Key Functions of Ball Screws in Swiss-Type Lathes

2025-07-26

Core Function:
Converts the rotary motion of servo motors into nanometer-level linear displacement of tool posts, guide bushings, and main spindles.
Technical Implementation:
- Utilizes ultra-high-precision ball screws of C0 grade (JIS) or P0 grade (ISO) and above (positioning error ≤ 3μm/300mm).
- Achieves repeat positioning accuracy ≤ ±1μm with closed-loop linear encoders.
Impact:
Ensures micron-level dimensional and geometric tolerances (e.g., coaxiality, cylindricity) for miniature parts (medical bone screws, watch gears).

Core Function:
Enables multi-axis synchronized high-speed cutting (e.g., simultaneous turning with radial tool posts and milling with end-facing live tools during spindle rotation).
Technical Implementation:
- High-lead design (lead: 10–20 mm) reduces rotational speed requirements while increasing feed rates (up to 30 m/min).
- Dn value ≥ 160,000 (screw nominal diameter × rpm) prevents step loss at high speeds.
Impact:
Achieves single-setup machining of complex small parts and reduces cycle time.

Core Function:
Resists radial/axial cutting forces during machining, preventing tool path deviation or vibration.
Technical Implementation:
- Ultra-high preload (axial rigidity ≥ 500 N/μm) eliminates backlash.
- Raceway hardness ≥ HRC 60; ball accuracy: G5 grade (diameter variation ≤ 0.5 μm).
Impact:
Maintains dimensional stability of thin-walled parts (e.g., electronic connector housings) and prevents surface roughness degradation (Ra > 0.4 μm) from chatter marks.

Core Function:
Suppresses screw elongation caused by frictional heat, preventing dimensional drift in batch production.
Technical Implementation:
- Hollow cooling structure: Circulates temperature-controlled oil (20±0.5°C) internally to limit temperature rise to ≤1°C.
- Pre-tensioned mounting: Applies 0.03 mm/m pre-stretch to counteract thermal expansion (ΔL=α·L·Δt, α≈11×10⁻⁶/℃).
Impact:
Compresses thermal error to ≤2 μm (vs. 20 μm in standard screws), eliminating batch failures after extended machining.

Core Function:
Maintains precision for over 10 years under frequent micro-step interpolation (e.g., turning 0.01 mm micro-threads).
Technical Implementation:
- Multi-lip seals + long-life grease (e.g., Kluber NBU series) block dust and chips.
- Ceramic balls/special coatings (e.g., NSK HTF-SRC series) reduce wear rates.
Impact:
Minimizes downtime and meets stringent reliability requirements in medical/aerospace applications.

Ball screws are the physical enablers of Swiss-type lathes across five critical dimensions:

Micron-level positioning for complex micro-structures;
High-speed rigidity supporting synchronized multi-axis cutting;
Active thermal control ensuring batch consistency;
Ultra-wear-resistant design enabling maintenance-free operation for 10+ years.
Their performance defines the precision ceiling of Swiss-type machining – truly "invisible champions" in precision transmission.