Case

Case Highlights

A leading Asian manufacturer of industrial automatic doors wanted to reduce noise and extend the life of its drive units used on warehouse and supermarket doors. Existing worm gearboxes were loud at peak speed and required overhaul every 2–3 years on busy openings.

DD Gear engineered a compact, low-noise gearset that fits into the same housing: a hardened steel helical input stage driving a bronze worm wheel output stage. After the change, typical door installations recorded about 5–6 dB lower operating noise at 1 m and roughly double the gearbox maintenance interval, while keeping opening/closing speed unchanged. Helical gears are widely used where quieter operation is needed, as their angled teeth engage gradually and distribute load over multiple teeth, reducing vibration and whine compared with spur gears.

Customer Background & Project Scope

• Customer industry: Manufacturer of sectional and high-speed roll-up doors for warehouses, logistics centers and retail stores. High-cycle products often reach 200,000+ open/close cycles per year, similar to other commercial high-cycle doors.

• Application: Motor-gearbox units that drive rolling drums or counterweight shafts on interior and exterior doors.

• Project goals:

  • Reduce operating noise at typical opening speeds.

  • Increase service life of the gearbox in high-cycle locations.

  • Keep the outer dimensions and shaft positions of the drive unit unchanged for easy retrofit.

The OEM’s existing gearmotor design used a single worm-gear stage with relatively coarse tooth geometry. As sales volumes grew and doors were installed in noise-sensitive areas (retail, offices above warehouses), customer complaints and maintenance costs increased.

Challenges

1. High operating noise near the door opening

   • Door operators measured around 68–70 dB at 1 m during opening, perceived as intrusive in quiet indoor spaces.

   • The direct sliding action in the worm mesh and coarse tooth form contributed to whine and vibration.

2. Limited gearbox life in high-cycle doors

   • On doors exceeding 150,000 cycles/year, the bronze worm wheel showed wear steps and pitting after 2–3 years.

   • Backlash increased, causing a “clunk” when starting and stopping, and required gearbox replacement to avoid failure.

3. Tight packaging constraints

   • The new gearset had to fit into the existing cast-aluminum housing, keeping shaft centers, mounting holes, and drum interface unchanged so that dealers could retrofit in the field.

DD Gear Solution

1. Design Optimization

• Two-stage architecture

  • DD Gear added a small-module helical input stage between the motor and worm shaft.

  • The helical stage handles speed reduction and smooths torque fluctuations before the worm mesh, which helps reduce vibration at the final output. Helical gears generally run smoother and quieter than spur gears due to gradual tooth engagement and higher contact ratio. 

• Tooth geometry refinement

  • Optimized helix angle and profile modifications to balance load and axial forces within the existing bearing arrangement.

  • Re-designed worm and wheel tooth form to improve contact pattern and reduce local sliding stress in the most loaded positions.

• Drop-in housing compatibility

  • Kept shaft spacing, overall length, and mounting interface identical, enabling the OEM to use the same casting and assembly jigs.

2. Materials & Heat Treatment

• Helical input gears

  • Material: SCM415 carburizing steel, which is widely used for gears requiring a tough core and wear-resistant surface.

  • Heat treatment: Carburizing + quenching, then precision grinding; target surface hardness HRC 58–60.

• Worm gear set

  • Worm: Alloy steel (quenched and tempered, surface ground).

  • Wheel: High-strength tin-bronze alloy with good wear resistance and damping, commonly used for worm wheels in high-duty drives.

  • Tooth flanks finished to a fine surface roughness to reduce sliding friction and noise.

3. Manufacturing & Quality Control

• Accuracy & assembly

  • Helical gears manufactured to ISO / DIN Grade 6 accuracy; worm and wheel controlled for lead error and contact pattern.

  • Backlash measured and recorded for each gearbox type; assembled units are run-in on a test stand at rated torque and speed.

• Noise and durability validation

  • Sample drives tested on an indoor rig; sound pressure measured at 1 m over multiple door cycles to benchmark against the previous design.

  • Endurance tests for a subset of units simulating >200,000 cycles to verify wear behavior.

Results

After introducing the DD Gear solution, the OEM recorded the following on several pilot installations and internal rig tests:

• Noise reduction

  • Typical sound levels during door opening dropped by about 5–6 dB at 1 m, moving from the high-60s into the low-60s dB range. This aligns with published data showing helical gearsets can operate significantly quieter than spur-type arrangements under comparable conditions.

  • Subjectively, door motion was perceived as smoother and less harsh, especially at high-speed travel.

• Gearbox life & maintenance

  • On high-cycle warehouse doors, expected overhaul interval increased from 2–3 years to approximately 4–5 years, based on accelerated test results and the first wave of field feedback.

  • Backlash growth over time was slower, reducing impact at start/stop and improving perceived quality.

• Implementation

  • Because the new gearset kept the same housing and interfaces, the OEM could roll out the upgrade with minimal change to installation manuals and dealer tooling. Existing doors can be retrofitted during regular maintenance.

Typical Technical Specifications

Case Summary

By combining a helical pre-stage, carburized SCM415 steel gears, and a refined bronze worm wheel, DD Gear helped this automatic-door OEM:

• Lower operating noise to meet comfort expectations in warehouses and retail environments.

• Extend gearbox life and maintenance intervals on high-cycle doors.

• Implement the upgrade without changing housings or installation procedures.

This approach is ideal for manufacturers of industrial and commercial automatic doors who want to improve NVH and reliability while reusing their existing operator platform.

Facing noise complaints or frequent gearbox failures on your automatic doors?
Contact our engineers to discuss a custom low-noise gear solution for your next door operator platform.