Precision gearhead and bellows coupling drive train for a servo-driven pump: backlash plus torsional wind-up
Servo motor, low-backlash gearhead and metal bellows coupling in one line to a dosing or calibration pump · where the angular error between motor and pump shaft comes from
Where a servo motor turns a pump that must deliver a set volume per revolution, the motor's encoder sees its own shaft, not the pump's. Between them sit a low-backlash planetary gearhead and a coupling, and each adds angular error: the gearhead through backlash and torsional rigidity, the coupling through its own torsional stiffness. A metal bellows coupling is chosen here because it has no backlash and still takes small misalignment between gearhead and pump shafts. This page adds those errors up from published data.
The drive line between a servo motor and a rotary pump or similar precision load: a low-backlash planetary gearhead on the motor and a metal bellows coupling to the load shaft, judged by backlash, torsional rigidity and misalignment. Jaw, disc, diaphragm, gear and grid couplings with application service factors are covered on the Shaft coupling page; planetary reducer ratios, stages and tooth-count rules are covered on the Planetary gear reducer page.
CNFX editorial research · Sources checked October 12, 2026 · 4 sources
A 1-stage NP015S gearhead: ≤ 8 arcmin backlash and 2.8 Nm/arcmin rigidity at a 19 Nm nominal torque
Wittenstein's data sheet for the NP015S-MF1-10-1D1-1S, a single-stage low-backlash planetary gearhead with ratio 10, gives a maximum torsional backlash of 8 arcmin or less, a torsional rigidity Ct21 of 2.8 Nm/arcmin and a tilting rigidity of 17 Nm/arcmin. [1] Its nominal output torque is 19 Nm, the maximum output torque 56 Nm and the emergency-stop torque 80 Nm, permitted 1000 times in the gearhead's life. [1]
The same sheet lists 97% efficiency at full load, 4300 rpm nominal and 8000 rpm maximum input speed, IP 64, lubrication for life, a 90 °C maximum housing temperature and 1.9 kg with the standard adapter plate; rigidity depends on the clamping hub diameter, 16 mm on this variant. [1]
A two-stage gearhead trades ratio for different figures: Anaheim Automation's GBPS-1422-NM-030, ratio 30 in two stages, lists 3 arcmin maximum backlash, 45 Nm/arcmin torsional rigidity and 94% efficiency. [2] Backlash is lost motion on each reversal; rigidity sets how far the output twists under load once the gears are in contact.
Editorial calculation treats rigidity as linear up to the torque shown; Wittenstein marks the rigidity value as dependent on the clamping hub diameter.
02
Bellows coupling at the pump: 128,000 Nm/rad with 0.2 mm offset, or 75,000 Nm/rad with 0.25 mm
HucoFlex K bellows couplings have aluminium alloy hubs, a stainless steel bellows and a removable clamp shaft connection. Two versions of the 82 mm diameter size show the trade-off between stiffness and misalignment: part 592.82, 91 mm long, has 128,000 Nm/rad torsional stiffness and takes 1.5° angular and 0.2 mm radial misalignment; part 593.82, 102 mm long, has 75,000 Nm/rad and takes 2° and 0.25 mm. [3][4]
Both are rated 150 Nm peak, 6900 rpm, −30 to +120 °C, bores 22 to 42 mm, and clamp with M10 screws tightened to 84 Nm. [3][4]
Editorial calculation at 19 Nm, converting rad to arcmin with 1 rad ≈ 3437.7 arcmin: the 592.82 twists 19 / 128,000 rad ≈ 0.51 arcmin and the 593.82 19 / 75,000 rad ≈ 0.87 arcmin. Added to the NP015S's 6.8 arcmin wind-up, the drive line twists about 7.3 to 7.7 arcmin at the pump shaft, before the gearhead's up to 8 arcmin backlash on reversal. The coupling contributes about 7% (592.82) to 11% (593.82) of that elastic twist; the gearhead contributes the rest.
Editorial calculation; the HucoFlex size shown is rated far above the NP015S's torque and its 22–42 mm bores must be checked against the actual gearhead and pump shafts.
03
Data for a gearhead and coupling to drive a pump
Paste it into your enquiry below or into an email to a maker, then replace every bracket.
Load: [pump type; torque nominal and peak in Nm; speed range; reversing or one direction]
Accuracy: [allowed angular error at the pump shaft in arcmin; volume per revolution]
Gearhead: [ratio; backlash class; torsional rigidity; motor flange and shaft]
Coupling: [bores both sides; torsional stiffness; expected angular, radial and axial misalignment]
Environment: [ambient temperature; washdown; IP rating]
2 companies list this product among what they make. Company figures are quoted from each
company's own website; every card states where the relationship came from.
Changzhou Sunrise Electric Motor Co., Ltd.
Manufacturing site to be confirmed for the order
Lists precision planetary gearboxes alongside servo motors and motors with planetary gearboxes.
Explore company information and manufacturing capabilities, then discuss the scope of your project with a relevant supplier.
Share this page
Compiled and source-reviewed by the CNFX editorial team.
Each manufacturer above links to the page on that company's own website where the product is listed, with the date we checked it. How we source and review
· Page last updated 13 October 2026
Buyer questions
How much does a low-backlash gearhead twist under load?
Editorial calculation: the Wittenstein NP015S at 2.8 Nm/arcmin twists about 6.8 arcmin at its 19 Nm nominal torque, on top of up to 8 arcmin backlash. [1]
How stiff is a metal bellows coupling?
HucoFlex K couplings of 82 mm diameter list 128,000 Nm/rad for the 91 mm part 592.82 and 75,000 Nm/rad for the 102 mm part 593.82. [3][4]
What misalignment can such a bellows coupling take?
Part 592.82 takes 1.5°, 0.2 mm radial and 0.5 mm axial; part 593.82 takes 2°, 0.25 mm and 0.5 mm. [3][4]
Does a two-stage gearhead have to be less accurate?
Not in the data shown: Anaheim Automation's two-stage GBPS-1422-NM-030 lists 3 arcmin maximum backlash and 45 Nm/arcmin rigidity. [2]
Sources and what still needs a direct check
Sources checked 2026-10-12. Gearhead backlash, rigidity and ratings come from Wittenstein's NP015S product data sheet and Anaheim Automation's GBPS-1422 listing; coupling stiffness and misalignment from the HucoFlex K data sheets for parts 592.82 and 593.82. Values apply to the parts named.
