Processing Precautions for the Full Process of Granite Equipment Bases

Red Line of Processing Sequence: Raw Material Selection → Sawing and Rough Shaping → Rough Processing (Grooving, Drilling, Weight-Reduction Grooves) → Stress Relief Aging → Embedding Stainless Steel Threaded Inserts, Bonding and Joining → Multi-stage Constant Temperature Grinding → Manual Matching and Grinding → Constant Temperature Static Aging to Release Grinding Stress → Final Inspection, Hole Sealing and Protection → Packaging and Shipment
Strictly Prohibit Reversing the Sequence: Drilling, inserting sleeves, and grooving after fine processing will cause stress rebound, leading to precision drift and scrapping.

I. Raw Material Stage (Source defects cannot be repaired later)

1. For high-precision bases, Jinan Qinghui Green Granite is preferred due to its dense grain structure; reject materials with inclusions, white spots, mica clusters, or internal dark cracks; for high-end 00/000 grade, try to use whole blocks as much as possible, and do not allow the joining of raw blocks.
2. It is best to allow raw blocks to naturally age in advance to release original mining stresses; ultrasonic flaw detection can be used to screen for invisible internal cracks.
3. Blank allowance control: Reserve 3-5mm on each side for length, width, and thickness; leave a 0.4-0.6mm grinding allowance on each side for weight-reduction grooves and irregular grooves.
4. Drawing structural requirements: All internal corners must have a radius of R≥5mm; right angles are prohibited, as right-angle positions are extremely prone to chipping and generating radial micro-cracks.
5. Hole edge distance ≥50mm, hole-to-hole distance ≥100mm to reduce the risk of cracking during drilling.

II. Cutting and Rough Processing (Sawing, CNC Milling, Drilling)

1. Full water cooling throughout the process; dry cutting, dry drilling, and impact drilling are strictly prohibited; dry processing generates high temperatures, causing invisible thermal micro-cracks in the stone that will gradually deform and crack during later use.
2. CNC processing should use layered cutting; deep single-pass cutting is prohibited; reduce the feed rate at corners and edges to prevent chipping.
3. Weight-reduction grooves, countersinks, and all installation holes must be completely rough-processed; do not leave them for after fine grinding.
4. Control the flatness of the rough-processed surface to about 0.2 mm/m, leaving an allowance for the next process; do not pursue high precision during rough processing.
5. Clamping should not be overly tight; granite is highly brittle, and excessive clamping force will directly crack the workpiece; use soft-padded fixtures.

III. Stress Relief Aging (Determines the long-term precision stability of the base, most easily omitted)

Aging should only be done after all rough processing is completed; aging after fine processing is meaningless.

1. 000 Grade (Semiconductor, High-end CMM): Static aging in a constant temperature workshop at 20±1°C for 2-4 weeks, flipping the workpiece every 7 days to release cutting stresses.
2. For batch medium-to-high-end products, use artificial composite aging: 80°C insulation for 24h → -10°C insulation for 4h → slow return to 20°C, constant temperature static aging for 72h; the temperature rise and fall rate must be gradual to avoid new cracks caused by thermal shock.
3. Bases that do not undergo aging may pass factory inspection but will warp or exceed flatness tolerances after a few months of customer use, which is a typical process defect.

IV. Joining, Bonding, and Embedding Threaded Inserts (High-failure process)

1) Back-bevel Joining (Large-sized bases)

1. Only recommended for 0-00 grade; joining is prohibited for 000 grade.
2. Grind the mating surfaces first, bond with a thin layer of epoxy resin, and ensure the glue layer is uniform; after bonding, cure at a constant temperature for 24-48h, and only perform overall grinding after curing is complete; do not proceed directly to fine processing after bonding.

2) Key Points for Embedding Stainless Steel Threaded Inserts

1. Process sequence: Rough grinding – Drilling – Inserting sleeves – Complete glue curing – Then fine grinding, absolutely no fine processing before this.

V. Grinding and Machining (Constant Temperature is a Mandatory Condition)

1. 00, 000-grade grinding workshops must maintain a constant temperature of 20±1℃, with temperature fluctuations ≤±0.5℃; for every 1℃ change in temperature, granite will undergo micron-level deformation, making the ground precision false.
2. Gradually change the grinding wheel grit size without skipping grits: rough grinding → semi-fine grinding → fine grinding; after 00/000-grade mechanical grinding, manual lapping is mandatory, as machines cannot achieve 000-grade precision on their own.
3. Key points of manual lapping: use standard 000-grade lapping plates, silicon carbide micro-powder with water lubrication, and a cross-reciprocating trajectory; Blue oil spot inspection: for a 25×25mm area, spots must be ≥20, uniformly distributed, and excessive grinding at a single point causing local depressions is prohibited.
4. After each round of grinding, the workpiece must rest in the constant temperature workshop for 4-8 hours to release grinding thermal stress before proceeding to the next step; do not grind continuously without stopping.
5. Workpiece support: large bases must use three-point or multi-point equal-height flexible support; single-side cantilever support is prohibited, as grinding will generate torsional stress.

VI. Cleaning, Constant Temperature Resting, and Final Inspection

1. Thoroughly clean the stone powder after grinding, ensuring no abrasive particles remain; then rest at a constant temperature for 24-72 hours to allow dimensions to stabilize completely before final inspection, as measurements taken immediately after grinding are inaccurate.
2. Inspection items: flatness (laser interferometer), parallelism, perpendicularity (autocollimator), hole position accuracy (CMM), thread plug gauges, and pull-out testing; high-end bases must be issued a formal inspection report, which is essential for foreign trade customers.
3. Perform hole sealing and protection treatment to seal the stone’s micropores, preventing the seepage of cutting fluids and oil stains.

VII. Finished Products, Lifting, Packaging, and Transportation

1. Apply protective film to the precision working surfaces; ensure reasonable lifting points, and strictly prohibit prying corners with a single point, as granite corners are extremely prone to chipping.
2. Use foam cushioning inside the wooden crate; the base must be fixed with three-point support and cannot be laid flat on a hard surface, to prevent stress deformation caused by transportation bumps.
3. Mark the wooden crate with constant temperature, moisture-proof, do not lay on side, and flip-over labels.

VIII. High-Frequency Process Red Lines (Prohibited List)

❌ Prohibit skipping rough machining and going directly to fine grinding
❌ Prohibit drilling, slotting, or inserting threaded inserts after fine machining
❌ Prohibit dry cutting, dry drilling, and dry grinding, which will cause internal micro-cracks
❌ Prohibit using spliced stone for 000-grade bases
❌ Prohibit grinding without temperature control, which results in “false precision”
❌ Prohibit threaded inserts from protruding above the stone working surface
❌ Prohibit sharp internal corners; R-fillets must be made
❌ Prohibit direct inspection and shipping without constant temperature resting after grinding