1. Although most injection molds are made of steel, at Creative Mechanisms we sometimes use aluminum alloy 7075. Its strength is comparable close to steel and has a good strength-to-density ratio. It also withstands heat well and can be polished to a high shine gloss surface finish.
2. Aluminum can also be used to inject into the molds to make the products. However, it’s
not very common and Creative Mechanisms deals strictly in plastic.There is a vast array of plastic materials that can be used for injection molding. Our aluminum molds can be used with most of them. The most common plastics we mold are ABS, Styrene, and Polypropylene.
3. For very detailed parts with a fine texture or complicated surfaces, we use an electric discharge machining (EDM) process. This involves building a copper electrode into the shape/design we want and using it to create a spark. The spark then burns the steel into the shape/design of the electrode.
4. If a part has some kind of texture on its surface, we might send it out to a company vendor that uses chemicals for etching textures does chemical etching for surface finishes. A “mask” is put on the tool to block the chemical where it is unwanted and then the chemical is applied, which etches the texture onto the surface of the part. The non-textured surfaces are then polished to give them a smooth finish.
5. Molds rarely work perfectly the first time, so if you work with a tool maker who gives you an 8 week delivery on the tool, be aware that that does not necessarily mean that your part will be useable in 8 weeks. Things that can’t be tested or measured until the mold is actually used will need fixing/adjusting after the first “injection” of plastic into the mold. This is known as tool debugging and people often do not allow enough time for or forget to include this important factor in their schedule.
6. As they say, “measure twice, cut once.” This applies in plastic injection molding as well as anything else; it is also important to stay on the "steel safe" side of a mold’s dimensions. What that means is that your tool maker should always have a little bit of extra material on the mold, just in case in the critical areas, for the first shots. It’s easier to remove steel than to add it, so it’s important to make sure that the tool has room for adjustments during that debugging process.
7. The molds made for prototypes are different from those that will ultimately be made for full-fledged product production. Our goal, and the goal of an injection molded prototype, is to prove feasibility our engineering and provide a limited number of production quality parts. This means that when Creative Mechanisms makes a prototype injection mold, our only goal is to make a “proof of function” model prove the engineering and demonstrate the function of the part in the production materials. We may choose a certain gate based on this goal location because we’re making only one part and because we are injecting molten plastic into only one cavity. Manufacturing, on the other hand, is making possibly millions of parts and may have, say, 64 cavities in their mold. Getting the plastic to flow into 64 cavities might require a change of location for the gate as well as other adjustment.
8. A client may use our prototypes for FDA trials or sales samples, but they rarely take the actual mold into production because, as previously mentioned, our molds are different from what they’ll need for higher volume manufacturing. What the client does take is the files that we have created for them. Those files prove that they have a truly manufacturable part.are the same ones used to make our prototype injection mold and will be used by the tool maker for the production tool as well.