What Is Identical, What Differs — The Complete Specification Comparison
The most important fact about the EP-ZDE versus EP-ZDF selection is this: the two series differ in exactly one respect. Every precision engineering parameter — gear geometry, torque capacity, efficiency, backlash, torsional stiffness, bearing life, lubrication, temperature range, IP rating — is shared between the two series for any given frame size and ratio combination. Selecting ZDF over ZDE, or vice versa, has no effect whatsoever on the gearbox performance in service. It affects only the ease, accuracy, and cost of mounting.
| Specificatieparameter | EP-ZDE Ronde flens |
EP-ZDF Vierkante flens |
Impact on Selection |
|---|---|---|---|
| Gear stages and ratios | Identical ✅ | Identical ✅ | None |
| Nominaal uitgangskoppel | Identical ✅ | Identical ✅ | None |
| Backlash specification | <8 arcmin ✅ | <8 arcmin ✅ | None |
| Torsiestijfheid Ct | Identical ✅ | Identical ✅ | None |
| Efficiency per stage | 96%/94%/90% ✅ | 96%/94%/90% ✅ | None |
| Bearing life (L10) | 20,000h ✅ | 20,000h ✅ | None |
| IP rating | IP54 ✅ | IP54 ✅ | None |
| Temperature range | −25 to +90°C ✅ | −25 to +90°C ✅ | None |
| Output shaft dimensions | Identical ✅ | Identical ✅ | None |
| Housing mounting interface | Round: pilot Ø + bolt circle | Square: 4-bolt flat plate | ★ THE ONLY DIFFERENCE |
| Concentricity reference | Pilot bore → <0.01mm TIR | Shaft alignment only | ★ Affects mounting precision |
| Required mounting structure | CNC-bored precision plate | Flat plate, laser-cut holes | ★ Affects manufacturing cost |
The correct selection principle: Do not choose ZDF to save money — the unit price difference is less than ±5% and should not drive the decision. Do not choose ZDE because it “sounds more precise” — the gear internals are identical. Choose based solely on whether your mounting structure provides (or requires) the pilot bore centering reference that round flange delivers, or whether you need the bolt-on simplicity of square flange for a non-precision mounting surface.
Round Flange (EP-ZDE) — How the Pilot Bore Provides Concentricity
The defining feature of the EP-ZDE round flange is the precision pilot diameter — a short cylindrical register on the gearbox housing face that locates into a matching precision bore in the mounting plate. This pilot-to-bore interface is the mechanical reference that centres the gearbox output shaft relative to the mounting structure with an accuracy better than 0.02mm TIR, achievable without any alignment instruments after installation.
- Output shaft centred to mounting structure: <0.01mm TIR achievable
- Angular squareness of output axis to mounting face: <0.01° achievable
- Repeatable remounting accuracy: within 0.005mm between dismount and reinstall
- No alignment instruments required during installation or replacement
- Self-locating: pilot drops into bore and registers position mechanically
- Precision circular bore to H7 tolerance (e.g. Φ95H7 for ZDE-120)
- Bolt circle holes at correct positions — CNC-machined or jig-drilled
- Flat seating face — surface flatness ≤ 0.02mm over the flange diameter
- Plate material: cast iron, steel, or precision aluminium (not sheet metal)
- CNC machining cost: approximately 90 minutes per plate including inspection
- Rigid coupling to ballscrew — runout causes bearing loads and vibration at speed
- High-speed spindle drive — eccentricity causes imbalance above 3,000 rpm
- Robot joint kinematic chain — concentricity affects arm position accuracy
- Direct-drive precision rotary table — pilot ensures table centreline accuracy
- Laser/optical beam positioning — runout causes beam wander
| Framegrootte | Pilot Diameter | Bolt Circle | Bolt Size | Concentricity Achievable |
Mounting Plate Bore |
|---|---|---|---|---|---|
| ZDE-60 | Φ50h6 | Φ70mm | M5 × 4 | <0.01mm TIR | Φ50H7 bore required |
| ZDE-80 | Φ63h6 | Φ90mm | M6 × 4 | <0.01mm TIR | Φ63H7 bore required |
| ZDE-120 | Φ95h6 | Φ130mm | M8 × 4 | <0.01mm TIR | Φ95H7 bore required |
| ZDE-160 | Φ130h6 | Φ175mm | M10 × 4 | <0.01mm TIR | Φ130H7 bore required |
Square Flange (EP-ZDF) — The Bolt-On Advantage for Fabricated Structures
The EP-ZDF square flange replaces the round pilot-and-bolt-circle with four bolts arranged at the corners of a square pattern on a flat housing face. There is no pilot bore. The gearbox positions against the mounting surface by the four bolt holes alone — any concentricity of the output shaft to the load axis is achieved through the shaft coupling or drive element, not through the housing interface.
- CNC boring of precision circular pilot bore in mounting plate
- CMM or indicator verification of concentricity after installation
- Requirement for precision plate material (cast iron or bored aluminium)
- Press-fit tool for insertion and removal (if interference fit pilot)
- 90-minute per-unit machining cost at CNC machining centre
- Four bolt holes at correct square pattern spacing — laser-cut or punched
- Reasonably flat surface (no precision grinding required)
- Any plate material: sheet steel, stainless, extruded aluminium
- No CNC boring operation: bolt hole pattern included in laser cut program
- Total extra machining cost: zero (or 10 min for optional surface grinding)
- Housing-referenced concentricity — output shaft position depends on coupling
- Automatic squareness of output axis to mounting face
- Repeatable remounting accuracy below 0.05mm without alignment
- Self-locating capability — unit must be positioned by other means
When Housing Concentricity Actually Matters — The Complete Application Analysis
The decision to use ZDE or ZDF hinges on one engineering question: does the application require the gearbox output shaft to be concentric to the load axis by virtue of the housing-to-structure interface? Or does the coupling element between gearbox output and load absorb whatever misalignment results from a non-precision mounting? The answer separates ZDE applications from ZDF applications completely.
| Sollicitatie | Max allowable runout |
Coupling type | Correct series | Why |
|---|---|---|---|---|
| Ballscrew direct coupling | <0.01mm | Rigid or bellows | ZDE | Runout → ballscrew bearing load and noise at speed |
| CNC rotary axis (B/C axis) | <0.02mm | Direct mount | ZDE | Table concentricity affects part roundness — see CNC guide |
| Robot joint (arm structure) | <0.02mm | Machined flange | ZDE | Kinematic chain accuracy propagates joint eccentricity |
| High-speed spindle (>3,000 rpm) | <0.005mm | Rigid | ZDE | Imbalance from eccentricity → vibration, bearing failure |
| Halfgeleiderwafelhandler | <0.005mm | Direct/rigid | ZDE | Sub-micron wafer placement accuracy requirement |
| AGV drive wheel (chassis plate) | ~0.1mm | Hub/keyed shaft | ZDF | Laser-cut chassis plate; tyre compliance absorbs eccentricity |
| Conveyor belt drive (weldment) | ~0.2mm | Sprocket/pulley | ZDF | Fabricated frame; belt/chain absorbs minor misalignment |
| Solar tracker drive (tube/extrusion) | ~0.5mm | Structural coupling | ZDF | Extruded aluminium structure; no bore machining available |
| Packaging machine (sheet metal) | ~0.1mm | Jaw coupling | ZDF | Sheet metal cabinet; jaw coupling absorbs misalignment |
| Food processing conveyor (stainless plate) | ~0.2mm | Sprocket/chain | ZDF | Laser-cut stainless plate; chain drive absorbs eccentricity |
| Rack-and-pinion drive (gantry) | ~0.05mm | Pinion on shaft | ZDF | Lateral float of rack engagement absorbs eccentricity |
| Material handling shuttle (weldment) | ~0.3mm | Gear coupling | ZDF | Rough welded structure; gear coupling absorbs misalignment |
Manufacturing Cost and Installation Time — The Volume Production Case for ZDF
In volume production — AGV manufacturing, conveyor systems, solar farm installations, and packaging machine production — the cumulative manufacturing and installation cost difference between ZDE and ZDF becomes significant. The unit price difference between the two series is less than ±5% and does not drive the economics. What drives the economics is the mounting structure machining and the installation time, both of which are substantially reduced by ZDF.
(500 × $270/unit)
(500 × 14 min)
(identical internals)
For AGV manufacturers producing 500 units/year, switching from ZDE to ZDF on drive units that do not require pilot bore centering (chassis plate mounts, where wheel hub alignment is done via shaft) saves approximately $135,000/year in machining cost alone — with zero impact on AGV drive performance. This calculation is why Korean AGV OEMs standardise on ZDF for chassis-mounted drive units.
Field Serviceability — Why ZDF Is Superior for Remote and Distributed Installations
When a gearbox requires replacement in service — at a solar farm hundreds of kilometres from the nearest CNC machine, on an AGV in a 24/7 logistics warehouse, or in a food processing facility during a production window — the time and skill required for replacement directly affects line availability. The ZDF square flange is dramatically simpler to replace in the field than ZDE.
- Disconnect motor and remove housing fasteners
- Extract pilot from bore — may require puller tool if light interference fit
- Inspect bore for damage or fretting corrosion — repair if needed (cannot replace without this)
- Clean and inspect bore surface
- Insert new unit pilot into bore (alignment automatic if bore is undamaged)
- Torque bolts in star pattern, verify concentricity with dial indicator
- Disconnect motor and remove 4 housing bolts
- Slide old unit off mounting plate
- Position new unit against plate, insert 4 bolts finger-tight
- Torque bolts to specification in cross pattern
- Reconnect motor — done
- (No concentricity verification needed — coupling absorbs alignment)
Critical for solar farms, AGV fleets, and remote installations: When a gearbox fails at a solar farm with 10,000 drive units across a remote site, the replacement must be completed by a field technician with basic tools in the shortest possible time. The ZDF square flange reduces field replacement from a 90-minute specialist operation requiring a dial indicator and puller tool to a 25-minute task requiring only a torque wrench. Across a fleet of thousands of units, this operational advantage compounds significantly over the installation lifetime.
Extending the Analysis: EP-ZDWE vs EP-ZDWF for Right-Angle Input Applications
The same ZDE-versus-ZDF selection principle applies identically to the right-angle input series. EP-ZDWE has a right-angle input stage combined with a round-flange output. EP-ZDWF has a right-angle input stage combined with a square-flange output. Gear internals, torque ratings, and all performance specifications are identical between ZDWE and ZDWF — only the output mounting interface differs, for exactly the same reasons as ZDE versus ZDF.
Motor enters at 90° to the output axis. Output side has a precision pilot bore round flange — same centering capability as EP-ZDE. Use for right-angle applications where the output must be precisely centred: precision rotary tables with right-angle motor placement, robot wrist joints where arm geometry constrains the motor, CNC auxiliary axes with right-angle drive layout.
Concentricity: <0.01mm TIR
Motor enters at 90° to the output axis. Output side has a square four-bolt flange — same bolt-on simplicity as EP-ZDF. Use for right-angle applications with fabricated mounting structures: AGV chassis (motor horizontal in chassis cavity, output to wheel), solar tracker elevation axis (motor along support tube), packaging machine right-angle drives in sheet metal frames. The ZDF square-flange chassis height saving for AGV is detailed in the AGV guide.
Concentricity: via shaft alignment
The right-angle input bevel gear stage in ZDWE/ZDWF adds backlash: <25–30 arcmin total output backlash, versus <8 arcmin for ZDE/ZDF inline units. This is not a function of the output flange type — it is inherent to the bevel input stage. For applications requiring <8 arcmin output backlash, ZDWE and ZDWF are both excluded regardless of flange choice. Use ZDE or ZDF with an inline 90° gearhead if right-angle geometry with tight backlash is required.
The Four-Question Decision Framework — ZDE, ZDF, ZDWE, or ZDWF
The unit price difference between ZDE and ZDF, or between ZDWE and ZDWF, is typically less than ±5% in either direction (varies by frame size and batch quantity). This small price difference is completely dominated by the machining and installation cost implications of the choice. Select on engineering merit — the cost will follow correctly from the right selection, not the other way around.
If the machine design already specifies a precision-bored mounting plate — as is standard in CNC machine tool and robot arm designs — always use ZDE to take advantage of the precision reference that the bore provides. Installing a ZDF into a precision-bored plate wastes the machining investment and forgoes the concentricity benefit that the bore enables.
Korea Ever-Power application engineering advises on ZDE versus ZDF selection based on your specific mounting structure, coupling type, and application concentricity requirement — at no charge for qualified OEM enquiries. Provide your mounting structure description, coupling type, and required output shaft alignment accuracy for a definitive recommendation in Korean and English.
Redacteur: Cxm
