What are the proper procedures for polishing and sanding edges and surfaces, scraping edges, and flame polishing edges of ACRYLITE® acrylic sheet?

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What are the proper procedures for polishing and sanding edges and surfaces, scraping edges, and flame polishing edges of ACRYLITE® acrylic sheet?

Be sure to follow the manufacturer's safety recommendations for equipment and materials used with ACRYLITE® acrylic sheet.

Type of Finish

FINISH METHOD
High Luster Polishing
Satin Sanding Method
Matte Scraping (Edges only)
Medium High Luster Flame Polishing (Edges only)
Matte to Medium Luster Edge Finishing Machines

Preparation

The amount of finishing required to produce a smooth, transparent edge is dependent on the quality of the machined edge. A sharp and properly designed cutting tool will reduce the amount of the finishing work needed. Finishing work is also reduced when a spray coolant is used with the cutting tool to prevent excessive heat build-up

Polishing Edges

Polishing creates the best finished edge but requires the most preparation. A well machined (milled) edge can be polished without prior sanding. However, a saw-cut must be either sanded, run through a jointer, shaper, router or edge-finishing machine, or be hand-scraped before it can be polished. Edge polishing is best done on a stationary polishing head. Use 8" to 14" (200-300 mm) diameter bleached muslin wheels designed with bias strips which give the buffing wheel a pleated appearance. This design runs cooler than a stitched buffing wheel design and will do a faster job.

Edge finish quality depends on the selection of the polishing compounds. The use of a medium cutting compound will give a fairly good finish in one operation. For a high luster finish, it is best to first use a fast cutting compound to remove all sanding marks, and then a high luster compound for the final buffing operation.

Be careful to avoid excessive heat buildup when buffing edges. Too much heat can induce stress into the sheet and eventually cause crazing. To reduce to a minimum the amount of stress, anneal the part, if possible, after all fabrication steps are complete (including polishing).

Polishing Surfaces

If the scratches or machining marks are not too deep, the surface can be polished without prior sanding. Wheels used for surface polishing can be from 6" to 12" (150-300 mm) in diameter, built up to a width of 1 ½" to 2" (38-51 mm). They are made of soft, bleached muslin for the initial polishing operation and of soft flannel for the final finishing.

For the first buffing operation use a medium-coarse polishing compound or a fine compound depending on the depth of the scratches.

When polishing the surface of the sheet, the piece must be kept in motion at all times. Do not use excessive pressure, as softening from over-heating can result.

Sanding Edges

Wet sanding is desired for finishing acrylics. Normally, 180 to 320 grit "wet-or-dry" paper is used along with plenty of water. If done by hand, use a sanding block to keep the edges even. Only light pressure should be applied when grinding with power sanders to minimize frictional heat which can cause gumming from over-heating of the acrylic. Follow "Polishing Surface" procedure for a higher finish.

Sanding Surfaces

A scratched surface should not be sanded unless the imperfections are too deep to be removed by polishing alone. If sanding is required, it is recommended that wet sanding be used. The application of water makes it possible to produce a smoother finish, because fine-grit sandpaper can be used. Without water, this same fine-grit paper would fill up and over heat the acrylic.

For very deep scratches, a 240-grit or 320-grit paper will be coarse enough to start the sanding process. This first step should be followed, after rinsing, by a 400-grit, and then by a 600-grit paper. Be sure to use plenty of water and rinse the sandpaper frequently to keep it from clogging. With power sanders, only light pressure should be applied to reduce friction. Follow "Polishing Surfaces" procedure for a higher finish.

Scraping Edges

Easiest of al finishing techniques is scraping. A scraper can be almost any piece of metal with a sharp, flat edge. Special acrylic scraping tools are available from your ACRYLITE® extruded (FF) acrylic sheet distributor. Whatever tool you use, it must have a sharp, square edge.

Hand scraping is an alternative to sanding for preparing the edges for polishing. Used in conjunction with flame polishing, high luster edges are achieved, but without the smoothness of sanded and polished edges.

Clamp the work vertically. Start at the rear of the edge with the scraper tilted 45° and draw with uniform speed and pressure to the front. A uniform strip should be removed. Follow an edge polishing procedure for a higher finish.

Flame Polishing Edges

Flame polishing should be done with an oxygen-hydrogen welding torch. The flame should be bluish, nearly invisible, approximately 3" (75 mm) long and narrow. Hold the torch at the angle shown and draw the flame along the edge of the sheet. Practice will help you to estimate the speed and distance. If the first pass does not produce a completely polished edge, allow the piece to cool, then try a second pass.

The sudden heating of the sheet when flame polishing induces a high degree of stress into it.

After flame polishing, be sure to anneal the part. This will decrease the amount of stress and reduce or prevent the chance of crazing over time.

Edge Finishing Machines

Commercially available edge finishing machines offer a fast method of obtaining smooth edges without sanding or scraping. Finishes range from smooth edges with slight machining marks to smooth, almost polished edges, depending on the design of the machine and cutting tools used. Machine finished edges are ideal for cementing or flame polishing, but are sharp and require some additional fabrication to make them safe for handling.

Care should be taken to adjust the feed rate to eliminate chipping and melting. Feed rates too fast will result in chipping, while a slow feed rate will result in melting. Edge finishing machines will vary in cutter diameter and rotation speed. In general, machines with larger cutter and rotation speeds will permit faster feed rates without chipping.

Troubleshooting

PROBLEM CAUSE SOLUTION
Dull edge after flame polishing Missed spots Allow to cool and reflame
    Change torch tip size
  Too much heat Increase rate of pass
    Adjust flame size
Char on edge Dirt or contamination Wipe with lint-free, dry cloth prior to flaming
  Wrong fuel Use oxygen/hydrogen mixture
Edge blisters Too much heat See above
  Wet sheet (high moisture content) Pre-dry sheet
Crazing after flame polishing Incompatible cleaner used before or after flaming Use approved cleaner

The suppliers listed below offer materials and equipment suitable for use with ACRYLITE® acrylic sheet. Authorized ACRYLITE® Sheet Distributors may also offer some materials and equipment.

Buffing Equipment  
Delta International
4290 E. Raines Road
Memphis, TN 38118
1-800-223-7278
Fax: 1-800-535-6488
www.deltaportercable.com/
 
Buffing Wheels and Belts  
Edward H. Best & Co.
1076 Washington Street
Hanover, MA 02339
781-826-0291
Fax: 781-826-0294
Jackson Lea Manufacturing Co.
121 Mattatuck Heights
Waterbury CT 06705
203-753-5116
Fax: 203-754-3770
jacksonlea.com
Buffing Compounds  
Jackson Lea Manufacturing Co.
121 Mattatuck Heights
Waterbury CT 06705
203-753-5116
Fax: 203-754-3770
jacksonlea.com
Matchless Metal Polish Co.
801 E. Linden Avenue
Linden, NJ 07036
908-862-7300
Fax: 908-862-7305
matchlessunited.com
Sanding Materials  
3M Company
Abrasives Laboratory
3M Center
St. Paul, MN 55144-1000
1-800-362-3550
651-737-6501
Fax: 651-733-1771
mmm.com
American Woodworking Equipment Distributor
P.O. Box 1756
3635 Martin Farm Road
Suwanee, GA 30024
770-831-9800
Fax : 770-831-7404
awed-machine.com
Edge Finishers, Tools Pre-Flame Cleaner
Edge Finishers, Machine
Edge Finisher Co.
16 Stony Hill Road
Bethel, CT 06801
203-796-7923
Fax: 203-796-7924
edgefinisher.com
 
Post Finishing Cleaners and Polishes  
Anstac 2M Cleaner
Chemical Development Corp
22 Portsmouth Road
Amesbury, MA 01913
978-388-2221
978-388-9762
210 and 210 Plus Plastic Cleaner
Sumner Laboratories
186 Lincoln Street
Boston, MA 02111
617-542-8656
Fax: 617-482-9001
sumnerlabs.com
ACRIFIX® AC1010
Evonik Cyro LLC
acrylite.co
Plexus Plastic Cleaner
Plexus
638 Lindero Canyon Road #371
Agoura, CA 91301
818-879-1493
1-800-405-6495
plexusplasticcleaner.com
Finesse It Polishing System
3M Company
Microfinishing Systems Dept.
3M Center
St. Paul, MN 55144-1000
651-737-5467
Fax: 651-737-1790
 
Torch Equipment  
Smith Equipment
2601 Lockheed Avenue
Watertown, SD 57201
605-882-3200
Fax: 605-882-1887
arcsmith.com
National Torches & Tips
By Premier Industries
980 Osborne Road NE
Fridley, MN 55432
763-786-4020
Fax: 763-786-5424
nationaltorch.com

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