Every shop deals with two universal truths: People are part of the process and make mistakes, and sooner or later, all mechanical devices will either wear out or break. The consequences of both truths can range from merely expensive to catastrophic. A modest investment in machine and process monitoring technology can, and nearly always does, pay large dividends over the long run in sparing moldmakers from the consequences of human error and the breakdown of machines.
Modern sensor technology comes in one of two forms: micro electro-mechanical systems (MEMS) and piezoelectric devices. Each has a distinct set of capabilities and advantages for machine monitoring applications.
MEMS sensors are miniature machines with integrated electronics that are produced by technologies similar to those used in the manufacturing of semiconductor devices. Because MEMS sensors are highly reliable and are relatively inexpensive, they are widely used in all sorts of electronic devices where their small size, low consumption of power, ease of integration, high level of functionality and superb performance encourage and enable innovation.
The major advantage of a MEMS sensor in a machine-monitoring application is its ability to detect vibration at extremely low amplitudes. For example, a MEMS sensor can detect vibration in a spindle rotating at speeds as low as 2 rpm. Because the signal processing electronics are integrated into a MEMS sensor, MEMS sensors also tend to be less expensive than comparable piezoelectric units.
Piezoelectric sensors use the current that is generated by deforming a crystal to measure the amplitude of a vibration. Piezoelectric sensors are not able to detect low amplitude vibrations nearly as well as MEMS devices. They deliver a non-linear response in that region. However, piezoelectric sensors are extremely rugged and are able to survive crashes generating up to -70 Gs, while most MEMS sensors experience damage at about -18 Gs.
A further advantage of piezoelectric sensors is their ability to respond to vibration and acceleration in three axes instead of one or two for MEMS devices. The combination of ruggedness, 3D sensing, and the ability to serve as both a vibration and crash detection device make piezoelectric sensors the technology of choice for most large machine tools.
Modern machine and process monitoring technology is as easy to implement as a retrofit solution. For example, installing a true power monitor on a vertical machining center typically takes no more than two to three hours, plus the time needed to program the PLC. A complete crash protection, vibration sensing and tool condition monitoring system might take eight hours to install on the same machine. Since most of the added components are in the electrical cabinet, the actual installation of the control system is quite simple. The digital torque adapter installation is even simpler.
As long as people make mistakes and machines wear out, some form of crash protection and condition monitoring technology will be the first line of defense against expensive and potentially catastrophic consequences. Fortunately, the technology is mature, effective, affordable and easy to implement, so there is no point in waiting to put it to work.