US firm Engis Corporation has just released a new three-axis single-pass bore finishing system, the FPM-3X which can finish stacked valve body bores to a cylindricity of 2 microns and a diameter of +/- 1 micron, especially those with multiple bores and bores of different diameters.

This development is in response to the needs of manufacturers of earth moving equipment and construction machinery using large hydraulic valve bodies. A major challenge faced in this industry is the precision finishing of hydraulic valve bores, in particular aligning and finishing the bores once the bodies have been stacked.

Engis says FPM-3X is the solution to the challenge.

The FPM-3X features full CNC controls with a Z-stroke of 750 mm, an X-stroke of 1066 mm and a Y-stroke of 100 mm. The slide base can accommodate parts up to 3,000 lbs. An 8 - 13 pocket automatic tool changer allows the machine to complete bores from rough to finish without operator involvement. Programming is done via standard G-Code.

Using a systems approach, Engis helps manufacturers optimise bore finishing results by selecting the best combination of superabrasives, tool design, tool holding, part fixturing, cooling/filtration and automation package options.

Traditionally, manufacturers finish each valve individually and then stack valves together. Unfortunately, the torque subsequently applied to the stack distorts bore geometry.

'Valves are the heart of heavy equipment hydraulics,' says Engis product manager Robert Marvin. 'They coordinate the flow of fluid. Bores with cylindricity problems may experience fluid leakage, premature wear or other failures.'

Renishaw CMM probe

The FPM-3X enables bore finishing after stacking the valves, which improves cylindricity and roundness. To precisely locate the bore under the BT-40 spindle, the FPM-3X uses a wireless Renishaw CMM probe to establish bore location; position information is automatically translated into G-Code coordinates.

Marvin notes that the FPM-3X also addresses other shortcomings of traditional bore finishing approaches. One approach is to finish the bores on a large indexing machine or in a series of machining cells.

'These options offer good accuracy and throughput, but are usually dedicated to high-volume part runs,' he says. 'Conversely, the FPM-3X provides significant flexibility. An operator can run a one-off part and change to another part fairly quickly.'

The FPM-3X also increases quality compared to conventional bore honing, where the abrasive tool expands. Engis’ single-pass process removes material by using progressively larger tools in ever-reducing increments with progressively finer diamond size.