ACRYLIC SHEET Fabrication Manual
TABLE OF CONTENTS 3 Introduction 19 Cementing Plexiglas® 3 General Health and Safety Precautions 19 Health and Safety Precautions 3 Concentration Levels and Ventilation Standards 19 General Joining Comments 3 Special Precautions 20 Cementing Plexiglas® Acrylic Sheet to Plexiglas® Acrylic Sheet 3 General Fabrication Considerations 21 Solvent Cements 4 Cutting Plexiglas ® 21 Thickened Cements 4 Health and Safety Precautions 22 Polymerizable Cements 4 Cutting 28 Basic Cementing Techniques 4
INTRODUCTION General Health and Safety Precautions Special Precautions Care must be taken whenever fabricating or thermoforming any thermoplastic, including Plexiglas® acrylic sheet. The heat of thermoforming, cutting, machining, finishing, annealing, or otherwise processing Plexiglas® acrylic sheet may result in the release of vapors or gases, including methyl methacrylate (MMA) monomer. Additionally, cementing Plexiglas® acrylic sheet introduces other vapors related to the formulation of the adhesives.
CUTTING PLEXIGLAS® ACRYLIC SHEET Health and Safety Precautions Circular Blade Saws Cutting Plexiglas® acrylic sheet may cause localized heating, resulting in the release of methyl methacrylate (MMA) monomer vapor, and may also generate some polymer dust. See Concentration Levels and Ventilation Standards, page 3. Any dust produced by the cutting of Plexiglas® acrylic sheet is considered “nuisance” dust. The OSHA PEL/TWA for nuisance dusts is 15 mg/m3 total dust, and 5 mg/m3 respirable dust.
FIGURE 1 Square and Advanced or Triple-Chip-Tooth Style 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.
High-Speed Steel Circular Saw Blade Recommendations Thickness To Be Cut Blade Thickness .030”-.080” .098”-.150” .177”-.354” .472”-.708” .944”-2.000” 1⁄ 16 TA B L E 1 B ”-3⁄32” ”-3⁄8” 3⁄ 1 32”- ⁄8” 1⁄ 8” 1⁄ 5 8”- ⁄32” 3⁄ 32 Type Blade Hollow Ground Hollow Ground Spring Set or Hollow Ground Spring Set or Swaged Spring Set or Swaged Notes: Recommendations are for hand-fed operations (3"-4"/sec.).
FIGURE 2 Cutting Board for PLEXIGLAS® Acrylic Sheet Small wood blocks may be lightly nailed to the top of the cutting board to cut other than rectangular shapes. 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.
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.
Scroll Saws 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.
Routing Plexiglas® Acrylic Sheet Portable routers are used for trimming the edges of flat or formed parts, particularly when the part is too large or it is too awkward to use a band saw or stationary router. Routers should have a minimum no-load spindle speed of 10,000 rpm – higher speeds are more desirable. Double, 5 1 straight-fluted cutters ⁄16 inches to ⁄2 inch in diameter will produce the smoothest cut at this speed.
MACHINING PLEXIGLAS® ACRYLIC SHEET Health and Safety Precautions Machining Plexiglas® acrylic sheet should not result in harmful concentrations of vapors provided that adequate ventilation is employed. To insure this, both general and local exhaust ventilation are recommended. See Concentration Levels and Ventilation Standards, page 3.
Routing and Shaping Woodworking shapers (also called table routers) and overhead or portable routers are used in edge-finishing operations and for cutting flat or formed Plexiglas® acrylic sheet parts to size. For edging small parts, the table router is convenient; portable routers are useful whenever the acrylic part is too large or awkward to bring to the machine. Routers should have a minimum no-load spindle speed of 10,000 rpm.
FIGURE 4A Deflanging Cuts with Veneer Saw Blades FIGURE 4B Close Tolerance Deflanging Cuts with Veneer Saw PORTABLE ROUTER Small Boss Narrow Flanged Parts TABLE ROUTER (Wood Shaper) Close Tolerance Fixture Large Boss Wide Flanged Parts PORTABLE ROUTER TABLE ROUTER (Wood Shaper) Close Tolerance PORTABLE ROUTER Small Boss Wide Flanged Parts Fixture FIGURE 5A FIGURE 5B Flange Trimming with Table Saw Alternative Flange Trimming Tuffak® Polycarbonate Window CLAMP Guide should ride on return rather
FIGURE 6 Drilling Flange Trimming Table Router When drilling Plexiglas® acrylic sheet, best results will be obtained using standard twist drills that have been modified, as described below. High-speed steel drills should be used. WITH TEMPLATE Specially ground drills for Plexiglas® acrylic sheet are available from Authorized Plastic Products Distributors. Fixture Modification of Drills: Instructions for Sharpening Bits Template TABLE ROUTER (Wood Shaper) Chuck the bit in an electric drill.
FIGURE 8A FIGURE 8C Drill Modification – 60˚ Tip Angle Drill Modification – Clearance Behind Cutting Edges Grinding Wheel Note angle Both wheel and drill are rotating. 60° GENERAL DRILL SPEEDS Diameter .060" .125" .187" .250" .312" .375" .437" .500" .750" 1.000" Wood or Metal Bushing Chuck Speed-RPM 3000-4500 1500-4500 1500-4500 1800-2000 1500-2000 1500-2000 1000-1500 800-1000 500-800 500 FEED RATE OF .015"-.
Drilling Techniques Whenever holes in Plexiglas® acrylic sheet penetrate the stock, standard twist drills should be modified, as previously described, up to a 1.00 inch diameter. A 60° tip angle allows the drill to emerge from the second surface without fracturing the sheet. When holes are to be drilled that do not penetrate the Plexiglas® acrylic sheet, the rake and lip clearance angles of the drill should be modified as described, but tip angles larger than 60° clear chips from the hole better.
FINISHING PLEXIGLAS® ACRYLIC SHEET Plexiglas® acrylic sheet should be handled carefully to avoid scratching its surface. It is easier to avoid scratches than to remove them. Scratched surfaces can be restored to a good finish by a process of polishing and/or sanding. Sawed edges and machined surfaces can also be polished to a high gloss. Where power-operated polishing equipment is not available, it is possible to hand-polish minor scratches from the surface of the sheet.
Polishing Drilled Holes A properly drilled hole has a smooth semi-matte finish that can be brought to a high polish. A wood or metal rod approximately 1⁄ 8 inch smaller in diameter than the drilled hole is split to a depth 1 equal to the depth of the hole plus ⁄2 inch and mounted in a drill press. If the inner surface of the hole is rough, steel wool or strips of emery cloth or sandpaper are wound around the rod and gripped in the slot.
CEMENTING PLEXIGLAS® ACRYLIC SHEET General Health and Safety Precautions Care must be taken whenever heating any thermoplastic, including Solarkote® capped film. When fabricating, use good practices consistent with any operation that uses high speed saw blades, bits or drills. The use of machine guards and hold down bars is recommended whenever possible. To avoid burns during thermoforming, the use of thermally protective gloves and sleeves is recommended.
Stress may be introduced into a part during the thermoforming operation, or during fabrication operations such as machining or polishing. Stress may sometimes be held to a minimum by altering the processing conditions when forming parts, and by using sharp tools of the recommended types when cutting or machining. For machining instructions, see page 11. The possibility of crazing may be greatly reduced by minimizing internal stresses by annealing the parts before cementing.
Solvent Cements Thickened Cements Depending on technique, cast acrylic surfaces to be joined are softened, and in some cases swollen into a cushion, by contact with commercially available solvent cements. Plexiglas® MC acrylic sheet should not be soaked in cement as long as Plexiglas® G acrylic sheet, for it tends to dissolve rather than swell into a cushion.
Polymerizable Cements Polymerizable cements are those in which a catalyst is added to an already thick monomer/polymer syrup to promote rapid hardening. Cements PS-30 and Weld-On 40 or 42 are polymerizable cements of this type. They are suitable for cementing all types of Plexiglas® acrylic sheet. At room temperature, the cements harden (polymerize) in the container in about 45 minutes after mixing the components. They will harden more rapidly at higher temperatures.
The gap joint technique should only be used with colorless Plexiglas® acrylic sheet, or in cases in which joints will be hidden, or when light leaks are not a problem. Inconspicuous joints in colored sheet are difficult, if not impossible, to achieve. Adding acrylic sign paints to Component A can be effective at times, but may adversely affect the joint strength. Cement forms or dams may be made with masking tape as long as the adhesive surface does not contact the cement.
FIGURE 9A FIGURE 9B Open ”V” Joint Polymerizable Cementing Open ”V” Angle Joint Technique 1. Prepare Parts for Cementing. 1. Position Parts for Cementing. About 3⁄ 32" Scrape edges Position pieces with small clearance not greater than .015". This clearance must be kept to prevent a dry notch. Paper, small wire, etc., may be used to position the parts prior to clamping. Remove spacers before cementing.
FIGURE 9C FIGURE 10 Open ”V” Angle Construction Variations Box Construction Using Polymerizable Cement Configuration of joints to be subjected to internal pressure such as by air or water. 1. Cement Sides Together. Pieces clamped to fixture for cementing. 0.250" or thinner Make joint as shown in Figure 9B. Cementing Fixture Second fillet Pour one joint at a time. Support Material thicker than 0.250" 0.250" Cementing Fixtures Various Angle Configurations Pour two joints at same time. 2.
FIGURE 11A FIGURE 11B Removal of Cement Bead and Lip-Open “V” Angle Joint Removal of Cement Bead and Lip–Open “V” Angle Joint Operation of guide. Direction of feed. Fixture guide Rough cuts to remove excess material. Cutter Wheel optional 3 ⁄8" double straight flute router cutter. Reducing angle reduces the lip left on the part. Air blast is required to keep guide clear of chips. NOTE: Ball bearing tip cutter may be used instead of guide.
FIGURE 13 FIGURE 14 Thick Section Butt Joint Techniques Technique for Inside Joints Fixture 3M #670 tape cut after cement is cured Cementing technique for inside joints that cannot be routed and finished. Outside open V-joint which may be routed Fill level will shrink when cured 3M #670 Tape (Reinforced cellophane) Cellophane tape (try tape to see if cement cures against adhesives) Processing Steps 1⁄ 16" 1. Use PS-30 or Weld-On 40 or 42. 2. Cut must be sharp (sawn or routed).
FIGURE 16 Basic Cementing Techniques Soak or Drip Cementing Techniques The two basic cementing techniques using unthickened cements are: 1. The capillary action method. 2. The soak or dip joint method. The soak or dip joint method is not recommended for Plexiglas® MC acrylic sheet, because it dissolves rather than softens the sheet. 1. Machine pieces with sharp tools so the parts to be joined fit without forcing or flexing. Do not polish edges to be cemented. Apply masking if required. 2.
Cementing Plexiglas® Acrylic Sheet to Other Materials Before specifying cementing for attachment of Plexiglas® acrylic sheet to dissimilar materials, the possibilities of mechanical attachment should be carefully evaluated. Properly designed mechanical attachment overcomes the difficulties often encountered with cementing. For some applications, pressuresensitive, double-faced tape may be suitable for joining Plexiglas® acrylic sheet to other materials.
ANNEALING PLEXIGLAS® ACRYLIC SHEET Health and Safety Precautions Annealing Plexiglas® acrylic sheet should not result in the release of harmful concentrations of vapors or gases under the annealing conditions recommended in this manual. However, Plexiglas® acrylic sheet may release high concentrations of vapors and monomers if heated to temperatures in excess of 350°F without adequate ventilation.
Cooling Times for Plexiglas® Acrylic Sheet Parts (All Formulations) Time (Hours) to Cool Plexiglas® Acrylic Sheet Parts from the Indicated Temperature to 120°F Maximum Thickness (Inches) 0.060 to 0.177 0.236 to 0.354 0.472 to 0.708 0.944 1.500 to 1.750 2.
MAINTENANCE OF PLEXIGLAS® ACRYLIC SHEET Dusting Always dampdust Plexiglas® acrylic sheet. For best results, mix a solution of one teaspoon of dishwashing liquid, or other mild soap or detergent, and a pint of water; apply this solution to Plexiglas® acrylic sheet with an atomizer or spray bottle and wipe until dry and glossy smooth with a clean cotton flannel or jersey cloth. Do not use dishwashing liquid containing hand lotions, such as aloe or lanolin.
STORAGE AND HANDLING Plexiglas® acrylic sheet is shipped in corrugated fiber cartons or in wood-reinforced fiberboard boxes having a gross weight of 400 pounds or more or on pallets weighing approximately 2,000 pounds. All Plexiglas® G and MC acrylic sheets are boxed in standard packages. The number of sheets in each package depends on the size and thickness of the sheets.
The masking paper used on Plexiglas® acrylic sheet is not water repellent. If masked Plexiglas® acrylic sheet is soaked with water, a white residue may be left on the material when the masking paper is removed. To avoid this, store masked sheet where it cannot come into contact with water. If a residue is deposited on the Plexiglas® acrylic sheet, it may be removed by wiping the surface gently with a clean, soft, damp cloth and drying it with a soft flannel cloth.
Protective Coatings Masking compounds are available that can be sprayed on the Plexiglas® acrylic sheet and later peeled off. These are especially useful when remasking formed parts. The spray masking compounds should not have a harmful chemical action on the Plexiglas® acrylic sheet. Some masking compounds may be used indoors for periods as long as twelve months. In general, no masking compound should be used on parts that will be stored outdoors.
Altuglas International Sales Offices For more information, call your local Altuglas International sales office or Altuglas International headquarters. Americas Headquarters Altuglas International Arkema Inc. 2000 Market Street Philadelphia, PA 19103 USA Tel.: 800-523-1532 215-419-7000 Fax: 215-419-5511 Detroit Office Altuglas International Arkema Inc. 1050 S. Milford Road Suite 102 Highland, MI 48357 USA Tel.: 248-887-2245 Fax: 248-887-0452 Chicago Office Altuglas International Arkema Inc. 2300 N.
