Engineering Context
Why CNC Machining Centers Demand ≤1 Arc-Min Backlash — And What Happens When They Don’t Get It
A CNC 5-axis machining center performing a simultaneous B/C-axis contour at feed rates above 6,000 mm/min generates reversal errors that, in the absence of a P0-grade planetary gearbox, translate directly into surface finish defects. For precision component manufacturers — turbine blades, implant housings, aerospace brackets — this is not a quality issue. It is a reject rate issue.
Backlash Grade Impact on Table Positioning Accuracy — Practical Comparison
The following comparison shows the achievable table-surface linear positioning accuracy for each backlash grade at a typical 315 mm table radius, with and without servo compensation. This data is based on customer acceptance test results reported across Korean and Japanese CNC machine builder applications.
±0.005 mm
±0.09 mm
±0.05 mm
±0.28 mm
±0.75 mm
Bars represent relative positional capability (longer = better). Values at r = 315 mm table radius.
Application Scenarios
Six Specific CNC Applications — Which EP-Series for Each Drive Point
Korea Ever-Power EP-series planetary gearboxes are specified across the full range of precision CNC servo drive applications — from the most demanding 5-axis rotary table to high-volume ATC cycle drives and laser cutting gantries. Each drive point has different requirements. The correct series selection prevents over-specification (cost waste) and under-specification (quality failure).
Technical Data
EP-Series CNC Application Specification — Complete Comparison Table
Use the table below to match your specific CNC drive point to the correct EP-series before requesting datasheets or contacting the engineering team.
| Series | Output Interface | Frame Sizes | P0 Backlash | Max Torque | Max rpm | Life (hr) | Primary CNC Application |
|---|---|---|---|---|---|---|---|
| EP-FAB | Square flange — Inline | 042–220 mm | ≤1 arc-min | 2,000 Nm | 6,000 | 20,000 | B/C-axis rotary table; ATC cam drive |
| EP-FABR | Square flange — 90° R/A | 042–220 mm | ≤2 arc-min | 2,000 Nm | 4,000 | 20,000 | Right-angle CNC axis; dial index tables |
| EP-FAD | Round flange — Inline | 047–255 mm | ≤1 arc-min | 2,000 Nm | 10,000 | 30,000 | Trunnion tilt axis; high-speed spindle servo |
| EP-FADS | Direct-insert — No adapter plate | 047–255 mm | ≤1 arc-min | 2,000 Nm | 10,000 | 30,000 | Fixed-motor axis; minimum axial length |
| EP-FAL | Inline + integrated belt pulley | 070–280 mm | ≤1 arc-min | 2,000 Nm | 5,000 | 30,000* | Laser/CNC gantry X/Y belt drive (inline motor) |
| EP-FALR | 90° R/A + integrated belt pulley | 070–280 mm | ≤2 arc-min | 2,000 Nm | 4,000 | 30,000* | Corner-drive gantry; stone/wood CNC; plasma cutter |
| EP-FPG | Round housing — Economy | 040–160 mm | ≤8 arc-min | 423 Nm | 4,000 | 20,000* | Chip conveyor; workpiece transfer (non-precision) |
* FAL/FALR: 30,000 hr S5 intermittent; 15,000 hr S1 continuous. FPG: 20,000 hr S5; 10,000 hr S1.
When specifying against the table above, keep in mind that the design life figures for all premium EP-series (FAB through FALR) assume the rated load torque is calculated correctly — specifically, using mean load torque rather than peak torque. A B/C-axis rotary table that peaks at 180 Nm during aggressive 5-axis contouring but spends 70% of its operating time at 40 Nm mean load will have a service life 3–5× longer than a calculation based on peak torque alone. Korea Ever-Power engineering team can assist with L10h service life calculations for any duty cycle profile — include your motor rated torque, application duty cycle, and required service interval in your enquiry to the engineering team.
Engineering Insight
Inside the EP-FAB / EP-FAD — What Makes a P0-Grade CNC Gearbox Different
Selection Guide
CNC Gearbox Selection Decision Matrix — 5 Questions to the Right Series
This decision matrix covers the five selection dimensions that determine which EP-series is correct for your specific CNC drive point. Work through Q1 to Q5 in sequence — each question narrows the options before the next. For most CNC machining center applications, the decision tree leads to either EP-FAB or EP-FAD at P0 grade for the precision axes, EP-FALR for any gantry corner-drive, and EP-FAB or EP-FAD at P1 grade for the ATC and pallet transfer drives. The EP-FPG/FPGA economy series is appropriate for chip conveyor, coolant pump, and workpiece transport drives within the same machine — all of which can be qualified with the same C1–C10 motor adapter system as the precision axes, eliminating separate procurement workflows.
Manufacturing Quality
Korea Ever-Power Manufacturing — How DIN 5 Accuracy Is Verified in Ansan-si
Korea Ever-Power EP-FAB/FAD vs. European Premium — Technical Attribute Comparison
Korea Ever-Power EP-FAB and EP-FAD are manufactured to the same technical specification as the European premium brands they replace. The comparison below is factual and technically verifiable. We do not claim to manufacture identical products; we claim to manufacture to the same governing standards.
| Technical Attribute | European Premium (Apex, Neugart) |
Korea Ever-Power EP-FAB / EP-FAD |
Korea Ever-Power EP-FPG (Economy) |
|---|---|---|---|
| Gear accuracy class | ✓ DIN Class 5 | ✓ DIN Class 5 (5-axis CNC) | DIN Class 6–7 |
| Backlash verification | ✓ Individual unit stamp | ✓ Individual unit stamp | Batch sample |
| P0 grade available | ✓ Yes | ✓ Yes (stamped per unit) | ✗ No |
| Special ratios (i=21/31) | Custom order only | ★ Standard catalogue | ✗ No |
| IP65 testing | Sample test | ✓ Every unit | IP64 (sample) |
| Motor adapter system | Brand-specific | ✓ C1–C10 universal | ✓ C1–C10 universal |
| Relative unit price (P1) | 100% (benchmark) | ★ ~60–75% | ★ ~35–50% |
Korea Ever-Power does not sell counterfeit products and does not claim to manufacture products identical to named brands. Comparative data is based on publicly available specifications and customer substitution tests.
Customer Feedback
From CNC Machine Builders and End Users — What Changes When You Switch to EP-FAB/FAD
The following three case summaries are drawn from Korea Ever-Power customer applications in CNC machining, laser cutting, and precision milling. All performance data is reported by the customer.
“We replaced an EP-FAB090-P1 on our 5-axis PCB drilling machining center with EP-FAB090-P0 after a 12-month backlash growth issue. The P0 unit has now run 14 months of 3-shift operation with zero measured backlash growth. The motor adapter system saved 3 weeks of custom bracket procurement.”
“On our CNC router Y-axis, we were getting a 0.08 mm periodic position error with EP-FAB110 plus a separate belt pulley hub. After switching to EP-FAL110, the error dropped to 0.015 mm. That one change moved us from grade C to grade A on our customer’s acceptance test. We’ve now standardised EP-FAL on all new gantry builds.”
“We specified EP-FALR190 on a stone CNC machining centre where the motor folds behind the end plate perpendicular to gantry travel. The right-angle layout gave us 185 mm more working length. IP65 has been clean after 18 months — no stone slurry ingress, no seal maintenance required.”
Complete Product Range
Browse the Full EP-Series — All Eight Planetary Gearbox Lines
Korea Ever-Power manufactures eight planetary gearbox series covering every servo integration scenario in CNC, robotics, semiconductor, packaging, and logistics automation — all from one supplier qualification.
For the complete CNC servo drivetrain, Korea Ever-Power planetary gearboxes can be paired with precision CV joint drive shafts for flexible coupling between gearbox and table, or with worm gear reducers where a lower-cost secondary stage is appropriate for non-precision chip and coolant conveyor drives.
Get the Right Series, Grade and Frame Size for Your CNC Drive Point
Send our engineers your servo motor model, required torque, reduction ratio, and duty cycle. We respond within 24 business hours with a confirmed series recommendation, P0/P1 grade specification, motor adapter ring selection, and delivery lead time — at no charge and with no obligation to order.
Frequently Asked Questions
Planetary Gearbox for CNC Machining — Engineering FAQ
Technical questions most commonly asked by CNC machine builders and production engineers when specifying planetary gearboxes for rotary table, ATC, gantry, and multi-axis CNC applications.
What backlash grade do I actually need for a 5-axis CNC machining center B/C-axis rotary table?
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For JIS Class-1 positioning accuracy on a B/C-axis rotary table — the standard required by most 5-axis machining center builders to pass customer acceptance testing — P0 (≤1 arc-min) is mandatory. At a table radius of 300–350 mm, 1 arc-min of backlash translates to approximately 0.087–0.102 mm of linear positioning uncertainty. Most customer acceptance specifications for 5-axis machining centers require ±0.005 mm or better with servo compensation, which is achievable only with a P0-grade gearbox providing the low backlash floor that the servo system can compensate around.
P1 (≤3 arc-min) is acceptable for ATC cam drives and pallet transfer mechanisms where the positioning requirement is less stringent (typically ±0.1 mm or greater). P2 (≤5 arc-min) is suitable for non-precision conveyor and chip-handling drives in the CNC environment.
Can I use EP-FAD instead of EP-FAB on a CNC rotary table, and what is the practical difference?
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Yes — both EP-FAB and EP-FAD are available in P0 grade and both achieve ≤1 arc-min backlash. The practical difference is the output interface and design life:
EP-FAB: Square bolt-pattern flange output. Standard for machining center rotary table builders using bolt-circle square-flange table interfaces. 20,000 hr design life at S1 continuous duty. 6,000 rpm max input.
EP-FAD: Round bolt-circle flange output. Required for tables with round-flange interface standards (common in Japanese machine designs and trunnion-type tables). 30,000 hr design life. 10,000 rpm max input. Special ratios i=16/21/31/61/91 available in standard production for non-standard reduction requirements.
Why does the EP-FAL integrated belt pulley reduce periodic position error compared to a separate pulley hub assembly?
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The periodic position error in a conventional gantry drive (gearbox output shaft + separate pulley hub + keyway + set screw) arises from dimensional tolerance stack between the output shaft and the hub bore — typically ±0.005–0.015 mm TIR — and any angular misalignment at the shaft-to-hub interface.
This eccentricity error appears in the gantry axis position feedback at the spatial frequency corresponding to one pulley revolution — hence the characteristic “periodic” nature of the error. At AT10 belt pitch and typical pulley sizes, this frequency falls within the bandwidth of the CNC interpolation algorithm, producing the banding pattern visible in machined surfaces.
In EP-FAL, the timing belt pulley bore IS the gearbox output shaft — there is no shaft-to-hub interface. The pulley teeth are concentric with the output bearing to ±0.003 mm TIR. This is why EP-FAL users report periodic position error reductions of 5–6× compared to the equivalent FAB + separate hub assembly.
How does the C1–C10 universal motor adapter system work, and which servo motor brands are covered?
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The C1–C10 clamp-ring adapter system consists of a split clamp-ring collar machined to match the specific motor’s shaft diameter, shoulder diameter, and flange bolt pattern on one side, and the EP-series gearbox input bore and flange on the other side.
Covered motor families include: Siemens 1FT6, 1FK7, 1FT7; Yaskawa Sigma-5, Sigma-7, Sigma-X; Mitsubishi HG-SR, HG-KR, HG-RR; Panasonic MHMD, MHME; Bosch Rexroth MSK, MKD; ABB BSM, BSW; and several hundred additional frames from Lenze, Parker, Allen-Bradley, and Kollmorgen families.
Key procurement advantage: once a C-series adapter ring is validated for a given motor model, it fits the same frame size across all EP-series — FAB, FAD, FADS, FAL, FALR, and FPG. A CNC machine builder qualifying one motor model qualifies it for the complete EP-series range simultaneously.
What is the correct EP-series for a CNC gantry laser cutting machine with a corner-drive layout (motor behind the end plate)?
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For a corner-drive gantry layout — where the servo motor is mounted perpendicular to the direction of belt travel (behind the gantry end plate) — the correct series is EP-FALR. This series provides a 90° right-angle output combined with an integrated timing belt pulley, so the motor can be oriented at 90° to the belt with no separate bevel stage or external pulley hub required.
The practical advantages for a CNC laser cutting machine are:
1. +180 mm working length: the motor folds behind the end plate, recovering the axial space that an inline motor + right-angle attachment would occupy.
2. F_rad up to 34,200 N: no external support bearing or pillow block required for the belt pulley shaft.
3. Ratios to 180:1 in a single unit: covers the full speed reduction requirement without a tandem gearbox stage. EP-FALR is available in frame sizes 070–280 mm; typical gantry laser applications use 110–190 mm frames at P1 grade.
Editor: Cxm
