Many clients throughout the Wellington area have heard the term vacuum forming, but they do not know what it really means, and they don’t know what it does or how it can help them in their business. Vacuum forming is a procedure that can shape performance plastic sheet materials into many different forms, and it is one of the best ways to make a host of different plastic products.
How Does it Work?
A type of thermoforming, vacuum forming, is a process by which a plastic sheet or thin sheet of plastic, such as a PVC sheet, is heated up so that it becomes malleable. The heating process includes the use of aluminum plates and infrared heaters. The heat application will come from the top and the bottom so that it is uniform and will provide the best results.
Once the heat finally reaches the proper temperature (which can differ based on the thickness of the sheets in use) the vacuum will mold the sheets to form the product. The vacuum is able to provide an airtight environment, which is going to be better for the overall molding process.
Products from Vacuum Forming
With this type of thermoforming, one could create countless types of products, and you may find that your company could benefit greatly from the process. One of the most common products using vacuum forming today are children’s plastic toys, but that’s just one of the possibilities. Product packaging is another option, and it is one most companies that create, manufacture, package and sell products could use. Most of the plastic items that you see around the home and office have gone through some type of thermoforming, and it’s often the vacuum process.
Wellington Best Plastic Sheet Supplier
Plastics cover a broad field of organic synthetic resin and may be divided into two main classifications - aerospace thermoplastics _ and aerospace thermosetting plastics. Thermoplastics may be softened by heat and can be dissolved in various organic solvents.
Thermoplastics may be softened by heat and can be dissolved in various organic solvents. Two kinds of transparent thermoplastic materials are commonly employed in windows, canopies, etc. These are known as acrylic plastics and cellulose acetate plastics. Cellulose acetate was used in the past but since it is dimensionally unstable and turns yellow after it has been installed for a time, it has just about passed from the scene and is not considered an acceptable substitute for acrylic. Acrylic plastics are known by the trade names of Lucite or Plexiglas and by the British as Perspex and meet the military specifications of MIL-P-5425 for regular acrylic, MIL-P-8184 -~ 184 for craze-resistant acrylic.
Aerospace Thermosetting Plastics.
Thermosetting plastics do not soften appreciably under heat but may char and blister at temperatures of 240 to 260 'C (400 to 500 °F). Most of the moulded products of synthetic resin composition, such as phenolic, urea-formaldehyde, and melamine formaldehyde resins, belong to the thermosetting group. Once the plastic becomes hard, additional heat will not change it back into a liquid as it would with a thermoplastic.
Storage and handling.
Because transparent thermoplastic sheets soften and deform when they are heated, they must be where the temperature will never be excessive.
Transparent acrylic plastics get soft and pliable when they are heated to their forming temperatures and can be formed to almost any shape. When they cool, they retain the shape to which they were formed. Acrylic plastic may be cold-bent into a single curvature if the material is thin and the bending radius is at least 180 times the thickness of the sheet. Cold bending beyond these limits will impose so much stress on the surface of the plastic that tiny fissures or cracks, called crazing, will form.
Simple Curve Forming. Heat the plastic material to the recommended temperature, remove it from the heat source, and carefully drape it over the prepared form. Carefully press the hot plastic to the form and either hold or clamp the sheet in place until it cools. This process may take from ten minutes to one-half hour. Do not force-cool it.
This type of forming is normally used for such parts as canopies or complex wingtip light covers, and it requires a great deal of specialized equipment. There are four commonly used methods, each having its advantages and disadvantages.
Stretch forming. Preheated acrylic sheets are stretched mechanically over the form in much the same way as is done with the simple curved piece. Special care must be taken to preserve uniform thickness of the material, since some parts will have to stretch more than others.
Male And Female Die Forming. This requires expensive matching male and female dies. The heated plastic sheet is placed between the dies which are then mated. When the plastic cools, the dies are opened.
Aerospace Vacuum Forming Without Forms. Many aircraft canopies are formed by this method. In this process a clamp with an opening of the desired shape is placed over a vacuum box and the heated sheet of plastic is clamped in place. When the air in the box is evacuated, the outside air pressure will force the hot plastic through the opening and form the concave canopy. It is the surface tension of the plastic that shapes the canopy.
Aerospace Vacuum Forming With A Female Form. If the shape needed is other than that which would be formed by surface tension, a female mould, or form must be used. It is placed below the plastic sheet and the vacuum pump is connected. When air from the form is evacuated, the outside air pressure will force the hot plastic sheet into the mould and fill it.
Aerospace Plastics For Aircraft Plastic Components
The world is an ever changing and frequently hostile environment. Damage can be caused by a range of factors: from storms, floods and tornados to fires, hurricanes and earthquakes - all natural disasters.
This is certainly evident in the recent earthquakes and tsunami that ravaged Japan and Haiti. In addition, we have man made disasters. The nuclear concerns in Japan have captivated people's attention throughout the globe. The Gulf Oil Spill is an example of another environmental disaster. Plastic materials are the perfect choice in prevention, preparedness and clean up from natural disasters.
Plastics in disaster preparedness.
Many plastic materials are used in the prevention, control and repair management - whenever and wherever a natural disaster may occur.
One of the most visible plastics is the Polycarbonate used in hurricane window covers / shutters. Polycarbonate is a clear rigid plastic that has extremely high impact strength, and is the material most commonly known as 'Bullet Resistant Glazing'. It is used in safety glasses, riot shields and bank theft prevention glazing. The Polycarbonate protects windows and inhabitants from flying debris and breaking glass caused by the high winds, hurricanes and tornadoes. Use of the Polycarbonate window coverings saves homes from damage, and helps reduce insurance premiums.
Hillsides are affected by storms and heavy rains, causing mud slides. The standard and most popular solution is to cover hillsides with Polyethylene film. This helps to prevent the rains from saturating the ground and causing the ground to move or shift. The Poly film is normally.004" -.010" thick in widths up to 20 feet and lengths of 100 feet (the same material used as painters tarps from home improvement centers). This film is then attached to the hill with spikes, stakes or sand bags; and this material sheds the water rather than letting it soak in. It can be applied with folds and used like rain gutters to direct water flow away from specific areas. Also, the current sand bags used are not the old cotton fabric bags used years ago; they are now a high strength and tear resistant woven polypropylene 'fabric' bag.
The recent critical issues with nuclear leaks bring up an interesting use of a plastic material. As you may recall, after the earthquake and tsunami, the Japanese energy experts were pumping water and boron into the reactors to help control the amount of nuclear energy released. The nuclear industry uses a plastic material, High Density Polyethylene (HDPE) that has been filled with the natural mineral boron. This boron filled (typically a 5% boron fill) is used to shield neutrons and nuclear energy in many applications; nuclear submarines, nuclear power plants, hospital radiation, dental x-ray shielding and industrial radiation applications. It is normally produced in sheet, and can then be mounted in and around the radiation source as shielding. The benefit to using this boron filled HDPE is this sheet weighs significantly less than traditional lead shielding, and is therefore much easier to install.
Plastic used in clean up from disasters.
It is much more difficult to clean up after natural disasters occur. Many of the methods used in the preparation limit the amount of clean up caused by natural disasters.
Depending on the severity of the natural disaster, the uses of plastics in the aftermath are almost limitless. In the cleanup and rebuild after major Earthquakes, shelter is a key component. One of the quick shelters brought in are simple wooden frames with twin-wall plastic sheets made from either Polypropylene or Polycarbonate stapled or nailed to the framework. This provides an inexpensive, easily movable and effective shelter for short term housing. The twin-wall design provides excellent insulation and energy savings. This style shelter is foldable, easy to transport and very easy to set up. Several versions can be made from small huts to larger family areas, to separate sanitary latrine units. These extruded twin-wall materials work well to protect against rain and excessive exposure to the elements. These can be used as assembled, or with a sand bag reinforced perimeter. In Haiti, there were reports of residents filling used one gallon water bottles with mud, and building shelters with these mud building blocks.
The gulf oil spill brought plastics to the front line in disaster cleanup again. Materials used to collect and dispose of excess oil from the waters were rushed to the area. Polyethylene bags are used to collect the oil covered and saturated cleaning rags and clothes, preventing additional dispersion. Many varieties of machinery were brought in to clean the waters. One style machine uses 8" UHMW rod as a squeegee roller that grabs the oil from the water surface and then collects it for later use. Oil booms and rotary wheels are common systems for collecting oil from spills. Because plastics have great surface tension, the oil 'sticks' to the plastic surface during the cleaning process. Then the plastic surfaces are wiped clean for reuse and capturing the oil. Plastic tubes and hoses are used to move the oil after collection.
A significant use of plastics would be in the aftermath of natural disasters, specifically in the sanitation and clean water areas. First is sanitation; plastics are used in keeping items clean and dry. Polyethylene film covers items such as medical supplies, shelters, clothing and food cartons. This film keeps the items protected during shipment and ready for use.
Water is the second area of concern. Clean water is critical during the clean up and resettling after a natural disaster. Individual use water bottles are the quick and easy way to deliver water. Larger rotationally molded tanks are brought in with the ability to store large amounts of water in the areas affected. Reverse osmosis equipment (many components are made from plastic) is brought in to convert contaminated water in the clean potable water on site.
In all of these examples, plastic is lighter in weight than the alternatives, normally less expensive that the alternatives, it lasts longer and the plastics are recyclable.
Plastics are excellent choices for material to use in natural disasters.