2009 CAFA Convention February 13 16, 2009 Indian Wells, CA CAFA and Their Effect on Performance. February 14, Presented by Mark Boudreau

Transcription

1 CAFA 2009 Coated Abrasive Components and Their Effect on Performance February 14, 2006 Presented by Mark Boudreau

2 Typical Coated Abrasives Construction Top Size/Stearate Backing Cotton, Polyester, Poly-Cotton, or Paper Base Coat Hide glue, Urea resin, or Phenolic resins Size Coat Hide glue, Urea resin, or Phenolic resins. Size Coat Grain Base Coat Backing Top Size/Grinding Aid Third layer grinding aid to reduce friction and heat. Stearates help prevent loading on soft materials.

3 Cloth Manufacturing Produced by spinning of fibers into a filament that is mm long. Filaments are spun into yarns. Yarn is woven into raw cloth.

4 Cloth Manufacturing Warp is the yarn running the length of the material. Weft is the yarn running the width of the material. Weft yarn is weaved over and under the Warp yarn in ratios of 1:1, as high as 1:4, with 1:2 the most common. Typically the Warp (length) yarn is larger, and therefore stronger, then the Weft (width) yarn.

5 Backing Types Cotton: Lower tensile strength due to the non-elastic (low stretch) characteristic of cotton. Low tear resistance in both Warp and Weft. Cotton must be treated to prevent migration of the base coat resins into the cloth which creates brittleness. The treatment of the cotton is detrimental to creating a mechanical bond that optimizes grain retention.

6 Backing Types Polyester: Excellent strength and durability due to the elasticity. Tear resistance of the width due to the larger threads of the Warp. Polyester does not require treatment to prevent brittleness. The untreated cloth provides a mechanical bond for optimal grain retention.

7 Backing Types Poly-Cotton: Mixture of polyester and cotton fibers to create filament which is spun into yarn. Typical ratio of polyester to cotton is 65% to 35%. Hybrid backing has benefits of both polyester and cotton with good base adhesion and low stretch.

8 Y X T J F E Cloth backing type Cloth backing type and stiffness

9 Weight of pa aper g/m A B C D E F G Paper type Paper type and weight

10 Summary of Grain Characteristics Single crystal Cut rate decays at start of grinding Fracturing - Dulling Brittle A/O & S/C Zirconia Alumina Multi-crystal Cut rate decays at start of grinding Self-sharpening Tough Billions of crystals Cut rate remains constant for 75% of grinding life Self-sharpening grain provides more aggressive cut Tough Ceramic

11 Grain Sizing The ANSI, FEPA & JIS scales have grain size differences at the fine and coarse ends of the scales JIS separates from ANSI and FEPA coarser than 36 grit ANSI separates from FEPA & JIS finer than 240 grit Micron grading is based on the average size of the grain diameter FEPA P (European Std.) ANSI (U.S. Std.) P16 16 P20 20 JIS AVG. GRAIN (Japanese Std.) DIAMETER (µm) P24 24 P P P P P P P P P P P P P P P P P P P P P

12 Evolution of Bonding Systems Hide Glue: Water soluble (non-waterproof). Elastic characteristics creates a passive grain presentation resulting in uniform finishes. Urea Resin: Cheaper than hide glue. Water resistant characteristics. Phenolic Resin: Most durable waterproof bond.

13 Grinding Aids Cryolite: Sodium Hexafluoroaluminate, Na 3 AlF 6. Added into size coat for heat dispersment on metal enhancing performance 10% - 20% as a lubricant reducing friction. Top Size: KBF 4 also known as Potassium Fluoroborate. Typically used as a third layer resin to reduce heat in grinding high alloy steels such as stainless steels, titanium, and inconel. Adds no benefit to mild steels.

14 Bonding Systems Illustrated 2009 CAFA Convention

15 Coating Densities 2009 CAFA Convention

16 Electrode Backing Abrasive Grain Electrostatic Field Grain Conveyor Belt Electrode Electrostatic Coating of Coated Abrasives (schematic)

17 Coating Technologies Close Coat Conventional Abrasive Split Coated Abrasive 100% Grain Coverage Open Coat 25% - 80% Grain Coverage Split Coat -Higher grinding forces per grain -Enhanced grain regeneration -Designed for light to moderate pressure applications

18 100% Coverage 10 lbs Force 2 lbs Force per Grain

19 75% Coverage 10 lbs Force 2.5 lbs Force per Grain

20 50% Coverage 10 lbs Force 3.33 lbs Force per Grain

21 100% Coating Split Open-Coat

22 Coated Abrasive Product Types 2009 CAFA Convention

23 Product Types - Supported Flap Discs Spiral Bands Discs Belts QTD Body Cones

24 Product Types - Unsupported Flap Wheels Sanding Stars Overlap Discs Slotted Discs Rotofinishers Slashed Loadings

25 Product Types - Wrapped Cartridge Rolls Cone Points Square Pads Cross Pads

26 Common Coated Abrasive Problems

27 Loading A loaded abrasive shows metal packed in between the abrasive grains Most commonly encountered with nonferrous metals Can be inhibited by use of Grease, Calcium stearate or open-coated abrasive.

28 Stripping - Shedding When an abrasive material strips or sheds, the grain is pulled away from the backing Most often encountered during high pressure on the individual grain points Consider using 100% coating on polyester backing

29 Glazing Glazing is caused by heat build up due to friction created by the dulling of the abrasive grain. Most commonly encountered with harder alloy metals such as titanium, inconel, and harder stainless. Reduce cutting speeds, topsize, ceramic grain, open or split coat abrasive.

30 Thank you! Questions?