Definitions of common terms.
Camco & Ferguson Product Cross-Reference Chart can be found here.
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What is indexing?
Indexing, whether linear or rotary, as defined by IMC is the process of starting and stopping in precise
intervals at precise locations.
How do cam driven indexers work?
Typical cam-driven index drives have two basic elements: a cam attached to
the input shaft (camshaft) and a follower wheel attached to the output shaft.
As the cam rotates, followers on the follower wheel are guided through a path
dictated by the shape of the cam.
During part of the input rotation, the cam
confines the followers (and therefore, the output) to a rigid, stationary
position called dwell. During the remainder of the camshaft rotation, the cam
geometry caused the followers to move and the output to rotate. This movement
is called an index. As the camshaft is rotated at a constant velocity, the
output stops and starts (dwells and indexes) in a repeating pattern.
Why should I use cam-actuated indexers?
Cam-operated indexing systems move a wide variety of products and components with precision. They offer controlled acceleration and decelerations with smooth motion, quick settling time in the dwell position, the capacity for high loads and high speeds, as well as repeatable, accurate positioning. They come with a known displacement-time relationship and known power requirements, and require little or no maintenance.
Why should I use IMC cam-actuated indexers?
IMC's equipment and manufacturing techniques represent more than 100 years of manufacturing and engineering expertise and allow us to maintain an unprecedented level of quality. We have a wealth of experience in developing the best solutions for a wide variety of applications, and our engineering staff, catalog information and proprietary software help ensure every customer has the optimum solution for each application.
- B10 Life of 8000 Hours: All IMC indexers are designed and rated to have a B10 life of 8000 hours minimum on the cam followers and over 100,000 hours on other major components.
- Precision Parts: IMC cams are hardened and manufactured for the best accuracy and durability. Shafts and flanges are oversized to maintain torsional rigidity. Cam followers of the highest precision are used to insure smooth operation, high accuracy and long life.
Ideal Index Motion Curve
Controlled indexing includes three phases: acceleration, peak velocity and deceleration. Cycloidal, modified sine and modified trapezoidal motion profiles are among the standard types of motions used to optimize transition from one phase to the next, although special polynomial curves can be developed for specific applications.
IMC most often employs modified sine curves because of their smooth transitions and power demand curves. Modified sine constant velocity is used when a period of peak, constant velocity is required. For an oscillating motion with no dwells, IMC uses modified sine quick return (MSQR); for oscillating applications with dwells at only one end of the stroke, we use synthesized modified sine harmonic (SMSH).
What types of index drives does IMC offer?
IMC offers all three types of index drives:
Roller Gear Indexers use a globoidal cam in conjunction with followers mounted radially outward from the circumference of the follower wheel. The input shaft is perpendicular to the output shaft.
Roller gear index drives are compact and low-profile and have motion flexibility due to relatively large cams. They have flanged output capability for dial mounting applications , through-hole capability and 2 to 24 stop range.
Right Angle Indexers use cylindrical or barrel cams with followers mounted parallel to the axis of the output and the input shaft perpendicular to the output shaft. They are the most compact design for a given output capacity, with the cam tucked partially under the output wheel.
Right angle indexers provide a fixed center distance between the input and output shafts, flanged output capability for dial mounting application, through-hole capability and 3 to 24 stop range. In addition, they feature very large index drives for automotive assembly and large (up to 40 feet) dial diameters.
Parallel Indexers use pairs of conjugate plate cams with yoke-mounted followers parallel to the axis of the output. The input and output shafts are parallel, in a configuration that means there are no ribs on the cam and no reversal of the cam followers.
Rates of more than 1,000 indexes per minute are possible with parallel indexers, which also provide high torque, high load and high-speed capabilities. Additionally, parallel indexers are more resistant to shock loading and have motion flexibility because of the conjugate cam geometry. The stop range is 1 to 8.
What is the difference between cycle-on-demand and continuous run?
With cycle-on-demand, the camshaft or input shaft stops on dwell for the time specified for a particular manufacturing process and then restarts. If the camshaft runs continuously, the index time and dwell time are fixed.
How does IMC measure indexer accuracy?
IMC states the maximum error as an indexer's worst possible accuracy, rather than using the average as the stated accuracy and declining to state repeatability. On request, IMC can provide special accuracy reports for particular indexers.
How do I know vibration isn't a factor in my application?
IMC's loading programs automatically ensure that the amplitude of vibration is less than 25 arc seconds in 25 percent of the dwell time - a criterion that IMC has developed to effectively predict vibration effects. IMC's loading software program, used in conjunction with recommended input and output connection methods, allows customers to avoid vibration effect in specific applications.
Does IMC take emergency stops into consideration when selecting an indexer?
While an emergency stop can occur during any part of the index motion, computer analysis is required to determine the point at which an emergency stop will put the least stress on cams and other components. IMC engineers will, on request, evaluate stresses and maximum expected stop times for specific applications. We recommend certain types of drive packages and clutch brakes for applications with emergency stop requirements. Consult your IMC sales representative or application engineer for more details.
How can I protect my IMC equipment?
Overload clutches protect indexer drives, which are subject to tremendous stress and potential damage at the very beginning of an index. IMC offers a wide range of both input and output overload clutches that accommodate shaft-to-shaft, flange-to-shaft and dial applications. On certain models, we also offer internal overload clutches to protect the clutch from foreign contamination. IMC overload clutches for indexing applications have single position reset to ensure accuracy and repeatability.
What lubrication is used in IMC equipment?
IMC index drives require high-quality, well-refined lubricants with extreme pressure additives. We ship index drives without oil to avoid potential leakage in transit, but provide a "bulls eye" oil level sight gauge and instructions for fill levels with each drive.
Lubricants must meet these specifications: MIL-PRE-2105E or SAE 80W-140, ISO220 or AGMA5 with extreme pressure (EP) additives. Units that use grease rather than oil are shipped with the grease. Generally, IMC uses lithium grease such as Mobilith AW-2.
What are axial, radial and moment capacities?
One of an index drive's load capacities is based on the bearings that support the output. Load conditions that may be present include:
- Axial capacity is the maximum balanced load the indexer's output bearing can support
- Radial capacity is the maximum side load of the output bearing
- Moment capacity is the maximum overturning or unbalanced load capacity of the output bearing.
Exceeding the capacity for any of these forces can cause permanent damage. Contact IMC engineering for analysis of applications with special requirements for any of these conditions.
How do I drive my IMC indexer?
Speed variations in the input shaft will be amplified on the output shaft, making it very important to have a controlled motor speed and reducer ratio that will dampen any variations. Any input belts must be tightened to prevent slipping or jumping during torque changes, and pulleys should be maximized to the largest diameter the camshaft will accommodate. See your IMC sales representative or application engineer for additional information on input speed control.
How do I connect my IMC indexer to what it is driving?
Indexing always applies positive and negative torque on the driven members. Therefore, all connections should be tight and doweled if possible. Shaft couplings should have an interference fit rather than depending on the keyway for tightness. Clearance in the keyway or key stock will eventually cause the connection to loosen.
||The statistical life for 90% of the cam followers functioning at their designated performance level at a given speed
||The total number of degrees during one cam revolution where the output is stationary.
|*** The sum of the index period and dwell period is always 360° ***
|Index cycle time
||For continuous running applications, the amount of time required to execute on index cycle (one dwell + one index) in seconds. The terms "Cycle Time" and "Total Cycle time" are used synonymously with Index Cycle Time.
||The time rate of index cycles, expressed as cycles per minute. Either the Index Rate or the Index Cycle Time can be given to adequately define the speed of the indexer output.
||The number of index cycles per revolution of the camshaft expressed as an integer. The vast majority of indexers use type 1 cams. A type 2 cam would have 2 complete dwell/index cycles per revolution of the camshaft. Note that the cam type does not affect the values of index period or dwell period.
|Weight Moment of Inertia (Wk2)
||A basic property of any object or system, it quantifies an object's resistance to rotational acceleration. This value is also supplied for the output assemblies of every indexer model offered by IMC in the product section.
||The maximum torque applied to the output as a result of the acceleration of the total inertia of the output. The total inertia includes the inertia of the indexer as well as the inertial of the attached masses.
||The maximum torque applied to the output by friction forces on the output. The value can be estimated or found empirically .
||The maximum torque applied to the output as a result of work being performed by the output during index. Possible sources of the work may be springs, cutting forces, gravity, etc.
|Total Output Torque
||The maximum amount of torque applied to the output by all forces together - the sum of Inertia Torque, Friction Torque, and Work Torque.
||The amount of torque needed on the camshaft (input) to overcome all external and internal loads.