Machine Technology

Getting a handle on heat in high-speed spindle bearings.

Measuring machine tool vibration with piezoelectric accelerometers.

A telescoping ball bar is a simple, but useful device that provides a quick and inexpensive way to characterize machine tool errors.

Real-time measurements during metalcutting can offer significant insight into machine tool performance. The parameters to be measured include position, velocity and acceleration of the axes; cutting force; sound; temperature; and acoustic emission, which is not the same as sound, but rather a high-frequency, structure-borne vibration.

Milling sounds range from loud to quiet, and experienced machinists often use those sounds to judge what is occurring in the cutting zone. It is difficult to position a sensor such as an accelerometer or a displacement probe close to the cutting zone, and it is often a challenge to see the cutting zone, but the sounds are pervasive.

The accurate positioning of the cutting tool with respect to the workpiece partly controls the accuracy of a machined part.

The moving elements of a machine tool have mass. Forces from the actuators cause the masses to move and accelerate. As the speed of the machine tool motion increases, the ability of the actuators to cause acceleration becomes more important.

In his October 2012 Machine Technology column, Dr. Scott Smith, professor at the William States Lee College of Engineering at the University of North Carolina at Charlotte, outlines the reasons stable milling zones appear the way they do.

The coefficient of linear thermal expansion helps shops anticipate thermal growth in parts, tools, and holders so they can protect tolerance, fit, and process stability.

Machine Technology column as published in the July 2012 issue of Cutting Tool Engineering.

Linear motion of machine tool axes is often achieved using screws and nuts.

Machine Technology columnist Dr. Scott Smith discusses the constraints related to the selection of machining parameters in the May 2012 issue of Cutting Tool Engineering.