Determining how long a friction clutch or brake will last has much to do with application. Cycle rates, revolutions per minute and the air pressure required to produce the torque to drive or stop the load are just a few of the considerations. Assuming the unit has been properly sized and the application is not unusually rigorous, the majority of friction brakes and clutches will measure their service life in years as long as the manufacturer’s instructions for installation, operation and routine maintenance are followed. Mach III has compiled its recommendations for users who want to do all they can to ensure that the clutches and brakes installed on their machinery last as long as possible. Topics covered in the eBook, Make It Last, include:
- Proper Selection
- Proper Mounting
- Chain & Belt Alignment & Tension
- Environmental Considerations
- Routine Maintenance
Click Here or on the graphic to download the eBook.
While most clutches serve to engage and disengage a driving source to or from driven equipment, there are many possible variations – each of which requires varying designs. In order to select the best possible option, it is best to consider the following:
1. Primary Drive
Slip clutches can be used to provide constant tension in winding paper, film, foil, or wire when driven slightly faster than the product line speed. The clutch slips at the desired torque value to match the process line speed. In these applications, care must be taken to minimize the thermal load on the clutch. The heat load is the product of the slip RPM and the torque setting. Slip RPM should be limited to the minimum in order to allow smooth slip. Excessive slip will lead to premature wear, erratic tension, and damaging heat build-up.
- Constant slip speed and torque
When the clutch is used to drive a tension roll or spool of constant diameter the slip RPM is constant and the thermal load is generally easily managed.
- Increasing slip speed and torque
When the clutch is used to drive a roll or spool on which the diameter is increasing with the build-up of material, the thermal load increases dramatically as the roll builds. As the diameter increases, the torque must be increased to maintain the required tension. If the clutch is driven at a constant input RPM, the increasing diameter will require greater and greater slip to match the line speed. The product of the increased slip and higher torque causes an increasing thermal load on the clutch.
Mechanical friction torque limiters and clutches are frequently used to limit the amount of torque between drive and driven components to prevent damage to either. These devices are designed to allow the friction elements to slip when the preset torque of the device is exceeded. The friction surfaces continue to slip until the excess torque load is removed.
- Frequent Overload Occurrence
Torque limiting devices are sometimes used in assembly equipment that requires a brief period of slip at the end of each cycle. For these applications, adjustability and long friction wear life are critical.
For many drive systems, the torque limiter is designed in to prevent damage to expensive drive components in the event of some unforeseen failure – and may never slip.
Means of Engagement
Consideration should be given to which means of activation is most compatible with the location, machinery, and duty.
- Mechanical Lever
- Pneumatic Pressure
- Hydraulic Pressure
- Spring (Power off engagement)
All clutches and brakes have a specified torque capacity which may be fixed or variable. Based on the individual designs, they can have very different values of the following precision characteristics.
- Torsional Stiffness
- Positional Accuracy (Single position, Multi position or Infinite)
- Constantly Engaged (Primary machine drive)
- Cycling (Indexing, packaging)
- Idling (Backup drive)
- Typical Electric Motor Speed (1750 RPM)
- Typical Reducer Output (Less than 1750 RPM)
- High Speed (Greater than 1750 RPM)
- Controlled Temperature/Dry
- Wash Down
- Exposed to the Weather
- Extreme Temperatures (Hot or Cold)
- Exposed to Harsh Chemicals or Lubricants
- Food Safe
Like the brake pads in your car, the friction linings of a clutch, brake, combination clutch-brake or torque limiter wear over time. The period in which this will occur varies widely by application. We have seen units in operation for 20 plus years with the original friction linings. On the opposite end of the spectrum, linings can fail in a matter of months due to extreme operation, overload or air system failure. (Click here for more info about service life.) Whether the wear is gradual or sudden, the end result is the same; a machine component which no longer functions.
Unless the unit has slipped excessively and overheated, it can typically be restored to operation with the installation of a repair kit. Mach III offers repair kits which contain all the typical wear parts; friction discs, springs, o-rings, and related pins and screws. Rush order repair kits will typically ship the same day and overnight freight service will have the kit on your dock the following morning.
However, what happens when waiting even one day is not an option? Customers who are forced to use a same-day air or courier service typically pay four to six times the price of the repair kit - just on freight charges! Add the cost of lost production and this quickly becomes one pricey life-lesson. If the operation of a clutch, brake or torque limiter is critical, avoid this worst-case scenario and stock a repair kit at your facility.
For information about repair kits for the Mach III units in your facility or in the facilities of your customers, please contact customer service toll free (866-291-0849) or by email. It will be helpful if you know the Mach III product number or numbers when you call or email. Click here for a guide to finding the Mach III product number.
Clutches are commonly connected to a drive system through roller chains and belting. This requires that a sprocket or pulley be mounted directly to the clutch. A pilot style clutch is made for this purpose; providing a projection onto which the sprocket or pulley will seat and a series of tapped holes along a bolt circle where the sprocket or pulley will be attached. Use the link below to download the Mach III Ebook which explains the factors which must be taken into consideration when selecting, machining and mounting a sprocket or pulley for a pilot style clutch.
MachIII_Ebook001.pdf (540.58 kb)