Rainer Dangel

Injection Molds for Beginners

2nd Edition

Hanser Publishers, Munich
Hanser Publications, Cincinnati

First of all I would like to thank my readers warmly. The success of this work has shown that its creation was a valuable exercise. The extensive feedback I received was consistently positive. The English edition, like the German edition, has been well received, and it has been a pleasure to see that it has been sold throughout the world, including in China and India, where it has been actively used in companies and training institutes. The popularity of the book is also the reason why the second edition is now available in full color.

Of course I was asked several times how a mold maker came up with the idea to write such a book. How does he find the time and where does the comprehensive knowledge come from?

The motivation to write a book can be manifold. My motivation was to write a small manual for the distribution of machining centers for mold making. The sales department should understand what mold making is, what it does, which components are to be manufactured, and from which materials the individual components are made. At first I wanted to use existing documents and publications. But I came to realize that there was nothing suitable at this level for beginners or newcomers. Then the only thing left was to create something of my own.

In order to make the book understandable for everyone, the idea came to me to always use the same plastic part as the basic concept. It should be as simple as possible and concentrate on the essentials. This gave me the possibility to build up the level of difficulty of the plastic part stepwise, and to explain the thereby-arising changes simply. That is to say, the central thread throughout the whole book should be uncomplicated and understandable. After publication in the processing machine company, the books were all gone after a few days. Not only the sales department, but also other interested parties tried to get hold of one.

So what could have been more obvious than to create a large work from this small book? Especially since, as already mentioned, there was nothing comparable on the market. At first, time constraints meant that the project ran more and more behind schedule. Then a long serious illness brought me the time, which I then used. Over 2500 hours of work and about 40 designs, or revisions of designs, had to be accomplished. Including all the corrections, this project took considerably more than half a year. The result is the present book, which after its success in both German and English versions, is now available in a second edition.

Over 40 active years in mold making, more than 23 years of which I worked as an independent entrepreneur and now as a project manager, consultant, and instructor have brought the necessary knowledge and experience. My training began in the summer of 1976. I passed through the entire technological change from milling machines with a handwheel, to NC technology, and then to today’s 5-axis simultaneous machining. The first designs were produced with India ink on a drawing board, moving on via a simple 2-D CAD program already in 1995 to full 3-D CAD.

The change over the decades was not only in the technology of the production of the injection molds, but also in the necessary shift from a handicraft business to an industrial company. Today the customers of the mold maker are almost exclusively industrial companies. Certifications, creation of processes, and Industry 4.0 are keywords that have occupied the mold making industry in recent years.

This is also the reason why a new section on process chains has been included in this second edition. In addition, it has been technically extended and small errors that unfortunately crept into the first version have now also been eliminated.

I hope you enjoy reading this book and look forward to your feedback.

Rainer Dangel, February 2020

German die and mold making is a brand with global significance. The reasons for this are diverse, but the industry’s secrets to success can certainly be attributed to smart design with a great deal of know-how, top performance production engineering and quality related criteria. One major aim of this book is to disseminate this philosophy to a wider, English-speaking readership.

Rapid implementation of innovations through close information exchange between all parties is planned for the future. Injection molds today already play a key role in modern production engineering in the manufacturing industry. Visions of the future such as the “smart factory” in the context of injection molding now offer the chance to raise the energy and resource efficiency of the production process to a new level with intelligent management and network flexibility. But the basis for this is a solid knowledge of the basics of engineering and manufacturing processes in mold making. The above-mentioned topics can only be implemented based on this knowledge and wealth of experience. And this is exactly where this technical book from Rainer Dangel comes in. What is required for bringing a product into shape?

In the book the author didactically as well as technically breaks new ground in the field of technical literature for injection mold making. In a very clear way, he combines theory with practice, always focusing on the following questions: “What is this product relevant for? What needs to be solved technically for which product specifications?” And, regarding the method of the manufacturing implementation: “How and with what can I fulfil the product requirement within the scope of the design and also the manufacturing process?” Through Mr. Dangel’s technical expertise which he established and developed over many years, it quickly becomes clear when studying the book that the practical implementation of the described has great significance. Basic knowledge and solutions are holistically considered. Advantages and disadvantages are presented and discussed. The wealth of 35 years of experience, beginning with training as a tool maker to the master craftsman’s diploma then to owning a private company flows through this technical book.

“Injection Molds for Beginners”, the title of this book, hits the bull’s eye and old hands who think it is no challenge to them might be taught a lesson!

Prof. Dr.-Ing. Thomas Seul

Vice rector for Research and Transfer at the Schmalkalden University of Applied Sciences and President of the Association of German Tool and Mold Makers (VDWF).

Rainer Dangel began his professional career in mold making with training as a mold maker from 1976 to 1980. As a young skilled worker, he already realized the possibilities of making a difference in this emerging technical profession. He laid the foundations for his career with the master craftsman’s diploma in mechanics at the age of 23.

He segued into self employment in 1987. He began with a small CNC milling shop for mold making components which within a few years developed into a modern, technically high-quality specialist company for manufacturing injection molds for various requirements. He had already introduced and was using the first 3-D CAD CAM system successfully in 1995.

All manufacturing options of modern mold making could now be offered. Rainer Dangel made it his duty to actively continue to develop and perfect the manufacturing processes. In 2006, the company built their own injection mold making shop in order to expand the process chain and be able to supply finished plastic components. Through the certification in accordance with DIN EN ISO 9001:2008 in 2008, his company was able to supply a variety of industries. Among other things plastic parts for the automotive industry could be VDA tested and approved (VDA = Association of German Automobile Manufacturers, see https://www.vda.de/en).

In the generally difficult economic year of 2010, the mold making company was closed. He was then for several years head of the technology center at the Heller brothers machining company in Nürtingen, Germany, where he was responsible for the support of the customers in the area of die and mold making.

Now back in the mold making arena, Rainer Dangel is currently active in two main areas as both consultant and instructor: Firstly, project management for injection molds, from part design via mold design all the way to start of production; he is also a machining specialist. The second area is the education and training of young people in this industry. He holds a lectureship at Reutlingen University, Germany, and supervises mechanical engineering students specializing in plastics technology.

I would like to express a heartfelt thank you to my colleagues at the Association of German Tool and Mold Makers (VDFW) for the support during the development of this book. Special thanks to Prof. Dr.-Ing. Thomas Seul, President of VDWF, for the foreword.

       Formenbau Schweiger GmbH & Co. KG, Uffing am Staffelsee, Germany, Anton Schweiger (Vice President)

       Formenbau Rapp GmbH, Löchgau, Germany, Markus Bay (Director of Training)

       VDWF, Schwendi, Germany, Ralf Dürrwächter (Managing Director)

       bkl-Lasertechnik, Rödental, Germany, Bernd Klötzer

       exeron GmbH, Oberndorf, Germany, Udo Baur

       Gebr. Heller Maschinenfabrik GmbH, Nürtingen, Germany, Marcus Kurringer, Jörg Bauknecht

       GF Machining Solutions GmbH, Schorndorf, Germany, Gabriele Urhahn

       Hans Knecht GmbH, Reutlingen, Germany, Hans Knecht

       Reichle GmbH, Gravier- und Laserschweißzentrum, Bissingen, Germany, Volker Reichle, Marco Reichle

       Werz Vakuum-Wärmebehandlung GmbH, Gammertingen-Harthausen, Germany, Henry Werz

       AS-Beratungen, Amtzell, Germany, Andreas Sutter

       3D Systems GmbH, Ettlingen, Germany (previously Cimatron GmbH)

       Meusburger Deutschland GmbH, Viernheim, Germany (previously PSG Plastic Service GmbH)

       Meusburger Georg GmbH & Co KG, Wolfurt, Austria

       MAKINO Europe GmbH, Kirchheim-Teck, Germany

The following are not association members, but were also on hand to help me. For this a heartfelt thank you to:

       Friedrich Heibel GmbH Formplast, Heuchlingen, Stefan Heibel

       Carl Hanser Publishers, Munich, Ulrike Wittmann, Jörg Strohbach

Finally, I would like to thank the Translation Management department at Meusburger Georg GmbH & Co. KG, Wolfurt, Austria, in particular Kristin Bylund Thurnher and Birgit Lins, for their expert translation of my German text into English. Achieving a high-quality translation of a specialist technical book is no trivial task, and for this the professional support of Meusburger is most warmly acknowledged.

In this book the planning, designing, and construction of injection molds is explained and described. It deals exclusively with injection molds for thermoplastics processing.

To simplify matters, the term “injection mold” is also referred to as mold, but has the same meaning. The term mold established itself in the specialist world and is predominantly used there. Note also that the spelling “mould” is used in British English, but again the meaning is the same.

Everything is explained and described concretely and understandably. A plastic container with a cover is the basis for almost all explanations. The drawings and designs of both of these plastic parts were especially made for this book. The dimensions of the designed molds and the technical details are real, so the injection molds can be actually built. On the basis of both or one of these parts, as much as possible is shown and explained.

There are sample calculations for the planning and dimensioning of injection molds. Different functions and elements relevant for the design are explained in detail. With the increasing demands on technology in the mold, the two parts become ever more complex so there is always a reference to the previous topics. If the part and/or the mold becomes more complex, the reason for it is therefore comprehensible.

There are further chapters in which the existing designs of actually manufactured injection molds are the basis for the explanations.

“Where do all these plastic parts actually come from? Who makes them and how are these plastic components even manufactured?” These are questions that hardly anyone asks. “What are those little curls on or in the plastic part, what are they for? Then there is a small spot that looks as if something was cut or torn.” These are all characteristics that are visible on each part and arise in the manufacturing of plastic parts. For this manufacturing technique, besides an injection molding machine and plastic granulates, an injection mold is needed.

Review your day and think about how many plastic parts you held in your hand, and then you can imagine that firstly there is an incredible number of injection molds and secondly the diversity of injection molds there must be in a variety of industries, applications, or life situations.

Or to put it in a different way, imagine yourself in the kitchen, bathroom, office, or sitting in the car. Now imagine all of the plastic parts gone. What remains? Not much is left that is not made of plastic.

In concrete terms: Let’s start early in the morning. Before even getting up you hit the alarm button. You already have had the first contact with a plastic part. It continues when you brush your teeth. Today’s toothbrushes are, although this is not easily recognizable, manufactured with very complex and complicated injection molds. The conventional toothbrushes with automatically inserted brushes are the simpler version. However, for manufacturing an electrical toothbrush, two different plastics are injected one after another in the injection mold in a very complicated procedure in order to make the rotating brushes in the small brush enclosure.

Hair dryers, coffee machines, tea kettles, refrigerators, stoves, and ovens are just a few consumer goods used in daily life. Opening the door of your car, you again have contact with plastic parts. Without injection molds, the interior of a car is unimaginable. Seats, steering wheel, switches, buttons, handles, levers, blinds, instruments, covering, trays and so on, a countless number of injection molds are used for the manufacturing of a vehicle.

Plastics surround us in the immediate vicinity of our workplace, whether it is in the workshop, in the office or in school. It doesn’t matter what you hold in your hand or use, again it’s plastic parts. A computer, a keyboard, whether it is on the machine or on the desk. Everywhere there are things made of plastic, in different colors, contours, shapes, and degrees of hardness—from hard and stable printer housings to the soft and flexible protective covers for the mobile phone.

Last but not least, a child’s room! Almost all children’s toy boxes are full of toys made from plastic: toy blocks, board game figurines, racetracks, puppets, game consoles, etc. Plastic parts, no matter what we do or where we are, accompany us the whole day. Plastic parts are everywhere, and without them a normal life would be inconceivable.

The list goes on and on. Everyone goes through their day, consciously or unconsciously in contact with plastic parts, but no one thinks about their origin, even though there is a huge worldwide industry behind them. Not only are there manufacturers of injection molds all over the world but also large corporations that manufacture the machines for the production of the plastic parts and very large chemical companies that constantly develop and produce new plastics for different applications. Millions of people are at home in this inconspicuous world.

Through the constant development of ever improving high-quality plastics the application possibilities continue to increase. Sheet metal parts made of steel or aluminum are gradually replaced by plastic parts. Brackets made of metal used for fixing cables, fuel lines, containers, or the like in a car’s engine compartment are replaced today by high-strength plastic parts.

Further evidence that this development will certainly continue is the progress in the production of bioplastics. To put it simply, for bioplastics, the petroleum used normally as raw material is replaced by biologically derived material. These oils are extracted from renewable raw materials and are also biodegradable. So far there have only been a few applications that were often only explored by scientific facilities. The whole thing is still in the stages of development. However, if only from the sustainability point of view, bioplastic is predicted to have a bright and important future.

The most significant advantage of plastic parts is that after manufacturing or the injection process a ready-to-use piece comes out of the injection molding machine. The manufacturing time for such a component is only a few seconds. This also has an impact on the much lower cost per piece. But now we come back to the contents of this book—the success of this whole process depends on a high-quality injection mold.