Components Of Coated Abrasives
Coated abrasives products have mainly 3 components, a backing which is flexible, a bond which is strong and flexible, and a single layer of abrasive. The main components are shown below.
The make coat is the first coat of adhesive which is applied on the backing and this is followed by the abrasive which is placed with a desired orientation on this make coat.
After curing this coat in the space between the abrasives a size coat of adhesive is applied this helps the grain to get firmly anchored.
Coated abrasives are made with grains which are longer and tougher than bonded abrasives. This ensures that the abrasive particles penetrate deeper with lesser forces and withstand very high pressures on the grain.
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The main components are hence :
· Backing
· Grain
· Bond
Backing supports or provides the foundation for the abrasive grain and because it is flexible allows the abrasive grain to be applied in the job in a variety of ways.
The Adhesive holds the abrasive grain in place till it is used up in the proper position in the backing
The Abrasive grain forms the cutting edge to grind, remove or polish material. Each grain in turn has a number of cutting edges, which form basic wedges for material to be removed.
Types Of Backings
· Paper
· Cloth - Cotton, Polyester and Rayon
· Vulcanized Fiber
· Combination - Paper and cloth laminated
· Wide mesh cloth - Screen Bak
· Polyester film
Types Of Coated Abrasive Products :
Fibre Discs
Fiber discs also called Sander Discs are used in sanding and polishing on portable sander polishers
These products use Vulcanized fibers as backing materials and are used mounted against a backup pad made of rubber or
Phenolic plastics. They can be used for very fast material removal rates without generating heat. They are made fully or
partial coated with grain in round or Rosette shapes.
AVOS Discs are new discs made by Norton which enables operator using discs to see the job he is grinding. This ensures no over grinding.
These discs are made with specially shaped holes in octagonal shape.
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Flap Discs
Flap discs are made with flaps of cloth backed coated abrasives stuck on a Phenolic backing.
These products are used on DCD or BDA machines which run at 80 m/sec speeds unlike a Sander polisher which runs at 33 m/sec speed.
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Fiber Discs and Flap discs are used in the following applications :
1. Weld grinding and blending in fabrication industry
2. Weld grinding and blending in Automotive body shops
3. Paint stripping applications when panels requiring repainting need old paint to be removed
4. Stainless Steel fabrication and finishing in Dairy, Pharma, Brewery, and Chemical plants
5. Fabrication of white goods like Kitchen sinks, Refrigerators, Steel furniture, Appliances
6. Grinding FRP materials
7. Beveling and grinding stone monuments
Psa Discs
Also called Stick N Sand discs or Stick It Discs are made with Cloth or Paper backings and are laminated on the back side
with Pressure sensitive adhesives (PSA). These discs can be used by sticking them on a Rubber or Foam back up pad and removed
after use.
These discs are used on Straight or Orbital sanders for sanding and polishing on the full face of the discs.
They are made as discs and disc rolls
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Velcro Backed Discs
These types of discs are similar to PSA discs but have a scrim cloth laminated to the back of the discs thus enabling them to be
stuck on a special back up pad which has Velcro hooks.
This type of fastening discs is more than PSA and these discs have the added
advantage of not having the adhesive getting weak when dust or swarf collects on the back of the disc.
These discs are also called
Speed-Grip discs or Hookit
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Major applications for PSA and Velcro discs are given below :
1. Blending scratches in Automotive body shops
2. Feather edging and Sealer sanding of wood
3. Watch case polishing
4. General finishing in fabrication industry
Speedlok Or Roloc Discs
These discs are smaller size with a quick flash locking system provided on the back so that they can be mechanically held on a large metal
or plastic threaded cavity on a holder.
These holders can be held on collate chucks on angle sanders and die grinders and
used for quick local sanding.
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Major applications of Speedlok discs are :
1. Weld and defect sanding in body shops of difficult to reach areas
2. Mould defect sanding in mould shops
3. Sanding welds which are difficult to reach in fabrication industry
4. General rust removing and cleaning
5. Creating special finishes like Sunray in Stainless steel fabrication
6. Maintenance and Repair operations
Coated Abrasive Belts
Belts are made by joining cloth or paper backed rolls into belt forms with an angular joint.
The belt is mounted between rolls of
rubber or steel and used for various sanding applications.
They are made in Narrow size - width upto 450mm and wide sizes from 455 - 1375 mm
in single joints. Wider width belts upto 92 inches can be made with multiple joints.
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Major applications with Wide belts which are used on special wide belt machines are :
1. Roughening backside of laminates
2. Stainless Steel coil defect sanding
3. SS Coil and sheet polishing
4. Flat sheet and job deburring and surface grinding
5. Lumber sanding natural wood logs instead of planning
6. MDF, Plywood and Particle board finishing
7. Furniture intermediate sanding and dimensioning
8. Leather buffing and Sueding
Major applications with narrow belts are :
1. Watch strap and Case polishing and special finishing
2. Shoe sole and heel buffing and roughening
3. Removing Risers and Runners from casings
4. Grinding investment casting projections
5. Removing forging flash from forgings
6. Automatic production of hand tools
7. Grinding and polishing brass sanitary ware, plumbing fixtures, door knobs, locks
8. Aircraft turbine blade plishing defect removal and maintenance
9. Power and Steam turbine blade polishing
10. Mold sanding curved wooden parts.
11. Cleaning Aluminum castings
12. Glass edge beveling and polishing
13. Rubber tread roughening
14. Polishing knives and Scissors
15. Polishing hydraulic rods
16. Centre less grinding SS and Zirconia tubes
Flap Wheels & Mops
Flap wheels and mops are made by radially fixing cloth coated abrasives in wheel form like a brush. These are used then on portable
or fixed machines for cleaning, polishing and special finishing.
Flap wheels are made with a bore for mounting and Mops are made with
spindles for collets holding.
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Typical Flap wheel and Mop applications are :
1. Blending grinding and sanding marks in fabrication industry
2. Bicycle and Two-wheeler rim polishing before chrome plating
3. Automatic buffing or pots pans and kitchenware
4. Watch strap and Case polishing
5. Deburring Automotive parts
6. Die and Mould polishing
7. Cleaning and surface preparation in plating shops
Sleeves or Spirabands
These are joint less small interlined belts which are mounted on expanding rubber mandrels and used on portable machines
for sanding. They are made with cloth backed coated abrasives.
These products are used in die and mould applications.
Pencils and Cartridge Rolls
These are made by using cloth based coated abrasives and fixing them on spindles in a spirally wound way which exposes fresh
abrasives as one layer wears out.
They are very productive over mounted points which are used for similar jobs. The main application areas are
maintenance repairs and mould maintenance.
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Sheets and Rolls
Sheets made with paper, cloth and screen cloth backing are used for hand sanding applications for cleaning surface
preparation and polishing.
Many hand sanding applications is fast being replaced by machine sanding using portable machines
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Applications for sheets are :
1. Water proof paper sheets used for paint and primer scuffing.
2. Cloth sheets used for maintenance and repairs
3. Emery paper sheets for die mould and specimen polishing
4. Wood and polish sealer sanding coat paper
5. Emery cloth sheets used for general operations
Rolls
Rolls are available in various widths like sheets for hand sanding. They are also used for Drum sanding on machines where they are wrapped around steel drums and used like large wheels. Special rolls made with polyester film backings are used for crankshaft, cam shaft and other automotive components for lapping in special machines. Rolls are supplied to converters making coated products
Some applications for rolls are :
1. Buffing leather on Drum Sanders
2. Plywood sanding on Drum Sanders
3. Crankshaft and Camshaft polishing
4. Polishing diary equipment using Flutter wheels
5. Turn polishing contoured wooden parts on Turn Sanders
6. Slit and Scoured rolls on Vonnegut wheels
7. Hand sanding applications
The history of coated abrasive manufacture is very old and some of the first types of abrasive products were coated abrasives manufactured as early as 1700 AD. Till early 1900 most coated abrasive products used were made with natural abrasives like pumice, flint, garnet, and emery and only after synthetic abrasives were discovered like Aluminum oxide and Silicon carbide did applications for these products extend beyond hand sanding and polishing.
The broad application classification of abrasives are :
1) Cleaning and Deburring - where unwanted material is removed from the job
2) Shaping and dimensio where the job is brought to desired shape and dimensions
3) Polishing and finishing - where a desired surface finish is imparted.
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