Looking at the future of manufacturing metrology: roadmap document of the German VDI/VDE Society for Measurement and Automatic Control

. “Faster, safer, more accurately and more ﬂexibly” is the title of the “manufacturing metrology roadmap” issued by the VDI / VDE Society for Measurement and Automatic Control (www.vdi.de / gma). The document presents a view of the development of metrology for industrial production over the next ten years and was drawn up by a German group of experts from research and industry. The following paper summarizes the content of the roadmap and explains the individual concepts of “Faster, safer, more accurately and more ﬂexibly” with the aid of examples.

by a considerable reduction in batch sizes, which can often only be managed by a more intensive use of metrology since lengthy production start-ups and pilot production runs can hardly be afforded any longer.At the same time more and more sectors of industry (such as aviation, medical products) are calling for a seamless documentation of the conformity assessment of all manufactured products, which is also impossible without a more intensive use of metrology.
The term "production metrology" is a natural one for metrology within the context of production, but this metrology is nevertheless also referred to as "manufacturing metrology" in German (Pfeifer and Schmitt, 2010;Dutschke and Keferstein, 2007).Figure 2 provides an overview of the more important fields of application for manufacturing metrology.These are also examined in the technical committees of the "manufacturing metrology" department of the VDI/VDE Society for Measurement and Automatic Control (GMA, 2012) where a working group has been formed which, in light of the aforementioned trends in manufacturing technology, has assigned itself the task of forecasting the future of manufacturing metrology (Fig. 3).
The results of this work have been published by the Verein Deutscher Ingenieure e.V. (VDI) under the title of "Manufacturing metrology 2020: a technology roadmap   for metrology in industrial production" (VDI/VDE, 2011).Summaries have been presented nationally (Imkamp andBerthold, 2009, 2011;Schmitt and Imkamp, 2011) and internationally (Schmitt et al., 2011;Grzesiak and Imkamp, 2012).This present paper points out the main results of the work.
The challenges and trends in manufacturing metrology can be described with the terms "faster", "safer", "more accurately" and "more flexibly".The topics of accuracy and speed are in particular of central importance, as can also be gathered from other studies of metrology, such as, for example, the market study on 3-D metrology prepared by the Fraunhofer Society (Fraunhofer-Allianz, 2010) and the technology roadmap for process sensors in the chemical and pharmaceutical industry (VDI/VDE/NAMUR, 2009).

Faster
On the one hand, speed means the development and application of metrological procedures by which information about product quality can be obtained in a shorter time.Here it is less a matter of developing procedures basically from scratch than of adapting a large number of known measurement principles for utilization in production.Optical methods play a significant part here (Leibinger and Tünnermann, 2012) (Fig. 4).On the other hand a tighter integration of metrology into production processes especially by means of automation will contribute to getting measurement results faster and using them more efficiently (Imkamp and Frankenfeld, 2009).In this way the times required for transportation to the measuring equipment can be reduced or even cut completely (Fig. 5).Furthermore, the information from measurements is directly available in production, thereby allowing the incorporation of control loops, for example.Regulation by means of an automated transmission of data can be implemented with a particularly high level of efficiency (Heizmann et al., 2009;Pfeifer and Imkamp, 2004).

More accurately
Demands relating to the accuracy of measurement technology are also increasing in conjunction with stricter quality requirements.This change affects procedures not only in  macrometrology (Schmitt et al., 2009) but also the microand nanometrology used for capturing the product shape (Bosse et al., 2009) (Fig. 6).
In macrometrology, as tolerances become tighter, e.g. for drives in wind power systems (DeGlee, 2010), a greater accuracy of the measuring instruments is required.In this context it is worth noting that, in response to the requirements of industrial quality inspection regarding, for example, traceability, techniques from geodesy are being used more and more frequently in manufacturing metrology (Hennes, 2007).Furthermore progress in optical technology and fast, lowcost computation leads to wide-spread application of laser trackers and digital photogrammetry for coordinate metrology (Estler et al., 2002).In micrometrology higher levels of accuracy are required on account of increasing miniaturization (Porath and Seitz, 2005;Wiedmann et al., 2011).Figure 7 shows the order of magnitude of these trends.
Demands for greater accuracy are also to be found in the measurement of material properties (Frenz and Schenuit, 2009) and electrical characteristics (Naß and Berthold, 2010).In addition to optimization of the procedures themselves, the monitoring and correction of environmental influences is becoming more important in this context.

Safer
Determination of measurement uncertainty and taking it into consideration in the conformity assessment are becoming increasingly important.Standardized procedures for determining measurement uncertainty will become more established and will be applied at different levels of detail depending on the task in question.More effort in determining uncertainty will need to be justified for the calibration of standards than in the inspection of straightforward product characteristics.As regards production, simplified procedures will be-  (Wiedmann et al., 2011), and macro-scale parts, e.g.measurement of large mechanical parts for wind energy systems (DeGlee, 2010).come established.It is precisely with safety-related products such as, for example, in the aviation industry and in medical technology that an evidential document regarding the determination of measurement uncertainty and its inclusion in the inspection decision will become standard and product safety will improve (Imkamp and Sommer, 2009).In addition, the computer-aided simulation of measurement processes on the basis of the Monte-Carlo method (JGCM 101, 2008) for determining measurement uncertainty will become more important.In the meantime implementations have become available for different measurement methods, in most cases in the form of prototypes (Schwenke, 1999;Bai et al., 2002;Hiller, 2011;Schmitt et al., 2008).In the field of coordinate metrology, systems are also already on the market (Fig. 8) (Wäldele and Schwenke, 2002) which are used in particular in the calibration of individual standards, and normative publications are now also available (ISO/TS 15530-4, 2008;VDI/VDE 2617-7, 2006).

More flexibly
The wide variety of measurement methods used in production is increasing and with it the flexibility of metrology.On the one hand, techniques are used which holistically register the shape of a product.These include fringe projection and photogrammetry (Bauer, 2003).With computer tomography it is even possible to register structures which are not accessible from the outside (Benninger et al., 2009;Kruth et al., 2011).Used, for example, to locate defects in castings or for running dimensional plausibility checks, computer tomography systems today attain measurement times which permit their integration into the clock-pulse-controlled production process -in other words, in-line utilization (Schnell, 2011) (Fig. 9).On the other hand, different methods are being increasingly combined into measuring systems that are called multi-sensor measuring systems (Weckenmann et al., 2009;Imkamp and Vizcaino-Hoppe, 2007) (Fig. 10).The combination of results from several sensors is called sensor fusion (Heizmann et al., 2009).This boosts the flexibility of the systems.It does however also increase the complexity of the measuring systems and also the demands imposed on the user as regards training and the effort required in preparation for measurements.

Summary
In addition to the technical aspects we have described, the 2020 manufacturing metrology roadmap (VDI/VDE, 2011) will include future developments in the fields of the economic assessment of metrology and of training not only in institutes of higher education but also in the commercial sector (Wäldele, 2011).This topic has a special importance since the qualifications of measuring instrument operators have in many cases a great deal of influence on the accuracy of results and on their usefulness in evaluating and improving production.Metrology will continue to grow in importance to industrial production.The increasing performance of metrology is reflected in its speed and levels of accuracy.At the same time it is becoming more flexible and can thus deliver more information about production.Mastering the uncertainty of metrology in production will contribute to making production more efficient and products safer.

Figure 2 .
Figure 2. Fields of application for manufacturing metrology (derived from Pfeifer and Schmitt, 2010).

15Figure 5 .
Figure 5. Faster metrology due to the automated integration of metrology into material flow with the aid of a robot..

Figure 5 .
Figure 5. Faster metrology due to the automated integration of metrology into material flow with the aid of a robot.

Figure 6 .Figure 6 .
Figure 6.Accuracy in coordinate metrology in micro-scale e.g.probe of a micro-scale part 3 measuring device (Wiedmann, Imkamp et al., 2011) and macro-scale parts e.g.measurement 4 of large mechanical parts for wind energy systems (DeGlee, 2010).5 6 Figure 6.Accuracy in coordinate metrology in micro-scale, e.g.probe of a micro-scale part measuring device(Wiedmann et al., 2011), and macro-scale parts, e.g.measurement of large mechanical parts for wind energy systems (DeGlee, 2010).

Figure 7 . 2 Figure 8 . 6 Figure 8 .
Figure7.Tendencies in the development of accuracy (here quantified by "uncertainty of measurement") in the case of instruments used in length measurement(Schmitt et al., 2009).