An Integrated Process Planning System Architecture for Machining and On-Machine Inspection

Inspection is an essential part of the entire manufacturing chain providing measurement feedback to the process planning system. Fully automated machining requires automatic inspection process planning and real-time inspection results feedback. As inspection process planning is still based on G&M codes containing low-level information or vendor-specific bespoke routines, inspection process planning is mostly isolated from machining process planning. With the development of new data model standards STEP and STEP-NC providing high-level product information for the entire manufacturing chain, it is achievable to combine machining and inspection process planning to generate optimal machining and inspection sequences with real-time measurement results feedback. This paper introduces an integrated process planning system architecture for combined machining and inspection. In order to provide real-time inspection feedback, On-Machine Inspection (OMI) is chosen to carry out inspection operations. Implementation of the proposed architecture has been partially carried out with a newly developed data model and interpreter software. A case study was carried out to test the feasibility of the proposed architecture.

Optimal Kinematics Design of an Industrial Robot Family

Product family design is a well recognized method to address the demands of mass customization. A potential drawback of product families is that the performance of individual members are reduced due to the constraints added by the common platform, i.e. parts and components need to be shared by other family members. This paper presents a formal mathematical framework where the product family design problem is stated as an optimization problem and where optimization is used to find an optimal product family. The object of study is kinematics design of a family of industrial robots. The robot is a serial manipulator where different robots share arms from a common platform. The objective is to show the trade-off between the size of the common platform and the kinematics performance of the robot.

Heat Compensation in Buildings Using Thermoelectric Windows: An Energy Efficient Window Technology

In this paper, we explore the design of thermoelectric (TE) windows for applications in building structures. Thermoelectric windows are equipped with TE units in the window frame to provide a heat absorption power, given a direct current input. We explore the design performance of the TE window to compensate for its own heat gains. While existing energy efficient windows have made advances towards reducing the heat transfer through them, they still depend on the building’s heating, ventilation and air-conditioning (HVAC) system to compensate for their heat gains. Our research explores the design of a window that can actively compensate for the passive heat flow through the window panes, and to do so with a better coefficient of performance (COP) than conventional HVAC systems. We also optimize the TE window design, and present results of the potential performance for practical applications in the building structure. For the geographic locations considered (Hawaii and Miami), the results are promising. Interestingly, the proposed TE window design actively compensates for the conduction heat gains with a COP greater than three, while that of conventional systems is typically less than three.

An Improved Initial Population Strategy for Compliant Mechanism Designs Using Evolutionary Optimization

In this paper, an improved initial random population strategy using a binary (0–1) representation of continuum structures is developed for evolving the topologies of path generating complaint mechanism. It helps the evolutionary optimization procedure to start with the structures which are free from impracticalities such as ‘checker-board’ pattern and disconnected ‘floating’ material. For generating an improved initial population, intermediate points are created randomly and the support, loading and output regions of a structure are connected through these intermediate points by straight lines. Thereafter, a material is assigned to those grids only where these straight lines pass. In the present study, single and two-objective optimization problems are solved using a local search based evolutionary optimization (NSGA-II) procedure. The single objective optimization problem is formulated by minimizing the weight of structure and a two-objective optimization problem deals with the simultaneous minimization of weight and input energy supplied to the structure. In both cases, an optimization problem is subjected to constraints limiting the allowed deviation at each precision point of a prescribed path so that the task of generating a user-defined path is accomplished and limiting the maximum stress to be within the allowable strength of material. Non-dominated solutions obtained after NSGA-II run are further improved by a local search procedure. Motivation behind the two-objective study is to find the trade-off optimal solutions so that diverse non-dominated topologies of complaint mechanism can be evolved in one run of optimization procedure. The obtained results of two-objective optimization study is compared with an usual study in which material in each grid is assigned at random for creating an initial population of continuum structures. Due to the use of improved initial population, the obtained non-dominated solutions outperform that of the usual study. Different shapes and nature of connectivity of the members of support, loading and output regions of the non-dominated solutions are evolved which will allow the designers to understand the topological changes which made the trade-off and will be helpful in choosing a particular solution for practice.

A Structure-Based Approach to Measuring Adaptability of Product Design

Adaptable design aims to extend the utilities of designs and products. Adaptability is classified into product and design adaptabilities. Product adaptability indicates that functionality and life can be extended for both economical and environmental benefits. Design adaptability improves design reuse by using existing designs to develop new designs more efficiently. To evaluate adaptable design, it is necessary to develop a method for quantitative measurement of the adaptability of products. A new method has been developed that first analyzes the independencies of functions and functional modules and then evaluates the adaptability of interfaces with two indices, as well as the performances of adaptive requirements. The effectiveness of the proposed method is demonstrated by an illustrative example of personal computer motherboards. The results show that the method can evaluate and reveal product adaptability for improving design and providing innovative design.

Shape Optimization of a Camoid Follower Surface

Camoids are three dimensional cams that can produce more complex follower output than plain disc cams. A camoid follower motion is described by a surface rather than a curve. The camoid profile can be directly synthesized once the follower surface is fully described. To define a camoid follower motion surface it is required that the surface pass by all predefined constraints. Constraints can be follower position, velocity and acceleration. These design constraints are scattered all along the camoid follower surface. Hence a fitting technique is needed to satisfy these constraints which include position and its derivatives (velocity and acceleration). Furthermore if the fitting function can be of a parametric nature, then it would be possible to optimize the follower surface to obtain better performance according to a specific objective. Previous research has established a method to fit camoid follower surface positions, but did not tackle the satisfaction of derivative constraints. This paper presents a method for defining a camoid follower characteristic surface B-Splines on two steps first synthesizing the sectional cam curves then using a surface interpolation technique to generate the follower characteristic surface. The fitting technique is parametric in nature which allows for its optimization. Real coded Genetic algorithms are used to optimize the parameters of the surface to meet a specified objective function. A demonstration problem to illustrate the suggested methodology is presented.

A Pareto Approach to Aligning Public and Private Objectives in Vehicle Design

The quest for producing vehicles friendlier to the environment is often impeded by the fact that a producer private good objective, such as maximum profit, competes with the public good objective of minimizing impact on the environment. Contrary to commercial claims, there may be no defined decision maker in the vehicle production and consumption process who takes ownership of the public good objective, except perhaps the government. One way ecofriendly products could become more successful in the marketplace is if public and private good objectives become more aligned to each other. This paper introduces three metrics for comparing Pareto curves in bi-objective problems in terms of relative level of objective competition. The paper also presents a quantitative way of studying an individual firm’s trade-off between profit and fuel consumption for automotive products, currently undergoing an historic evolution in their design. We show how changes in technology, preferences, competition, and regulatory scenarios lead to Pareto frontier changes, possibly eliminating it altogether.

A Comparison of Virtual Condition Cylinder Evaluation Methods in Coordinate Metrology

When a cylindrical datum feature is specified at maximum material condition (MMC) or least material condition (LMC) a unique circumstance arises: a virtual condition (VC) cylindrical boundary must be defined [1]. The geometric relationship between a cylindrical point cloud obtained from inspection equipment and a VC cylinder has not been specifically addressed in previous research. In this research, novel approaches to this geometric analysis are presented, analyzed, and validated. Two of the proposed methods are new interpretations of established methods applied to this unique geometric circumstance: least squares and the maximum inscribing cylinder (MIC) or minimum circumscribing cylinder (MCC). The third method, the Hull Normal method, is a novel approach specifically developed to address the VC cylinder problem. Each of the proposed methods utilizes a different amount of sampled data, leading to various levels of sensitivity to sample size and error. The three methods were applied to different cylindrical forms, utilizing various sampling techniques and sample sizes. Trends across sample size were analyzed to assess the variation in axial orientation when compared to the true geometric form, and a relevant case study explores the applicability of these methods in real world applications.

Contact Analysis Between a Moving Solid and the Boundary of Its Swept Volume

The modeling of many practical problems in design and manufacturing involving moving objects relies on sweeps and their boundaries, which are mathematically described by the envelopes to the family of shapes generated by the moving object. In many problems, such as the design and analysis of higher pairs or tool path planning, contact changes between the moving object and the boundary of its swept volume become critical because they often translate into functional changes of the system under consideration. However, the difficulty of this task quickly escalates beyond the reach of existing approaches as the complexity of the shape and motion increases. We recently proposed a sweep boundary evaluator for general sweeps in conjunction with efficient point sampling and surface reconstruction algorithms that relies on our novel point membership classification (PMC) test for general solid sweeps. In this paper we describe a new approach that automates the prediction of changes in the state of contact between a shape of arbitrary complexity moving according to an affine motion, and the boundary of its swept set. We show that we can predict when and where such contact changes occur with only minimal additional computational cost by exploiting the data output by our sweep boundary evaluator. We discuss the problem and the associated computational issues in a 2D framework, and we conclude by discussing the extension of our approach to 3D moving objects.

Assessing Functional and Shape Differentiation Within a Family of Products

Market differentiation strategies must identify competitive advantages when offering a line of products varying in features, price, quality, and/or aesthetics. Although this concept is well-known, many companies still have difficulties positioning their own products within their own product lines and against competitors. Few approaches combine two or more facets to answer the product differentiation problem. In this study, two novel indices are proposed to audit shape and functional differentiation within a family of products. The shape index appraises the shape similarity between the products upon digitization, while the functional assessment is based on functions characteristics of the product. Customers’ perception data is obtained experimentally and compared to these indices to validate the result. Pairs of products are evaluated, and the average scores are considered as the indices for a product family. A case study illustrates the usage of these two indices and performance of these tools as well. This approach can be used during detailed studies as well as early stages of the design process to help validate product family positioning.