注塑成型优化方法（有出处）--中英文翻译

3.0 闻远设计 2023-08-11 31 4 126.5KB 12 页 20光币

侵权投诉

A technical note on the characterization of electroformed nickel

shells for their application to injection molds

——Universidad 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

Article Outline

1. Introduction

2. Manufacturing process of an injection mold

3. Obtaining an electroformed shell: the equipment

4. Obtained hardness

5. Metallographic structure

6. Internal stresses

7. Test of the injection mold

8. Conclusions

References

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.

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.

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.

文档加载中……请稍候！
如果长时间未打开，您也可以点击刷新试试。

下载文档到电脑，查找使用更方便

20 光币 4人已下载

立即下载

摘要：

Atechnicalnoteonthecharacterizationofelectroformednickelshellsfortheirapplicationtoinjectionmolds——UniversidaddeLasPalmasdeGranCanaria,DepartamentodeIngenieriaMecanica,SpainAbstractThetechniquesofrapidprototypingandrapidtoolinghavebeenwidelydevelopedduringthelastyears.Inthisarticle,electroformingasa...

展开>> 收起<<

注塑成型优化方法（有出处）--中英文翻译.doc

共12页,预览4页

还剩页未读，继续阅读

注塑成型优化方法（有出处）--中英文翻译

相关推荐

开通VIP享超值会员特权

作者详情

相关内容

推荐作者

热门标签

举报选择: