Mold Design

For beginners, the only requirement is a little knowledge of mechanical drawing delineation, done either electronically via a computer (with programs like Autocad) or manually with a pencil on a drawing board.

In addition to basic calculus, the designer must know some trigonometry and arithmetic; both are required to spell out the dimensions on the mold parts to allow them to be machined. E-drafting has several advantages, including the following:

• It is possible to use the designs of earlier built molds without redrawing them entirely by copying or modifying some design features from the program’s memory, as opposed to having to redraw them from scratch.
• The development of a library of standard mold components and hardware that can be accessed and reproduced easily and on a large scale without the need to redraw them whenever they are needed can be made possible.
• Computer-generated prints do not require the skilled hand of the designer to produce quality prints.
• Computers allow you to easily transfer designs to other locations, such as manufacturing centers within your company or manufacturers in other locations.

Note that a computer is merely a tool for the designer; at the end of the day, a designer’s ability depends entirely on his or her understanding of what is required and what can be accomplished. You should also keep in mind that even the most experienced designer cannot always produce the most effective design on the first attempt. Instead, he will test various options throughout the design process. Sometimes, this requires sketching, erasing, and redrawing part or all of the picture, which can be done much more easily using an electronic device. In olden times, designers would make their drawings on paper without much concern for the appearance of the resulting picture; it was then the task of draftpersons to produce a good, readable drawing. Designers use pencils while designers use erasers.

A mold should be designed with care, ensuring the best possible outcome. It is always possible to find different ways to accomplish the same goal; in fact, all mold designers have their own ideas when it comes to solving a particular design problem. A designer should consult a colleague, or arrange a design meeting of peers to discuss the proposed design, after creating the mold layout, to take advantage of various ideas and to arrive at the best mold. Providing two or more layouts is even better in many cases. From these options, the best design should be chosen as a composite or the result of combining different ideas.

Every major design office in the world follows this standard procedure. Peer critique may seem time-consuming, but it’s usually worth the effort (and emotional drain) to arrive at a better mold. It is imperative that someone who is familiar with machining and assembly practices attend such design meetings, because mold designers (especially beginners) are not always familiar with these practices; this prevents design of mold parts that will be difficult (or even impossible) to manufacture economically or to assemble. An expert who understands the molding process can also offer valuable input on a new layout. If an error is caught during the design stage, it is much cheaper than to discover it later when steel has been cut or, even worse, after the mold is built.

The designer can be involved in the mold-making process to save time and money, rather than rushing through the design stage to save a few hours through the design office. Estimate how much time to devote to designing and detailing, 60-70% to machining, and 15-20% to assembling the mold when estimating the total time needed to build the mold. The better the drawing is, the less time is wasted during machining and assembly of the mold (this, of course, depends on the product shape and the complexity of the mold).