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Taking the shock out of product handling processes

08 May 2018

Increased automation is delivering many benefits to industrial processes, including the ability to increase the speed of products as they transit to the dispatch point. These speed increases mean that greater care is required for the products as they are moved from point to point. Introducing industrial shock absorbers can offer a range of benefits to a business, including improved productivity and a better working environment.

John Marshall, Technical Manager at WDS, looks at the specification of industrial shock absorbers and how they can benefit many businesses.

Modern manufacturing and processing businesses are continuously striving to improve efficiency and productivity to keep ahead of the competition. One simple answer would be to speed up the production lines, but this brings additional challenges that include a risk of damage to the end products as they are transferred between stations. 

Design appreciation

Various types of device are available to decelerate or change the direction of objects including dashpots, springs, rubber stops and pneumatic components. However, none of them can match the performance of a hydraulic shock absorber that has been properly matched to the application.

Industrial shock absorbers are designed to gradually bring objects to a smooth stop without bounce-back or vibration. As such, it is important to select the most appropriate design for a particular application; this task is made easier by understanding the calculations involved and how they affect the design of the shock absorber.

There are two main categories of design – adjustable and self-compensating. Adjustable shock absorbers use a single, variable orifice connected to an adjusting wheel that is used to fine tune the performance of the component to the application. The working range of the component allows it to be adjusted to suit a change in operating conditions, enabling a more flexible production area.

The self-compensating design employs a double tube arrangement where oil is forced through small orifices as the piston retracts. The spacing and design of the orifices maintain a constant pressure on the piston to provide near linear deceleration. 

Selection criteria

Choosing between the two designs of hydraulic shock absorber requires some specific information about the application. Clearly the mass and velocity of the objects is necessary, but the propelling force and the frequency objects to be decelerated are key pieces of information. 

Where these factors are expected to remain constant, an adjustable shock absorber would be most appropriate. In this situation, the component can be set up to match the effective mass (me) and minimise any spike reaction force. 

In contrast, the self-compensating versions are able to function with a range of effective mass. Simply making a choice between high, medium or low speed applications and the shock absorber is designed to compensate for changes in mass, velocity and propelling force.

Having established the most appropriate design, it is important to determine the orientation of the motion – horizontal, vertical fall or rotary. From here it is necessary to start defining the numbers that are required to make the calculations required to pinpoint the correct model of shock absorber within the range.

Crunching the numbers

Hydraulic shock absorbers are specified according to effective mass, (W3) maximum energy per cycle (MEC) and (W4) maximum energy per hour (MEH). In order to arrive at these figures a few calculations are required:

W1 – Kinetic energy per stroke, mass only = ((m*v^2))/2 (Nm) v=impact velocity

W2 – Propelling energy per stroke = F x stroke (Nm)

W3 – Total energy per stroke = W1 + W2 (Nm)

W4 – Total energy per hour = W3 x No. strokes / hour (Nm/hr)

Depending on the application, multiple shock absorbers can be used in parallel and the values of W3, W4 and effective mass can be divided by the number of units being used.

Integrating industrial shock absorbers into a processing or packing line can reduce wear, vibration, noise and extend equipment life while also improving the working environment. The key is finding the right product that will deliver an exact fit and reliable service for your application. 

WDS offers a wide range of industrial shock absorbers each with full specifications and 3D CAD drawings to cover a comprehensive list of applications. 

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