Servo-Hydraulic Injection Molding Machine with VG Internal Gear Pump: How 40 MPa Pressure and Ultra-Low Noise Improve Cycle Repeatability

In modern injection molding facilities, the hydraulic pump is the heart of every servo-hydraulic machine. The choice of pump technology directly influences cycle repeatability, energy consumption, noise levels on the production floor, and the long-term reliability of the entire hydraulic system. Among the available pump architectures, Internal Gear Pumps have gained significant traction because of their inherent advantages in pulsation control, volumetric efficiency, and quiet operation. TheVicksServo VG internal gear pumprepresents the current state of the art, combining pressures up to 40 MPa with ultra-low noise output and a displacement range that covers small to large tonnage Injection Molding Machines. This blog explores the engineering principles behind the VG series, explains how its design translates into measurable improvements in cycle repeatability, and provides practical guidance for system integrators and plant engineers evaluating servo-hydraulic pump solutions for their production lines.

Why Internal Gear Pump Architecture Matters for Servo-Hydraulic Systems

Servo-hydraulic Injection Molding Machines differ fundamentally from traditional fixed-speed hydraulic machines in how they control pressure and flow. Instead of running a motor at constant speed and throttling flow through proportional valves, a servo-hydraulic system varies the speed of the electric servo motor driving the hydraulic pump. The pump must therefore deliver stable, predictable flow across a wide speed range, from near-zero RPM during holding and cooling phases to full speed during injection and clamp closing. This operating profile places unique demands on the pump that not all hydraulic pump types can satisfy equally well, making the selection of the right pump architecture a critical engineering decision.

Internal gear pumps consist of an outer ring gear and a smaller inner gear mounted on a shared axis with a crescent-shaped separator. As the gears rotate, expanding and contracting chambers on the inlet and outlet sides create a smooth, continuous flow path. Because multiple tooth pairs are in contact at any given moment, the flow delivered to the system has inherently lower pulsation compared to external gear pumps, where only one or two teeth carry the load at a time. For servo-hydraulic machines, lower pulsation means the servo drive controller experiences fewer hydraulic disturbances, enabling tighter pressure and velocity regulation throughout the molding cycle. This tighter regulation directly translates into improved shot-to-shot consistency and higher part quality.

The VG internal gear pump series from Vicks Servo is specifically engineered for this operating mode. With models in the VGH0 Series rated up to 40 MPa and capable of speeds up to 4,200 RPM, the VG range covers the full performance envelope required by modern servo-hydraulic injection molding machines. Whether the application demands a single pump for a straightforward circuit, a double pump configuration for independent injection and clamping circuits, or a combined pump for multi-function flow delivery, the VG series provides the mechanical foundation for precise hydraulic control that machine builders and end users can rely on for consistent production results.

40 MPa Pressure Capability and Its Impact on Molding Performance

Pressure capability is one of the most critical specifications for any hydraulic pump used in injection molding. The injection phase requires high pressure to force molten polymer through the nozzle, sprue, runner, and gate into the mold cavity. For engineering resins with high viscosity, thin-wall parts, or long flow path lengths, the required injection pressure can approach or exceed 25 MPa at the hydraulic cylinder. Adding system losses from piping, fittings, and valve manifold pressure drops means the pump must deliver well above that threshold to ensure the machine can reach the required nozzle pressure at all times without being limited by hydraulic capacity.

The VGH0 Series VG internal gear pump addresses this requirement with a continuous working pressure rating of up to 40 MPa. This generous pressure margin ensures that the servo-hydraulic machine can maintain the programmed injection profile even under worst-case conditions such as cold mold startup, high-viscosity materials, or thick-section parts requiring extended packing. The robust gear set design and precision-machined housing of the VG pump ensure volumetric efficiency remains high at elevated pressures, which translates into less heat generated in the hydraulic fluid, lower cooling requirements, and reduced energy waste during extended production runs.

From a machine builder perspective, the 40 MPa rating of the VG pump also simplifies system design. Engineers can specify a single pump model that covers the pressure requirements of both injection and clamping circuits without the need for oversized or multi-stage solutions. This reduces the hydraulic component count, simplifies manifold design, and lowers the overall bill of materials. For end users operating servo-hydraulic machines on demanding applications such as automotive connectors, medical device housings, and multi-cavity precision molds, the pressure headroom of the VG series provides assurance that the hydraulic system will not be the limiting factor in achieving cycle time targets or part quality specifications on the shop floor.

Ultra-Low Noise Engineering: Design Principles Behind Quiet Operation

Noise reduction in hydraulic systems is not merely a comfort consideration for machine operators. Excessive hydraulic noise is a direct indicator of pressure pulsation, vibration, and flow instability that degrade system performance and accelerate component wear. In injection molding environments where multiple machines operate in close proximity, cumulative noise levels can exceed occupational health limits and create an unpleasant working atmosphere. Reducing noise at the source by selecting a pump with inherently low pulsation is far more effective and cost-efficient than attempting to attenuate noise through enclosures, mounts, or acoustic barriers after the fact.

The VG internal gear pump achieves ultra-low noise through several interrelated design features. The internal gear geometry ensures that the transition of fluid volumes from the inlet to the outlet side of the pump is gradual rather than abrupt. Because the crescent separator divides the gear mesh into multiple simultaneous chambers, the pressure build-up and release at the outlet port occurs in small, overlapping increments. This design inherently reduces the pressure ripple that is the primary source of tonal noise in hydraulic pumps. Additionally, the VG series features optimized port geometry that minimizes flow restriction and turbulence at the inlet and outlet, further reducing broadband noise contributions from fluid velocity effects throughout the operating range.

Manufacturing precision also plays a decisive role. The internal gear set of the VG pump is machined to tight dimensional tolerances that ensure consistent tooth-to-tooth contact and minimal clearance variation. This precision prevents the localized high-pressure zones and cavitation events that cause impulsive noise in lower-quality pumps. The result is a pump that operates at noise levels significantly below those of conventional external gear pumps of equivalent displacement. For servo-hydraulic injection molding machines operating in three-shift production environments, the quieter operation contributed by the VG pump reduces operator fatigue, improves communication on the shop floor, and supports compliance with workplace noise regulations across different jurisdictions.

Minimal Pulsation and Its Direct Influence on Cycle Repeatability

Cycle repeatability is the single most important performance metric for high-volume injection molding production. Part weight consistency, dimensional accuracy, surface finish quality, and mechanical property uniformity all depend on the machine executing the same injection, packing, holding, and cooling profile on every single shot. Any variation in hydraulic pressure or flow during the cycle introduces variability into the plasticating and filling processes that manifests as defective parts, increased scrap rates, and production downtime for process adjustments. Achieving tight repeatability requires every component in the hydraulic chain to contribute minimal disturbance to the system.

The VG internal gear pump contributes to cycle repeatability primarily through its minimal flow pulsation characteristic. Flow pulsation from the hydraulic pump propagates through the system and appears as pressure oscillations at the injection cylinder or clamping cylinder. Even when the servo drive is operating in closed-loop pressure or velocity control, high-frequency pulsation from the pump can exceed the bandwidth of the control loop, introducing residual oscillation into the actual pressure and velocity profiles. By reducing pulsation at the source, the VG pump allows the servo controller to achieve tighter tracking of the programmed profiles, reducing shot-to-shot variation in fill time, switch-over pressure, and pack pressure during each molding cycle.

In practical terms, molders who adopt servo-hydraulic machines equipped with VG internal gear pumps report measurable improvements in part weight consistency and dimensional repeatability. The reduction in pressure ripple translates directly into fewer process adjustments, shorter setup times during mold changeovers, and reduced reliance on wide process windows to accommodate hydraulic variability. For applications in medical, optical, and electronic component molding where tolerances are measured in microns and every scrap part represents significant material cost, the cycle repeatability improvement enabled by the VG pump is a compelling economic and technical advantage that justifies the investment in premium hydraulic components.

Displacement Options: Matching the VG Pump to Machine Requirements

Selecting the correct pump displacement is essential for achieving optimal performance in a servo-hydraulic injection molding machine. An undersized pump forces the servo motor to operate at excessively high speeds to deliver the required flow, leading to increased wear, higher noise, and reduced motor life. An oversized pump wastes energy because the servo motor must still overcome the pump's internal friction even at low displacement utilization. The VG internal gear pump series addresses this selection challenge by offering displacements from 003 CC to 160 CC per revolution, covering machines from small laboratory-scale units to large-tonnage production cells used in automotive and industrial molding applications.

For small to medium servo-hydraulic machines in the 50 to 200 ton range, smaller displacement VG pumps in the 003 to 030 CC range are typically selected. These pumps deliver the flow rates required for typical injection speeds while operating within the efficient speed range of standard servo motors. For larger machines in the 300 to 1,000 ton range, higher displacement VG pumps up to 160 CC provide the large flow volumes needed for fast clamp movements and high-speed injection without requiring excessive motor speeds. The availability of single, double, and combined pump configurations further expands the design flexibility for machine builders optimizing their hydraulic circuit architecture for specific market segments.

Vicks Servo also supports custom pump sizing consultations through its engineering team, which includes over 120 dedicated R&D professionals with deep expertise in hydraulic system design for injection molding. By analyzing the machine's tonnage, stroke requirements, injection speed targets, and duty cycle, the team can recommend the optimal VG pump displacement and configuration for each application. This engineering support, combined with Vicks Servo's production capacity of over 200,000 units per year, ensures that machine builders can source precisely matched pumps at scale with dependable delivery schedules for their production planning needs.

Integration with Servo Drives and Motors: The Complete Hydraulic Solution

The performance of a servo-hydraulic injection molding machine depends not only on the pump but on the seamless integration of the pump, servo drive, and servo motor as a unified system. Vicks Servo addresses this requirement by offering a complete product ecosystem that includes the VG internal gear pump, the ABT Series servo vane pump, the ABT580-030 servo drive, and compatible servo motors and gearboxes. This integrated approach eliminates the compatibility issues that arise when sourcing hydraulic and electrical components from multiple vendors and ensures that the system is optimized end-to-end for injection molding performance and reliability.

The ABT580-030 servo drive from Vicks Servo is designed to handle the dynamic load profiles characteristic of injection molding cycles, including rapid acceleration during injection, precise pressure control during packing, and efficient energy recovery during deceleration phases. When paired with the VG internal gear pump's minimal pulsation output, the servo drive can operate with tighter control parameters, achieving faster response to setpoint changes and more accurate tracking of complex injection profiles. The result is a servo-hydraulic system that delivers the precision of all-electric machines—enabled by advanced motion technologies such as harmonic drive and servo control—with the force density and cost efficiency of hydraulic technology, giving machine builders a competitive advantage in the market.

For machine builders seeking maximum integration, Vicks Servo also offers the 3-in-1 Albert Servo Integrated Machine, which combines the servo motor, drive, and pump into a single compact unit. This configuration simplifies machine design, reduces wiring and plumbing complexity, and accelerates assembly time on the production line. Whether the application calls for discrete component sourcing or a fully integrated servo-hydraulic power unit, Vicks Servo provides the product range and engineering depth to support the complete solution from initial concept through volume production and field service support.

Manufacturing Scale and Quality Assurance at Vicks Servo

When selecting a hydraulic pump supplier for servo-hydraulic injection molding machines, manufacturing capability and quality assurance are as important as technical specifications. Vicks Servo Intelligent Equipment (Ningbo) Co., Ltd. has invested over USD 50 million in its manufacturing infrastructure, which spans more than 70,000 square meters of production and testing facilities. The company has accumulated over 18 years of hydraulic expertise, during which it has developed and refined the VG internal gear pump series and its broader product portfolio to meet the demanding requirements of the global injection molding industry and related hydraulic applications across multiple sectors.

Quality assurance at Vicks Servo encompasses the entire product lifecycle. Raw materials are sourced from certified suppliers and subjected to incoming inspection. The precision machining of VG internal gear pump components is performed on state-of-the-art CNC equipment under controlled environmental conditions. Each assembled pump undergoes performance testing that verifies flow rate, pressure capability, noise level, and volumetric efficiency against published specifications. This rigorous testing protocol ensures that every VG pump shipped from the factory meets the same performance standards, supporting the cycle repeatability and reliability that injection molding machine builders and end users require for their critical production operations.

Vicks Servo's commitment to quality and innovation is further validated by its recognition as a National Little Giant enterprise and a National High-Tech Enterprise, designations that reflect significant investment in research and development. The company holds over 20 patents related to hydraulic pump and servo system technology, and its team of more than 120 R&D engineers continuously works on advancing the performance, efficiency, and reliability of the VG series and supporting product lines. With an annual production capacity exceeding 200,000 units, Vicks Servo has the scale to serve both large OEM machine builders and smaller specialized manufacturers with consistent quality and dependable delivery schedules that support lean manufacturing principles.

Applications Beyond Injection Molding: Versatility of the VG Pump

While this blog has focused on servo-hydraulic injection molding machines, the VG internal gear pump is engineered for versatility across a broad range of hydraulic applications. The same combination of high pressure, low noise, minimal pulsation, and wide displacement range that benefits injection molding also delivers advantages in die-casting machines, hydraulic presses, lifting equipment, vulcanizing machines, shoe-making machinery, brick-making equipment, bending machines, and industrial balers. Any hydraulic application that requires precise flow control and consistent pressure delivery from a variable-speed drive can benefit from the VG pump's advanced internal gear architecture and precision manufacturing quality.

In die-casting applications, for example, the VG pump's ability to deliver high-pressure flow with minimal pulsation supports accurate control of the injection plunger speed profile, which directly influences casting porosity and surface finish quality. In hydraulic press applications, the pump's smooth flow output enables precise control of ram velocity and force during forming, stamping, or compaction operations. For lifting and material handling equipment, the ultra-low noise characteristic of the VG pump contributes to safer and more comfortable operation in environments where operator awareness of auditory signals is important for workplace safety compliance.

The breadth of applications served by the VG internal gear pump reflects Vicks Servo's deep understanding of hydraulic system requirements across diverse industries. By engineering a single pump platform that addresses the common needs of high-pressure, low-noise, and precise flow control, Vicks Servo enables machine builders in multiple sectors to standardize on a proven hydraulic component. This standardization reduces inventory complexity, simplifies maintenance training, and leverages the economies of scale achieved through Vicks Servo's production volume of over 200,000 units per year. For engineers evaluating hydraulic pump options for their next machine design, the VG series offers a compelling combination of technical performance, manufacturing quality, and supply chain reliability that supports long-term operational excellence.