Qualities Of A Good Mold Design For An Injection Mold

Every single plastic item we use was, at one time, just a mold design. This can range from a very simple sketch done to flesh out a concept, or, in most cases, it is a very sophisticated model done using high end CAD design software.

The plastic injection molding process is a rather involved part of manufacturing and mold design plays a critical role. Consider that an injection mold can cost from $20,000 to over $500,000 and you can appreciate the importance of a good design.

7 Qualites Of A Good Plastic Mold Design

1. Manufacturability. If a mold cannot be machined without using highly complicated machines and set-ups chances are it is too complicated. Some plastic part designs are such that there is no other way beside the complicated, but most things can be made more simple.

2. Maintenance must be considered. At some point in the life of most molds there will be mold maintenance to deal with. Components that can be extracted in the molding machine are great because they save a huge amount of down-time.

3. Proper materials must be used in the manufacturing process. Component failure due to the wrong steel can be disastrous, for example. Using dis-similar steels or steels of differing hardness when the possibility of wear is a factor makes a huge difference.

4. Proper cooling of the mold is essential. Hot spots or cool spots create surface blemishes that just cannot be processed out. The use of mold flow analysis software is helpful, but so is a lot of observation and common sense.

5. Correctly sized gates and runners are critical. The entire mold design may be wonderful, but if the gates and runners are inadequate, the part will never properly fill. This is part science and part art; born out of experience.

6. Adequately drafted side walls are often overlooked. If the dimensional tolerances allow for the size variation of a drafted wall, by all means use it. This makes life easier for the EDM department, the polisher, the high speed milling machine operator and the molding technician.

7. Using common sizes in various mold components makes the machining operations much easier to perform as well as plan. Why make one block slightly different from another just because the CAD lines fell that way? It is much easier to gang up parts to combine machining operations.

While there is an almost endless list of what makes for a good mold design, these highlighted points are certainly near the top of the list. By paying careful attention to the basics many of the more critical aspects are naturally taken care of.