Standard ground glass instrument

Standard ground glass instrumentProduction requires strict control of process parameters to ensure the sealing, interchangeability, and durability of the grinding mouth. The following are key precautions:

1、 Grinding design and specification control

1. taper standard: strictly follow the standard taper

2. Dimensional accuracy: The diameter of the large end and small end of the grinding mouth, as well as the length of the grinding mouth, must meet the standards

3. Matching tolerance: The grinding clearance should be controlled between 0.01-0.05mm. If it is too tight, it is easy to get stuck, and if it is too loose, it is easy to leak

4. Surface roughness: Ra ≤ 0.8 μ m, ensuring good sealing and grease adhesion

5. Concentricity: The coaxiality between the grinding axis and the instrument body axis is ≤ 0.1mm

Common standard grinding specifications:

Small: NS 7/16, NS 10/19, NS 14/23

Medium size: NS 19/26, NS 24/29, NS 29/32

Large: NS 34/35, NS 45/40, NS 55/44

2、 Material selection and pretreatment

1. Glass material

High borosilicate glass (3.3): coefficient of thermal expansion 3.3 × 10 ⁻⁶/K, resistance to sudden temperature changes ≥ 120 ℃

Medium borosilicate glass (5.0): coefficient of thermal expansion 4.9 × 10 ⁻⁶/K, with good economy

Avoid using: Sodium calcium glass (with a high coefficient of thermal expansion, prone to stress cracking)

2. Preprocessing requirements

Annealing treatment: eliminate molding stress, annealing temperature 560-580 ℃, slow cooling to prevent explosion

Cleanliness: No oil stains, no dust, avoid scratching the surface during grinding

Temperature balance: The glass temperature before processing should be consistent with the ambient temperature to prevent thermal deformation

3、 Grinding processing technology

1. Grinding process parameters

Abrasive selection: Silicon carbide or corundum abrasive, particle size W14-W28 (coarse grinding) → W5-W10 (fine grinding)

Grinding tool speed: 800-1500rpm, too high can easily burn the glass, too low has poor efficiency

Coolant: Continuous supply of water-based coolant to prevent thermal stress cracking

Feed rate: ≤ 0.05mm per feed to avoid edge breakage

Grinding pressure: 0.1-0.3MPa, maintain uniform pressure

2. Key process control

Rough grinding forming → Semi precision grinding (correcting taper) → Precision grinding (improving surface quality) → Grinding and polishing (mirror effect) → Cleaning and testing

After rough grinding: taper gauge inspection to ensure accurate taper

After precision grinding: standard plug gauge inspection, contact surface ≥ 80%

After grinding: no scratches, cracks, or broken edges detected by light inspection

Finally, it was tested in conjunction with the standard grinding mouth, and the rotation was smooth without any jamming

4、 Key points of quality control

1. Online detection

Plug gauge testing: Use a standard grinding plug gauge to check the tightness of the fit

Coloring test: Apply red lead powder to check the distribution of the contact surface, requiring uniform and continuous distribution

Vacuum test: Vacuum to -0.09MPa, hold for 5 minutes, pressure drop ≤ 5%

2. Finished product inspection

Appearance quality: no bubbles, no stones, no cracks, no broken edges

Dimensional accuracy: Vernier caliper/specialized gauge, tolerance ± 0.1mm

Interchangeability test: Grind and plug with the same specification standard for more than 10 times, without jamming or leakage

Thermal stability: water bath rapid cooling method: sudden change from 200 ℃ to 20 ℃, no explosion

Chemical stability: Water/acid/alkali resistance test