Strength Of Mold Research Articles

Experimental Study of Demolding Properties on Stereolithography Tooling

Direct tooling using stereolithography (SL) photopolymer has been developed as rapid tooling for short-run injection molds. However, the tool strength, thermal conductivity, and erosion resistance of SL mold are lower than that of the conventional metal mold. Previous study has showed that the tool life was limited under 200 shots and tool damage often occurs during part ejection. In this paper, experimental data from a demolding properties test are presented and discussed. The experiments were performed using various cooling time, hold pressure, and mold temperature. The experimental data were analyzed by measuring demolding force and surface roughness to evaluate tool life and failure mechanism in order to obtain a working range for the process parameters. The test result shows that the demolding force has close relation with cooling time and mold temperature.

Rubber isostatic pressing and cold isostatic pressing of metal powder

The effect of a rubber mold on densification behavior of aluminum alloy powder was investigated under cold isostatic compaction such as cold isostatic pressing (CIP) and rubber isostatic pressing (RIP). The effect of the thickness and strength of a rubber mould and friction between die wall and a rubber mold were studied. The hyperelastic constitutive model based on the Ogden strain energy potential was employed to analyze deformation of rubber. The elastoplastic constitutive model of Shima and Oyane and that of Lee and Kim were implemented into a finite element program (ABAQUS) to simulate densification of metal powder during CIP and RIP. Finite element results were compared with experimental data for densification and deformation of an aluminum alloy powder compact under isostatic compaction.

Experimental ammonia-free phosphate-bonded investments using Mg(H2PO4)2.

In previous study, we found that Mg(H2PO4)2 instead of NH4H2PO4 was available as a binder material for phosphate-bonded investments and possibly could be used to develop the phosphate-bonded investment without ammonia gas release. The purpose of the present study was to develop the experimental ammonia-free phosphate-bonded investments by investigating suitable refractories. Mg(H2PO4)2.nH2O and MgO were prepared as a binder. Cristobalite and quartz were selected as refractories. The power ratio of MgO/Mg(H2PO4)2.nH2O was set constant at 1.2 according to our previous findings. Fundamental properties of dental investment such as strength, manipulation and expansion were evaluated. Using cristobalite as the refractory material, further investigations were performed. The refractory/binder ratio was definitely effective. The increase of this ratio led to low mold strength and large mold expansion. The present findings suggested that C5 was desirable for dental investment.

Dimensional Changes of Cast Iron during Crystallisation at Different Mold Parameters

s Dimensional and volume changes of castings including inner shrinkage cavities during the solidification are affected by the metal properties and by the given mold as well. Earlier research in the field dealt with the effect of various properties of the solidified metal under equal test conditions The present research project aims to investigate the effect of different properties of the mold on the size accuracy and the compactibility of castings The results of tests confirm that the thermal expansion properties of sand, the resistance and strength of mold have important influence on dimensional changes at the beginning solidification of casting.

Modelling grain growth dependence on liquid content in liquid phase sintered materials : R.M.German, E.A.Olevsky. (Pennsylvania State University, USA.) Metall. Mater. Trans. A, vol 29A, no 12, 1998, 3057–3067

The effect of a rubber mold on densification behavior of aluminum alloy powder was investigated under cold isostatic compaction such as cold isostatic pressing (CIP) and rubber isostatic pressing (RIP). The effect of the thickness and strength of a rubber mould and friction between die wall and a rubber mold were studied. The hyperelastic constitutive model based on the Ogden strain energy potential was employed to analyze deformation of rubber. The elastoplastic constitutive model of Shima and Oyane and that of Lee and Kim were implemented into a finite element program (ABAQUS) to simulate densification of metal powder during CIP and RIP. Finite element results were compared with experimental data for densification and deformation of an aluminum alloy powder compact under isostatic compaction.

Effect of binder/filler ratio on hot strength and hot permeability of investment casting ceramic moulds

The hot strength and hot permeability of investment casting ceramic moulds are closely related to their service performance. The main purpose of this study was to investigate the effect of the binder/filler ratio of the back-up slurry on these properties. Back-up slurries consisting of zircon flour bonded with colloidal silica were used to construct the test specimens and the hot strength and hot permeability were evaluated by measuring the modulus of rupture and the absolute permeability, respectively. Additionally, ceramographic samples were extracted from the hot permeability specimens in order to correlate the results with microstructural features. It was shown that the hot strength reaches a maximum and that the hot permeability increases with increasing binder/filler ratio. The ceramographic observations indicated that these results are related to the presence of microcracks in the back-up coats of the mould.

The effect of potential investment expansion and hot strength on the fit of full-crown castings made with a gypsum-bonded investment

Objectives. It has been claimed that the strength of the investment mold at the casting temperature affects the dimensional accuracy of castings ( e.g., Markley, 1953; Earnshaw, 1957; Asgar, 1972), but the relationship has not been studied quantitatively. In this investigation, the effects of both mold expansion and hot strength on the relative inaccuracy of full-crown castings have been measured and analyzed. The likelihood that a strong investment could cause distortion of the casting by non-uniform restriction of casting shrinkage (Earnshaw, 1969b) was also considered. Methods. Castings were made with a commercial gypsum-bonded inlay investment, used both as supplied and with modifications that increased its expansion and reduced its hot strength. In both series of tests, the investments were used over a wide range of liquid/powder (L/P) ratios in casting rings fitted with dry ceramic liners, and set under dry conditions. Results. Casting inaccuracy showed a significant linear correlation with total expansion and a highly significant linear correlation with the combination of total expansion and hot strength. The modified investment, with its low hot strength, gave less distortion of casting shape than did the much stronger unmodified material. However, it was found that to ensure sound castings, the hot compressive strength should not be less than 1.8 MPa. Significance. This investigation showed that while investment expansion is the major variable affecting casting inaccuracy, hot strength is an important modifying factor which also has to be considered when predicting casting inaccuracy from measured properties of the investment.

特集 工具鋼 プラスチック金型材料選択エキスパートシステムにおける樹脂流動解析にもとづく金型の変形及び応力解析

We have been studying the strength of television cabinet mold by using results of injection molding analysis. In this case, we found that the stress applied to cavity widely ranged.The mold cracking is mainly caused by concentration of stress.Especially the corner of mold exhibits a so large stress, therefore we must design large corner-rounding according to mold materials.

Skin holes of titanium casting.

The present study describes refractories which contribute to formation of skin holes of Ti casting. Plates consisting of quartz (Qu) and cristobalite (Cr) powders and Qu- and Cr-MgO mixtures were fired at high temperatures and used as phosphate-free molds. The cross-section of the castings was investigated using an optical microscope and an electron probe microanalyzer. Whereas the castings into the Qu molds were almost complete, those into the Cr molds were incomplete. The surface reaction zone of the Qu molds formed a typical layered structure with fewer skin holes. That of the latter extended deeply into the interior with a net-shaped Ti-Si phase, cracks, and holes. Addition of MgO to Cr effectively improved the castability and changed the reaction zone to the typical layered structure. However, slender holes occurred along the mold wall. The overall area around the holes was contaminated by Si and Mg. Probably, this resulted from a reaction of forsterite with Ti. The reactivity difference between Qu and Cr was not related to the fired strength of mold.

Compressive Strength of Green Sand Mold Using Active Bentonite Separated by Elutriation

Compressive Strength of Green Sand Mold Using Active Bentonite Separated by Elutriation

Standardization of investment casting process using modified binder hydrolysis

A full factorial 23 matrix was designed to study the bending strength, permeability and hoop-stress of investment moulds. A novel method of ethyl-silicate hydrolysis; two-step hydrolysis, was used. The results indicate that the bending strength is directly proportional to the quantity of filler material in the slurry. Grain size of stucco material appears to exert the least effect on bending and hoop strength, whereas permeability increases slightly when coarser grain is used.

Relation between the Dehydration Process of Starch Mold and Mold Strength

Relation between the Dehydration Process of Starch Mold and Mold Strength

Materials of molds for electric discharge sintering of powder composites based on Cu-Sn, Cu-Zn

As a result of an analysis of the literature data it was established that the chief material used in non-Soviet practice for making dies and electrode punches of molds for EDS is graphite which, however, has a number of shortcomings; the principal ones among them -sticking of the product to the mold and low strength -complicate extraction of the products and have the effect that the molds are used practically only once.

Hot Compressive Strength and Deformation of Sand Mold

Hot Compressive Strength and Deformation of Sand Mold

Application of dispersed additives for increasing the strength of gypsum molds

An analysis of the patent and technical literature shows that directed change in the characteristics of the binding systems is one of the methods of improving the physicomechanical properties of the molds for the production of precision (thin) ceramic parts. Such a modification has the following aims: strengthening of the system, changing the duration of setting, increasing the porosity (water-absorption), decreasing the shrinkage, improving the wear resistance and life, etc. Water-soluble resins substituted by polyoxyethylene and polyoxyalkylene glycols, latex, derivatives of cellulose, etc. [i] are used for accomplishing the directed modification of gypsums.

The Strength of Self-Hardened Molds at Elevated Temperatures

The Strength of Self-Hardened Molds at Elevated Temperatures

Relations between Endothermic Curves in Differential Thermal Analysis of Bentonite and Mold Strength in High Pressure Molding

Relations between Endothermic Curves in Differential Thermal Analysis of Bentonite and Mold Strength in High Pressure Molding

Relations between Moisture Content at the Plastic Limit of Bentonite and Mold Strength in High Pressure Molding Process

Relations between Moisture Content at the Plastic Limit of Bentonite and Mold Strength in High Pressure Molding Process

Improvement of the Measurement of Retained Strength and a Study on the Retained Strength of Molds with Sodium Silicate-Bonded Sands

Improvement of the Measurement of Retained Strength and a Study on the Retained Strength of Molds with Sodium Silicate-Bonded Sands

Strength of ingot molds cast in molds of liquid self-hardening compounds

Strength of ingot molds cast in molds of liquid self-hardening compounds