Thermoforming is one of many manufacturing processes that converts plastic resininto usable everyday products.
Thermoforming is greatly relied on in today'ssociety because of the tremendous need for high volume plastic products.Thermoforming is considered to be one of the most cost-effective processes inplastics manufacturing. Thermoforming is considerably economical because of thelow molding costs and fast molding cycles. Speed and cost efficiency are thehighlighted qualities that thermoforming offers which lead the way for theprocess becoming so important in industry today. The basic concept ofthermoforming is quite simple.
A premanufactored thermoplastic sheet is heateduntil it becomes soft and pliable. It is then forced against the contours of amold until it cools to its original state. Once it has cooled it is removed fromthe mold while still obtaining the shape of the mold. Usually the product isthen trimmed to produce the finished product.
The operation seems simple andstraight foreword but there are many different applications associated with theprocess. Thermoforming is a broad term; there are many different types ofthermoforming processes. These processes all have similar traits but they dodiffer in certain aspects of the overall process. Trapped Sheet Forming is aspecialized type of thermoforming.
In trapped sheet forming a hot blow plate isused in both the heating and forming process. A plastic sheet is positionedbetween the hot blow plate and the female mold cavity. Air forced through theplate and pressure from the female mold combine to thrust the sheet onto the hotplate. The sheet is then heated and forced into the female mold by the use ofair pressure. One advantage to trapped sheet forming that is such a simplifiedprocess that many products can be produced from this method. Also the processuses contact heating, which is easily used and is not subject to temperaturefluctuation.
The contact heating is a definite advantage but is also a slightdisadvantage. The problem with contact heating is that heat can only be appliedto the underside of the sheet. This slows down the process and restricts the useof the more durable heavier -gauge sheets. Plug-assist forming is one of themost widely used thermoforming processes today.
In plug-assist forming a heatedsheet is sealed over a female cavity. Once the plastic is sufficiently heatedthe plug-assist, which is shaped like the female cavity but slightly smaller insize, pushes the plastic sheet and forces it in the cavity. Vacuum force pullsthe sheet onto the mold surface. The main advantage associated with plug-assistforming is that the walls of the container can be measured precisely with theassist. Wall thickness is uniformly the same throughout the container.
Plug-assist forming works well with both heavy and light gauge materials and iscommonly used to form deep-drawn containers. Pressure bubble plug-assist vacuumforming is similar to plug-assist forming. In this forming process a portion ofthe sheet is stretched to guarantee an even thickness of walls. The heated sheetis positioned over the female cavity. Air is then blown up through the baseplate channel.
This air causes the sheet to billow upward. The sheet is thenpushed into the cavity by the plug-assist. Vacuum is then applied to transportthe sheet to the mold. The advantage to this forming technique is that the wallthickness can be measured with great accuracy. This process, as with plug-assistforming, is used to create deep-drawn containers.
Pressure bubble snapbackforming is similar to bubble plug-assist forming except for one aspect. Theplastic sheet is not formed by the female mold but rather the male mold. Thesheet is snapped back to form against the male mold. This forming processimproves material distribution because of its prestrecthing procedures. Thesnapback vacuum forming method is popular because of its simplified process. Asheet is clamped over a female cavity, air pressure through the base plate thenstretches the plastic.
The pressure is then turned off while the vacuum isturned on to pull the plastic into the mold. This process is widely used toproduce auto parts and luggage due to its ability to create external deep draws.It works well with all medium to heavy -gauge sheets. The processes mentionedare just a handful of the many thermoforming processes out in the industrytoday.
Everyday better more reliable products are being manufactured bythermoforming methods. Improvements are consistently being applied to thedifferent processes to ultimately create better products. Thermoformings placein the plastics industry will continue to remain strong because of the dynamicsof its manufacturing process.
