Servo Driven Robotic Aluminum Polishing Machine For Motorcycle Front Fork Tube

The motorcycle front fork tube represents one of the most demanding polishing applications in two-wheel manufacturing. Its complex geometry combines a long cylindrical outer barrel, intricate flange/crown mount at the top, side-ported boss features, decorative groove lines on sport variants, and a precision bore at the lower end. All surfaces must achieve Ra ≤ 0.1 µm before hard chrome plating or Ra ≤ 0.2 µm before anodizing, with zero tolerance for scratches, pits, or waviness.

Manual polishing of fork tubes is physically demanding, inconsistent along the tube length, and difficult to scale without extensive operator teams. Even experienced polishers struggle to maintain uniform pressure across 400-600 mm tube barrels while navigating flange transition zones without damaging crown faces.

The LRMC-FK Series Servo-Driven Robotic Polishing Machine addresses these challenges comprehensively. A servo-controlled spindle maintains precise rotational speed regardless of load conditions. A 6-axis robot arm with active force control continuously tracks the tube profile, adapting to diameter transitions, flange shoulders, and decorative groove geometry. The result is repeatable, auditable, plating-ready surface finish on every tube, every cycle.

Fork tubes feature non-uniform diameters across the main barrel, flange shoulder, and end boss sections. Fixed-speed spindles lose surface speed at smaller diameters and over-polish at larger ones.

The LRMC-FK servo spindle continuously adjusts RPM to maintain constant surface speed (CSS) as abrasives traverse diameter changes:

• Spindle speed range: 500 - 12,000 RPM (servo-controlled)
• Constant surface speed control: ±2% across full tube profile
• Torque feedback: real-time abrasive wear detection
• Spindle power: 1.5 - 3.0 kW

The polishing program covers complete fork tube geometry in a single uninterrupted cycle:

• Cylindrical barrel zone: helical polishing path, uniform overlap ratio, consistent Ra along full length
• Flange/crown transition: path automatically lifts contact angle to follow shoulder radius without gouging flat face
• Side boss and port features: reduced-force contouring around raised boss geometry
• Decorative groove lines (sport variants): dedicated groove-tracing path with narrow-profile wheel
• Lower bore end face: optional flat-face polishing stage

Contact force range: 5 - 120 N, zone-programmable. Force repeatability: ±0.5 N.

The fork tube rotates on a servo-driven twin-chuck fixture (live centers) while the robot arm delivers abrasive tools along the tube axis. This cylindrical grinding-inspired configuration ensures complete external surface coverage.

A laser measurement station at cell entry scans each tube before polishing begins:

• Measures outer diameter at 3 axial positions
• Measures total tube length
• Auto-selects matching polishing recipe from stored library
• Flags dimensional out-of-spec parts before polishing (prevents abrasive waste on rejects)
• Compatible with 20+ fork tube variants in a single cell

• 2 shifts/day, 250 days/year
• Replace 5 manual polishers @ USD 18/hr fully loaded
• Monthly abrasive spend: USD 3,500 → 30% saving = USD 1,050/month
• Hard chrome plating reject rate: 15% → 1.5% on 6,000 tubes/month @ USD 4.50 rework cost/tube

• 6-axis robot arm, 20-50 kg payload
• Servo-driven spindle (1.5 kW)
• Twin-chuck rotating fixture (Ø28-65 mm, L250-700 mm)
• 4-station automatic abrasive changer
• Manual tube load/unload
• HMI with 200-recipe storage
• Basic dust extraction

A: Yes. The twin-chuck fixture accommodates Ø28-65 mm as standard. The laser recognition station measures each tube at load-in and auto-selects the correct recipe — no manual adjustment needed when switching between diameters within the supported range.

A: The CNC path program includes a dedicated transition zone where the robot arm lifts the contact angle to follow the shoulder radius, simultaneously reducing contact force and adjusting spindle RPM to maintain constant surface speed on the reduced-diameter shoulder. The result is a smooth, continuous finish across the barrel-to-flange transition with no step mark or over-grind.

A: Yes. Decorative grooves are handled by a dedicated abrasive stage using a narrow-profile conical wheel. The path traces only the groove floor and chamfers the groove edges to a controlled radius — the surrounding polished barrel surface is not contacted during this stage.