Osai Controller is Key to Success of Patternless Project

A radical new design of machine, that eliminates the need for pattern manufacture in the production of prototype castings, has, at its heart, a five-axis 10/Series CNC controller from Osai.

The machine, now operational at the Castings Development Centre in Sheffield, is part of the ongoing EU funded CRAFT project to develop a fast and versatile casting production process. The machine directly machines bonded sand compacts at a very high speed, with both high dimensional accuracy and low operational costs. This makes the process ideal for small quantity and prototype production and completely eliminates the costly process of pattern manufacture.

"Our concept for the machine was very demanding in machine tool terms," explains Project Manager, Roger Wallis. "We needed speeds of up to 35 metres a minute in the x & y axes, plus networking, tolerances of ± 0.1 mm, when machining at finishing speeds, and the option of high speed polynomial control - and a standard Osai 10/Series controller, with polynomial algorithms has been proved to meet our requirements."

The five-axis 'dust-proof' machine is programmed off-line using Delcam's Powermill CAD/CAM package.

Capable of managing up to 24 processes and 32 axes simultaneously, the 10/385 communicates with Castings Development Centre's network via an Ethernet connection, pulling in CAD programs, for each component as required from a nearby PC that is used for additional buffer storage.

No special software is needed to run in the high-speed polynomial mode and data doesn't need to be interpreted differently.

The polynomial interpolation algorithms enable the maximum speed to be calculated for each spline segment calculated in the geometrical phase (depending on the programmed speed and the characteristics of the single axes involved in the motion) and for these constant speed sections to be linked with polynomial ramps.

"The networking with the Osai 10/385 is very easy. The open architecture is easy to use," says Roger Wallis. "We use the polynomial algorithm functionality where it is suitable and it produces very much smoother control, but often the standard control mode is more than adequate." The machine itself is relatively light-weight, to reduce the inertia of moving parts, and is an all-moving gantry design, which means that the workpiece is stationary, so that the inertia is always constant regardless of the component. These mean that the machine is optimised for high-speed machining.

The x/y axes are rated at 35 metres/min, the z axis being rated at 20 metres/min. When roughing, the machine uses a very rapid slicing motion for maximum material removal, and, for finishing, the CMS machine has been proven to achieve the required tolerances, far in excess of industry standard tolerances - effectively the thickness of a grain of sand! The project has been an unqualified success for the Castings Development Centre.

"Every aspect of the project has been examined in detail to produce a unique and exceptionally high performance machine, " concludes Roger Wallis, "not the least part being the Osai controller, which is superb!"

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