• Design & Manufacturing
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• v.6 no.1
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• pp.5-11
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• 2012

The sink mark on boss parts is generated by the volumetric shrinkage that is caused by both the molding thickness and the boss wall thickness. The volumetric shrinkage is caused by packing pressure and its amount tends to decrease by increasing the packing pressure. The packing pressure can therefore increase the flow rate to a boss part and causes the depth of sink mark to increase. As the molding thickness and the boss wall thickness in the boss part can increase the part volume, these may yield bad solidifying and also extend the molding cycle. In this paper, both the injection molding test and the flow analysis were carried out to investigate the effect of sink mark that was generated in the boss wall thickness of injection molded products. The sink mark could also be caused by thickness ratio of boss part. For a given thickness ratio of boss, several molding process parameters such as packing pressure, packing time and melt temperature, affecting to generation of the sink mark were discussed.

• 한국금형공학회:학술대회논문집
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• 2008.06a
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• pp.103-109
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• 2008

The sink mark on boss parts is generated by the volumetric shrinkage that is caused by both the molding thickness and the boss wall thickness. The volumetric shrinkage is caused by packing pressure and its amount tends to decrease by increasing the packing pressure. The packing pressure can therefore increase the flow rate to a boss part and causes the depth of sink mark to increase. As the molding thickness and the boss wall thickness in the boss part can increase the part volume, these may yield bad solidifying and also extend the molding cycle. In this paper, both the injection molding test and the flow analysis were carried out to investigate the effect of sink mark that was generated in the boss wall thickness of injection molded products. The sink mark could also be caused by thickness ratio of boss part. For a given thickness ratio of boss, several molding process parameters such as packing pressure, packing time and melt temperature, affecting to generation of the sink mark were discussed

• Transactions of Materials Processing
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• v.14 no.3 s.75
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• pp.233-238
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• 2005

Blow molding is divided into three categories, injection stretch blow molding, injection blow molding, and extrusion or direct blow molding. Extrusion blow molding has been studied experimentally to characterize the blowing behavior of parison. Blow conditions such as blowing temperature and cooling time were the experimental variables in this blowing experiment. Wall thickness of the lower part of blow molded sample was thicker than that of the upper part because of the sagging of parison during extrusion process. As temperature increases the wall thickness and the weight of blow molded sample decreased. No thickness variations in the blowing sample were observed according to the cooling time. The lower part of the sample showed high degree of crystallinity compare with the upper part of the sample. Thus the lower part of the sample was strong mechanically and structurally. It was recognized that the uniform wall thickness could not be obtained by only controlling the operational conditions. Parison variator should be introduced to get uniform wall thickness of parison and subsequently produce uniform wall thickness of blow molded product.

• Design & Manufacturing
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• v.14 no.3
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• pp.37-43
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• 2020

Progressive drawing processing is one of the manufacturing processes used to mass-produce a variety of products on the industrial site. In this study, the goal is to achieve a uniform product thickness of at least 1.3mm by reducing the wall thickness of the coupler parts used in automotive air conditioning systems to within 15% using A5052-H32 materials. The progressive die was designed using Blank's law of volume invariance. Due to the characteristics of the drawing process, the material thickness in the punch R part decreases and the thickness in the die R part increases. When designing the progressive die of the coupler part, an ironing method, a push back method, and a stand-alone die pad method were applied to each process to design a mold in consideration of the drawing rate and to artificially adjust the thickness change. The suitability of the method used in die design was investigated by measuring the thickness change of forming parts for each process. In the final part, it was confirmed that the thickness measurement values of the five regions of a radial line were implemented as 1.34-1.36 mm.

• Journal of the Korean Institute of Gas
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• v.18 no.6
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• pp.27-31
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• 2014

This paper presents a study on the strength safety of the weak parts at Part 1, Part 2 and Part 3 in the valve structure for LPG cylinder by using the finite element method. The maximum Von Mises stress of 27.5MPa was occurred at the corner edge of a valve Part 1 for the valve thickness of 1.5mm and LPG pressure of 3.5MPa. And the maximum Von Mises stresses for the valve thickness of 1.5mm and LPG pressure of 3.5MPa were 41.5MPa at Part 2 and 46.5MPa at Part 3. The FEM computed results show that the maximum Von Mises stresses at Part 1, Part 2 and Part 3 are very low value of 9.2~15.5% compared with the yield strength of a copper alloy, C3604. This means that the valve thickness for LPG cylinder is so over designed for the conventional valve. Thus, this paper recommends that the thickness at Part 1 and Part 2 is reduced for a light weight of a copper valve. But, the thickness at Part 3 may be better for a thick valve as a conventional valve for high torque strength.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.4
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• pp.163-173
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• 1996

Stereolithography is a process used to rapidly produce polymer components directly form a computer representation of the part. There are several considerations to be made for the efficient use of the process. Especially, the build-up orientation of part critically affects the part accuracy, total build time and the volume of support structures. The purpose of tis study is to determine the optimal build-up part orientation for the SLA process with improving part accuracy, and minimizing total build time and the volume of support structures. The forst factor is related to the area of surfaces whioch have staircase protrusions after solidification, the second factor is related to the total number of layers, and the third factor is related to the area of the surfaces which need to be supported with support structures. An algorithm is developed to calculate the staircase area, quantifying the process errors by the volume of materials supposed to be removed or added to the part, and the optimal layer thickness for the SLA system which can handle the variable layer thickness. So the optima l part orientation is determined based on the user's selections of primary criter- ion and the optimal thickness of layers is calculated at any part orientations.

• Solar Energy
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• v.4 no.2
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• pp.13-28
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• 1984

Direct Absorption Receiver and Thermal Storage System is a complex problem. This paper describes only characteristic of fluid flow on the receiver. The fluid thicknesses of Molten Salts (Melting Point : $397^{\circ}C$) flowing on the receiver of modified protopype ($10m{\times}10m$) were calculated theorectically, changing the receiver slope from 60 degree to 85 degree (5 steps). The receiver temperatures were $430^{\circ}C$ at the top part and $950^{\circ}C$ at the low part. The flow thickness of the Molten Salts at the top part of the receiver are around 1.9mm in the case of maximum insolution ($50{\times}10^6$juoule/sec; 58.898kg/sec of flow rate) and 2.0mm at the low part. In the case of 3/10 of maximum insolation (flow rate = 17.669kg/sec) the flow thickness at the top part are around 0.9mm and 0.4mm at the low part, and in the case of 1/10 of maximum insolation (flow rate = 5.889 kg/see) the flow thickness at the top part are around 0.6mm and 0.3mm at the low part. From experimental measurements of a normal fresh water thickness flowing on the model plate ($12.7cm{\times}111.76cm$), around 0.8mm at the top part of the plate and around 0.7mm at the low part were obtained in the case of maximum insolation (flow rate = 0.12496 kg/see). In the case of 3/10 (flow rate = 0.03748 kg/see) and 1/10 (flow rate = 0.012496 kg/see) of maximum insolation, around 0.5mm and 0.4mm at the top part, and around 0.3mm and 0.2mm at the low part were obtained respectively. The reason why the thickness of the Molten Salts increase at the low part of the receiver only in case of maximum insolation is that decreasing rate of the viscosity of the Molten Salts is larger than decreasing rate of the density of the Molten Salts during temperature increase from the top to the low receiver plate and decrease of the fluid velocity in accordance with continuity principle. In all cases without the above maximum insolation, the thickness of the Molten Salts and the fresh water decreased at the low part of the plate because of gravity force effects rather than friction effects and of continuity principle. All simillar flow patterns were obtained through all cases of the insolation making an exception of only maximum insolation.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.11 s.176
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• pp.210-217
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• 2005

A curl distortion induced by shrinkage during stereolithography polymerization process is analyzed with the classical lamination theory. Test parts of different layer thickness and part thickness are manufactured and their deformations are measured with CMM. Curl distortion is generated by the differential shrinkage of the layers, where the total shrinkage includes the shrinkages due to solidification and the change of temperature. It is shown that the curl distortion increases exponentially with decreasing the total thickness of the part, whose smaller layer thickness induces larger curl distortion. It is verified that only a part of the total shrinkage plays a role in generating the curl distortion.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.04a
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• pp.552-558
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• 1995

Stereolithography is a process used to rapidly produce polymer components directly from a computer-representation of the part. There are several considerations to be made for the efficient use of te process. Especially, the build-up orientation of part critically affect to the part accuracy, total build time and the volume of support structures. Te purpose of this study is to determine the optimal build-up part orientation for the SLA process with improving part accuracy, minimizing total build time, and the volume of supprot structures. The first factor is related to the area of surfaces which have staircase protrusions after solidification, the second factor is related to the total number of layers, and the third factor is related to the area of the surfaces which need to be supported with support structures. An algorithm is developed to calculate the staircase area with quantifying the process planning errors that the volume of materials is supposed to be removed or added to the part, and the optimal layer thickness for the SLA system whichcan hadle the variable layer thickness in different orientations achieved by rotating the given part to the specified finite directions. So the optimal part orientation is determined based on the user's selections of primary criterion and the optimal thickness of layers is calculated at any part orientations.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.9 no.4
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• pp.435-445
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• 1997

It was studied the phenomena of transient freezing of an inclined water-saturated enclosure. One side of the test section was cooled and the other sides were insulated. The effects of the initial temperature, the inclination angle on the temperature field and the shape of the ice-water interface were observed. In the beginning of freezing, with increasing the inclination angle the freezing rate was increased and in the stable density layer centered $4^{\circ}C$, the freezing was fast as the convective fluid flow became small. When the initial temperature was above the $4^{\circ}C$, the frozen thickness in the upper part of inclined surface was thinner than that in the lower part, but with time the frozen thickness of upper part was thicker than that of lower part, below the $4^{\circ}C$, the frozen thickness in the upper part was thicker than that of lower part from the begining, and above the $8^{\circ}C$ in the beginning upper part was thinner with concave, but with time thicker the upper part, vanishing concave.