Diamond soft grinding discs (resin-based soft grinding discs, used for polishing stone/ceramic) 
The mainstream products in the market are resin-based soft grinding discs. These can be divided into hot-pressed types (the current market standard) and AB glue-based dry grinding discs. The grinding discs typically consist of a abrasive layer and a backing cloth (nylon cloth).

I. Composition of raw materials (by weight percentage) 
1. Diamond abrasives (5%–30%) 
Single-crystal diamond powder (HPHT) is the preferred choice. Based on type, it can be divided into RVD and MBD. Nickel or titanium-coated diamonds are used in high-end products; they improve the resin grip, service life, and sharpness. Particle size range: W20–W500 (covering from coarse grinding to mirror-polished finish). High-end products use fine-grained powder; low-end products may use mixed materials, recycled diamonds, or particles with wide particle sizes. 
Coarse grades (W20–W40): Used for removing material; medium grades (W60–W120): For intermediate steps; fine grades (W180–W500): For mirror-polished finishes.

1. Resin binders (30%–60%, the core component) 
Phenolic resin (most commonly used in hot-pressed types): Moderate cost, good heat resistance, and adjustable hardness. Includes ordinary phenolic resin and modified phenolic resins (silicone/dimethyl polysiloxane modification, resistant to high temperatures and prevents disc burning). 
Epoxy AB glue (for dry grinding discs): Component A is epoxy resin, Component B is polyamide curing agent. Curing can occur at room temperature or low temperatures. Good toughness, but poor heat resistance; discs are prone to burning during dry grinding. 
Modified rubber/nitrile rubber: Used to increase elasticity and flexibility, improving the flexibility of soft grinding discs and preventing edge cracking. Small amounts of rubber powder are often added in high-end formulations. 
Curing agents: In phenolic systems, hexamethylenetetramine is used; in epoxy systems, special curing agents are used.

3. Fillers (15%–40%), which determine hardness, self-sharpening ability, polishing shine, and cost 
Auxiliary abrasives: Corundum, silicon carbide, chromium oxide (chromium green, used for polishing and enhancing shine), zinc oxide, aluminum oxide powder; 
Pore regulators: Hollow glass beads, calcium carbonate, talc; hollow beads are used to create microholes, improving self-sharpening and making the disc softer; fillers: heavy calcium carbonate, talc (cheap fillers used to reduce costs); 
Additives: Silane coupling agents (used for surface modification of diamonds/fillers, improving resin adhesion), defoamers, colorants, lubricants (molybdenum disulfide).

1. Backing material 
Nylon cloth (Velcro-like backing cloth), pressed together with the abrasive layer during hot pressing; low-end products use thin cloth, which may cause separation.

II. Production processes (two main methods) 
Method A: Hot-pressing molding (wet or dry grinding discs, mainstream in the market) 
Mixing ingredients: Resin powder, diamonds, fillers, and coupling agents are mixed dryly to ensure proper dispersion; diamonds need to be modified before mixing. 
Laying the cloth: The mixture is evenly spread in the mold, with nylon cloth on top. Hot-pressing sintering: Using a flat sintering machine; temperature 150–170°C, pressure 40–80MPa, holding for 8–15 minutes. Resin melts and cross-links, encasing the diamonds and pressing them together with the backing cloth. 
Post-curing (second curing in an oven): After removal from the mold, cured at 120–140°C for 4–8 hours to improve strength, reduce internal stress, and prevent deformation or particle loss during use. 
Edge trimming, inspection, packaging.

Method B: AB glue casting process (dry grinding discs) 
A/B epoxy glue is mixed in proportion, diamonds and fillers are added, and vacuum deaeration is performed; 
The mixture is poured into the mold, with backing cloth on top; 
Low-temperature curing in an oven (70–90°C); 
Removal and adjustment after curing. 
Advantages: Simple equipment; disadvantages: Poor heat resistance, discs burn easily during dry grinding, short service life. 
Key factors: Even mixing, hot-pressing temperature, pressure, time, proper post-curing, diamond modification, directly affect quality.

III. Differences in formulations between different quality levels (low-end/medium-end/high-end) 🔹 Low-end (cheap products) 
Diamonds: Recycled materials, low-strength RVD, no metal coating; wide particle size distribution, mixed coarse and fine particles; low diamond content. Resin: Ordinary cheap phenolic resin, no modification; little rubber added, disc is hard and less flexible; fillers: Large amounts of heavy calcium carbonate and talc as cheap fillers; few hollow beads; no coupling agents; 
Process: Insufficient hot-pressing time, no post-curing; thin backing cloth. 
Performance: Severe particle loss, short service life; poor polishing shine; discs burn stone easily; hard, prone to edge cracking; quickly worn out.

🔹 Medium-end (mainstream price-performance) 
Diamonds: New MBD single-crystal powder, narrow particle size; some use nickel-coated diamonds; moderate diamond concentration; 
Resin: Ordinary phenolic resin with a little modification; rubber powder added to ensure flexibility; 
Fillers: Balanced combination of corundum, chromium oxide, appropriate amount of hollow glass beads; silane coupling agents added; 
Process: Complete hot-pressing and post-curing; thicker nylon backing cloth. Performance: Good sharpness, stable polishing shine; normal service life; suitable for polishing ordinary stone; not easy to burn.

🔹 High-end (mirror-polished finishes, high-end stone/ceramic) 
Diamonds: Titanium/nickel-coated single-crystal diamond powder, precise D10/D50/D90 particle size distribution; high purity; some fine particles use polycrystalline diamond; sufficient diamond concentration. 
Resin system: Modified high-temperature resistant phenolic resin (silicone modification) combined with rubber; balances heat resistance, flexibility, and toughness; strong resin grip, diamonds do not fall off. 
Fillers: Fine-grade auxiliary abrasives (corundum, chromium oxide); precise hollow bead ratio, controlled pore size; sufficient coupling agents; control filler types to avoid scratches or discoloration. 
Process: Proper mixing, vacuum treatment; accurate hot-pressing parameters; thorough post-curing; high-strength backing cloth. Performance: Sharp, self-sharpening, high mirror polish, long service life, not easy to burn, not easy to crack; fine particle size, no scratches during polishing; no disc burning over long periods.

IV. Key points in formula design 
Diamond concentration: Too high leads to disc blockage; too low means lack of wear resistance; higher concentration for coarse grinding, lower for fine polishing. 
Resin hardness: Hard resin provides wear resistance but poor self-sharpening, easy to burn; soft resin (with rubber, hollow beads) has good self-sharpening, gentle polishing, but faster wear. 
Coupling agents: High-end formulas require diamond surface modification, otherwise diamonds may fall off. 
Hollow glass beads: Increase pores, improve self-sharpening, reduce hardness, increase flexibility; too much reduces disc softness and strength. 
Post-curing: If omitted, internal stress remains, leading to deformation, particle loss, and aging during use.

V. Simple way to distinguish high-quality from low-quality products 
Feel: High-end soft grinding discs are flexible, not easy to crack when bent; low-end products are hard and brittle, easy to crack. 
Polishing effect: High-end fine discs produce mirror polish without scratches; low-end discs have foggy polishing and scratches. 
Use: High-end discs do not burn, stone does not burn; low-end discs burn easily and have particle loss.