Mold Industry Research Articles

Feedrate scheduling strategies for free-form surfaces

Free-form machining is one of the commonly used manufacturing processes for several industries such as automobile, aerospace, die and mold industries. In 3D complicated free-form surfaces, it is critical, but often difficult, to select applicable cutting conditions to achieve high productivity while maintaining high quality of parts. It is essential to optimize the feedrate in order to improve the machining efficiency of the ball-end milling. Conservative constant feedrate values have been mostly used up to now since there was a lock of physical models and optimization tools for the machining processes. The common approach used in feedrate scheduling is material removal rate (MRR) model. In the MRR based approach, feedrate is inversely proportional to either average or instantaneous volumetric removal rate. Commonly used CAM programs and NC code generators based on only the geometric and volumetric analysis, but they do not concern the physics of the free-form machining process yet. The new approach that is also introduced in this paper is based on the mechanics of the process. In other words, the force-based models in which feedrate is set to values which keep either average or instantaneous machining forces to prescribed values. In this study, both feedrate scheduling strategies are compared theoretically and experimentally for 3D ball-end milling of free-form surfaces. It is shown that MRR based feedrate strategy outputs higher feedrate values compared to force based feedrate strategy. High feedrate values of the MRR strategy increase the cutting forces extensively which can be damaging to the part quality and to the CNC Machine. When the new force based feedrate-scheduling strategy introduced in this paper is used, it is shown that the machining time can be decreased significantly along the tool path. The force-based feedrate scheduling strategy is tested under various cutting conditions and some of the results are presented in the paper.

MAPP – A web-based decision support system for the mould industry

This paper describes the MAPP, “Mould: Assistant Production Planner”, a web-based decision support system developed for the mould industry. MAPP addresses two subsystems considered fundamental by the managers of a case study company: (1) production planning and control and (2) information and document management. The production planning methodology implemented is based on the workload control concept developed at Lancaster University, adapted to the context of the moulds industry, under a Rapid Prototyping case study. The main objectives of this paper are to present a discussion of the system functions at the service of the planning methodology, and to explain the development decisions in the socio-technical context of the case study company. We conclude with a brief overview of issues raised in lab and field testing, along with some proposals for further research.

A Novel Adaptive Process Control for Injection Moulding of BMC and CIC Polyester Compounds

The formulation of unsaturated polyester Bulk Moulding Compounds (BMC) or Continuously Impregnated Compounds (CIC) induces a variation of their reactivity or viscosity, which reflects the heterogeneity of the material batches produced. This experimental study has pointed out the benefits brought by an advanced process control of the injection moulding holding stage (feedback control on the polymer pressure in the mould cavity with automatic set up of holding time) compared to a regular process control (feedback control on the hydraulic pressure). The advanced process control actually leads to the reduction of the scattering observed on bulk (weight, specific gravity), surface (porosity, roughness) or mechanical properties (Charpy impact strength). It allows smoothing the thermal perturbations induced by a manufacturing start-up, as well as the rheological perturbation due to the material batches heterogeneity that are frequently encountered in the unsaturated polyester compound injection moulding industry. This scattering decrease, centred on the mean value of the target properties, directly involves significant quality and productivity improvement.

A Novel Automatic Feedrate Adjustment Method for Die-Cavity Roughing

Sculptured surface machining is a critical process commonly used in die and mold industries. Since there is a lack of scientific tools in practical process planning stages, feedrates of CNC machining are selected based on previous experiences. In the selection of feedrate, the feedrate is set an individual conservative constant value all along the die cavity roughing processes in order to avoid undesirable results such as chipping, cutter breakage or over-cut due to excessive cutter deflection. Usually, volumetric models or vector force models used for optimizaton of feedrates must be created to get the variable feedrates along the tool path. Considering the die cavity roughing being a 2.5D cutting, a novel cutting force surface model is created based on orthogonal cutting tests to adjust the feedrates. The model is tested by a typical die-cavity roughing, thinning down machining time and balanced cutting-load can be attained. The presented feedrate scheduling characterized by balancing the cutting-loads in die-cavity roughing will be more significative in high speed machining.

FGM Mould with Fine Veins Rapidly Manufactured by Plasma Spraying

There is the advantage of continuity in organic structure and mechanical property for functionally gradient materials (FGMs), but it is unable to be used in the mould industry for the difficulty of the second machining up to now. In this study, a novel technology of FGM mould with fine veins fabricated by plasma spraying has been developed, which can easily realize the integration of FGM forming and deep machining of the mould. According to applied characteristic of plastic injection mould, WC-12%Co/NiCrAl powders are selected and the reasonable FGM coating has been prepared. Spraying processes have been investigated, such as fabrication of spray mould with fine veins, FGM forming, backing and demoulding, etc. At the same time, the metallography, porosity and microhardness of the spraying layer have been analyzed. The results show that the service performance of the FGM mould is much more excellent than that of the traditional mould, and the life span can also be greatly improved. The research will have a significant influence on the material development in the mould industry.

Relationship portfolios and capability development: Cases from the moulds industry

A number of authors within business marketing and purchasing, have stressed that the heterogeneity of relationships in customer and supplier portfolios are a source of managerial problems and opportunities. This paper looks at the use and development of firms’ capabilities in the context of relationship portfolios. Two case studies about producers of moulds are used to illustrate how their contrasting trajectories in terms of degree of specialisation can be related to the variety found and sought in their portfolios of relationships. Our study suggests that portfolio interdependencies are best understood in the context of the development of idiosyncratic capabilities, which include interpretations and experiences in using and influencing that variety.

Mould pressure control in rotational moulding

The technology of the rotational moulding of plastics has improved dramatically in recent years due to the recognition that measuring the temperature inside the mould is fundamental to process control. The next major advance will be made when the benefits of controlling the pressure inside the mould are fully utilized. A drawback of the rotational moulding process has always been the surface pinholes and internal bubbles that occur in the moulded part. These occur because, as the powder particles melt and coalesce, they trap pockets of air and it takes a considerable time for these to disappear. It is known that factors such as the viscosity of the polymer melt, the shape of the powder particles, the particle size and size distribution, the mould release agent and the metal used for the mould all affect the pinholing problem. However, the major factor that influences pinhole removal is mould pressure. If pressure is applied at a strategic point in the heating cycle, it can force trapped air out of the melted plastic. Indeed the use of mould pressurization can offer additional benefits such as cycle time reduction and significant improvements in the mechanical properties of the moulded part. However, few moulders make any attempt to monitor or control the mould pressure, mainly because its effect is not understood. This paper explains why mould pressure control throughout the moulding cycle is crucial to the rotational moulding industry in terms of, firstly, achieving good part quality and, secondly, reducing cycle times. It is also suggested that a fundamental change from passive venting to active venting of the mould is an important development that must occur in this industry.

A collaborative application portal for the mould industry

Large companies are conducting business with greater numbers of partners than ever before, and are looking for information and communication technology to better manage these relationships. Likewise, they expect partners, including their suppliers, to also quickly adopt appropriate technologies and business strategies. The mould industry is an important support industry during the product development process, serving as an important link between the product designer and manufacturer. This paper presents a collaborative application portal which provides an application platform for collaborative product design, product data management, manufacturing information management and e-business services for the mould industry. A J2EE-based architecture and some pivotal elements are used to construct this portal. Collaborative activities between mould companies and its customers, suppliers and partners are illustrated. A http://www.diemoldonline.net portal for the mould industry in Singapore as an application case is introduced.

Industrial Agglomerations as Localised Networks: The Case of the Portuguese Injection Mould Industry

A resurgence of interest in industrial agglomerations can be found among many different academic disciplines. This trend has been accompanied by a focus on how spatial proximity and the emergence of links between colocated actors may generate benefits for firms, namely, in the generation and diffusion of knowledge. By conceiving industrial agglomerations as territorially based networks, we argue that the dynamics in connections internal to those networks affect and are affected by local institutions as well as connections external to the territory. Our study of the injection mould industry cluster at Marinha Grande in Portugal suggests that firms profit from the emergence of relationships between colocated actors and other agglomeration benefits. However, we suggest that the potential of the industry to generate new knowledge appears to be founded on the patterns of interfirm connections, which selectively connect diverse capabilities both within and outside the agglomeration.

Knowledge renewal in industry, a question of relationship between product and process

In order to consolidate their competitive advantages, companies have adopted new organisational structures for design. However, these structures are often inadequate to the innovative process. The latter would be far better served by a knowledge development process revealing the importance of the relationship between product development and process manufacturing. In the particular case of the mould industry, process engineers, as intermediaries between product and tool, play a crucial role here. But, while they contribute to knowledge creation, they are not universally active in the entire knowledge renewal process. Case studies show some difficulties encountered by companies in integrating process knowledge in production. Two models emphasise the role of the combination of three resources – material, human and symbolic resources – in organisations to enhance the renewal of knowledge between product and process developments.

Domain-specific portal for the precision component and tooling industry in Singapore—needs analysis and a test-bed implementation

This paper presents the observations and implications of Internet-based collaborative design and manufacturing in Singapore for targeted domain-specific areas—more specifically, the die and mould industry. Based on a survey, the issues faced by local companies are summarized and possible solutions are proposed. To promote the use of Internet for collaborative design, manufacturing and business in the local manufacturing industry, a test-bed domain-specific portal has been developed to facilitate collaborations among companies with their customers, suppliers and partners. Various technologies for value-added collaboration services are investigated and developed. These aim to facilitate business collaboration, such as partner selection, order process collaboration and collaborative planning, as well as engineering collaboration, such as collaborative product and tooling design and rapid prototyping over the Internet. The architecture of the e-manufacturing portal is presented and the collaborative technologies are introduced.

Accurate Machining of Freeform Surfaces by Restraining Cutter Contouring Errors

Machined parts having sculptured surfaces pose challenges in the field of CAD/CAM. Sculptured surfaces are essential in the manufacture of components with curved geometry, which are demanded mostly in the aerospace and die and mould industries. This paper presents an adaptive cutter path restraining method for freeform surface machining and its implementation in milling. The ultimate goal is to achieve high contouring accuracy for sculptured parts machining which is a principal index for the performance evaluation of CNC machines. The proposed method is robust in achieving the desired surface cutting with the capability of satisfying pre-specified tolerance requirements using certain adaptive laws. The given tolerance is measured as the angular deviation by which the generated cutter path differs from the desired path. Since the feedrate is considered to be the most significant cutting parameter, only feedrate variations from 5 mm s-1 to 30 mm s -1 are applied in this system. The tool paths generated with and without the adaptive mechanism are compared. The proposed methodology has been tested on a CNC milling system with an open-architecture controller. The experimental results demonstrate that the proposed tolerance feedback mechanism is very effective for producing parts with sculptured surfaces.

Experimental research on the dynamic characteristics of the cutting temperature in the process of high-speed milling

The cutting temperature is a key factor which directly affects cutting tool wear, workpiece surface integrity and machining precision in the high speed machining (HSM) process. The purpose of this paper is to present an inverse heat-transfer model considering three-dimensional transient heat conduction to calculate the heat flux and the temperature distribution on the tool–workpiece interface in the high speed milling process. The model was set up by a finite element method based on Beck’s inverse heat-conduction theory and was verified by numerical simulations and a series of experiments which aimed to obtain the surface temperature data of a thin-walled workpiece with the aid of an infrared thermometer and the tool–workpiece interface temperature by an embedded artificial thermocouple. The dynamic characteristics of the cutting temperature in high-speed milling aluminum alloy were studied systematically. The numerical simulation results revealed that there was a close agreement between the calculated temperature value and the measured temperature value of the cutting interface in high-speed milling of aluminum alloy. The inverse heat-conduction method can be used to estimate the heat flux flowing into the workpiece and the temperature distribution on the tool–workpiece interface. Using the infrared thermometer as a remote sensor can solve the problem of measuring the temperature in high-speed milling and also it can be used as an approach to reveal the cutting mechanism of high-speed milling. There exists a critical cutting speed in the high-speed milling aluminum alloy. The value of this critical speed will be different for the different cutting conditions. Constant feed per tooth must be kept in high-speed milling to efficiently suppress excessive heat generation while obtaining a high material removal rate, especially for machining difficult to-cut materials with a thin-wall construction. The average tool–workpiece interface temperature is influenced by the thickness of the workpiece. The related temperature distributions will be very beneficial to the optimal construction design for the thin-wall parts used in the aeronautics and astronautics as well as die and mold industries.

Local Production Systems and Organizational Change: Hierarchization and Competing Firm Networks in Marinha Grande, Portugal

European local production systems have evolved and restructured in recent decades. One path of change has been an internal reorganization towards more hierarchization among local firms and the emergence of formal firm networks and an economic reconcentration. This article supports these observations and provides evidence from the mould industry in Marinha Grande, Portugal. The formal firm networks are, however, heterogeneous and they constitute new competitive strategies, that challenge the historical organization and institutions of the industrial districts and local production systems in which small was beautiful.

Rapid machining of hardened AISI H13 and D2 moulds, dies and press tools

Tools and dies for the forging, die casting and plastics moulding industries are commonly made from AISI H13, heat treated to 48–52 HRC, while the press tool sector predominantly uses AISI D2 at a significantly higher hardness of 60–62 HRC. Over the last 10 years, the introduction of high speed end milling has enabled the direct manufacture of prismatic components in the hardened state. The paper briefly outlines such techniques and details published machinability data. Following on from this, experimental work is presented on the drilling of hardened AISI H13 using carbide tooling, together with research on ancillary drilling and tapping operations on hardened AISI D2. When through drilling AISI H13, it was possible to produce up to 210 holes (16 mm deep), with a cutting speed of 30 m/min and a feed rate of 0.1 mm/rev. Drilling data are also presented on the use of water-based electrical discharge machining (EDM) dielectric fluids as a replacement for a conventional soluble oil cutting fluid to allow hybrid HSM/EDM on one machine tool. When drilling and tapping D2, tool life was low with six and nine holes, respectively. Finally, case study work is detailed, relating to the production of AISI D2 automotive press tool parts, in which traditional manufacture is compared with high speed machining (HSM) techniques, using both indexable and solid coated carbide cutting tools. When producing accurate radii on one component, the manufacturing time was cut by 75% using the HSM approach, despite the relatively poor tool life performance detailed above.

金型を取り巻く環境と金型材の動向

金型を取り巻く環境と金型材の動向

The application of U-shape milled grooves for cooling of injection moulds

In the injection moulding process, productivity and part quality depend largely on the cooling system of the injection mould. Several cooling methods are being adopted by the mould industry, with the straight-drilled cooling channels method being the most popular. Many reported research activities have been based on this method, but the method has several limitations that prevent it from achieving efficient and uniform cooling. In the present work, a U-shape milled groove method was proposed for large and complicated parts, especially for parts with large free-formed surfaces. Simulations were made to compare the cooling effect of U-shape milled grooves with that of straight cooling channels using COSMOS/DESIGNSTAR, an analysis software based on the finite element method (FEM). The heat flux was calculated on a cycle-averaged basis and the natural convection between ambient air and the exterior mould surface was ignored. A mouse cover was used as a case study. The U-shape milled grooves were found to have better temperature control than straight cooling channels. The temperature distributions of the core and cavity with U-shape milled grooves were more uniform than with straight cooling channels. Moreover, the U-shape milled grooves removed the heat efficiently; the mould temperature was lower than that with straight cooling channels. The U-shape milled grooves method has demonstrated its advantages in mould cooling. Although U-shape milled grooves need to be machined using computer numerical control (CNC) machines and more machining time is required, making them more expensive than straight cooling channels, their potential benefits will be explored for practical applications.

Six axis robots help plastics moulders meet intense competition

Recent trends in the plastic moulding industry that now mean it can be beneficial to apply six axis robots to tasks previously undertaken by simpler beam or Cartesian robots are described. The six axis robots are also able to undertake many additional assembly and finishing tasks that could not be attempted by simpler robots. Also described are “Soft Float” and collision detection features now available on six axis robots.

518 新型 5 軸加工機械の開発

There is a request for development of the multiple axis machines for machining of the slope surface, freedom curved surface from the Die & mold industry and the Aerospace industry. Especially, Die & Mold industry requires not only high speed finish machining but also heavy duty rough machining. So, we developed 5-axis machining center to be high rigidly which has swivel type head and rotary table. Specially, the turn mechanism of the spindle head uses ball screw drive on the A-axis head swivel. This mechanism is higher rigid than a rack-and-pinion drive, have a high accuracy and more resistant to wear. It is introduced about this new-model 5 axis machining center in this paper.

Investigation of chip formation in high speed end milling

Ball-nose end mill cutters are used extensively in the die and mold industry. However, very little work has been done in the research of chip formation in high speed ball-nose end milling. An experimental investigation has been conducted in this study to establish the chip formation mechanism. Common mold steel H13 hardened to HR c 55 is machined on a high speed machining center under dry conditions at a spindle speed range of 10–30k rpm. Four typical types of chip and three types of chatter have been encountered in this study. Images of the chips are obtained by the use of SEM. The EDX method is used to analyze the interaction between the cutting edge and the chip in the formation process. Based on the findings of this study, the chip formation mechanism has been proposed in this paper. The locus of cutter movement for the three types of chatter is illustrated to explain the relationship between the chip formation and the chatter behavior. A method to judge process stability by analysis of the chip has been suggested based on the findings of the experiment. It has also been established through this study that the classical “adiabatic shear” does not occur in chip formation in high speed ball-nose end milling.