{"id":747,"date":"2026-06-03T01:47:04","date_gmt":"2026-06-03T01:47:04","guid":{"rendered":"https:\/\/planetary-gearboxes.com\/?p=747"},"modified":"2026-06-03T01:47:04","modified_gmt":"2026-06-03T01:47:04","slug":"planetary-gearbox-torsional-stiffness-dynamic-accuracy-ct-backlash","status":"publish","type":"post","link":"https:\/\/planetary-gearboxes.com\/zh\/planetary-gearbox-torsional-stiffness-dynamic-accuracy-ct-backlash\/","title":{"rendered":"Planetary Gearbox Torsional Stiffness Explained \u2014 Why Ct Matters More Than Backlash at High Torque"},"content":{"rendered":"
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\u97e9\u56fd\u6c38\u529b<\/span>
\nTechnical Deep-Dive \u00b7 Dynamics<\/span><\/div>\n

Planetary Gearbox Torsional Stiffness Explained \u2014 Why Ct Matters More Than Backlash at High Torque<\/h1>\n

Every precision \u884c\u661f\u9f7f\u8f6e\u7bb1<\/a> datasheet lists backlash in arcminutes. Fewer than 20% list torsional stiffness. Yet under significant applied torque \u2014 the real operating condition of a CNC rotary table, a heavy robot joint, or a servo press \u2014 elastic angular deflection from torsional compliance exceeds the backlash specification entirely. This guide puts the number on it.<\/p>\n

Get Stiffness Analysis for Your Application \u2192<\/a><\/p>\n<\/div>\n<\/div>\n<\/section>\n

<\/p>\n

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The Parameter That Dominates Accuracy Under Load \u2014 and Rarely Appears in Selection Guides<\/h2>\n

Backlash is the accuracy specification that every gearbox selector knows. It is the angular dead band at direction reversal \u2014 measurable with no load applied, listed prominently on every datasheet, and typically the first (and sometimes only) precision criterion applied when comparing planetary gearboxes. Torsional stiffness, designated Ct and measured in N\u00b7m\/arcmin, is the parameter that determines how much the output shaft rotates elastically under an applied load. It appears in fewer than one in five published planetary gearbox selection guides \u2014 and it is entirely absent from most application-specific sizing tools.<\/p>\n

This creates a systematic blind spot: engineers specify backlash carefully, select a low-backlash unit, and then discover that at their actual operating torque, the elastic deflection from torsional compliance produces an angular error two to four times larger than the backlash they specified. The two phenomena are completely independent in origin \u2014 and a gearbox with tight backlash can have poor torsional stiffness, and vice versa.<\/p>\n

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Backlash \u2014 Direction-Reversal Error<\/div>\n

The angular dead band between input and output when drive direction reverses. Purely geometric \u2014 caused by clearance between gear teeth. Present at zero load<\/strong>. Fixed once manufactured (until wear increases it). Specified in arcmin.<\/p>\n

Measured at: \u00b13% rated torque
\nOccurs when: direction reverses
\nDepends on: manufacturing tolerance<\/div>\n<\/div>\n
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Torsional Deflection \u2014 Load-Dependent Error<\/div>\n

The elastic “wind-up” of gear teeth, shafts, and planet carrier under applied torque. Proportional to load. Occurs at any torque level<\/strong>. Disappears when load is removed (elastic). Grows with every N\u00b7m of applied torque beyond zero.<\/p>\n

Formula: \u03b8_elastic = T \/ Ct (arcmin)
\nOccurs at: any applied torque
\nDepends on: gearbox stiffness Ct<\/div>\n<\/div>\n
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Total Angular Error \u2014 What the Tool Actually Sees<\/div>\n

In real servo applications, total positioning error includes both contributions simultaneously. At low torques, backlash dominates. At high torques \u2014 above a crossover point that depends on Ct \u2014 elastic deflection exceeds backlash and becomes the primary accuracy limit<\/strong>.<\/p>\n

\u03b8_total \u2248 \u03b8_backlash + \u03b8_elastic
\n= BL + T\/Ct (arcmin)
\nLinear: E = R \u00d7 tan(\u03b8_total\/60 \u00d7 \u03c0\/180)<\/div>\n<\/div>\n<\/div>\n<\/section>\n

<\/p>\n

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The Complete EP Series Torsional Stiffness Table \u2014 All Frame Sizes and Series<\/h2>\n

The following specifications are the certified torsional stiffness values for all Korea Ever-Power EP series precision planetary gearboxes. Torsional stiffness Ct is defined as the output torque required to produce one arcminute of elastic angular deflection at the output shaft under load, with the input shaft fixed. Higher Ct means less elastic deflection under the same applied torque \u2014 and therefore better dynamic positioning accuracy.<\/p>\n

\n\n\n\n\n\n\n\n\n\n\n\n\n\n
\u7cfb\u5217<\/th>\nFrame (mm)<\/th>\nCt \u2014 1-Stage
\n(N\u00b7m\/arcmin)<\/span><\/th>\n		Ct \u2014 2-Stage
\n(N\u00b7m\/arcmin)<\/span><\/th>\n		Max Torque
\n(N\u00b7m)<\/span><\/th>\n		Ct Class<\/th>\n<\/tr>\n<\/thead>\n
EP-ZDE \/ EP-ZDF<\/a><\/td>\n40 mm<\/td>\n0.7<\/td>\n\u2014<\/td>\n6<\/td>\nLight-duty<\/td>\n<\/tr>\n
EP-ZDE \/ EP-ZDF<\/td>\n60 mm<\/td>\n1.8<\/td>\n\u2014<\/td>\n16<\/td>\nStandard<\/td>\n<\/tr>\n
EP-ZDE \/ EP-ZDF<\/td>\n80 mm<\/td>\n4.5<\/td>\n\u2014<\/td>\n50<\/td>\nStandard<\/td>\n<\/tr>\n
EP-ZDE \/ EP-ZDF<\/td>\n120 mm<\/td>\n12<\/td>\n\u2014<\/td>\n110<\/td>\nModerate<\/td>\n<\/tr>\n
EP-ZDE \/ EP-ZDF<\/td>\n160 mm<\/td>\n38<\/td>\n\u2014<\/td>\n450<\/td>\nStandard-High \u2605<\/td>\n<\/tr>\n
EP-ZDWE \/ ZDWF<\/a><\/td>\n60\u2013160 mm<\/td>\n1.5 \u2013 38<\/td>\n2.5 \u2013 43<\/td>\n16 \u2013 450<\/td>\nSame as ZDE by frame<\/td>\n<\/tr>\n
EP-ZDS<\/a><\/td>\n115 mm<\/td>\n20<\/td>\n22<\/td>\n210<\/td>\nHigh<\/td>\n<\/tr>\n
EP-ZDS<\/td>\n142 mm<\/td>\n44<\/td>\n46<\/td>\n910<\/td>\nHigh (1.16\u00d7 ZDE-160)<\/td>\n<\/tr>\n
EP-ZDS<\/td>\n190 mm<\/td>\n130<\/td>\n140<\/td>\n1,800<\/td>\nHighest (3.4\u00d7 ZDE-160) \u2605\u2605<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

\u2605 EP-ZDS-115 Ct (20 N\u00b7m\/arcmin) is lower than EP-ZDE-160 (38 N\u00b7m\/arcmin) because ZDS-115 is a smaller frame \u2014 compare within frame class, not across. \u2605\u2605 EP-ZDS-190 achieves 130 N\u00b7m\/arcmin through a larger output shaft (\u03a655h7 vs \u03a640h7), stiffer planet carrier, and preloaded output bearings. 2-stage Ct exceeds 1-stage because additional planet stages increase carrier rigidity in ZDS design.<\/p>\n<\/section>\n

<\/p>\n

\"High-torque<\/p>\n
The EP-ZDS series achieves torsional stiffness up to 130 N\u00b7m\/arcmin (1-stage) through a larger output shaft diameter, stiffer planet carrier geometry, and preloaded output bearings \u2014 delivering 3.4\u00d7 better dynamic accuracy than EP-ZDE-160 under the same applied torque. Compare planetary gearbox specifications \u2192<\/a><\/div>\n<\/div>\n

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The Crossover Point \u2014 Where Torsional Deflection Overtakes Backlash as the Dominant Error<\/h2>\n

At low torque levels, backlash dominates total angular error because the elastic deflection is small. As applied torque increases, elastic deflection grows linearly with T\/Ct while backlash remains constant. There is a crossover torque beyond which elastic deflection becomes the larger of the two error sources \u2014 and this crossover point differs dramatically between the EP-ZDE and EP-ZDS series.<\/p>\n

This is the calculation that most selection guides omit entirely \u2014 and it fundamentally changes how torsional stiffness should be weighted in the specification process for high-torque applications.<\/p>\n

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Crossover Torque: When \u03b8_elastic = \u03b8_backlash<\/div>\n
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Crossover condition: T_crossover = BL \u00d7 Ct<\/div>\n
EP-ZDE-160 (BL=8 arcmin, Ct=38): T_cross = 8 \u00d7 38 = 304 N\u00b7m<\/strong><\/div>\n
EP-ZDS-190 (BL=8 arcmin, Ct=130): T_cross = 8 \u00d7 130 = 1,040 N\u00b7m<\/strong><\/div>\n
Above T_crossover: torsional deflection is the LARGER error source \u2014 not backlash.<\/div>\n<\/div>\n

EP-ZDE-160 crosses over at 304 N\u00b7m \u2014 well within its rated range of 450 N\u00b7m. For the upper half of its torque range (304\u2013450 N\u00b7m), elastic deflection is already larger than backlash. Tightening the backlash specification from 8 arcmin to 3 arcmin in this torque range saves only 5 arcmin of dead band while the elastic deflection at 380 N\u00b7m is 10 arcmin \u2014 an error that a tighter backlash cannot address at all. EP-ZDS-190 does not cross over until 1,040 N\u00b7m \u2014 beyond its rated 1-stage range \u2014 so backlash remains the dominant error for its entire operating range, which is why the EP-ZDS achieves better total accuracy than EP-ZDE even with the same (<8 arcmin) backlash specification.<\/p>\n<\/div>\n

\n\n\n\n\n\n\n\n\n\n\n
Applied Torque<\/th>\nZDE-160
\n\u53cd\u51b2\uff08\u5f27\u5206\uff09<\/th>\n		ZDE-160
\nElastic \u03b8 (arcmin)<\/th>\n		ZDE-160
\nTotal (arcmin)<\/th>\n		ZDS-190
\nElastic \u03b8 (arcmin)<\/th>\n		ZDS-190
\nTotal (arcmin)<\/th>\n		Accuracy Gain<\/th>\n<\/tr>\n<\/thead>\n
50 N\u00b7m<\/td>\n8.0<\/td>\n1.3<\/td>\n9.3<\/td>\n0.4<\/td>\n8.4<\/td>\n1.1\u00d7 better<\/td>\n<\/tr>\n
100 N\u00b7m<\/td>\n8.0<\/td>\n2.6<\/td>\n10.6<\/td>\n0.8<\/td>\n8.8<\/td>\n1.2\u00d7 better<\/td>\n<\/tr>\n
200 N\u00b7m<\/td>\n8.0<\/td>\n5.3<\/td>\n13.3<\/td>\n1.5<\/td>\n9.5<\/td>\n1.4\u00d7 better<\/td>\n<\/tr>\n
304 N\u00b7m \u2190 Crossover<\/td>\n8.0<\/td>\n8.0 \u2190 elastic = BL<\/td>\n16.0<\/td>\n2.3<\/td>\n10.3<\/td>\n1.6\u00d7 better<\/td>\n<\/tr>\n
380 N\u00b7m<\/td>\n8.0<\/td>\n10.0 > BL<\/td>\n18.0<\/td>\n2.9<\/td>\n10.9<\/td>\n1.7\u00d7 better<\/td>\n<\/tr>\n
800 N\u00b7m<\/td>\n8.0<\/td>\n21.1<\/td>\n29.1<\/td>\n6.2<\/td>\n14.2<\/td>\n2.0\u00d7 better<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

Both units specified at <8 arcmin backlash. Ct: ZDE-160 = 38 N\u00b7m\/arcmin; ZDS-190 = 130 N\u00b7m\/arcmin. \u03b8_elastic = T\/Ct. Total = backlash + elastic. The ZDS-190 improvement grows with torque because Ct is the only differentiator \u2014 backlash is identical for both.<\/p>\n<\/section>\n

<\/p>\n

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From Arcminutes to Millimetres \u2014 Dynamic Positioning Error at Your Load Radius<\/h2>\n

As established in the backlash guide, the conversion from angular error to linear error at a specific load radius is: E_linear = R \u00d7 tan(\u03b8\/60 \u00d7 \u03c0\/180). The following table applies this conversion to the elastic deflection component alone \u2014 showing the millimetre-level dynamic positioning error from torsional compliance at four representative load radii. This is the error that tighter backlash specification cannot address.<\/p>\n

\n\n\n\n\n\n\n\n\n\n
\u626d\u77e9<\/th>\nZDE-160 elastic error (Ct=38)<\/th>\nZDS-190 elastic error (Ct=130)<\/th>\nZDS improvement<\/th>\n<\/tr>\n
Applied torque<\/th>\nR=100mm<\/th>\nR=300mm<\/th>\nR=100mm<\/th>\nR=300mm<\/th>\nat R=300mm<\/th>\n<\/tr>\n<\/thead>\n
100 N\u00b7m<\/td>\n0.077 mm<\/td>\n0.230 mm<\/td>\n0.022 mm<\/td>\n0.067 mm<\/td>\n3.4\u00d7 better<\/td>\n<\/tr>\n
200 N\u00b7m<\/td>\n0.153 mm<\/td>\n0.459 mm<\/td>\n0.045 mm<\/td>\n0.134 mm<\/td>\n3.4\u00d7 better<\/td>\n<\/tr>\n
380 N\u00b7m (heavy cut)<\/td>\n0.291\u6beb\u7c73<\/td>\n0.873 mm<\/td>\n0.085 mm<\/td>\n0.254 mm<\/td>\n3.4\u00d7 better<\/td>\n<\/tr>\n
800 N\u00b7m<\/td>\n0.613 mm<\/td>\n1.839 mm<\/td>\n0.179 mm<\/td>\n0.538 mm<\/td>\n3.4\u00d7 better<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n
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Critical insight for CNC rotary table specification:<\/strong> A CNC B-axis rotary table with a 300mm workpiece mounting radius and a peak cutting torque of 380 N\u00b7m will accumulate 0.873mm of elastic positioning error<\/strong> from torsional compliance alone if fitted with EP-ZDE-160. This error changes with every variation in cutting force \u2014 it is dynamic, not static, and servo feedback cannot compensate for it because the motor encoder measures the motor position, not the tool position. The same table fitted with EP-ZDS-190 has only 0.254mm<\/strong> of elastic error under identical cutting conditions \u2014 a 3.4\u00d7 improvement that directly translates to tighter part tolerances.<\/p>\n<\/div>\n<\/section>\n

<\/p>\n

\"Planetary<\/p>\n
Under applied torque, elastic deformation occurs at three locations in a planetary gearbox: planet gear tooth flanks (Hertzian contact deflection), sun gear mesh, and the planet carrier structure. Torsional stiffness Ct is the aggregate measure of all three deflections combined \u2014 higher Ct means less total elastic wind-up under the same torque.<\/div>\n<\/div>\n

<\/p>\n

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Torsional Stiffness and Resonant Frequency \u2014 The Servo Tuning Implication<\/h2>\n

The torsional stiffness of a precision planetary gearbox directly sets the mechanical resonant frequency of the gearbox-load system. This resonant frequency determines the upper limit of the servo velocity loop bandwidth \u2014 the speed at which the controller can respond to position errors without exciting structural resonance. A gearbox with higher Ct pushes the resonant frequency higher, allowing more aggressive servo tuning and therefore better dynamic positioning performance.<\/p>\n

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Resonant Frequency Formula<\/div>\n
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f_resonant = (1\/2\u03c0) \u00d7 \u221a(Ct_output[N\u00b7m\/rad] \/ J_load[kg\u00b7m\u00b2])<\/div>\n
Ct[N\u00b7m\/rad] = Ct[N\u00b7m\/arcmin] \u00d7 (60 \u00d7 180 \/ \u03c0) = Ct[N\u00b7m\/arcmin] \u00d7 3,438<\/div>\n
Target: f_resonant > 3\u00d7 servo control bandwidth (typically 50\u2013150 Hz for servo axes)<\/div>\n<\/div>\n<\/div>\n
\n\n\n\n\n\n\n\n\n
\u53d8\u901f\u7bb1<\/th>\nCt (N\u00b7m\/arcmin)<\/th>\nf_resonant
\nCNC table J=5 kg\u00b7m\u00b2<\/span><\/th>\n		f_resonant
\nRobot J2 J=97 kg\u00b7m\u00b2<\/span><\/th>\n		Servo Kv limit<\/th>\nTuning assessment<\/th>\n<\/tr>\n<\/thead>\n
ZDE-160<\/td>\n38<\/td>\n25.7 Hz<\/td>\n5.8 Hz<\/td>\nLimited<\/td>\nCNC table: OK. Robot J2: below servo BW \u2014 risk of oscillation<\/td>\n<\/tr>\n
ZDS-115<\/td>\n20<\/td>\n18.7 Hz<\/td>\n4.2 Hz<\/td>\nLow<\/td>\nLower Ct than ZDE-160 \u2014 correct only for smaller-frame applications, not direct upgrade<\/td>\n<\/tr>\n
ZDS-142<\/td>\n44<\/td>\n27.7 Hz<\/td>\n6.3 Hz<\/td>\nGood<\/td>\nModest improvement over ZDE-160 \u2014 preferred for heavy-load CNC and robot J2\/J3<\/td>\n<\/tr>\n
ZDS-190<\/td>\n130<\/td>\n47.6 Hz<\/td>\n10.8 Hz<\/td>\nHighest<\/td>\nBest dynamic response \u2014 recommended for large CNC tables and robot J1\/J2<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n
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\u26a0 Important: ZDS-115 has lower Ct than ZDE-160<\/div>\n

The EP-ZDS-115 (Ct=20 N\u00b7m\/arcmin) has lower torsional stiffness than the EP-ZDE-160 (Ct=38 N\u00b7m\/arcmin) because it is a smaller frame. Do not assume “ZDS = stiffer than ZDE” \u2014 the comparison is valid only within the same or comparable frame size. ZDS-142 (44) marginally exceeds ZDE-160 (38). ZDS-190 (130) vastly exceeds it. For the ZDS series to deliver its stiffness advantage, the application must require the 115\u2013190mm frame range that ZDS covers.<\/p>\n<\/div>\n

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\u2705 Why ZDS 2-stage has slightly higher Ct than 1-stage<\/div>\n

Counterintuitively, the EP-ZDS 2-stage Ct exceeds the 1-stage (ZDS-190: 140 vs 130 N\u00b7m\/arcmin). This is because the additional planet stage in ZDS contributes structural rigidity to the planet carrier assembly \u2014 the carrier becomes effectively stiffer with the secondary stage clamped in place. This is specific to ZDS design and does not apply to the ZDE series, where multi-stage adds compliance rather than stiffness.<\/p>\n<\/div>\n<\/div>\n<\/section>\n

<\/p>\n

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When to Specify Torsional Stiffness as the Primary Selection Criterion<\/h2>\n

Torsional stiffness should be the primary accuracy specification \u2014 ahead of backlash \u2014 in four application categories. In all other categories, backlash specification alone is adequate and the EP-ZDE\/ZDF series delivers correct performance at lower cost.<\/p>\n

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\u2460 CNC Heavy-Duty Rotary Tables (B\/C axis)<\/div>\n

Peak cutting torques of 200\u2013800 N\u00b7m in large horizontal machining centres. At these torques, elastic deflection dominates total angular error. Part dimensional tolerance on large workpieces (bore roundness, face perpendicularity) directly reflects gearbox dynamic stiffness. Specify: EP-ZDS-142 or EP-ZDS-190 by torque class.<\/p>\n<\/div>\n

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\u2461 Industrial Robot Joints J1 and J2<\/div>\n

Structurally high inertia ratio at J1\/J2 means servo bandwidth must be limited to avoid resonance. Higher Ct raises the resonant frequency, allowing wider servo bandwidth and better path-tracking accuracy. Additionally, peak dynamic torques during acceleration of large robot arms exceed the ZDE-160 crossover point.<\/p>\n<\/div>\n

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\u2462 Servo Press Main Drive Axes<\/div>\n

Impact forming operations subject the gearbox to impulse torques of 2\u20133\u00d7 the sustained rated value at the moment of part contact. Under impulse load, elastic deflection is instantaneous and the tool tip position deviates from the commanded position. Higher Ct reduces this deviation and improves press forming dimensional consistency. Service factor 2.5+ plus stiffness specification is the correct approach for press drives.<\/p>\n<\/div>\n

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\u2463 Gantry Axes with High-Speed Direction Reversal<\/div>\n

Laser cutting gantries and high-speed pick-and-place systems execute direction reversals at 50\u2013200 times per minute with significant axis inertia. At each reversal, the gearbox must both eliminate backlash dead band and simultaneously absorb the torque transient from decelerating and re-accelerating the load. A stiffer gearbox damps the torque transient faster and reduces position error during the reversal interval. For gantries operating above 3m\/s with sub-0.1mm positioning requirements, consider EP-ZDS-142 even at moderate torque levels.<\/p>\n<\/div>\n<\/div>\n

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When EP-ZDE\/ZDF at Ct=38 N\u00b7m\/arcmin is sufficient:<\/strong> For applications where the peak applied torque is below the crossover point of 304 N\u00b7m for ZDE-160 \u2014 light robot joints (J3\u2013J6), packaging servo axes, AGV drive wheels, solar tracker drives, and conveyor indexers \u2014 backlash is the dominant accuracy parameter and EP-ZDE\/ZDF is the correct and more cost-efficient choice. The higher Ct of ZDS is not needed and the additional cost is not justified by any measurable improvement in application performance.<\/p>\n<\/div>\n<\/section>\n

<\/p>\n

\"Korea<\/p>\n
The higher torsional stiffness of the EP-ZDS series vs EP-ZDE is engineered through three structural changes: a larger output shaft (\u03a655h7 vs \u03a640h7 at the largest frame), a stiffer planet carrier with increased wall thickness, and preloaded output bearings that eliminate clearance in the output shaft support. All three contribute to the 3.4\u00d7 Ct improvement (130 vs 38 N\u00b7m\/arcmin) of ZDS-190 over ZDE-160.<\/div>\n<\/div>\n

<\/p>\n

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A Practical Three-Step Method for Including Torsional Stiffness in Your Selection<\/h2>\n

Most engineers apply service factor and backlash grade but omit torsional stiffness from the selection process entirely. The following three-step method integrates Ct into the standard five-step selection process without adding significant complexity.<\/p>\n

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1<\/div>\n
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Calculate the crossover torque for your candidate gearbox<\/div>\n

T_crossover = BL \u00d7 Ct. For EP-ZDE-160: 8 \u00d7 38 = 304 N\u00b7m. Compare this to your actual peak operating torque (after applying service factor). If peak torque > T_crossover, torsional stiffness is already the dominant accuracy limit and Ct must be increased to improve positioning performance \u2014 tighter backlash specification will not help.<\/p>\n

If T_peak_operating > T_crossover \u2192 specify higher Ct (ZDS series)<\/div>\n<\/div>\n<\/div>\n
\n
2<\/div>\n
\n
Calculate acceptable elastic deflection from your dimensional tolerance<\/div>\n

Determine your machining or positioning tolerance (e.g. \u00b10.1mm at your specific load radius R). Calculate the maximum acceptable elastic deflection: \u03b8_max = arctan(tolerance \/ R) in arcmin. Then calculate the required Ct: Ct_required = T_peak \/ \u03b8_max. Select the EP series unit with Ct \u2265 Ct_required.<\/p>\n

Example: \u00b10.3mm at R=300mm, T_peak=380Nm
\n\u03b8_max = arctan(0.3\/300) \u00d7 3438 = 3.44 arcmin
\nCt_required = 380\/3.44 = 110 N\u00b7m\/arcmin \u2192 specify ZDS-190 (Ct=130)<\/div>\n<\/div>\n<\/div>\n
\n
3<\/div>\n
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Verify resonant frequency is above servo control bandwidth<\/div>\n

Calculate f_resonant = (1\/2\u03c0) \u00d7 \u221a(Ct[N\u00b7m\/rad] \/ J_load). Compare to your servo control bandwidth. For safety, f_resonant should be at least 3\u00d7 the servo Kv gain frequency. If f_resonant is below 3\u00d7 servo BW even with the stiffest appropriate EP series unit, reduce servo bandwidth (accept slower response) or consider reducing load inertia at the output.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n


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

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Need a Torsional Stiffness Analysis for Your Application?<\/div>\n

Korea Ever-Power application engineering provides crossover torque calculation, Ct requirement analysis, and resonant frequency verification for specific applications \u2014 including dimensional tolerance and load radius inputs. Provide your peak operating torque, load radius, and dimensional accuracy requirement to receive a complete stiffness specification recommendation in Korean or English.<\/p>\n<\/div>\n

Request Stiffness Analysis \u2192<\/a><\/p>\n
sales@planetary-gearboxes.com<\/div>\n<\/div>\n<\/div>\n

<\/p>\n

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EP Series \u2014 Torsional Stiffness Specifications<\/div>\n
\n
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EP-ZDS\u7cfb\u5217<\/div>\n
Ct 20\u2013130 N\u00b7m\/arcmin<\/strong> \u00b7 IP65 \u00b7 1,800 N\u00b7m \u00b7 crossover at 1,040 N\u00b7m for ZDS-190 \u2014 torsional stiffness never limits accuracy within rated range<\/div>\n

\u67e5\u770b\u89c4\u683c \u2192<\/a><\/p>\n<\/div>\n

\n
EP-ZDE\u7cfb\u5217<\/div>\n
Ct 0.7\u201338 N\u00b7m\/arcmin<\/strong> \u00b7 crossover at 304 N\u00b7m (ZDE-160) \u00b7 correct choice for torque below 300 N\u00b7m where backlash dominates \u2014 most servo automation applications<\/div>\n

\u67e5\u770b\u89c4\u683c \u2192<\/a><\/p>\n<\/div>\n

\n
EP-ZDF Series<\/div>\n
Same Ct as EP-ZDE by frame \u00b7 square flange for plate-mount structures \u00b7 identical torque and stiffness \u2014 choose ZDF when bore machining is not available<\/div>\n

\u67e5\u770b\u89c4\u683c \u2192<\/a><\/p>\n<\/div>\n<\/div>\n

\u6d4f\u89c8\u5168\u90e8 5 \u90e8\u5267\u96c6 \u2192<\/a><\/div>\n<\/div>\n<\/section>\n

\u7f16\u8f91\uff1aCxm<\/p>\n<\/div>","protected":false},"excerpt":{"rendered":"

Korea Ever-Power Technical Deep-Dive \u00b7 Dynamics Planetary Gearbox Torsional Stiffness Explained \u2014 Why Ct Matters More Than Backlash at High Torque Every precision planetary gearbox datasheet lists backlash in arcminutes. Fewer than 20% list torsional stiffness. Yet under significant applied torque \u2014 the real operating condition of a CNC rotary table, a heavy robot joint, […]<\/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-747","post","type-post","status-publish","format-standard","hentry","category-application-and-technical-guid"],"_links":{"self":[{"href":"https:\/\/planetary-gearboxes.com\/zh\/wp-json\/wp\/v2\/posts\/747","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/planetary-gearboxes.com\/zh\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/planetary-gearboxes.com\/zh\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/zh\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/zh\/wp-json\/wp\/v2\/comments?post=747"}],"version-history":[{"count":1,"href":"https:\/\/planetary-gearboxes.com\/zh\/wp-json\/wp\/v2\/posts\/747\/revisions"}],"predecessor-version":[{"id":748,"href":"https:\/\/planetary-gearboxes.com\/zh\/wp-json\/wp\/v2\/posts\/747\/revisions\/748"}],"wp:attachment":[{"href":"https:\/\/planetary-gearboxes.com\/zh\/wp-json\/wp\/v2\/media?parent=747"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/zh\/wp-json\/wp\/v2\/categories?post=747"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/planetary-gearboxes.com\/zh\/wp-json\/wp\/v2\/tags?post=747"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}