By replacing traditional gearbox and motor assemblies with innovative gear technology in its machine tools, Coalville-based manufacturer Winbro has reduced the size and weight of tool heads, minimised backlash and improved the positional accuracy and repeatability of the machines.
"The Harmonic Drive system offers a number of important advantages over conventional gearbox and motor units," explained Chris Clements, project manager at Winbro, which manufactures high performance laser and EDM machining centres for producing specialised parts for gas turbines. He continued: "First, it is considerably simpler, lighter and more compact. Used on our latest laser systems, Harmonic Drive units used in conjunction with directly-coupled encoders allows us to achieve rotary accuracies of 20 arc seconds, with repeatability being 10 arc seconds."
Winbro requires accurate drives since the turbine parts its machines produce, such as blades and vanes, often have complex shapes and the cooling holes have to be drilled at precise locations on the surface of the component. Also, the geometry of each hole has to be accurately machined to produce the correct flow pattern.
The novel gear units, supplied by Stafford-based company Harmonic Drives, comprise three basic component parts: an elliptical 'Wave Generator', 'Flexspline' and 'Circular Spline', which fit one within the other to form an integrated unit that is easy to install and configure. The overall construction is very simple and allows each component to be used as the input, output or fixed part, enabling the gear unit to be used for reduction gearing, gearing for increasing speed, or differential gearing.
As well as using the new gear units on its tool heads, more recently, Winbro has incorporated the new Harmonic Drive FHA hollow shaft servo actuator into both the workpiece manipulator and laser head on its machines. This actuator has a large, central, hollow shaft, which allows the laser beam to be directed through the gear unit (or pneumatic, hydraulic and electric equivalents). It is available with an absolute position output shaft encoder, which provides direct measurement of output shaft position and eliminates the need for referencing. Its feedback systems are compatible with most major controller manufacturers.
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