Metrotronics: mechatronics + metrology

Metrology leaves the laboratory and enters the factory: quality control and measurements directly on the production line.

In the manufacturing sector, above all, there has been a considerable increase in the request for measurements performed directly on the production line. In this article we will talk about the solution found by ECAwhich takes the name "Metrotronics": starting from the definition and the needs we will come to know all the advantages of its application.

For many industrial sectors there is an increasing need to ensure that all products comply with the specifications, thus making the statistical sample control carried out in the Laboratory insufficient.

On average, it is required to be able to measure pieces automaticallywith an hourly frequency exceeding thousands of pieces; the measurement may also be associated with a quality control, either "cosmetic" or functional. On the other hand, the accuracy of the measurement required in-line is always closer to that of the Laboratory equipmentThis calls for an increasingly rigorous metrological approach.

L’practical application of metrology has always had its natural home in the lab, in a controlled environment. The instrumentation and technologies designed to perform measurements have also adapted to this environment. Now the need to leave the Laboratory involves a series of not indifferent activities, to be evaluated as a new opportunity for the current metrology sector.

Definition of "Metrotronics

Hence the need to identify with a term a series of actions, thoughts, rules and technologies, so that they can assume a defined scope and form. I took the liberty of creating the neologism "Metrotronics"to identify everything within the scope of theadaptation of metrological instruments so that they can operate directly and effectively in an industrial production environment. Metrotronica is a word composed of metro(logia) and (mecca)tronica.

Metrology is the science that has as its object the study of issues related to the measurement of physical quantities (ref. Treccani Encyclopedia online) and, according to the VIM definition, Article 2.2, is the science of measurement and its applications.

Mechatronics is a word composed of mecca(nica) and (elet)tronica and means "science that comes fromintegration between mechanics and electronics in order to design, develop and control systems and processes with a high level of automation and integration” (ref. Treccani Encyclopedia online). Many companies producing measurement equipment are investing a large part of their R&D resources in this area.

5 key aspects of automatic measurement in an uncontrolled environment.

1. Metrotronics and the object

In the first place the impossibility to control everything that was controlled in a laboratory environment and could affect the measured objectSpecifically, the influence of uncontrolled quantities will be more or less critical depending on the type of measurement to be performed. If I have to measure a metallic object, I will concentrate more on aspects relating to temperature and not, for example, those relating to the percentage of humidity in the air.

2. Metrotronics and the instrument

In second place we consider the inability to control everything that was controlled in a laboratory environment and could affect the measuring instrumentIn this case, a lot depends on the tool we plan to use. Often dynamic stresses such as environmental vibrations and lighting variations (for optical measuring systems) are two characteristics to be analyzed.

3. Metrotronics and the environment

In third place we consider the difficulty or inability to prepare the object to be measured in an optimal and controlled manner with which you prepare it in the lab. The fast and repetitive aspect of the measurement implies its automatism. In the Laboratories there are specialized operators who prepare the object for measurement, a fundamental and complex operation which, if performed by an automatic mechanism in an unsuitable way, can lead to incorrect measurements. The most trivial of the problems to deal with is the lack or incomplete cleaning of the piece.

4. Metrotronics and speed

In fourth place the measurement speed. Measuring a part in a few seconds and performing hundreds of dimensions per second is often the norm for these machines. A large number of measuring instruments are not able to perform the measurement with sufficient speed. There are two reasons for this technological problem related to the instrument or a measurement method problem. For example, various methods can be used to measure the hardness of a material (Brinell, Vickers, Rockwell), based on the measurement of the resistance that one body makes to penetrate another body. An important parameter in these measurements is the time it takes for the penetrator to act on the object.

In order to have an ISO-compliant scale, this time is in the order of a few seconds, too high (even orders of magnitude) for online measurements. This is a classic example of a measurement standard designed for a laboratory measurement.

5. Metrotronics, repeatability and accuracy

As a fifth and final aspect we consider the need to measure repeatability and accuracy in real time if possible. In an industrial environment the loss of accuracy of the instruments is on average higher than in the Laboratory, so it is essential to know the actual repeatability and accuracy of the instrument. A case history illustrating a possible solution will be presented below.

VEA technologies, application of metrotronics.

Already from these key aspects of automatic measurement you can clearly focus one of the peculiarities of the MetrotronicsIt is a science that brings with it the considered evaluation of several metrological aspects and combined uncertainties generated by measuring different physical quantities.

quality control plant and micrometric measurement of pistons

I report the experience of a micrometric measuring systemrecently made by VEA, which performs measures in production line of cylindrical objects approximately 40 mm in diameter, measuring one part every 3 seconds and the required measurement accuracy is 4 µm.

The pieces come out of a washing machine and are dried by jets of hot air; each piston comes out with a different temperature, with excursions of up to 40 °C, which implies about 38 µm of thermal expansion.

Thermal appearance

They were made ad hoc high speed thermal sensorsbecause the ones on the market were not fast enough, and an algorithm of quadruple-stage temperature compensation with auto-calibrationwhich takes into account the ambient temperature, the temperature of the workpiece, the gauge and the optical sensor that makes the measurement.

Loss of accuracy

In order to detect the loss of accuracy of the instruments, a self-calibrating system has been adopted, which contains internally reference gauges, with a automatic procedure to check for variations. Vibrations in the environment can sometimes cause incorrect measurements.

The use of a particular proprietary technology, called MSA (Micro Stabilized Accuracy), allows you to detect in real time the standard deviation of a given measure. From it the repeatability of the instrument can be deduced and, in case of a large deviation, it can be decided to repeat the measurement, also because vibrations are often momentary phenomena. In the plants under construction there is a tendency to improve the accuracy of the systems by increasing the interactions between different physical quantitiesfor example with the introduction of accelerometers or devices that allow the reflection index of the objects to be measured to be analysed.

Metrotronics and metrology

I conclude this "introduction" to metrotronics with some ideas that would deserve further study.

The amount of information generated by online measuring systems allows you to improve the production process automaticallythrough an appropriate feedback process. In addition, these technologies are fully covered by the new funding under the National Strategic Plan. INDUSTRY 4.0which could be a good opportunity for many companies.

The measuring systems present in the production lines are still mainly manual solutions or, if automated, that do not take into account the environmental factors and aspects discussed above, showing great room for improvement. To paraphrase a famous saying, I could say that "behind a great metrologer is always a great metrologer", because the two figures are strongly complementary: the metrologist possesses the knowledge for identify uncertainties; the metrotronic has the one to find the solutions to identified uncertainties.