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Gears, brakes, couplings and engines
News Release from: Abssac | Subject: Abssac machined springs
Edited by the Engineeringtalk Editorial
Team on 25 May 2007
Springs machined from solid metal
Machined springs can provide very precise, linear deflection rates because virtually all residual stresses are eliminated.
Abssac of Evesham's machined spring products do not employ the traditional method of deforming a wire and around a set form to produce the spring The spring is actually machined from a solid piece of material, be it compression, extension, torsion or a lateral bending spring
When considering the dynamics of the machined spring Abssac looks at the six possible Cartesian co-ordinates and then the rotary (RO=rotation) ROTX, ROTY and ROTZ co-ordinates.
When applying the Cartesian co-ordinates to a traditional wound spring, it will try to deliver all six axis potentials when it is asked to move.
When applying the Cartesian co-ordinates to a machined spring it can be designed to be a single degree of freedom system or it can be machined to deliver multi-Cartesian axis potentials.
For example, some applications have demanded an accurate mixture of compression, lateral and torsional spring rates.
Machined springs can provide very precise, linear deflection rates because virtually all residual stresses are eliminated.
The machined spring also enables the designer to incorporate parts of the spring assembly into the single-part construction.
It is possible to have more than one spring coil in the single-piece construction or multi-start configurations, which deliver performance advantages.
In fact, the machined springs capability to be supplied in multiple start spring coil configurations takes the performance and reliability to levels not achievable by the traditional wound spring format .
Naturally, the most common configuration is the single start spring, which consists of a single continuous coil element, which starts at one end and terminates at the other end, much like its wire wound counterpart.
The double start or indeed a triple start spring has two or three intertwined continuous coil elements, still within the same single-part construction.
In effect, this puts multiple independent helixes in the same cylindrical plane, which provides enhanced spring performance.
On multiple start machined springs, virtually all internal moments are resolved within the spring itself and the double start machined spring configuration is the closest single Cartesian co-ordinate deflection part available with today's technology.
Most wound torsion springs can achieve a rate tolerance of around 15%, while the machined alternative can easily achieve a 10% on rate and can be tuned to +/-2% for the more demanding applications.
Both unwind and wind up torsion springs can be supplied and in both cases the spring rates achieved are as linear as the geometry will permit.
Abssac can incorporate any form of end attachment into the torsion spring.
In the wound torsion spring format, tangs are produced by bending the last portion of wire into a set position.
These tangs are bent inward or outward.
This not only limits the actual attachment designs available but induces high stress into this attachment area.
In the machined torsion spring the tang is integral and without stress, making it a far more rugged and reliable attachment.
Tang usage is designed to provide a moment on a torsion spring.
To accomplish this, a force at a distance is employed.
The spring provides the moment reaction, but there needs to be an additional reaction to the force.
With a machined torsion spring, the application of a moment is possible using a pure couple.
Machined springs are used in medical, aerospace, semiconductor and motor sport industries. Request a free brochure from Abssac ...
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