Clutches and brakes are electromechanical devices used to transfer rotary motion or hold a load in place. Although their actions are relatively straightforward, there are a surprisingly large number of variables to consider when choosing the most appropriate clutch or brake for a particular system. Taking these considerations into account in the early phase of an application’s design can be critical for meeting budgetary goals and achieving project objectives.
When selecting a brake or clutch from a product catalog, keeping these considerations in mind will help you determine if any modifications to the standard product are necessary in order to fit the needs of your application. In some cases, a completely new application-specific design may be required to ensure optimal functioning. The following are three essential criteria that should be taken into account when selecting or designing a clutch or brake for a system.
Determine the Function Required for the Application
When choosing a brake or clutch for an application, the first and most important factor to consider is the specific action that will need to be performed by the component. A clutch is typically used to connect or disconnect two in-line or parallel rotating shafts. A brake is used to statically hold a load or to perform dynamic stopping to a backstop, motor, or machine frame.
Determine Rotating Inertial Load
When starting or stopping a load, it is important to be aware of the amount of inertia in the system that is being reflected from other components back to the clutch and brake. Inertia, which measures the resistance of an object to changes in motion, is involved in the calculation used to determine the required torque for acceleration or deceleration. Understanding these factors will help to optimally size the clutch and/or brakes for a specific system.
Using the proper “Units of Measure” is critical when calculating the required torque for acceleration or deceleration. The units of dimension for mass moments of inertia are mass x length2. The moment of inertia, or rotational inertia, is the rotational analog to mass. It is important to note that, unless otherwise specified, the axis of rotation must be taken through the center of mass. Please refer to the illustration in our new eBook for more details and specific examples regarding inertial load.
Size the Clutch or Brake Appropriately to the Function
The following criteria should be used to determine the appropriate sizing of clutches or brakes for an application. It is important to note that certain high-performance installations may require additional considerations specific to the application.
- Function– The first step is to consider the function that needs to be performed (clutch or braking action).
- Size restraints– The clutch or brake should be sized according to its function (stop/start or hold) and should consider any potential sizing restraints (overall diameter, length, shaft size, and weight).
- Torque– The minimum required torque (and maximum, if applicable) should be considered.
- Load – The frictional load or inertial load that the unit must overcome should be taken into account.
- Voltage/Current – The voltage/current objectives of the system should be evaluated. This will often vary depending on the particular operating system surrounding the clutch/brake.
- Maximum RPM– The maximum RPM that will be required by the system should be taken into account. This value will likely vary depending on the actuation requirements of the whole system.
- Duty– Cycles per Minute (CPM) or motion profile should be considered.
- Environment– Environmental issues (temperature, debris, vibrations, etc.) that can impact clutch or brake function should be taken into account as they will influence the need for special protective coatings or other treatments to enable survivability/longevity under the given conditions.
- Static or Dynamic Engagement– Static or dynamic engagement requirements can help to identify the most appropriate friction device for ensuring success of the application.
- Life – The theoretical number of cycles/hours that must be completed before replacement or overhaul should be considered.
Benefits of Working with SEPAC
Choosing a brake and/or clutch that is best suited for a particular system can be complicated, especially for sophisticated or specialized applications. Involving the motion control experts at SEPAC early in the design phase of a project will ensure that all of the relevant factors surrounding your specific application are carefully thought out. We work closely with customers to plan and design electromagnetic clutch and brake solutions that are built to comply with performance specifications, budgetary objectives, and delivery schedules. When working with us, you can be assured that the appropriate time and attention to detail will go into designing a clutch or brake that is tailored for your application.
To see our complete list of 12 essential clutch/brake design criteria, please download our new eBook.