J. Barreiro

Information model for the integration of inspection activity in a concurrent engineering framework

Abstract The basis of the integration of activities related to the product life cycle is, mainly, the creation of a unique and coherent information model along all the stages in the cycle. Up to date, dimensional inspection activities have not been deeply analysed, possibly due to the fact that, their work influences are smaller than others, such us numerical analysis, materials or numerical control. However, the integration of dimensional inspection is very important for several reasons: the need of specifying the design and planning of the inspection process from the conceptual part design; the increase of use of high speed coordinate measuring machine (CMM) in the production lines; and finally, for the interest of a feedback between data inspection and manufacturing processes. This paper is a detailed proposal of an information model for inspection based on operations for CMM, which represents a consistent structure of the necessary data in an integrated product setting.

Application of a Force Sensor to Improve the Reliability of Measurement with Articulated Arm Coordinate Measuring Machines

A study of the operator contact force influence on the performance of Articulated Arm Coordinate Measuring Machines (AACMMs) is presented in this paper. After developing a sensor capable of measuring the contact force applied by an operator, a ring gauge has been used to analyse the relationship between the contact force and diameter and form errors measured with the AACMM. As a result, contact force has been proved as one of the main factors influencing the AACMM performance. A probe deflection model based on the Finite Element Method (FEM) has been also proposed in order to obtain the AACMM probe deflection caused by contact force. This allows measurement correction by comparing them with reference values, specifically, a ring gauge. Experimental test results show a significant measurement improvement that minimizes diameter error. Finally, an uncertainty evaluation for the contact force sensor and AACMM measurements with and without probe deflection model has been carried out in order to validate the ability of the sensor and the methodology followed.

Design of a Computer Vision System to Estimate Tool Wearing

Wear level of tool inserts in automated processes is tried using techniques of artificial vision. An application has been developed in Matlab that allows the acquisition of images with different resolutions and later on to process them. It is explained how the vision system used has been designed and implemented. The method for acquiring tool insert images and their treatment in the pre-processing, segmentation and post-processing is commented. First results are also presented using diverse texture descriptors. These first results must be corroborated carrying out new experiments with a bigger number of images.

A new concept of feature-based gauge for coordinate measuring arm evaluation

Articulated arm coordinate measuring machines (AACMM or CMA) have conquered a market share in the actual dimensional metrology field, overall when their role implies the inspection of geometrical and dimensional tolerances in an accurate 3D environment for medium-size parts. However, the unavoidable fact of AACMM manual operation constrains its reliability to a great extent, avoiding rigorous evaluation and casting doubt upon the usefulness of external calibration. In this research, a dimensional gauge especially aimed at AACMM evaluation has been developed. Furthermore, the operator skill will be revealed through the use of this gauge. A set of geometrical features, some of them oriented to evaluate the operator and others the equipment, have been collected for the gauge. The proposed evaluation methodology clearly distinguishes between dimensional and geometrical tolerances (with or without datum references), whereas actual verification standards only consider the former. Next, quality indicators deduced from the measurement results are proposed in order to compare AACMM versus coordinate measuring machine (CMM) performance, assuming that CMM possess the maximum accuracy that AACMM could reach, because CMM combines maximum contact accuracy with minimum operator influence. As a result, AACMM evaluation time could be significantly reduced since this gauge allows us to perform a customized evaluation of only those specific tolerances of interest to the user.

Functional model for the development of an inspection integration framework

Abstract Product dimensional inspection is set as one of the essential parts of the production process, where not only product quality test is checked but also its interaction with other development stages in a minimal time. This enables a feedback to make quicker production and design decisions, provides updated information about the inspection processes to be shared and used in the new development processes, and permits the simultaneous work in the preparation of the inspection processes themselves. For this aim, it is necessary, as it occurs in the STEP framework, to develop an application context that includes all dimensional inspection aspects, from the geometrical and measurement aspects to those related to administration and configuration product data. This paper proposes a solution to integrate the dimensional inspection process with coordinate measuring machines with the design and manufacturing processes. Integration is achieved through a common product information model. A functional information model, a reference information model and an interpreted information model have been defined. The interaction with other information models associated to other activities of the production cycle is possible. Tests have been made of the possibility of making the inspection information interchange at the operation level instead of making it at the CMM trajectory level, as it is the case of the current DMIS format. This level of information definition is easier to put into effect, easier to interpret, and it is more productive. In order to test the validity of the information model, a real work environment which has been called IFCIA (Inspection Framework for Concurrent Information Access) has been developed. The IFCIA architecture is composed of a product modelling system, an object-oriented central database and a tri-dimensional coordinate measuring machine. The model has been implemented on an object-oriented product central database which is accessible by all the applications, so that the access to data is achieved in a concurrent way and in real time for the different agents involved in the development cycle, in a heterogeneous framework of platforms and applications. The generation and transference of the information among these systems are carried out exclusively according to data structures defined in the information model.

Computer Vision and Classification Techniques on the Surface Finish Control in Machining Processes

This work presents a method to perform a surface finish control using a computer vision system. Test parts used were made of AISI 303 stainless steel and were machined with a MUPEM CNC multi-turret parallel lathe. Using a Pulnix PE2015 B/W camera, a diffuse illumination and a industrial zoom, 140 images were acquired. We have applied a vertical Prewitt filter to all the images obtaining two sets, the original one and the filtered. We have described the images using three different methods. The first features vector was composed by the mean, standard deviation, skewness and kurtosis of the image histogram. The second features vector was made up by four Haralick descriptors --- contrast, correlation, energy and homogeneity. The last one was composed by 9 Laws descriptors. Using k-nn we have obtained a hit rate around 90 % with filtered images and, the best one, using Laws features vector of 92.14% with unfiltered images. These results show that it is feasible to use texture descriptors to evaluate the rugosity of metallic parts in the context of product quality inspection.

Testing coordinate measuring arms with a geometric feature-based gauge: in situ field trials

This work describes in detail the definition of a procedure for calibrating and evaluating coordinate measuring arms (AACMMs or CMAs). CMAs are portable coordinate measuring machines that have been widely accepted in industry despite their sensitivity to the skill and experience of the operator in charge of the inspection task. The procedure proposed here is based on the use of a dimensional gauge that incorporates multiple geometric features, specifically designed for evaluating the measuring technique when CMAs are used, at company facilities (workshops or laboratories) and by the usual operators who handle these devices in their daily work. After establishing the procedure and manufacturing the feature-based gauge, the research project was complemented with diverse in situ field tests performed with the collaboration of companies that use these devices in their inspection tasks. Some of the results are presented here, not only comparing different operators but also comparing different companies. The knowledge extracted from these experiments has allowed the procedure to be validated, the defects of the methodologies currently used for in situ inspections to be detected, and substantial improvements for increasing the reliability of these portable instruments to be proposed.

Implementation of decision rules for CMM sampling in a KBE system

This work presents a methodology for setting the number and spatial distribution of inspection points in the automatic inspection of parts using Coordinate Measuring Machines. This methodology collects the existing knowledge about sampling rules in automatic inspection. The final purpose is to store this knowledge in a KBE platform oriented to the inspection planning process and based on the MOKA methodology.

Tools for Teaching-Learning of Manufacturing Engineering Using Content Management Platforms

This paper presents the methodology that is being applied at present time for teaching and evaluation of different courses in the area of manufacturing processes engineering at the University of León. The context is delimited to the use of content management systems and continuous evaluation of learning. In particular, the Moodle platform is used for structuring the contents and for the continuous evaluation of courses in the scope of materials science, manufacturing processes and automation of operations. An analysis of the changes and challenges derived from the adoption of this methodology in the different courses in which has been applied is presented. These changes have been slightly different as a function of the compulsory or optional character of courses, as well as depending on the number of students enrolled in them.

Conceptual principles and ontology for a KBE implementation in inspection planning

The inspection process planning with coordinate measuring machines involves repetitive and well-known decisions to make about the different strategies to use, although much of this knowledge is today implicit in the expert mind. Therefore, the inspection planning is a good activity for implementing knowledge-based engineering (KBE) systems. However, the origin of KBE is in the design activity and, traditionally, the different methodologies have been applied to that activity. In this paper, the focus is the application of a known methodology traditionally used in the design process to the inspection process with coordinate measuring machines. The paper considers the knowledge elicitation phase, that is, the knowledge identification before its formalisation and implementation in a platform. The identification of knowledge is done in a high-abstraction level using a combination of IDEF0 diagrams and a text analysis application. The knowledge extracted was represented in a first approximation by means of a modified ontology to adapt the original MOKA ontology to the inspection process.