外文翻译--注射成型模具温度调节系统的设计和优化

外文翻译--注射成型模具温度调节系统的设计和优化内容摘要：

d costs are strongly linked. The longer is the time to produce parts the more are the costs. A reduction in the time spent on cooling the part before its is ejected would drastically increase the production rate, hence reduce costs. It is therefore important to understand and thereby optimise the heat transfer processes within a typical moulding process efficiently. Historically, this has been achieved by creating several straight holes inside the mould (core and cavity) and forcing a cooler liquid to circulate and conduct the excess heat away so the part can be easily ejected. The methods used for producing these holes rely on the conventional machining process such as this simple technology can only create straight holes and so the main problem is the incapability of producing plicated contourlike channels or anything vaguely in 3D space. An alternative method that provides a cooling system that „conforms‟ to the shape of the part in the core, cavity or both has been proposed. This method utilises a contourlike channel, constructed as close as possible to the surface of themould to increase the heat absorption away from the molten plastic. This ensures that the part is cooled uniformly as well as more efficiently. The first part of this investigation concentrates on reviewing and evaluating the injection moulding process, to set the knowledge and background on the subject. Then a study of proposed methods for developing and applying conformal channels is conducted, identify the most viable method. Specific softwarewas used to optimise the design and construction of the mould, with attention on refining the tool design through application of finite element and thermal flow , a study on the effectiveness of the conformal cooling channel based on virtual models was performed using IDEASTM software for prototyping and simulation. The study is on going and hopefully would culminate in the suggestion of the level of proficiency required using virtual models in deciding moulding specifications for production parts. 2. Brief overview of the injection moulding process The injection moulding industry, like all industries, at present needs to reduce costs to remain petitive. This need has been addressed using various technologies ranging from design software to puter numerical control machinery. After these technologies are in place and moulding begins the cost is usually based on cycle time. Adjustments can be made to the moulding machine to help reduce the time to mould but in the final analysis the time is dictated by the ability of the mould to carry the heat away from the molten polymer. Liquid is passed through cooling channels in the mould at the required temperature. This must allow the molten polymer to flow into all sections of the cavity while at the same time remove the heat as quickly as possible. Up to nowthese channels have been produced by drilling which can only produce straight lines. If the channels carrying the water could be conformed to the shape of the part and their crosssection changed to increase the heat conducting area then a more efficient means of heat removal could be realised. This may also help to reduce warpage when the part is ejected, as the plastic would be cooled more uniformly. . Temperature control Temperatures such as those for the molten polymer, the mould, the surround temperature and the clamping system temperature need to be controlled (Fig. 1). When molten plastic is injected in the mould it must be solidified to form the object. The mould temperature is regulated by circulation of a liquid cooler, usually water or oil that flows inside channels inside the mould parts. When the part is sufficiently cooled it can be ejected. Most (95%) of the shrinkage happens in the mould and it is pensated by the ining material。 the remainder of the shrinkage takes place sometime following the production of the part [1]. . Pressure control Both the injection unit and the clamping system require npressure with the latter developed to resist the former (Fig. 2). Three different pressures can be distinguished in the injection unit: initial, hold and back. All these are obtained by the action of a screw. In the clamping unit the oil pump of the hydraulic system controls the pressure needed to move the mould. Holding pressure is required to finish the filling operation and maintained during solidification to supply the shrinkage. . Time control Time is the most significant parameter in the entire operation. Cost and machine efficiency can be estimated from the cycle time. The principle temporal aspects to be controlled include: gatetogate time, injection time and cooling time. A simple schematic illustration of a typical cycle time is shown in Fig. 3. . Thermal proprieties Despite their large diffusion, for all plastic materials temperature range is a limit to their purpose. Both high and low temperature can create damage to plastic ponents. It is important to study thermal proprieties to understand and predict this behaviour. Therefore cooling times in moulding machines must be set carefully to permit, first, plasticization of the thickness and secondly dissipation of melting heat. Unlike metals, the thermal capacity of plastics is high with crystalline plastics having a higher capacity than noncrystalline. Plastics have a large coefficient of thermal expansion if pared, for example, with metals. A way to modify these values is to use mineral fillers such as fibre glass. . Cooling channels As with most manufacturing fields, production time and costs (lead and lag) are strongly correlated. The longer it takes to produce parts the more are the costs, and with injection moulding production industries cooling time is often taken as the indicator of cycle time. Improving cooling systems will。