Service Life Of Molds Research Articles

Development of a Rapid Tool for Metal Injection Molding Using Aluminum-Filled Epoxy Resins.

Metal injection molding (MIM) is a near net-shape manufacturing process combining conventional plastic injection molding and powder metallurgy. Two kinds of injections molds for MIM were developed using conventional mold steel and aluminum (Al)-filled epoxy resins in this study. The characteristics of the mold made by rapid tooling technology (RTT) were evaluated and compared with that of the fabricated conventional machining method through the MIM process. It was found that the service life of the injection mold fabricated by Al-filled epoxy resin is about 1300 molding cycles with the average surface roughness of 158 nm. The mold service life of the injection mold fabricated by Al-filled epoxy resin is about 1.3% that of the conventional mold steel. The reduction in manufacturing cost of an injection mold made by Al-filled epoxy resin is about 30.4% compared with that of the fabricated conventional mold steel. The saving in manufacturing time of an injection mold made by RTT is about 30.3% compared with that of the fabricated conventional machining method.

Industrial‐scale vacuum casting with silicone molds: A review

AbstractVacuum casting (VC) of reactive polymer resins in silicone molds is one of the oldest rapid tooling methods. It is widely used in the industry for prototype and small‐series production of thermoset plastic parts. Despite its widespread use, its scientific exploration is still scarce compared to other prototyping methods, such as three‐dimensional (3D) printing. Compared to conventional 3D printing methods, a wide range of excellent material properties can be achieved, making it well suited for the production of functional prototypes and even final products. The properties of the thermosets are comparable to those of injection molding in terms of viable shapes, mold fidelity, and material properties. However, due to the high cycle time and limited service life of the molds, VC is rarely utilized for mid‐ or large‐series production. Here, we provide a comprehensive overview of the state of the art and recent advances in the field. The review also provides a detailed technical introduction to the mold production, the process flow, and the materials used. A particular focus is on the key challenges facing industrial‐scale VC today—how to reduce cycle time, and how to increase mold service life?

Advances in polishing of optical freeform surfaces: A review

Abstract Ultra-precision polishing is one of the main machining processes for components with high surface finish requirements, such as optical molds. Typical optical mold materials include mold steel, silicon carbide and tungsten carbide, which have many excellent properties like strong corrosion resistance, low thermal expansion coefficient, strong oxidation resistance, low density, and high hardness. To ensure that the replicated parts meet high precision form and finish specifications, the molds made in hard and brittle materials must be machined to obtain a high-quality part surface. Therefore, polishing has evolved into ultra-precision polishing, which has a critical impact on the mold service life as well as the precision optical component quality. This paper presents the basic concepts and classification of ultra-precision polishing, introduces typical polishing processes, discusses polishing mechanisms and characteristics, and finally indicates the directions for future development of ultra-precision polishing processes.

Numerical simulation of wear-resistant surface design under high speed milling conditions

The effect of different surface texture micro-elements on the service life of molds in hardened steel molds has been systematically explored by establishing a four-right-angle bending simulation model. The temperature field, wear depth, load distribution, stress and strain distribution and other surface conditions were analyzed and studied, and then identified the poor service conditions in the region. According to the calculation of actual bending force, the accuracy of simulated load loading is verified. By changing the values of line spacing and feed, the corresponding texture elements are established on the die, and the numerical simulation of the texture elements under the interaction of the line spacing and feed is conducted. The influence of surface texture elements on the working condition of the die is studied. The milling parameters which are most beneficial to reduce the wear and improve the serviceability of the mold are selected, which provides a theoretical basis for the design of the wear-resistant surface under the conditions of high-speed milling.

Tribological and Wear Performance of Nanocomposite PVD Hard Coatings Deposited on Aluminum Die Casting Tool.

In the aluminum die casting process, erosion, corrosion, soldering, and die sticking have a significant influence on tool life and product quality. A number of coatings such as TiN, CrN, and (Cr,Al)N deposited by physical vapor deposition (PVD) have been employed to act as protective coatings due to their high hardness and chemical stability. In this study, the wear performance of two nanocomposite AlTiN and AlCrN coatings with different structures were evaluated. These coatings were deposited on aluminum die casting mold tool substrates (AISI H13 hot work steel) by PVD using pulsed cathodic arc evaporation, equipped with three lateral arc-rotating cathodes (LARC) and one central rotating cathode (CERC). The research was performed in two stages: in the first stage, the outlined coatings were characterized regarding their chemical composition, morphology, and structure using glow discharge optical emission spectroscopy (GDOES), scanning electron microscopy (SEM), and X-ray diffraction (XRD), respectively. Surface morphology and mechanical properties were evaluated by atomic force microscopy (AFM) and nanoindentation. The coating adhesion was studied using Mersedes test and scratch testing. During the second stage, industrial tests were carried out for coated die casting molds. In parallel, tribological tests were also performed in order to determine if a correlation between laboratory and industrial tests can be drawn. All of the results were compared with a benchmark monolayer AlCrN coating. The data obtained show that the best performance was achieved for the AlCrN/Si3N4 nanocomposite coating that displays an optimum combination of hardness, adhesion, soldering behavior, oxidation resistance, and stress state. These characteristics are essential for improving the die mold service life. Therefore, this coating emerges as a novelty to be used to protect aluminum die casting molds.

Application of a New Type of Lubricant in Warm Forming

Lubrication of warm forming moulds is of great significance for improving the product quality, reducing the deformation force, and prolonging the service life of moulds. In this paper, the film-forming property, anti-friction stick resistance, corrosion resistance and clean ability of several types of liquid lubricant were studied, a new type of flameless water-based graphite lubricant was prepared, and its high-temperature lubricating performance was researched. The test results show that the lubricant has better lubricating property, and is easy to use and free of pollution as a new type of water-based lubricant.

Parameter optimization of cooling system in U-shape hot stamping mold for high strength steel sheet based on MOPSO

This work aims to simultaneously optimize the cooling efficiency, cooling uniformity, and mold service life of the cooling system in U-shape hot stamping mold. And three indicators of the average temperature (Tave) of the hot stamping mold surface, the standard deviation of the temperature (σT) of mold surface, and the maximum equivalent stress (\( {\overline{\sigma}}_{\max } \)) of mold were adopted to represent the cooling efficiency, cooling uniformity, and mold service life, respectively. Such three indicators are greatly influenced and even can be adjusted by the mold structure parameters, such as the diameter of cooling channels (D), the number of cooling channels, the center distance of adjacent cooling channels (L), and the distance from the center of cooling channel to the mold surface (H). Based on the Box-Behnken design method and finite element simulation results simulated by the MSC. Marc software, the mold structure parameters D, L, and H were selected as the three independent variables, and the three response surface models of Tave, σT, and \( {\overline{\sigma}}_{\max } \) were, respectively, established. The applicability and reliability of the response surface models were checked by analysis of variance. And then the mold structure parameters (D, L, and H) were optimized by a multi-objective particle swarm optimization to simultaneously minimize the indicators of Tave, σT, and \( {\overline{\sigma}}_{\max } \). After optimization, the instantaneous cooling rates of steel sheet are higher than the critical cooling rate of martensite transformation before MS, which indicate that full martensite can be obtained in the steel sheet. The temperature uniformity of mold surface was improved, and a smaller \( {\overline{\sigma}}_{\max } \) of mold was obtained. Finally, a series of hot stamping experiments according to the optimizing scheme were conducted by a four-column hydraulic press. The experimental results verified the evolution of the mold temperature field simulated by finite element software and the reliability of the improved U-shape hot stamping mold.

CREATING A DIFFUSION LAYER ON THE NARROW SIDES OF THE MOLD OF CONTINUOUS CASTING MACHINE USING ALUMINUM THERMAL SPRAY COATINGS

To increase the service life of molds of CCM, there were created diffusion layers on their worked narrow sides of copper M1 and copper alloy MN2.5KoKrKh by sputtering of aluminum layer about 1.5 mm with subsequent diffusion annealing at T = 800 °C during 10 hours in an oxidizing atmosphere. It was found that on the copper surface of M1 it was observed hardening diffusion layer with thickness up to 1.5 mm, and of alloy MN2.5KoKrKh – 0.6 to 1.4 mm, that can be explained by the deterrence of diffusion process of contained alloying elements at subsequent thermal treatment. As the main indicators of the health of the diffusion layer authors used its thickness and microhardness. Du ring the analysis of the coated samples the feasibility of the application working on the narrow wall of the mold with aluminum thermal spray coating was established, followed by heat treatment in a protective atmosphere adjusted modes. The authors tested the mold of continuous casting machine with the assessment of the condition of the walls in the process of operation and changes in the quality of cast metal.

Effect of Thinning Additives in Ceramic Slips on the Corrosion of Gypsum Molds

The effect of different thinning agents on the corrosion of gypsum molds is investigated. It is shown that a more than two-fold reduction of the surface corrosion of samples is possible when using phosphate thinners. This will increase the service life of molds and make ceramic manufacture economically more efficient.

Grinding Affect the Service Life of Mould Research

In the process of modern mould manufacturing, grinding work still account for 25% ~ 45% of the total manufacturing time mould. Mould manufacturing quality of the finished product is closely related to the precision of mould manufacturing, particularly with the mould cavity surface accuracy and surface roughness has a close relationship. In the manufacturing of mould to make grinding micro cracks and residual stress is reduced to a minimum, full attention, grinding process in order to improve the service life of mould. So research to improve grinding processing quality, improve the service life of the mold, to extend the time of service, has the positive significance

Improvement of water slot design for beam blank casting mould

Two-dimensional thermo–elastic–plastic creep finite element models of two beam blank moulds with different water slot designs, the large hole mould and the small hole mould, are set up and their thermomechanical behaviour is numerically investigated by means of ABAQUS software. The temperature, distortion, stress and inelastic strain range across the hot faces as well as the fatigue life of the two moulds are discussed in detail, based on which it is shown that the distributions of temperature and distortion of the small hole mould are more uniform than those of the large hole mould, and the peak temperature of the former mould is smaller than that of the later mould. However, the fatigue life of the small hole mould is shorter than that of the large hole mould. Both moulds were put into service in an industry and it is demonstrated that the quality of the product cast by the small hole mould is better than that by the large hole mould, and the service life of the small hole mould is longer than that of the large hole mould because the service life of a mould chiefly depends on the wear of its hot face, which is much shorter than the fatigue life. An improved water slot design for the beam blank mould is then proposed and it is numerically demonstrated that this improved mould is superior to the large hole mould and the small hole mould.

Thermal Factors of Die Casting and Their Impact on the Service Life of Moulds and the Quality of Castings

Thermal Factors of Die Casting and Their Impact on the Service Life of Moulds and the Quality of Castings

Thermal Factors of Die Casting and Their Impact on the Service Life of Moulds and the Quality of Castings

This article deals with the analysis of the temperature factors of die casting and the conditions of the service life of moulds. It also describes a mechanism of the origin of internal structures and development of crystallisation grains of aluminium castings depending on the degree of undercooling. The monitored factors are very important in terms of production efficiency and the quality of the casting, which is positively reflected in the most important economic indicators of the production. In die casting, the melted metal is pressed under high temperature into a mould cavity of significantly lower temperature. The mould is then exposed to thermal strain of individual surface layers of the mould material. The speed of cooling of the castings in the metal mould increases, causing an increase of thermal gradients in the casting. Intensive heat exchange between the casting and the metal mould has a negative effect on fluidity, which increases the danger of incomplete replenishment and the occurrence of cold joints.

Study on the design of precious metal based protective films for glass moulding process

Driven by the huge market demand, the glass lenses made of various optical glasses are required to be more diversified in sizes/shapes, to have better form accuracy/surface roughness, to be more environmental durable, and to be more competitive in price. Glass moulding process (GMP) is regarded as a very promising technique for mass producing high precision optical components such as spherical/aspheric glass lenses and free-form optics. However, only a handful of materials can sustain the chemical reaction, mechanical stress and temperature involved in the glass moulding process. Besides, almost all of these mould materials are classified as hard-to-machine materials. This makes the machining of these materials to sub-micrometre form accuracy and nanometre surface finish a rather tough and expensive task. As a result, making service life of mould longer has played a critical part in the GMP industry. The interfacial chemical reaction between optical glass and mould is normally the main reason for pre-matured mould failure. This research aimed to investigate the interfacial chemical reaction between various optical glasses and different precious metal based anti-stick coating designs. The results showed that mould material, coating design, glass composition, moulding temperature and moulding duration could all have profound effects on the interfacial chemical reaction. Based on the results, a design developed specially for certain glasses is more likely to be the viable way of optimizing the effect of the protective coating.

Simulation and Experimental Analysis of Moulding Processes of Glass Diffractive Optical Elements

Driven by the huge market demand, the glass lenses made of various optical glasses are required to be more diversified in sizes/shapes, to have better form accuracy/ surface roughness, to be more environmental durable, and to be more competitive in price. In comparison to conventional refractive lens, diffractive lens (diffractive optical element, DOE) has the advantages of being thinner and lighter, and is widely used in optical systems such as lighting and photovoltaic systems. Glass moulding process(GMP) is regarded as a very promising technique for mass producing high precision optical components such as spherical/ aspheric glass lenses and free-form optics. However, only a handful of materials can sustain the chemical reaction, mechanical stress and temperature involved in the glass moulding process. Besides, almost all of these mould materials are classified as hard-to-machine materials. This makes the machining of these materials to sub-micrometer form accuracy and nanometer surface finish a rather tough and expensive task. As a result, making service life of mould longer has played a critical part in the GMP industry. The excessive stress and/or temperature involved in the moulding process are amongst the main reasons for pre-matured mould failure. This research aimed to analyze the stress/strain conditions and the obtained dimensional accuracy under various molding parameters by simulations. Molding experiments were subsequently carried out to verify the simulated results. A glass DOE of 14.8 mm in diameter and 3.36 mm in thickness are successfully produced in this research and the difference between the simulated and the molded DOE is around 15μm.

The Application Study of the Diamond Punching Method in Stamping Production of the Screen Hole Parts

In allusion to the problems such as the poor flatness of the parts , not-easy-guaranteed aperture precision, low strength and short service life of mould that occur in stamping production of the screen hole parts, this article detailed introduced the diamond punching method and at the same time it summarized the maintenance of the mould that this method uses

Applications on Nanocomposite Coating Technology in Plastic Injection Mould Cavity Surface Treatment

Nano surface engineering is a protection technology using nanometer material and nanometer technology, pointing at failure forms, characteristics and mechanism, comprehensively using a variety of traditional surface engineering technology. Nanocomposite coating technology which develops on the basis of the traditional composite coating technology was briefly introduced in the article. The research of application nanocomposite coating technology in plastic injection mould cavity surface treatment has just started. The nanocomposite coating technology was compared with the ordinary nickel electro-brush coating and the basic approach which realizes nanometer on the mould cavity was described. The advantages of nanocomposite coating were comprehensively and effectively explained. It can increase the coating thickness and hardness, improve the abrasive resistance, fatigue resistance and corrosion resistance of the plastic injection mould cavity, thereby enhancing the service life of mould.

Laser Local Stripe Bionic Strengthening of Mould Surface

In order to solve the problems of the waste of resources, and reduce the cost directly caused by the short life of the hot die in enterprises, this paper analyzes the wear of hot die which is one of the main factors affecting service life, and a thought that enhanced mold through laser surface local stripe grid bionic process is pointed out. Different from traditional laser hardening technology, the service life of mold processed by bionic laser melting enhancement simulating butterfly wings is nearly doubled. Experimental results provide a new way to improve die life, and the application of laser local stripe grid bionic process will bring enterprises significant economic benefits for its extension in mould industry.

Study of Properties of Ni-Base Nano-ZrO<sub>2</sub> Composite Plating Coatings

The surface of copper plate of the mold need to be reinforced to obtain the plating coatings with high hardness and corrosion resistant properties. Nowadays, Ni-base alloy coatings is used widely in the industrial production. In order to raise the service life of mold, the experiments on the property of Ni-base nano ZrO2 composite plating coatings was done in this paper. The experiments were planned with the orthogonal test design method. The effective factors on the property of coatings, bath temperature, cathode current density, the distance between two electrodes and the magnitude of Nano-ZrO2,were experimentally studied. The optimum process parameter were obtained. The results show that the composite plating layer of Ni-base Nano ZrO2 with good properties can be obtained.The optimal conditions are as follows: the bath temperature is 40 °C, cathode current density is 3A/dm2, the distance between two electrodes is 12 cm, the magnitude of Nano-ZrO2 is 12g/L. In addition binding strength of the coatings were measured quantitatively, and the structure of the plating layer were observed with SEM. The layer with good properties can be obtained in this method.

Investigation on RE Ion Nitro-Carbonizing Technology Used for 4Cr5MoSiVl Casting Mold

. In order to improve the high temperature stability of casting mold, we carried out the RE Ion nitro-carbonizing technology test on the 4Cr5MoSiVl steel. This test was done by using high-power pulsed supply for the 4Cr5MoSiVl steel casting mold surface treatment under different temperatures, time period, atmospheric pressure, and RE contents. The optimization of these parameters makes the layer structure dense, toughness increased, specifically the surface hardness, wear resistance, high temperature oxidation resistance, and thermal fatigue properties of the treated layer significantly improved. A test with the use of this technology has been done for the 4Cr5MoSiVl steel automotive lamp aluminum casting mold. The mold service life of each mold time increased from 30,000 to 100,000. The experimental results show that by using 4%RE 520oC×2h, and 1.05KPa atmospheric pressure, the treated layer has optimal qualities, which can meet the requirements in practice.