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INOMAX ACS580 & ACS880 Bending Machine Solutions

High-Performance Variable Frequency Drives for Press Brakes, Panel Benders and Metal Forming Equipment

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Overview

Sheet metal bending is one of the most fundamental operations in metal fabrication. From automotive body panels and chassis components to HVAC ductwork, electrical enclosures, and structural steel, press brakes produce the precise angles and bends that shape the modern world. Yet traditional hydraulic press brakes are notoriously inefficient — the hydraulic pump runs continuously at full speed regardless of whether the machine is actively bending, waiting for the operator, or idle between cycles. This constant operation wastes enormous amounts of energy, generates excessive noise, and accelerates pump wear.

At Inomax Technology, our ACS580 (general purpose) and ACS880 (high-performance) variable frequency drives are engineered specifically for the demanding requirements of bending machine applications. With Direct Torque Control (DTC) technology delivering full torque at zero speed and sub‑5 ms torque response, built‑in PID control for precise pressure regulation, regenerative braking options for energy recovery, and high overload capacity for demanding bending cycles, our drives deliver the precision, reliability and energy savings that modern metal fabrication shops demand.

Why INOMAX for bending machines?

Which INOMAX drive is right for your bending machine application?

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The Bending Machine Challenge: Energy Efficiency & Precision

Energy Waste in Traditional Hydraulic Press Brakes

A conventional hydraulic press brake uses a fixed-speed electric motor driving a hydraulic pump. The pump runs continuously at full speed as long as the machine is powered on — regardless of whether the ram is moving, bending, or idle. Studies have shown that using VFDs can lead to energy savings of up to 30% in press brake operations. Hybrid hydraulic drives that power the hydraulic pump at just the right speed and torque to match changing load demands use about half the energy of a conventional system while performing equivalent work

The waste happens in three ways:

• Idle time — While the operator loads and positions the workpiece, the pump runs at full speed, circulating oil through a relief valve — consuming energy but doing no useful work

• Light bending — During bends requiring less than full pressure, the pump still runs at full speed, with excess flow bypassed through the relief valve

• Rapid descent — The pump continues running at full speed even though gravity is lowering the ram

How VFDs solve these problems:

With a VFD controlling the pump motor, the drive adjusts motor speed to match the actual demand of each phase of the bending cycle:

• Rapid descent — Pump runs at low speed (only enough to open pilot valves); gravity does most of the work

• Bending — Pump accelerates to full speed only during the actual bend stroke when pressure is required

• Return stroke — Pump speed reduced; gravity and cylinder area differences assist the return

• Idle / loading — Pump runs at minimal speed or stops (if sleep mode is enabled)

Variable frequency drives control the speed of the electric motor in the press brake, adjusting the motor speed according to the actual load. When the press brake is idle or only doing light bending work, the VFD reduces the motor speed, consuming less energy

Precision Control for Consistent Bend Angles

Bending accuracy depends on precise control of ram position and hydraulic pressure. Traditional fixed-speed systems rely on proportional valves to meter oil flow — a wasteful and inherently less precise method. VFDs with closed-loop control offer superior accuracy:

• Speed accuracy ±0.5% (ACS580 open loop) to ±0.01% (ACS880 closed loop) — Consistent ram speed for repeatable bend angles

• Built-in PID control — Maintains precise hydraulic pressure regardless of load variations

• Direct Torque Control — Instantaneous torque response for smooth, jerk-free ram motion

Noise Reduction — A Critical Workplace Benefit

A typical hydraulic press brake with a fixed-speed pump produces continuous noise — often exceeding 85 dB(A). With VFD control, the pump runs at lower speeds during most of the cycle, dramatically reducing noise pollution. A study by Green Hydraulic Power found that VFD hydraulic systems typically use up to 80% less energy and dramatically reduce noise pollution, leading to a safer and more productive workplace–.

Extended Equipment Life

Soft starting eliminates the electrical and mechanical shock of across-the-line motor starting. Reduced pump operating hours directly extend pump life. Lower operating temperatures reduce seal degradation and fluid oxidation. Reduced pressure ripple minimizes stress on valves, hoses and cylinders.

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Key Technologies for Bending Machine Applications

Variable Speed Pump Control — The Core Energy Saver

The primary function of a VFD in a hydraulic press brake is to control the speed of the pump motor. Instead of the pump running at full speed continuously, the drive ramps motor speed up and down based on real-time demand.

How it works:

• Pressure feedback — A pressure transducer (4-20mA or 0-10V) provides real-time feedback to the VFD

• PID control — The drive compares actual pressure to setpoint and adjusts motor speed to maintain target pressure

• Demand-based speed — During low-demand phases (rapid descent, idle), motor speed drops significantly — often to 20-30% of rated speed

• Energy savings — Power consumption follows the affinity law: reducing speed by 50% reduces power consumption by approximately 87.5%

Direct Torque Control (DTC) — ACS880 for High-Performance Applications

ACS880 DTC technology updates the motor model 40,000 times per second, delivering instantaneous torque response and full torque at zero speed without an encoder for most applications.

Why DTC matters for bending machines:

• Full torque at zero speed — Instantaneous pressure buildup when the bend starts; no waiting for the pump to spin up

• Torque response <5 ms — Immediate response to pressure setpoint changes

• Speed accuracy ±0.01% with encoder — Precise control for synchronized dual-cylinder press brakes

• No encoder needed for most applications — Higher reliability in dusty fabrication environments

Built-in PID Control for Hydraulic Pressure Regulation

Both ACS580 and ACS880 include powerful built-in PID controllers specifically configured for pressure and flow control applications.

Key PID features for press brakes:

• Pressure setpoint via analog input — Direct connection to CNC controller (0-10V or 4-20mA)

• Pressure feedback via pressure transducer — Real-time feedback from cylinder or manifold

• Auto-tuning — Drive automatically calculates optimal P, I, D gains

• Sleep/wake-up mode — Stops pump during extended idle periods; restarts automatically when bending resumes

• Two independent PID sets — Switch between rapid traverse and bending pressure profiles

Regenerative AFE (Active Front End) — Energy Recovery

During rapid ram descent, the pump motor may be driven by the descending weight of the ram and tooling — effectively operating as a generator. Traditional systems waste this energy as heat in braking resistors. The ACS880 AFE (Active Front End) option captures this regenerated energy and returns >95% to the grid.

Key AFE benefits for press brakes:

• THDi <5% at 80-100% load — Eliminates harmonic interference with CNC controls and sensors

• Unity power factor (>0.99) — Reduces utility penalties

• Regenerative energy recovery — Return braking energy to the grid during rapid descent

• Constant DC bus voltage — Immune to grid fluctuations common in industrial environments

Master-Slave Torque Control for Dual-Cylinder Synchronization

Large press brakes often have two hydraulic cylinders (Y1 and Y2) that must move in perfect synchronization to prevent racking and ensure parallel ram movement. Our master-slave torque control ensures perfect synchronization:

• Master drive operates in speed control (usually Y1 cylinder)

• Slave drive operates in torque control, receiving torque reference from master

• Result — Both cylinders produce identical force; ram remains perfectly parallel

• Redundant master capability — If master drive fails, slave can automatically assume master role

Position Control for Back Gauges and Crowning

Modern CNC press brakes require precise positioning of back gauge axes (X, R, Z) and crowning systems. Both ACS580 and ACS880 support position control with encoder feedback:

• Positioning accuracy ±1 encoder count — Sub-millimeter accuracy for flange positioning

• Electronic gearing — Multiple axes can follow master position with programmable gear ratios

• Absolute encoder support (ACS880) — Eliminates homing on power-up

• Pulse train input — Direct interface with CNC controllers for step-and-direction positioning

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Product Series Overview

Selection guide:

• Choose ACS580 for standard hydraulic press brake pump drives, back gauge axes, and auxiliary pumps where cost-effectiveness is the primary driver

• Choose ACS880 for large press brakes, high-duty-cycle applications, dual-cylinder synchronization, and applications requiring the highest dynamic performance or regenerative energy recovery

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Technical Specifications for Bending Machine Applications

ACS580 Series — Pump Drive for Standard Press Brakes

ACS880 Series — High-Performance for Large Press Brakes

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Application Case Studies

Case Study 1: Hydraulic Press Brake Retrofit — Energy Savings with ACS580

Customer: Confidential — metal fabrication shop, North America
Machine: 150-ton hydraulic press brake, 30 kW pump motor
Old system: Fixed-speed pump running continuously; energy costs $12,000/year; noisy operation

Challenge: The shop operates two shifts, but the press brake is only actively bending for approximately 40% of the time. The rest of the time, the pump runs idle while operators load parts, check angles, or change tooling. The shop wanted to reduce energy costs and noise levels.

Solution: Inomax supplied an ACS580-4030 (30 kW) drive configured for pump control. Pressure feedback from a 4-20mA pressure transducer. Enabled PID pressure control and sleep/wake-up mode. Set sleep frequency to 10 Hz — pump stops after 10 seconds of idle operation. Wake-up on pressure drop below 5% of setpoint.

Results:

• Energy consumption reduced by 38% — annual savings of $4,560

• Pump operating hours reduced by 60% — extended pump life

• Noise level reduced by 12 dB(A) — significantly quieter work environment

• Hydraulic oil temperature reduced by 15°C — less fluid degradation

• Payback period: 8 months

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Case Study 2: Large CNC Press Brake — Dual-Cylinder Synchronization with ACS880

Customer: Confidential — heavy fabrication shop, Europe
Machine: 500-ton CNC press brake, dual hydraulic cylinders, 110 kW pump motor
Challenge: The press brake experienced ram skewing during heavy bending (20 mm thick plate), causing inconsistent bend angles and excessive wear on cylinder seals and guides.

Solution: Inomax supplied two ACS880-01-180A-5 (110 kW) drives in master-slave torque control. Master drive controls Y1 cylinder (speed control). Slave drive controls Y2 cylinder (torque control, receiving torque reference from master). Installed incremental encoders on both cylinders for position feedback. Enabled electronic line shaft for perfect synchronization.

Results:

• Ram parallelism maintained within ±0.05 mm across full width — no skewing

• Bend angle consistency improved by 80% — scrap rate reduced from 5% to 1.5%

• Cylinder seal life extended (reduced side loading)

• Master-slave torque balance within ±3%

• Payback period: 14 months

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Case Study 3: High-Cycle Panel Bender — Rapid Acceleration with ACS580

Customer: Confidential — HVAC ductwork manufacturer, Asia
Machine: High-speed panel bender for light-gauge sheet metal, 15 kW pump motor
Old system: Fixed-speed pump; cycle rate limited by pump acceleration time

Challenge: The panel bender operates at high cycle rates (up to 30 bends per minute). The fixed-speed pump wasted energy during idle periods and limited maximum cycle rate due to slow pressure buildup.

Solution: Inomax supplied an ACS580-4015 (15 kW) drive with pressure PID control. Enabled energy optimizer mode. Programmed rapid acceleration (0.5 seconds to full speed). Set PID for fast response (proportional gain 2.5, integral time 0.3 seconds).

Results:

• Cycle rate increased from 22 to 30 bends per minute — 36% productivity gain

• Energy consumption reduced by 32%

• Pump starts reduced (soft start eliminated inrush)

• Annual energy savings: $3,200

• Payback period: 6 months

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Case Study 4: Regenerative Press Brake — Energy Recovery with ACS880 AFE

Customer: Confidential — automotive parts supplier, Europe
Machine: 300-ton CNC press brake for chassis components, high cycle rate, frequent rapid ram descent

Challenge: The press brake operates at high cycle rates with frequent rapid ram descent (gravity assisting the downward stroke). The pump motor regenerates significant energy during descent. Traditional system wasted this energy as heat in braking resistors, requiring large resistors and cooling fans.

Solution: Inomax supplied an ACS880 AFE regenerative drive. AFE front end returns >95% of braking energy to the grid during ram descent. Unity power factor and THDi <5% eliminated utility penalties.

Results:

• Energy recovered: 45,000 kWh/year — annual savings of $5,400

• Braking resistors eliminated — no heat load in electrical enclosure

• Power factor improved from 0.82 to 0.99 — utility penalties eliminated

• THDi reduced from 38% to 4.2% — harmonic compliance achieved

• Payback period: 16 months

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Case Study 5: Back Gauge Positioning — Multi-Axis Control with ACS580

Customer: Confidential — sheet metal fabricator, North America
Machine: CNC press brake with 4-axis back gauge (X1, X2, R, Z)
Old system: Stepper motors with open-loop control; lost steps caused positioning errors

Challenge: The existing stepper motor system frequently lost position, causing incorrect flange lengths and scrap parts. The shop needed a reliable, closed-loop positioning solution.

Solution: Inomax supplied four ACS580 drives with incremental encoder feedback configured for position control. X1 and X2 axes — independent positioning for taper correction. R-axis — vertical positioning to clear flanges during feeding. Z-axis — finger positioning across the beam. Integrated with existing Delem CNC controller via Modbus TCP.

Results:

• Positioning accuracy improved to ±0.1 mm — consistent flange lengths

• Scrap rate from positioning errors eliminated

• Lost steps eliminated (closed-loop control)

• Production speed increased by 15% (faster positioning)

• Payback period: 9 months

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Case Study 6: Servo-Electric Press Brake — Hybrid Drive with ACS880

Customer: Confidential — machine tool builder, Asia
Machine: New design hybrid press brake — servo motor driving hydraulic pump (on-demand hydraulic system)
Challenge: The machine required a drive capable of rapid acceleration, precise speed control across a wide range (0-100% pump speed), and seamless integration with a proprietary CNC controller.

Solution: Inomax supplied ACS880 drives with encoder feedback for closed-loop speed control. Profinet IRT communication for deterministic control (<1 ms cycle time). Energy optimizer enabled. Built-in PLC eliminated need for external controller for pump logic.

Results:

• Pump speed control accuracy ±0.5% across full range

• Energy consumption 55% lower than equivalent fixed-speed hydraulic press brake

• Machine noise level 15 dB(A) lower than conventional design

• Machine builder standardized on ACS880 for entire product line

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Comparison with Competitors

Why INOMAX wins for bending machines:

• ACS580 offers exceptional value for standard press brake pump control — same core technology as premium brands at significantly lower cost

• ACS880 provides identical DTC performance to ABB at 20-30% lower cost

• Conformal coating standard — competitors often charge extra for this essential protection

• Master-slave torque control for up to 60 drives — perfect for large dual-cylinder press brakes

• Proven import substitution — successfully replaced ABB ACS800 and Siemens drives in multiple applications

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Frequently Asked Questions

Q1: What size VFD do I need for my hydraulic press brake?

Size the VFD based on the motor’s full load current (FLA) — not horsepower alone. For standard hydraulic press brake applications, we recommend selecting a drive with a continuous current rating equal to or greater than the motor FLA. For heavy-duty applications with frequent high-pressure bending, consider adding 15-20% margin. For a 30 kW motor (approximately 60 A at 400V), we recommend an ACS580-4030 (30 kW) or ACS880-01-061A-5 (30 kW). Contact our engineering team for a precise sizing recommendation based on your motor nameplate and duty cycle.

Q2: How much energy can I save by adding a VFD to my press brake?

Energy savings depend on your duty cycle and operating patterns. Based on our case studies and industry research:

• High-cycle press brakes (automotive, high-volume fabrication) — 30-40% energy savings

• General fabrication shops (mixed production) — 25-35% energy savings

• Job shops (low volume, long idle periods) — 35-50% energy savings

A typical 150-ton press brake operating 2 shifts (4,000 hours/year) with energy costs of $0.12/kWh can save $4,000-$6,000 annually. Studies have shown that using VFDs can lead to energy savings of up to 30% in press brake operations. The hydraulic system is said to use about half the energy of a conventional system while performing equivalent work

Q3: Can I retrofit an existing fixed-speed press brake with a VFD?

Yes — and this is one of the most cost-effective energy efficiency upgrades available for metal fabrication shops. The retrofit typically includes:

• Installing the VFD between the main disconnect and the pump motor

• Adding a pressure transducer (if not already present) for closed-loop pressure control

• Configuring the drive for pump control (PID pressure regulation, sleep/wake-up)

• Minor modifications to the control circuit (start/stop signals from the press brake CNC)

Most retrofits can be completed in one day. Payback is typically 6-18 months depending on operating hours.

Q4: Does the ACS580 support position control for back gauge axes?

Yes. The ACS580 supports position control with incremental encoder feedback. Positioning accuracy is ±1 encoder count. For absolute encoder support (EnDat, Hiperface) or higher precision applications, we recommend the ACS880. For multi-axis back gauge systems (X1, X2, R, Z), we can supply multiple ACS580 drives with electronic gearing for coordinated motion.

Q5: How does master-slave torque control improve dual-cylinder press brake performance?

In a dual-cylinder press brake, perfect synchronization is essential to prevent ram skewing (one side leading the other). Without proper synchronization, the ram twists, causing inconsistent bend angles, accelerated wear on cylinder seals and guides, and potential tooling damage. Master-slave torque control ensures both cylinders produce identical force — the master drive controls speed, and the slave drive follows the master’s torque reference. This eliminates skewing and ensures the ram remains perfectly parallel to the bed throughout the stroke.

Q6: What is the advantage of regenerative AFE for press brakes?

During rapid ram descent, gravity assists the downward motion. The pump motor may be driven by the descending weight — effectively operating as a generator. Traditional systems waste this energy as heat in braking resistors (up to 10 kW of heat that must be removed from the electrical enclosure). ACS880 AFE captures this energy and returns >95% to the grid, reducing energy consumption, eliminating braking resistors (and their associated heat load), and improving power factor. For high-cycle press brakes with frequent rapid descents, AFE can reduce overall energy consumption by an additional 10-15%.

Q7: What communication protocols are supported for integration with press brake CNC controllers?

We support Modbus RTU/TCP (standard), Profibus DP, Profinet IRT, EtherCAT, EtherNet/IP, and CANopen. For press brakes with Delem, Cybelec, ESA or other CNC controllers, we provide complete GSDML, ESI, and EDS files for seamless integration. We also support analog control (0-10V pressure setpoint, 4-20mA pressure feedback) and discrete I/O (start/stop, run/fault) for simpler control systems.

Q8: How does the VFD protect the hydraulic pump and system?

Our drives provide multiple protection features:

• Soft starting — Eliminates the electrical and mechanical shock of across-the-line motor starting

• Pressure limiting — Programmable maximum pressure prevents over-pressurization

• Torque limiting — Prevents pump damage from excessive load

• Underload detection — Detects pump cavitation or loss of prime

• Overload protection — Protects motor and pump from extended over-current conditions

These features significantly extend pump and hydraulic component life.

Q9: What maintenance does a VFD require in a metal fabrication environment?

Metal fabrication shops can be dusty environments with conductive metal particles. We recommend:

• Monthly — Visual inspection, check cooling fan operation, monitor heatsink temperature (should be <80°C)

• Quarterly — Clean air filters (IP54 units) using a vacuum; inspect for metal dust accumulation

• Every 6 months — Tighten power terminals (thermal cycling loosens connections)

• Annually — Replace cooling fans (expected life 40,000 hours; in dusty environments, reduce to 25,000 hours)

Conformal coating on all INOMAX drives provides essential protection against conductive dust and humidity in metal fabrication environments.

Q10: Can I use a single VFD to control multiple press brake functions?

A single VFD can control the main pump motor. Back gauge axes require separate drives (or servo drives). For machines with auxiliary pumps (cooling, pilot pressure), additional small VFDs may be required. Our engineering team can help you design a complete drive solution for your specific press brake configuration.

Q11: What is the typical payback period for retrofitting a press brake with INOMAX VFD?

Based on our case studies and industry research, typical payback periods range from 6 to 18 months:

• High-cycle press brakes — 6-12 months (energy savings + productivity gains)

• General fabrication — 9-15 months (energy savings primarily)

• Job shops with long idle periods — 12-18 months (energy savings from idle reduction)

• New machine integration — Included in machine cost; ROI achieved through lower operating costs

Q12: Does INOMAX offer IP55 drives for harsh fabrication environments?

Yes. The ACS580 is available in IP55 (NEMA 12) enclosures with rugged metal housing, suitable for fabrication shop environments with metal dust and humidity. The IP55 version includes sealed cable entries, conformal-coated circuit boards, and a ventilation system that protects against non-conductive dust and splash damage. For the most demanding environments, we offer IP66 enclosures.

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Why Choose Inomax Technology for Bending Machines?

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Ready to Upgrade Your Press Brake?

Whether you are retrofitting an existing hydraulic press brake, designing a new bending machine, or simply looking for a cost-effective alternative to premium European brands, our bending machine application engineers are ready to help you select, size, and commission the right VFD solution.

Contact us today for:

• Free press brake energy savings assessment

• VFD sizing recommendation based on your motor and duty cycle

• Retrofit proposal for replacing existing drives

• Pressure PID tuning support

• Back gauge position control configuration