{"id":750,"date":"2026-06-03T01:55:14","date_gmt":"2026-06-03T01:55:14","guid":{"rendered":"https:\/\/planetary-gearboxes.com\/?p=750"},"modified":"2026-06-03T01:55:14","modified_gmt":"2026-06-03T01:55:14","slug":"right-angle-planetary-gearbox-vs-inline-axial-depth-calculation-zdwe-zde","status":"publish","type":"post","link":"https:\/\/planetary-gearboxes.com\/nl\/right-angle-planetary-gearbox-vs-inline-axial-depth-calculation-zdwe-zde\/","title":{"rendered":"Planetaire tandwielkast met haakse ingang versus inline-tandwielkast \u2014 Berekening van de axiale diepte"},"content":{"rendered":"
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Korea Ever-Power<\/span>
\nInstallation Design Guide<\/span><\/div>\n

Right-Angle Input Planetary Gearbox vs Inline \u2014 Axial Depth Calculation and the Decision Framework for Choosing EP-ZDWE Over EP-ZDE<\/h1>\n

The choice between a right-angle input and an inline precisie planetaire tandwielkast<\/a> is settled by one question: can your machine accommodate the full axial stack of gearbox plus motor? If the answer is no \u2014 and in compact machine heads, AGV chassis, and collaborative robot wrists it frequently is \u2014 then right-angle input is not a compromise. It is the correct engineering answer. This guide gives you the numbers to make that call with confidence.<\/p>\n

Get Installation Depth Calculation Support \u2192<\/a><\/p>\n<\/div>\n<\/div>\n<\/section>\n

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The Fundamental Geometry: Why Right-Angle Input Changes the Space Equation<\/h2>\n

In an inline (coaxial) precision planetary gearbox, the servo motor mounts directly behind the gearbox along the same axis as the output shaft. The total axial installation depth is therefore the sum of the gearbox body length (L1) plus the motor length (L_motor) \u2014 both occupy the same axis behind the output face. In most industrial machine designs, this combined depth is the constraint that limits how close the output shaft can be to a structural wall, a bearing block, or another mechanism.<\/p>\n

A right-angle input precision planetary gearbox (EP-ZDWE or EP-ZDWF series) incorporates a bevel gear stage at the input that turns the motor shaft 90\u00b0 relative to the output shaft. The motor now exits perpendicular to the output shaft axis. The total axial installation depth behind the output face is only the gearbox body length L1<\/strong> \u2014 the motor is housed in the perpendicular direction and does not add to the axial depth behind the output face at all.<\/p>\n

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Inline Configuration (ZDE \/ ZDF)<\/div>\n
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Axial depth = L1_gearbox + L_motor<\/div>\n
Example (80-frame, 750W):<\/div>\n
= 144mm + 100mm = 244mm<\/strong><\/div>\n<\/div>\n
Motor and gearbox stack coaxially behind the output shaft. Both L1 and L_motor consume axial space in the machine envelope.<\/div>\n<\/div>\n
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Right-Angle Input (ZDWE \/ ZDWF) \u2605<\/div>\n
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Axial depth = L1_gearbox only<\/div>\n
Example (80-frame, 750W):<\/div>\n
= 184.5mm only \u2192 saves 59.5mm<\/strong><\/div>\n<\/div>\n
Motor exits 90\u00b0 into perpendicular space. Only L1 determines axial depth. Motor length becomes a perpendicular (height or width) constraint instead.<\/div>\n<\/div>\n<\/div>\n
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Critical trade-off to keep in mind:<\/strong> The right-angle input approach saves axial depth but introduces a perpendicular height constraint (L12 \u2014 the total assembly height including the motor mounted at 90\u00b0). On an 80-frame ZDWE, L12 = 119.5mm. The machine must accommodate 119.5mm in the perpendicular direction to mount the motor. On a compact machine this may be acceptable; on a very flat machine it may introduce a new constraint. Both axial and perpendicular dimensions must be verified before specifying the right-angle configuration.<\/p>\n<\/div>\n<\/section>\n

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\"EP-ZDWE<\/p>\n
The EP-ZDWE series planetary gearbox<\/a> bevel gear input stage turns the servo motor 90\u00b0 relative to the output shaft axis \u2014 removing the motor from the axial space behind the output face. Available in 4 frame sizes: 60mm, 80mm, 120mm, and 160mm. Torque ratings and gear ratios match the inline EP-ZDE series exactly at each frame size.<\/div>\n<\/div>\n

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The Axial Depth Calculation \u2014 All Four Frame Sizes, Both Stage Options<\/h2>\n

The following tables use verified EP series dimensional data (L1 values from the official EP-ZDE and EP-ZDWE product specifications) combined with a reference 750W servo motor length of 100mm \u2014 a representative value for this power class from Mitsubishi, Panasonic, and Yaskawa. Adjust the motor length to your actual motor for an exact result.<\/p>\n

Single-Stage (Ratio 3:1 to 10:1)<\/h3>\n
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Kader<\/th>\nZDE L1<\/th>\n+ Motor (750W)<\/th>\nZDE Total Axial<\/th>\nZDWE L1<\/th>\nAxial Saved<\/th>\nSaving %<\/th>\nZDWE Height L12<\/th>\n<\/tr>\n<\/thead>\n
60 mm<\/td>\n113.5 mm<\/td>\n100 mm<\/td>\n213.5 mm<\/td>\n150.0 mm<\/td>\n63.5 mm \u2193<\/td>\n29.7%<\/td>\n93.0 mm<\/td>\n<\/tr>\n
80 mm<\/td>\n144.0 mm<\/td>\n100 mm<\/td>\n244.0 mm<\/td>\n184.5 mm<\/td>\n59.5 mm \u2193<\/td>\n24.4%<\/td>\n119.5 mm<\/td>\n<\/tr>\n
120 mm<\/td>\n195.2 mm<\/td>\n100 mm<\/td>\n295.2 mm<\/td>\n249.2 mm<\/td>\n46.0 mm \u2193<\/td>\n15.6%<\/td>\n167.5 mm<\/td>\n<\/tr>\n
160 mm<\/td>\n291.0 mm<\/td>\n100 mm<\/td>\n391.0 mm<\/td>\n368.0 mm<\/td>\n23.0 mm \u2193<\/td>\n5.9%<\/td>\n229.0 mm<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

L1 values from official EP-ZDE and EP-ZDWE dimensional specifications. Motor length 100mm = reference 750W servo (Mitsubishi HG-SR or equivalent). L12 = total assembly height of ZDWE unit (perpendicular to output shaft axis). Actual savings scale proportionally with your motor length \u2014 longer motors produce larger absolute savings.<\/p>\n

Two-Stage (Ratio 9:1 to 64:1)<\/h3>\n
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Kader<\/th>\nZDE 2-stage + Motor<\/th>\nZDWE 2-stage L1<\/th>\nAxial Saved<\/th>\nSaving %<\/th>\nBest for<\/th>\n<\/tr>\n<\/thead>\n
60 mm<\/td>\n226.5 mm<\/td>\n163.0 mm<\/td>\n63.5 mm \u2193<\/td>\n28.0%<\/td>\nCobot wrist, small AGV, compact arms<\/td>\n<\/tr>\n
80 mm<\/td>\n262.0 mm<\/td>\n202.5 mm<\/td>\n59.5 mm \u2193<\/td>\n22.7%<\/td>\nMachine head spindle, industrial robot J4<\/td>\n<\/tr>\n
120 mm<\/td>\n323.0 mm<\/td>\n277.0 mm<\/td>\n46.0 mm \u2193<\/td>\n14.2%<\/td>\nHeavier indexing heads, transfer arms<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n
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How to calculate your specific axial depth saving<\/div>\n
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Axial saving = (ZDE_L1 + L_motor_actual) \u2212 ZDWE_L1<\/div>\n
Example with 1.5kW motor (L_motor = 138mm), 80-frame:<\/div>\n
Saving = (144 + 138) \u2212 184.5 = 282 \u2212 184.5 = 97.5mm (34.6%)<\/strong><\/div>\n
Rule: The longer your motor, the greater the absolute saving. Right-angle input is most compelling with high-power, physically long servo motors.<\/div>\n<\/div>\n<\/div>\n<\/section>\n

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Five Machine Design Scenarios Where Right-Angle Input Is the Correct Engineering Choice<\/h2>\n

Right-angle input is not always better \u2014 it introduces a bevel gear stage that adds approximately 2% efficiency loss and widens backlash to <25\u201330 arcmin. The axial depth saving justifies these trade-offs only when the saved depth actually enables a design that would otherwise be infeasible or requires structural compromises. The five scenarios below represent the most common situations in Korean servo automation engineering where right-angle input delivers decisive value.<\/p>\n

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1<\/div>\n
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Compact Machine Spindle Heads \u2014 Depth Limit Imposed by Adjacent Structure<\/div>\n

CNC tool spindle heads, laser cutting heads, and waterjet nozzle assemblies often have a hard depth limit imposed by proximity to the machine column or a structural wall. In these configurations, the available depth between the output shaft face and the machine structure may be 180\u2013210mm \u2014 insufficient for a ZDE-80 plus motor (244mm) but exactly right for a ZDWE-80 (184.5mm). The right-angle input allows the motor to route along the back face of the machine column rather than projecting behind the gearbox.<\/p>\n

Typical saved depth: 40\u2013100mm | Recommended: EP-ZDWE-80, 1 or 2-stage<\/div>\n<\/div>\n<\/div>\n
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2<\/div>\n
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AGV and AMR Low-Profile Chassis \u2014 Chassis Height Is the Critical Dimension<\/div>\n

Low-profile AGVs targeting chassis heights of 100\u2013160mm require the drive gearbox plus drive wheel to fit within this envelope. An inline motor-gearbox stack projects upward into the chassis body. With a right-angle input EP-ZDWF unit (square flange, for direct plate mounting), the motor is positioned horizontally inside the chassis body and only the gearbox L1 protrudes downward toward the drive wheel. This layout is standard in flat AMR designs from Korean manufacturers in Hwaseong and Ansan.<\/p>\n

Recommended: EP-ZDWF-80<\/a> (no bore needed for chassis plate mount)<\/div>\n<\/div>\n<\/div>\n
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3<\/div>\n
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Collaborative Robot Wrist Joints \u2014 Wrist Diameter Target Drives the Decision<\/div>\n

Korean cobot OEMs target wrist outer diameters of 60\u2013100mm. At J4 and J5, the wrist diameter is directly determined by what fits inside the arm cross-section. An EP-ZDWE-60 with the motor exiting perpendicular has L12 = 93mm \u2014 fitting within a 100mm wrist. An inline EP-ZDE-60 plus motor stack at 213.5mm makes the wrist 2\u00d7 longer, adding distal mass and reducing reach. See the robot joint selection guide for the full J1\u2013J6 analysis. The closed-loop position feedback of the servo controller fully compensates for the ZDWE’s wider (<30 arcmin) backlash at these joints.<\/p>\n

Recommended: EP-ZDWE-60 (10:1) \u2014 L12 = 93mm fits 100mm wrist target<\/div>\n<\/div>\n<\/div>\n
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4<\/div>\n
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Cable and Pneumatic Routing Constraints \u2014 Motor Must Exit Non-Axially<\/div>\n

Some machine designs require the motor power cable and encoder cable to be routed away from the gearbox output face \u2014 either to avoid cable fouling during rotation or to route through a cable chain that only has space on the side of the assembly. Right-angle input places the motor on the side, allowing cables to route laterally through cable chains designed for perpendicular cable exit. This is common in gantry systems with long horizontal travels where cable management is a significant design consideration.<\/p>\n

Recommended: Specify motor exit direction (Left\/Right\/Up\/Down) at time of order<\/div>\n<\/div>\n<\/div>\n
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5<\/div>\n
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Press Transfer Feeders \u2014 Tight Stroke Clearance Behind Drive Assembly<\/div>\n

Press transfer feeders and servo-driven part transfer arms often operate inside a press gap with defined clearance behind the output shaft. A transfer arm running between press strokes may have 190mm of clearance behind the drive shaft \u2014 enough for an EP-ZDWE-80 (184.5mm) but not for an EP-ZDE-80 plus motor (244mm). The 59.5mm difference is the difference between a design that clears the press frame and one that interferes. Right-angle input in these applications is not a convenience \u2014 it is what makes the machine physically possible.<\/p>\n

Verify: ZDWE-80 L1 = 184.5mm < 190mm clearance \u2705<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/section>\n

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\"EP-ZDE<\/p>\n
The EP-ZDE inline series planetary gearbox<\/a> remains the preferred choice when axial depth is available \u2014 96% efficiency (vs 94% for ZDWE), <8 arcmin backlash (vs <25\u201330 arcmin), and simpler installation without a prescribed motor exit direction. Choose ZDWE only when the axial depth saving enables a design that the ZDE cannot achieve.<\/div>\n<\/div>\n

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The Trade-Offs Quantified \u2014 Efficiency, Backlash, and Temperature<\/h2>\n

Every right-angle input planetary gearbox carries three inherent characteristics relative to its inline equivalent at the same frame size. These are not quality deficiencies \u2014 they are the physical consequences of adding a bevel gear stage to turn the input 90\u00b0. Understanding their actual magnitude prevents both over-specification (specifying inline unnecessarily) and under-specification (using right-angle input without accounting for the differences).<\/p>\n

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\u2460 Efficiency: 2% reduction per stage<\/div>\n

The bevel gear input stage has its own mesh efficiency of approximately 97\u201398%. Combined with the planetary stage efficiency of 96% (1-stage), the total ZDWE 1-stage efficiency is approximately 94%. Two-stage ZDWE efficiency is approximately 92% vs 94% for ZDE 2-stage.<\/p>\n

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Annual cost of 2% efficiency loss:<\/div>\n
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400W motor: +8W \u2192 +16 kWh\/yr \u2192 $1.6\/yr<\/strong><\/div>\n
750W motor: +15W \u2192 +30 kWh\/yr \u2192 $3.0\/yr<\/strong><\/div>\n
1,500W motor: +30W \u2192 +60 kWh\/yr \u2192 $6.0\/yr<\/strong><\/div>\n<\/div>\n
@$0.10\/kWh Korean industrial rate, 8h\/day, 250 days\/year, continuous duty<\/div>\n<\/div>\n

Conclusion:<\/strong> For intermittent-duty machines (robot joint cycles, press feeders), the actual efficiency cost is a fraction of this. For 24\/7 continuous-duty machinery, verify the housing temperature budget \u2014 the additional heat generation may require forced cooling.<\/p>\n<\/div>\n

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\u2461 Backlash: wider due to bevel stage clearance<\/div>\n

The bevel gear input stage adds its own angular clearance (approximately 15\u201320 arcmin) to the planetary stage backlash (<8 arcmin for ZDE). The total ZDWE backlash is therefore <25 arcmin (frame 80\u2013160, 1-stage) and <30 arcmin (frame 60, 1-stage). This is not a measurement of lower quality \u2014 it is an inherent geometric property of bevel gears that applies to all manufacturers.<\/p>\n

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Config<\/th>\nVerzet<\/th>\nLinear error at R=200mm<\/th>\n<\/tr>\n<\/thead>\n
ZDE-80 (1-stage)<\/td>\n<8 arcmin<\/td>\n0.47 mm<\/td>\n<\/tr>\n
ZDWE-80 (1-stage)<\/td>\n<25 arcmin<\/td>\n1.45 mm<\/td>\n<\/tr>\n
ZDWE-60 (1-stage)<\/td>\n<30 arcmin<\/td>\n1.75 mm<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

For servo closed-loop axes:<\/strong> The servo position feedback loop compensates for the backlash dead band completely during normal position-controlled operation. ZDWE backlash only matters for open-loop stepper motor drives \u2014 which should not be used in precision planetary gearbox applications anyway.<\/p>\n<\/div>\n

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\u2462 Motor exit direction: fixed at order, plan cable routing early<\/div>\n

Unlike inline configurations where the motor simply bolts to the rear of the gearbox in one defined orientation, right-angle input gearboxes can be ordered with the motor exiting in four directions: Left (L), Right (R), Up (U), or Down (D) \u2014 as viewed from the output shaft. This direction is fixed by the bevel gear housing design and cannot be changed in the field after manufacturing.<\/p>\n