07-04-2012, 11:27 AM
THERMOFORMING
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PROCESS DESCRIPTION
Thermoforming is a collection of manufacturing methods that heat and form sheets of extruded
plastic. Thermoforming processes include drape, vacuum and pressure forming.
Drape forming relies on gravity to pull the sheet against the tool. Vacuum forming, as the name
implies, draws the heated sheet against the tool with the assistance of a vacuum. Pressure
forming combines vacuum and pressure to simultaneously pull and push the plastic sheet to the
contours of the tool.
This process guide documents the steps for vacuum forming since it is the most common
thermoforming method. However, many of the details presented may also be applied to drape
and pressure forming.
In vacuum forming, heated plastic sheet is drawn down onto a male or female tool that has vent
holes around the periphery and in areas requiring crisp detail. The application of a vacuum offers
improved feature defi nition and greater wall thickness consistency. Vacuum forming also allows
the use of thicker sheet stock and reduces forming time, when compared to drape forming.
APPLICATIONS
Packaging is the leading application for vacuum forming. The clear plastic bubble (blister pack)
that contains a product is vacuumed formed. The disposable plastic lid on a coffee cup is vacuum
formed as are the plastic and foam containers used in delicatessens and fast food restaurants.
While the packaging industry is the leading consumer of vacuum formed parts, the applications
extend across many product types and throughout many industries.
Automotive applications for vacuum forming include instrument panels (IPs), wheel covers
and door liners. In aerospace, covers and cowlings are commonly vacuum formed. Used for
boat hulls, the marine industry shows that vacuum formed parts can be large. There are many
applications in electronics, including anti-static conveyance trays. For custom machinery, covers
and shrouds are made quickly and cost-effectively with the vacuum forming process. The list of
applications for vacuum forming is virtually endless, as illustrated in fi gure 2.
AEROSPACE – VEHICLE DESIGN AND PRODUCTION
Military aircraft and airborne vehicles are sophisticated tools that are used for intelligence,
surveillance, targeting, and reconnaissance. A defense contractor applies FDM and vacuum
forming to prototyping and manufacturing of these complex systems.
The company uses a Fortus system and Formech vacuum forming system to reduce time, cost
and labor demands for components that include air ducts, engine cowlings and antennae covers
In one application, vacuum forming replaces pre-preg (pre-impregnated) carbon fi ber lay-up.
This manufacturing method is a labor-intensive process that requires cavity fabrication, hand
lay-up of the pre-preg material and a lengthy heat curing cycle. The process takes days and
numerous man-hours to complete. Using the Titan to construct a tool, vacuum forming begins in
as little as one day after a design is completed, and it is done with minimal labor requirements.
Since vacuum forming of the parts takes only minutes, prototype and production ducts, covers
and cowlings are made in less time than it takes to fabricate a fi ber lay-up tool. This company
demonstrates that vacuum forming is not just for prototyping vacuum formed parts. It can
replace other processes.
CONSUMER GOODS – PACKAGE DEVELOPMENT
Saving time and money are desirable outcomes. But phenomenal gains arise when the process
is changed. And that is what FDM and vacuum forming have done for the package development
efforts of one mass-market, consumer goods company.
Prior to implementation of FDM technology, creating tooling for vacuum forming required a full
man-day just for drilling of vent holes. Many of the tools used are multi-cavity, forming a dozen
or more parts in one cycle. With all of the cavities, there are 1,000 to 2,000 vent holes to be
drilled. With FDM tooling, the operation was eliminated.
CONCLUSION
In just fi ve simple steps, vacuum forming delivers plastic parts for prototyping and short-run
manufacturing. Whether the application is prototype blister packs or production engine cowlings,
plastic parts are delivered quickly and cost-effectively.
Applying FDM to the creation of vacuum forming tools offers additional advantages. Eliminating
the time and labor required of machined tools—CAM programming, set-up and operation—and
eliminating the vent drilling operation, FDM expedites the vacuum forming process while
decreasing costs and labor demands.
With this process guide and the necessary tools, companies in all industries can capitalize on the
effi ciency, simplicity and cost-effectiveness of vacuum forming.
For information on Formech vacuum forming machines, visit the company’s web site at
Images and information in fi gure 1-5 and 8-16 are courtesy of Formech International Limited.