Woodworkers have traditionally pursued productivity improvement by increasing machine speeds and throughput. However, focusing on reduced scrap loss and improved yield has an equally dramatic effect on productivity. Short production runs, in particular, dictate attention to manufacturing every piece perfectly, with as little labor and machine cost as possible. Repair or remanufacturing of even one component erodes already slim margins.
Many machining defects result from typical cutting pressures formed at the edge of the cutting tool. These cutting forces often result in tearing or plucking of the wood grains, or tear-out of the unsupported edge of a workpiece as the tool exits the cut. In either case, the damaged piece must be repaired or scrapped, incurring additional time and cost.
Tool engineers have utilized a variety of designs to reduce cutting pressure and yield improved cut quality. Most of the previous designs have focused on achieving specific cutting angles for each wood species, which limits grain separation ahead of the cutting tool. Shear angles have also been incorporated to reduce the chisel-like cutting action of basic tools. Other options include adding more cutting edges to the tool, but this can result in heat build-up which damages the carbide tips. In 2009, an engineering team led by Andreas Kisselbach (Leitz GmbH), began testing the use of rippled knives to further reduce cutting pressure and preserve the wood grain. The theory that the sharp peaks of the rippled knives would slice through solid wood with ease was proven, and ripple technology was born.
Ripple technology utilizes micro serrations in the knife edge to greatly reduce the cutting forces at the largest diameter of the cutting tool, thereby allowing the tool to pre-cut the part without defect. The resulting tiny ridges left on the workpiece are effectively pre-scored and can be removed by the following knife or cutter under equally light cutting pressure.
Ripple technology can be achieved using a single tool or multiple tools. If two spindles are available to cut in the same plane, the first tool is equipped with ripple knives, and the second tool is equipped with finish knives. If only one spindle is present, the cutterhead is equipped with both ripple and finish knives. In both cases, the use of ripple and finish knives work in unison to divide and greatly reduce cutting pressures.
The greatly reduced cutting pressures also dramatically improve tool life, as lower pressure yields reduced knife wear. Operators report a 200-300% increase in tool service life from their finish knives, when used in conjunction with ripple knives. Machine owners will appreciate significantly improved machine throughput due to increased feed rates and reduced down-time due to tool changes.
The key benefit of ripple technology is reduced or eliminated repair work and scrap loss due to cutting pressure related defects. Ripple technology also increases the flexibility to cut multiple wood species with the same cutting angle, as the light cutting pressure reduces pre-splitting and residual defects.
Ripple serrations can generally be added to existing precision cutter systems at very low cost, since the only modification is in the profiling of the insert knives or diamond tips. Ripple technology can be utilized in many solid wood applications and the advantages can be enjoyed by small and large shops alike.
Source: Leitz Tooling Systems. Visit LeitzTooling.com or call (800) 253-6070.
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