It is essential to design a device that has to meet a certain vibration level. Ideally, the desired vibration response must be clearly stated before a design can begin. Many different methods have been proposed to measure and describe acceptable levels of vibration in many different areas including building structures, power tools, cars. Vibration measurement should be established in terms of displacement, velocity, or acceleration, and how a device should be measured needs to be clarified. These measurement selections often depend on the specific application. It is generally accepted that the best indication of potential machinery damage is the amplitude of the machinery’s vibration velocity. Acceleration amplitude is the most perceptible by humans, for example acceptable level of vibration in angle grinders is 2.5m/s2 for 8 hour use. Some common ranges of vibration frequency and displacement are given in Table.
The International Organization of Standardization, ISO and European Union directives, EU directives provide a published standard of acceptable levels of vibration that has the intent of facilitating communications between manufacturers and consumers. Manufacturers and consumers should be aware of minimum vibration levels to avoid harmful use of a device. It is required that manufacturers state product’s vibration level on the product manual. Standards for vibration require products to be tested in terms of root mean square, rms values of displacement, velocity, or acceleration. Rms value is the square root of the mean of the square of the values. Please note that vibration level requirement described in Standards is minimum vibration level requirement.
Vibrations are harmful and damaging, and they exist in some devices such as angle grinders and an unbalanced tire on a car. The difficult issue for design engineers is deciding between acceptable levels of vibration and those that will cause damage and/or become so annoying that consumers will not use the device.