For all of the fabrication
information, please download the complete brochure. Authorized Plexiglass Fabrication Brochure Download Also - a great article written by the makers of Plexiglas - Sawing Acrylic Sheet - as published in the IAPD Magazine
Plexiglass acrylic sheet may be cut by sawing or routing with power equipment saws or by scribing and breaking. Scribing is limited to straight cuts in thin pieces of Plexiglas® acrylic sheet, 0.236 inches or less, and is practical for use by the craftsman who has no power tools when cutting small quantities of sheet material. Sawing and routing may be used for straight and curved cuts on any thickness of material. Keep masking intact during fabrication to protect the surfaces and provide lubrication. Plexiglass acrylic sheet is a combustible thermoplastic material. Observe fire precautions appropriate for comparable forms of wood and paper products.
The kind of cutting to be done on Plexiglas® acrylic sheet should determine the type of sawing equipment to be used. Circular blade saws are limited to straight cuts; scroll and sabre saws for rough cutting small-radius curves in thin Plexiglas® acrylic sheet; band saws for rough cutting larger-radius curves or for making rough straight cuts in thick Plexiglass acrylic sheet. Routers and woodworking shapers are used for cutting and trimming the edges of flat and formed parts of any configuration and provide the best overall fabricated edge.
Circular Blade Saws
There are several types of circular blade saws suitable for cutting Plexiglas® acrylic sheet. Table saws vary in size from small, light-duty models to large, heavy-production models and are generally used for cutting Plexiglas® acrylic sheet to close dimensions. The size of table saw most commonly used is a medium-duty model with an arbor of 5/8 to 1 inch diameter and powered by a 1.5 to 5hp motor. Special fixtures are often used to hold the work steady for accurate cutting. Radial saws and swing saws move while the work is held stationary and are generally used to make angle cuts and cross cuts in narrow pieces of Plexiglas® acrylic sheet. The length of cut of a radial saw is limited to about 24 inches. Panel saws are of two types. The first has the saw blade and motor mounted above the material to be cut. The work is placed on the table against a fence and the saw is fed through the work. The second type has the saw blade and motor mounted below the material to be cut with a combination saw guard and hold-down bar. The blade extends through the table high enough to cut through the material. This type of panel saw is usually set so that the saw blade must be retracted before the saw guard and hold-down bar can be released.
These saws are available with either horizontal or vertical tables. The vertical saws offer advantages in that less floor space is needed; large sheets of Plexiglas® acrylic sheet may be placed on the saw more easily; and there is less danger of scratching unmasked sheets of Plexiglas® acrylic sheet. Circular saws should have motors with sufficient power. A 10-inch-diameter saw should be powered by approximately a 2 hp motor; a 14-inch-diameter saw, by approximately a 5 hp motor. Blades are normally driven direct and run at a motor speed of 3,450 rpm. Saws should be equipped with heavy-duty, production type fences, be well-guarded and have sawdust-removal systems. Kick-plate switches and electromechanical or frictionless electronic motor brakes should be provided for safety purposes. Programmable horizontal and vertical panel saws with a movable fence can be used to cut Plexiglas® acrylic sheet to size in high-production operations. Saw blades should be equipped with carbide-tipped teeth of the triple-chip style. This tooth style is also called square and advance and is illustrated in Figure 1. Triple-chip-style teeth are designed so that alternate teeth start and finish the cut. The slight chamfering of the square tooth corners minimizes chipping. Carbide-tipped blades give cuts of superior quality, cut faster, and require fewer blade changes because of dulling. However, such blades must be returned to the factory for resharpening.
For best results with Plexiglas® MC acrylic sheet, circular saw blades should be the largest diameter possible and contain 60 carbide-tipped teeth with a triple-chip-tooth design. Teeth should be shaped with a 5° to 10° positive rake angle and have sharp cutting edges with adequate clearance. To obtain the optimum cut from carbide-tipped blades, the saw and stabilizer discs must fit the arbor closely with a clearance of about 0.001 inch, and must run true. Loose bearings, bent arbors, or misaligned or burred stabilizers will vibrate and cause cuts of poor quality and shorten blade life. For maximum service life, carbide-tipped blades used for cutting Plexiglas® acrylic sheet should not be used to cut any dissimilar materials. To minimize blade wobble, which results in the generation of heat and possible melting of the plastic, the use of a single- or double-mounted, precision-ground, hardened-steel stiffener with a diameter 4 inches less than the saw blade and a blade with additional radial/side tooth clearance is highly recommended. Table1A lists specifics on the recommended carbide-tipped circular saw blades. Where the quantity of the Plexiglas® acrylic sheet to be cut does not warrant the purchase of carbide- tipped blades, high-speed steel blades designed to cut Plexiglas® acrylic sheet may be used instead. These blades are made of alloy steel and are tempered to permit filing. The teeth should have a positive rake angle of 0° to 10° and should be of uniform height and shape. When cutting 0.150 inches or thinner sheet, the blade should be hollow ground rather than set. Teeth of uneven height will cause chipping of the Plexiglas® acrylic sheet and will place undue cutting strains on a few teeth. This may cause the saw blade to crack. The saw blades should be machine filed or ground. For cutting very small quantities of Plexiglas® acrylic sheet, standard hollow ground, fine-tooth blades used for cross cutting wood or ply-tooth blades may be used. Table 1B lists the recommended high-speed steel circular saw blade information for cutting various thicknesses of Plexiglas® acrylic sheet.
Circular Blade Saw Operation
To minimize both chipping and overheating tendencies, circular saw blades should protrude approximately 1⁄2 inch more than the thickness of the Plexiglas® acrylic sheet. The work must be held firmly against the fence, which must be parallel to the saw blade. Several sheets of Plexiglas® acrylic sheet can be cut at one time by stacking one on top of another. Suitably designed holding fixtures must be used when stacks of sheets are to be cut to close tolerances. When unmasked sheets of Plexiglas® acrylic sheet are cut, it is necessary to take care to avoid scratching the surface of the sheet. Working surfaces should be covered with some soft material such as medium-density felt. The surface should be kept free of dirt and chips. Sawdust and chips remaining on the surface of the Plexiglas® acrylic sheet after cutting may be removed by blowing with compressed air. Wiping the surface of the sheet with a damp cloth will remove sawdust that clings to the material because of static electricity. The damp cloth will also dissipate the static charge.
When cutting Plexiglas® acrylic sheet on a table saw, a cutting board should be used for cutting stacked/clamped material or making a cut not parallel to another edge (angle cut). Figure 2 shows a suitable cutting board. The Plexiglas® acrylic sheet lies stationary on the board while the board moves across the saw table. When cutting stacked Plexiglas® acrylic sheet to final dimensions with a panel saw, hold-down clamps should be used when feasible. This procedure will also help reduce chipping. The manual feed rate should be 3 to 4 inches per second (15 to 20 feet per minute) and should be uniform. The saw should be allowed to cut freely while maintaining the rated speed of the motor. Coolants are not required for most sawing operations, although, if exceptionally smooth cuts in thick sheet are needed, a fine spray mist of detergent in water or 10 percent soluble oil, compatible with Plexiglas® acrylic sheet, in water can be directed against the saw blade. For Plexiglas® MC acrylic sheet, circular saws should operate at speeds of approximately 3,450 rpm and the material feed rate should be about 4 inches per second. The saw blade should be set at a height only slightly greater than the thickness of the material being cut, to ensure a smooth, chip-free edge on either single or stacked cutting of sheets. Elimination of gumming or welding of the sheets during stack cutting can be reduced by applying compressed air or an approved liquid coolant to the saw blade and material to reduce heat buildup. Clamp the stack if possible. Make sure that the saw arbor runs true and the blade plate is flat to prevent rubbing. Some fabricators with special cutting problems have found it helpful to purchase a circular saw blade with additional clearance behind the teeth, such as the “no melt” blade from Forrest Manufacturing Co., Inc., in Clifton, NJ (1-800-733-7111). With this blade, increase the feed rate up to 6 inches/second, and increase the height of blade above the plastic sheet, short of developing chipping of the sheet. Stabilizing discs are recommended to minimize saw blades from wobbling and developing heat. Table 2 (shown on page 6) summarizes some circular saw cutting problems, with some possible corrections.
Band saws should be used when curves are cut in flat sheets or when formed parts are rough trimmed. They are also used for making straight cuts in thick pieces of Plexiglas® acrylic sheet. For production work, large saws with a 30- to 36-inch throat are best, although smaller band saws are satisfactory for small work. The blade should run at a speed of 2,300 to 7,500 feet per minute. As a general rule, as the thickness of the Plexiglas® acrylic sheet increases, the number of teeth per inch on the blade should decrease. See Table 3 for recommendations. Metal cutting blades and, in particular, bimetallic blades stay sharp longer than blades designed for cutting wood and are better for use on Plexiglas® acrylic sheet. They are supplied by several manufacturers in 100-ft. coils and can be cut to the proper length and brazed or welded. The weld must be annealed and dressed. Blade thickness, width, and the number and type of teeth depend on the size of the band saw, the thickness of the material to be cut, and the minimum radius to be cut. Band saw blades of 0.250-inch to 0.375-inch width should be used for cutting curves; blades of 0.50-inch to 0.75-inch widths should be used for straight ripping or cutting large-radius curves. The diameter of the band saw wheels will determine the maximum thickness of the blade. The thickness of the blade increases as the diameter of the wheels increases. Special band saw blades, called “skip tooth” or “buttress” blades, have been developed for soft materials such as plastics and are available with 2, 3, 4, or 6 teeth per inch. These blades should be used when cutting thicknesses greater than 0.472 inches. These blades are hardened and will retain their sharpness for long periods when used only for cutting Plexiglas® acrylic sheet. Variable pitch (number of teeth per inch) blades work well in reducing chipping when cutting sheet 0.472 inches thick or less.
Band Saw Operation
The tension on the saw blade should be just enough to prevent slipping on the wheels, but not enough to stretch the blade and cause misalignment. The guide rolls or blocks should be set so they just miss the teeth but support the rest of the blade width. They should be set so that their rotation can be stopped with pressure from the thumb and forefinger when the saw is turned by hand. The backup roll should be adjusted so that it does not turn when the saw is idling, but will provide support while the saw is cutting. When cutting formed sections, it may be necessary to raise the upper guide. When this is done, extra care is necessary to insure proper alignment. For added safety, the upper guide should be as low as possible (within 1⁄2 inch of the Plexiglas® acrylic sheet). The action of the saw carries sawdust from the Plexiglas® acrylic sheet and the masking paper onto the wheels. The dust builds up on the wheels and may cause the blade to run off. Therefore, this accumulation of dust must be removed. Stiff-bristle brushes can be placed so that they touch the tires and clean them as they revolve. The brushes should be held with a light spring tension so that they will make contact, yet not cause excessive wear on the tires. Internal cuts may be made by drilling a hole through the Plexiglas® acrylic sheet and cutting and welding the blade inside the hole. Once the internal cut is completed, the blade must be recut, removed from the hole, and rewelded. This technique may be useful for special jobs but is too time-consuming for production use. When cutting unmasked Plexiglas® acrylic sheet on a band saw, special care must be taken to prevent scratching. The saw table must be kept clean and should be free of nicks or burrs.
Kraft paper or cardboard should be placed on the table under the unmasked sheet. Tape or rubber cement can be used to hold the paper and the Plexiglas® acrylic sheet together to ensure that both will move through the saw together. When trimming flanges on formed parts, the flange will slide on the saw table so any scratching will not be objectionable for most applications.
For other curved work, a piece of wood about 1⁄2-inch thick by 1.0 inch wide can be run partially through the saw and clamped to the saw table at the ends. The main portion of the acrylic part will be raised slightly above the saw table, while the kerf is supported by the wood strip. For Plexiglas® MC acrylic sheet, band saw blades should be of the edge-hardened metal-cutting type with raker set or broach-style teeth. Blades should have 10 to 14 teeth per inch. Speeds should be between 2,300 and 5,000 feet per minute. In general, the thicker the stack of material, the slower the blade speed should be to avoid overheating. Blade speed and material feed and thickness should be such that each saw tooth cuts a clean chip. The welded joint of the blade should be smooth and carefully aligned to prevent chipping or cracking of the material during the cutting operation. A band saw cut should not be considered a finished edge and, if not a rough cut, should be further finished by scraping.
Scroll saws may be used for cutting sharp radii and closed holes in thin pieces of Plexiglas® acrylic sheet, but are less suitable for cutting thick sections or multiple sheets. Because of the short stroke, scroll saw blades do not clear the chips and tend to gum up. When this happens, the plastic softens and welds around the blade. Scroll saws must be used with a light feed and without forcing the work. The teeth should be cleared often. As soon as the blade stops cutting cleanly, it should be backed out, the chips removed, and the sheet cooled. Welding of the plastic behind the blade may be alleviated by using two blades mounted side by side, or by using an air blast to remove chips and cool the Plexiglas® acrylic sheet. A coolant may also be used. Masking material should always be left intact to provide lubrication in addition to protecting the sheet. Blades should be sharp with 10 to 14 teeth to the inch. Hold-downs are necessary to prevent vibration.
Portable saber saws may also be used for making either straight or curved cuts in Plexiglas® acrylic sheet. When using this type saw, however, it is necessary to provide adequate support for the Plexiglas® acrylic sheet, since the vibration caused by the reciprocating action of the saw blade may chip or crack the sheet. Chisel-type sabre saws should be adjusted so that the cutting chisel stroke is about 3⁄16 inches greater than the thickness of the work to be cut. Two thicknesses of corrugated fiberboard should be placed on the working surface under the Plexiglas® acrylic sheet. The stroke of the chisel should clear the upper surface of the sheet by about 1⁄16 inch and penetrate into the corrugated fiberboard about 1⁄8 inch, thus driving the plastic chips into the board. The blade should be the same type used for scroll saws.
Veneer saws are small circular saws mounted on arbors and powered by high-speed electric or air motors. They are available as stationary or portable models. The saw blades are made in 3-inch and 4-inch diameters with several teeth per inch and have considerable set. They should be driven at 10,000 to 15,000 rpm to give a surface speed of 8,000 to 15,000 feet per minute. Veneer saws cannot be easily guarded and must be used with great care. Carbide-tipped blades should not be used unless designated for high-speed operations. Portable veneer saws are most often used to trim large formed parts of Plexiglas® acrylic sheet held in trimming fixtures. (See Machining Plexiglas® Acrylic Sheet, page 11.) Stationary veneer saws can be used in woodworking shapers or routers for trimming the flanges of compound formed parts when the flange is on one plane. The height of the saw is adjusted to the proper distance above the table and the work is moved past the revolving blade.
A hole saw is a tubular tool with teeth filed on the lower edge of the tube. The teeth are set to cut a groove wider than the thickness of the tool wall. A shaft is fastened to the top of the tube so that it can be mounted in a drill press to drive the saw. Usually a pilot drill and guide are provided to locate and center the hole saw. Knockout holes are located in the top of the saw to allow removal of the discs. Hole saws are stocked in sizes from 5⁄16-inch to 4-inch diameters. Large-diameter hole saws may be made by inserting a piece of band saw blade in a groove machined in a steel disc and holding it with set screws. Coarse-tooth saws should be used for cutting Plexiglas® acrylic sheet. The Plexiglas® acrylic sheet should be cut halfway through, turned over, and the finishing cut made from the other side. When cutting sheet greater than 0.236 inches thick, a detergent/water lubricant and coolant should be used. A saw-cut hole is typically rough and often melted, requiring a post-finishing operation. Better quality holes can be achieved by machining with a router or circle cutter. For more information, please download the complete brochure. Authorized Plexiglass Fabrication Brochure Download
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