Staying in control

Image_1_SLD An example of a stability lobe diagram produced with Dormer’s proprietary software

Two research projects recently undertaken by Dormer’s Milling R&D facility inItaly aim to address one of the most significant factors affecting the machining process: vibration.

More commonly known as chatter, vibration affects a whole range of elements, from cycle time and productivity to the finished product and machine tool life.

“These kinds of projects usually fall within the realm of a research department at a university,” explains Francesco Minutillo, responsible for competence (research) projects at Dormer. “However, we feel it is important to be proactive in increasing our knowledge of vibration theory – not only to develop the next generation of cutting tools but also to help our customers solve vibration-related problems.”

The aim of the first project was to optimise the cutting process by developing an instrument to identify stability during milling. With stability comes higher performance, increased productivity, reduced production costs, improved component surface quality, less machine/spindle damage and longer tool life.

In practice, this meant developing software that could calculate the stability lobe diagram (SLD), a two-dimensional diagram that compares axial depth to cutting speed with a boundary line dividing the curve in regions of stability or instability (chatter). “When there is excessive vibration, most operators tend to reduce cutting speed, but with SLD they can do the opposite and increase the speed as they know where the boundary line for stability is,” says Minutillo.

This project gave birth to the second initiative which involved the development of a sound-spectrum analyser – an instrument capable of measuring and interpreting the noise generated from the milling process.This enabled detailed and accurate analysis of the milling process, providing crucial information about the presence of chatter and its frequency. This can, for example, help with finding a stable cutting speed.

Both projects have not only increased Dormer’s knowledge and understanding of a complex phenomenon that can have a significant impact on the productivity of cutting tools, but have also developed instruments than can help find stable cutting conditions and predict the final result of the milling process.

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