{"id":672,"date":"2026-05-29T05:41:03","date_gmt":"2026-05-29T05:41:03","guid":{"rendered":"https:\/\/planetary-gearboxes.com\/?p=672"},"modified":"2026-05-29T05:41:49","modified_gmt":"2026-05-29T05:41:49","slug":"planetary-gearbox-vs-harmonic-drive-vs-cycloidal","status":"publish","type":"post","link":"https:\/\/planetary-gearboxes.com\/hi\/planetary-gearbox-vs-harmonic-drive-vs-cycloidal\/","title":{"rendered":"\u092a\u094d\u0932\u0947\u0928\u0947\u091f\u0930\u0940 \u0917\u093f\u092f\u0930\u092c\u0949\u0915\u094d\u0938 \u092c\u0928\u093e\u092e \u0939\u093e\u0930\u094d\u092e\u094b\u0928\u093f\u0915 \u0921\u094d\u0930\u093e\u0907\u0935 \u092c\u0928\u093e\u092e \u0938\u093e\u0907\u0915\u094d\u0932\u094b\u0907\u0921\u0932 \u0930\u093f\u0921\u094d\u092f\u0942\u0938\u0930"},"content":{"rendered":"
\n

<\/p>\n

\"planetary<\/p>\n
\n
Technical Comparison \u00b7 5-Dimension Analysis \u00b7 Korean Price Bands \u00b7 Application Fit<\/div>\n

Planetary Gearbox vs Harmonic Drive
\nvs Cycloidal \u2014 Which to Specify When<\/h1>\n

The planetary gearbox vs harmonic drive vs cycloidal debate occupies Korean machine builders choosing between these three technologies encounter the same gap in published documentation: backlash numbers and torque ratings are easy to find, but the five dimensions that actually determine which technology wins for a specific application \u2014 shock load tolerance, efficiency under duty cycles, fatigue life, unit cost at Korean volume, and maintenance reality<\/strong> \u2014 are rarely quantified in the same document.<\/p>\n

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

<\/p>\n

\n

Three Fundamentally Different Reduction Mechanisms<\/h2>\n
\n
\n
PLANETARY<\/div>\n

Rolling-contact involute gears<\/h3>\n

Sun gear drives multiple planet gears meshing simultaneously with a fixed ring gear. Load is distributed across N planet contacts (N=3\u20135), producing high torque density in a compact cylindrical envelope. Gear teeth roll and slide in contact \u2014 contact stress is Hertzian, proportional to applied load.<\/p>\n

Ratio range: i = 3\u201310,000
\nBacklash: \u22641\u20138 arcmin (P0\u2013AE)
\nEfficiency: \u226594\u201398% per stage
\nShock tolerance: HIGH (metal teeth)
\nMaintenance: Sealed grease, none<\/div>\n<\/div>\n
\n
HARMONIC DRIVE (STRAIN WAVE)<\/div>\n

Elastic flexspline deformation<\/h3>\n

An elliptical wave generator cam elastically deforms a thin-wall flexible gear (flexspline) to mesh with a rigid circular spline at two diametrically opposite points. The tooth count difference between flexspline and circular spline produces the speed reduction. Backlash is near-zero by mechanism \u2014 no clearance required for deformation-driven mesh.<\/p>\n

Ratio range: i = 30\u2013320 per stage
\nBacklash: \u22640.5 arcmin (typical)
\nEfficiency: 75\u201385% (flexspline loss)
\nShock tolerance: LOW (flex fatigue)
\nMaintenance: Grease, periodic check<\/div>\n<\/div>\n
\n
CYCLOIDAL (RV REDUCER)<\/div>\n

Eccentric cam + pin-gear mesh<\/h3>\n

An eccentric input crankshaft drives a cycloidal disc that rolls around the inside of a fixed ring of cylindrical pins. The eccentric motion of the disc minus one pin-pitch per revolution produces the speed reduction. Large contact area (half the pins engaged simultaneously) gives very high torque density and excellent shock tolerance. Output is taken through output pins in the disc.<\/p>\n

Ratio range: i = 6\u201387 per stage
\nBacklash: \u22641 arcmin (typical)
\nEfficiency: 85\u201393% per stage
\nShock tolerance: VERY HIGH
\nMaintenance: Oil bath, periodic change<\/div>\n<\/div>\n<\/div>\n

In the planetary gearbox vs harmonic drive vs cycloidal comparison, the three mechanisms are not competing versions of the same design \u2014 they are genuinely different engineering approaches with non-overlapping strength profiles. The selection question is not “which is better” but “which profile matches the actual application requirements in each of the five key dimensions.”<\/p>\n<\/section>\n

<\/p>\n

\n

Five-Dimension Quantified Comparison \u2014 The Data That Catalogue Specs Don’t Show<\/h2>\n
\n\n\n\n\n\n\n\n\n\n\n
Dimension<\/th>\n\u0917\u094d\u0930\u0939\u094b\u0902<\/th>\nHarmonic Drive<\/th>\nCycloidal (RV)<\/th>\n<\/tr>\n<\/thead>\n
Backlash \u2014 single stage<\/td>\n\u22641\u20135 arcmin (P0\u2013P2)
\nSelectable grade<\/span><\/td>\n		\u22640.5 arcmin
\nBest in class<\/span><\/td>\n		\u22641 \u0906\u0930\u094d\u0915\u092e\u093f\u0928
\nGood, consistent<\/span><\/td>\n<\/tr>\n
Torque density (N\u00b7m\/kg)<\/td>\n30\u201380 N\u00b7m\/kg
\nGood \u2014 multi-planet sharing<\/span><\/td>\n		60\u2013150 N\u00b7m\/kg
\nBest in class, very compact<\/span><\/td>\n		80\u2013200 N\u00b7m\/kg
\nHighest (large contact area)<\/span><\/td>\n<\/tr>\n
Shock load tolerance<\/td>\nHigh
\nMetal teeth, peak T = 2\u20133\u00d7 rated<\/span><\/td>\n		Low
\nFlexspline fatigue crack risk<\/span><\/td>\n		Very high
\nPeak T = 5\u00d7 rated (typical)<\/span><\/td>\n<\/tr>\n
Efficiency \u2014 continuous rated load<\/td>\n94\u201398%
\nBest for high-power drives<\/span><\/td>\n		75\u201385%
\nFlexspline hysteresis loss<\/span><\/td>\n		85\u201393%
\nPin friction losses<\/span><\/td>\n<\/tr>\n
Korean unit cost (same T output)<\/td>\n1.0\u00d7 (baseline)
\nBest value for most apps<\/span><\/td>\n		3\u20138\u00d7
\nFlexspline precision machining<\/span><\/td>\n		2\u20134\u00d7
\nComplex eccentric + pin assembly<\/span><\/td>\n<\/tr>\n
Maintenance requirement<\/td>\nNone (sealed grease)
\nFactory fill lasts service life<\/span><\/td>\n		Grease check (periodic)
\nFlexspline inspection at intervals<\/span><\/td>\n		Oil bath change (periodic)
\nAnnual oil level\/quality check<\/span><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n
Reading this table: <\/strong>
\nNo single technology wins on all dimensions in a planetary gearbox vs harmonic drive comparison. Harmonic drive wins on backlash and torque density; cycloidal wins on shock tolerance and peak torque multiple; planetary wins on efficiency, cost, and zero-maintenance sealed construction. The application determines which dimensions matter most \u2014 and in the majority of Korean servo applications, efficiency and cost are dominant, which is why planetary gearboxes serve approximately 80% of the Korean servo drive market despite not leading on backlash or torque density.<\/span><\/div>\n<\/section>\n

<\/p>\n

\n

When Harmonic Drive Outperforms Planetary \u2014 The Genuine Use Cases<\/h2>\n
\n
\n

The harmonic drive earns its cost premium in applications where backlash \u22640.5 arcmin is a genuine functional requirement \u2014 not simply a specification selected conservatively. Three Korean application categories justify harmonic drive selection despite the 3\u20138\u00d7 cost premium over equivalent planetary units.<\/p>\n

\n
\u2460 Collaborative robot wrist joints (J4\u2013J6)<\/strong><\/p>\n

The wrist joints of a 6-axis collaborative robot must position the tool centre point (TCP) to \u00b10.05 mm. At the typical 400\u2013600 mm TCP reach of Korean cobot arms, backlash \u22640.5 arcmin (0.008\u00b0) produces a TCP error of 0.06 mm \u2014 just within tolerance. P0 planetary (\u22641 arcmin) produces 0.12 mm TCP error at 600 mm reach \u2014 exceeding the \u00b10.05 mm target. For Korean cobot OEMs competing on positioning accuracy, the harmonic drive’s \u22640.5 arcmin is the specification that makes their product work; planetary P0 is genuinely insufficient for this application.<\/p>\n<\/div>\n

\u2461 Semiconductor wafer handler rotation axes<\/strong><\/p>\n

Korean FOUP and wafer cassette transfer handlers position wafers to \u00b10.1 mm on a 300 mm radius rotation axis \u2014 requiring backlash below 0.6 arcmin. The cleanroom environment also favours harmonic drives: their sealed compact construction generates fewer particles than the larger-diameter planetary gear sets at equivalent torque-to-weight ratios. Samsung and SK Hynix equipment vendors specify harmonic drives for wafer handler rotation axes as a category rule.<\/p>\n<\/div>\n

\u2462 Precision optical instrument pointing axes<\/strong><\/p>\n

Korean astronomical telescope drives, satellite tracking antennas, and multi-axis laser cutting machine tilt axes require sub-arcminute repeatability that planetary gearboxes at P0 (\u22641 arcmin) cannot consistently deliver across temperature cycles. The harmonic drive’s near-zero backlash is not just a specification advantage here \u2014 it simplifies the servo control model by eliminating the reversal dead zone from the control loop entirely.<\/p>\n<\/div>\n<\/div>\n

The harmonic drive shock-load warning: <\/strong>
\nThe flexspline \u2014 the thin-wall elastic gear that makes near-zero backlash possible \u2014 is also the harmonic drive’s most critical failure point. Shock loads beyond the rated peak torque (typically 1.5\u20132\u00d7 rated for harmonic drives vs 2\u20133\u00d7 for planetary) cause fatigue cracks in the flexspline that propagate rapidly. Korean robot applications where the arm may impact workpieces or fixtures during programming errors have repeatedly produced flexspline failures that require complete harmonic drive replacement. The EP-AB P0<\/a> planetary at \u22641 arcmin withstands the same shock events with metal gear tooth contact \u2014 the damage is tooth surface fatigue that accumulates slowly, not a single catastrophic crack.<\/span><\/div>\n<\/div>\n
\"planetary
\n<\/p>\n
\n

TCP ERROR AT 600mm REACH<\/p>\n

Harmonic \u22640.5′: 600\u00d70.000145 = 0.087mm \u2713
\nEP-AFH \u22641.0′: 600\u00d70.000291 = 0.175mm \u2713
\nEP-AB P0 \u22641.0′: same as AFH = 0.175mm \u2713
\nEP-AB P1 \u22643.0′: 600\u00d70.000873 = 0.524mm \u2717<\/p>\n

Cobot \u00b10.05mm spec at 600mm:<\/span>
\nRequires backlash \u22640.48 arcmin
\n\u2192 Harmonic drive required
\n\u2192 EP-AFH marginal<\/p>\n

At 300mm reach:<\/span>
\nRequires backlash \u22640.96 arcmin
\n\u2192 EP-AFH \u22641′ adequate \u2713
\n\u2192 EP-AB P0 marginal \u2713<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n

<\/p>\n

\n

When Cycloidal (RV Reducer) Outperforms Planetary \u2014 High Shock, High Torque<\/h2>\n
\n
\n

The cycloidal reducer’s distinguishing characteristic is its exceptional shock load tolerance \u2014 peak torque ratings of 4\u20136\u00d7 the rated continuous torque are typical, compared to 2\u20133\u00d7 for planetary and 1.5\u20132\u00d7 for harmonic drives. This tolerance comes from the large contact area of the cycloidal mechanism: approximately half the output pins engage simultaneously, distributing any shock load across multiple contacts rather than concentrating it on the two mesh points active in a planetary gear.<\/p>\n

In Korean industry, cycloidal reducers dominate three application categories where shock tolerance and stiffness are the overriding requirements:<\/p>\n

\n
\u2460 Heavy industrial robot base joints (J1\u2013J3)<\/strong><\/p>\n

Korean automotive welding robots (700\u20131,500 kg payload capacity, 2\u20134 m reach) use RV cycloidal reducers on the base, shoulder, and elbow joints \u2014 where the combined inertia of the robot arm and payload produces peak joint torques of 3,000\u20138,000 N\u00b7m during emergency stops. The cycloidal’s 4\u20136\u00d7 peak torque multiple absorbs these events; a planetary at the same rated torque would require frame sizes 2\u20133\u00d7 larger to provide equivalent peak tolerance.<\/p>\n<\/div>\n

\u2461 Press and stamping machine drive shafts<\/strong><\/p>\n

Korean automotive steel press lines produce peak drive shaft torques during blank contact that can reach 8\u201310\u00d7 the mean torque. The cycloidal reducer’s pin-gear mechanism distributes this shock across its contact area without the tooth fracture risk that limits planetary gearboxes in direct press applications.<\/p>\n<\/div>\n

\u2462 Marine and offshore winch drives<\/strong><\/p>\n

Korean shipbuilding applies RV reducers to offshore crane slewing rings and anchor winch drives where wave-induced shock loads are continuous and unpredictable in magnitude. The zero-maintenance oil bath (compared to sealed grease in planetary) is a disadvantage, but the shock tolerance advantage outweighs it in this application.<\/p>\n<\/div>\n<\/div>\n<\/div>\n

\n
\n
Peak Torque Multiple Comparison<\/div>\n
\n
\n
Cycloidal (RV)<\/span>
\n4\u20136\u00d7 rated<\/span><\/div>\n
\n
5\u00d7<\/span><\/div>\n<\/div>\n<\/div>\n
\n
Planetary (EP-AB)<\/span>
\n2\u20133\u00d7 rated<\/span><\/div>\n
\n
2.5\u00d7<\/span><\/div>\n<\/div>\n<\/div>\n
\n
Harmonic Drive<\/span>
\n1.5\u20132\u00d7 rated<\/span><\/div>\n
\n
1.8\u00d7<\/span><\/div>\n<\/div>\n<\/div>\n<\/div>\n

Peak torque multiples are typical values. Confirm specific unit ratings from manufacturer specifications for each application.<\/p>\n<\/div>\n

\n
Cycloidal maintenance note for Korean industry:<\/div>\n

Cycloidal reducers use an oil bath lubricant that requires periodic oil level checks and annual oil quality assessment. In Korean food processing environments, this creates a KFDA hygiene concern \u2014 an oil-bath reducer near food contact surfaces requires additional containment measures. For food and cleanroom applications, sealed planetary gearboxes remain the hygienically preferred choice even where cycloidal torque density would be advantageous.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n

<\/p>\n

\n

When Planetary Gearbox Wins \u2014 Why It Serves 80% of Korean Servo Applications<\/h2>\n
\n
\n

Whether specified as EP-BPG energy-saving<\/a> for conveyor replacement or EP-AB precision for servo axes, the planetary gearbox does not win on any single specification dimension against its specialised competitors. It wins on the combination of adequate performance across all dimensions simultaneously, combined with price, availability, and zero-maintenance sealed construction that no competing technology matches. In practice, approximately 80% of Korean servo drive applications require neither the sub-0.5 arcmin backlash of harmonic drives nor the 5\u00d7 shock tolerance of cycloidal reducers \u2014 and for those 80%, the planetary is objectively the correct choice.<\/p>\n

Efficiency advantage quantified:<\/strong> A Korean packaging line running 200 VFFS machines 21 hours per day, each with a cross-seal jaw servo at 750W nominal input power. At harmonic drive efficiency 80%, the system draws 937W per servo. At planetary efficiency 97%, the same servo draws 773W. Per machine: 164W difference \u00d7 21h \u00d7 330 days = 1,137 kWh\/year. At Korean industrial electricity rates (\u20a9150\/kWh): \u20a9170,550 saved per machine per year<\/strong>. Over 200 machines: \u20a934.1 million saved annually. Over a 10-year machine life: \u20a9341 million \u2014 for choosing planetary over harmonic on axes where backlash \u22640.5 arcmin is not actually required.<\/p>\n

Zero-maintenance advantage:<\/strong> In Korean three-shift food packaging and logistics operations, maintenance windows are measured in minutes per machine per month. A harmonic drive requiring periodic grease inspection and a cycloidal reducer requiring oil level checks and annual oil changes both consume maintenance labour that a sealed planetary gearbox does not. The zero-maintenance sealed construction of Korea Ever-Power EP series is not a minor convenience feature \u2014 for facilities running 300+ machines, it is a significant operational cost advantage.<\/p>\n<\/div>\n

\"BAF<\/p>\n
\n

EFFICIENCY COST \u2014 200 VFFS MACHINES, 10 YEARS<\/p>\n

Harmonic (\u03b7=80%): 937W \u00d7 21h \u00d7 330d
\n= 6,493 kWh\/machine\/yr
\nPlanetary (\u03b7=97%): 773W \u00d7 same
\n= 5,356 kWh\/machine\/yr
\nSaving: 1,137 kWh \u00d7 \u20a9150 = \u20a9170,550\/yr<\/p>\n

200 machines \u00d7 10 years:
\n\u20a9341,100,000 saved<\/span>
\nby choosing planetary over harmonic
\non axes where \u22640.5′ is not required<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n

<\/p>\n

\n

Korean Market Price Comparison \u2014 Relative Cost at Equivalent Torque Output<\/h2>\n

Absolute pricing varies by supplier, volume, and specification. The following relative cost analysis uses Korea Ever-Power EP-AB as the 1.0\u00d7 baseline and reflects typical Korean industrial market pricing for equivalent continuous output torque at i=50:1 single-stage, P0\/\u22641 arcmin backlash.<\/p>\n

\n\n\n\n\n\n\n\n
Technology<\/th>\nRelative Unit Cost<\/th>\n10-yr Energy Cost<\/th>\nMaintenance Cost<\/th>\nWhen Worth the Premium<\/th>\n<\/tr>\n<\/thead>\n
Planetary (EP-AB P0)<\/td>\n1.0\u00d7 baseline<\/td>\nLowest (\u03b7\u226597%)<\/td>\nZero (sealed)<\/td>\n80% of Korean servo applications<\/td>\n<\/tr>\n
Cycloidal (RV)<\/td>\n2\u20134\u00d7<\/td>\nModerate (\u03b785\u201393%)<\/td>\nOil changes (annual)<\/td>\nHeavy industrial robot J1\u2013J3; press drives<\/td>\n<\/tr>\n
Harmonic Drive<\/td>\n3\u20138\u00d7<\/td>\nHighest (\u03b775\u201385%)<\/td>\nGrease check<\/td>\nCobot J4\u2013J6; wafer handler; optical pointing<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n
The Korean OEM over-specification pattern: <\/strong>
\nA consistent pattern in Korean machine design is specifying harmonic drives on all robot joints because J4\u2013J6 require them \u2014 then specifying the same harmonic drives on J1\u2013J3 for component commonality. This costs 3\u20135\u00d7 more than necessary on the base joints, delivers efficiency losses on the highest-torque axes (where harmonic efficiency loss is largest in absolute watt terms), and achieves no accuracy benefit since J1\u2013J3 positioning error is dominated by structural compliance at the robot reach, not gearbox backlash. Correctly mixed specifications \u2014 harmonic drive on J4\u2013J6, planetary on J1\u2013J3 \u2014 deliver the same robot TCP accuracy at significantly lower system cost and higher overall efficiency.<\/span><\/div>\n<\/section>\n

<\/p>\n

\n

Application Decision Guide \u2014 Which Technology for Which Korean Application<\/h2>\n
\n\n\n\n\n\n\n\n\n\n\n\n\n
Korean Application<\/th>\nBacklash Req.<\/th>\nShock Need<\/th>\nRecommended<\/th>\nKorea Ever-Power<\/th>\n<\/tr>\n<\/thead>\n
Cobot J1\u2013J3 (shoulder, elbow)<\/td>\n\u22643 \u0906\u0930\u094d\u0915\u092e\u093f\u0928<\/td>\nMedium<\/td>\n\u0917\u094d\u0930\u0939\u094b\u0902<\/td>\n\u0908\u092a\u0940-\u090f\u092c\u0940 \u092a\u09401<\/a><\/td>\n<\/tr>\n
Cobot J4\u2013J6 (wrist)<\/td>\n\u22640.5 arcmin<\/td>\nLow\u2013Medium<\/td>\nHarmonic<\/td>\nNot planetary<\/td>\n<\/tr>\n
CNC 5-axis rotary table<\/td>\n\u22641 \u0906\u0930\u094d\u0915\u092e\u093f\u0928<\/td>\nLow<\/td>\n\u0917\u094d\u0930\u0939\u094b\u0902<\/td>\n\u0908\u092a\u0940-\u090f\u090f\u092b\u090f\u091a<\/a><\/td>\n<\/tr>\n
Korean automotive press drive<\/td>\n\u22643 \u0906\u0930\u094d\u0915\u092e\u093f\u0928<\/td>\nVery high<\/td>\n\u091a\u0915\u094d\u0930\u091c\u093e\u0924<\/td>\nNot planetary<\/td>\n<\/tr>\n
VFFS packaging jaw \/ conveyor<\/td>\n\u22643\u20135 arcmin<\/td>\nLow\u2013Medium<\/td>\n\u0917\u094d\u0930\u0939\u094b\u0902<\/td>\nEP-AB P1\/P2<\/a><\/td>\n<\/tr>\n
Semiconductor wafer handler<\/td>\n\u22640.5 arcmin<\/td>\nLow<\/td>\nHarmonic<\/td>\nNot planetary<\/td>\n<\/tr>\n
Solar tracker \/ wind turbine yaw<\/td>\n\u22643\u20138 arcmin<\/td>\nMedium<\/td>\n\u0917\u094d\u0930\u0939\u094b\u0902<\/td>\nEP-AH New Line<\/a><\/td>\n<\/tr>\n
AGV \/ AMR drive wheel<\/td>\nP1\u2013P2 (ratio match)<\/td>\nMedium<\/td>\n\u0917\u094d\u0930\u0939\u094b\u0902<\/td>\nEP-KF<\/a> or EP-AB<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n<\/section>\n

\"\u092a\u094d\u0932\u0947\u0928\u0947\u091f\u0930\u0940-\u0917\u093f\u092f\u0930\u092c\u0949\u0915\u094d\u0938-\u090f\u092a\u094d\u0932\u093f\u0915\u0947\u0936\u0928-1\"<\/p>\n

\n

Efficiency Under Real Duty Cycles \u2014 The Number Harmonic Drive Catalogues Don’t Highlight<\/h2>\n
\n
\n

Harmonic drive catalogues typically specify peak efficiency at rated load and rated speed \u2014 conditions where the flexspline hysteresis losses are proportionally small relative to the transmitted power. However, Korean servo applications frequently operate at partial load (30\u201370% of rated torque) and variable speeds \u2014 conditions where harmonic drive efficiency drops significantly below its peak specification.<\/p>\n

The efficiency-load characteristic of the three technologies diverges most sharply at partial load. Planetary gearbox efficiency is relatively flat across the load range \u2014 at 30% of rated torque, efficiency remains 94\u201396%. Harmonic drive efficiency at 30% of rated torque drops to 65\u201375% (the flexspline hysteresis loss is nearly constant in absolute watts regardless of load). Cycloidal efficiency at partial load is moderate \u2014 80\u201388%.<\/p>\n

This partial-load efficiency gap is particularly significant for Korean packaging and assembly machine servo drives that spend substantial time at partial load during acceleration ramps, dwell phases, and light-load product handling. A Korean cobot arm in pick-and-place operation may operate at full rated torque for only 10\u201320% of its cycle time \u2014 spending the remaining 80\u201390% at partial load. Under this duty cycle, the harmonic drive’s real-world average efficiency is closer to 70\u201375%, not the catalogue-stated 80\u201385%.<\/p>\n<\/div>\n

\n
\n

Efficiency at Partial Load (% of Rated Torque)<\/p>\n

Load % Planetary Harmonic Cycloidal
\n100% 97% 82% 92%
\n70% 96% 78% 89%
\n50% 95% 73% 86%
\n30% 94% 68% 82%
\n10% 92% 58% 75%Partial-load efficiency matters:
\nMost Korean servo axes run 20\u201370%
\nof rated torque for >70% of cycle time.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n

<\/p>\n

\n

Frequently Asked Questions \u2014 Planetary vs Harmonic Drive vs Cycloidal<\/h2>\n
\n
\n

\u0915\u094d\u092f\u0942<\/span>
\nOur Korean robot integrator recommends harmonic drives on all six joints. Is this necessary?<\/h3>\n

For joints J4\u2013J6 (wrist) where the specification requires \u22640.5 arcmin backlash and the tool centre point accuracy target is \u00b10.05 mm at reach, harmonic drives are technically justified. For joints J1\u2013J3 (base, shoulder, elbow), the TCP accuracy is dominated by structural compliance and joint stiffness at those large radii, not by gearbox backlash \u2014 P0 or P1 planetary gearboxes (\u22641\u20133 arcmin) achieve the same robot TCP accuracy at J1\u2013J3 at significantly lower cost and higher efficiency. A correctly specified 6-axis Korean cobot uses harmonic drives at J4\u2013J6 and planetary gearboxes at J1\u2013J3. If your integrator is specifying harmonic drives at all six joints, ask them to show the calculation connecting J1\u2013J3 gearbox backlash to TCP accuracy \u2014 in most cases, the calculation will show that planetary P0 at J1\u2013J3 achieves the same result.<\/p>\n<\/div>\n

\n

\u0915\u094d\u092f\u0942<\/span>
\nCan a Korea Ever-Power EP-AFH planetary gearbox replace a harmonic drive on a Korean cobot joint?<\/h3>\n

The \u0908\u092a\u0940-\u090f\u090f\u092b\u090f\u091a \u0905\u0932\u094d\u091f\u094d\u0930\u093e-\u092a\u094d\u0930\u0947\u0938\u093f\u091c\u0928 \u0936\u094d\u0930\u0943\u0902\u0916\u0932\u093e<\/a> delivers \u22641 arcmin backlash as standard \u2014 approaching the harmonic drive’s \u22640.5 arcmin but not matching it. For J1\u2013J3 joints on a cobot with 400\u2013600 mm reach, EP-AFH is the correct replacement \u2014 TCP accuracy at those radii is not degraded by the 0.5 arcmin difference. For J4\u2013J6 wrist joints where sub-0.5 arcmin is a genuine functional requirement, EP-AFH at \u22641 arcmin is marginally outside the specification. Korea Ever-Power recommends confirming the specific accuracy requirement at the joint \u2014 if the requirement is \u22641 arcmin at the joint (not at the TCP), EP-AFH is a direct cost-efficient replacement. If \u22640.5 arcmin at the joint is specified, the harmonic drive remains the correct choice.<\/p>\n<\/div>\n

\n

\u0915\u094d\u092f\u0942<\/span>
\nWhy do Korean CNC machine tool builders use planetary gearboxes rather than harmonic drives for rotary tables?<\/h3>\n

Korean 5-axis machining centre rotary tables require \u22641 arcmin positioning accuracy and 2,000\u20135,000 N\u00b7m holding torque against machining forces. Harmonic drives at these torque levels become very expensive (3\u20138\u00d7 the cost of equivalent planetary) and their peak torque multiple of 1.5\u20132\u00d7 rated is insufficient for the interrupted cutting shock loads from milling titanium and high-hardness steels \u2014 peak cutting forces can exceed 2.5\u00d7 the rated holding torque during toolpath reversals. The planetary gearbox (P0 \u22641 arcmin, peak torque 2\u20133\u00d7 rated) meets the accuracy requirement and survives the shock loads at a cost that makes it the universal choice for Korean CNC rotary table drives.<\/p>\n<\/div>\n

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\u0915\u094d\u092f\u0942<\/span>
\nFor Korean machine builders considering worm reducers as a cost alternative, how does the comparison extend?<\/h3>\n

Worm gear reducers<\/a> occupy a different cost tier \u2014 typically 0.3\u20130.6\u00d7 the cost of an equivalent planetary \u2014 but this cost advantage comes with meaningful capability trade-offs: efficiency of 40\u201370% (vs planetary \u226597%), backlash of 10\u201330 arcmin (vs planetary \u22641\u20135 arcmin), and torque output that degrades significantly above 40\u00b0C ambient as the worm lubricant viscosity drops. Worm reducers are appropriate for slow conveyor drives and agitator applications where efficiency and backlash are secondary to cost and self-locking capability. For any application requiring closed-loop servo position control, the worm’s 10\u201330 arcmin backlash effectively prohibits its use on precision axes \u2014 the planetary gearbox is the minimum precision standard for servo positioning.<\/p>\n<\/div>\n<\/div>\n<\/section>\n

<\/p>\n

\n

Confirm the Right Technology with Korea Ever-Power Application Support<\/h2>\n

Korea Ever-Power’s application team evaluates your accuracy requirement, shock load profile, and efficiency budget to confirm whether planetary gearbox is the correct technology \u2014 or whether a different approach is warranted. Honest assessment, same working day, in Korean.<\/p>\n

EP-AB P0\/P1 Precision Series \u2192
\n<\/a><\/div>\n<\/section>\n

\u0938\u0902\u092a\u093e\u0926\u0915: \u0938\u0940\u090f\u0915\u094d\u0938\u090f\u092e<\/p>\n<\/div>","protected":false},"excerpt":{"rendered":"

Technical Comparison \u00b7 5-Dimension Analysis \u00b7 Korean Price Bands \u00b7 Application Fit Planetary Gearbox vs Harmonic Drive vs Cycloidal \u2014 Which to Specify When The planetary gearbox vs harmonic drive vs cycloidal debate occupies Korean machine builders choosing between these three technologies encounter the same gap in published documentation: backlash numbers and torque ratings are […]<\/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-672","post","type-post","status-publish","format-standard","hentry","category-application-and-technical-guid"],"_links":{"self":[{"href":"https:\/\/planetary-gearboxes.com\/hi\/wp-json\/wp\/v2\/posts\/672","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/planetary-gearboxes.com\/hi\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/planetary-gearboxes.com\/hi\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/hi\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/hi\/wp-json\/wp\/v2\/comments?post=672"}],"version-history":[{"count":2,"href":"https:\/\/planetary-gearboxes.com\/hi\/wp-json\/wp\/v2\/posts\/672\/revisions"}],"predecessor-version":[{"id":674,"href":"https:\/\/planetary-gearboxes.com\/hi\/wp-json\/wp\/v2\/posts\/672\/revisions\/674"}],"wp:attachment":[{"href":"https:\/\/planetary-gearboxes.com\/hi\/wp-json\/wp\/v2\/media?parent=672"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/hi\/wp-json\/wp\/v2\/categories?post=672"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/hi\/wp-json\/wp\/v2\/tags?post=672"}],"curies":[{"name":"\u0921\u092c\u094d\u0932\u094d\u092f\u0942\u092a\u0940","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}