Clément Fortin

Theory and simulation for the identification of the link geometric errors for a five-axis machine tool using a telescoping magnetic ball-bar

The position invariant geometric inaccuracies of a machine tool are the first to influence the quality of machined parts. A systematic approach is presented to identify some of these errors on a five-axis machine tool. The methodology is applied to the link error parameters such as joint misalignments, angular offset and rotary axis separation distance. A method based on the mathematical analysis of singularities of linear systems is used to assist in selecting a minimal but sufficient set of link error parameters for the calibration of a machine tool. A number of criteria are proposed in order to verify that the identified parameters accurately predict the positioning errors of the true machine. Finally, the numerical effectiveness of this method is shown through simulations.

Making sense of engineering design review activities

Abstract Engineering design reviews, which take place at predetermined phases of the product development process, are fundamental elements for the evaluation and control of engineering activities. These meetings are also acknowledged as unique opportunities for all the parties involved to share information about the product and related engineering processes. For product development teams, the knowledge generated during a design review is not as secondary as it may seem; key design decisions, design experiences, and associated rationale are frequently made explicit. Useful work has been carried out on the design review process itself, but little work has been undertaken about the detailed content of the meeting activity; it is argued that understanding the transactions that take place during a meeting is critical to building an effective knowledge-oriented recording strategy. To this effect, an extensive research program based on case studies in the aerospace engineering domain has been carried out. The work reported in this paper focuses on a set of tools and methods developed to characterize and analyze in depth the transactions observed during a number of case studies. The first methodology developed, the transcript coding scheme, uses an intelligent segmentation of meeting discourse transcriptions. The second approach, which bypasses the time consuming transcribing operation, is based on a meeting capture template developed to enable a meeting observer to record the transactions as the meeting takes place. A third method, the information mapping technique, has also been developed to interpret the case study data in terms of decisions, actions, rationale, and lessons learned, effectively generating qualitative measures of the information lost in the formal records of design reviews. Overall, the results generated by the set of tools presented in this paper have fostered a practical strategy for the knowledge intensive capture of the contents of design reviews. The concluding remarks also discuss possible enhancements to the meeting analysis tools presented in this paper and future work aimed at the development of a computer supported capture software for design reviews.

Cutting tool reliability analysis for variable feed milling of 17-4PH stainless steel

Variable feed machining has recently been proposed as a significant method to improve cutting tool life particularly for hard and diffucult to machine materials. This method, which is easy to apply in industry, has been shown to improve tool life in the order of 40% in certain cases. This paper presents a reliability model for the quantitative study of the effect of feed variation on tool wear and tool life. To better compare processes with two different wear modes, a reliability model taking simultaneously into account both flank and face wear has been developed. With this model, which is based on experiments, the tool life for the constant and variable feed cases was calculated from the reliability function. The mean time to failure, obtained from the reliability function, provides an accurate evaluation for any probabilistic distribution. The proposed method is therefore a general approach that can be used for analyzing cutting tool life under any conditions and for any equipment and material.

Tool path error prediction of a five-axis machine tool with geometric errors

Abstract Predicting the actual tool path of a machine tool prior to machining a part provides useful data in order to ensure or improve the dimensional accuracy of the part. The actual tool path can be estimated by accounting for the effect of the machine tool geometric error parameters. In computer aided design/computer aided manufacture (CAD/CAM) systems, the nominal tool path [or CL (cutter location) data] is directly generated from the curves and surfaces to be machined and the errors of the machine tool are not considered. In order to take these errors into consideration, they must first be identified and then used in the machine tool forward kinematic model. In this paper a method is presented to identify the geometric errors of machine tools and predict their effect on the tool-tip position. Both the link errors (position-independent geometric error parameters) and the motion errors (position-dependent geometric error parameters) are considered. The nominal and predicted tool paths are compared and an assessment is made of the resulting surfaces with respect to the desired part profile tolerance. A methodology is also suggested to integrate this tool within a CAD/CAPP (computer aided process planning)/CAM environment.

Manufacturing Process Management: iterative synchronisation of engineering data with manufacturing realities

The principles of Concurrent Engineering (CE) have led to an early introduction of manufacturing decisions in the Product Development Process (PDP). Nevertheless, the integration along the product life cycle of computer tools to help engineers manage their tasks in the global market still suffers from a poor understanding of information requirements for the effective streamline of the design to production process. Manufacturing Process Management (MPM) is a strategy that supports formal communication between engineering and production in a virtual 3D environment. This paper outlines how MPM enables a real-time assessment of component manufacturability and a parallelisation of product design and manufacturing processes. The proposed scheme is dedicated to offer CE teams the answers to integrated change management issues through a digital collaborative environment. From a technological perspective, a MPM solution provides an intelligent bridge between the Computer-Aided Design/Product Data Management (CAD/PDM) and Enterprise Resource Planning/Manufacturing Execution System (ERP/MES) software with viable perspectives for complete Product Life cycle Management (PLM) packages and new Knowledge Management (KM) approaches.

A balancing technique for optimal blank part machining

A balancing technique for casting or forging parts to be machined is presented in this paper. It allows an optimal part setup to make sure that no shortage of material (undercut) will occur during machining. Particularly in the heavy part industry, where the resulting casting size and shape may deviate from expectations, the balancing process discovers whether or not the design model is totally enclosed in the actual part to be machined. The balancing process requires a measurement dataset of the blank part to be balanced as well as a computer-assisted design (CAD) solid representation of the design model. A preferential constrained alignment algorithm calculates the proper compensation, or fixture offset, for any type of geometry to eliminate any possible shortage of material if possible, or orient the unavoidable area of missing material for appropriate rework. The alignment is an iterative process involving nonlinear constrained optimization, which forces datapoints to lie outside the nominal model under a specific order of priority. The Simplex method of direct search is used to solve the optimization process at each iteration. Two different artificial objective functions are implemented and compared for the balancing problem, a logarithmic and a least-squares formulation. The technique is applied to the balancing of a wiggle and a hydroelectric turbine blade. Results show that the balancing process under the logarithmic formulation converges faster than with the least-squares expression and is also more appropriate to balance the stock allowance for proper machining of the part.

Calibration of a Five-Axis Machine Tool for Position Independent Geometric Error Parameters Using a Telescoping Magnetic Ball Bar

Many parameters influence the quality of machined parts on five-axis machine tools. One important family of parameters are the geometric inaccuracies in the relative location of the machine axes. A method is proposed which uses a telescoping magnetic ball bar to identify these error sources. The methodology is applied to position independent geometric error parameters such as joint misalignments, angular offset and axes separation. Simulation results support the effectiveness of the approach.

Product decomposition using design structure matrix for intellectual property protection in supply chain outsourcing

In global recession, outsourcing becomes a question of survival for most executives who need to restore profitability and growth. One of the critical challenges faced by such decisions is the potential risk of leaking confidential information through shared suppliers and partners. In this paper, a new approach is proposed to decompose a product into several sub-components for mitigating the risk of Intellectual Property (IP) leakage caused by inferences in supply chains. A design structure matrix is employed to study the potential risk of IP leakage considering different types of interactions between product components. Based on such a matrix, a clustering algorithm is developed to decompose and allocate the product components regarding IP protection issue. This methodology can be considered as a decision support tool to help the manufacturer select a set of optimal suppliers while minimizing the information leakage risk and the manufacturing cost.

A Soft Gaging Approach for Complex Cases Including Datum Shift Analysis of Geometrical Tolerances

A soft-gaging approach using solid tolerance zones and three-dimensional alignment algorithms is proposed to verify various geometric and dimensional tolerances. The method is particularly well suited for the verification of position tolerances involving a possible datum shift which still requires traditional metrology techniques to be solved. The totally CAD based approach uses constrained and unconstrained alignment techniques in order to bring closer the measurement points relative to the toleranced features and the corresponding tolerance zones. The process can either deal, with structured sparse CMM data or unstructured dense data files generated by a manufactured part inspection process. A typical example is presented to illustrate the developed methodology applied to a datum shift problem, which is solved using a non-linear constrained optimization method.

Calculation of virtual and resultant parts for variational assembly analysis

Usually, the design of mechanisms and assemblies uses the perfect model of the part. This type of model can be used within a software application to simulate and to verify the kinematics and dynamic behavior of such mechanisms. However, the analysis of the manufacturing uncertainties is also necessary to control the sensitivity and robustness of the mechanism assembly. To take into account these uncertainties, the designer deals with a class of interchangeable and functionally equivalent parts. When specifying tolerances, he essentially defines the authorized variations of the envelope of the parts and a number of classes can represent the various domains of acceptance of the parts. Since we need to take into account the infinite number of parts allowed by the variational class, the analysis of variational assembly is a hard task. In this paper, an extension of our previous work to calculate the virtual and resultant parts is proposed. The proposed method takes into account the datum chaining in the toleranced part. A kinematics model and robotic parameterisation is used to simulate the possible “motion” of the tolerance zone, allowed by MMC and LMC modifiers. Thus, the analysis of the infinite number of parts is reduced to analyse only two parts for each variational class. The analysis of the Jacobian matrix of the mechanism effectively generates the intersection and the union of all the boundaries of the features of the part. The paper presents also a significant application of this approach.