A new interactive approach in teaching complex

multi-sensor measuring technology

J Bargenda, E Reetz, M Schumann, M Vogel and G Linÿ

Ilmenau University of Technology, Faculty of Mechanical Engineering, Department of QualityAssurance, Ilmenau, Germany

E-mail: joerg.bargenda@tu-ilmenau.de

Abstract. This document states bene�ts, possibilities and importance given by a newinteractive approach in teaching complex contents of integrated multi-sensor measuringtechnology, regarding optical and tactual coordinate measuring technology at the IlmenauUniversity of Technology.

1. Introduction

In terms of handling problems regarding measurement processes, image processing becomes moreand more important. Many students face problems abstracting measurement problems and theirsolutions caused by lack of practical experience in handling complicated measuring technology.On the other hand understanding dimensions and scales, tolerance zones, measurement errors andmeasurement deviation, speci�cally regarding small components, is missing. Modern measuringdevices come at a high level of complexity, hence the handling of these devices in most ofthe trainings and teaching concepts covers only a very limited extent of functionality. Thepotential bene�t of each di�erent method and strategy in measuring mechanic or electroniccomponents is seldomly demonstrated. Especially opportunities and advantages given bycombining di�erent methods of measuring devices is not included in the regular curricular.The interactive application of multi-sensor measurement devices opens new perspectives for anintegrated approach of solving measurement problems.

For students the complexity of handling the measurement device itself is another obstacle. Theinteractive part of the training will be conducted on the SPECTRUM 700 coordinate measuringmachine (see �gure 1a), which commands a tactile and an optical sensor. This enables teachingof the di�erent measurement methods at constant conditions.

2. The Teaching Concept

A given mechanical component (production part, see �gure 1b) is used to de�ne several tasksto be measured and speci�ed in several assignments. For tactile measurement tasks di�erentsensors will be used to measure geometrical dimensions and positions. For optical measurmenttasks the Viscan sensor will be used, which is also available for the Zeiss coordinate measuringmachine SPECTRUM 700 (see �gure 1a). The measurement results of both, the tactile

(a) Zeiss SPECTRUM 700 (b) Bent sheet metal part � design drawing

Figure 1: Coordinate measuring machine and production part to be measured

and the optical measurement method, could be compared, due to the fact that environmentvariables, e.g. the lighting, could change. Di�erences in the results based on the measurementmethods context could explain advantages and disadvantages of di�erent measurement strategiesand method's. The new multistage approach guides students step by step through problemsconcerning measurment technology. The interactive teaching concept is based on a three stagemodel, using the following methodology.

A single practical experience as completion of the theoretical knowledge basis is considerednot to be very useful in topics of such complexity as metrology. The learning curve will greatbe improved by a tutoring concept with special attention to identifying and resolving possiblemistakes immediately. At the same time the students methodological approach is guided. Inorder to enable the students to handle the complexity of the matter, the following three stageswere developed (see �gure 2).

Stage One

The target of the �rst stage is to explain the general handling of the measuring device. Thisrequires interdisciplinary theoretical knowledge acquired in the academic career. The structureand the di�erent types of coordinate measuring machines, di�erent types of scanning probes andsensors, measuring points and the number of measuring points to acquire per element as well asimportant criteria for evaluating the measurement results are explained using a bent sheet metalpart as practical example.

In the next step an inspection plan has to be created by the students, using the operatingsoftware (see �gure 3). The students familiarize with the speci�c control options of the

Figure 2: Three stage teaching concept

device (control panel, positioning methods, probe change). For capturing the elements of themeasurement subject the students can choose between the teach-in mode and the selection ofsingle elements within the CAD model.

The inspection plan in stage one contains measuring the distances between the bentlongitudinal edges of the production part (see �gure 4a). To do this the measurement subject hasto be mounted, then the system has to be informed about the current position of the subject. Forthis purpose the outer contour will be de�ned using on the outer surfaces of the measurementsubject. Furthermore basic needs like the de�nition and orientation of the basic coordinatesystem as well as the selection and usage of a suitable scanning probe will be explained. Next

Figure 3: Preparing the inspection plan

the necessary features that are to be measured have to be added to the inspection plan. Specialattention has to be given to the measuring strategies and the basic conditions � they are criticalfor the measurement results. The practical aspects will be strengthened not only by the operatingsoftware itself, but also by the fact that further pc workstations with the same operating softwarefor simulation purposes are available.

After successful creation of the inspection plan students ca proceed to the coordinatemeasuring machine. Possible errors with the positioning path, the selection process of the rightscanning probe, an appropriate positioning speed as well as a su�cient number of measurementpoints become apparent immediately, which encourages the process of understanding. The �rststage is completed with a successfully processed inspection plan including the evaluation of themeasurement results afterwards.

(a) bent longitudinal edges (b) parallelism

Figure 4: Inspection plan for the production part (excerpt)

Stage Two

Stage two contains the determination of form, positional tolerances and relations. Furtherinstructions are necessary to understand roundness, �atness, parallelism, cylindricity, symmetryand perpendicularity (see �gure 4b). In contrast to the theoretical instructions the practicalexperience with dimensional and geometrical tolerances motivates the students. Furthermorethey realize the in�uence of changes in temperature between two comparative measurements.

Stage Three

Stage three of the teaching concept deals with the complex interactions of di�erent sensors fora more complex inspection plan. To measure the boreholes in the production part the scannerprobe has to be changed. The students are facing the decision for the right scanning probe again.Scanning probes available are tactile sensors with di�erent sizes and parameters as well as theoptical probe system ViScan (see �gure 5a). At this stage particular attention will be devotedto the optical probe system. In its adjustments the optical system is more di�cult to handlethan the tactile one due to additional parameters like lighting, the correctly con�gured focus orsetting criteria for edge detection. The relationship between calibration and adjustment of the

sensors are illustrated. First of all the tactile and the optical sensor are re-measured, then aninspection plan for multisensor technology will be created. This illustrates speci�c advantagesand disadvantages of probe systems (see �gure 5b).

The importance of the right setting of criteria like the direction for edge detection and correctfocus settings will lead to their in�uences on the measurement results. Realizing the parameter'sin�uence on the measurement result is the key element at this stage. The third stage is completedwith the successfully processed inspection plan using multisensor technology. An additionaltask for the students is to �nd a time e�cient measurement strategy. For this purpose themeasurement points have to be brought in an order that minimizes the distance of the sensorduring the measurement. Also the time of the sensor changes have have to be chosen timee�ciently.

(a) Optical probe sys-tem ViScan

(b) Application with multisensor technology (inspec-tion plan)

Figure 5: Multisensor technology and application

First experiences

Results from the concepts �rst validation phase have shown, that the complexity is to high tobe handled by students. Speci�cally the usage of the operating software causes many di�cultiesand mistakes. In fact, the students motivation decreased by di�culties with handling the userinterface of the software. The tutoring concept of direct support usually helped a lot to �xthe problems immediately. These results lead to a reduction in the requirements and severaladjustments in the concept.

3. The Students Opinion

Asking the students opinion about the new training, most of them agree that it is an interestingand exciting series of experiments, explaining the connection between theory and practical

application. The information was gained with a questionnaire which the students had to�ll in directly after the completion of the current stage. The opportunity to gain someexperiences working with multi-sensor measuring devices and discovering di�erent in�uences onthe measurement results was highly appreciated by the students. The prospective engineer'smotivation for training the acquired knowledge with practical demonstrations increasedsigni�cantly. The goal of the teaching concept - solving a measurment task for a productionpart by creating an inspection plan and successfully processing it on a coordinate measuringdevice - could be achieved. Unfortunately is has to be pointed out that the number of studentsparticipated in the trainings yet is too small to be convincing.

4. Summary and Prospect

The training in optical and tactile measurement technology enables students to gain experiencein the usage of measuring devices and encourages the process of understanding measurementmachines and their characteristics. The academic education will bene�t from the increasingquality by combining theoretical lessons with interactive trainings. The Ilmenau University ofTechnology is o�ering such a combined teaching method with its new consecutive degree program`Optronik', which is a cross-section-science, based on the technical disciplines optics, electronics,mechanical engineering and computer science.

References[1] Linÿ G 2003 Training Qualitätsmanagement (München, Wien: Fachbuchverl. Leipzig im Carl-Hanser-Verl.)[2] Linÿ G 2006 Statistiktraining im Qualitätsmanagement (München, Wien: Fachbuchverl. Leipzig im Carl-

Hanser-Verl.)[3] Linÿ G 2005 Qualitätsmanagement für Ingenieure 2nd ed (München, Wien: Fachbuchverl. Leipzig im Carl-

Hanser-Verl.)[4] Carl Zeiss (ed) 2009 Calypso Basisschulung (Aalen: Carl Zeiss 3D Metrology GmbH)[5] Beets S, Roitmeier R and Weckenmann A (eds) 2002 Ausbildungskonzept Koordinatenmesstechnik - AUKOM

vol 81-01 (FQS-DGQ)