design & molding - Changing Times for Mold Designers: Technology Leads the Way

By Scott Peters, Sales/Engineering Manager, ProMold, Inc.

I am uniquely positioned in our industry to comment on the ever-changing culture of the mold making industry. I began my career in this business as an apprentice mold maker/designer, and later as a manufacturing engineer. Today, I am a sales/engineering manager and have been fortunate to see first-hand the kinds of changes we are experiencing today.

For years, in some companies, mold designers were considered overpaid draftspeople. Many toolmakers and product engineers envisioned these individuals as a means to obtaining a functional injection mold. However, these overpaid draftspeople were only needed when it came time to determine parting lines and general mold construction methods. The actual completed design was left to the artisan toolmaker. The toolmaker alone understood the mold as no one else could, due to his/her experience and expertise. The toolmaker determined actions, fit, and function. The designer determined that there was adequate steel and specific, accurate gate locations, based primarily on trial and error, past experiences, and a product engineer's guidance. Today, however, mold designers are valuable participants in the design-to-manufacture process of bringing new products to market. They are relied upon for a greater amount of engineering information. Now, mold designers must be familiar with an ever widening variety of plastic resins, be more creative in determining moving actions within a mold, and have a working understanding of new and exotic mold materials.

In addition, mold designers need a working knowledge of, or an excellent resource base for, items such as shear characteristics, shrinkage rates (both in and across flow), chemical reactions with mold materials, and venting requirements. Just as important, mold designers need to understand processing parameters as well as other key issues, such as being familiar with higher operating temperatures associated with exotic molding resins. For example, some of the toughest new thermoplastic resins mimic thermosets in terms of dimensional stability at elevated temperatures.

These resins are injected at temperatures often double that of commodity-grade materials. The molds are usually cooled with hot water, live steam, or hot oil. In these cases, the designer not only has to account for thermal expansion of the mold itself but also provide adequate insulation to isolate the mold from the press. If too much heat is lost from the mold to the platen, the process can be hindered, and the product will be rejected.

Newer resins allow greater complexity in design

Along with the elevated temperatures, product engineers are discovering new ways to add complexity to the end product. Where it was once unusual for a product to require unscrewing actions or side cores, it is today becoming the norm. It is also becoming almost common for a product to require at least one action in a direction out of die draw. Today's designer must recognize these requirements and find a proper cost-effective solution. In addition, depending on the actual molder, tool builder, and the required action, a designer may need to propose several options during the preliminary design phase. Those options may range from a simple mechanical slide to a complex reciprocation unscrewing action. Whichever the case, it is the designer who must find a cost-competitive, durable answer to the actions required.

As a result of all these new requirements, many component manufacturers have begun standardizing items for use in a modular approach to mold building. In this case, the designer not only has the responsibility of designing the mold but also utilizing standardized parts. In Europe, for example, a designer may commit career suicide if asked to detail a part for manufacture that could be purchased commercially. In an industry where lead times are becoming shorter and shorter, the designer has a greater role in meeting the delivery schedule.

The electronic and print engineering libraries are becoming more valuable every day. During slack times, a wise designer spends time becoming familiar with the various manufacturers and components. Thanks to the Internet, information is available 24/7, and geographical and time zone barriers no longer exist. With the use of e-mail and catalog data, purchase orders and requests for quotation can be solicited anytime, in any time zone, and a confirmation will be waiting in the morning. This evolution has helped make the task of securing and reviewing catalog information all the more important.

In some instances, the designer must play the role of salesperson to introduce a new approach to building a mold or using a new standardized component in meeting the product design challenge. Whatever the task, a good designer derives a feeling of success when the mold is finally finished and parts are shot, especially when new technology has been introduced and implemented.

New mold materials require greater chemical awareness

With one eye on cycle reduction and the other on durability, today's designer practically needs a minor in chemical engineering. For example, designers need to understand the relationship of phosphates in a nickel bath to sulfurs in a rubber compound. In addition, they should understand the potential for galvanic corrosion between copper-based alloys and tool steels. What's more, in many cases, designers are expected to determine the proper type of steel for a given set of properties, know the best possible heat treatment conditions, and remember whether the material will expand, shrink, twist, or sag as a result of the heat treatment.

With the introduction of specialty metals — sintered and special grade types — designers must consider what is to be achieved by each selection that is made. Designers should ask, "Is this material being used because it's what we have always used, or is it being used because it is best suited for wear, hobbing, coining or galling?" Whatever the case, the designer is now situated at the front lines in metallurgy. I cannot over-emphasize the need to establish and maintain close relations with the metallurgical department at your steel supplier. These resources really know their business and can save a tool from certain disaster when they are involved early in a project that requires their expertise.

New software enhances design All of the changes occurring in the mold making industry have not happened in a vacuum. The computer industry has provided higher levels of sophistication in the hardware available. The new hardware runs more exotic software and provides more information to the designer. With all of this new technology, the design/build process is being compressed even more. Molds that took sixteen weeks a few years ago are now being completed in as few as eight weeks. As a result of this flurry of new technology, design engineers are in a constant state of learning. Just when we think we are program-proficient, the next version of the software release hits the street. In the 1970s, drafting machines with power-rise tables were the hot technology. In the 1980s, a new product called computer-aided design and drafting (CADD) was launched. The 1990s brought solid modeling and the integration of finite-element analysis (FEA) with CAD. The new millennium is focusing on a heightened awareness for the use of mold cool analysis and mold filling analysis. As these tools are refined, the designer of today and tomorrow must stretch his/her capabilities to meet the demands of our industry.

About the author

Scott Peters is the Sales/Engineering Manager for ProMold, Inc. (Cuyahoga Falls, OH). He has worked in the plastics industry as a mold designer and sales engineer for 25 years. For the past six years he has served on the Mold Making and Mold Design Division Board of Directors, Society of Plastics Engineers International. Contact him at slpeters@promoldinc.com, or visit www.promoldinc.com.