Brakes are essential to diverse industries for slowing and stopping motion or holding various loads in place. Electromagnetic brakes specifically use the presence and absence of electric current and magnetic field to release or lock brakes into place, holding or stopping a load when the electric current shuts down. This type of power-off brake is applicable when you require high torque and quick response times, making them ideal for safety brake applications.
Like all varieties, electromagnetic brakes will suffer from progressive wear and tear. Read on to better understand brake wear and how to prevent it for longer-lasting and efficient functionality.
What Is Brake Wear?
Brake wear results from the friction and temperatures that braking systems create while slowing or stopping a load. Over time, these factors have a detrimental effect on brake components and their performance. To reduce wear, electromagnetic brakes use force and the appropriate friction materials to slow or stop action.
The design of spring-engaged brakes (SEBs) enables these electromagnetic brakes to minimize wear when they serve as static holding brakes, because power-off SEBs won’t sustain cycling or stopping wear. The good news is that coils and springs in a brake rarely cease working or fully break. When they do, it’s usually because of extreme environmental conditions or improper setup, but you can take steps to address these factors that result in wear.
Causes of Wear
Wear is inevitable in any braking system, with friction and heat being the leading causes. There are several scenarios in which wear generally occurs, such as the motor starting up prior to brake release, a brake engaging before its mechanism has a chance to stop, or an effort surpassing a brake’s torque routinely back-driving the mechanism.
Understanding the primary causes of brake wear can help you identify and prevent premature wear for improved brake longevity. These primary causes include:
- Excessively high temperatures. At friction surfaces, high heat causes a significant increase in wear rate. Such temperatures can come from various sources, anything from high ambient temperatures to slipping, high rates of cycling, or excessive voltage applications. This can quickly lead to fatigue and eventual breakdown in the spring material and insulation of a coil wire.
- Friction. Friction and friction material are necessary for mechanical braking systems to halt or slow loads, and wear happens most often in SEBs on mating friction surfaces. As a brake halts a load, shaft rotation transforms mechanical energy into heat, or thermal energy. This resulting heat and abrasion lead to opposing friction surface and metal plate wear.
- Cyclical damage. The repetition of a positive feedback loop can generate heat and friction, causing distortion in the metal plates for non-flat surfaces. This leads to a reduced contact area on friction surfaces, which concentrates energy onto smaller and smaller surface areas. As the temperature in those locations rises, so does the occurrence of wear.
- Unmanaged air gaps. When current flow is absent, a magnetic coil’s spring will push against the armature plate, forcing it into the floating friction disc. Torsional friction results, which passes into the hub and shaft. Once voltage begins to flow through the magnetic coil again, it creates a magnetic field that pulls the armature plate across the air gap, producing an air gap on each side of the disc with free-spin movement. Brakes may only partially release, and the resulting drag can cause it to self-destruct. You can prevent unmanaged air gaps by resetting the air gap periodically using the manufacturer-supplied Service Life Energy Value.
How to Avoid High Wear or Damage
When using electromagnetic brakes, familiarize yourself with their thermal capacity limitations to avoid wear or damage. Suppliers typically have a set upper mechanical energy limit for their brakes to indicate maximum energy and energy dissipation capacities. These two thermal capacity categories define how much energy a particular brake can absorb or dissipate on each stop prior to surpassing its temperature limit.
Using a pulse width modulation (PWM) controller can address root causes, decreasing heat buildup and energy consumption in continuous tasks while enhancing longevity. It’s also a good idea to use a dust cover to prevent debris from collecting on the friction surface.
Adjustable and protective power-off SEB designs can help, too. Adjustable air gap designs can prevent issues stemming from excessive air gaps. Using smaller air gaps facilitates brake release once a coil receives electric power, creating minimal wear allowance. Inspecting air gaps and readjusting as needed will help prevent brake failure.
Prolong Brake Life With Power-Off SEBs From SEPAC, Inc.
SEPAC has nearly four decades of experience developing and manufacturing innovative, custom brake designs and American-made motion-control solutions. Our reliable, highly configurable power-off SEBs are available in multiple sizes and torque ratings to best fit your unique application. Contact us today for more details, or request a quote.