• 소성∙가공
• /
• 제16권1호
• /
• pp.54-60
• /
• 2007

Optimum injection molding condition for a box mold was searched by the Response Surface Analysis(RSA) with the aid of process monitoring system(PMS). Process variables on the control panel of the injection molding machine such as barrel temperatures, screw speed profile, holding pressures, etc. cannot guarantee the uniformity of the material variables directly related with the state of the product in the mold cavity. In order to make sure the state of the resin in the cavity, pressures and temperatures in the cavity, runner and nozzle were monitored in the experiment with the PMS. To accomplish the consistency of the molding process, dependent variables such as the switchover point and holding time were searched with the PMS. With a proper objective function about deflection of the box-type product, the optimum injection molding condition was obtained.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2001년도 춘계학술대회 논문집
• /
• pp.32-36
• /
• 2001

Recently, reaction injection molding has been used broadly for rapid prototyping, because of its convenience and versatility. Since the properties of molded products are dependent on the process variables and the production is very short(less than 2minutes), the control of process variables is important. Generally, the two significant process variables are degree of cure and temperature of the reactants. In this paper, the relation between the degree of cure and the temperature of reactants was investigated to find the optimal curing condition of reaction injection molding for rapid prototyping. The degree of cure during reaction injection molding was measured by the Lacomtech sensor and dielectrometry equipment employing Wheatstone bridge type circuit.

• Design & Manufacturing
• /
• 제16권3호
• /
• pp.50-57
• /
• 2022

The qualities of the products produced by injection molding are strongly influenced by the process variables of the injection molding machine set by the engineer. It is very difficult to predict the qualities of the injection molded product considering the stochastic nature of the manufacturing process, since the processing conditions have a complex impact on the quality of the injection molded product. It is recognized that the artificial neural network(ANN) is capable of mapping the intricate relationship between the input and output variables very accurately, therefore, many studies are being conducted to predict the relationship between the results of the product and the process variables using ANN. However in the condition of a small number of data sets, the predicting performance and robustness of the ANN model could be reduced due to too many input variables. In the present study, the ANN model that predicts the length of the injection molded product for multiple combinations of process variables was developed. And the accuracy of each ANN model was compared for 8 process variables and 4 important process inputs that were determined by the feature selection. Based on the comparison, it was verified that the performance of the ANN model increased when only 4 important variables were applied.

• 소성∙가공
• /
• 제21권2호
• /
• pp.107-112
• /
• 2012

Gas-assisted injection molding(GAIM) produces parts with hollow internal sections. The technique offers benefits to powder injection molding(PIM), with lower material usage and reduced time for de-binding processes. In this study, the effects of processing parameters on gas penetration length of gas-assisted powder injection molding(GAPIM) were investigated for SUS316L stainless steel powder feedstock. Experiments were planned based on the Taguchi method, involving processing variables such as melt temperature, shot size, gas pressure, and gas delay time. The most significant parameters affecting gas penetration length were gas delay time and shot size, while the effects of melt temperature and gas pressure was relatively insignificant.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2002년도 금형가공 심포지엄
• /
• pp.253-259
• /
• 2002

Micro cell structures with high aspect ratio were fabricated by injection molding method. The mold inserts had dimension $1.9cm\times8.3cm$ composed of a lot of micro posts and were fabricated by LIGA process. The size of the micro posts was $157{\mu}m\times157{\mu}m\times500{\mu}m$ and the gaps between two adjacent posts were $50{\mu}m$. Using Polymethylmethacrylate (PMMA) injection molding was performed. The key experimental variables were temperature, pressure, and time. By controlling these, good shaped mim cell structures with $50{\mu}m$ in wall thickness and $500{\mu}m$ in depth were obtained. In order to understand micro molding mechanism, shape changes of molded PMMA were studied with experimental variables. And the durability of mold insert was investigated, too. The results show that the most important factor in molding processes was the mold temperature that is closely related to the filling of the melt into the micro cavity. And the holding time before cooling showed a great effect on the quality of molded PMMA.

• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집C
• /
• pp.621-626
• /
• 2001

Microcellular foaming process was developed at MIT in 1980's to save a quantity of raw materials and improve mechanical properties. There are many process variables in appling microcellular foaming process to the conventional injection molding process. Of all process variables, part dimension control and shrinkage are the most influential on the post molded dimension. The post molding dimensional change of thermoplastic resins is important to tool designers for predicting the specific difference of molded part vs. actual mold cavity. Generally, articles injection molded are smaller in size than the cavity; hence, the term shrinkage factor is used to define the allowance a designer specifies. It is important to consider the factors that influence molded part dimension. According to ASTM Designation: D 955, shrinkage from mold dimensions of molded plastics was measured. In injection molding, the difference between the dimensions of the mold and of the molded article produced therein from a given material may vary according to the design and operation of the mold. In this paper, shrinkage data of molded plastic parts was obtained. It can be an important information for designing optimum mold system in a microcellular foaming injection molding process.

• 한국정밀공학회지
• /
• 제22권3호
• /
• pp.68-77
• /
• 2005

The set-up of an injection molding process is a ye complicated and time-consuming job because it is required to well determine a lot of variables closely related to products. Thus, the productivity of the set-up process mainly depends on operators' expertise and know-how. To solve the problem mentioned before, this research constructs a support system which helps operators determining the condition of the injection molding easily and systematically. The construction of the support system consists of the following four steps: 1) to determine the control variables which affect the target defect types, 2) to design and implement UI(user interface) using a scenario of set-up process, 3) to design and implement the search algorithms for the initial and optima] condition, and 4) to construct the embedded system which integrates the support system with the operating system of a plastic injection molding machine. The test experiments of some typical products are performed using the embedded system to verify the validity of the support system.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
• /
• pp.469-470
• /
• 2006

The purpose of this research was to investigate and to find out the optimal annealing condition to mold an aspheric glass to be used for mobile phone module having 2 megapixel and $2.5{\times}$ zoom. Taking annealing rate and re-press temperature after molding as molding variables under the identical molding temperature and pressure, a glass lens was molded. And, Form Accuracy, Lens Thickness, Refractive Index, and Modulation Transfer Function(MTF) were measured in order to observe characteristics of molded lens, and then optimal annealing conditions were determined based on the resulting data. Properties of lens molded under the optimal conditions revealed Form Accuracy[PV] $0.2047\;{\mu}m$ in aspheric surface, and $0.2229\;{\mu}m$ in plane, and MTF value was 30.3 % under 80 lp/mm.

• 소성∙가공
• /
• 제11권7호
• /
• pp.581-588
• /
• 2002

Among the processes to produce micro lens, the process using press molding is a new technology to simplify the process, but it contains many unknown variables. The press-molding process proposed in this paper was simplified into two step process, the first step is the pressing to design the preform for glass element, the second step is the annealing to reduce the residual stress. It is important to estimate the amount of shrinkage of glass gob and the residual stress during process. It Is difficult to evaluate the process variables as mentioned above through the experiment. The influences due to process variables was evaluated by using FEM parametric analysis. The results in this paper can be applicable to produce micro lens.

• 대한기계학회논문집A
• /
• 제21권11호
• /
• pp.1773-1785
• /
• 1997

The cooling stage is the very critical and most time consuming stage of the injection molding process, thus it cleary affects both the productivity and the part quality. Even through there are several commercialized package programs available in the injection molding industry to analyze the cooling performance of the injection molding coling stage, optimization of the cooling system has npt yet been accomplished in the literature due to the difficulty in the sensitivity analysis. However, it would be greatly desirable for the mold cooling system designers to have a computer aided design system for the cooling stage. With this in mind, the present study has successfully developed an interated computer aided design system for the injection molding cooling system. The CAD system utilizes the sensitivity analysis via a Boundary Element Method, which we recently developed, and the well-known CONMIN alforuthm as an optimization technique to minimize a weighted combination (objective function) of the temperature non-uniformity over the part surface and the cooling time related to the productivity with side constranits for the design reality. In the proposed objective function , the weighting parameter between the temperature non-uniiformity abd the cooling time can be adjusted according to user's interest. In this cooling system optimization, various design variable are considered as follows : (i) (design variables related to processing conditions) inlet coolant bulk temperature and volumetric flow rate of each cooling channel, and (ii) (design variables related to mold cooling system design) radius and location of each cooling channel. For this optimum design problem, three different radius and location of each cooling channel. For this optimum design problem, three different strategies are suffested based upon the nature of design variables. Three sample problems were successfully solved to demonstrated the efficiency and the usefulness of the CAD system.