Also referred to as vacuum molding or thermoforming, vacuum forming is a
process in which a sheet of heated plastic material is shaped to a
mold, known as a buck. A type of pressure forming process, vacuum
forming is among the oldest of plastic forming techniques. Twin sheet
thermoforming is a sub category of vacuum molding, a slightly different
process that heats 2 separate sheets of plastic and welds them together
to make a hollow part or product.
Some benefits of vacuum forming include low tooling costs, quick start-up and cost-efficiency for small to medium production runs. Industries that utilize vacuum forming include food and beverage, sporting goods, electronics, medical, appliance, automotive, cosmetics and telecommunications. Vacuum forming and pressure forming are often used to form plastic packaging for other items, either for their safekeeping or for aesthetic purposes. However, both forming methods can be used for other applications such as creating signs for convenience stores and gas stations. Vacuum formed plastics are three-dimensional shapes that include a long list of plastic packaging such as vacuum packaging, blister packs, plastic trays, plastic covers and clamshells. Offering exceptional design flexibility, the vacuum forming process also varies in terms of complexity, ranging from a small tabletop machine to very large production machines. Typically, vacuum forming is limited to forming plastic parts that have a relatively shallow depth.
There are numerous different thermoplastic materials that are used in the vacuum forming process; the type of thermoplastic used depends on the application. Polyester (PET), for instance, is used for packaging such as food containers, processed meat packages, beverage containers and boil-in food pouches. Although it can be difficult to form, high density polyethylene (HDPE) is commonly used for detergent bottles, cereal box liners, milk bottles, margarine tubes and plastic bags. Polyvinyl chloride (PVC) is often used for food wrap, vegetable oil bottles and blister packaging. Another common thermoplastic that may be difficult to form is low density polyethylene (LDPE), which is used for garment bags, shrink-wrap, plastic bags and squeezable food bottles. Polypropylene (PP) is often used to form yogurt containers, container caps and medicine bottles. High grades of polystyrene (PS) are best for use in vacuum forming applications such as disposable plastic silverware, compact disc jackets, egg cartons and fast food trays. Other materials that may be used in vacuum forming services include acrylonitrile-butadiene-styrene (ABS), acrylics, polycarbonate and Kydex, which is a PVC-based thermoplastic.
There are three main types of plastic packaging; blister packs, clamshells and plastic trays. A blister pack is a broad term that encompasses several types of pre-formed plastic packaging. Most often used for small consumer goods such as unit-dose packaging for pharmaceutical tablets or capsules, pharmaceutical blister packaging and other vacuum formed blister packs are able to provide barrier protection in order to meet shelf life requirements as well as a level of tamper resistance. Clamshells, unlike blister packs, refer to a specifically-shaped container. One of the most popular plastic packaging, a clamshell is two hinged halves of a plastic shell that encapsulates the product. Clamshell packaging is not designed to be easily opened by hand and often require the use of a pair of scissors or a sharp knife to open. Plastic trays, also referred to as blister trays, are flat shallow containers that typically have slightly raised edges. Vacuum formed trays are often used for carrying, displaying or holding articles such as food or glass. The most common types of plastic trays are plastic food trays and plastic storage trays. Vacuum packaging is different from other types of plastic packaging because it is a method of packaging as well as a type. Vacuum forming packaging is used to store food in an airless environment such as an air-tight bottle or pack. The vacuum pack is made air-tight through a vacuum environment that works to remove oxygen from the package.
In the most common vacuum forming process, a plastic sheet is fed from a roll or an extruder into a set of guiding chains that use spikes to pierce the sheet and transport it through an oven to be heated to a high enough temperature for forming. The pliable heated plastic sheet is then guided into a form station where a mating mold and pressure-box enclose the sheet. Within the form station a vacuum is used to remove to create an air-tight environment and to pull the plastic sheet into or onto the male, meaning protruding, or female, meaning recessed, mold. This causes the heated plastic sheet to conform to the mold's shape. The vacuum environment is achieved through venting holes in the mold that are joined to vacuum lines. After a thermo forming cycle, a burst of reverse air pressure may be used to break the vacuum and assist the vacuum formed parts off of, or out of, the mold. The sheet containing the formed parts can then be trimmed either in a trim station on the same machine or it can travel to a separate trim press. Pressure forming is very similar to plastic thermoforming, except pressure thermoforming uses both the vacuum environment as well as additional air pressure to increase the tightness of the sheet onto the mold and create highly detailed vacuum formed plastics.
Vacuum Forming Types
- Blister packs are clear plastic, nonresealable packaging used for products that could be tampered with.
- Clamshells are plastic packages that have hinges to open and close like a clam's shell.
is like snapback forming except
that the thermoplastic sheet is stretched to the base of the mold.
In both cases, the use of air to stretch the material prior to vacuum
sealing and application to the mold permits the material to thin uniformly.
- Plastic covers are vacuum formed plastics designed to secure, contain and protect objects from environmental conditions such as weather, lighting, dust, water or other debris.
- Plastic forming is a group of manufacturing procedures that take thermoplastics and form them through molding processes into a wide variety of plastic products for numerous industrial, commercial and domestic applications.
- Plastic packaging encompasses all storage or containment devices produced through the manipulation of any number of polymer resins.
- Plastic trays are shallow platforms with raised edges intended to stop contents from sliding or rolling off of the surface.
is a thermoforming procedure that uses a plug or male
mold to press the heated thermoplastic material into the female mold
prior to the application of a vacuum. This method helps uniformly
distribute the sheet.
- Pressure forming is a thermoforming procedure that involves applying pressure to the
top of the plastic sheeting while the vacuum force pulls downward. Pressure
forming is done through air pressure or mechanical means, and provides
greater precision because the plastic is able to attain a greater definition
of shape in the mold.
is the process of pre-stretching the sheet
material with a vacuum box. A partial vacuum is then applied
to the box, just enough for the necessary stretching, and the mold
into the material where the box is vented to atmospheric pressure
that draws on a vacuum.
is vacuum thermoforming using only female
molds that produce a material distribution that is the opposite
of the results
obtained from male molds.
- Thermoforming involves heating and stretching plastics.
- Twin sheet thermoforming is a plastic processing technique involving vacuum forming two separate plastic sheets simultaneously before welding them together to create a hollow part or product.
- Vacuum formed plastics are created by a thermoforming process that uses a vacuum to suck the plastic sheet into a mold.
- Vacuum molding is a type of manufacturing method that takes thermoplastics and forms them through a molding process into a wide variety of plastic products.
- Vacuum packaging can refer to both those items held or displayed in reduced oxygen containers and any and all packaging materials produced through vacuum forming.
Vacuum Forming Terms
- The dark particles that appear
in plastic film during thermoforming processes because of contamination.
- The characteristic of some plastics of losing their colors
when coming into contact with water or certain solvents. Also, this is
the undesirable movement of materials to the surface of plastic or into
an adjacent material.
- Thermoformed semi-rigid plastic shells, typically made
to conform to the shape of the product being packaged.
- A protrusion on a plastic part that adds strength, assists
with alignment in assembly and allows for fastenings.
- Portions of thermoformed plastic where vacuum and
heat produce an opening in weak or thin points.
- A change in the structure of a plastic material.
- The detachment of thermoformed parts, like blisters, from
one another for the next phase of the packaging procedure.
- The process of removing static electricity from
plastic so that less dust clings to it.
- The use of a steel rule die to cut finished sheets of blisters
or blister cards to create individual pieces.
- The degree to which the sidewall of a blister or
clamshell is tapered to smooth the progress of the removal from the thermoforming
mold and denesting of the blister.
- A technique that creates depressions in a specific
pattern on plastic film and sheeting.
- The tendency of thermoformed plastic
to crack under the influences of certain chemicals.
Female Mold - A concave mold, referred to as a negative or cavity mold.
- A blister
card that is scored and die cut, permitting entrapment of the blister
between the two halves of the card. This supplies a seal between two boards
or between a board and a blister flange, especially useful when blister
packaging heavy items.
Gas-flush - During vacuum packaging, the chamber is flushed with nitrogen, keeping the plastic from sucking down tightly to fragile products.
- The process of joining two or more plastics together
with the application of heat and pressure.
Male Mold - A convex mold, referred to as a positive or protruded mold
- The result of inadequate contact of the plastic material
with the surface of the mold due to trapped air, moisture on the surface
of the mold or low pressure in irregular indentations on the material's
- A model of an intended
part. Prototypes show the final size as well as the design.
- Thermoplastic material derived from industrial
plastic scrap from a different processor.
- The flow of heated plastic
sheeting in a thermoforming procedure in which molten plastic sheets sag
before forming. The distance of the sag is determined by an electric eye
and is good for determining the forming readiness of the material.
- A heating procedure before forming a thermoplastic
sheet that involves heating both sides.
- Any plastic material,
which is not part of the product, that results from a molding procedure.
This material is typically tip scrap and can be reused.
- The construction required to create plastic sheeting,
comprised of an extruder, die, polish rolls, conveyor, draw rolls, cutter
and a stacker.
- The minute change in length or volume of a
material when subjected to heat.
- A double blister for encapsulating a product
for product visibility on two sides.
- An indentation or protrusion that hinders the removal
from a mold.
Unit Dose Packaging - medicine blister packaging in terms of single dosages for clarity purposes.
Vacuum Form Table - A machine that produces vacuum formed parts and products.
Vacuum Formed Lexan Component - Engineered Plastic Products, Inc.
Vacuum formed plastics - Engineered Plastic Products, Inc.
Conlet Vacuum Formed Plastic Case Component - Conlet Plastics, Inc.
Conlet Vacuum Formed Plastic Component - Conlet Plastics, Inc.
Vacuum Formed Plastic Panel - Conlet Plastics, Inc.
Vacuum Formed FRABS - Engineered Plastic Products, Inc.