{"id":675,"date":"2026-05-29T05:47:48","date_gmt":"2026-05-29T05:47:48","guid":{"rendered":"https:\/\/planetary-gearboxes.com\/?p=675"},"modified":"2026-05-29T05:47:48","modified_gmt":"2026-05-29T05:47:48","slug":"planetary-gearbox-overheating-causes-diagnosis","status":"publish","type":"post","link":"https:\/\/planetary-gearboxes.com\/ja\/planetary-gearbox-overheating-causes-diagnosis\/","title":{"rendered":"\u904a\u661f\u6b6f\u8eca\u6a5f\u69cb\u306e\u904e\u71b1 \u2015 \u6839\u672c\u539f\u56e0\u3001\u8a3a\u65ad\u3001\u304a\u3088\u3073\u4e88\u9632"},"content":{"rendered":"
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<\/p>\n

\"planetary<\/p>\n
\n
Root Cause Analysis \u00b7 Thermal Calculation \u00b7 5-Min Diagnosis Protocol<\/div>\n

Planetary Gearbox Overheating \u2014
\nRoot Causes, Diagnosis and Prevention<\/h1>\n

Every 10\u00b0C rise above rated operating temperature halves the remaining service life<\/strong> of a precision planetary gearbox \u2014 this is not an approximation but a direct consequence of the Arrhenius equation governing lubricant degradation and gear surface fatigue. Korean engineers who identify overheating early and correct its root cause prevent failures worth months of unplanned downtime; those who address the symptom (adding cooling) without finding the cause watch the gearbox fail again within weeks.<\/p>\n

View EP-AB Precision Series \u2192
\n<\/a><\/p>\n<\/div>\n<\/section>\n

<\/p>\n

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How Overheating Destroys a Precision Planetary Gearbox \u2014 The Arrhenius Mechanism<\/h2>\n
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\n

A planetary gearbox overheating event is not simply uncomfortable \u2014 it initiates a cascade of degradation mechanisms that accelerate failure at every level of the gearbox simultaneously. Understanding exactly what happens inside the housing when temperature exceeds rated limits explains why the Arrhenius-based life prediction is so unforgiving, and why even brief temperature excursions compound over a machine’s lifetime.<\/p>\n

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\u2460 Grease oxidation and base oil separation<\/strong><\/p>\n

Above 80\u201390\u00b0C, the base oil in sealed grease begins to separate from the thickener structure (oil bleeding). Once separated, the base oil migrates to the lowest point in the housing \u2014 often away from the gear mesh contact zone. The gear teeth begin running with reduced lubrication, increasing metal-to-metal contact and accelerating surface fatigue. This process is irreversible: once the grease structure has degraded, cooling the gearbox back to normal temperature does not restore the lubrication film.<\/p>\n<\/div>\n

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\u2461 Bearing raceway surface fatigue<\/strong><\/p>\n

Ball and roller bearing steel hardness begins to decrease above 120\u00b0C due to tempering of the hardened raceway surface. Hardness reduction by even 2 HRC units can halve the bearing’s fatigue life. At 150\u00b0C, case-hardened bearing steel loses structural integrity fast enough to produce spalling within hours of operation.<\/p>\n<\/div>\n

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\u2462 Gear tooth surface hardness reduction<\/strong><\/p>\n

Case-hardened gear teeth (typically 58\u201362 HRC surface hardness) follow the same tempering curve as bearings. Sustained temperatures above 120\u00b0C initiate micro-structural changes in the gear tooth surface that reduce hardness, lower wear resistance, and accelerate pitting fatigue \u2014 the primary gear tooth failure mode in Korean high-cycle servo applications.<\/p>\n<\/div>\n

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\u2463 Shaft seal deterioration<\/strong><\/p>\n

NBR and FKM lip seals have operating temperature limits of 100\u2013120\u00b0C. Above these limits, seal lip elasticity is permanently reduced \u2014 the seal no longer exerts sufficient radial force on the shaft to maintain contact. Grease begins to migrate out through the seal; external contamination migrates in. This failure mode typically manifests as visible grease weeping at the output shaft seal.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

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<\/p>\n

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Arrhenius Life Reduction \u2014 Every 10\u00b0C Halves Life<\/p>\n

L(T) = L\u2080 \u00d7 e^(\u2212E\u2090\/kT)
\n(simplified: life halves per 10\u00b0C rise)At rated temp T\u2080 = 70\u00b0C: Life = 100%
\nAt T\u2080 + 10\u00b0C = 80\u00b0C: Life = 50%
\nAt T\u2080 + 20\u00b0C = 90\u00b0C: Life = 25%
\nAt T\u2080 + 30\u00b0C = 100\u00b0C: Life = 12.5%
\nAt T\u2080 + 40\u00b0C = 110\u00b0C: Life = 6.25%
\nAt T\u2080 + 50\u00b0C = 120\u00b0C: Life = 3.1%<\/div>\n
A gearbox rated for 20,000 hours running at 120\u00b0C instead of 70\u00b0C will fail after only 625 hours \u2014 3.1% of its rated life. A 50\u00b0C temperature excursion compounds through the Arrhenius exponent to a 32\u00d7 life reduction.<\/div>\n<\/div>\n
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Normal operating temperature range<\/div>\n

Korea Ever-Power EP series rated operating range: \u221210\u00b0C to +90\u00b0C (standard grease). Normal steady-state housing temperature during continuous rated-load operation: ambient + 20\u201340\u00b0C. At Korean factory ambient 25\u00b0C \u2192 housing should stabilise at 45\u201365\u00b0C. Consistent housing temperature above 80\u00b0C warrants investigation.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n

<\/p>\n

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Root Cause 1 \u2014 Input Speed Exceeds Rated Maximum<\/h2>\n
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Every Korea Ever-Power EP gearbox has a maximum input speed rating \u2014 the highest rotational speed at which the internal gear mesh, bearing system, and lubrication can maintain a normal operating temperature. Exceeding this speed does not immediately fracture gears; instead, it produces a rapid temperature rise driven by two mechanisms operating simultaneously.<\/p>\n

First, bearing centrifugal forces increase with the square of rotation speed \u2014 at double the rated speed, centrifugal forces on the bearing balls quadruple, squeezing the lubricant film between balls and raceway and increasing friction heat by the same factor. Second, gear mesh frequency (the number of tooth-to-tooth engagements per second) increases linearly with speed \u2014 at double speed, every heat-generating tooth engagement occurs twice as often, doubling the mesh heat generation per unit time.<\/p>\n

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BEARING HEAT vs INPUT SPEED<\/p>\n

Q_bearing \u221d n\u00b2 (centrifugal) + n (drag)
\nAt 1\u00d7 rated speed: Q = 1.0\u00d7 (normal)
\nAt 1.5\u00d7 rated speed: Q \u2248 2.5\u00d7 (50% overspeed)
\nAt 2\u00d7 rated speed: Q \u2248 5\u00d7 (double rated)Example: EP-AB090, n_rated = 3,000 rpm
\nAt n = 4,500 rpm (1.5\u00d7 rated):
\nBearing heat \u2248 2.5\u00d7 normal
\nHousing temp \u2248 25 + 2.5\u00d7(45) = 137\u00b0C \u26a0<\/span>
\n(assuming 45\u00b0C normal temp rise above ambient)<\/div>\n<\/div>\n

Common trigger in Korean industry:<\/strong> Variable-frequency drives (VFDs) allow servo motors to run above their nameplate speed. A Korean packaging machine upgraded from 80 CPM to 120 CPM by increasing VFD frequency from 50 Hz to 75 Hz runs the motor \u2014 and the gearbox input shaft \u2014 at 1.5\u00d7 rated speed. Unless the gearbox was originally specified with headroom for this speed increase, the gearbox begins overheating within days of the upgrade.<\/p>\n

Prevention: <\/strong>
\nBefore increasing VFD frequency above 50 Hz on an existing gearbox, confirm the new motor speed does not exceed the gearbox’s rated maximum input speed. Korea Ever-Power EP-AB maximum input speed varies by frame size (typically 3,000\u20135,000 rpm). Request the specific maximum speed for your frame and ratio combination before approving any VFD frequency increase.<\/span><\/div>\n<\/div>\n
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Overheating Diagnosis \u2014 Root Cause 1 Signature<\/p>\n

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\u2713<\/span><\/p>\n

Heat develops within minutes<\/strong> of startup<\/div>\n<\/div>\n
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\u2713<\/span><\/p>\n

Heat concentrated at bearing locations<\/strong> (front\/rear caps)<\/div>\n<\/div>\n
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\u2713<\/span><\/p>\n

Noise increases (bearing whine) before housing becomes hot<\/div>\n<\/div>\n
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\u2713<\/span><\/p>\n

Problem started after VFD frequency change<\/strong> or motor upgrade<\/div>\n<\/div>\n
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\u2717<\/span><\/p>\n

Problem existed before any recent machine changes<\/div>\n<\/div>\n<\/div>\n
Fix:<\/strong> Reduce VFD frequency, downgrade motor to correct RPM, or replace gearbox with a higher-speed rated frame\/series.<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n

<\/p>\n

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Root Cause 2 \u2014 Output Torque Overload and the Thermal Power Calculation<\/h2>\n
\n
\n

Torque overload generates heat through the direct relationship between friction losses and transmitted power. A planetary gearbox operating at 97% efficiency dissipates 3% of its input power as heat. At rated torque and speed, this heat is within the gearbox’s thermal capacity \u2014 the housing surface area radiates and convects it fast enough to maintain steady-state temperature. When applied torque exceeds the rated value, friction power increases in proportion, and the housing temperature rises until either a new thermal equilibrium is reached or the maximum seal\/bearing\/grease temperature is exceeded.<\/p>\n

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THERMAL POWER DISSIPATION vs OVERLOAD<\/p>\n

P_heat = P_input \u00d7 (1 \u2212 \u03b7)
\nP_input = T_output \u00d7 \u03c9_output \/ \u03b7At rated torque T\u2080, \u03c9\u2080:
\nP_heat_rated = T\u2080 \u00d7 \u03c9\u2080 \/ \u03b7 \u00d7 (1\u2212\u03b7)
\n= T\u2080 \u00d7 \u03c9\u2080 \u00d7 (1\u2212\u03b7)\/\u03b7At 1.5\u00d7 T\u2080 (50% overload):
\nP_heat_overload = 1.5 \u00d7 P_heat_rated<\/p>\n

Example: EP-AB090 P1, T\u2080=300 N\u00b7m, n=100rpm
\nP_heat_rated = 300\u00d7(100\u00d72\u03c0\/60)\/0.97 \u00d7 0.03
\n= 300\u00d710.47\/0.97 \u00d7 0.03 = 97 W<\/span><\/p>\n

At 1.5\u00d7 overload: P_heat = 145 W<\/span>
\nHousing \u0394T \u221d P_heat \/ (h \u00d7 A)
\nh=convection coeff, A=housing surface area<\/p>\n<\/div>\n<\/div>\n

The worm-to-planetary replacement trap:<\/strong> A Korean food packaging line replaces a worm reducer (\u03b7=60%) with an EP-BPG planetary (\u03b7=97%) to save energy. The facility engineer notes that the planetary is more efficient \u2014 and chooses a motor with the minimum power for the planetary’s running torque at 97% efficiency. What the engineer misses: the motor is now also more efficient, delivering more torque per ampere than before. The conveyor that previously ran at 80% of the worm reducer’s rated torque (limited by motor heat) now runs at 95% of the planetary’s rated torque \u2014 and on heavy material days, briefly exceeds it. The gearbox overheats within weeks.<\/p>\n<\/div>\n

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\"planetary<\/p>\n

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Torque overload diagnostic signatures:<\/div>\n
\u2713 Heat is uniform across housing (not localised)
\n\u2713 Problem worsens with heavier material loads
\n\u2713 Motor current exceeds rated ampere on overload events
\n\u2713 Problem began after production rate increase
\n\u2713 After worm\u2192planetary replacement without motor recheckFix:<\/strong> Verify actual peak torque with a torque meter. If exceeding rated, upsize gearbox frame or reduce load. Review service factor applied at original specification.<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n

<\/p>\n

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Root Cause 3 \u2014 Grease Degradation, Contamination and Over-Greasing<\/h2>\n
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Korea Ever-Power EP series gearboxes are factory-filled with sealed grease designed for the full gearbox service life \u2014 no periodic re-greasing is required or recommended under normal operating conditions. Overheating from grease degradation occurs through three mechanisms: natural end-of-life oxidation (at the normal usage rate, after approximately 20,000 hours), accelerated oxidation from previously overheated grease, and contamination from external sources breaching the seal.<\/p>\n

The over-greasing failure mode<\/strong> is specific to Korean industrial practice and deserves special attention. When a maintenance team adds grease to a sealed planetary gearbox \u2014 either because they believe it needs routine lubrication or because they misidentify a seal leak \u2014 the added grease increases internal pressure, forces the existing grease against the seals, and may introduce incompatible grease types. Internally pressurised grease creates churning losses that directly add to operating temperature. Korean field cases confirm that over-greased EP gearboxes can reach housing temperatures 20\u201330\u00b0C above normal within one operating shift after the incorrect greasing.<\/p>\n

Critical instruction for Korean maintenance teams: <\/strong>
\nKorea Ever-Power EP series gearboxes with sealed grease construction DO NOT require re-greasing. The fill port (if visible) is a factory fill point, not a field service port. Adding grease to a sealed EP gearbox voids the thermal design and accelerates, rather than prevents, overheating. If you observe grease weeping from the shaft seal, this indicates seal wear \u2014 the correct action is to schedule gearbox replacement, not to add more grease.<\/span><\/div>\n<\/div>\n
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Grease Degradation \u2014 Three Pathways<\/div>\n
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\u2460 Normal end-of-life (~20,000h)<\/div>\n
Grease slowly oxidises over time. Symptom: gradual temperature rise over weeks. Fix: planned gearbox replacement at service interval.<\/div>\n<\/div>\n
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\u2461 Over-greasing by maintenance team<\/div>\n
Added grease creates internal pressure and churning. Symptom: rapid temperature rise within 1 shift of maintenance activity. Fix: drain excess grease, verify housing volume.<\/div>\n<\/div>\n
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\u2462 Contamination via failed seal<\/div>\n
Water, coolant or cleaning agent enters through worn seal. Grease emulsifies, loses film strength. Symptom: intermittent temperature spikes, visible contamination in expelled grease. Fix: seal replacement (= gearbox replacement).<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n

<\/p>\n

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Root Cause 4 \u2014 Ambient Temperature Stacking and Korean Summer Conditions<\/h2>\n
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A gearbox that operates within temperature limits in March may overheat every August \u2014 not because anything has changed in the machine, but because Korean summer ambient temperatures add directly to the gearbox’s steady-state operating temperature. This “ambient stacking” effect is the most frequently overlooked root cause in Korean industrial overheating cases, and the one that produces the most frustrating pattern: the gearbox runs fine for eight months of the year and fails in summer.<\/p>\n

The steady-state gearbox housing temperature is approximately: T_housing = T_ambient + \u0394T_operating<\/strong>, where \u0394T_operating is the temperature rise from friction losses above ambient \u2014 typically 20\u201340\u00b0C for a correctly sized gearbox. If a gearbox produces \u0394T_operating = 40\u00b0C and the Korean factory ambient is 18\u00b0C in March, the housing reaches 58\u00b0C \u2014 well within the 90\u00b0C grease limit. In August, the same Korean factory with poor ventilation may reach 38\u00b0C ambient \u2014 the same gearbox now reaches 78\u00b0C. Add a partial load increase from summer production surge, and the housing exceeds 90\u00b0C.<\/p>\n

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KOREAN SEASONAL AMBIENT STACKING<\/p>\n

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T_housing = T_ambient + \u0394T_operating<\/p>\n

March (T_amb=18\u00b0C, \u0394T=40\u00b0C):
\nT_housing = 18 + 40 = 58\u00b0C \u2713 safe<\/span><\/p>\n

August (T_amb=38\u00b0C, \u0394T=40\u00b0C):
\nT_housing = 38 + 40 = 78\u00b0C \u26a0 warning<\/span><\/p>\n

Aug + partial overload (\u0394T=52\u00b0C):
\nT_housing = 38 + 52 = 90\u00b0C \u2192 grease limit<\/span><\/p>\n

Aug + unventilated enclosure (+10\u00b0C):
\nT_housing = 48 + 52 = 100\u00b0C \u2192 seal failure risk<\/span><\/p>\n<\/div>\n<\/div>\n<\/div>\n

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Prevention \u2014 Korean Summer Preparation<\/div>\n
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\u2460 Improve ventilation<\/strong>
\nInstall directional air flow over gearbox housing. Even 2 m\/s air flow can reduce \u0394T_operating by 8\u201312\u00b0C through enhanced convection.<\/span><\/div>\n
\u2461 Reduce production rate in peak summer<\/strong>
\n5\u201310% speed reduction reduces friction power by ~10\u201320%, providing margin for the higher ambient temperature.<\/span><\/div>\n
\u2462 Upsize at next gearbox replacement<\/strong>
\nIf seasonal overheating recurs annually, specify one frame size larger at replacement \u2014 more housing surface area reduces \u0394T_operating at the same load.<\/span><\/div>\n
\u2463 Verify enclosure ventilation<\/strong>
\nGearboxes in sealed enclosures can reach ambient +15\u00b0C above open-air installation. Ensure motor\/gearbox enclosures have adequate ventilation slots or forced cooling.<\/span><\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n

<\/p>\n

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Steady-State Thermal Calculation \u2014 Predicting Housing Temperature Before Installation<\/h2>\n
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The steady-state housing temperature can be estimated before installation using the thermal equilibrium model: at steady state, the heat generated by friction losses equals the heat dissipated through the housing surface by natural convection and radiation. Solving for the housing temperature above ambient gives the operating \u0394T.<\/p>\n

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STEADY-STATE THERMAL BALANCE<\/p>\n

Heat generated:
\nP_heat = P_input \u00d7 (1 \u2212 \u03b7)
\nP_input = T_out \u00d7 \u03c9_out \/ \u03b7Heat dissipated (natural convection):
\nP_diss = h \u00d7 A \u00d7 \u0394T
\nh \u2248 10\u201315 W\/(m\u00b2\u00b7K) natural convection
\nA = housing surface area (m\u00b2)At steady state: P_heat = P_diss
\n\u0394T = P_heat \/ (h \u00d7 A)<\/p>\n

Example: EP-AB090, T=300 N\u00b7m, n=100 rpm
\nP_heat \u2248 97 W (from Module 3)
\nA_housing \u2248 0.08 m\u00b2 (090mm frame est.)
\nh = 12 W\/(m\u00b2\u00b7K) (natural convection)<\/p>\n

\u0394T = 97 \/ (12 \u00d7 0.08) = 101\u00b0C above ambient<\/span>
\nT_housing = 25 + 101 = 126\u00b0C \u26a0 too hot!<\/span><\/p>\n

At rated load only (T=200 N\u00b7m):
\nP_heat = 65 W
\n\u0394T = 65\/0.96 = 68\u00b0C above ambient<\/span>
\nT_housing = 25 + 68 = 93\u00b0C \u2713 acceptable<\/span><\/p>\n<\/div>\n<\/div>\n

This calculation reveals that the gearbox at 300 N\u00b7m (its rated value) would exceed safe operating temperature without forced ventilation \u2014 meaning Korea Ever-Power’s published rated torque assumes a ventilated installation or intermittent duty cycle. Always confirm the duty cycle (continuous vs intermittent) and ventilation condition when selecting gearbox frame size for continuous high-load Korean conveyor and packaging applications.<\/p>\n<\/div>\n

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\"Korea<\/p>\n

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Duty cycle factor for Korean 3-shift vs intermittent:<\/div>\n

Korea Ever-Power EP-AB rated torque is specified for S1 (continuous) duty at 100% duty cycle. For intermittent duty (S3\/S5, less than 60% on-time), the permissible torque is increased by a duty cycle factor: T_S3 = T_S1 \u00d7 \u221a(1\/DC), where DC is the on-time fraction. At 25% duty cycle: T_allowed = T_S1 \u00d7 \u221a(1\/0.25) = 2\u00d7 T_S1. This is why indexing drives can use smaller gearboxes than continuous drives at the same peak torque.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n

<\/p>\n

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5-Minute On-Site Diagnosis Protocol \u2014 Finding the Root Cause Without Disassembly<\/h2>\n

When a Korean production engineer reports a hot gearbox, the first response is almost always to check coolant flow or add ventilation \u2014 treating the symptom. The 5-minute protocol below identifies the root cause before any corrective action is taken, saving weeks of repeat failures. All steps require only a temperature gun (infrared thermometer) and the gearbox’s nameplate or Korea Ever-Power specification sheet.<\/p>\n

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1<\/div>\n
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Measure housing temperature at three points (1 min)<\/div>\n

Use an infrared thermometer to measure: (A) centre of output shaft bearing cap, (B) centre of input shaft bearing cap, (C) gear housing body mid-section. Record all three and note which is hottest. Bearing cap hottest \u2192 Root Cause 1 (overspeed) or Root Cause 3 (grease).<\/strong> Housing body hottest \u2192 Root Cause 2 (overload).<\/p>\n<\/div>\n<\/div>\n<\/div>\n

\n
\n
2<\/div>\n
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Check input shaft speed vs rated maximum (1 min)<\/div>\n

Find the rated maximum input speed on the gearbox nameplate or Korea Ever-Power datasheet. Measure or calculate the actual input shaft speed from the motor nameplate RPM and VFD frequency: n_actual = n_nameplate \u00d7 (f_VFD \/ 50). If n_actual > n_rated_max: Root Cause 1 confirmed. Stop here.<\/strong><\/p>\n<\/div>\n<\/div>\n<\/div>\n

\n
\n
3<\/div>\n
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Check motor current vs rated (1 min)<\/div>\n

Read the motor drive display or clamp-meter the motor supply cable. Compare to motor nameplate current. If motor current consistently exceeds rated ampere during production: torque demand exceeds design \u2192 Root Cause 2 likely. Check load conditions and service factor.<\/strong><\/p>\n<\/div>\n<\/div>\n<\/div>\n

\n
\n
4<\/div>\n
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Check maintenance history and shaft seal (1 min)<\/div>\n

Ask: has anyone added grease to this gearbox in the past 3 months? Inspect the output shaft seal visually: is there grease residue on the shaft or housing exterior? Grease external = seal worn or over-pressurised \u2192 Root Cause 3 if grease was recently added; seal replacement needed.<\/strong><\/p>\n<\/div>\n<\/div>\n<\/div>\n

\n
\n
5<\/div>\n
\n
Compare temperature pattern across seasons (1 min)<\/div>\n

Review temperature logs or ask operators: does overheating occur only in summer months (June\u2013August)? Does it begin a few hours into the shift on hot days? If yes: ambient stacking \u2192 Root Cause 4. Add ventilation or reduce summer production rate before replacing the gearbox.<\/strong><\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n

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After identifying root cause \u2014 what to do next<\/div>\n
\n
RC1 (Overspeed):<\/strong> Reduce VFD frequency or replace with higher-speed rated gearbox before continuing operation.<\/div>\n
RC2 (Overload):<\/strong> Reduce load or upsize frame at next available shutdown. Do not add cooling to mask overload \u2014 gear damage is accumulating.<\/div>\n
RC3 (Grease):<\/strong> If over-greased: drain excess. If seal failed: schedule replacement. Do not re-grease sealed EP gearboxes.<\/div>\n
RC4 (Ambient):<\/strong> Add directional air flow, reduce summer rate, or upsize at next replacement. Cooling addresses root cause here.<\/div>\n<\/div>\n<\/div>\n

<\/p>\n

\n\n\n\n\n\n\n\n\n
Root Cause<\/th>\nPrimary Symptom<\/th>\nQuick Diagnosis<\/th>\nFix<\/th>\n<\/tr>\n<\/thead>\n
RC1 \u2014 Overspeed<\/td>\nHeat at bearing caps, high-pitch noise<\/td>\nn_actual > n_rated_max?<\/td>\nReduce VFD freq or replace gearbox<\/td>\n<\/tr>\n
RC2 \u2014 Overload<\/td>\nUniform body heat, worsens under load<\/td>\nMotor current > rated A?<\/td>\nUpsize frame or reduce load<\/td>\n<\/tr>\n
RC3 \u2014 Grease<\/td>\nGradual rise or after maintenance<\/td>\nGrease added recently? Seal weeping?<\/td>\nDrain excess \/ replace gearbox<\/td>\n<\/tr>\n
RC4 \u2014 Ambient<\/td>\nSummer-only, improves in cooler weather<\/td>\nProblem starts June\u2013August only?<\/td>\nAdd ventilation or reduce summer load<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/section>\n

<\/p>\n

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Overheating Prevention \u2014 The 8-Point Specification and Installation Checklist<\/h2>\n
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\u2460 Apply service factor at specification<\/div>\n

Always calculate T_rated = T_running \u00d7 SF (1.25\u20132.5). Never specify at running torque alone. SF absorbs startup peaks, seasonal load variation, and material surges that cause transient overload.<\/p>\n<\/div>\n

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\u2461 Verify input speed against rated maximum<\/div>\n

Confirm n_motor \u00d7 (f_VFD\/50) \u2264 n_max_gearbox. Always recheck when VFD frequency is changed. This step prevents the most common Korean conveyor\/packaging overheating cause.<\/p>\n<\/div>\n

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\u2462 Account for Korean summer ambient<\/div>\n

Use T_ambient = 38\u00b0C as the summer design basis for Korean indoor factories without air conditioning. Verify T_housing = 38 + \u0394T_operating \u2264 80\u00b0C (conservative), not \u2264 90\u00b0C (limit).<\/p>\n<\/div>\n

\n
\u2463 Do NOT re-grease sealed EP gearboxes<\/div>\n

Instruct maintenance teams explicitly: sealed Korea Ever-Power EP series require no re-greasing. Over-greasing is a direct cause of overheating in Korean field experience. Post a label on the gearbox if necessary.<\/p>\n<\/div>\n

\n
\u2464 Ensure airflow around housing<\/div>\n

Gearboxes must not be enclosed in cabinets without ventilation. Minimum 50 mm clearance on all faces for natural convection. Directional fan air preferred for continuous high-load applications.<\/p>\n<\/div>\n

\n
\u2465 Match duty cycle to rated torque<\/div>\n

Continuous S1 duty and intermittent S3 duty have different permissible torques for the same gearbox. Verify rated torque in the catalogue corresponds to your actual duty cycle before final frame size selection.<\/p>\n<\/div>\n

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\u2466 Annual temperature baseline measurement<\/div>\n

During annual maintenance, record housing temperature at steady state and compare to previous year. A 5\u00b0C year-on-year rise indicates beginning grease degradation \u2014 plan replacement in the next maintenance window.<\/p>\n<\/div>\n

\n
\u2467 Use KF\/KH only for indoor 0\u00b0C+ installations<\/div>\n

The EP-KF\/KH hypoid series<\/a> 0\u00b0C minimum is not a cold-start limit \u2014 it is the operating minimum. Using KF\/KH in environments where temperatures reach 0\u00b0C produces grease viscosity that generates excess heat from churning at low temperature. Paradoxically, a “cold” KF\/KH can overheat from cold-temperature churning losses.<\/p>\n<\/div>\n<\/div>\n

<\/p>\n

\n\n\n\n\n\n\n\n\n\n\n
Housing Temperature<\/th>\nAbove Rated T\u2080 (70\u00b0C)<\/th>\nLife Remaining (%)<\/th>\nEP-AB 20,000h \u2192 Hours<\/th>\nAction Required<\/th>\n<\/tr>\n<\/thead>\n
\u226470\u00b0C<\/td>\nRated<\/td>\n100%<\/td>\n20,000 h<\/td>\nNormal \u2014 no action<\/td>\n<\/tr>\n
80\u00b0C<\/td>\n+10\u00b0C<\/td>\n50%<\/td>\n10,000 h<\/td>\nInvestigate root cause<\/td>\n<\/tr>\n
90\u00b0C<\/td>\n+20\u00b0C<\/td>\n25%<\/td>\n5,000 h<\/td>\nFix root cause immediately<\/td>\n<\/tr>\n
100\u00b0C<\/td>\n+30\u00b0C<\/td>\n12.5%<\/td>\n2,500 h<\/td>\nReduce load\/speed urgently<\/td>\n<\/tr>\n
110\u00b0C<\/td>\n+40\u00b0C<\/td>\n6.25%<\/td>\n1,250 h<\/td>\nStop \u2014 schedule replacement<\/td>\n<\/tr>\n
120\u00b0C<\/td>\n+50\u00b0C<\/td>\n3.1%<\/td>\n625 h<\/td>\nStop immediately<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/section>\n

\"Planetary<\/p>\n

\n

Frequently Asked Questions \u2014 Planetary Gearbox Overheating<\/h2>\n
\n
\n

Q<\/span>
\nMy EP-AB gearbox ran fine for 2 years and then started overheating with no machine changes. What is the most likely cause?<\/h3>\n

A gearbox that ran correctly for two years and then begins overheating without machine changes is exhibiting natural end-of-life grease degradation. At three-shift Korean operation (~6,300 hours\/year), two years of operation equals approximately 12,600 hours \u2014 past the halfway point of the 20,000-hour design life. The grease is beginning to lose its viscosity-temperature characteristics from normal oxidation aging. This manifests as a gradual, steady temperature rise over weeks or months rather than a sudden step change. The correct action is to schedule gearbox replacement in the next planned maintenance window \u2014 typically at the next annual shutdown. Do not attempt to add or replace grease in the sealed unit; the housing must be replaced. For simple conveyor and agitator drives where continuous torque is modest, the Economic Line<\/a> sealed-grease construction provides the same zero-maintenance principle at lower cost.<\/p>\n<\/div>\n

\n

Q<\/span>
\nIs it safe to continue running the gearbox at elevated temperature while waiting for the replacement unit to arrive?<\/h3>\n

This depends on the temperature and root cause. If housing temperature is 80\u201390\u00b0C (10\u201320\u00b0C above the 70\u00b0C typical operating point), short-term continued operation is possible with active monitoring \u2014 increase monitoring to every two hours and watch for any rapid temperature increase (more than 5\u00b0C per hour), unusual noise, or visible grease leakage. If housing temperature exceeds 90\u00b0C, Arrhenius life reduction is accelerating rapidly and continued operation should be minimised \u2014 reduce load or speed if possible to lower temperature. If temperature exceeds 100\u00b0C, stop the gearbox immediately; bearing and seal damage may already be irreversible, and continued operation risks a complete in-service failure that is more disruptive and dangerous than a planned shutdown.<\/p>\n<\/div>\n

\n

Q<\/span>
\nCan I install a cooling fan on the gearbox housing to solve overheating?<\/h3>\n

Adding forced cooling can address Root Cause 4 (ambient temperature stacking) and provide temporary relief for mild Root Cause 2 (modest overload). A 2 m\/s airflow over the gearbox housing can reduce steady-state \u0394T by 30\u201350%, providing meaningful temperature margin. However, forced cooling cannot address Root Cause 1 (overspeed) or Root Cause 3 (grease degradation\/contamination) \u2014 in those cases, the problem source remains active regardless of cooling added externally. Forced cooling applied to an overloaded gearbox (Root Cause 2) reduces the symptom while gear tooth fatigue accumulates unseen inside the housing. The correct sequence is always: (1) diagnose root cause, (2) fix root cause, (3) add cooling as supplementary margin if ambient conditions justify it.<\/p>\n<\/div>\n

\n

Q<\/span>
\nFor a multi-axis Korean gantry machine, should I connect CV shafts to gearbox outputs that run hot?<\/h3>\n

If a gearbox in a multi-axis gantry system runs at elevated temperature, it is particularly important to diagnose and correct the root cause before adding coupling components. An overheating gearbox bearing produces shaft runout as the bearing clearances change with thermal expansion \u2014 a hot gearbox output shaft may oscillate in position by 0.01\u20130.05 mm with thermal cycling. When a CV drive shaft<\/a> connects two axes that need synchronisation, thermal position drift in one gearbox introduces gantry synchronisation error that compounds with actual trajectory errors. Maintain normal gearbox operating temperature before integrating precision shaft couplings in synchronised multi-axis gantry configurations.<\/p>\n<\/div>\n<\/div>\n<\/section>\n

<\/p>\n

\n

Overheating? Korea Ever-Power Can Identify the Root Cause<\/h2>\n

Korea Ever-Power’s Korean application team provides remote thermal diagnosis from your machine parameters \u2014 input speed, load torque, ambient temperature, and duty cycle \u2014 and confirms whether the current gearbox specification is adequate or whether an upsized replacement is required. Same working day response.<\/p>\n

EP-AB Precision Series \u2192
\n<\/a>
\nEP-AF High-Rigidity Series \u2192
\n<\/a><\/div>\n<\/section>\n

\u7de8\u96c6\u8005: Cxm<\/p>\n<\/div>","protected":false},"excerpt":{"rendered":"

Root Cause Analysis \u00b7 Thermal Calculation \u00b7 5-Min Diagnosis Protocol Planetary Gearbox Overheating \u2014 Root Causes, Diagnosis and Prevention Every 10\u00b0C rise above rated operating temperature halves the remaining service life of a precision planetary gearbox \u2014 this is not an approximation but a direct consequence of the Arrhenius equation governing lubricant degradation and gear surface fatigue. Korean engineers who identify overheating early and correct its root cause prevent failures worth months of unplanned downtime; those who address the symptom (adding cooling) without finding the cause watch the gearbox fail again within weeks. View EP-AB Precision Series \u2192 How Overheating Destroys a Precision Planetary Gearbox \u2014 The Arrhenius Mechanism A […]<\/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-675","post","type-post","status-publish","format-standard","hentry","category-application-and-technical-guid"],"_links":{"self":[{"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/posts\/675","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/comments?post=675"}],"version-history":[{"count":3,"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/posts\/675\/revisions"}],"predecessor-version":[{"id":678,"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/posts\/675\/revisions\/678"}],"wp:attachment":[{"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/media?parent=675"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/categories?post=675"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/ja\/wp-json\/wp\/v2\/tags?post=675"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}