壳的一个主要特点是应该有其应用，如插入时要有一个低水平的内部压力。测试不同的温度很电流密度，所采取的措施取决于阴极弯曲张力计法。A钢测试控制使用侧固定和其他自由度固定（160毫米长，12.7毫米宽，0.3毫米厚）。金属沉积只有在控制了机械拉伸力（拉深或压应力），才能计算内部压力。弹性的角度来看，斯托尼模型应用，假定镍基质厚度，对部分钢材产生足够小（3微米）的影响。在所有测试情况下，一个能够接受的应用程序在内部压力在50兆帕的极端条件下和2兆帕的最佳条件下产生。得出的结论是，内部压力在不同的工作条件和参数没有明显的变化条件下。 7 校验注塑模具
试验已进行了各种代表性热塑性材料如聚丙烯、高密度聚乙烯和PC、 并进行了注射部件性能的分析，如尺寸，重量，阻力，刚度和柔性。对壳的力学性能进行了拉伸破坏性测试和分析。大约500个注射液在其余的条件下，进行了更多的检验
总体而言, 为分析一种材料，重要的是注意到行为标本中的核心和那些加工腔之间的差异。然而在分析光弹注入标本（图7）有人注意到不同的国家之间张力存在两种不同的类型的标本，是由于不同的模腔热传递和刚度。这种差异解释了柔性的变化更加突出的部分晶体材料，如聚乙烯和聚酰胺6.
有人注意到一个较低的柔性标本在的高密度聚乙烯分析测试管在镍核心的情况下，量化30%左右。如尼龙6这个值也接近50%。 8 结论
经过连续的测试，注塑模具在不同条件下检查的氨基磺酸镍液使用添加剂。这就是说塑性好，硬度好和摩擦力好的层状结构，已取得的力学性能是可以接受的。借鞋缺陷的镍壳将部分取代环氧树脂为核心的注塑模具，使注入的一系列中型塑料零部件达到可接受的质量的水平。
A technical note on the characterization of electroformed nickel shells for their application to injection molds
——aUniversidad de Las Palmas de Gran Canaria, Departamento de Ingenieria Mecanica, Spain
Abstract
The techniques of rapid prototyping and rapid tooling have been widely developed during the last years. In this article, electroforming as a procedure to make cores for plastics injection molds is analysed. Shells are obtained from models manufactured through rapid prototyping using the FDM system. The main objective is to analyze the mechanical features of electroformed nickel shells, studying different aspects related to their metallographic structure, hardness, internal stresses and possible failures, by relating these features to the parameters of production of the shells with an electroforming equipment. Finally a core was tested in an injection mold.
Keywords: Electroplating; Electroforming; Microstructure; Nickel
1. Introduction
One of the most important challenges with which modern industry comes across is to offer the consumer better products with outstanding variety and time variability (new designs). For this reason, modern industry must be more and more competitive and it has to produce with acceptable costs. There is no doubt that combining the time variable and the quality variable is not easy because they frequently condition one another; the
technological advances in the productive systems are going to permit that combination to be more efficient and feasible in a way that, for example, if it is observed the evolution of the systems and techniques of plastics injection, we arrive at the conclusion that, in fact, it takes less and less time to put a new product on the market and with higher levels of quality. The manufacturing technology of rapid tooling is, in this field, one of those technological advances that makes possible the improvements in the processes of designing and manufacturing injected parts. Rapid
tooling techniques are basically composed of a collection of procedures that are going to allow us to obtain a mold of plastic parts, in small or medium series, in a short period of time and with acceptable accuracy levels. Their application is not only included in the field of making plastic injected pieces [1], [2] and [3], however, it is true that it is where they have developed more and where they find the highest output. This paper is included within a wider research line where it attempts to study, define, analyze, test and propose, at an industrial level, the possibility of creating cores for injection molds starting from obtaining electroformed nickel shells, taking as an initial model a prototype made in a FDM rapid prototyping equipment.
It also would have to say beforehand that the electroforming technique is not something new because its applications in the industry are
countless [3], but this research work has tried to investigate to what extent and under which parameters the use of this technique in the production of rapid molds is technically feasible. All made in an accurate and systematized way of use and proposing a working method.
2. Manufacturing process of an injection mold
The core is formed by a thin nickel shell that is obtained through the electroforming process, and that is filled with an epoxic resin with metallic charge during the integration in the core plate [4] This mold (Fig. 1) permits the direct manufacturing by injection of a type a multiple use specimen, as they are defined by the UNE-EN ISO 3167 standard. The purpose of this specimen is to determine the mechanical properties of a collection of materials representative industry, injected in these tools and its coMParison with the properties obtained by conventional tools.
Fig. 1. Manufactured injection mold with electroformed core.
The stages to obtain a core [4], according to the methodology researched in this work, are the following:
(a) Design in CAD system of the desired object.
(b) Model manufacturing in a rapid prototyping equipment (FDM system). The material used will be an ABS plastic.
(c) Manufacturing of a nickel electroformed shell starting from the previous model that has been coated with a conductive paint beforehand (it must have electrical conductivity). (d) Removal of the shell from the model.
(e) Production of the core by filling the back of the shell with epoxy resin resistant to high temperatures and with the refrigerating ducts made with copper tubes.
The injection mold had two cavities, one of them was the electroformed core and the other was directly machined in the moving platen. Thus, it was obtained, with the same tool and in the same process conditions, to inject simultaneously two specimens in cavities manufactured with different technologies.
3. Obtaining an electroformed shell: the equipment
Electrodeposition [5] and [6] is an electrochemical process in which a chemical change has its origin within an electrolyte when passing an electric current through it. The electrolytic bath is formed by metal salts with two submerged electrodes, an anode (nickel) and a cathode (model), through which it is made to pass an intensity coming from a DC current. When the current flows through the circuit, the metal ions
present in the solution are transformed into atoms that are settled on the cathode creating a more or less uniform deposit layer.
The plating bath used in this work is formed by nickel sulfamate [7] and [8] at a concentration of 400 ml/l, nickel chloride (10 g/l), boric acid (50 g/l), Allbrite SLA (30 cc/l) and Allbrite 703 (2 cc/l). The selection of this composition is mainly due to the type of application we intend, that is to say, injection molds, even when the injection is made with fibreglass. Nickel sulfamate allows us to obtain an acceptable level of internal stresses in the shell (the tests gave results, for different process conditions, not superior to 50 MPa and for optimum conditions around 2 MPa). Nevertheless, such level of internal pressure is also a consequence of using as an additive Allbrite SLA, which is a stress reducer constituted by derivatives of toluenesulfonamide and by formaldehyde in aqueous solution. Such additive also favours the increase of the
resistance of the shell when permitting a smaller grain. Allbrite 703 is an aqueous solution of biodegradable surface-acting agents that has been utilized to reduce the risk of pitting. Nickel chloride, in spite of being harmful for the internal stresses, is added to enhance the conductivity of the solution and to favour the uniformity in the metallic distribution in the cathode. The boric acid acts as a pH buffer.
The equipment used to manufacture the nickel shells tested has been as follows:
? Polypropylene tank: 600 mm × 400 mm × 500 mm in size. ? Three teflon resistors, each one with 800 W. ? Mechanical stirring system of the cathode.
? System for recirculation and filtration of the bath formed by a pump and a polypropylene filter.
? Charging rectifier. Maximum intensity in continuous 50 A and continuous current voltage between 0 and 16 V.
? Titanium basket with nickel anodes (Inco S-Rounds Electrolytic Nickel) with a purity of 99%. ? Gases aspiration system.
Once the bath has been defined, the operative parameters that have been altered for testing different conditions of the process have been the
塑料模具毕业设计中英文对照资料外文翻译文献
