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Controlled by factory noise

Company develops sensors to control industrial machines

Anyone who ever enters the machining shop area of an industry comes upon several different types of machine in noisy operations. Some are called robots and all have gotten a new type of controlling mechanism, using sensors, which detect defects based on the sound the equipment makes. This advanced control system is the theme as the work done by Sensis, a São Carlos-based company in the State of São Paulo, which is concluding the second phase of the project ‘Research and Development of Micro-controlled Systems for the Monitoring of the Machining of Precision Components Using Acoustic Emission”. This project is part of the Technological Innovation in Small Companies Program (PIPE) sponsored by FAPESP. Using the support of the Program, Sensis has concluded the research for developing a new model of sensor.

The new system represents an advance in relation to existing products on the market which measure noise for the monitoring of production processes. Using sensors, this equipment monitors the whole range of machining activities such as milling, drilling, rectification and lathing. Sensis itself manufactures a model of sensor, the BM12, capable of furnishing reliable data. More than 60 units of this machine have been sold to auto-parts factories in Brazil.

The problem with the BM12 is its analogue limitation, or in other words, it works without any digital content and is therefore unable to communicate with the new and/or improved generation of machines using information technology. “Our challenge was to discover what had to be done to the BM12 in order to incorporate the digital functions which would result in more reliable and better quality machining”, explains the coordinator of the project and partner in Sensis, Luiz André Melara de Campos Bicudo.

In the search to perfect the equipment, Sensis’s five partners hunted the world looking for software that would provide the basis for an efficient and reliable monitoring system. “We had to do it all ourselves. We found nothing that interested us”, says Bicudo. Thus, in tandem with upgrading the models of sensors, a tailor-made software was also developed.

After receiving all the innovations and renamed as DM42, the model has been exhaustively tested over the last few months. About 30 prototypes of the new generation have been installed in machines on the factory floor of various companies such as Norton, in the United States and Zema Szelics in Brazil. Norton is the world leader in abrasive products for cutting metals for the manufacture of machine tools and is part of the Saint-Gobain Group.  Zema manufactures in Brazil machinery that uses these components.

“I use the Sensis product successfully. I am even gathering data to demonstrate its importance in our business”, says Chris Arcona, a researcher at Saint-Gobain Abrasives, and responsible for managing the process of adapting the DM42 to Norton’s machines.

Ceramic rings
The key to success of the equipment is the sensors. They are assembled in six different ways, all of them with their small and strange piezoelectric ceramic rings, the raw material chosen due to its highly developed capacity to act as a sound receiver. The models were designed in according to the operations to be executed (milling, lathing, etc.).

One of the versions is anchored by magnates at the base of the machines, so that the installation and functioning does not require screw fixtures. A second model (a fluid sensor) required even more adjustments since it captures the sound of the interaction of the machine tools with the parts being form the oil lubrication process of the machine itself. The response time for this system is about 7 to 8 milliseconds.

Another version of the DM42 has timing and logic functions, devices which control the interaction cycles of the parts with the machines and moreover they interpret the signals that are recorded. Overall, the machine can identify over 20 parameters such as the level of sound that is received from the sensor, which can then be amplified, and a subsequent comparison made via computer program.

To monitor a forged part being machined is only one of DM42’s missions. “It is perfectly possible to analyze the degree of wear and tear of the grinding component and in this way ensure higher quality from the final processing.” explains Juarez Felipe Júnior, one of Sensis’s partners. If parameters for sound are duly fed into the sensor’s memory, then the DM42 is able to detect the real state of the grinding component and the characteristics of its surface.

By doing this, problems are avoided. Based on computer screen images, the machine tool operator can activate a corrective process in the grinding piece, known as dressage, which consists of rehabilitating the millimeter grains on the surface of the grinding instrument by using a sharpened diamond headed cutter.

No collisions
DM42 makes the whole machining process faster and safer by eliminating slow stages in the manufacturing process such as the gradual moving together of the grinding pieces and detecting collisions due to parts accidentally fed into the production system. Through the simple contact of the machine tool with an extraneous object in its operating field, the device automatically aborts the working of the grinding system. “For a factory that gets a minute per a part is manufactured, the savings at the of month can be an astonishing”, Bicudo recalls.

Sensis started up at the Nucleus for Advanced Manufacture (Numa) of the School of Mechanical Engineering of the University of São Paulo (USP), São Carlos campus. There, the present coordinator, João Gomes de Oliveira began a line of research in 1993, after returning from the United States where he had obtained a post doctorate qualification. At the laboratories of the Mechanical Manufacturing Area of the University of California, Gomes worked as assistant to research scientist David Dornfeld, a visionary who, at the beginning of the nineties, conducted an academic study on the processes of acoustic emissions.

The beginning
In 1995, Sensis was founded by students of Gomes, as a company born out of the ParqTec Foundation. The first of the five partners that began to think of setting up a company was Luiz André Bicudo. In 1993, he began studies that resulted in the building of the first didactic lathe called the Didat. Sensis eventually marketed this equipment, mainly to technical schools.

Currently, Sensis is focusing strongly on the implements market by selling the DM42 to manufacturers of industrial machines. In the same fashion as the auto assembly lines, the DM42 is expected to mount its device in the control panel of grinding and cutting machinery, lathes, drilling machines etc.

With the innovation brought to the market by the DM42, the machining area of any factory will continue noisy and even forbidding but, on the other hand, it will become more sophisticated, precise and economical.

Luiz André Melara de Campos Bicudo, graduated in Computer Science at the Federal University of São Carlos (UFSCar). Took a master’s degree and doctorate from the Engineering Faculty of São Carlos, University of São Paulo (USP).

The project
Research and Development of Micro-controlled Systems for the Monitoring of the Machinery of Precision Components Using Acoustic Emission (nº 97/07245-4); Modality Innovative Research in Small Business (PIPE); Coordinator Luiz André Melara de Campos Bicudo; Investment: R$ 135,505.00 and US$ 29.229.00