A manufacturing process in which plastic extruded film .007 – .080 is heated to a pliable temperature, formed to a particular shape with the use of a mold, cooled and trimmed. Producing various engineering plastic manufacturing products, packaging clamshells, blisters & tri-folds & products point of purchase displays, inserts, and trays used in markets such as Cosmetics, Candles, Electronics, Food, Medical, Retail and more.
Our most common method of light gauge thermoforming is done inline, utilizing various rolls of fed plastic materials such as PET, PVC, Polystyrene, and Polyethylene offered in a range of grades general purpose, anti-static, medical, food and cosmetic and colors.
The material is fed from a roll or an extruder into a set of indexing chains containing pins or spikes that pierce the material and moves it through an oven containing ceramic radiant heating elements.
The material is then heated to the proper forming temperature and indexed to the forming station where a mold and pressure-box encapsulates the film. Vacuum is then applied to evacuate trapped air between the film and the mold. Atmospheric pressure is then applied to force the film to stretch and conform to the specific contour of the mold. Plug-assists can be utilized on deeper draw parts to deliver the needed material distribution throughout the finished part.
Once formed, a burst of air pressure is used to assist in the release of the formed part off of or out of the tooling as the mold and pressure-box separate. In some instances, a mold assists stripper plate is utilized in the mold to aid in the ejection of the detailed parts or those with a negative draft and or undercut areas.
Then, light gauge film containing the formed parts indexes into the inline trim station, where the parts are die-cut from the sheet web or indexes into a separate trim press where the formed parts are trimmed. Like Maryland Thermoform, most thermoforming and custom vacuum forming companies recycle their scrap and waste plastic, either by compressing like resins into a baling machine or by feeding directly into a grinder and producing ground flake for sale to reprocessing companies or re-use in their own facility. Frequently, scrap and waste plastic from the thermoforming process is converted back into an extruded sheet for forming again.
Light Gauge Thermoforming has benefited from applications of engineering technology, although the basic forming process is very similar to what was invented many years ago. Microprocessor and computer controls on more modern machinery allow for greatly increased process control and repeatability of same-job setups from one production run with the ability to save oven heater and process timing settings between jobs.
The ability to place formed the sheet into an inline trim station for more precise trim registration has been hugely improved due to the common use of electric servo motors for chain indexing versus air cylinders, gear racks, and clutches on older machines. Electric servo motors are also used on some modern and more sophisticated forming machines for actuation of the machine platens where form and trim tooling are mounted, rather than air cylinders which have traditionally been the industry standard, giving more precise control over closing and opening speeds and timing of the tooling. Quartz and radiant-panel oven heaters generally provide more precise and thorough sheet heating over older cal-rod type heaters and better allow for zoning of ovens into areas of adjustable heat.
A new technology, ToolVu, has been developed to provide real-time feedback on thermoforming machines. This stand-alone system connects directly to the thermoforming and utilizes multiple sensors to record production-run data in real time including air pressure, temperature, tool strain gauge and other specifications. The system sends out multiple warnings and alerts whenever pre-set production parameters are compromised during a run. This reduces machine downtime lowers startup time and decreases start-up scrap.
An integral part of the thermoforming process is the tooling which is specific to each part that is to be produced. Thin-gauge thermoforming as described above is almost always performed on in-line machines and typically requires molds, plug assists, pressure boxes and all mounting plates as well as the trim tooling and stacker parts that pertain to the job.
Thick or heavy-gauge thermoforming also requires tooling specific to each part, but because the part size can be very large, the molds can be cast aluminum or some other composite material as well as machined aluminum as in thin gauge. Typically thick-gauge parts must be trimmed on CNC routers or hand trimmed using saws or hand routers.
Even the most sophisticated thermoforming machine is limited to the quality of the tooling. Maryland Thermoform chooses to have design and tool making facilities in-house while others will rely on outside tool-making shops to build the tooling.
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