Decision-based process design for shortening the lead time for mold design and production

We propose “Decision-based process design” for reducing the process time of the design and production of molds. This method reviews the human processes of making decisions for setting unknown parameters, and reduces their process time by actively reducing the operations with such decisions. We applied decision-based process design to the design and production of injection molding cellular phone shells, together with 3D-CAD and high speed machining. The application reduced the number of decision operations to 77, 13% of the total number of operations, and drastically decreased the process time by 86% down to 50 hours.     

Decoupling Executions in Navigating Manufacturing Processes for Shortening Lead Time and Its Implementation to an Unmanned Machine Shop

A new navigation method that decouples manufacturing processes of tailor-made products has been developed for shortening lead time. Axiomatic Design expresses manufacturing processes with two design equations; one with functional requirement (FR) of “defining process” and design parameter (DP) of “decisions in process,” and the other with FR of “predicting completion time of product” and DP of “priority of product.” Once formulated, decoupling the system with the rules of “No feedback” and “No moving up” effectively shortens lead time. Applying the navigation methodology to a real unmanned machine shop of molds, eventually shortened it from 44 to 7.7 days.     

Sustainability of abrasive processes

This paper presents an overview of research on sustainability of abrasive processes. It incorporates results from a round robin study on “energy-efficiency of abrasive processes” which has been carried out within the scientific technical committee “abrasive processes” (STC G) of CIRP, the content of technical presentations in STC G, and the results of a comprehensive literature study. The approach to sustainability includes environmental, social, and economic sustainability in accordance with the definition proposed in the Brundtland Report of the United Nations [156]. The main focus is on environmental and social sustainability. Economic sustainability will be considered as manufacturing productivity.     

Complexity in design of technical systems

This paper discusses the complexity of technical systems resulted from engineering design. We defined the “overall difficulty” of such a system as consisting of “inborn complication” due to customer needs and external constraints as well as “acquired complexity” associated with uncertainty in satisfying the functional requirements caused by design decisions. An ideal design should lead to the least difficult technical system by minimizing inborn complication and eliminating acquired complexity. To achieve this design ideality, strategies of using the Axiomatic Design theory and the Design-Centric Complexity theory are introduced to guide the creation and improvement of complex time-independent and time-dependent technical systems.     

Design methodologies: Industrial and educational applications

The field of Design Theory and Methodology has a rich collection of research results that has been taught at educational institutions as well as applied to design practices. First, this keynote paper describes some methods to classify them. It then illustrates individual theories and methodologies focusing on industrial and educational use. Theories and methodologies that are found most practically useful are “math-based methods”, “methodologies to achieve concrete design goals,” and “process methodologies”, while at educational institutes in addition to these, traditional design methodologies are also taught. The paper discusses this gap between practical and educational usages.     

Defects in axisymmetrically drawn bars caused by longitudinal superficial imperfections in the initial material

Metallic wires and bars are produced by axisymmetric drawing of hot rolled material and must not display surface defects that impair their service use or whose opening during subsequent cold forming is unacceptable. Experimental and numerical (Finite Element Analysis - FEA) analyses of the evolution of longitudinal superficial defects in copper bars during seven successive axisymmetric drawing passes are presented. The initial experimental defects displayed a rectangular cross-section, 1 mm wide and 0.3, 0.6 or 0.9 mm deep; the two latter evolved after drawing into the “inverted Y” defect already reported in the literature, but the former led to a newly reported “double V” defect. There was a good agreement between the results from experiments and FEA and further analyses were then carried only through FEA, covering two other materials (a carbon steel and aluminum), a decrease in the defect width (from 1.0 to 0.5 mm) and an inclination of 15° or 30° of the walls of the 1.0 mm wide rectangular defect. The defect evolution was similar for the three materials; the decrease in the defect width enhanced the incidence of “inverted Y” defects, and indicated the formation of newly reported “Radial” and “Inverted V” defects. The inclination of the defect walls led to the possibility of a change from the “inverted Y” defect to a “double V” one. Defects 0.3 mm deep and with walls at 30° were eliminated by the present drawing sequence. A novel approach for the prediction of the effect of the initial superficial imperfections on the final drawn stock, through the so called “defect evolution maps” is presented.     

Scratch resistance of platinum-vanadium single and multilayer systems

The effects of annealing on coating morphology and scratch resistance have been studied in several single and multilayered Pt-V coated systems. The changes in coating morphology included the formation of distinctive “square shape precipitates”, increased surface roughness, coating thickening and cracking. The results show that scratch resistance was affected by coating thickness, the sequence of deposited layers and Pt-V phases induced by annealing. The scratch resistance was improved for all coated systems by annealing. However, there is an indication that a large volume fraction of PtV₃ formed at 900 °C/45 min significantly increased the critical load at which the coating failed. This result will be the base for further study on the development of targeted phases to improve the surface characteristics for specific coating applications.     

The effect of partially cut-out blanks on geometric accuracy in incremental sheet forming

Industrial requirements for accuracy in metal sheet components are typically ±0.2 mm where current incremental sheet forming processes are capable of an accuracy of only ±3 mm. Several approaches based on process design modifications or control strategies are being developed to overcome this problem, but none has as yet been entirely successful. This paper proposes and examines a new approach in which the area to be formed within the blank is “partially cut-out” using a water jet or laser cutter. The aim of this partial cut-out is to localise deformation to the area over which the tool travels and thus reduce the difference between a part made by a “contour tool path” and the target product geometry. Several design options are considered, and the approach is evaluated with one simple and one complex part. The results indicate that partially cut-out blanks lead to slightly more accurate forming than conventional blanks when unsupported, but that the accuracy improvement is less than that which is achieved by use of a stiff cut-out supporting plate. The results include an experimental investigation of residual stresses and springback in incremental sheet forming.     

Lower boundary in metal explosive welding. Evolution of ideas

Like in any solid state method of metal bonding, a weldability area exists for each pair of explosion welded materials. Establishing the lower boundary of explosive welding is a relevant task because it makes it possible to specify the parameters of the explosive welding process. The existing concepts and models of the lower boundary are comprehensively reviewed, and the evolution of ideas on the subject is described. The axis “average mass of the explosion welded plates” is added to the original representation of the welding areas in the “hydrodynamic” coordinates “collision angle-collision velocity”. Such an approach makes it possible to analyse the bonding process in terms of energy. A new parameter - the pressure deforming pulse - is proposed. This parameter depends on the collision conditions and relates the pressure in the contact area to the time period within which the pressure operates. Thus, it presents the explosive welding lower boundary in the physical coordinates “pressure-time-temperature”.     

An Axiomatic Approach for “Target Cascading” of Parametric Design of Engineering Systems

Complex engineering system realization involves finding out design specifications that simultaneously achieve performance objectives at different levels. A common practice in industry is to adopt “Target Cascading” to obtain proper settings of the performance objectives, and find out those design specifications, not necessarily optimal, but satisfying all the desirable component-level, subsystem-level and system-level performance objectives. In this paper, an Axiomatic Approach to “Target Cascading” (AATC) is presented to improve the current “Target Cascading” process. AATC uses axioms to guide the decompositions of performance objectives, and an integration of a hybrid meta-modeling tool and direct synthesis method to enhance both robustness and efficiency. The preliminary results of AATC's industrial applications demonstrate its advantage in improving productivity at the early stage parametric design, especially for complex engineering systems.     

Role of Bayer solution concentration and temperature in stress corrosion cracking susceptibility of steel

To improve the efficiency of the Bayer process for the extraction of alumina from Bauxite ore, there is a push for increasing processing temperature and caustic concentrations, which has also led to an increased concern for caustic embrittlement. In this study, the caustic cracking behaviour of steel in Bayer solutions of 2.5, 5, 7.5 and 10 mol dm⁻³ “free caustic” concentrations have been studied at different temperatures using pre-cracked circumferential notch tensile specimens. It has been observed that at 100 °C, steel is susceptible to caustic cracking in each of the four Bayer solutions. Caustic cracking has also been observed at temperatures as low as 55 °C. Tests were also conducted using only the notched specimens (i.e., without pre-cracking) in a 7.5 mol dm⁻³ “free caustic” Bayer solution at 120 °C to study the stress corrosion crack formation and propagation behaviour in blunt notches.     

Design knowledge extraction from scenario-based databases using associative search engine for FR-induced decisions

The authors set the functional requirement of “reduce your own risk” and ran sessions of associative search to extract useful knowledge from databases. Ninety engineers found the most analogous knowledge using the associative search engine “GETA/IMAGINE” on scenario-based databases “Failure Knowledge Database” and “100 Scenarios of Failure.” Above 60% of their risk concern cases successfully reached the most analogous accident cases or failure scenarios from either database in about 10 min. Associative search can aid the designer in selecting design solutions for the functional domain.     

Microstructure characterization of as-fabricated and 475 °C annealed U-7 wt.% Mo dispersion fuel in Al-Si alloy matrix

High-density uranium (U) alloys with an increased concentration of U are being examined for the development of research and test reactors with low enriched metallic fuels. The U-Mo fuel alloy dispersed in Al-Si alloy has attracted particular interest for this application. This paper reports our detailed characterization results of as-fabricated and annealed (475 °C for 4 h) U-Mo dispersion fuels in Al-Si matrix with a Si concentration of 2 and 5 wt.%, named as “As2Si”, “As5Si”, “An2Si”, “An5Si” accordingly. Techniques employed for the characterization include scanning electron microscopy and transmission electron microscopy with specimen prepared by focused ion beam in situ lift-out. Fuel plates with Al-5 wt.% Si matrix consistently yielded thicker interaction layers developed between U-Mo particles and Al-Si matrix, than those with Al-2 wt.% Si matrix, given the same processing parameters. A single layer of interaction zone was observed in as-fabricated samples (i.e., “As2Si”, “As5Si”), and this layer mainly consisted of U₃Si₃Al₂ phase. The annealed samples contained a two-layered interaction zone, with a Si-rich layer near the U-Mo side, and an Al-rich layer near the Al-Si matrix side. The U₃Si₅ appeared as the main phase in the Si-rich layer in “An2Si” sample, while both U₃Si₅ and U₃Si₃Al₂ were identified in sample “An5Si”. The Al-rich layer in sample “An2Si” was amorphous, whereas that in sample “An5Si” mostly consisted of crystalline U(Al,Si)₃, along with a small fraction of U(Al,Si)₄ and U₆Mo₄Al₄₃ phases. The influence of Si on the diffusion and reaction in the development of interaction layers in U(Mo)/Al(Si) is discussed in the light of growth-controlling mechanisms and irradiation performance.     

Development of a new lean lubrication system for near dry machining process

The minimal quantity of lubricant supply (MQL) technique has been applied to environment friendly machining processes. However, in the MQL technique, a large volume of oil mist is discharged to the environment. In this paper, a new lean lubrication system for a near dry machining process called “direct oil drop supply system (DOS)” is proposed. The performance of the DOS technique was evaluated by the milling processes. The DOS technique can supply a very small oil drop directly to the cutting edge without making oil mist, and the DOS shows almost same machining performances compared to the MQL technique.     

‘Odds Algorithm’-based Opportunistic Maintenance Task Execution for Preserving Product Conditions

Today, a new role for maintenance exists to enhance the eco-efficiency of the product life cycle. The concept of “life cycle maintenance” emerged to stress this role leading to push, at the manufacturing stage, an innovative culture wherein maintenance activities become of equal importance to actual production activities. This equivalence requires mainly considering the integration of the maintenance and production strategy planning for developing opportunistic maintenance task keeping conjointly the product - production - equipment performances. In this paper, a novel approach is proposed for integrating maintenance and production planning. The approach uses the “odds algorithm” and is based upon the theory of optimal stopping. The objective is to select, among all the production stops already planned, those which will be optimal to develop maintenance tasks keeping the expected product conditions. It combines criteria such as functional performance and component reliability. Approach feasibility is shown on a practical example.     

Homogeneous surface coating of bolts, nuts, and screws by barrel-sputtering technique

Our newly developed “barrel-sputtering” technique has been employed for the surface coating of solid substrates with complex shapes such as bolts, nuts, and screws. The entire surface of the iron bolts and nuts including the flank and the root in the thread is homogeneously coated with the Au film. SEM measurements reveals that the surface of the Au film is very smooth. In the SEM measurements of the cross-sectional area, it is found that the Au film possess uniform thickness without any significant defects and/or pits. The Au film coating can also be successfully conducted on polycarbonate bolts and small SUS screws. The results provide evidences that the sputter deposition takes place in “three-dimensionally.”     

Galvanic corrosion of magnesium alloy AZ91D in contact with an aluminium alloy, steel and zinc

An investigation was carried out into the galvanic corrosion of magnesium alloy AZ91D in contact with zinc, aluminium alloy A380 and 4150 steel. Specially designed test panels were used to measure galvanic currents under salt spray conditions. It was found that the distributions of the galvanic current densities on AZ91D and on the cathodes were different. An insulating spacer between the AZ91D anode and the cathodes could not eliminate galvanic corrosion. Steel was the worst cathode and aluminium the least aggressive to AZ91D. Corrosion products from the anode and cathodes appeared to be able to affect the galvanic corrosion process through an “alkalisation”, “passivation”, “poisoning” effect or “shortcut” effect.     

Improvement of thermally sprayed abradable coating by microstructure control

The aim of this work was to characterise the microstructure of recently developed abradable materials for providing a sealing between rotating and stationary parts in aerospace turbine engines. The investigated materials were two coatings obtained by thermal spraying of composite powder particles from the AlSi-hBN and NiCrAl-bentonite systems. X-ray diffraction and scanning electron microscopy were used to analyse the microstructure and identify the structural elements of the coatings. These structural elements: the coarse porosities, the metallic binding phase and the embedded “abradable” particles were analysed by quantitative metallography. In particular, an image analysis procedure has been established to quantify different geometrical parameters related to the shape, size and orientation distribution, of these structural elements.     

Effect of phase transformation latent heat on prediction accuracy of strip laminar cooling

The cooling of hot-rolled strips is of great importance due to its effects on the mechanical and metallurgical properties of the final product. In this paper, the effect of phase transformation on accurate prediction of strip temperature at the run-out table is investigated. For this purpose, a model is developed for the heat transfer and phase transformation in hot-rolled strips during the cooling process. The model is capable of calculating strip temperature and the volume fraction of steel phases during cooling at the run-out table under the two different situations of “regarding phase transformation latent heat” (RPTLH) and “disregarding phase transformation latent heat” (DPTLH). Actual data from a hot rolling line were used to evaluate the accuracy of the model. The model was used to predict strip temperature under the above two scenarios. Comparison of actual and predicted values in the two DPTLH and RPTLH cases revealed that disregarding the released heat would lead to considerable errors in temperature predictions. The results for different steel grades predicted by the model also showed that the higher the carbon content of the steel, the higher the error due to disregarding phase transformation latent heat.     

Effect of molten pool boundaries on the mechanical properties of selective laser melting parts

Selective laser melting (SLM) manufactures components through the overlapping of multi-track and multi-layer molten pools of metal powders, resulting in two types of molten pool boundaries (MPBs), “layer–layer” and “track–track” MPBs, remaining in SLM parts. The microstructure of MPBs exhibits a complex and regular spatial topological structure. There is a coarse grain zone below the MPBs and nonmetallic elements (C, O, Si) near the MPBs are in an unstable state. Long and thin columnar grains with the same orientations distribute on two sides of the “layer–layer” MPBs, whereas the columnar grains on both sides of “track–track” MPBs have different orientations. The “track–track” MPBs are short and intersect with “layer–layer” MPBs at some points and form acute angles, where cracks are initiated when applied with external loads. The effect of the MPBs on microscopic slipping, macroscopic ductility and fracture mechanism of the SLM parts made along different directions, which were exerted a tensile loading in the as-built condition without heat treatment, was analyzed and evaluated using slip theory and experiments. The results reveal that the MPBs have a significant impact on the microscopic slipping at the loading, macroscopic plastic behavior and fracture mode, and are one of the main reasons for the obvious anisotropy and low ductility of SLM parts.