A 20-ton excavator OEM upgraded its slewing pinion from hobbing (GB 7) to grinding (GB 4/DIN 5), extending slewing system life to over 5,800 hours.
industry: “Construction Machinery” product_category: “Cylindrical Gears / Custom Gears” week_cycle: “Week 3: Construction Machinery — Excavator/Crane Slewing Gears”
Key Results: A 20-ton medium excavator’s slewing drive pinion was upgraded from hobbing (GB 7) to grinding (GB 4/DIN 5) with tooth micro-profile modification. Slewing system life extended from 1,800 hours to over 5,800 hours, with slewing noise complaints reduced by 92%.
| Item | Details |
|---|---|
| Client | A medium-sized construction machinery OEM (3,000+ excavators/year) |
| Model | 20-ton medium excavator |
| Problem Component | Slewing drive gear pair (slewing ring + drive pinion) |
| Supply Term | 3-year framework agreement, 3,600+ units/year |
From 2023 to 2024, the OEM’s 20-ton medium excavator received concentrated market feedback on the following issues:
| Issue | Symptom | Impact |
|---|---|---|
| Slewing Noise | Periodic “clicking” during slewing, especially under heavy load | Increased complaints, brand reputation impact |
| Early Tooth Wear | Visible wear and pitting after 800~1,200 hours on drive pinion | Early gear replacement, increased warranty costs |
| Excessive Clearance | Meshing clearance exceeds design values after 6 months | Machine sway, reduced operating precision |
Estimated Annual Warranty Loss: Replacement costs + labor costs due to slewing system issues — approximately ¥2.8 million/year.
Geyontech’s engineering team, together with the OEM’s R&D department, conducted a systematic analysis of the failed parts:
| Inspection Item | Original Gear (Hobbed) | Analysis Conclusion |
|---|---|---|
| Surface Hardness | 52~55 HRC surface, 33~37 HRC core | Case depth too shallow (0.6mm vs 0.8~1.2mm spec) |
| Profile Error | Fα = 0.018~0.025mm | Exceeded design tolerance (≤0.015mm spec) |
| Cumulative Pitch Error | Fp = 0.045~0.060mm | Exceeded GB 7 upper limit |
| Surface Roughness | Ra 1.6~2.5μm | Too rough, accelerating initial wear |
| Contact Pattern | 45% edge loading on tooth height | Lead error + no lead modification caused stress concentration |
Initial Design Issues
├─ Insufficient precision: GB 7 hobbing cannot meet slewing drive requirements
├─ No profile modification: no addendum/profile modification was done, causing stress concentration at the tooth ends
├─ Heat treatment fluctuation: carburized layer depth and hardness uniformity are unstable
└─ Excessive fit clearance: the matching clearance between the ring gear and pinion was not pair-controlled
| Improvement Item | Original Plan | New Plan | Effect |
|---|---|---|---|
| Machining Process | Hobbing | Hobbing + Gear Grinding (worm wheel gear grinding, DIN 3-grade mother machine) | Tooth profile error reduced from 0.020mm to 0.006mm |
| Accuracy Grade | GB 7-grade | GB 4-grade (DIN 5) | Meshing smoothness greatly improved |
| Tooth Surface Roughness | Ra 1.6~2.5μm | Ra 0.4~0.6μm | Initial running-in period shortened by 60% |
| Tooth End Modification | None | Lead + addendum compound modification (K-chart modification amount 8~15μm) | End stress concentration reduced by 70% |
| Heat Treatment | Carburizing and quenching (general process) | Controlled carburizing + deep quenching (closed-loop carbon potential control) | Carburized layer depth stabilized at 0.9~1.2mm |
| Pairing Control | Batch interchangeability | Ring gear + pinion pairing numbering, controlling backlash 0.15~0.25mm | Assembly qualification rate increased to 99.5% |
┌─────────────────────────────────────────────┐
│ Material and Design Optimization Plan │
├─────────────────────────────────────────────┤
│ Pinion material: 20CrMnTi → 20CrMnTi-H (narrow hardenability band) │
│ Carburized case depth: 0.8~1.2mm (closed-loop carbon potential ±0.02%C) │
│ Surface hardness: 58~62 HRC │
│ Core hardness: 35~42 HRC │
│ Tooth root fillet optimization: R0.3→R0.6mm (reduce tooth root stress concentration) │
│ Tooth profile modification: tip relief + lead crowning (8~15μm) │
│ Matching mark: ring gear number→pinion number corresponding match │
└─────────────────────────────────────────────┘
| Product Category | Specific Product | Matching Quantity |
|---|---|---|
| Spur Cylindrical Gear | Slewing drive pinion (module m8, number of teeth z13, 20° pressure angle) | 3600 pieces/year |
| Non-standard Gears | Slewing ring gear segments (module m8, internal or external tooth structure, paired numbering) | Matched with OEM self-produced gear rings |
| Shaft Parts | Drive pinion shaft (stepped shaft, with spline connection section) | Supplied as a set |
| Test Item | Original Solution (Hobbing) | New Solution (Grinding + Modification) | Improvement |
|---|---|---|---|
| Tooth profile error Fα | 0.020mm | 0.006mm | ↑ 70% |
| Cumulative pitch error Fp | 0.052mm | 0.014mm | ↑ 73% |
| Tooth surface roughness Ra | 1.8μm | 0.5μm | ↑ 72% |
| Contact patch area ratio | 55% | 85%+ | ↑ 55% |
| Tooth root bending fatigue life | 3.2×10⁶ cycles | 8.5×10⁶ cycles | ↑ 166% |
The above data comes from measured results of the Geyang Transmission Gear Measurement Center (Klingelnberg P26) + closed power flow gear test bench.
10 prototype machines continuously operated for 6 months (cumulative 3,000 hours) under mining conditions (limestone mine), results:
| Metric | Result |
|---|---|
| Rotary abnormal noise | Zero complaints within 3,000 hours, operator feedback on rotary smoothness “significantly better than competitors” |
| Tooth surface wear | No obvious pitting on tooth surface, still retains 60% of gear grinding texture |
| Fit clearance | After 3,000 hours, backlash increased by only 0.03mm (still within design range) |
| Tooth surface hardness | Carburized layer hardness gradient normal, no signs of deep spalling |
| Metric | Before improvement | After improvement | Change |
|---|---|---|---|
| Rotary abnormal noise complaint rate | 8.2% | 0.65% | ↓ 92% |
| Gear replacement rate within warranty period | 5.7% | 0.8% | ↓ 86% |
| Average rotary system lifespan | ~1800h | >5800h | ↑ 222% |
| After-sales cost per unit | ¥930 | ¥85 | ↓ 91% |
| Customer satisfaction score | 7.2/10 | 9.4/10 | ↑ 31% |
“In 2023, the complaint rate for the slewing system of our 20-ton-class excavators once reached over 8%, seriously affecting brand reputation and dealer confidence. The Geyang Transmission team produced a complete process upgrade plan from four dimensions: gear precision, modification, heat treatment, and pairing. After mass production verification, the results exceeded expectations—the complaint rate for slewing abnormal noise dropped below 0.65%, and the slewing operation feel of the complete machine achieved a qualitative improvement.”
—— Chief Engineer of Slewing System Procurement at this OEM
| Factor | Description |
|---|---|
| Impact load | Excavator slewing frequently starts, stops, and reverses, and the tooth surface bears impact loads; insufficient precision leads to early pitting |
| Heavy-load working conditions | The slewing torque of a 20-ton-class medium excavator is about 60,000~80,000 N·m, and the tooth surface contact stress can reach 800~1200 MPa |
| Low-noise requirements | Cab noise standards are becoming stricter (<80 dB); hobbed tooth surfaces have high roughness, and high-frequency noise is significant |
| Service life requirements | The OEM’s target complete machine life is 8,000~10,000 hours, while hobbed gears show obvious wear after only 1,000~2,000 hours |
| Image position | Content description | Purpose |
|---|---|---|
| Top of article | 3D cross-section of excavator slewing system (annotating ring gear + pinion positions) | Cover image, intuitively showing the application scenario |
| Middle section | Before-and-after tooth surface comparison photos of gear grinding (hobbing Ra1.8μm vs grinding Ra0.5μm) | Visual comparison of process upgrade |
| Middle section | Schematic diagram of tooth end modification (K-chart) | Technical depth display |
| End section | Tooth surface contact pattern comparison (55% → 85%+) | Visualization of verification effect |
| End section | Life improvement line chart (1800h → 5800h) | Core data visualization |
Chinese Keywords: excavator slewing gear, slewing drive gear, construction machinery gear machining, precision gear grinding, gear modification, excavator gear supporting, slewing gear ring, gear tooth surface wear, gear heat treatment, gear life improvement
English Keywords：excavator slewing gear, slewing drive pinion, construction machinery gear, precision gear grinding, gear crowning, gear tooth modification, gear failure analysis, excavator gear supplier, case hardened gear, gear fatigue life
| Capability | Parameters |
|---|---|
| Batch Accuracy | GB 4~5 grade (DIN 4~6) |
| Maximum Gear Grinding Accuracy | DIN 3 grade |
| Machining Diameter | Maximum ≥500mm |
| Module Range | m1~m12 (cylindrical gears) |
| Inspection Equipment | Klingelnberg P26 gear measuring center + CMM + meshing tester |
| Design Software | KISSsoft / Solidworks / AutoCAD |
| Industry Experience | 13 years of gear manufacturing experience |
| Applicable Industries | Construction machinery, mining machinery, automotive, agricultural machinery, elevators, robotics |
Key Results: Upgrading 20-ton excavator slewing pinion gears from hobbing (GB 7) to precision grinding (GB 4 / DIN 5) with micro-geometry modification extended system life from 1,800 hours to 5,800+ hours and reduced swing noise complaints by 92%.
| Item | Detail |
|---|---|
| Customer | Mid-sized Chinese excavator OEM (3,000+ units/year) |
| Machine | 20-ton class medium excavator |
| Problem component | Slewing drive gear pair (ring gear + drive pinion) |
| Supply agreement | 3-year framework, 3,600+ pieces/year |
| Issue | Symptom | Impact |
|---|---|---|
| Swing noise | Periodic clicking during heavy load rotation | Customer complaints, brand damage |
| Tooth surface wear | Pitting & scuffing after 800~1,200 hours | Early replacement, higher warranty cost |
| Backlash increase | Gear clearance exceeded design limits after 6 months | Machine wobble, reduced precision |
Annual warranty loss: Approximately ¥2,800,000/year ($390,000 USD) from slewing system failures.
| Test Item | Original (Hobbed) | Finding |
|---|---|---|
| Surface hardness | 52~55 HRC, core 33~37 HRC | Shallow case depth (0.6mm vs 0.8~1.2mm required) |
| Profile deviation Fα | 0.018~0.025mm | Exceeded design tolerance (≤0.015mm) |
| Cumulative pitch Fp | 0.045~0.060mm | Exceeded GB 7 limit |
| Surface roughness Ra | 1.6~2.5μm | Accelerated initial wear |
| Contact pattern | 45% edge loading | Lead error + no crowning |
Design & Process Deficiencies
├─ Precision: GB 7 hobbing insufficient for slewing drive demands
├─ No micro-geometry modification → stress concentration at tooth ends
├─ Heat treatment variance → inconsistent case depth & hardness
└─ No pairing control → excessive backlash variation
| Item | Original | New Process | Improvement |
|---|---|---|---|
| Machining | Hobbing | Hobbing + Grinding (DIN 3 grinder) | Fα: 0.020→0.006mm |
| Precision | GB 7 | GB 4 (DIN 5) | Smoother meshing |
| Surface roughness | Ra 1.6~2.5μm | Ra 0.4~0.6μm | 60% shorter run-in period |
| Micro-modification | None | Tip relief + Crowning (8~15μm K-chart) | 70% less edge stress |
| Heat treatment | Standard carburizing | Closed-loop controlled carburizing | Case depth 0.9~1.2mm stable |
| Matching control | Random interchange | Matched pair marking (backlash 0.15~0.25mm) | 99.5% assembly pass rate |
┌─────────────────────────────────────────────────────┐
│ Material & Design Optimization │
├─────────────────────────────────────────────────────┤
│ Pinion material: 20CrMnTi → 20CrMnTi-H (narrow H-band) │
│ Case depth: 0.8~1.2mm (closed-loop ±0.02%C) │
│ Surface hardness: 58~62 HRC │
│ Core hardness: 35~42 HRC │
│ Root radius: R0.3→R0.6mm (reduced stress concentration) │
│ Modification: Tip relief + lead crowning (8~15μm) │
│ Pairing: Ring gear ID → pinion ID matched │
└─────────────────────────────────────────────────────┘
| Category | Product | Annual Volume |
|---|---|---|
| Spur Gears | Slewing drive pinion (m8, z13, 20°PA) | 3,600 pcs/yr |
| Custom Gears | Ring gear segments (m8, internal/external teeth) | OEM-supplied |
| Shaft Parts | Drive pinion shaft (stepped shaft with spline) | Matched supply |
| Parameter | Original (Hobbed) | New (Ground + Modified) | Improvement |
|---|---|---|---|
| Profile deviation Fα | 0.020mm | 0.006mm | ↑ 70% |
| Cumulative pitch Fp | 0.052mm | 0.014mm | ↑ 73% |
| Surface roughness Ra | 1.8μm | 0.5μm | ↑ 72% |
| Contact pattern ratio | 55% | 85%+ | ↑ 55% |
| Bending fatigue life | 3.2×10⁶ cycles | 8.5×10⁶ cycles | ↑ 166% |
Data from Klingelnberg P26 gear measuring center + power-circulating gear test rig.
10 prototype machines operated 6 months (3,000 hours) in limestone mine conditions:
| Metric | Result |
|---|---|
| Swing noise | Zero complaints in 3,000 hours |
| Tooth surface wear | No visible pitting — 60% of grinding marks remained |
| Backlash stability | Only 0.03mm increase (within design spec) |
| Case hardness | No deep-layer spalling detected |
| Metric | Before | After | Change |
|---|---|---|---|
| Swing noise complaint rate | 8.2% | 0.65% | ↓ 92% |
| Gear replacement rate (warranty) | 5.7% | 0.8% | ↓ 86% |
| Average slewing system life | ~1,800h | >5,800h | ↑ 222% |
| Per-unit warranty cost | ¥930 | ¥85 | ↓ 91% |
| Customer satisfaction score | 7.2/10 | 9.4/10 | ↑ 31% |
“In 2023, our 20-ton excavator swing noise complaint rate exceeded 8%, severely impacting our brand reputation and dealer confidence. Geyontech’s engineering team delivered a complete process upgrade addressing precision, micro-geometry, heat treatment, and pairing control. The results exceeded expectations — complaint rate dropped to 0.65% and the machine’s swing operation feel improved dramatically.”
— Chief Engineer, Slewing System Procurement, Customer OEM
| Factor | Explanation |
|---|---|
| Impact loading | Frequent start/stop/reverse in excavator swing creates shock loads |
| Heavy duty | 20-ton excavator swing torque: 60,000~80,000 N·m, contact stress 800~1,200 MPa |
| Noise requirements | Cab noise standards tightening (<80 dB), hobbed surface roughness causes high-frequency noise |
| Life targets | OEM targets 8,000~10,000 hours machine life; hobbed gears show wear at 1,000~2,000 hours |
| Cost-benefit | Grinding adds 40~60% per-piece cost but reduces warranty cost by 90%+ — significantly lower total lifecycle cost |
| Position | Content | Purpose |
|---|---|---|
| Top | 3D cutaway of excavator swing drive showing ring gear + pinion | Cover image, application visualization |
| Middle | Side-by-side comparison: hobbed surface (Ra1.8μm) vs ground (Ra0.5μm) | Process upgrade visual proof |
| Middle | K-chart diagram showing tip relief + crowning profile | Technical depth demonstration |
| Bottom | Contact pattern comparison (55% → 85%+) | Validation visualization |
| Bottom | Life improvement chart (1,800h → 5,800h) | Core data visualization |
| Capability | Specification |
|---|---|
| Batch precision | GB 4~5 (DIN 4~6) |
| Max ground precision | DIN 3 |
| Max gear diameter | ≥500 mm |
| Module range | m1~m12 (cylindrical) |
| Inspection | Klingelnberg P26 + CMM + Hardness tester + Gear meshing tester |
| Design tools | KISSsoft / Solidworks / AutoCAD |
| Industry experience | 13 years |
| Served industries | Construction machinery, mining, automotive, agriculture, elevator, robotics |
Geyontech · 13 years of precision-gear experience in our engineering team · One-stop gear transmission solutions from design to inspection
Geyontech — engineering team with 13 years of precision-gear experience (company established in 2020), delivering end-to-end gear drive solutions from design to inspection.
+86 18002857601 | www.geyontech.com
Upload a 2D/3D drawing (STEP, DXF, PDF) — we reply with a quote and lead time.