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Fabrication

#7 Line BendingThis brief gives advice for:

l Equipment

l Procedures

l Trouble Shooting

l Equipment Suppliers

l Additional Technical Information& Assistance

TECHBRIEF

Equipment

Straight Nichrome Resistance Wire Heater

To bend ACRYLITE® FF acrylic sheet up to 1/8" (3mm)thick, the most commonly used piece of equipment isa straight nichrome wire resistance heater. The unitfunctions similarly to a household electric toaster bypassing electricity through a wire.

You can bend material thicker than 1/8" (3mm) on thisunit, but the material must be flipped over halfway duringthe heating cycle.

In constructing the heater, use plywood for the base.The top surface should be insulation board or aluminumsheet to provide a smooth surface, helping preventmark-off marks on the sheet as a result of contact.Aluminum is selected as the metal alternative becauseit is durable and does not absorb and re-radiate heat.

The heating element is a 17-gauge nichrome (nickel-chrome) wire. Attach the wire to a 120-volt, 20-ampvariable transformer. Provide a spring as shown to keepthe wire under tension. Allow space around the wire forfree air flow to aid heat transfer from the wire to the part.Position the wire so it remains at least 1/8" from thesheet during heating. Ceramic stand-offs are useful insupporting the wire at a consistent height from the base(see last page for source of supply).

CAUTION: An unguarded nichrome wire is a burn/shock hazard. Provide a guard to prevent contactwith the wire.

Modification for Multiple Line Bends

To perform multiple line bends, modify the heater asshown above. Where the wire joins the spring, includean insulation ring. Raise the unit’s base so convectionair from below flows through slots routed in the base asshown.

Coiled Resistance WireCoiled resistance wire can be substituted for straightwire as a heating element. Because coiled wire must besupported and because it is difficult to position the coilsevenly, temperatures across the sheet’s width mayvary, causing uneven stresses and distortion. See thefollowing section under Procedures entitled LineBending with Coiled Resistance Wire.

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Procedures

Be sure to follow the manufacturer’s safetyrecommendations for equipment and materials usedwith ACRYLITE FF sheet.

Bending with a Straight Nichrome Wire Heater

Heat the material until it bends easily. Experience willteach you how long to heat each part. Don’t overheat orlay ACRYLITE FF sheet directly on the heating element- doing so will blister and/or mark the sheet.

Bend the heated part to the desired shape and quicklyplace it in a cooling jig. To retain the bend while you doother work, secure the part in the jig with weights or

clamps. Cooling timenormally equalsheating time.

When line bendingwith only one heatingelement, be sure tobend away from theheated side. Forexample, if thenichrome wire is on thebottom, bend upwards.

Line Bending with Coiled Resistance WireFollow the procedures above for nichrome resistancewire line bending. Flip the piece over while heating toprevent uneven stresses in the bend area.

Long Line BendsWhen a bend line exceeds 24 inches in length, there isa tendency for the part to bow across the bend. This canalso happen when a bend is made close to the edge ofa sheet. To minimize bowing, restrict the width of theheated area or, v-groove the sheet along the desiredbend line, as shown at right. When a line bend exceeds36" in length, the part tends to bend unevenly (slightwave) along the bend due to shrinkage. To minimize thistendency, make the bend perpendicular to the manufac-turing direction. You can tell manufacturing directionwhen the label or masking paper is still attached to thesheet. If there is a label, manufacturing direction is from

To heat sheet thickerthan 1/8" (3mm), usea tubular-rod heater witha heating rod like theheating element of anelectric stove. Powerthe heater with avariable transformer.Place a reflector,preferably of splitaluminum conduit forits good reflectivity,

beneath the rod. For shorter heating cycles, mountheaters above and below the sheet. Use water-cooledsupports to avoid marks on the acrylic.

Radiant Quartz Tube Heaters

Quartz tube heaters are among the most efficientsources of radiant energy. They look like a thinfluorescent light bulb. These units provide capability tobend ACRYLITE FF sheet 1/4" (6mm) thick or greater.The heater consists of a coiled resistance wire housedin a quartz-coated glass tube.

Use a reflector with a quartz tube heater for mostefficient heating. For short heating cycles, mountheaters above and below the sheet. Power theheater(s) with a variable transformer.

Cooling JigsUse a cooling jig likethe one shown at leftto assure that yourbend is at the properangle and to preventthe piece from“springing back” into itsoriginal shape. This isan all-purpose jig for90° bends - you canmodify it to suit thepart. A cooling jigwhich exposes bothsides of the heated

sheet to air will accelerate cooling and reduce stresses.

Tubular Rod Heaters

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top to bottom as you read it. If masking paper is still onthe sheet, manufacturing direction is from top to bottomas you read the words on the masking.

Sharp Line BendsFor sharp line bendswith no deflection, it isa good idea to v-groovethe sheet, as shown atleft. Use a v-rabbetrouter bit or a table saw,making two opposed45° cuts. V-grooving thesheet reduces thematerial cross sectionat the point of bending,reducing stresses and

making bending easier. A wire heater beneath the cutwill help create a sharp angle bend without deflectionsor bowing.

Bending with a Tubular HeaterBend the part as outlined above for a nichrome wireheater. The ACRYLITE FF sheet should be at least halfan inch from the rod to avoid overheating.

Bending with Quartz Tube HeatersBend the part as outlined above for a nichrome wireheater. The ACRYLITE FF sheet should be at least ahalf inch from the tube to avoid overheating.

Gentle BendingBy changing the distance between supports, the workercan increase or decrease the width of the heated area,thus varying the curvature of the bend. In this way, thepart can be bent with a gentle curve instead of a right-angle bend.

Trouble Shooting

Problem Cause SolutionBubbling Overheating Lower heat;or Blistering Reverse or turn

over work.Increase sheet- heater distance

Wet material Pre-dry sheet

Wrinkling Narrow heating Widen heated areaIncrease bend radius (bend radius at least twice sheet thickness)

Bending part Bend away the wrong way from heated side

Mark-off Surface contact Avoid overheating(stray marks Cover jig with felton sheet Reduce areas ofsurface) contact in

cooling jig

Bow Effect Stresses from Use straight heated and nichrome wire unheated to decrease areas width of heated

areaDesign reverse curve in cooling jig

Heat entire part in ovenUse a v-groove bend line

Inherent Bend sheet shrinkage perpendicular in sheet to direction of

manufacture - see foregoing drawing

Equipment and Materials SuppliersThe suppliers listed below offer materials and equipmentsuitable for use with ACRYLITE FF sheet. AuthorizedACRYLITE Sheet Distributors may also offer materialsand equipment.

Variable TransformersSuperior Electric Company383 Middle StreetBristol, CT 06010860-585-4500Fax: 860-589-2136www.superiorelectric.com

Staco Energy Products301 Gaddis Blvd.Dayton, OH 45403937-253-1191Fax: 937-253-1723www.stacoenergy.com

4 1319(7F)-0901-5RA

Nichrom Wire/Strip HeatersPelican Wire Company6266 Taylor RoadNaples, FL 34109-1896941-597-8555Fax: 941-597-9783www.pelicanwire.com

Ceramic Stand-offsCHROMALOXEdwin L. Wiegand DivisionEmerson Electric Co.103 Gamma Drive ExtensionPittsburgh, PA 15238412-967-3800Fax: 412-967-5148www.chromalox.com

EquipmentEdge Finisher Corporation16 Stony Hill RoadBethel, CT 06801203-796-7923Fax: 203-796-7924www.edgefinisher.com

FTM, Inc.6160 Cobblestone RoadPlacerville, CA 95667530-626-1986Fax: 530-642-2602www.thefabricatorssouce.com

C.R. Clarke & Company4407 Vineland Road - Suite D5Orlando, FL 32811800-676-7133www.crclarke.co.uk

Additional Technical Informationand AssistanceWe invite you to visit our TechKnowlogy Centeron www.cyro.com.

Visitors have immediate access to frequently askedquestions, technical concerns, physical properties,processing conditions, fabrication tips, regulatorycompliance information, engineering guidelines, tipsfor troubleshooting, and hundreds of other facts aboutacrylics from one of North America’s leadingmanufacturers of acrylic-basedpolymer and sheet products.

© 2001 CYRO Industries. All Rights Reserved. Printed in USA.

CYRO Industries, Rockaway, New Jersey 07866

Fire PrecautionsACRYLITE FF sheet is a combustible thermoplastic. Precautions should betaken to protect this material from flames and high heat sources. ACRYLITE FFsheet usually burns rapidly to completion if not extinguished. The products ofcombustion, if sufficient air is present, are carbon dioxide and water. However,in many fires sufficient air will not be available and toxic carbon monoxide willbe formed, as it will when other common combustible materials are burned. Weurge good judgement in the use of this versatile material and recommend thatbuilding codes be followed carefully to assure it is used properly.CompatibilityLike other plastic materials, ACRYLITE FF sheet is subject to crazing, crackingor discoloration if brought into contact with incompatible materials. Thesematerials may include cleaners, polishes, adhesives, sealants, gasketing orpackaging materials, cutting emulsions, etc. See the Tech Briefs in this seriesfor more information, or contact your ACRYLITE Sheet Distributor or the CYROTechnical Center for information on a specific product.Important Notice:The information and statements herein are believed to be reliable but are not tobe construed as a warranty or representation for which we assume legalresponsibility. Users should undertake sufficient verification and testing todetermine the suitability for their own particular purpose of any information orproducts referred to herein. NO WARRANTY OF FITNESS FOR PARTICULARPURPOSE IS MADE. Nothing herein is to be taken as permission, inducementor recommendation to practice any patented invention without a license.

Sales OfficesFor the name of your local Authorized Distributor,call 800-631-5384, visit www.cyro.com, or contactthe nearest regional sales office:

Eastern Region100 Enterpise DrivePO Box 5055Rockaway, NJ 07866973-442-6130

South/Central Region101 East Park Blvd.Suite 1039Plano, TX 75074972-424-6830

Western Region3180 Crow Canyon PlaceSuite 240San Ramon, CA 94583925-866-9300

CYRO Canada Inc.6285 Northam DriveSuite 100Mississauga,Ontario L4V 1X5905-677-1388800-268-4743

Technical ServiceFor more information or specific questions aboutyour project, contact CYRO’s Technical ServiceRepresentatives.

CYRO Industries25 Executive Blvd.Orange, CT 06477203-795-6081

CYRO Canada Inc.6285 Northam DriveSuite 100Mississauga,Ontario L4V 1X5905-677-1388800-268-4743

Web site: www.cyro.com