{"id":1099,"date":"2026-06-24T03:44:33","date_gmt":"2026-06-24T03:44:33","guid":{"rendered":"https:\/\/planetary-gearboxes.com\/?p=1099"},"modified":"2026-06-24T05:50:26","modified_gmt":"2026-06-24T05:50:26","slug":"slewing-drive-planetary-gearbox-for-tbm-cutterhead","status":"publish","type":"post","link":"https:\/\/planetary-gearboxes.com\/th\/slewing-drive-planetary-gearbox-for-tbm-cutterhead\/","title":{"rendered":"Slewing Drive Planetary Gearbox for TBM Cutterhead"},"content":{"rendered":"
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\"Slewing<\/p>\n
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Korea Ever-Power \u00b7 Application Engineering \u00b7 Tunnel Boring Machines<\/p>\n

Slewing Drive Planetary Gearbox for TBM Cutterhead<\/h1>\n

No other slewing application combines this much torque, this much confinement, and this much consequence of failure. The TBM cutterhead drive system generates 10,000 to 50,000 kN\u00b7m of torque from 8 to 20 individual slewing drive planetary gearboxes \u2014 and every one of them must be replaced, if it fails, from inside a tunnel with no overhead crane access.<\/p>\n

Browse Slewing Drive Planetary Gearboxes \u2192<\/a><\/p>\n<\/div>\n<\/div>\n<\/section>\n

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How the TBM Cutterhead Drive System Works \u2014 8 to 20 Drives Sharing One Ring Gear<\/h2>\n

The TBM cutterhead is a massive steel disc \u2014 3 to 17 metres in diameter \u2014 fitted with disc cutters (for rock) or cutting teeth and scrapers (for soft ground). This disc must rotate continuously as the TBM advances, and the torque required to turn it against the rock face is enormous: 10,000 to 50,000 kN\u00b7m for large-diameter rock TBMs. No single \u0e0a\u0e38\u0e14\u0e40\u0e01\u0e35\u0e22\u0e23\u0e4c\u0e14\u0e32\u0e27\u0e40\u0e04\u0e23\u0e32\u0e30\u0e2b\u0e4c\u0e02\u0e31\u0e1a\u0e40\u0e04\u0e25\u0e37\u0e48\u0e2d\u0e19\u0e01\u0e32\u0e23\u0e2b\u0e21\u0e38\u0e19<\/a> can generate this torque alone.<\/p>\n

Instead, the cutterhead is fitted with a large internal ring gear, and 8 to 20 individual slewing drives are mounted around the TBM shield \u2014 each driving a pinion that meshes with this ring gear. The drives share the total torque equally in theory, or proportionally in practice depending on individual drive condition and hydraulic or electric balance. This multi-drive architecture is unique among all slewing applications \u2014 no crane, no excavator, and no antenna system uses this many independent drives on a single ring gear.<\/p>\n

The load sharing between drives is not automatic \u2014 it must be actively managed. In a hydraulic drive system, the oil flow to each motor is metered through a flow divider or controlled by individual proportional valves. In an electric drive system, each motor is controlled by its own variable-frequency drive (VFD) with current-limiting to prevent any single motor from absorbing more than its proportional share. When one drive wears faster than the others (due to its position relative to ground hardness variations), it draws less current or accepts less flow \u2014 and the adjacent drives must compensate. The hydraulic or electrical balance system is as critical to long-term drive life as the gearbox itself.<\/p>\n

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Redundancy mathematics:<\/strong> If one drive in a 12-drive system fails, the remaining 11 each absorb an additional 9% of the load \u2014 within the 1.5x safety factor. Two simultaneous failures bring the per-drive overload to 18% \u2014 still manageable. Three failures reach 27%, approaching the safety factor limit and requiring immediate advance rate reduction. The multi-drive architecture is the primary protection a TBM has against underground shutdown.<\/p>\n<\/div>\n

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The load sharing between drives is not automatic \u2014 it must be actively managed. In a hydraulic drive system, the oil flow to each motor is metered through a flow divider or controlled by individual proportional valves. In an electric drive system, each motor is controlled by its own variable-frequency drive with current-limiting to prevent any single motor from absorbing more than its proportional share. When one drive wears faster than the others (due to its position relative to ground hardness variations), it draws less current or accepts less flow \u2014 and the adjacent drives must compensate.<\/p>\n

The pinion-ring gear meshing arrangement also affects load sharing. If the pinions are evenly spaced around the ring gear, each pinion meshes with a different section of the ring \u2014 and any eccentricity or tooth-pitch error in the ring gear produces a systematic load variation that repeats with each cutterhead revolution. High-quality ring gears with DIN Class 6 tooth pitch accuracy are essential for uniform load sharing. A ring gear with Class 8 pitch accuracy can produce per-pinion load variations of 15 to 25% above the mean \u2014 equivalent to losing 2 to 3 drives worth of capacity from the tooth-error alone.<\/p>\n<\/div>\n

\"ZR45<\/div>\n<\/div>\n<\/section>\n

\"Slewing<\/p>\n

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TBM Types and Cutterhead Drive Requirements<\/h2>\n

The cutterhead drive specification depends fundamentally on the TBM type \u2014 each designed for a different ground condition and each imposing different demands on the slewing drive.<\/p>\n

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Hard Rock TBM (Open or Gripper Type)<\/div>\n

Cuts through rock with UCS of 50 to 300+ MPa using disc cutters. Cutterhead torque is very high (15,000 to 50,000 kN\u00b7m) but relatively steady. Disc cutters generate radial forces producing continuous low-frequency vibration transmitted through the ring gear. Drives operate in open (unpressurised) conditions \u2014 no slurry sealing is required, but rock dust and groundwater seepage are present.<\/p>\n<\/div>\n

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EPB (Earth Pressure Balance) TBM<\/div>\n

Operates in soft ground by maintaining a pressurised chamber of conditioned soil behind the cutterhead. Torque is lower (3,000 to 15,000 kN\u00b7m) but the drives operate behind a pressurised bulkhead at 1 to 5 bar. Seal integrity is critical \u2014 any leak allows pressurised muck to enter the gearbox, and any loss of face pressure risks ground collapse. The conditioned soil is highly abrasive and chemically aggressive (pH 10 to 12).<\/p>\n<\/div>\n

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Slurry TBM<\/div>\n

Uses pressurised bentonite slurry at 2 to 6 bar to support the face. The slurry is extremely abrasive (rock fragments at high velocity) and corrosive. Drive seals must withstand both the pressure and the abrasion simultaneously for 2,000 to 5,000 hours between seal service intervals \u2014 the most demanding seal environment of any slewing drive application.<\/p>\n<\/div>\n<\/div>\n<\/section>\n

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Variable Ground Torque \u2014 From Soft Clay to Hard Granite in the Same Tunnel<\/h2>\n

Unlike every other slewing drive application \u2014 where the load is predictable and relatively constant \u2014 the TBM cutterhead torque varies continuously and unpredictably as the ground conditions change along the tunnel alignment. A single tunnel may pass through clay, sand, gravel, sandstone, limestone, and granite \u2014 each requiring a different cutterhead torque, a different rotation speed, and a different advance rate.<\/p>\n

\n\n\n\n\n\n\n\n
Ground Type<\/th>\nUCS (MPa)<\/th>\nTorque (kN\u00b7m)<\/th>\nRPM<\/th>\nPer Drive (12)<\/th>\n<\/tr>\n<\/thead>\n
Soft clay \/ silt<\/td>\n0.1 \u2013 1<\/td>\n3k \u2013 8k<\/td>\n4 \u2013 10<\/td>\n250 \u2013 670<\/td>\n<\/tr>\n
Sandstone \/ limestone<\/td>\n20 \u2013 80<\/td>\n10k \u2013 25k<\/td>\n3 \u2013 6<\/td>\n830 \u2013 2,080<\/td>\n<\/tr>\n
Hard granite<\/td>\n100 \u2013 300<\/td>\n25k \u2013 50k<\/td>\n1 \u2013 3<\/td>\n2,080 \u2013 4,170<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n
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Mixed-face tunnelling \u2014 the worst case:<\/strong> The most damaging condition is mixed-face ground \u2014 where the cutterhead encounters hard rock on one side and soft soil on the other simultaneously. This produces unbalanced radial forces that alternate with each revolution, loading the drives on one side at 1.5 to 2.5 times the average while the opposite side runs near zero. This cyclic unbalanced loading produces fatigue damage at rates 3 to 5 times faster than uniform-ground boring.<\/p>\n<\/div>\n

Torque Calculation \u2014 10-Metre Rock TBM, 12 Drives<\/h3>\n
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Given:<\/div>\n
\u00a0\u00a0Diameter: 10,000 mm \u00b7 Rock: 150 MPa granite<\/div>\n
\u00a0\u00a0Disc cutters: 52 x 483 mm \u00b7 Thrust\/disc: 250 kN<\/div>\n
Cutterhead torque (k=0.06, R_avg=2.8 m):<\/div>\n
\u00a0\u00a0T = 52 x 250,000 x 0.06 x 2.8 = 2,184 kN\u00b7m<\/strong><\/div>\n
Mixed-face factor (1.8x) \u2192 per drive (12):<\/div>\n
\u00a0\u00a0T_max = 2,184 x 1.8 \/ 12 = 328 kN\u00b7m per drive<\/strong><\/div>\n
\u2192 Korea Ever-Power 400 kN\u00b7m drive \u2714 (SF=1.22)<\/div>\n<\/div>\n<\/div>\n

The rolling coefficient (k) varies significantly with rock type and disc cutter condition. Fresh disc cutters on hard granite produce k values of 0.05 to 0.07. As the cutters wear (the carbide ring develops flat spots), the rolling coefficient increases to 0.08 to 0.12 \u2014 increasing the cutterhead torque by 40 to 70% from fresh-cutter to worn-cutter condition. The slewing drive must be sized for the worn-cutter torque, not the fresh-cutter torque \u2014 because disc cutter replacement intervals are typically 500 to 2,000 boring hours, and the last 20% of each cutter life produces the highest rolling resistance. This worn-cutter design condition is unique to TBM drives \u2014 no other slewing application has a tool-wear variable that changes the drive torque by 40 to 70% over a predictable service interval.<\/p>\n<\/section>\n

\"Precision<\/p>\n

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Confined-Space Maintenance \u2014 Design Driven by Replacement Logistics<\/h2>\n

On every other slewing drive application, a failed drive can be replaced using a mobile crane or forklift. On a TBM, the slewing drives are inside the shield \u2014 buried 20 to 40 metres below ground, accessible only through a tunnel that may be 2 to 10 kilometres long. Every tool, every replacement part, and every technician must travel through this tunnel.<\/p>\n

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5 \u0e15\u0e31\u0e19<\/div>\n
max lifting \u2014 chain hoists only<\/div>\n<\/div>\n
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600 mm<\/div>\n
max wrench swing arc<\/div>\n<\/div>\n
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8\u201316 h<\/div>\n
replacement target time<\/div>\n<\/div>\n<\/div>\n

TBM cutterhead slewing drive planetary gearboxes<\/a> are designed for replacement logistics as much as for torque capacity. The mounting interface, coupling geometry, oil connection routing, and fastener accessibility are all optimised for the 600 mm wrench arc, the 5-tonne chain hoist, and the 8-hour replacement window. Every hour the TBM is stopped for drive maintenance costs USD 15,000 to 50,000 in lost advance rate and project delay.<\/p>\n

The replacement procedure itself is engineered as carefully as the drive: the mounting bolt pattern is designed for hydraulic torque wrenches (not impact wrenches, which cannot be used reliably in the confined arc). The coupling between the motor and the gearbox uses a splined interface that self-aligns during installation \u2014 eliminating the need for precision alignment with dial indicators in a space where visibility and access are severely limited. The oil fill and drain ports are positioned for gravity filling from above and complete draining from below, using flexible hoses that can reach around adjacent equipment. These logistics details \u2014 invisible in a surface-mounted specification \u2014 determine whether a drive replacement takes 8 hours (well-designed) or 24 hours (poorly designed).<\/p>\n

Most TBM contractors carry 1 to 2 complete spare drives inside the tunnel backup gantry \u2014 pre-filled with oil, pre-tested, and ready for installation. The spare drive strategy is a critical part of the TBM logistics plan and should be specified with the initial drive order. A spare drive stored at the tunnel portal is 2 to 10 kilometres and 2 to 4 hours of transport away from the machine \u2014 too far for time-critical replacements during a difficult ground transition.<\/p>\n

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The drive weight is a critical constraint. Each unit must be transportable on the tunnel rail system (typically in a materials car with a 5-tonne payload limit) and liftable by the chain hoists mounted on the shield roof rails. This limits the maximum individual drive weight to approximately 2,500 to 3,000 kg \u2014 regardless of the torque requirement. For very large TBMs where the per-drive torque exceeds what a 3,000 kg unit can deliver, the solution is to add more drives (increasing from 12 to 16 or 20) rather than making each drive heavier. This scaling approach preserves the confined-space replacement capability while meeting the total torque requirement through additional parallel units.<\/p>\n<\/div>\n

\"Compact<\/div>\n<\/div>\n<\/section>\n
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Seal Engineering for Pressurised TBMs<\/h2>\n

On hard rock TBMs, sealing is conventional dust and water exclusion. On EPB and slurry TBMs, the drives operate behind a pressurised bulkhead at 1 to 6 bar. The drive seal must prevent pressurised, abrasive, chemically aggressive medium from entering the gearbox \u2014 continuously, for 2,000 to 5,000 hours between service intervals.<\/p>\n

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Lip Seals (Hard Rock TBMs)<\/div>\n

Multiple tandem lips (3 to 5) for progressive dust and water exclusion. Life: 3,000 to 6,000 hours. Not suitable above 0.5 bar.<\/p>\n<\/div>\n

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Mechanical Face Seals (EPB TBMs)<\/div>\n

Silicon carbide or tungsten carbide faces pressed by springs. Withstands 3 to 6 bar. Wear rate: 0.01 to 0.03 mm per 1,000 hours. Life: 4,000 to 8,000 hours. Seal chamber pre-filled with clean grease at positive pressure.<\/p>\n<\/div>\n

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Pressurised Labyrinth + Grease Barrier (Slurry TBMs)<\/div>\n

Multi-stage labyrinth with continuous grease injection at 0.5 to 1.0 bar above face pressure. Consumption: 0.5 to 2.0 L\/h per drive. A 12-drive slurry TBM consumes 6 to 24 L\/h of barrier grease \u2014 a significant cost, but far less than a gearbox failure from slurry ingestion.<\/p>\n

The seal selection directly affects the operational cost model of the TBM. Mechanical face seals have lower running cost (no grease consumption) but higher replacement cost and require skilled technicians for seal face lapping. Pressurised labyrinth seals have higher running cost (continuous grease consumption at USD 3 to 8 per litre) but are more tolerant of misalignment and can be serviced by general maintenance personnel. For a 12-drive slurry TBM operating 6,000 hours per year at 1 L\/h per drive, the annual grease cost is 72,000 litres x USD 5 = USD 360,000 \u2014 a significant but predictable operating expense compared to the unpredictable cost of a mechanical seal failure and consequent gearbox flooding.<\/p>\n

The seal monitoring strategy differs by seal type. Mechanical face seals can be monitored by measuring the grease leakage rate at the seal drain port \u2014 a sudden increase in leakage indicates face wear approaching the replacement threshold. Pressurised labyrinth seals can be monitored by tracking the grease consumption rate \u2014 a decrease in consumption at constant injection pressure indicates a partial blockage of the labyrinth (from contamination build-up), while an increase indicates labyrinth gap widening from wear. Both monitoring approaches provide 500 to 1,000 hours of advance warning before the seal condition becomes critical \u2014 sufficient time to schedule a replacement during a planned maintenance shift rather than an emergency stop.<\/p>\n<\/div>\n<\/div>\n<\/section>\n

\"Korea<\/p>\n

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Three Failure Modes Specific to TBM Cutterhead Slewing Drives<\/h2>\n
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1<\/div>\n
Torque spike from boulder encounter exceeding the drive shock rating<\/div>\n<\/div>\n

When the cutterhead encounters an isolated boulder in softer ground, the disc cutter transmits a torque spike of 2 to 4 times the average \u2014 lasting 0.1 to 0.5 seconds. The planetary gears must absorb this shock without tooth fracture. Repeated encounters (10 to 50 per metre in glacial till) accumulate fatigue far faster than uniform-ground assumptions. The torque spike propagates through the pinion-ring mesh and into the planetary stages \u2014 loading the sun gear, planet gears, and carrier pins with an impulse that exceeds the steady-state design torque. The gear tooth root stress during a 3x spike can approach the yield strength of standard case-hardened steel \u2014 and if the spike coincides with an existing fatigue crack from previous events, the tooth can fracture catastrophically, shedding fragments into the gear mesh that damage adjacent teeth and bearings in a cascade failure.<\/p>\n

Prevention: DIN 3990 Method B dynamic rating. 18CrNiMo7-6 steel, 58\u201362 HRC. Torque monitoring per drive.<\/div>\n<\/div>\n
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2<\/div>\n
Seal failure from pressurised slurry ingestion<\/div>\n<\/div>\n

On EPB and slurry TBMs, a catastrophic seal failure can fill the gearbox with abrasive slurry under 2 to 6 bar within hours \u2014 condemning the entire gear set and all bearings in a single event. Unlike gradual leaks (detectable through oil analysis), a catastrophic failure is immediate and total. The replacement cost is compounded by 8 to 16 hours of TBM downtime at USD 15,000 to 50,000 per hour.<\/p>\n

Prevention: Mechanical face or pressurised labyrinth seals (mandatory for EPB\/slurry). Leak sensors at seal drain. Oil sampling every 500 hours.<\/div>\n<\/div>\n
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3<\/div>\n
Cutterhead jam requiring reverse rotation under full stall torque<\/div>\n<\/div>\n

When the cutterhead jams, the operator must reverse it to free the obstruction. The reverse torque loads the opposite (non-driving) tooth flank \u2014 a surface with less fatigue resistance from less contact during normal forward rotation. Multiple jam-and-reverse cycles per shift in mixed-face ground produce accelerated reverse-flank spalling within 2,000 to 4,000 hours. The problem is compounded by the fact that the reverse torque is often applied at full system pressure (the operator pushes the hydraulic relief valve to maximum to free the jam) \u2014 generating torque peaks that exceed the normal forward-cutting maximum by 10 to 30%. This combination of less-hardened contact surface and higher-than-normal torque makes reverse-flank failure the most common gear damage mode in mixed-face TBM tunnelling.<\/p>\n

Prevention: Symmetric tooth profile (both flanks same quality). Limit reverse to 80% of forward torque. Log all reversals.<\/div>\n<\/div>\n<\/div>\n<\/section>\n
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Slewing Drive Planetary Gearbox for TBM Cutterhead \u2014 Frequently Asked Questions<\/h2>\n
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How many slewing drives does a typical TBM use?<\/h3>\n

8 to 20. Small TBMs (3\u20136 m) use 8 to 10. Medium (6\u201310 m) use 10 to 14. Large (10\u201317 m) use 14 to 20. Total power: 1,500 to 15,000 kW. Each unit weighs 800 to 3,000 kg \u2014 sized for the 5-tonne chain hoist replacement constraint.<\/p>\n<\/div>\n

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What is the typical service life?<\/h3>\n

5,000 to 15,000 boring hours (5 to 15 km of tunnel). Soft ground: up to 15,000 h. Hard rock with boulders: 5,000 to 8,000 h. Mixed-face with frequent jams: 4,000 to 6,000 h. Oil analysis at 500-hour intervals is the most effective early warning.<\/p>\n<\/div>\n

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How long does it take to replace one drive inside the TBM?<\/h3>\n

8 to 16 hours with 2 to 3 technicians. The 600 mm wrench-swing limitation adds 30 to 50% compared to surface-mounted replacement. Most operators carry 1 to 2 spare drives inside the tunnel backup system for rapid swap during planned maintenance shifts.<\/p>\n<\/div>\n

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Can the TBM continue boring if one drive fails?<\/h3>\n

Yes \u2014 this is the primary advantage of the multi-drive architecture. One failed drive in a 12-drive system increases each remaining unit load by 9%. The TBM continues at 5 to 12% reduced advance rate until the next planned maintenance window.<\/p>\n<\/div>\n

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What seal type is required for a slurry TBM?<\/h3>\n

Mechanical face seals (carbide faces, 3\u20136 bar rated) or pressurised labyrinth seals with continuous grease injection (0.5\u20132.0 L\/h per drive). Standard lip seals fail within days under 2+ bar of abrasive slurry pressure. The choice depends on maximum face pressure, abrasive content, and acceptable grease consumption rate.<\/p>\n<\/div>\n

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Does Korea Ever-Power supply cutterhead drives for TBMs?<\/h3>\n

Yes. 3 to 4 stage planetary reductions, 18CrNiMo7-6 case-hardened gears (DIN 3990 Method B), pressurised mechanical face and labyrinth seal options, confined-space mounting interfaces. Available from 200 to 4,500 kN\u00b7m per unit for 3 to 17 metre TBMs. Provide the TBM manufacturer, diameter, ground conditions, and maximum face pressure for a matched specification.<\/p>\n<\/div>\n<\/div>\n<\/section>\n

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TBM Cutterhead Drives \u2014 Shock-Rated, Pressure-Sealed, Tunnel-Replaceable<\/div>\n

Korea Ever-Power provides TBM cutterhead slewing drive planetary gearboxes from 200 to 4,500 kN\u00b7m per unit with shock-rated gears, pressurised seals, and confined-space mounting.<\/p>\n<\/div>\n

View Slewing Drive Range \u2192<\/a><\/p>\n
sales@planetary-gearboxes.com<\/div>\n<\/div>\n<\/div>\n<\/section>\n

\u0e1a\u0e23\u0e23\u0e13\u0e32\u0e18\u0e34\u0e01\u0e32\u0e23: Cxm<\/p>\n<\/div>","protected":false},"excerpt":{"rendered":"

Korea Ever-Power \u00b7 Application Engineering \u00b7 Tunnel Boring Machines Slewing Drive Planetary Gearbox for TBM Cutterhead No other slewing application combines this much torque, this much confinement, and this much consequence of failure. The TBM cutterhead drive system generates 10,000 to 50,000 kN\u00b7m of torque from 8 to 20 individual slewing drive planetary gearboxes \u2014 […]<\/p>","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_et_pb_use_builder":"","_et_pb_old_content":"","_et_gb_content_width":"","footnotes":""},"categories":[965],"tags":[],"class_list":["post-1099","post","type-post","status-publish","format-standard","hentry","category-application-and-technical-guid"],"_links":{"self":[{"href":"https:\/\/planetary-gearboxes.com\/th\/wp-json\/wp\/v2\/posts\/1099","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/planetary-gearboxes.com\/th\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/planetary-gearboxes.com\/th\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/th\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/th\/wp-json\/wp\/v2\/comments?post=1099"}],"version-history":[{"count":5,"href":"https:\/\/planetary-gearboxes.com\/th\/wp-json\/wp\/v2\/posts\/1099\/revisions"}],"predecessor-version":[{"id":1113,"href":"https:\/\/planetary-gearboxes.com\/th\/wp-json\/wp\/v2\/posts\/1099\/revisions\/1113"}],"wp:attachment":[{"href":"https:\/\/planetary-gearboxes.com\/th\/wp-json\/wp\/v2\/media?parent=1099"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/th\/wp-json\/wp\/v2\/categories?post=1099"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/th\/wp-json\/wp\/v2\/tags?post=1099"}],"curies":[{"name":"\u0e14\u0e31\u0e1a\u0e40\u0e1a\u0e34\u0e25\u0e22\u0e39\u0e1e\u0e35","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}