I read and reviewed the second edition of Menges and Mohren's How To Make Injection Molds a couple of years ago and considered it the most comprehensive mold engineering book I had ever seen. This third edition has been updated and expanded, and a great deal of new material has been added, making it thoroughly impressive and even more comprehensive than its predecessor. 

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The book's target audience is people in the injection molding, mold making, and mold design fields, with a primary emphasis on those who design molds. The presentation focuses more on engineering than technology, with 214 formulas available to calculate nearly anything you might need to know in order to design or build an injection mold. 

In addition, the book includes 608figures and 62 tables of information to illustrate, expand, and organize the material in such a way that it is accessible and ready to use. The extensive bibliographies at the end of each chapter still reference primarily German works but with a few more English titles than the prior edition. The 11-page table of contents and 12-page index lead you readily to whatever topic for which you may be searching. 

This is the kind of book that contains so much information that any attempt at a synopsis fails to do it justice—but I'll try. There are descriptions, explanations, examples, and mathematical relationships for quoting molds and for designing mold bases, hot and cold runner systems, gates, vents, cooling systems, cavities and cores, ejection devices, side-action and unscrewing components, and more. The reader is shown how to calculate forces and pressures in the various systems of a mold, as well as different methods of designing molds and components that best withstand these conditions. 

I have used and compared the results of many of the equations in this book to actual conditions and found them to be a good indicator of actual conditions. For example, I selected the extensive section on calculating the force required to eject plastic parts from a mold. 

The most challenging part of this was estimating what the plastic's properties would be at the time of ejection. (Material properties are not included in this text; I found them in one of the more widely used plastics encyclopedias.) Using an educated guess of the temperature at ejection and the corresponding tensile strength of the plastic at that point, I calculated that it would require 6.7 tons to eject a 72-cavity mold for a certain part with a substantial undercut. 

When our customer ran the mold, a press with 6.5 tons of ejector force would not strip the parts. When the mold was moved to a press with 9 tons of ejector force, the parts were ejected. Obviously, this is not a replacement for finite-element analysis or a more thorough knowledge of the behavior of plastics, but for obtaining a quick, good working idea of the forces required, the result was impressive. 

Following are highlights of selected chapters, beginning with Chapter 1, Materials for Injection Molds. This chapter contains a wealth of information not only on metals and their application, but also on surface treatments. The treatments covered include tried-and-true materials like the families of chrome, nickel, and other types of plating, and some of the newer chemical and physical vapor deposition (CVD and PVD) methods and laser treatments. 

Chapter 2, Mold Making Techniques, has been updated with a thorough discussion of the direct and indirect methods of rapid tooling available today. Traditional and nontraditional machining methods are covered well, and the text on dies for the fusible core technique covers the process in detail. 

Chapter 6, Design of Gates, also delves into hot runners. The hot runner section has been updated with pictures and descriptions of hot sprues, single face and stack manifolds, and a new section on some of the different methods employed in two-shot and multimaterial molding. Insulated runner design is still discussed in detail. 

As one might imagine, Chapter 8, Heat Exchange System, can be either a number cruncher paradise or the math phobic's nightmare. Even if your idea of fun isn't partial differential equations, a great deal of useful, readable information is presented in this chapter. The many drawings emphasize the descriptions of proper cooling channel geometry for different types of parts. The considerations involved in designing the heating systems for molding high-temperature and reactive materials are also covered. 

Chapter 14 presents many examples of the application of various types of computer-aided engineering and design software with rendered images from some of the major players in those fields and guidelines for choosing a CAD program. 

After a review of the second edition of this book was published, I received an e-mail from a gentleman in Italy who was looking for books and information on mold maintenance—and I could recommend this book as an excellent source. From scheduling and data evaluation to repair and storage and care, all aspects of mold maintenance are described fully in Chapter 15. 

Chapter 18 treats the subjects of temperature controllers and different types of sensors available for use with molds. Chapter 20, Special Processes­Special Molds, looks at the molding of micro structures, silicon technology, the LiGA Technique, inmold decoration, liquid silicone molding, and injection-compression molding. 

How To Make Injection Molds is such an excellent reference for mold designers and engineers that I personally consider it a must read/must have. The serious molder or moldmaker who wants a better understanding of any part of the art and science of mold building will want to read this book and have it as source of reference. In summary, How To Make Injection Molds, 3rd edition, is an excellent addition to the library of anyone seriously interested in mold design and moldmaking.—Reviewed by: Rocky Huber, senior engineer, Ivanhoe Tool & Die Co. Inc., Thompson, CT, rhuber@ivanhoetool.com .

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