The Key to Up-Front Mold Design

By involving the tool designer, builder and molder early in product development, you can reduce turnaround time by weeks or even months, shave weeks off the mold construction cycle and reduce costs by eliminating potential product design troubles.


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The most time-consuming and costly phase of plastic part production is the mold design and build process. What magnifies this is that when the mold designer gets started is usually when the part to be tooled is discovered not to be moldable. Challenging and expensive mechanisms are needed in order to produce and release the part out of the tool.

Some remedies include making use of the tool design phase to finalize the part design; handing off a portion of the part design to a toolmaker; as part of the program, having tooling engineers on staff who understand how molds work and know how to design them; and, operating product and mold design development concurrently.

Handy Tools

Until recently, CAD software's function in the product design process was well identified, but its purpose for mold design was unclear. In the past, most molds were designed by drafting them in 2-D and dimensioning the different details of the mold on blueprints. This information was used exclusively for the tool manufacture, and had very little or no impact upon the part designed.

Today, the use of software for mold design is experiencing a remarkable evolution. There are a variety of essential mold design tools available within your current product design software.

With the new generation of 3-D solid modeling software, there are highly developed tools that speed up the mold design process, but also examine the part's geometry, simulate analysis and forecast potential tooling problems.

Draft analysis, thickness examination, undercut detection, geometry check, parting line recognition, etc., is some of the information you can obtain with the most recent software capabilities. Moreover, with 3-D, advanced tool problems such as sink marks, knit lines and other cosmetic defects can be predicted before any steel gets manufactured. However, the dilemma is that product designers are not acquainted with how to use these capabilities because they are specialized for use by tooling and injection molding engineers.

Tooling Background Dilemma

Many manufacturing companies have incredibly talented product designers on staff driven by great marketing imagination. They can design wonderfully shaped and sculptured parts with ingenious functions and mechanisms, but also create challenging—and sometimes almost absurd—tooling issues that greatly impact time and cost because these designers lack a tooling background.

A mold designer has the skills not only to engineer tooling, but also to examine the piece parts and forecast potential problems with a part design, often with the same 3-D solid modeling software. It is a great policy to invite a mold designer to review meetings and let him learn valuable information about the product while in concept design stages rather than when the product is finalized and expected to be tooled—where no time is projected for revisions or modifications due to stringent delivery times.

Traditional Versus Modern

Traditional Product-to-Market Approach
Injection molds are time-consuming to build because typically mold buyers supply the work in a vertical mode—product designer, mold designer, moldmaker and molder. The traditional product-to-market approach (see Figure 1) exercises a serialized arranged method. Mold design is not started until the product is on its final approved design, tools are quoted and awarded, purchase orders issued, and a mold builder and mold designer are scheduled. Not only does this add extra weeks to the project, it places the mold builder in a decisive vertical path that can compromise the success of the program.

By the time a product is launched for mold drawing, there is no time available for redesigning a part that could have been fixed earlier if problems were known. Sometimes not even small modifications that could radically improve quality, cost and speed up tool building are permitted because of time constraints.

Not only does the tool builder have a promised and strongly enforced delivery date, other mating parts of the same program are dispersed to similar tool shops that are currently working on them. A redesign is not only time consuming, but also very costly—when considering repair work on all the related parts. The traditional product-to-market approach creates long leadtimes.

Modern Product-to-Market Approach
The modern product-to-market approach (see Figure 2) is an engineering-based progression in which the product designer and mold designer can design concurrently after initial product conceptions. What is practical today is to involve a mold designer after the preliminary concepts of the part are brainstormed—maybe rapid prototypes made—and a rough outline is completed of how the part is going to look, feel and function—basically to educate the design intent.

The mold designer can examine the part prototypes and suggest a few areas of concern to be modified, and discuss any draft issues as well as thick and thin areas. He can start laying out the tool for preliminary sizes and determine a rough parting line, while the part designed is being matured. Once the part gets to its final tweaks, the mold designer can review the tool design and quickly issue steel orders to the builder, so he can start squaring up the different blocks for the tool. After final part is issued, the mold designer can finalize the tool details, while the tool builder can start extracting electrodes and creating CNC toolpaths. This approach can save an enormous amount of time.

The Keys to Modern Product Design

Product and mold designers can work through most of the manufacturing issues in advance by teaming up in the early stages of product development as one engineered process. A team of engineers with diverse backgrounds concurrently working together is far more capable, intelligent and talented than any individual will ever be. Part design shouldn't be a millstone of the product designer, but the shared production of the entire team that has contributed to its achievement. Being powered by a creative product development team streamlined with robust manufacturing engineering muscle is a tremendous competitive advantage nobody can afford to overlook.

Open communication between the design parties is crucial to keeping the tool design and build on schedule. Increasing emphasis on concurrent part and tool design makes the associability with the part model data more significant than ever for faster reaction in the event of design changes.
In the result of a drastic modification to the part, the mold designer should be informed immediately so he can evaluate the revision of the tool build. Communication, interaction, participation and involvement are widespread key words in today's mold manufacturing environment.

There also is a cost/time matter to consider (see Figure 3). In the event of an engineering change to a particular product due to poor quality, cost or performance, you'd rather find out sooner than later. The cost to repair a potential problem is multiplied by several times the further it is discovered down the product development cycle. A problem discovered while designing the part or mold is far more economical to repair than if the glitch is revealed after the molds are built, the parts are molded, and the products are assembled, packaged and sitting on the store's shelf. A $500 part design change can proliferate to be a $50,000 change—if it needs to be addressed after parts are put on the market.

Overlapped Engineering Tasks
Although high-tech solutions—such as high-speed machining and automation—can accelerate certain portions of the mold build process, there is a great opportunity to overlap product and mold design for timesavings (see Figure 4). In order to manage this concurrent activity you must select your mold designer first while designing the product. The mold designer not only will help in anticipating potential molding problems, he also can accelerate your process by starting the preliminary mold design while the part design is being completed—running them parallel. Furthermore, by using the same 3-D design software for product and tool design, rapid engineering response is guaranteed due to the data legacy and associability of the software. Having a product and tool designer using the same CAD system is strongly recommended.


The main advantage of having your tool designer involved earlier is the ability to influence the product and processes being developed. This approach results in added value to your services and creates strong ties with your customer as he becomes more reliant on you to oversee his design process. You can integrate with your customer by catering strong manufacturing skills, value-added services and the ability to anticipate his manufacturing needs.

Another great advantage of this concurrency is cross training. As the tool designer learns and understands the use and function of the product developed, the part designer gains the knowledge of tooling concerns and how to correct them. This knowledge gain also is useful for future projects.

One last gain is that the mold designer can anticipate potential changes and possible future modifications to the part. When he designs the mold with this in mind, he can keep the tool compatible and avoid expensive repairs in the future. Staying clear from certain areas with components or cooling lines, anticipating future mold inserts, implementing steel safe conditions, or merely protecting certain parts of the mold that might get revised is a tremendous time and cost saving not only at tool build, but also for future modifications.

A disadvantage of no communication between designers is a good share of lost time. If the product designer doesn't communicate the part changes quickly enough, the mold designer will waste valuable time designing a tool with an outdated part.

Another drawback is in the event of extreme part changes in shape and form with dramatic changes in the parting line. A large amount of mold design work can be trashed if the part undergoes extraordinary modifications. Closer communication and compromise between product designer and mold designer is the answer to time-to-market improvements.

A Break for Mold Designers

Mold design is a highly demanding profession and a vital function of product development success. The mold engineering practice cannot be expected to be any faster without giving up something. No matter what kind of software or computer you may use, you just can't think faster. This doesn't mean that mold designers should have an unlimited amount of time to perform the job, but at least enough to have an opportunity to study and analyze the part to be molded. The more they know about the part functions and design intent, the more they can spot potential problems down the road. The sooner a mold designer gets involved, the more time that is still on hand to concentrate on potential glitches, and reduce the chances of becoming a victim of designs that are not molder friendly.

Up-front mold design allows the engineering team to explore all feasible alternatives early in the process and reduce costly changes later. It prevents the tool builder from wasting a lot of effort having to rework tooling and avoid producing an unacceptable or expensive part. The way to design molds today is not just taking the final product design data sent from the customer, construct parting line surfaces and enclose them with a mold base. You should discuss any improvements or potential issues with the customer. Communicating slight changes in the part design will lead to considerable time and cost savings.

If you want to shrink leadtimes, reduce manufacturing costs and create a competitive edge, get a competent mold designer by your side before the product design gets developed. You can have a high rate of return for a relatively small time investment. With an open mind, forward-preventive thinking and a unified vision you too can save time, money and design for manufacture.