Stable forming accuracy in a servo CNC stretch bending machine is not created by one cylinder, one motor, or one control program. It comes from the coordinated operation of the drive system, hydraulic circuit, feedback devices, filtration equipment, lubrication system, and temperature-control unit.

During stretch bending, a profile is clamped, tensioned, and formed around a die along a controlled path. Any fluctuation in motion feedback, oil cleanliness, pressure delivery, lubrication, or hydraulic-fluid temperature can affect machine response and long-term consistency. Understanding the main internal components therefore helps buyers evaluate not only the machine specification, but also its reliability, maintenance requirements, and suitability for a particular production task.

How the Main Components Support the Bending Process

1. Servo Motor and Hydraulic Pump: Controlled Power for Forming

The servo-hydraulic drive is responsible for supplying the controlled power needed to stretch and form the profile. The permanent-magnet AC servo motor drives the hydraulic pump, converting electrical energy into regulated hydraulic flow and pressure.

Compared with a conventional continuously running drive, a servo-controlled system can adjust its output according to the operating command. This supports responsive control and may reduce unnecessary energy consumption during stages of the operating cycle with lower hydraulic demand.

The complete power unit integrates servo motors, pump assemblies, filters, pressure gauges, valve blocks, ball valves, hydraulic lines, sensors, and electrical connections. These elements must be selected, assembled, and commissioned as one coordinated system.

A high-capacity motor alone does not determine forming performance. Pump displacement, required pressure, flow demand, control strategy, cylinder size, and actuator arrangement must also match the workpiece and production cycle.

In the photographed machine configuration, the three-phase permanent-magnet AC servo motor has a nameplate rating of 46.5 kW, 222 N·m rated torque, 2,000 rpm rated speed, 380 V rated voltage, IP54 protection, and 94.5% efficiency.

These values describe this particular machine configuration rather than a universal specification for every Camille stretch bending machine. Motor and pump selection should be engineered according to the profile material, cross-section, bending radius, required tensile force, workpiece length, and target production rate.

2. Rotary Encoder: Feedback for Closed-Loop Motion Control

A rotary encoder converts shaft rotation into electrical feedback signals. In a servo CNC stretch bending machine, this feedback allows the controller to monitor actual rotational movement and compare it with the programmed command.

The photographed encoder includes A, B, and Z signal channels, which are commonly used to provide incremental position, rotational direction, speed, and reference feedback.

Reliable feedback is important because the machine must coordinate multiple actions rather than complete a single uncontrolled push. Stretching, feeding, bending-arm movement, and forming travel must occur in the correct sequence.

The rotary encoder is one part of the control loop that helps the CNC system identify deviations between commanded and actual movement. Final forming accuracy, however, still depends on the complete machine structure, tooling, calibration, material behavior, and bending program.

3. Integrated Oil-Level and Temperature Sensor

The hydraulic reservoir must contain enough oil for stable circulation, while the fluid temperature must remain within the intended operating range. An integrated oil-level and temperature sensor allows both conditions to be monitored through one device.

In the photographed system, the display shows an oil-level reading of approximately 415 mm and an oil temperature of approximately 27.2°C. These values give the operator a direct view of the current reservoir conditions.

A low oil level may introduce aeration, unstable pump supply, or insufficient cooling capacity. Excessive oil temperature can reduce viscosity, accelerate seal aging, and change hydraulic response.

Monitoring these values does not replace preventive maintenance, but it makes abnormal operating conditions easier to identify before they develop into larger hydraulic-system problems.

4. Hydraulic Oil Filter and CS-V Clogging Indicator

Hydraulic oil carries power through narrow valve passages, pump interfaces, cylinders, seals, and other precision components. Particles introduced during assembly, maintenance, or normal mechanical wear can damage these components and interfere with valve operation.

The hydraulic oil filter removes contamination from the circulating fluid and is therefore an important protective element within the hydraulic system.

The filter element gradually accumulates contamination during operation. As the element becomes restricted, the pressure difference between the filter inlet and outlet increases.

A differential-pressure device is therefore used to monitor the condition of the filter element. The CS-V differential-pressure clogging indicator monitors this pressure drop and provides a switch or alarm signal when the preset condition is reached.

The photographed CS-V unit is marked for a working pressure of 32 MPa and a differential-pressure trigger point of 0.35 MPa. Its body also indicates the required installation direction from P1 to P2.

Correct installation and a timely response to the clogging signal are important. Replacing a filter element too late may increase the risk of restricted flow, bypass operation, or contamination entering sensitive hydraulic components. At the same time, abnormal contamination should be investigated rather than treated only as a routine filter replacement issue.

5. High- and Low-Pressure Ball Valves for Circuit Isolation

Ball valves provide a direct mechanical method for opening or isolating hydraulic lines. They are used during system operation, commissioning, inspection, and maintenance, but the valve specification must match the pressure level of the circuit in which it is installed.

The high-pressure valve in the photographed assembly is marked KHB-G1 1/4, DN32, and 31.5 MPa. It is intended for pressurized sections where component strength, sealing performance, and pressure resistance are critical.

The lower-pressure valve is marked Q11F-16C, DN32, and G1 1/4. It can be used in circuit positions with lower pressure requirements, such as certain return, cooling, or auxiliary lines.

These two valve types should not be treated as interchangeable simply because their connection sizes are similar. Pressure rating, material, sealing method, connection type, and intended circuit position must all match the hydraulic design.

During maintenance, isolation valves help technicians separate a defined section of the system. However, shutting a valve does not automatically mean that the isolated line is safe. Residual pressure must still be released according to the machine’s operating and maintenance procedures.

6. Automatic Centralized Lubrication Pump

The automatic centralized lubrication pump is separate from the machine’s main hydraulic pump. Its purpose is not to generate the hydraulic pressure used for stretching or bending.

Instead, the lubrication pump supplies grease to designated mechanical lubrication points, helping reduce friction at guideways, bearings, sliding surfaces, and other moving interfaces included in the machine design.

Centralized delivery can provide more consistent lubrication than relying entirely on separate manual greasing operations. It also makes routine maintenance easier to organize because multiple lubrication points can be supplied from one controlled system.

However, an automatic lubrication system does not eliminate inspection. The reservoir must contain the correct lubricant, the delivery lines must remain clear, and operators should confirm that each lubrication point receives the intended amount of grease.

7. Industrial Fluid Chiller: Managing Hydraulic Oil Temperature

Hydraulic-fluid temperature changes during continuous machine operation as pumps, valves, throttling points, and mechanical loads generate heat. If the oil becomes too hot, its viscosity can fall, internal leakage may increase, and seals may age more quickly.

If the oil is too cold, viscosity can become too high and slow the response of the hydraulic system. Temperature stability is therefore important for machines that are expected to maintain consistent operating behavior during extended production periods.

An industrial fluid chiller helps maintain the hydraulic oil closer to the configured temperature range. This supports more stable oil viscosity and more consistent hydraulic response over a longer operating cycle.

The photographed chiller display shows a current value of approximately 29.8°C and a set value of approximately 32.0°C. These readings are an operating snapshot rather than a recommended setting for every stretch bending application.

The appropriate temperature setting depends on the selected hydraulic oil, ambient temperature, system design, production duty cycle, and commissioning parameters of the equipment.

How the Components Work Together

During a programmed bending cycle, the CNC controller sends motion commands to the servo drive. The servo motor and hydraulic pump provide the required flow and pressure, while the rotary encoder and other sensors return operating feedback to the control system.

Clean oil passes through the filtration system, and the CS-V indicator warns when the pressure difference across the filter reaches its trigger level. High- and low-pressure ball valves provide circuit isolation in their respective positions, while the centralized lubrication pump supplies grease to designated mechanical movement points.

During extended operation, the industrial fluid chiller helps manage hydraulic-oil temperature. The oil-level and temperature sensor gives the operator additional information about the condition of the reservoir.

This coordinated architecture supports stable and repeatable machine response. However, component quality is only one part of a successful stretch-bending solution. The machine frame, clamping method, tooling geometry, compensation strategy, profile material, operator setup, and CNC program must all be considered together.

What Buyers Should Confirm Before Selecting a Machine

A list of high-quality components should never be evaluated separately from the actual forming task. Before configuring a servo CNC stretch bending machine, buyers should provide the following information:

• Profile drawings with complete cross-section dimensions and tolerances
• Material grade, temper, and heat-treatment condition
• Target bending radius, arc length, and finished geometry
• Maximum workpiece length and required tensile force
• Expected production volume and operating cycle
• Surface-quality requirements and acceptable deformation limits
• Required forming accuracy and repeatability
• Factory power supply and installation conditions
• Available workshop space and material-handling requirements

With this information, the drive power, hydraulic flow, sensor arrangement, tooling, cooling capacity, lubrication system, and maintenance configuration can be matched more closely to the application instead of being selected from a generic equipment checklist.

Discuss Your Stretch-Bending Application with Camille

Camille develops metal-profile and plate-bending equipment for application-specific forming requirements. If you are evaluating a CNC stretch bending machine, send us your PDF or DWG drawings together with the material, bending radius, tolerance, workpiece length, and production requirements.

Our team can review the project requirements and recommend a suitable machine, hydraulic system, tooling, and control configuration.

Learn more: CNC Stretch Bending Machines

Contact Camille: Submit Your Project Requirements

Note: The brands, models, ratings, and displayed operating values shown in this article are examples from the photographed machine configuration. Final component selection may vary according to the technical requirements of each project.