Introduction
Duct forming machines—whether spiral, round, or rectangular—play a critical role in HVAC duct production. However, mechanical wear, improper setup, and material issues can lead to downtime and inconsistent quality.
This guide summarizes the most common duct machine problems and provides practical, technician-level solutions, supported by tables and process checklists for clear reference.
Common Problems Overview
Table 1：Common Duct Machine Problems at a Glance
| Problem | Symptoms | Primary Cause | Difficulty to Fix | Recommended Action |
|---|---|---|---|---|
| Poor duct shape | Out-of-round, wrinkles | Roller wear, wrong pressure | ★★☆ | Adjust/replace rollers |
| Feeding jams | Coil won’t feed | Tension or alignment issues | ★☆☆ | Fix coil tension, realign guides |
| Inaccurate length | Cut too long/short | Sensor or encoder issue | ★★☆ | Calibrate sensor, check wiring |
| Noise/vibration | Machine shaking | Loose bolts/bearings | ★★☆ | Tighten & lubricate |
| Weak seam | Seam not tight | Roller wear or pressure | ★★★ | Replace seam rollers |
| Overheating | Motor hot, stop errors | Power or ventilation | ★★★ | Clean fan, check power load |
Problem 1: Poor Duct Shape
Symptoms
Not perfectly round
Wrinkles or flattening
Spiral seam misalignment
Cause Breakdown (Table Format)
| Cause | Impact |
|---|---|
| Worn forming rollers | Shape distortion |
| Wrong roller pressure | Over-compression or loose forming |
| No lubrication | Roller dragging, uneven forming |
Fix
Adjust roller pressure for your sheet thickness.
Lubricate shafts daily.
Replace forming rollers when marking appears on duct surface.
Problem 2: Material Feeding Jams
Symptoms
Coil cannot feed
Material folding or bending
Machine stops intermittently
Cause Breakdown
| Cause | Solution |
|---|---|
| Coil tension incorrect | Adjust using tension control wheel |
| Bent coil edge | Trim before feeding |
| Feeding angle off | Re-align guide rail |
Problem 3: Inaccurate Cutting Length
Symptoms
Duct pieces too long or too short
CNC showing unstable values
Fix
Re-calibrate sensor every week.
Tighten encoder cables.
Replace dull blades to maintain accuracy.
Quick Calibration Checklist
| Step | Action |
|---|---|
| 1 | Reset zero position |
| 2 | Run test piece |
| 3 | Compare tolerance (±1–2 mm) |
| 4 | Adjust again if needed |
Problem 4: Excessive Noise or Vibration
Noise and vibration often indicate a mechanical alignment problem.
Possible Causes
Bearings worn
Bolts loose
Shafts not aligned
Fix
Tighten all bolts weekly.
Re-align the main shaft monthly.
Lubricate bearings daily to reduce internal friction.
Problem 5: Seam Not Tight or Leakage Risk
Symptoms
Spiral seam opening
HVAC installer reports air leakage
Causes & Fix Table
| Cause | Fix |
|---|---|
| Worn seam-locking rollers | Replace every 6–12 months |
| Wrong pressure | Reset according to material gauge |
| Poor sheet quality | Avoid uneven or soft material |
Problem 6: Overheating or Electrical Faults
Symptoms
Motor hot
Machine shuts down
CNC error codes appear
Fix
Clean fans & dust screens weekly.
Ensure correct power load.
Replace inverter or motor only with approved parts.
Maintenance Table
Duct Machine Maintenance Checklist
| Frequency | Tasks |
|---|---|
| Daily | Clean dust, lubricate rollers, check alignment |
| Weekly | Tighten bolts, calibrate sensors, clean electrical cabinet |
| Monthly | Inspect bearings, adjust shafts, check vibration level |
| Yearly | Replace worn rollers, update CNC, full machine inspection |
Conclusion
By understanding these common duct machine problems and applying structured preventive maintenance, manufacturers can significantly reduce downtime and improve consistent duct quality. Adding routine checks, proper lubrication, and sensor calibration ensures long-term stable operation.
FAQ
Mainly misaligned or worn forming rollers or incorrect pressure.
Usually due to incorrect coil tension or damaged coil edges.
Verify the encoder, sensor alignment, and blade sharpness.
Daily cleaning, weekly calibration, and yearly full inspection.
Regularly replace seam rollers and use the correct material gauge.