ADVANCED MANUFACTURING NOW Andrew Osborn
Michel Rottet
Product Manager Studer
Radius Grinding Gets a B-Axis Boost a M
anufacturers depend on grinders to process components with complex radii and other sphere- shaped features. The machines’ dressing systems
impart the desired part profi les onto the grinding wheels that shops then use for plunge-grinding operations. However, conventional radius wheel dressing is time consuming, costly and often diffi cult. Therefore, many of today’s manufacturers have swung their attention over to a relatively new process called pendulum grinding, which involves the interpolation of a machine’s B, X and Z axes simultaneously The pendulum process hinges on radius grinders with
advanced B-axis workheads that provide precise, smooth swiveling movement—much like a pendulum’s path only in a horizontal, instead of a vertical plane. With this capability, the machine grinds/interpolates convex radii, diameters, cones, transitional radii, spheres and other contoured shapes onto workpieces. But most benefi cial is that the machines use straight grinding wheels that eliminate the need to dress radius profi les onto the wheels. Radius grinders with B-axis capability reduce wheel costs and shorten overall part-cycle times while generating high- precision, superior surface fi nishes that often make second- ary hand-polishing unnecessary. The machines and their process contribute signifi cantly to longer wheel life. Dressing radii profi les on wheels shortens their working lives and makes it a challenge to maintain part tolerances and radius shapes. Without using the interpolating B-axis process, each shape also requires a unique grinding wheel. B-axis radius grinders, on the other hand, use the full width of a straight grinding wheel as it oscillates around the part surface, using only one wheel for even wear and shape consistency while generating perfect features. These straight grinding wheels still require dressing, but the process is faster, less involved, and uses only a standard dressing unit as opposed to an expensive, complex radius dresser . However, not all B-axis radius grinders are created equal.
B-axis construction, in particular, as well as operating software capabilities, can vary from one machine builder to the next.
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AdvancedManufacturing.org | February 2015
The ideal radius grinder should have a direct-drive, B-axis with hydraulic braking. It must also be well designed and construct- ed for high rigidity and stability, along with superior vibration- damping. While the B-axis concept has been in existence since the late 1990s, the direct-drive design is relatively new technology. Earlier machines used belts or gears to move/ steer the B-axis, but movement was choppy and inconsistent. Direct-drive technology eliminates these problems. In addition, a machine should incorporate highly devel- oped operating software to help further shorten machine setup times and ease programming.
Radius grinders with B-axis capability reduce wheel costs and shorten overall part-cycle times while generating high- precision, superior surface fi nishes.
Dedicated radius-grinding simulation functionality within a
machine’s software package is a must. Simulation is critical in internal radius grinding applications, as an operator can’t see the wheel working inside a part. Because the pendulum process involves multiple ma- chine axes moving simultaneously, radius grinding machine software must also help simplify part programming. Through highly advanced software packages, manufacturers can generate programs using dxf fi les imported from the 3D CAD software they used to design the part. Shops simply point and click on a part’s CAD fi le, and the machine software will generate the necessary grinding cycle from that information. Today’s research continues to advance B-axis radius grinding. For instance, grinding machine builder Studer has successfully ground full external spheres (complete ball shapes) onto test parts using a radius grinder with a B axis. Research technicians had the axis oscillate from a -60° posi- tion to a +60° one for 120° of axis rotation. Once perfected, such a capability will further expand the applications of radius grinding.
Product Engineer United Grinding
MODERN MANUFACTURING PROCESSES, SOLUTIONS & STRATEGIES
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