Drives for machine tools and metalworking: servo systems, hydraulics, couplings
Today's metal-cutting and sheet-metal fleet is built on high-precision servo systems. Main spindles of machining centers and CNC lathes run across a wide speed range with torque control, feed drives must position to single-digit microns at 1–2 g accelerations, and hydraulic presses and press brakes demand clean, stable hydraulics and couplings able to absorb stamping shock loads. There is no room for consumer-grade components here — the bet is on brand-name servo drives, precision ball screws and dedicated couplings for press main drives.
Industry-typical tasks
- Main spindle drive of machining centers and CNC lathes — 7.5–90 kW servo motors with 1:10,000 control range
- X/Y/Z feed drives via ball screws — 0.4–7 kW servo motors with 23-bit encoder and ±5 µm positioning accuracy
- Drill-mill machines and general-purpose machining centers — 11–45 kW main drive, spindle assemblies with belt or direct drive
- Grinding and tool-grinding machines — high-speed 1.5–15 kW spindles with vibration damping and fine balancing
- Press shears (guillotine shears and hydraulic press brakes) — 75–500 kW drives with flywheel and friction clutch
- Hydraulic stamping and forming presses 75–1,500 tonf — 5.5–200 kW power packs with proportional valves
- CNC oxy-fuel and plasma sheet cutters — servo drives for gantries and carriages, dual Y-axis gantry synchronization
- Horizontal and vertical CNC machining centers — combined servo system + CNC controller + coolant feed PLC
Servo motors and electric motors
The key difference between metalworking drives and general-industry drives is closed-loop servo systems. The main spindle uses a servo motor with torque control and a wide regulation range (from 1 rpm on rough turning up to 12,000 rpm on finishing and grinding). Feed drives use servo motors with low rotor inertia, an absolute encoder and a holding brake that locks the axis on power loss. Key parameters: positioning accuracy (encoder counts), rotor inertia (J kg·m²), torque-loop bandwidth (≥ 2 kHz for modern series) and compatibility with EtherCAT/Mechatrolink/CANopen fieldbus through which the CNC controls the axes.
Servo drives for main spindles of machining centers and lathes
Servo motors with built-in encoder and forced cooling for the main spindle. Torque must hold across a wide speed range: at low speeds for heavy turning, at high speeds for finishing. Inovance MS1H and Wolong WGM water-cooled series deliver 7.5–90 kW at speeds up to 12,000 rpm and low-speed torque up to 600 N·m.
- — 7.5–90 kW power, 1:10,000 control range
- — 23-bit absolute encoder (8,388,608 pulses/rev)
- — Torque-loop bandwidth ≥ 2 kHz
- — Forced liquid or air cooling (IC416/IC81W)
- — Bearing protection against shaft currents (insulated non-drive-end bearing)
X/Y/Z feed servo drives via ball screw
Precision servo motors with low rotor inertia and built-in holding brake. They couple to the ball screw directly via a bellows coupling or through a 1:3–1:10 feed gearbox. Low rotor inertia matters for fast reversals during contour following, and a holding brake is mandatory on the vertical Z axis so the spindle does not drop on power loss. Inovance SV660 / WOLONG WPM cover 0.4–7 kW.
- — 0.4–7 kW power, 1.3–22 N·m torque
- — Low rotor inertia (J ≤ 5 × 10⁻⁴ kg·m²)
- — Built-in 24 V holding brake on the Z axis
- — 300 % overload for 3 s (for accelerations)
- — EtherCAT or Mechatrolink-III fieldbus to the CNC controller
Flywheel motors for press shears and crank presses
Mechanical shear-type presses use a 75–500 kW asynchronous motor to spin the flywheel up to working speed. Working-stroke energy comes not from the motor but from the flywheel's stored kinetic energy; in steady state the motor only tops up 10–20 % to recover speed. No VFD start is required here — a general-industrial motor with high starting torque or a soft starter is sufficient.
- — 75–500 kW power, 6 or 8 poles
- — Starting torque ≥ 1.8 × rated
- — Insulation class F, IP55
- — Compatibility with the press friction clutch (heavy extended shaft)
- — S6 duty capability (continuous with short-time load)
Motors for press power packs and coolant systems
Standard 5.5–200 kW asynchronous motors driving axial-piston and vane pumps in hydraulic power packs. S1 continuous duty, IP55, class F. Large hydraulic presses use several pumps on separate motors — this allows shutting down part of the pumps in low-flow cycles and saving energy. Variable-output presses use VFD start via Invt or Inovance drives.
- — 5.5–200 kW power, 4 or 6 poles
- — Insulation class F, IP55, S1 continuous duty
- — Pump compatibility via IEC B3/B5 flange
- — Inverter-duty option (NEMA MG1 Part 31) for VFD operation
- — Built-in PTC thermal protection
High-speed motors for grinding and tool-grinding machines
Grinding operations need spindles running at 6,000–15,000 rpm with fine rotor balancing (G1.0 or better). Dedicated servo motors or 1.5–15 kW high-frequency asynchronous motors (200–400 Hz) with G2.5 balancing are used. Bearings are ceramic or forced oil-lubricated. A specific requirement is low no-load vibration — otherwise vibration marks transfer to the ground surface.
- — 6,000–15,000 rpm speed
- — Rotor balancing per ISO 1940 G1.0–G2.5
- — Long-life bearings (ceramic or oil-mist)
- — No-load vibration ≤ 1.8 mm/s (zone A per ISO 10816)
- — High-frequency VFD compatibility
Gearboxes and gear motors
Gearboxes play a supporting role in metalworking: spindle main drives are increasingly direct (motor-spindle without a gearbox), but gear motors stay on feed drives of large gantries, buffers, tool magazines and material feed for shears. The critical parameters here are backlash (no more than 1–3 arc minutes for precision feeds), efficiency under high accelerations, low inertia referred to the output shaft, and flange compatibility with servo motors.
Low-backlash planetary feed gearboxes
Precision planetary gearboxes 1:3–1:100 with 1–3 arc-min backlash, used to couple servo motors to ball screws and rack-and-pinion drives of gantry machines. Low inertia and high torsional stiffness preserve the position-loop bandwidth of the servo drive. On large gantry plasma cutters they are used to synchronize the two Y axes.
- — 1:3 – 1:100 ratio
- — Backlash ≤ 3 arc-min (precision class)
- — Torsional stiffness ≥ 10 N·m/arc-min
- — Servo motor flange compatibility (DIN or proprietary chart)
- — Low referred inertia (J ≤ 1 × 10⁻⁴ kg·m²)
Gear motors for buffers, chip conveyors and coolant feed
Standard industrial helical-bevel (K-series) or in-line (R-series) gear motors for auxiliary drives: chip conveyors, workpiece chain conveyors, coolant feed, tool magazine buffers. Boneng K and HB series 0.55–11 kW cover the full set of typical tasks.
- — 0.55–11 kW power, 5–200 ratio
- — Service factor ≥ 1.5
- — IP55 protection (IP66 in coolant zone)
- — Compatibility with 24 V brake
- — Seal resistance to oil-based coolants
Rack-and-pinion gantry drives for plasma and oxy-fuel cutters
On gantry cutting machines (plasma, oxy-fuel, laser) gantry drives run through a rack and pinion. Precision planetary gearboxes with an output pinion are used, with low backlash and high efficiency. Rack length reaches 10–24 m, so the stiffness of the gearbox-to-carriage mount and rack alignment accuracy are critical.
- — Output pinion with module 2–4 mm
- — Installed backlash ≤ 0.05 mm along the arc
- — Spring-loaded mounting to eliminate clearance
- — 1:5–1:20 ratio
- — Adjustable center distance
Sheet feed gearboxes for guillotine shears and press brakes
Servo drives with 1:10–1:50 planetary gearboxes on the back-gauge stops. Stop positioning accuracy defines the cut-length accuracy of the sheet — typically ±0.05 mm over 4 m. Backlash here must not exceed 1 arc-min and reverse repeatability must be high.
- — Stop positioning accuracy ±0.05 mm
- — Backlash ≤ 1 arc-min (high-precision class)
- — Reverse repeatability ≤ 0.02 mm
- — 1:10–1:50 ratio
- — Low thermal deformation (operating up to 80 °C)
Couplings for main drives and spindles
On press equipment the coupling between the flywheel and the eccentric shaft transmits stamping shock loads of tens and hundreds of tonnes — it is the most heavily loaded coupling in the machine fleet. Yongjing drum gear couplings are used for rigid connection with misalignment compensation, and Longxuan flexible couplings are used for vibration damping on finishing machining centers and grinding spindles. Ball-screw feeds use zero-backlash bellows or disc-pack couplings — no backlash is acceptable here.
Gear couplings for press and shear main drives
Yongjing GIICL drum-type double-engagement gear couplings transmit torque from flywheel to press eccentric shaft under stamping shock loads. The crowned tooth profile compensates angular misalignment up to 1°30′ after thermal expansion of housings and foundation settling. Grease lubrication via a fitting, replaced every 6 months.
- — 50–800 kN·m torque
- — Angular compensation up to 1°30′
- — Compatibility with flywheel and eccentric flange
- — G6.3 balancing at peripheral speeds > 15 m/s
- — Service factor for stamping loads ≥ 2.0
Flexible pin couplings for spindle vibration damping
Longxuan LX/LMC flexible couplings with elastomer bushings reduce vibration amplitude of the main motor under interrupted cutting (milling with entry/exit) and compensate small shaft misalignment. They sit between the main spindle motor and the gearbox or belt-drive pulley. Elastomer service life is at least 30,000 hours.
- — 0.5–25 kN·m torque
- — Radial misalignment compensation up to 0.5 mm
- — Torsional damping capability 1–2°
- — Elastomer life ≥ 30,000 h
- — Bushing replacement without coupling removal
Bellows and disc-pack couplings for ball-screw feeds
Zero-backlash metal couplings between the servo motor and the ball screw. Bellows couplings suit long shafts with greater misalignment compensation; disc-pack couplings suit short shafts with high torques. Torsional stiffness must exceed 200 N·m/rad, otherwise position-loop bandwidth is lost and oscillations appear on finishing passes.
- — 5–500 N·m torque
- — Zero-backlash design
- — Torsional stiffness ≥ 200 N·m/rad
- — Axial misalignment compensation ±0.5 mm
- — G2.5 balancing for speeds up to 6,000 rpm
Press combined clutch-brake units
A combined clutch-brake unit on the press eccentric shaft — engages the flywheel with the shaft on the working stroke and clamps the shaft with the brake during idle. Actuation is pneumatic or hydraulic, engagement time 100–200 ms. Used on crank presses and press shears. Friction-lining wear is monitored via piston travel; once the limit is reached, the disc set must be replaced.
- — Engagement time ≤ 200 ms
- — 5–6 bar pneumatic control or hydraulics
- — Torque reserve 1.75–2.0 × press rated stroke
- — Lining wear monitored via limit switch
- — Press eccentric-shaft fit compatibility
Hydraulic components for presses and press brakes
Hydraulic presses and press brakes are above all a hydraulic system: pump → manifold → proportional valves → cylinders. Ram travel accuracy (typically ±0.01 mm on a 100 tonf press) and force stability depend on valve quality and oil cleanliness. On press brakes with two-cylinder synchronization (mechanical torsion bar or CNC via linear scales), valves must have high repeatability and low thermal drift.
Power packs for 75–1,500 tonf hydraulic presses
Complete Donly 5.5–200 kW power packs with variable-displacement axial-piston pumps, heat exchanger, fine filtration and proportional force-control valves. Hot-stamping presses add a water oil cooler and tank heating for winter start-up. Donly is SDS's signature competence in power packs, including build-to-print assembly to customer drawings.
- — 5.5–200 kW power, 16–32 MPa pressure
- — Variable-displacement axial-piston pump
- — 10 µm fine filter with clogging indicator
- — Air or water oil cooler
- — Tank with level gauge, thermometer and heating up to 35 °C
Proportional valves for press force control
Huade DBE/2FRE/4WRE proportional pressure and flow valves for CNC-programmed press force and ram speed control. Used on CNC press brakes and in two-cylinder synchronization systems on long press brakes. Pressure regulation accuracy ±1 % of rated, response time 30–80 ms.
- — Pressure up to 31.5 MPa, flow 30–500 l/min
- — Regulation accuracy ±1 % of rated
- — Response time 30–80 ms
- — Control signal 0–10 V or 4–20 mA
- — IP65 protection, oil temperature -20…+80 °C
Cylinders and valves for CNC machine guideways
Hydraulic cylinders for table clamping, rotary indexers and Z-axis counterbalance on large machining centers. Standard Ini unloading and pressure-reducing valves control clamp/unclamp. On large horizontal boring mills the spindle headstock weight is counterbalanced by hydraulic cylinders held at constant pressure.
- — 16–25 MPa pressure
- — Cylinders per ISO 6020/6022 or proprietary
- — Pressure-reducing valves with ±2 % accuracy
- — Seals for long cycle life (≥ 2 million cycles)
- — Compatibility with HLP 46 / HM 46 oil
CNC press brake systems with synchronization
Hydraulic press brakes with two cylinders require synchronized motion via two linear scales (right and left ram ends). Control through Huade proportional valves with feedback delivers ram parallelism of ±0.02 mm over 4 m, which is critical for bend quality on long sheets.
- — Ram parallelism ±0.02 mm over 4 m
- — Magnetostrictive linear scales, 0.01 mm
- — Proportional valves with < 50 ms response
- — Software control from CNC controller (DA-66T / Cybelec)
- — Two-channel emergency stop (category 4)
Hydraulic systems for plasma and oxy-fuel cutters
Large oxy-fuel and plasma cutters with elevating tables use compact 5.5–22 kW hydraulic systems for grate lift, sheet clamping and slag-bin extraction. Components include Ini manifolds and directional valves, filters with vacuum clogging indicator. Oil cleanliness is critical: class no worse than 18/16/13 per ISO 4406.
- — 5.5–22 kW power, 16 MPa pressure
- — Oil cleanliness 18/16/13 per ISO 4406
- — 4/3 directional valves with 24 V DC solenoid control
- — 10 µm return-line filters
- — Power-pack protection class IP54
Applications gallery
Our solutions for this industry
SDS portfolio brands that cover typical applications in this industry.
- INOVANCEfull SV660/MS1H servo drive line for spindles and feeds, CNC controllers and PLCs — one of China's leading positions in integrated machine-tool automation
- WOLONGbrushless WPM servo motors (0.4–7 kW feeds) and WGM (7.5–90 kW spindles) for main drives and feed axes of CNC machines
- INVTVFDs for press flywheel drives, servo drives for auxiliary axes, PLCs for material feed and coolant systems
- YONGJINGGIICL drum-type gear couplings for press and shear main drives, transmitting stamping shock loads up to 800 kN·m
- LONGXUANLX/LMC flexible pin couplings for vibration damping on finishing machining centers and grinding spindles, brake pulleys for auxiliary drives
- DONLYcomplete power packs for 75–1,500 tonf presses and press shears, 5.5–200 kW, build-to-print assembly to customer drawings — SDS's signature competence
- HUADEDBE/2FRE/4WRE proportional pressure and flow valves for CNC press brakes and variable-force hydraulic presses
- INIgeneral-purpose hydraulic components — valves, directional valves, filters for plasma and oxy-fuel cutter hydraulics, machining-center clamping and counterbalance circuits
- BONENGauxiliary K/HB/R gear motors for chip conveyors, workpiece buffers, tool magazines and coolant feed drives
- HUAWUelectrohydraulic thrusters and brake units for auxiliary hoisting mechanisms within metalworking process cells
Image credits: Psychlist1972 (CC BY 2.0) · Wikimedia Commons (CC BY 3.0) · Historic American Engineering Record (HAER) (Public domain) · Wikimedia Commons (Public domain) · Graibeard (CC BY-SA 3.0)