use a simple sensor on the input shaft to tell the motor to stop after one cycle.

The advantage of saving time by eliminating the need for programming and debugging. There is no need to re-home the machine after a power outage (the cam position is absolute). This simplicity drastically reduces engineering hours during machine commissioning and troubleshooting.

When calculating TCO, the combination of a moderate initial purchase price and near-zero maintenance costs makes the cam indexer one of the most economical choices for long-term production.

How do I calculate the correct size for my application?

Sizing depends on three critical factors: the Total Moment of Inertia (mass and diameter of your turntable + fixtures), the Target Indexing Speed (seconds per cycle), and the Dynamic Torque required. Using an undersized indexer can lead to cam wear. Hansheng Automation offers a free sizing service-simply provide your turntable specifications, and our engineers will calculate the safety factor for you.

Can the "Dwell Angle" be adjusted after purchase?

No. The dwell angle (e.g., 90° index, 270° dwell) is permanently ground into the steel cam. If your application requires changing the timing frequently, please consult us during the design phase.

What happens if the indexer develops play (backlash) over years of use?

High-quality cam indexers feature an eccentric adjustment mechanism. If minor wear occurs after years of heavy use, the input shaft housing can be rotated slightly to move the cam closer to the followers, effectively eliminating the gap and restoring the "zero backlash" condition without replacing the unit.

The three driving methods mentioned in the article each have their own advantages, but for large-scale production, the Fixed Multi-station Rotary Indexer is the better choice in terms of cost and performance. Below, Hansheng provides a comparison table for your reference.

Suggestion
Choose Cam Indexers for: Automated Assembly Machines, Packaging Lines (Filling/Capping), Pad Printing, Ultrasonic Welding, and Pharmaceutical Inspection.

Choose Servo for: CNC Machining centers or flexible lines where product spacing changes frequently.

At Hansheng Automation, we specialize in calculating the perfect indexer size for your load and speed requirements. Whether you need the heavy-duty DF Flange Series or the versatile DS Shaft Series, our engineers are ready to assist.

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• ISO 230-2:2014 (Referenced for our ±30 arc-sec testing standards).
• Rothbart, H. A. (2004). Cam Design Handbook. McGraw-Hill Education.
• AGMA (American Gear Manufacturers Association): Standards for Lubrication of Industrial Enclosed Gear Drives.