A J Medland

Model Spaces and their use in Mechanism Simulation

Computer aided design systems tend to work simply in terms of geometric entities. Any intelligence that could be implanted in the system would, however, need to deal with the function of the design being described. This requires the system to handle the geometry at a higher level. One approach is to use model spaces that hold groups of geometric entities and preserve some of the associations between them. A software system is described that works in terms of such spaces and allows hierarchies of spaces to be built up. The hierarchy, however, is not sufficient for a complete description of every design. There is a need to add extra constraints. The software allows these to be entered and automatically tries to maintain them as being true. The use of this approach is illustrated by the simulation of the motion of a mechanism from a high-speed packaging machine.

Late customisation: issues of mass customisation in the food industry

The strategy of mass customisation is being increasingly adopted as companies seek to exploit market trends for greater product variety and individualisation. The implications of changing to mass customisation practice are considerable, where traditional contradictions of high volume and extensive product variety require being reconciled. The literature discusses the need for an integrated approach to mass customisation across all business functions if micro-segmentation of markets is to be profitably pursued, and the current paper investigates extending the paradigm of mass customisation into the, until now, poorly represented sector of food processing. Product design and manufacturing system design for mass customisation are reviewed and contrasted with good practice in more traditional mass customisation industries.

The representation and handling of constraints for the design, analysis, and optimization of high speed machinery

High speed machinery has played and continues to play a vital role in the manufacture and production of consumer goods. In the design of high speed systems there are two key considerations: power transmission and motion control. Although there is considerable computer-based support for the design of systems to achieve requirements of power transmission, there is only limited support for the design of systems to deliver complex motion control. This is particularly the case where mechanism and linkage systems are considered in order to achieve large displacements and intricate paths involving reentrant and reciprocating components. One explanation for this relative lack of supportive tools is the underlying reasoning and analysis techniques implemented within many commercial and research software environments. To overcome these limitations a constraint-based approach has been employed to provide the fundamental elements of a design environment for mechanisms and machine systems. The design environment provides support for the transition from concept to embodiment stages of the design process and the subsequent stages of detailed design and optimization. In contrast to many research approaches the design environment presented in this paper has been created and developed through close collaboration with industry and through extensive application to real design scenarios. First, the underlying representations and methods are presented. The fundamental elements of the design environment are then described and its capabilities discussed with particular reference to the use of constraints in design.

The Integration of Coordinate Measuring Machines within a Design and Manufacturing Environment

The role of the coordinate measuring machine within the inspection process has changed throughout its brief development. With its integration with industrial computer aided design (CAD) systems, its role is to change yet again. This paper presents the difficulties and limitations of current practice and identifies the inputs and decisions that need to be made within an integrated manufacturing environment. A research programme was undertaken to investigate an approach based upon intelligent communications between systems. This led to the creation of a demonstration system that was employed in the measurement of industrial components. A case study, using a standard test block, is included to illustrate the processes undertaken. This includes feature identification, probe calibration and selection strategies and automatic re-routing to minimize changes in probes and orientations. It is proposed that the approach demonstrated can be incorporated within a concurrent engineering environment to provide feedback and information about machine adjustments through a constraint modelling process.

Energy method for modelling delamination buckling in geometrically constrained systems

Abstract Delamination buckling analysis of laminates is of considerable interest to the mechanical and materials engineering sectors, as well as having wider applications in geology and civil engineering. With advances in computing power, the ability to model ever increasingly complex problems at more detailed levels becomes more of a reality. However, many of the common finite element packages, with the exception of all but the most specialized, do not perform particularly well where complex non-linear problems are dealt with. In many cases, these packages can fail to determine the full range of solutions or accurately predict the properties and geometry of the final state. This is particularly the case where large deformations and buckling of laminates are considered. Because of this, many researchers prefer to use what they perceive to be more reliable techniques, such as the symbolic computation of the underlying differential equations, rather than finite element approaches. The use of finite element packages is further frustrated by the steep learning curve and implicit restrictions imposed by using third-party software. In this paper, a finite element approach and an energy formulation method are considered and used to model the delamination buckling in a geometrically constrained system. These methods are compared with experimental results and their relative merits are discussed. In particular, the accuracy and the ability to represent the geometry of the buckled system are discussed. Both the finite element approach and the energy formulation are described in detail and the numerical results are compared.

Interpretation of errors from inspection results

This paper looks at ways in which inferences about errors in manufacturing can be made by comparing inspection points with a solid model of the desired component. The approach is to form a hierarchy of stages within a typical manufacturing process, and to try to match the inspected points associated with each with the computer model. This requires ‘best fit’ transforms to be found.

Finite element simulation of folding carton erection failure

Abstract In response to recent European Union (EU) regulations on packaging waste, the packaging industry requires greater fundamental understanding of the machine-material interactions that take place during packaging operations. Such an understanding is necessary to handle thinner lighter-weight materials, specify the material properties required for successful processing and design right-first-time machinery. The folding carton industry, in particular, has been affected by the new legislation and needs to realize the potential of computational tools for simulating the behaviour of packaging materials and generating the necessary understanding. This paper describes the creation and validation of a detailed finite element model of a carton during a common packaging operation. The model is applied here to address the problem of carton buckling. The carton was modelled using a linear elastic material definition with non-linear crease behaviour. Air inrush suction, which is believed to cause buckling, was quantified experimentally and incorporated using contact damping interactions. The results of the simulation are validated against high-speed video of carton production. The model successfully predicts the pattern of deformation of the carton during buckling and its increasing magnitude with production rate. The model can be applied to study the effects of variation in material properties, pack properties and machine settings. Such studies will improve responsiveness to change and will ultimately allow end-users to use thinner, lighter-weight materials in accordance with the EU regulations.

Simulating the behaviour of folded cartons during complex packing operations

Abstract The folding carton is a widely used packaging solution. Recent European Union packaging legislation has forced carton manufacturers to use lighter-weight grades of carton board. This typically results in a reduction in board stiffness, which can lead to decreased process efficacy or even prevent successful processing. In order to overcome this, end-users lower production rates and fine-tune packaging machine settings for each pack and material. This trial-and-error approach is necessary because the rules relating machine set-up to pack design and material properties are not generally well known. The present study addresses this fundamental issue through the creation of a finite-element computer simulation of carton processing. Mechanical testing was performed to ascertain the key mechanical properties of the carton walls and creases. The carton model was validated against the experimental results and was then subjected to the machine-material interactions that take place during complex packaging operations. The overall approach was validated and the simulation showed good agreement with the physical system. The results of the simulation can be used to determine guidelines relating machine set-up criteria to carton properties. This will improve responsiveness to change and will ultimately allow end-users to process thinner lighter-weight materials more effectively.

The performance envelope of forming shoulders and implications for design and manufacture

Abstract The production of packaging machinery is a highly competitive global market driven by the ever-increasing demands of customers and legislation. The fundamental design principles of many packaging machines are the result of incremental improvements made over the last few decades. This paper looks at the underlying theory for forming shoulders and, starting with previously published results, determines the performance envelope relating to certain critical parameters. The findings are discussed in the light of their relevance for the creation of new designs.

A design methodology to create constraint-based human movement patterns for ergonomic analysis

Non-fatal injury within industry could be reduced using predictive computer-aided design (CAD) human models to evaluate machinery designs at the concept stage. This paper introduces a constraint-based manikin model that can effectively predict movement patterns over a range of potential designs. The approach was centred upon a proposed methodology that sought key movement events and a movement descriptor as independent inputs to the model. Validation of a generated sit-to-stand case study movement showed the lumbar, hip, knee, and ankle joints to be accurate to within 4.2° across changes in the pace of movement and the designed environment. It is proposed that predictive models can now be generated for other chosen movements by employing the new methodology. Creating realistic CAD-based movement models that change appropriately as the designed environment changes allows industrial workstations and machinery controls to benefit from improved design. Thus, the abilities of the operator can be better matched with the tasks at hand, potentially reducing operator injury when in use.