TPT November 2016

AR T I C L E

Advanced Machine & Engineering/AMSAW

Based on sophistical test results using a Data Acquisition Instrument, laser triangulation sensors and Bentley ® probes, we developed and patented a combination stabiliser and damper with the following characteristics: • Anti-friction rollers instead of stabilising plates, eliminating any heat build-up through friction. The rotating bearings transfer the heat by ventilation too. • A speciality-shaped damping ring contained between two anti-friction ball bearings. This ring is made of a special vibration-absorbing compound. • An eccentric device allows pre-loading the blade with the rollers from both sides of the blade. This eliminates the gap on the present devices between stabilising plates and the surface of the saw blades and makes the device especially stiff. • The eccentric adjustment and simple screw lock makes the device very user friendly and cuts the time for blade exchange to a fraction compared to the present devices on the market. Damping and thermal issues often go hand in hand For damping forces due to material deformation you need to use continuum mechanic models, which are complex because you have to solve a system of partial differential equation. Usually there is an interaction between mechanical and thermodynamic processes, since the material is heating up and many material properties are functions of the temperature. Plastic is a good damping material, which indicates that high frequency vibrations will create much heat. But plastic is also a good thermal insulator, which leads to the problem that heat might destroy the damper material if not properly sized. Simple calculations show that this aspect should not be neglected. Conclusion • If you cannot avoid that a forcing frequency is matching a natural frequency of the structure you should at least have high damping at this mode to reduce the problem. • Box ways are more expensive and more demanding on maintenance but have better damping that anti friction linear ways. Hardened roller elements rolling on hardened ways hardly dampen.

• There is a distinct difference between stabiliser and damper of a saw blade. A stabiliser constrains the saw blade but on the other hand a damper withdraws energy. • In general you have two possibilities. Either you have a sub- critical or over-critical operation. Sub-critical means that the forcing frequency is lower than the natural frequency and over-critical means that the forcing frequency is higher than the natural frequency. In the past machine tool builders always tried to be as low as possible with the natural frequency and so they added a lot of mass. This way they didn’t have to worry about the forcing and the natural frequency will match. According to Newton’s second law: when you have the same force that is causing vibrations and you increase the mass, the acceleration will go down. Nowadays with enhanced simulation and measurement equipment you have a better understanding of natural frequencies and you can avoid problems by the right balance between mass and ingenuity. Smart systems with a lot of modal damping will help too. This will result in a better, more cost-efficient saw.

Advanced Machine & Engineering/AMSAW – USA 2,500 Latham Street

Rockford, IL 61103, USA Website: www.amsaw.com

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N OVEMBER 2016