Thermoforming is a manufacturing process in which the plastic sheet is heated to a flexible forming temperature, molded into a particular shape in the mold, and trimmed to create a usable product. Sheets, or "films" when referring to thin gauges and certain types of materials, are heated in an oven to a sufficiently high temperature that allows it to be stretched into or into the mold and cooled to the finished shape. The simplified version is a vacuum.
In its simplest form, a small table or lab-size machine can be used to heat small pieces of plastic sheet and stretch it over the mold using a vacuum. This method is often used for sample sections and prototypes. In complex and high-volume applications, very large production machines are used to heat and form plastic sheets and trim parts formed from sheets in a continuous high-speed process, and can produce thousands of finished parts per hour depending on the machine and the size of the mold and the size of the parts formed.
Thermoforming differs from injection molding, blow molding, rotational molding and other forms of plastic processing. Thin-gauge thermoforming mainly manufacture disposable glassware, containers, lids, trays, abrasions, clamshells, and other products for the food, medical, and general retail industries. Thermoforming thick-gauge includes diverse parts such as vehicle doors and dash panels, refrigerator liners, utility vehicle beds, and plastic pallets.
In the most common method of high volume, the continuous thermoforming of a thin gauge product, the plastic sheet is fed from the coils or from the extruder into a set of indexing chains that combine pins, or spikes, that pierce the sheets and transport them through the oven for heating to form temperature. The heated sheet is then indexed into the form of the station where the matrimonial mold and the pressure box are sealed on the sheet, with vacuum then applied to remove the trapped air and pull the material into or into the mold together with the pressurized air to form the plastic into the printed detail. (Plug-assist is usually used in addition to the vacuum in the higher case, the deeper part to form the distribution and thickness of the required material at the end.) After a short-form cycle, the reverse air pressure burst is moved from the vacuum side of the mold as a form tool open, usually referred to as an air-release, to break down the vacuum and to assist parts that are formed from, or out of, mold. Stripper plates can also be used in molds as they are open for the discharge of more detailed parts or parts that have negative areas. The sheet that contains the parts formed then indexes to the trim station on the same machine, where die cuts parts of the remaining web sheets, or the index becomes a separate trim press where the parts formed are trimmed. The remaining web sheets after the trimmed parts are usually wrapped around the take-up reel or inserted into the inline granulator for recycling.
Most thermoforming companies recycle their waste and plastic scraps, either by compressing in a propeller or by feeding into a granulator and producing soil debris, reselling them for reprocessing or re-use at their own facilities. Often, scrap and waste plastics from the thermoforming process are converted back into extruded sheets to form again.
Video Thermoforming
Thin measurement and thickness (thickness) thermoforming
There are two general categories of thermoforming processes. The thickness of the sheet less than 1.5 mm (0.060 inches) is usually sent to the thermoforming machine from the roll or from the sheet extruder. The application of roll-fed or inline thin-gauge thermoforming applications is dominated by rigid or semi-rigid disposable packaging. The thickness of the sheet more than 3 mm (0.120 inches) is usually delivered to the forming machine by hand or by the automatic filling method that has been cut to the final dimension. Thermoforming application of thick or thick pieces of pieces, mainly used as permanent structural components. There is a growing medium-small market that forms a sheet of thickness of 1.5 mm to 3 mm.
The measuring-weight meter uses the same basic process as the continuous formation of thin sheets, usually placing a plastic sheet heated over a mold. Many machine-building applications use vacuum only in the form process, although some use two parts of the marital form tool and include air pressure to help shape. Window shutters and turret windows of machine guns spurred the technological advancements of heavy equipment during World War II. Heavy spare parts are used as cosmetic surfaces on permanent structures such as kiosks, cars, trucks, medical equipment, material handling equipment, refrigerators, spas and bathroom covers, as well as electrical and electronic equipment. Unlike the thinnest thermoformed parts, heavy-gauge parts often work hand after forming for trimming to the final shape or for additional drilling, cutting, or finishing, depending on the product. Heavy-duty products are usually "permanent", but thin-gauge parts are often designed to be disposed or recycled and are primarily used for packaging or storing goods or food products. Thermoforming weight measurements are typically used for a production amount of 250 to 3000 per year, with lower tooling costs and faster product development than competing plastic technologies such as injection molding.
Maps Thermoforming
Engineering
Thermoforming has benefited from the application of engineering technology [3] , although the basic forming process is very similar to what was discovered several years ago. Microprocessors and computer controls in more modern machinery make it possible to greatly improve process control and repetition of the same work settings from one running production with the ability to store an oven heater and setting the timing between jobs. The ability to place molded sheets into inline trim stations for more precise trim registrations has been greatly improved due to the general use of electric servo motors for chain indexing over air cylinders, gear racks, and clutches on older machines. Electrical servo motors are also used in some modern and sophisticated shaping machines for actuation of machine plates where tool shapes and trims are installed, rather than air cylinders that have traditionally been the industry standard, providing more precise control over closing and opening speeds and tooling times. Quartz and glow heating oven heaters generally provide more precise and thorough heating of sheets of older cal-rod types, and better allow zoning ovens into manageable hot areas.
New technology, ToolVu, has been developed to provide real-time feedback on the [7] thermoformer engine. This stand-alone system connects directly to the thermoformer and uses multiple sensors to record production-run data in real time including air pressure, temperature, strain gauges and other specifications. This system sends many warnings and warnings if the predefined production parameters are compromised during the process. This reduces machine downtime, decreases startup time and reduces startup memos.
An integral part of the thermoforming process is tooling, which is specific to each piece to be produced. Thin-gauge thermoforming as described above is almost always done on an in-line machine and typically requires mold, assist plug, pressure box and all mounting plates as well as parts of work-related trim tools and stackers. Thermoforming that is thick or heavy also requires special tools for each part, but because the size of the parts can be very large, molds can be cast aluminum or some other composite material as well as aluminum machines as in thin gauges. Typically, the thick gauge section should be trimmed on a CNC router or hand-trimmed using a chainsaw or hand router. Even the most sophisticated thermoforming machines are limited to the quality of the tool. Some of the major thermoforming manufacturers choose to have designs and tool-making facilities at home while others will rely on outside tool-making shops to build tools.
Printable type
- plaster paris
- wood prints
- plastic mold
- aluminum mold
Industry
The more than $ 10 billion North American market has traditionally been a thin gauge and weight gauge. In 2003 there were about 150 thin gauge thermoformers in North America. Sixty percent form exclusive products. Thirty percent are habit-makers and 10 percent are OEMs with the ability to form in-house. There are nearly a dozen thin shapers that have annual sales of at least US $ 100 million. The biggest one has annual sales of over $ 1,000 million. There are about 250 machine builders in North America. Almost all are habit-makers. Only two or three weight shapers have annual sales of more than $ 100 million. The biggest one has annual sales of about $ 140 million. [2] Beaverton, Michigan, is known as the Thermoforming Plastics world capital sparked by the proximity of the Dow Chemical Company in Midland, Michigan.
See also
- The blister package
- Blow molding
- Microthermoforming
- Packaging
- Thermoplastics
Source of the article : Wikipedia
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