Robust Process Development and Scientific Molding

Frontmatter

1. Introduction to Scientific Processing

Abstract

Injection molding and extrusion are the most common techniques employed in the manufacture of plastic products. Injection molding of plastics began as an idea by the Hyatt brothers for the manufacture of billiard balls. The idea was borrowed based on a patent by John Smith to inject metal castings.

Suhas Kulkarni

2. Properties of Polymers and Plastics That Influence Injection Molding

Abstract

The term plastic is most commonly used when referring to injection molding materials. Plastics are a class of long-chain molecules called polymers. When polymers have certain properties they are called plastics. Since most of the commercially molded polymers fall under the classifications of plastics, we shall refer to these materials as plastics in this book.

Suhas Kulkarni

3. Polymer Rheology

Abstract

Polymer rheology is the science of flow of polymers. The study of polymer flow is essential to understand the melt processing of plastics. In any melt processing technique, the plastic has to be melted and then deformed to conform to the final product specifications. In injection molding, the melt must be injected into a mold and then cooled to get the final part.

Suhas Kulkarni

4. Plastic Drying

Abstract

Most plastics tend to absorb moisture when exposed to humidity. This is true with plastic in any form, whether in pellet form before processing or in a finished product, such as an injection molded product. Such plastics are called hygroscopic or hydrophilic plastics. Plastics that do not absorb moisture are called hydrophobic plastics. Nylons are common examples of hygroscopic plastics.

Suhas Kulkarni

5. Common Plastic Materials and Additives

Abstract

Injection molding processors are mainly concerned with the way the plastic flows and with the temperature at which the plastic can be processed. Flow characteristics of all plastics are very similar. They all follow non-Newtonian behavior and therefore exhibit shear thinning effects.

Suhas Kulkarni

6. Injection Molding and Molding Machines

Abstract

The concept of injection molding for plastics was adopted from the metal die cast industry, which began to develop in the early to mid-1800s. Plastics were not known for their useful properties at this time. All polymers were naturally occurring materials and did not have much industrial value. In 1869, John Hyatt developed a concept to make billiard balls from cellulose nitrate, also known as celluloid.

Suhas Kulkarni

7. Scientific Processing, Scientific Molding, and Molding Parameters

Abstract

Several parameters determine a successful molding process. There are various speeds, pressures, times, and temperatures to be considered. Scientific processing encompasses an understanding of the underlying scientific principles of each parameter and the application of these principles to achieve a robust process and consistency in part quality. Scientific processing covers the complete molding process, from the time the plastic enters the facility to when it leaves as a finished product.

Suhas Kulkarni

8. Process Development Part 1: the 6-Step Study – Exploring the Cosmetic Process

Abstract

Developing a robust molding process is often not done by following a systematic procedure. While decreasing ‘art to part’ times with decreasing resources, it is often difficult to follow the procedures. However, these shortcuts decrease the part quality, increase scrap rates, increase workloads of personnel, and reduce the overall efficiencies of the molding process.

Suhas Kulkarni

9. Process Development Part 2: Exploring the Dimensional Process via the DOE

Abstract

Chapter 8 introduced the first stage of the process development process where the boundaries of the process were explored based on the cosmetics of the part. No dimensions were considered. The bigger the cosmetic process window, the higher the chances of a final robust process with dimensional consideration. The first stage is the basis for the second stage of process development, because if the parts are not cosmetically acceptable, the dimensions would not matter.

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10. Mold Qualification Flowchart, Production Release, and Troubleshooting

Abstract

This chapter will discuss a flowchart that includes all necessary measurements and the documentation that must be carried out for successful release of a molding process into production. The tools required for mold qualifications and troubleshooting are also mentioned. Development of troubleshooting guides is a continuous process, and they need to be revised and updated during production runs.

Suhas Kulkarni

11. Role of Mold Cooling, Venting, and Regrind in Process Development

Abstract

The mold is basically a heat transfer unit. The hot plastic melt is injected into the cold mold cavity where it is cooled down until it is ejected out of the mold. The mold is kept at a lower temperature compared to the melt, which is sufficient to bring the melt down to the ejection temperature of the plastic. The temperature of the mold is very important because it controls the rate of heat transfer.

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12. Related Technologies and Topics

Abstract

This chapter will introduce a variety of technologies and techniques that can be applied to enhance the robustness of a process and/or to speed up the complete project from conceptualizing the part to its release as a molded product. Cavity pressure technology, which takes process monitoring and control to a completely new level, increasing product quality and plant efficiency many fold, will be introduced.

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13. Quality Concepts

Abstract

This chapter is included to give the reader some basic knowledge and understanding of some of the terminology used in injection molding. At the end of the chapter, a list of some suggested texts is mentioned for readers who would like to further their knowledge.

Suhas Kulkarni

Backmatter