{"id":1875,"date":"2026-07-20T05:40:05","date_gmt":"2026-07-20T05:40:05","guid":{"rendered":"https:\/\/gearrack.top\/?p=1875"},"modified":"2026-07-20T05:40:05","modified_gmt":"2026-07-20T05:40:05","slug":"planetary-gearboxes-for-robotics","status":"publish","type":"post","link":"https:\/\/gearrack.top\/ko\/planetary-gearboxes-for-robotics\/","title":{"rendered":"Planetary Gearboxes for Robotics"},"content":{"rendered":"
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GEAR APPLICATION GUIDE \u00b7 PLANETARY GEAR \u00b7 P02<\/span><\/p>\n

Planetary Gearboxes for Robotics:
\nJoint Drive Selection and Gear Specification<\/span><\/h1>\n

Industrial robot joint drives demand the highest combination of torque density, backlash accuracy, torsional stiffness, and service life of any gear application \u2014 operating billions of cycles over 10\u201315-year robot lifetimes at continuous rated torque. This guide covers planetary gearbox selection for 6-axis robot arm joints, collaborative robot joints, SCARA robot drives, and delta robot arm drives \u2014 including torque, speed, and accuracy specifications for each joint type and axis position.<\/p>\n

20CrMnTi \u00b7 17-4 PH \u00b7 DIN 4\u20136 \u00b7 B10 \u2265 10,000 h<\/span>
\nBacklash <1 arcmin \u00b7 Ratio 5:1\u2013100:1<\/span>
\n6-Axis \u00b7 SCARA \u00b7 Collaborative \u00b7 Delta<\/span><\/div>\n<\/div>\n<\/div>\n
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DESIGN LIFE<\/p>\n

B10 \u2265 10,000 h<\/p>\n

Industrial robot joint planetary gearbox minimum L10 life at rated torque. Automotive body welding robots: 30,000\u201350,000 hours. Collaborative robots in lighter duty: 20,000 hours<\/p>\n<\/div>\n

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BACKLASH TARGET<\/p>\n

<1 arcmin<\/p>\n

Ultra-precision class backlash for robot joint planetary gearboxes. Determines the robot’s positional repeatability \u2014 typically \u00b10.02\u20130.1 mm at the tool centre point (TCP) for industrial robots<\/p>\n<\/div>\n

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CYCLE COUNT<\/p>\n

> 109<\/sup> cycles<\/p>\n

Robot joint gear cycles over lifetime. At 3,000 cycles\/hour and 6,000 hours\/year over 5-year TBO: 90 million cycles per joint. High-speed wrist joints at 10,000+ cycles\/hour: several billion tooth mesh cycles over robot life<\/p>\n<\/div>\n

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EFFICIENCY<\/p>\n

94\u201397%<\/p>\n

Robot joint planetary gearbox efficiency \u2014 critical for collaborative robots operating near human workers where heat generation is a safety constraint, and for battery-powered AMRs where efficiency directly affects run time<\/p>\n<\/div>\n<\/div>\n

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Robot Joint Drive Requirements \u2014 Why Planetary Gearboxes Are Standard<\/h2>\n

The industrial robot joint drive is the most demanding gear application in terms of the combination of required properties: the gearbox must simultaneously achieve ultra-low backlash (<1 arcmin), high torsional stiffness (>5 Nm\/arcmin), maximum torque density (the heaviest possible joint torque in the smallest possible volume), and multi-billion-cycle fatigue life \u2014 all in a compact in-line (coaxial input\/output) arrangement that mounts directly behind the servo motor. No gear type other than the planetary gearbox achieves this combination, which is why planetary gearboxes are used in virtually every industrial robot joint worldwide.<\/p>\n

Korea Ever-Power’s planetary gearboxes for robotics<\/a> are manufactured in 20CrMnTi case carburized for standard robot joint applications and 17-4 PH stainless for food processing and cleanroom robot joints \u2014 ground to DIN 4\u20135 quality class, assembled with needle roller planet bearings for maximum stiffness, and measured to backlash <1 arcmin before shipment. The carrier and ring gear are machined to H7 tolerances for precise housing fit, and the sun gear is available in a hollow shaft configuration for direct servo motor shaft insertion without a separate coupling. See also: planetary gearboxes<\/a> for robotics specifications and selection data.<\/p>\n

The backlash of a robot joint planetary gearbox defines the robot’s positioning dead band when the joint reverses direction. At a 500 mm robot arm length and a 1 arcmin joint gearbox backlash: TCP dead band = 500 \u00d7 tan(1\/60 \u00d7 \u03c0\/180) = 0.145 mm. For a 6-axis robot with six joints, each contributing up to 1 arcmin backlash, the cumulative TCP positioning uncertainty can reach 0.5\u20131.0 mm \u2014 unacceptable for precision assembly or laser cutting applications. This is why ultra-precision (<1 arcmin, and ideally <0.3 arcmin) planetary gearboxes are specified for robot joints despite their higher cost compared to standard precision (<3 arcmin) servo planetary gearboxes.<\/p>\n

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Torque Density \u2014 Compact Joint Design<\/h3>\n

Robot joints are severely constrained in diameter by the robot arm structure \u2014 a 20 kg payload 6-axis robot typically has a J1 (waist) joint diameter of 120\u2013160 mm and J6 (wrist flange) of 50\u201380 mm. The planetary gearbox, by dividing the load among 3 planet gears simultaneously, achieves 3\u20135\u00d7 the torque density of an equivalent spur gear reducer in the same housing diameter. This allows the rated joint torque to be achieved within the robot arm diameter constraints that would be impossible with any parallel-shaft gear arrangement.<\/p>\n<\/div>\n

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Fatigue Life \u2014 Billion-Cycle Endurance<\/h3>\n

An automotive spot-welding robot operating at 3,000 weld cycles per hour for 6,000 hours per year accumulates 108 million joint cycles per year. Over a 5-year TBO (time between overhaul), joint 6 (the wrist flip joint, which moves on every cycle) accumulates over 500 million load cycles. The gear fatigue design for robot joint planetary gears must use the tooth root bending endurance limit (\u03c3FlimN<\/sub> at >3 \u00d7 109<\/sup> cycles) rather than the finite life fatigue curve \u2014 the gears must operate at stresses permanently below the endurance limit to avoid fatigue failure within the design life.<\/p>\n<\/div>\n

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Torsional Stiffness \u2014 Servo Response<\/h3>\n

Robot joint torsional stiffness (Nm\/arcmin) determines how quickly the servo controller can accelerate the joint after a direction reversal before the output shaft begins to track the motor \u2014 lower stiffness means slower servo response and reduced contouring accuracy during high-speed continuous path motion. Korea Ever-Power robot joint planetary gears are manufactured to the tightest tooth profile tolerances achievable at DIN 4 quality to maximise mesh stiffness per planet contact, and needle roller planet bearings (vs ball bearings) provide the highest planet radial stiffness and therefore the highest gearbox torsional stiffness per unit mass.<\/p>\n<\/div>\n<\/div>\n<\/section>\n

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Robot Type and Joint Specifications<\/h2>\n
\"planetary
Korea Ever-Power precision planetary gear kit for industrial robot joint application \u2014 20CrMnTi case carburized sun gear, planet gears, and ring gear, ground to DIN 4 quality class. Needle roller planet bearings (4-piece inner race design for maximum stiffness). Backlash <1 arcmin, torsional stiffness 12 Nm\/arcmin, gear ratio 10:1, input speed 5,000 RPM maximum. Planet carrier output flange drilled to customer robot interface pattern. Lifetime lubricant filled (Kluber Isoflex NBU 15) sealed for no-maintenance service life. Supplied with backlash and stiffness test certificate per joint.<\/figcaption><\/figure>\n
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ROBOT \/ JOINT<\/th>\nRATIO<\/th>\nBACKLASH<\/th>\nRATED TORQUE<\/th>\nTYPICAL APPLICATION<\/th>\n<\/tr>\n<\/thead>\n
6-axis robot J1 (waist)<\/td>\n50:1\u2013100:1<\/td>\n<1 arcmin<\/td>\n500\u20133,000 Nm<\/td>\nHeavy arm swing, full robot payload & reach moment arm<\/td>\n<\/tr>\n
6-axis robot J2\/J3 (upper arm)<\/td>\n40:1\u201380:1<\/td>\n<1 arcmin<\/td>\n300\u20131,500 Nm<\/td>\nArm elevation and extension against gravity plus payload inertia<\/td>\n<\/tr>\n
6-axis robot J4\/J5 (forearm)<\/td>\n20:1\u201350:1<\/td>\n<1 arcmin<\/td>\n80\u2013400 Nm<\/td>\nWrist bend and twist \u2014 highest cycle rate, lightest torque<\/td>\n<\/tr>\n
6-axis robot J6 (wrist flange)<\/td>\n10:1\u201325:1<\/td>\n<0.5 arcmin<\/td>\n20\u2013120 Nm<\/td>\nTool orientation \u2014 fastest motion, most cycles, tightest backlash requirement<\/td>\n<\/tr>\n
SCARA robot (R-theta axes)<\/td>\n10:1\u201330:1<\/td>\n<3 arcmin<\/td>\n20\u2013200 Nm<\/td>\nAssembly, dispensing, pick-and-place \u2014 horizontal arm axes only<\/td>\n<\/tr>\n
Collaborative robot (all joints)<\/td>\n50:1\u2013100:1<\/td>\n<3 arcmin<\/td>\n30\u2013300 Nm<\/td>\nHuman-collaborative assembly \u2014 6-axis, lower speed, force-torque sensing integrated in each joint<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n
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KEY DIFFERENCES: INDUSTRIAL ROBOT vs COLLABORATIVE ROBOT PLANETARY GEARS<\/p>\n

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Industrial Robot (High Power)<\/p>\n

Higher torque-to-weight ratio priority. Maximum cycle speed. 20CrMnTi case carburized standard. 3-planet for compactness. Sealed grease lifetime lubrication standard. Tool centre point repeatability \u00b10.02\u20130.05 mm. Annual operating hours 6,000\u20138,000.<\/p>\n<\/div>\n

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Collaborative Robot (Cobot)<\/p>\n

Back-drivability required for force sensing (cobot joints must allow the human to push the arm to a stop in collision). Lower efficiency acceptable. Force-torque sensor embedded in each joint. More planets (4\u20135) for load sharing at lower speed. TCP repeatability \u00b10.05\u20130.10 mm. Annual hours 2,000\u20134,000.<\/p>\n<\/div>\n

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Washdown \/ Food Robot<\/p>\n

17-4 PH stainless planetary gears or 20CrMnTi with stainless housing. NSF H1 food-grade lubricant. IP67 or IP69K rated joint housing. FDA\/EU food contact compliance. Less stringent backlash (<3 arcmin acceptable) \u2014 food robots operate at lower speeds than automotive robots.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n

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Frequently Asked Questions<\/h2>\n
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Q 01<\/span><\/p>\n

How do I select the correct planetary gearbox ratio for each joint of a 6-axis robot?<\/p>\n<\/div>\n

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Robot joint ratio selection is driven by three simultaneously applied constraints: (1) Rated joint torque:<\/strong> Tjoint<\/sub> = Tmotor<\/sub> \u00d7 i \u00d7 \u03b7. The joint must produce the maximum rated torque including the gravitational torque of all downstream arm segments and payload at the worst-case arm configuration. (2) Maximum joint speed:<\/strong> \u03c9joint<\/sub> = \u03c9motor,max<\/sub> \u00f7 i. The joint must achieve the specified maximum angular velocity at the rapid traverse speed (J1\/J2\/J3 typically 180\u2013300\u00b0\/s, J4\/J5\/J6 wrist typically 400\u2013600\u00b0\/s). (3) Reflected inertia:<\/strong> Jreflected<\/sub> = Jarm segment + payload<\/sub> \u00f7 i\u00b2 must be within the servo amplifier’s inertia ratio specification relative to Jmotor<\/sub>. For J1 (waist), the reflected inertia of the full robot arm at worst-case extension is the dominant constraint \u2014 typically requires high ratio (50:1\u2013100:1) to bring the reflected inertia within the motor’s servo bandwidth limit. For J6 (wrist), the payload inertia is small but the speed requirement is high \u2014 lower ratio (10:1\u201320:1) with a high-speed motor is typical. Korea Ever-Power can model the joint torque, speed, and inertia for your specific robot payload and arm geometry if you provide the arm segment masses, lengths, and servo motor specifications.<\/p>\n<\/div>\n<\/div>\n

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Q 02<\/span><\/p>\n

What is the expected service life of a robot joint planetary gearbox, and what causes premature failure?<\/p>\n<\/div>\n

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A correctly specified and maintained industrial robot joint planetary gearbox should achieve a B10 life of 10,000\u201320,000 hours under rated load. Automotive spot-welding robots (the highest-duty robot application) typically reach 30,000\u201340,000 hours before joint gearbox replacement is scheduled. Premature failure causes, in order of frequency: (1) Overloading above rated peak torque<\/strong> \u2014 robot program modifications that increase reach, payload, or acceleration beyond the original design specification accelerate tooth fatigue and planet bearing wear. (2) Lubricant degradation<\/strong> \u2014 sealed lifetime-lubricated robot joints use pre-filled synthetic grease that should not require replacement, but contamination (coolant entry through damaged seals) or thermal degradation from continuous high-cycle operation above 80\u00b0C reduces lubrication effectiveness, accelerating wear. (3) Impact overload<\/strong> \u2014 robot collision events that exceed the gearbox’s maximum allowable overload torque (typically 2.5\u20133.5\u00d7 rated) can cause immediate tooth fracture or planet bearing overload; robots should be fitted with electronic torque limiting in the servo amplifier and structural fuse elements (shear pins) to protect the joint gearboxes from collision overload. Korea Ever-Power supplies robot joint gearbox replacement kits with the failed component analysis report identifying the failure mode when the failed unit is returned.<\/p>\n<\/div>\n<\/div>\n

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Q 03<\/span><\/p>\n

Can Korea Ever-Power supply robot joint planetary gear sets as replacement for Harmonic Drive, Nabtesco, or other brand robot joint gearboxes?<\/p>\n<\/div>\n

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Korea Ever-Power supplies planetary gear replacement kits for standard robot joint gearboxes using involute planetary gear technology (standard multi-planet gearboxes used in many robot designs from Chinese, Korean, and European manufacturers). It is important to note that Harmonic Drive and Nabtesco Cycloidal gearboxes (commonly used in Japanese robot brands such as Fanuc, Yaskawa, and Kawasaki) use non-involute gear principles \u2014 wave generator and flexspline (Harmonic Drive) or cycloidal disc and roller pins (Nabtesco) \u2014 which are fundamentally different from involute planetary gears and cannot be supplied as equivalents by Korea Ever-Power. For robots using standard involute planetary gearboxes (common in Chinese robot brands, many European collaborative robots, and custom robot designs), Korea Ever-Power can supply replacement sun gear, planet gear sets, and ring gears to the specified ratio, module, and quality class. Contact Korea Ever-Power with the robot brand, model, joint number, and gearbox ratio for an immediate assessment of whether the joint uses involute planetary or non-involute technology, and a quotation for the applicable replacement parts.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n

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Explore Korea Ever-Power Gear Categories<\/h2>\n

Seven precision gear product lines for robotics, CNC, automotive, industrial and specialist applications worldwide.<\/p>\n<\/div>\n

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\"spur<\/p>\n
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Spur Gears<\/a><\/p>\n

M1\u2013M20 \u00b7 C45, 20CrMnTi, 316L<\/p>\n<\/div>\n<\/div>\n

\"helical<\/p>\n
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Helical Gears<\/a><\/p>\n

Low noise \u00b7 high contact ratio \u00b7 gearbox<\/p>\n<\/div>\n<\/div>\n

\"bevel<\/p>\n
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\ubca0\ubca8 \uae30\uc5b4<\/a><\/p>\n

Right-angle drives \u00b7 straight & spiral<\/p>\n<\/div>\n<\/div>\n

\"worm<\/p>\n
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Worm Gears<\/a><\/p>\n

High ratio \u00b7 self-locking \u00b7 valve, hoist<\/p>\n<\/div>\n<\/div>\n

\"ring<\/p>\n
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Ring Gears<\/a><\/p>\n

Internal \u00b7 planetary stage \u00b7 robot joint<\/p>\n<\/div>\n<\/div>\n

\"planetary<\/p>\n
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Planetary Gears<\/a><\/p>\n

Low backlash \u00b7 robot joint \u00b7 servo, CNC<\/p>\n<\/div>\n<\/div>\n

\"plastic<\/p>\n
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Plastic Gears<\/a><\/p>\n

POM \u00b7 PA66 \u00b7 PEEK \u00b7 cleanroom robot<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n

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GET A QUOTATION \u00b7 KOREA EVER-POWER<\/p>\n

Need Planetary Gearboxes for Robotics?<\/h2>\n

Korea Ever-Power manufactures 20CrMnTi and 17-4 PH stainless planetary gear sets for all robot joint drive applications \u2014 DIN 4\u20135 quality class, backlash <1 arcmin, ratio 5:1\u2013100:1, torque 20\u20133,000 Nm. 6-axis industrial robots, SCARA, collaborative robots, washdown robots. Backlash and stiffness test certificate with every order. Planetary gearboxes selection guide at planetary-gearboxes.com.<\/p>\n

Request a Quotation \u2192<\/a><\/p>\n<\/div>\n<\/div>\n

\ud3b8\uc9d1\uc790: Cxm<\/em><\/p>\n<\/div>","protected":false},"excerpt":{"rendered":"

GEAR APPLICATION GUIDE \u00b7 PLANETARY GEAR \u00b7 P02 Planetary Gearboxes for Robotics: Joint Drive Selection and Gear Specification Industrial robot joint drives demand the highest combination of torque density, backlash accuracy, torsional stiffness, and service life of any gear application \u2014 operating billions of cycles over 10\u201315-year robot lifetimes at continuous rated torque. This guide […]<\/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":[4566],"tags":[],"class_list":["post-1875","post","type-post","status-publish","format-standard","hentry","category-application-of-gears"],"_links":{"self":[{"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/posts\/1875","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/comments?post=1875"}],"version-history":[{"count":1,"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/posts\/1875\/revisions"}],"predecessor-version":[{"id":1876,"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/posts\/1875\/revisions\/1876"}],"wp:attachment":[{"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/media?parent=1875"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/categories?post=1875"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/gearrack.top\/ko\/wp-json\/wp\/v2\/tags?post=1875"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}