B.G. Bryden, D.I. Wimpenny and I.R. Pashby
Lastform, a three year EPSRC (IMI) programme, has investigated metallic laminating techniques to produce large‐scale production capable tooling. This work is intended as an…
Abstract
Lastform, a three year EPSRC (IMI) programme, has investigated metallic laminating techniques to produce large‐scale production capable tooling. This work is intended as an overview of the research and development performed at the University of Warwick’s Warwick manufacturing Group. The programme was a collaboration between seven industrial partners and three universities with each university having a discreet area of research. The focus at Warwick was to establish robust methods of joining metal sheets to form tools for different production processes. Bonding mediums, test parts for process evaluation, sample tools and production tools are described. The advantages of metal laminating for different processes are evaluated. Results include reduced lead‐time and cost savings and enhanced processing capability by the use of conformable heating or cooling channels.
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This paper outlines a method of sequentially joining steel laminations together using a high strength brazed joint to produce laminated tools. Individual joints were produced by…
Abstract
This paper outlines a method of sequentially joining steel laminations together using a high strength brazed joint to produce laminated tools. Individual joints were produced by using a heated platen rather than a furnace. Lap shear test samples were used to evaluate the tensile strengths of bonded laminates. Two laminate gauges were tested, 0.8mm and 1.6mm. Ranging trials were undertaken to determine optimum time to produce the joint. Constants for the trials were platen temperature, laminate material, braze material, joint area and joining pressure. At optimum conditions, that is the least time taken for highest tensile strength, the 0.8mm laminate averaged a strength of 4.7kN in 120 seconds’ heating time and the 1.6mm laminate averaged 9.3kN in 210 seconds.
High‐powered diode lasers are becoming increasingly used in manufacturing for transmission welding of thermoplastic materials. This process can replace many of the traditional…
Abstract
High‐powered diode lasers are becoming increasingly used in manufacturing for transmission welding of thermoplastic materials. This process can replace many of the traditional techniques such as ultrasonic welding. Benefits include being a non‐contact process that can encapsulate sensitive electronic housings without damage. This is described in an electronic throttle assembly case study.
Mohammad Hayasi and Bahram Asiabanpour
The main aim of this study is to generate curved-form cut on the edge of an adaptive layer. The resulting surface would have much less geometry deviation error and closely fit its…
Abstract
Purpose
The main aim of this study is to generate curved-form cut on the edge of an adaptive layer. The resulting surface would have much less geometry deviation error and closely fit its computer aided design (CAD) model boundary.
Design/methodology/approach
This method is inspired by the manual peeling of an apple in which a knife's orientation and movement are continuously changed and adjusted to cut each slice with minimum waste. In this method, topology and geometry information are extracted from the previously generated adaptive layers. Then, the thickness of an adaptive layer and the bottom and top contours of the adjacent layers are fed into the proposed algorithm in the form of the contour and normal vector to create curved-form sloping surfaces. Following curved-form adaptive slicing, a customized machine path compatible with a five-axis abrasive waterjet (AWJ) machine will be generated for any user-defined sheet thicknesses.
Findings
The implemented system yields curved-form adaptive slices for a variety of models with diverse types of surfaces (e.g. flat, convex, and concave), different slicing direction, and different number of sheets with different thicknesses. The decrease in layer thickness and increase of the number of the sloped cuts can make the prototype as close as needed to the CAD model.
Research limitations/implications
The algorithm is designed for use with five-axis AWJ cutting of any kind of geometrical complex surfaces. Future research would deal with the nesting problem of the layers being spread on the predefined sheet as the input to the five-axis AWJ cutter machine to minimize the cutting waste.
Practical implications
The algorithm generates adaptive layers with concave or convex curved-form surfaces that conform closely to the surface of original CAD model. This will pave the way for the accurate fabrication of metallic functional parts and tooling that are made by the attachment of one layer to another. Validation of the output has been tested only as the simulation model. The next step is the customization of the output for the physical tests on a variety of five-axis machines.
Originality/value
This paper proposes a new close to CAD design sloped-edge adaptive slicing algorithm applicable to a variety of five-axis processes that allow variable thickness layering and slicing in different orientations (e.g. AWJ, laser, or plasma cutting). Slices can later be bonded to build fully solid prototypes.
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Robert E. Williams, Daniel F. Walczyk and Hoang T. Dang
To determine the feasibility of sealing and finishing conformal cooling/heating channels in profiled edge laminae (PEL) rapid tooling (RT) using abrasive flow machining (AFM).
Abstract
Purpose
To determine the feasibility of sealing and finishing conformal cooling/heating channels in profiled edge laminae (PEL) rapid tooling (RT) using abrasive flow machining (AFM).
Design/methodology/approach
Sample PEL tools constructed of both aluminum and steel were designed and assembled for finishing by AFM. A simple design of experiments approach was utilized. Output parameters of interest included the material removal, surface roughness improvement and, most importantly, the ability to withstand a pressurized oil leak test.
Findings
AFM significantly improved the finish in the channels for aluminum and steel PEL tooling. Leak testing found that AFM also improved the sealing of both stacks at static pressures up to 690 kPa. The steel tooling appeared to benefit more from the AFM process. It has been postulated that the primary cause of the sealing is the plastic deformation of workpiece material in the plowing mode.
Research limitations/implications
The conformal channels studied had a simple cross‐sectional geometry and straight runs. The PEL tools were only made of two materials. However, the research results show great promise for large RT, including thermoforming and composite forming molds where temperature control is a critical issue.
Practical implications
The ability to seal the interfaces between individual laminae expands the potential application of AFM tremendously. AFM also has the potential to finish a wide range of internal passages in a variety of RT.
Originality/value
AFM has been previously used for finishing stereolithography prototypes. This is the first known attempt to seal and finish channels in laminated RT using AFM.
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Gregory John Gibbons, Robert G. Hansell, A.J. Norwood and P.M. Dickens
This paper details the development of a rapid tooling manufacturing route for the gravity and high‐pressure die‐casting industries, resulting from an EPSRC funded collaborative…
Abstract
This paper details the development of a rapid tooling manufacturing route for the gravity and high‐pressure die‐casting industries, resulting from an EPSRC funded collaborative research project between the Universities of Warwick, Loughborough and DeMontfort, with industrial support from, amongst others, MG Rover, TRW Automotive, Sulzer Metco UK Ltd and Kemlows Diecasting Products Ltd. The developed process offers the rapid generation of mould tools from laser‐cut laminated sheets of H13 steel, bolted or brazed together and finish machined. The paper discusses the down‐selection of materials, bonding methods and machining methods, the effect of conformal cooling channels on process efficiency, and the evaluation of a number of test tools developed for the industrial partners. The paper also demonstrates the cost and time advantages (up to 50 and 54 per cent, respectively) of the tooling route compared to traditional fabrication methods.
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Hossein Ahari, Amir Khajepour and Sanjeev Bedi
This paper proposes sheet thickness determination in manufacturing of laminated dies as an optimization problem. The aim of this optimization procedure is finding the best set of…
Abstract
Purpose
This paper proposes sheet thickness determination in manufacturing of laminated dies as an optimization problem. The aim of this optimization procedure is finding the best set of thicknesses which minimizes the volume deviation between actual computer‐aided design (CAD) model and assembled slices.
Design/methodology/approach
This works uses a modified version of genetic algorithms for the optimization purpose. Each set of thicknesses that can cover the whole CAD model surface is considered as a chromosome. Genetic operators such as crossover and mutation have to be modified to be used in this application.
Findings
A new method for finding the total volume deviation between assembled slices and the actual CAD model was developed in this research. On the other hand, the results show how the program can automate the slice plane locations search process.
Research limitations/implications
Premature convergence does not allow the algorithm to search the entire solution space before getting trapped in a local optimum. Even the mutation operator cannot postpone this untimely convergence.
Practical implications
The proposed method is a good substitute for the manual methods that are currently used in industry. These experience‐based methods are mostly based on the decision made by a well‐trained technician on picking up the thicknesses for a specific CAD model.
Originality/value
This is the first attempt at optimizing the slicing method in laminated tooling. Other methods are mostly based on rapid prototyping (RP) and they are not applicable in the laminated tooling process since, despite RP, here not all optimization outputs can be used in practical procedure.
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Abstract
Purpose
The purpose of this paper is to present a novel rapid prototyping (RP) approach and verifying its feasibility. This alternative solution is to bring several merits from both selective laser sintering and laminated object manufacturing.
Design/methodology/approach
The phenolic resin coated sand is used in this method. It could be cured at an appropriate temperature and be invalidated at a higher one. Therefore, the fabrication flows from laser cutting along slice profiles to a bulk curing heating after stacking up. Finally, the workpiece may be detached out of the excess material. Experiments and modeling on laser scanning are conducted to optimize the processing parameters, which, along with the direct slicing strategy, guarantee the part performance.
Findings
A novel prototyping system is developed comprising the software package and prototyping machine, through which several specimens are fabricated. The results show the feasibility of the proposed RP method.
Originality/value
This research brings the applicability of a hybrid solution: profile invalidation RP.