Auto Duct Line Preventive Maintenance Guide (2026)

Why Preventive Maintenance Matters

An auto duct line is a complex integration of motors, gearboxes, hydraulic systems, PLC controls, and forming rolls — all working in sync. When one component fails, the entire line stops. A single day of downtime can cost $500-$2,000 in lost production, plus rush shipping for emergency parts.

Preventive maintenance is the single most effective way to protect your investment. Following this schedule will:

• Reduce unplanned downtime by 80%
• Extend machine life from 8-10 years to 15+ years
• Maintain consistent product quality
• Reduce long-term repair costs by 40%
• Keep your warranty valid (most warranties require documented maintenance)

Daily Maintenance (5 minutes per shift)

Perform these tasks at the start of every shift before production begins:

1. Visual inspection — Walk the full length of the line. Look for loose bolts, leaking hydraulic fluid, worn belts, or debris.
2. Clean forming rolls — Wipe rolls with a clean cloth to remove zinc dust and metal shavings. Buildup causes scratches and dimension errors.
3. Check hydraulic oil level — Oil should be between min and max marks on the sight glass. Top up if low.
4. Check air pressure — If using pneumatic components, verify pressure is 6-8 bar (90-120 psi).
5. Lubricate chain drives — Apply a few drops of chain oil to all drive chains.
6. Test emergency stop — Press the E-stop to confirm it cuts power immediately.
7. Run test piece — Produce one test duct section and check dimensions before full production.

Weekly Maintenance (20 minutes)

Perform at the end of the last shift each week:

1. Clean entire machine — Remove all metal shavings, dust, and debris from every station. Use compressed air (wear safety glasses).
2. Check belt tension — Press each belt with your thumb. Deflection should be 10-15mm. Adjust if too loose or too tight.
3. Inspect belt condition — Look for cracks, fraying, or glazing. Replace if damaged.
4. Lubricate all grease points — Use a grease gun on every grease nipple (forming roll bearings, drive shafts, pivot points).
5. Check decoiler operation — Verify coil holder rotates freely, brake tension is correct, and expansion mandrel works properly.
6. Clean electrical cabinet — Blow out dust with low-pressure air. Check for loose wire connections.
7. Verify cutting blade sharpness — Check cut edge quality. If burrs are visible, blade may need sharpening or replacement.

Monthly Maintenance (1 hour)

1. Check gearbox oil level — All reduction gearboxes. Top up with specified gear oil (ISO VG 220 or VG 320) if low.
2. Inspect hydraulic hoses — Look for cracks, bulges, or leaks at fittings. Replace any damaged hose immediately.
3. Calibrate length measurement — Produce 5 test pieces at 1000mm. Measure each with tape. Adjust encoder calibration if error exceeds ±2mm.
4. Check forming roll alignment — Use a straightedge across the rolls. Misalignment causes twisted duct and uneven seams.
5. Tighten all mounting bolts — Vibration can loosen bolts over time. Check and retorque all visible bolts.
6. Inspect pneumatic components — Check filters, drain water from air filter, lubricate air tools.
7. Backup PLC program — Save the PLC program to a USB drive. Store backup in a safe place.
8. Test safety interlocks — Verify all safety guards and interlocks function correctly.

Quarterly Maintenance (2 hours)

1. Change hydraulic oil filter — Replace the filter element. Oil should be changed every 2,000 operating hours (typically yearly).
2. Inspect all bearings — Listen for unusual noise, check for play. Replace bearings that are rough or noisy.
3. Check motor insulation — Use a megohmmeter to test motor winding insulation. Minimum 1 megohm.
4. Calibrate punching/notching dies — Check hole position and size. Adjust if drift is detected.
5. Inspect leveling rollers — Check for wear patterns. Adjust roller pressure if material is not flat after leveling.
6. Verify folding accuracy — Check fold angle with a protractor. Adjust if not 90° ±0.5°.
7. Clean cooling fans — Clean all motor and cabinet cooling fan filters.

Yearly Maintenance (4 hours)

1. Change all gearbox oil — Drain and refill with fresh gear oil. Dispose of old oil properly.
2. Change hydraulic oil — Drain, clean tank, refill with specified hydraulic oil (ISO VG 46 or VG 68).
3. Replace all drive belts — Even if they look good, belts degrade over time. Replace annually.
4. Replace hydraulic hoses — Hoses degrade from the inside. Replace every 3-5 years, or yearly if in harsh environment.
5. Full electrical inspection — Check all contactors, relays, terminals. Tighten all electrical connections.
6. Inspect forming rolls for wear — Measure roll diameters. Replace if worn more than 0.5mm from original.
7. Recalibrate entire line — Full dimensional calibration including length, width, fold angle, flange position.
8. Update PLC firmware — Check for manufacturer updates. Preda Care provides free firmware updates.

Common Issues and Quick Fixes

Wear Parts to Keep in Stock

Having critical wear parts on hand reduces downtime from days to hours. We recommend keeping these in stock:

Preda Care ships all wear parts free of charge worldwide. Most parts arrive within 3-7 business days via DHL or FedEx.

Frequently Asked Questions