When the Academy Award winning move, The Graduate¸ helped launch Dustin Hoffman into fame, it helped the word “Plastic” move to the top of everyone’s mind.
In the movie, Benjamin (Dustin Hoffman) told Mr. McGuire (Walter Brooke) that he was worried about his future and that he wanted to be different, he received this response
Mr. McGuire said, “I just want to say one word to you. Just one word.”
Benjamin replied, “Yes, sir.”
Mr. McGuire said, “Are you listening”?
Benjamin replied, “Yes I am.”
Mr. McGuire said, “Plastics”.
From that moment forward, Plastics assumed a prominent place in everyone’s mind and foreshadowed Plastic as the materials choice for so many products we use today.
Plastic can be formed into almost any size or shape imaginable through different plastic forming methods. Injection molding and thermoforming account for most of the plastic parts manufactured today.
Here’s the simple truth about them.
- If you plan to have a short production run (under 2000) of a new part you have designed, Thermoforming should be considered. Thermoforming molds are much less expensive that injection molding molds and offer a distinct advantage in low production run projects.
- For long production runs, molds that are used in Injection Molding, while much more expensive than Thermoforming molds, truly offer lower part prices.
- Often a company that anticipates long production runs in the future, but not immediately, will choose thermoforming because the molds are less expensive even though the part price can be higher. Then, when they see that the product has really taken off and will require very large production runs, they convert to injection molding.
- Designers often feel that the cosmetic appeal of an injected molded part is far superior to parts that are thermoformed. This is not true because thermoformed molds can be designed to produce really elegant finishes. Don’t confuse your need for beautiful finishes based on thinking that injection molded parts offer the only solution. Once again, do use injection molding for large production run parts, and thermoforming for shorter production runs. Both can produce beautiful finishes.
- Thermoforming is a method in which huge plastic sheets can be molded into huge objects. All other methods are used for making small objects.
- Superior quality products using more plastic are formed by thermoforming. As a result, thermoformed parts are more durable than those created by other methods.
- Injection molding incurs extremely high start-up costs and requires a great deal of engineering time. Since there are long time frames necessary to fabricate tooling, the time-to-market is a major drawback.
While the use of plastic has increased since Mr. McGuire gave Benjamin the tip of a lifetime, astute designers and mechanical engineers who design their plastic products for the right forming process will produce parts most cost efficiently.