New IM-pAC AC motor drive optimized for cam-operated index applications

Camco-Ferguson introduces the IM-pAC AC motor drive, specifically programmed for cam-operated index applications.

"Customers desire reliable, maintenance-free motors and controls. AC technology eliminates the downtime normally associated with DC brush motors,” says Lou Wozniak, director of research and development at Camco-Ferguson. “The IM-pAC eases the transition from DC to AC.”

AC drives are cost-effective, efficient and energy-saving replacements for DC motors and controls, offering superior performance when used with low-inertia AC motors. With AC motors, there are no brushes to wear out, providing long life and reliability.

The IM-pAC is for use with motors up to 1 hp and either 240VAC or 480VAC. Other features include:

• Designed for cam-operated indexing applications
• Easy setup – factory preset parameters
• Simple connections – easy-access terminals with clear markings
• Up to 60 cycles per minute using high-performance AC motors
• Index times as short as 0.5 seconds
• 230 or 460 volts, 50 or 60 Hz
• Can be programmed with multiple speeds: faster speeds for standard operation or slower speeds for restarting after emergency stops
• Does not require external braking resistors
• Can be used to cycle a brake motor
• Replaces motor starter and cycling logic and allows speed adjustment
• A “Quick Start” manual for easy setup is included with all IM-pAC drives, along with user manuals in five languages – English, French, German, Italian and Spanish

For more information, visit the IMC "What's New" page.

What is indexer accuracy and repeatability?

Accuracy is the deviation of the indexed station (tooling station) from the perfect position of the station. To illustrate, let's consider a 12-stop indexer, with the 12 stations spaced like the numbers on the face of a clock. If we define the 1 o’clock position as “Station 1,” we measure the difference between the perfect position at Station 1 and the actual position produced by the output face of the index drive. When measuring accuracy, IMC-Camco-Ferguson usually rotates the output of the index drive six complete times.

Now, let’s take the example of an 18-stop indexer. The 18-station graph (see graph) represents the recording of 108 (6 X 18 = 108) data points. With this process, the same tooling station stops at Station 1 six times. The range of data points at a given station determines the Repeatability of the indexer.

IMC-Camco-Ferguson is conservative when stating accuracies. In the graph at right, the maximum deviation from theoretical occurs at Station 4 and the minimum occurs at Station 16. The total range is 44 arc seconds, so we state Accuracy for this index drive as +/- 22 arc seconds. As a rule of thumb, IMC-Camco-Ferguson lists Repeatability as one-half of the accuracy, or +/- 11 arc seconds in this case. In reality, for the chart shown, at Station 14 the Repeatability is much better than the stated rule of thumb.

In summary, Accuracy measures how close the indexer brings a station to the theoretical perfect position and Repeatability measures how accurately the indexer brings the tooling station back to the same position each time.

 

How is accuracy measured?

Accuracy is measured with a laser collimator mounted to the indexer. The laser collimator is accurate to two arc seconds and repeatable to one arc second. In some cases, a Coordinate Measuring Machine (CMM) is also used.

What are the major contributors to the accuracy of an index drive?

• Output bearing runout
• Follower wheel machining tolerances, including follower hole location, squareness, size and bearing pilot runout
• Cam followers, including shell runout and diametral clearances
• Cam rib runout, but only on continuous-run applications or on cams with more than one dwell per input revolution (e.g. Type 2 or Type 3 cams)
• Assembly preloads/fitting