Concentric Precision Planetary Gearbox for High-Speed Servo — VR Series

The VR series concentric planetary gearbox solves a specific integration problem that flange-output reducers cannot: applications where the driven shaft must be co-axial with the motor shaft, the machine envelope prohibits any lateral offset between motor and load, and the speed reduction must be achieved without right-angle or offset gear stages that add length, weight, and backlash. The VR's inline co-axial output keeps motor and load on the same centreline axis — motor shaft in, reduced output shaft out on the same axis — in a housing diameter that adds only the planetary ring gear wall thickness to the motor's own frame diameter.

Two input configurations address the full range of motor coupling scenarios: S-type (solid input shaft) for direct coupling via bellows or jaw couplings to standard motor shafts, and F-type (hollow bore input) for direct motor shaft through-mounting that eliminates the coupling hardware entirely — reducing backlash contribution, cutting assembly time, and minimising overall system length. Frame sizes B through E cover servo motor compatibility from 50 W to 5,000 W with gear ratios spanning 3:1 to 81:1.

VR-S Type — Solid Input Shaft

• ▸ Input shaft keyed for coupling attachment
• ▸ Compatible with any motor via bellows or jaw coupling
• ▸ Accommodates shaft misalignment via coupling selection
• ▸ Suitable for motor replacement without gearbox removal
• ▸ Best for: lab automation, test equipment, general servo

VR-F Type — Hollow Bore Input ★ Most Specified

• ▸ Motor shaft passes through bore — zero coupling hardware
• ▸ Minimum system axial length — motor flange butts directly to gearbox
• ▸ Zero coupling backlash contribution to total system backlash
• ▸ Keyless clamping ring secures motor shaft without key slots
• ▸ Best for: spindle drives, high-speed indexing, space-critical designs

Wafer Chuck & Stage Drives

Semiconductor wafer chuck theta-axis rotation and precision X-Y stage drives use VR Frame B and C for co-axial torque delivery within the stage assembly height limit. Sealed grease prevents cleanroom particle contamination from lubricant vapour that would disqualify conventional oil-lubricated reducers.

Telescope Tracking Drives

Amateur and professional telescope equatorial mount drives require co-axial reduction on both RA and Dec axes. VR series noise-free operation at sidereal tracking speeds (0.0007 rpm output) and low cogging torque prevents the micro-step vibration that blurs long-exposure astrophotography images at focal lengths above 1,000 mm.

Medical Diagnostic Equipment

CT scanner gantry rotation drives and MRI gradient coil actuators operate in environments where any metallic particle or lubricant contamination is unacceptable. VR sealed grease fill and IP54 sealed housing meet medical device contamination control requirements without additional enclosure hardware.

Concentricity verification is an additional acceptance test step unique to VR series — the co-axial output shaft is measured for runout relative to the input bore centreline using a CMM fixture, verifying the core performance claim of the design before shipment.

Factory Acceptance Tests — Every Unit

• ✔ Co-axial concentricity — input to output ≤0.005 mm TIR
• ✔ Backlash measurement per grade
• ✔ Full-load torque test at 110% rated
• ✔ F-type bore clamp torque capacity verification
• ✔ IP54 ingress seal test — pressure differential

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→ Precision CV Drive Shafts

For extended-reach spindle configurations and telescope primary mirror drives where the VR output flange cannot be directly adjacent to the load bearing, precision CV shafts transmit torque with ≤0.005 mm runout contribution — preserving the concentricity advantage that makes VR series the design choice.

• ▸ Runout contribution ≤0.005 mm
• ▸ Lengths 50–500 mm for compact systems

→ Self-Locking Worm Gearbox

Rotary indexing heads with dwell-position holding requirements use a VR pre-stage for speed reduction followed by a worm stage for self-locking dwell. The VR handles the speed reduction efficiently; the worm provides the positive mechanical lock that prevents table creep under load during assembly or test operations.

• ▸ Combined ratios to 6,000:1
• ▸ Self-locking eliminates brake hardware

→ Multi-Output Bevel Stage

Where a single VR output must power two perpendicular axes in a multi-head automation system, a bevel stage downstream splits the co-axial output to two right-angle drives at 96–98% per-stage efficiency — maintaining the system energy efficiency that makes VR series cost-effective over the product lifecycle.

• ▸ Bevel efficiency 96–98%
• ▸ Compact split for tight multi-axis layouts

VR-F Frame C units on our PCB micro-drill heads. The F-type hollow bore reduced our spindle assembly length by 32 mm compared to the previous coupling + standard reducer combination — which was exactly the margin we needed to fit the drill head inside the machine gantry profile. Runout measured at 0.004 mm on all 24 units. 18 months operation, zero failures.

Specified VR-S Frame B across 8 axes of a liquid handling robot for genomics research. The sealed grease was a mandatory requirement for biosafety compliance — no open lubrication within 500 mm of sample handling zones. The Frame B housing diameter fit perfectly within our 40 mm arm link profile. 14 months of daily automated operation with no lubrication-related incidents.

VR-F Frame D for a precision rotary indexing head in a semiconductor die-bonding machine. The co-axial layout was the only solution that fit within the machine's Z-axis column — a 90 mm diameter constraint that eliminated all offset reducers. Indexing cycle time improved 18% versus the previous belt-and-pulley arrangement due to the elimination of belt compliance at high acceleration. Two years operation, zero maintenance.

VR-S Frame C on our astronomical telescope RA axis. The co-axial geometry kept the mount head diameter compact; the low cogging torque eliminated the periodic drive error that was blurring long-exposure images at f/10. No vibration detectable at 5-minute exposures at 1,200 mm focal length. Minor note: longer lead time than standard series — order ahead if delivery timing matters.

QWhat is the difference between VR-S and VR-F type, and how do I choose?

VR-S uses a solid keyed input shaft that couples to the motor via a bellows, jaw, or disc coupling — giving motor selection flexibility and easy motor replacement in the field. VR-F uses a hollow bore with a keyless clamping ring through which the motor shaft passes directly — eliminating coupling hardware, reducing system length, and removing coupling backlash from the total system error budget. Choose F-type when minimum axial length, zero coupling backlash, and permanent motor-gearbox assembly are priorities. Choose S-type when motor replacement access or mixed motor-shaft-diameter compatibility is required.

QHow is VR series different from the PLE/PLF series I'm already using?

PLE/PLF uses a standard flange output arrangement where the output shaft protrudes from the front face — the motor and load shaft centrelines are the same axis, but the planetary housing adds lateral width. VR series achieves true co-axial output where the housing diameter adds only ring gear wall thickness to the motor diameter, enabling significantly more compact axis designs. If your current PLE/PLF design has adequate space, stay with PLE/PLF. If you need to reduce the housing diameter of a spindle or axis column, VR series is the upgrade path.

QWhy is the ratio range limited to 3:1 – 81:1 compared to other series that reach 512:1?

The co-axial arrangement constrains the multi-stage cascade options available. Adding planetary stages within the co-axial envelope increases housing length proportionally — at ratios above 81:1 (typically three stages), the housing length exceeds the dimensional advantage that makes VR series the co-axial choice. For ratios above 81:1 with co-axial requirement, the standard approach is to cascade VR with a worm stage downstream, achieving combined ratios to 6,000:1 while keeping VR's co-axial output flange as the structural datum.

QCan I use VR-F type if my motor shaft has a keyway?

Yes. The keyless clamping ring in the VR-F bore applies symmetric radial clamping force and does not require a smooth shaft. Motor shafts with standard IEC keyways are compatible — the clamping ring spans the keyway without issue. For very heavy shock load applications where keyway stress concentration is a concern, specify VR-S with a coupling that distributes the torque over the full shaft circumference via friction clamping rather than key shear.

QIs VR series suitable for continuous high-speed operation above 3,000 rpm input?

Yes, and it is a specific design advantage of the co-axial architecture. The symmetric mass distribution of VR's planet carrier about the rotational axis eliminates the rotating imbalance that limits usable speed in offset planetary designs. VR series is rated and tested at maximum input speed without vibration derating. For sustained operation above 5,000 rpm, specify Frame B or C (smaller, lighter planet assemblies) and confirm oil temperature stays below 80°C at the selected operating point — contact our engineering team with motor speed and duty cycle for a thermal confirmation.

QWhat motor adapter flanges are available for VR-F type?

IEC B5 and B14 motor flanges are standard for Frame B through E in both S and F types. Standard bore diameters in F-type match IEC motor shaft sizes for the corresponding frame (e.g., Frame C F-type accepts 14 mm, 16 mm, 19 mm, and 24 mm motor shaft diameters with appropriate clamping ring insert). For non-IEC motor flanges including Nema 23/34 and proprietary servo motor housings, custom adapter machining is available with 2-week lead time — provide motor datasheet flange dimensions for a fit confirmation.