With the development of the 701S machining centre, Willemin-Macodel has introduced a quantum leap in the machining of small parts by fully exploiting the dynamics and rigidity of the delta kinematic for the first time. This was achieved through the reduction of moved masses and by leveraging powerful PC-based CNC technology from Beckhoff. This has enabled a 90% reduction in energy consumption and a reduction in the machining time by as much as a factor of 10.
The Switzerland-based company specialises in machines for small part machining. The systems are used in the watchmaking industry, medical technology and the aerospace industry, among others. Technical director, Denis Jeannerat explains, “Our core competency is in high-precision machines for full-process machining. Because fixing small workpieces has always represented a challenge, the same machine now performs all machining steps – without the traditional division of processes into turning, milling and grinding. The machine also takes care of the parts handling – the careful insertion and removal of the workpieces.”
A simple idea revolutionises micromachining
On the face of it, the idea behind the new machine sounds simple. The 701S micromachining centre features a delta robot that has been inverted. This robot moves the workpiece – a task usually handled by the tool carriage. The basic concept of the new machine is based on parallel kinematics with a delta structure, and has been implemented in the form of a workpiece carrier connected by three arms. The machining strategy of the 701S, which is designed for machining small workpieces (ø 52 x 32 mm), focuses on computationally intensive circular interpolation. The key characteristics include path accuracy better than 0,2 m, low sensitivity to temperature fluctuations, as well as very high precision and repeatability. A specially designed high performance motor spindle, with a maximum speed of 80 000 rpm and without tool holders, provides increased static and dynamic rigidity, very high balancing quality and a low radial runout (less than 1 m at the tool tip).
The openness of PC control has also proven helpful in the simple connection of a special vision-based tool measuring system. With its help, the tools can be measured at full speed, including radial runout. The measuring system can be integrated into the Beckhoff control computer simply by using appropriate PCI plug-in cards, thus providing the computer directly and quickly with large quantities of data. In addition to its high computing power, the C6920 control cabinet industrial PC (IPC) with 1,9 GHz IntelR CeleronR processor is very compact and therefore requires little space in the machine’s control cabinet.
CNC-specific software and operator interface
Apart from complex path calculations, the tasks of PC control also include controlling the speed and position of the high-performance spindle. A total of four axes – the delta robot and the spindle as an additional axis – are controlled extremely quickly. This makes it possible to perform special machining operations with the spindle, such as planing or deburring. This is implemented using TwinCAT CNC by means of a pure software solution running on an IPC with complete CNC functionality. TwinCAT CNC can operate with up to 64 axes/controlled spindles, which can be distributed to up to 12 CNC channels. In a CNC channel, up to 32 axes can be interpolated simultaneously, solving even the most difficult motion tasks.
For a CNC operator interface, the 701S features the customised CP7912 Economy Control Panel with a 38 cm touch screen as well as integrated DVI/USB extended technology which allows separation from the IPC by up to 50 m. Jeannerat adds, “The control panel makes the operation of the machine extremely convenient. Numerous functions are directly integrated, for example, via the electromechanical pushbuttons, which enables intuitive and very simple operation.”
Highly efficient micromachining solution
The combination of intelligent design and efficient automation has resulted in a highly efficient and compact machine with a footprint of only around 1 m².
Due to the reduced moved masses, it requires only 2 kW of power to machine a small part. A conventional machine requires 20 kW or more. Denis Jeannerat adds, “With very high path accuracy within 0,2 m – even at full speed – the 701S also achieves a value that is better than conventional machining centres by a factor of 10. A further advantage is the immense time savings in parts machining. Depending on the complexity of the workpiece, the machining time is reduced by a factor between 3 and 10.
For more information contact Kenneth McPherson, Beckhoff Automation, +27 (0)11 795 2898, [email protected], www.beckhoff.co.za
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| Fax: | 086 603 6868 |
| Email: | [email protected] |
| www: | www.beckhoff.com |
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