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Advice About Vacuum Thermoformed Packaging

Don’t get caught in a knowledge vacuum about this major way of producing plastic packaging.

Vacuum Thermoformed Packaging

Technologies that use heat in converting plastic into packages can be called thermoforming. With vacuum thermoforming, however, radiant heat is used to soften plastic sheet. Next, vacuum draws the sheet down into a female mold or down over a male mold, where the plastic takes shape. The plastic cools inside the mold. The shaped part is removed. Lastly, the part is cut and trimmed.

Packaging types include trays, kits, tubs, cups, blisters, and clamshells, used for food, medical device, and hardware—among other applications. As its description and applications might suggest, vacuum thermoforming is comparatively simple. But no technology is so simple that it is without pitfalls.

The central objective of vacuum thermoforming is the faithful three-dimensional rendering of a design, having a targeted wall thickness, uniformly distributed. That objective cannot be achieved if the design is poor. And since no one intentionally develops a poor design, it’s typically the result of not being aware of certain pitfalls that can manifest themselves aesthetically, functionally, and cost-wise. Of the various design features in which pitfalls lurk, three major ones are draw ratio, draft angle, and corners & radii.

Draw ratio is a calculation that divides the surface area of the mold by the footprint of the plastic sheet. Setting math aside, empirically, the more a plastic sheet is stretched (i.e., the deeper the draw), the thinner the walls. Draw ratio, therefore, is useful in determining the minimal starting thickness for the sheet. Without such knowledge, walls can end up too thin and subject to physical defects/damage. In contrast, walls that are thicker than needed waste money, in addition to violating principles of sustainability.

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