by Chris Kudla, Senior Application Engineer, ITT Enidine
Energy absorption products, such as shock absorbers and vibration isolators, can help maintain speed and throughput while keeping linear motion processes online with less downtime.
Within the automation industry, a linear motion system is most aptly characterized as a series of drives and guides that work in harmony to perform a precision motion task. Most linear motion systems rely on a complex array of subsystems to help move objects from point A to point B. Moreover, linear systems often experience a sequence of start and stop impacts and vibrations that can adversely affect an object during its travel time, making the entire operation more susceptible to costly failures and unexpected downtime.
As part of a holistic preventive maintenance plan, plant operators should look to energy absorption products that control kinetic energy and reduce vibration to help keep processes online with less failure.
As advances in technology help provide manufacturers with improved performance feedback, the constant demand for higher speeds, improved cycle times and increased meantime between failures continues to drive the industry forward. By using today’s most advanced motion control and vibration isolation products in linear motion systems, manufacturers will see improved accuracy and production with minimal damage from abrupt starts, stops, turns, precise locating and vibration.
When considering ways to control movement in a linear motion system, managing the kinetic energy behind the start/stop process is extremely crucial to maintaining an efficient operation. Without an engineered approach to managing this energy, production lines have a limitation on the speed of operation. Operating beyond this limit can lead to equipment downtime for unplanned repairs. For instance, as products move along an assembly line, there is an impact at each stop, which could cause damage to the product or reduce the life of the assembly itself. To add an additional layer of complexity, products can also increase or decrease in weight at different points, which affects the amount of impacting energy.
Shock absorbers are used to cushion the impact at each stop. Tuning of the shock absorbers becomes critical in this application, considering the energy variations. Proper sizing and tuning of the shock absorber will result in the lowest transmission of impacting force to an object.
Case Study 1 — A major automotive OEM was experiencing excessive shock force on its nearly 1,000-lb assembly pallets as they stopped at each workstation down the line. The major hurdle was that the weight of the pallet almost doubled as it moved through each of the workstations having components assembled, creating a unique impact condition at each stop along the assembly line.
To improve the overall process, providing an ECO OEM series adjustable shock absorber, as seen in Figure 3, helped to manage the shock force within the assembly. To accommodate for the application’s weight variations, the shock absorber used a different setting at each stopping point on the assembly line.
By implementing the new product, the customer was able to reduce the transmitted shock force to the assembly line by an order of magnitude, significantly reducing downtime and improving overall efficiency.
Case Study 2 — Vacuum-operated pick-and-place robot systems in tire manufacturing rely on the forces generated through vacuum to lift the tire and move it to the next station during the molding process. When operated slowly, the shock induced at the end of stroke has very little energy, and the system functions properly. However, to increase throughput, the cycle times are reduced, increasing the impact velocity at the end of travel, leading to higher impacting energy. This impact energy can cause the tire to break free from the vacuum, stopping production and potentially damaging the product.
In looking for a way to increase throughput and reduce overall impacting energy, the manufacturer of the production molding equipment implemented ECO and PMXT series shock absorbers, as seen in Figure 2, for stopping the motion at the end of travel (the model and size is dependent on the type of tire). Through simulation of the impact event, the team generated performance curves and data to show that the deceleration and maximum allowable force requirements were being met, leading to a more reliable operation.
Today, tire manufacturers are experiencing faster cycle times without losing control of the product during movement.
Failures associated with vibration, such as loose bolts or broken welds, are often related to general fatigue or degradation of the assembly rather than one, abrupt movement.
In linear motion systems, vibration control products operate by decoupling the equipment from the vibration source, making it difficult for the vibration to make its way to the equipment. For example, vibrating tables are often used to transfer components and materials in many manufacturing processes, including linear motion systems. The frequency of the vibration causes the material being handled to subtly bounce around and flow across the vibration surface. Although this is an effective method of moving material and components in high volume production, the same vibration that allows for this movement can also damage the surrounding equipment. By isolating the vibrating assembly with wire rope isolators, Figure 1, the surrounding equipment is protected. Isolating the surrounding equipment from the damaging vibration prevents the loosening of bolts, breaking welds and damaging electronic components. This reduces downtime and improves productivity.
In addition to controlling vibration within a linear system itself, vibration control devices are also used to steady a system’s electronic components (the brains behind the operation), as they are typically expensive to fix or replace and can cause significant downtime if they are damaged.
Take, for example, monitoring cameras used to regulate equipment for operations and security purposes. Many overhead crane manufacturers rely on these cameras to control the entire production process. The motion of the cranes causes vibration, which is not only damaging to the cameras, but also impacts the clarity of the image. Moreover, the cameras are often mounted in difficult-to-reach locations and are exposed to severe environments. To help protect the equipment and stabilize the image, wire rope isolators are often applied to decouple the camera from the vibrations in the crane equipment. The rugged design of the isolators is ideal for severe environments, while keeping them maintenance-free.
When looking for a way to minimize damage and increase meantime between failures in your linear motion application, it is important to consider using energy absorption devices like shock absorbers and vibration isolators to control the kinetic energy of your system. By tuning your solution to match an application’s unique requirements, plant operators will see improvements in operational runtime, efficiency, product life and protection as well as overall profitability. On the manufacturer’s side, it is equally important to arm customers with the right tools and products to fully optimize their system for improved results.