BASIC VACUUM AND PRESSURE FORMING EQUIPMENT
How to make a vacuum chamber
An airtight vacuum chamber can be fabricated from welded steel plates. Steel should not be used for the forming plate since it may "chill" the hot sheet. A hardboard forming plate about 1/2 inch in thickness is recommended.

The detachable forming plate can be sealed to a flange on the top of the vacuum box using a gasket. The sheet blank is clamped in place over the forming plate using a clamping or holding ring and several toggle clamps.

The shape of the formed part's base will be determined by the shape of the cutout in the forming plate. Regulating the vacuum between the vacuum chamaber and a vacuum storage tank will control the height or depth of the part. Required equipment: a high speed vacuum pump (10 cfm minimum), a vacuum storage tank, a 1'' gate valve, a vent valve for releasing vacuum after the part is formed and a vacuum gauge.

Free blowing equipment
The required equipment for free blowing includes a plywood board with an air hose attached to its underside and a forming plate for controlling the piece's contour at its base. To evenly distribute incoming air, baffle the air intake with foam, felt or cardboard. Cover the plywood board with flannel or polyurethane foam to prevent mark-off. The forming plate or ring should be made from approximately 1-1/2'' thick hardboard. Quick acting toggle clamps may be used to attach the heated sheet and the ring to the plywood base.

Plug-and-ring forming equipment
Rings or plates can be made from hardboard, plywood or metal; plugs are usually made from hardwood, and the equipment should be coated with flocked rubber sheet to minimize mark-off. For producing large volumes of parts, durable aluminum rings and plugs can be used

For more information contact Mike at Ultra Acrylics, Inc.

Acrylic sheet can be thermoformed using several types of equipment employing a variety of heating methods. The following technical information is offered as a resource for thermoforming equipment and procedures. Users should undertake sufficient verification and testing to determine the suitability for their own particular purpose.

Heating Methods:
Vertical Ovens
Forced circulating-air ovens heat uniformly at consistent temperatures. These ovens consist of an outer and inner shell separated by a space containing fiber or rockwool insulation. Inside, the ovens have thermostatically controlled heaters. Ovens capable of operating at temperatures ranging from 140-380 degrees F (60-193C) and to within 10 degrees F (5C) are required; air velocities across the sheet should range between 200-100 feet per minute (1-5 m/s). Baffles and electric fans can also be used to ensure even heat distribution.

Because of its relatively low molecular weight, continuously manufactured or extruded acrylic sheet cannot be hung from a single edge. A clamping frame should be used for support and to facilitate sheet transfer to the forming station. Do not leave continuously manufactured sheet hanging in the oven after it has reached its forming temperature. The material can soften, deform and fall out of the clamping frame if heated too long. Cell cast sheet, on the other hand, can be hung from a single edge, and is unlikely to fall out of the clamps if heated longer than required. Be sure that temperatures throughtout the oven are uniform, and the clamping frame exerts constant uniform pressure on all sides of the sheet as it becomes soft.

Horizontal heaters
Using horizontal infrared heaters (ceramic elements for instance) instead of hot air ovens is faster and less labor intensive. Horizontal units are also more flexible because either the heaters or the sheet and clamping frame can be moved. Working clearances can often be improved by moving the heaters, and systems can be designed to handle custom made blanks.

When designing a horizontal heating system, independently controlled heating zones should be set up to improve control and flexibility.

Thermoforming mahines
Many types and sizes of forming equipment are commercially available. Thermoforming machines are ideal when small to medium volumes of the same shape are being produced. This is because the tooling required for thermoforming is much less expensive than the tooling required for injection molding.

For more information contact Mike at Ultra Acrylics, Inc.

Posters made of single/double printed paper, polyester or vinyl are particularly suitable for use with light diffusing acrylic sheet. Enhanced graphic substrates such as Duratrans improve the light diffusion of color contrast.

Light intensity transmitted through the face of this type of acrylic sheet is governed by parameters such as location, quantity and length of light source. For example, a sign/display panel measuring 24 inches in length by 16 inches in width can be successfully lit by placing only one fluorescent lamp on the longer edge. A larger panel measuring 32 inches by 40 inches can be fully illuminated by placing a fluorescent lamp on each of the opposite edges from the width. The maximum width attainable with an even illumination is about 48 inches; however, with ever-improving technology, greater attainable widths will be possible in the future.

An economic and very effective way to boost lighting from standard fluorescent tubes is to place metalized reflective adhesive tape around the tube to direct the maximum amount of light into the edge of the acrylic sheet. Reflective film can increase lighting efficiency up to 20 percent by preventing light from exiting the panel.

In preparing the sheet for installation, it is very important that the edges remain perfectly flat, as optical defects in the edges will affect the amount of light that the panel will receive. Because some sign makers are only providing a clean saw cut edge, it may be necessary to smooth that edge further. Saw marks, if any, can be successfully removed by scraping the edges or using diamond discs cooled with water. In order to obtain the maximum effect, it is recommended that the sheet edges, where the light enters, be polished with a diamond edge finisher. This will enhance the amount of light entering the sheet panel. It is also important to avoid gluing or bonding any materials to the sheet as this may inhibit its light transmitting properties.

Light diffusing edge-lit acrylic sheet has all the mechanical, thermal, fabrication and weathering properties of standard cell cast acrylic sheet. However, comparing the lighting behavior of this sheet with standard cell cast acrylic clear sheet is not relevant. Clear acrylic sheet will work only as a light guide and prevent the light from diffusing throughout the sheet face of edge-lit. Only light diffusing edge-lit acrylic sheet diffuses light when edge-lit. Following standard procedures for cell cast acrylic sheet, edge-lit acrylic sheet can be thermoformed into a curve to a maximum radius of 20 inches to create original shapes and designs.

Because it is light weight, easy to maintain and aesthetically pleasing, public demand continues to increase as a result of the many positive attributes that light diffusing edge-lit acrylic sheet possesses.

For more information, contact Mike at Ultra Acrylics, Inc.

There is a growing demand in the illuminated signage and point of purchase display markets for light boxes that have thinner profiles. Acrylic manufacturers have addressed the need for a new sign substrate by developing a special acrylic sheet that can be used in such an application. This acrylic incorporates a new type of "light diffusing edge-lit technology" essential for those fabricators and designers looking for a new sign substrate that acts as a light source. It offers the technological advantage where light focused on the edge of the sheet is transmitted and evenly diffused to both faces of the sheet. This property is achieved with the dispersion of very fine particles throughout the acrylic. When light beams hit these particles, each of them works as a miniature light source.

Designers are beginning to use light diffusing edge-lit arylic sheet in many new and original applications such as:
. Illuminated signs for airports, movie theaters, department stores, banks and casinos.
. Display panels/menu boards for restaurants.
. Information/directory panels for railways, subways, malls, shopping centers, hotels and
buildings.
. Double-sided window shop displays.

One of the main development market sectors of light diffusing edge-lit acrylic sheet is poster/light boxes. Edge-lit acrylic improves the look of illuminated applications by eliminating bulky display boxes and replacing them with slimmer, lighter, more economical thin profile designs. Fluorescent tubes are concealed in the side profiles allowing the frames to be extremely slim.

This type of sheet is specifically designed for either single or double-sided light boxes.

Single-sided light boxes require the following materials: light diffusing edge-lit acrylic sheet, white backing material and a clear protection sheet. Posters need to be placed between the sheet and clear protective layer.

In a double-sided light box, the poster substrates are located on each face of the sheet. In this case, the white backing material should not be used. Each side of the sheet should have the poster and a clear protective sheet over it.

For more information, contact Mike at Ultra Acrylics, Inc.

When buying acrylics, remember that transparency, gloss and dimensional shape of acrylics are virtually unaffected by years of exposure to the elements, salt spray or corrosive atmospheres. These materials withstand exposure to light from fluorescsent lamps without darkening or deteriorating. They ultimately discolor, however, when exposed to high-intensity UV emission from light below 265 nm. Special formulations resist UV emission from light sources such as mercury-vapor and sodium-vapor lamps.

Colorants can be added to produce a full spectrum of transparent, translucent or opaque colors. Most colors can be formulated to give long-term outdoor durability. Clear acrylics are normally formulated to stop the ultraviolet radiations below 370 nm wavelength.

Mechanical properties of acrylics are high for relatively shorterm loading. High stresses can be sustained safely for short periods, but for long-term service, tensile stresses must be limited to 1,500 psi to avoid crazing or surface cracking.

Acrylic plastics are among the most scratch resistant of all thermoplastics. Toughness of acrylic sheet, as measured by resistance to crack propagation, can be improved by inducing molecular orientation during forming. Jet aircraft cabin windows, for example, are made from oriented acrylic sheet.

Special ultraviolet-absorbing grades are used for document preservation in museums and for various photographic applications. Specially formulated acrylic sheet is available for deeply formed components such as tub and shower units which are subsequently backed with glass-fiber reinforced polyester.

For more information, contact Mike at Ultra Acrylic's, Inc.

Virtually unbreakable, high optical quality Lexan polycarbonate (PC) sheet materials from Ultra Acrylics are often a top choice. Lexan polycarbonate sheet combines cryltal clear transparency with value-added performance that features light weight, the outstanding ripple, distortion, and optical defect characteristics. Extruded lexon sheet has one of the tightest measurable specifications with regard to black specks, inclusions, bubbles, lints & fibers, distortion and ripple. This high-tech optical quality sheet product, with highly specialized properties, is an excellent candidate to help answer the specific needs of a variety of structures.

For more information, contact Mike at Ultra Acrylics, Inc.

Acrylic thermoplastics (PMMA) are products of polymerization of acrylic esters. The materials are available in cast sheet, continuous cast and extruded sheet, film and a number of small pellets for injection molding and extrusion. Tubes and rods can also be cast or extruded.

Cell-cast sheet is produced in a variety of sizes and thicknesses. The largest sheets available are 120'' x 144''. Thicknesses range from 0.030'' to 4.25''. Continuous cast material is supplied as flat sheet and in coils in lengths to 600' and widths to 110''. Maximum thickness is 1/2''. Acrylic sheet cast in the continuous process (between stainless steel belts) is more uniform in thickness than cell-cast sheet. Cell-cast sheet, on the other hand, which is cast between glass plates, has superior optical properties and surface qualities. Also, cell-cast sheet is offered in a greater variety of colors and compositions. Cast acrylic sheet is supplied in general-purpose grades and in ultraviolet absorbing, mirrored and superthermoformable sheet grades.

All cast acrylic grades are strong, stable, weather resistant and thermoformable. Sheets are also available in transparent, translucent and opaque colors, and in a variety of surface textures.

Extruded sheet is produced by forcing acrylic pellets through a conventional screw extruder. The acrylic is melted and pushed through a sheet die in a continuous process allowing for a variety of widths and lengths within practical or economical limits.

For more information, contact Mike at Ultra Acrylics, Inc.

Acrylics properties
Acrylic plastics are known for their attractive, glossy surfaces, in practically any color. The problem is that in large, three-dimensional parts, acrylic moldings are not rigid enough for some requirements. One answer to the problem is provided by a process called "rigidizing." Rigidizing marries a thin thermoformed acrylic shell to a strong underlayer of glass-reinforced polyester. Adhesion is excellent and the results are being seen in successful applications such as tops for vans and other RVS.

The light weight and toughness of clear plastic sheet qualifies it for many jobs formerly held by glass. Materials in this category include acrylics, cellulosics, polyarylates, polysulfones and polycarbonates. Despite the durability of these materials, however, their surfaces are softer than those of glass, making them more suseptible to hazing by surface abrasion and to damage by scratching. But progress is being made, and more abrasion-resistant materials and surface treatments are being developed.

For more information, contact Mike at Ultra Acrylics, Inc.

Continuously cast acrylic is produced from monomer. This type of acrylic is polymerized between two stainless steel belts. The belts are typically 108 to 110 inches wide. Each belt has a seam or weld line at 54 or 55 inches. The 108-inch wide belt is actually made up of two belts which are welded together. The seam in the belt causes a slight distortion in the sheets when viewed at acute angles. Continuous cast acrylic sheet sizes are limited in width by the width of the belts that are used to polymerize the sheets. Continuous cast acrylic is produced in thickness ranging from .100/2.5 mm through .471/12 mm thick. Continuous cast acrylic generally has a higher molecular weight than continuously processed or extruded acrylic sheet. It forms well, it has good thickness tolerances and it can be produced on reels. Continuous cast acrylic is generally considered inferior to cell cast acrylic for optical applications.

Continuously processed acrylic sheet is extruded from polymer. Acrylic polymer or acrylic pellets are melted in a hopper and forced through an extrusion die. As the sheet comes out of the die, it passes through a stack of highly polished drums called a roll stack. The roll stack is used to polish the sheet and control the thickness. Some customers prefer a specific manufacturer of continuously processed acrylic sheet. The sheets differ primarily due to the optical brighteners that the manufacturer uses to control edge color, the quality of the extruder that is used to manufacture the sheet and the downsteam equipment that is used in the final stages of polymerization. Most manufacturers have begun to produce continuously processed acrylic sheet with a higher molecular weight. The molecular weight of this material is similar to continuous cast acrylic sheet.

Continuously processed acrylic sheet is the most commonly sold acrylic sheet in the U.S. market. It has excellent thickness tolerances, shorter cycle times for solvent cementing, bending and forming when compared to cell cast acrylic sheet. The width of the sheet is limited by the width of the extruder, but any length can be achieved. The optical quality of continuously processed acrylic sheet is generally considered to be inferior to cell cast acrylic sheet, but is considered acceptable for most applications, including the framing lens for fine arts. It is also used as the main substrate for the production of acrylic mirror. The production minimums for colors are generally higher than batch minimums for cell cast acrylic.

For more information, contact Mike at Ultra Acrylics, Inc.

It is important to understand your customers' needs, concerns, the application, their equipment and their shops' capabilities. This will determine what type of acrylic will work best for their application.

For more information, contact Mike at Ultra Acrylics, Inc.

Continuously processed acrylic sheet is extruded from polymer. Acrylic polymer or acrylic pellets are melted in a hopper and forced through and extrusion die. As the sheet comes out of the die, it passes through a stack of highly polished drums called a roll stack.

Contact Mike at Ultra Acrylics for more information.

Acrylic sheet can easily be saw cut, drilled, bent, free formed, vacuum formed, routed into shapes, solvent cemented, silk screened, painted, etched, flame polished and buff polished.

For more information, contact Mike at Ultra Acrylics, Inc.

Cast arylic or specifically cell cast acrylic sheet is manufactured in batch quanities. Monomer (methyl methacrylate) is poured between two plates of tempered glass, commonly known as a cell, and polymerized in hot water baths or in an oven. Cell cast acrylic is preferred for small batch color runs and optical applications because it has a higher molecular weight, is more chemically resistant to aromatic solvents, exhibits more symmetry when it is free formed into domes, and also because it can be produced in thicker gauges. Cell cast acrylic is limited in its sheet size by the size of the glass used to cast it. Thickness tolerances can vary widely. Class C tolerances for .236/6mm thick cast acrylic are +.303 to .050 inches typically.

For more information, contact Mike at Ultra Acrylics, Inc.

There are three basic types of acrylic: cell cast, continuous cast and continuously processed or extruded acrylic sheet. Understanding how the sheets are produced, how their physical properties differ and what the advantages and disadvantages are for each type of material will help you choose the proper type of acrylic best suited for your customer's application. All domestic manufacturers produce acrylic sheets which are UV stabilized and suitable for outdoor use. (Some exotic colors are produced from dyes or pigments that not intended for outdoor use.)

For more information, contact Mike at Ultra Acrylics, Inc.

Each fabrication process adds stress to the sheet. Some fabricators have very sophisticated production facilities, others do not. If the fabricator cuts acrylic sheet with a sophisticated panel saw, the amount of stress that is added to sheet is minimal. If he cuts the sheet with a hand-held circular saw that has a dull blade, there will be major difference in the amount of stress that is added to the sheet. If your customer is more archaic in the way he processes his sheet, cast will be more resistant to crazing. If your customer has a highly automated shop with CNC cutting, routing and polishing equipment, he should be able to fabricate continuously processed acrylic sheet very efficiently. If he uses some of the highter molecular weight acrylics, he will be able to perform more processes in a shorter period of time. Since stress in acrylic can cause crazing, it should be avoided as much as possible. If your customer has sharp tooling, uses the proper cycle times and feed rates for cutting, bonding, polishing and forming, the amount of stress that is added to the sheet is minimized.

For more information, contact Mike at Ultra Acrylics, Inc.

Coiled resistance wire may be substituted for straight wire as a heating element Coiled wire must be supported, however. It is also difficult to position the coils evenly. This causes temperatures across the sheet's width to vary, resulting in uneven stresses and distortion.

Problem-free line bending of acrylic sheet requires the right combination of appropriate equipment and proper procedures. Done correctly, line bending provides strong and visually appealing results, adding shape and form to acrylic-made products, as well as increasing its usefulness in a broad range of applications.

The light weight and toughness of clear plastic sheet qualifies it for many jobs formerly held by glass. Materials in this category include acrylics, cellulosics, polyarylates, polysulfones and polycarbonates. Despite the durability of these materials, however, their surfaces are softer than those of glass, making them more susceptible to hazing by surface abrasion and to damage by scratching. But progress is being made, and more abrasion-resistant materials and surface treatments are being developed.

Acrylic plastics are among the most sratch resistant of a thermoplastics. Toughness of arylic sheet, as measured by resistance to crack propagation, can be improved by inducing molecular orientation during forming. Jet aircraft cabin windows, for example, are made from oriented acrylic sheet.

Ultra Acrylics, Inc. introduces Show Off Cleaner, available in 1 oz., 4 oz., and 1 gallon size.

For more information, contact Mike at Ultra Acrylics, Inc.

Acrylic thermoplastics (PMMA) are products of polymerization of acrylic esters. The materials are available in cast sheet, continuous cast and extruded sheet, film and a number of small pellets for injection molding and extrusion. Tubes and rods can also be cast or extruded.

For more information about our services, contact Mike at Ultra Acrylics, Inc.