Press Comparison Guide: Mechanical vs. Servo Press Technology

Selecting the right press machine for your metal stamping operations is crucial and requires a thorough understanding of the different types of machines available. Certain press types are better suited to specific production needs.

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Mechanical Press Technology

A mechanical stamping press is a machine that delivers substantial force through mechanical means, utilizing a flywheel, crankshaft, and clutch-brake mechanism. These presses are essential in metal forming operations due to their reliability, efficiency, and ability to produce high volumes of parts with consistent quality. A common variation of the mechanical press is the frame type, which we compare in another article: C frame vs. straight side presses.

Working Principle & Applications - Mechanical Presses

The fundamental working principle of a mechanical press is to convert rotational energy into linear motion. The flywheel stores this rotational energy and releases a controlled portion to drive the ram, which applies force to shape the material according to the tool and die composition. This process is fast and precise, making mechanical presses crucial in high-volume production environments.

Mechanical presses are versatile and are commonly used for various metal stamping applications, including:

- Blanking

- Coining

- Drawing

- Shearing

- Embossing

- Bending

- Punching

Advantages - Mechanical Presses

Speed & Efficiency  

Mechanical stamping presses excel in high-speed operation, making them ideal for large-scale production where time is critical. Their continuous, rapid cycles ensure high output, perfect for repetitive, high-volume tasks.

Reliability & Durability  

Known for their robustness, mechanical presses are built with proven, refined technology that minimizes breakdowns and maintenance, ensuring continuous operation with minimal downtime.

Power  

Mechanical presses deliver significant power, making them well-suited for heavy-duty applications, such as those requiring thick, resistant materials or significant material deformation like deep drawing.

Cost Effectiveness  

Mechanical presses often present a more budget-friendly option compared to servo presses. They generally require lower initial investment and maintenance costs, resulting in a lower total cost of ownership.

Limitations - Mechanical Presses  

Flexibility  

Mechanical presses have limited flexibility in terms of stroke length and profile. Unlike servo presses, which can adjust these parameters, mechanical presses typically have fixed stroke lengths and speeds.

Energy Consumption  

Mechanical presses tend to consume more energy. The flywheel requires continuous operation throughout the press cycle, resulting in a steady power draw, which can be higher compared to servo presses that only consume energy when in motion.

Noise Levels  

Mechanical presses often generate higher noise levels due to their mechanical operations. This may require additional noise reduction measures, such as sound enclosures or protective gear, to ensure a safe environment for operators.

One way to mitigate these limitations is by using adjustable stroke technology combined with a variable frequency drive, offering servo-like flexibility while maintaining the simplicity and consistency of a mechanical press.

Servo Press Technology  

What sets a servo press apart in press technology is its use of servo motors, unlike traditional mechanical presses. These machines utilize servo motors to drive the press ram mechanism, providing high accuracy and flexibility. Servo presses are programmable, allowing precise control of slide position, speed, and pressure, making them ideal for complex and varied stamping tasks.

Working Principle & Applications - Servo Presses

A servo press relies on a servo motor that directly controls the ram movement. Unlike mechanical presses with fixed cycles determined by the flywheel, a servo press adjusts its stroke and speed in real time based on the task, with software controlling the servo motor for on-the-fly adjustments. This flexibility allows the press to be tailored to specific production needs.

Many of the applications suited for mechanical presses can also be performed with a servo press.

Advantages - Servo Presses

Some of the standout aspects of servo press technology lie in the amount of precision and control that it provides users. Unlike a mechanical press which operates on a fixed cycle, a servo press has a highly programmable stroke profile. This allows the user to adjust the motion, speed, and position of the slide at any point in the stroke. Servo presses can pause or slow down at specific points in the stroke, allowing time for feeds or transfer systems to complete their function. This feature makes complex forming processes more feasible, especially when gradual or variable force is required to ensure high part quality.

Energy Efficiency  

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Servo presses are energy-efficient, consuming power only during the stamping process, unlike mechanical presses, which draw energy constantly when powered on. Additionally, servo presses optimize the stroke profile for specific tasks, further enhancing energy efficiency.

Versatility  

The programmability of the stroke profile makes servo presses highly versatile. They can adapt to various materials, thicknesses, and forming requirements without needing manual or physical adjustments. This versatility makes servo presses ideal for operations with a high mix of parts with different requirements.

Reduced Set-Up Times  

With tool/program storage capabilities, servo presses can easily recall and adjust to stored programs. This significantly reduces setup and changeover times, which is especially beneficial for high-mix, low-volume stamping operations.

Limitations - Servo Presses

Initial Investment  

Servo presses come with a higher initial cost due to advanced controls, programmable features, and other components. This can be a barrier for smaller operations or those with limited budgets.

Maintenance  

The complexity of servo presses, involving both mechanical and software components, makes maintenance more intricate than that of mechanical presses. Specialized knowledge and expertise are needed, leading to higher maintenance costs, training expenses, and specialized diagnostics, which contribute to a higher total cost of ownership.

Operator Training  

Due to the complexity and programmability of servo presses, operators require more extensive training. Maintaining a skilled workforce is crucial to maximizing the press's capabilities, but it can be challenging in areas with limited skilled labor or for companies that don't prioritize personnel development.

Reduced Operating Speeds  

While offering superior control and programmability, servo presses operate at slower speeds compared to mechanical presses. For operations requiring high-speed stamping, servo presses may not be the ideal choice.

Comparing Mechanical and Servo Presses

Key Considerations:

- Mechanical Presses are ideal for high-volume tasks, offering speed, reliability, and cost-effectiveness.

- Servo Presses are ideal for complex and precise applications that require control, flexibility, and adaptability.

Both press types require skilled operators and proper training, but servo presses demand more technical expertise due to their advanced control systems.

Servo Presses offer the best of both worlds – the slide velocity variability of hydraulic presses at the same or faster production speeds than mechanical presses.

The servo motors and controls that run servo presses account for the combined benefit of flexibility and speed.

But let’s step back and take a look at traditional mechanical presses to understand why servo presses are different. In mechanical presses, the flywheel mass and speed determine the amount of working energy available to form a part. This works well until a slower slide velocity is required to form the part effectively (since metal generally flows and forms better at slower speeds). To achieve the slower slide velocity, the flywheel needs to rotate more slowly, which diminishes the amount of working energy, preventing the press from properly forming the part.

No More Flywheel

On a servo press, however, the servo motor replaces the flywheel, clutch and brake and provides full working energy during the stroke at any speed, even supplying continuous force while dwelling.

Unlike traditional mechanical presses, which operate at a fixed speed through the entire stroke length, servo presses can vary the speed throughout the entire stroke, moving quickly through the non-working portion of the stroke (before and after the die) and moving at optimum forming speeds (usually slower) through the working portion of the stroke.

The greater speed control has allowed some of our customers to double their production output.

Fully Programmable

The servo motors and controls also easily manipulate the crankshaft position, allowing for a broad range of highly precise stroke profiles. Best of all, the stroke, slide motion, slide position and speed are all programmable, enabling different combinations that can work with a wide variety of dies and part types.

Preprogrammed profiles on Stamtec presses include:

• Standard crankshaft motion
• Simulation of link control
• Compound pressing and forging
• Deep drawing
• General forming
• Perforation/blanking
• Fineblanking
• Warm forging
• Pendulum/Swing
• Multi-pass

Applications

Servo presses are particularly well-suited for deeper drawing or more difficult forming applications. In fact, a servo press can often perform more drawing and forming in one station than a traditional mechanical press can do in multiple stations, allowing manufacturers to consolidate the number of presses needed for a project or to use presses with smaller beds.

Servo presses provide even greater flexibility in stroke lengths. Even if a press’s full stroke is eight inches, a servo press can provide a two-inch, four-inch or six-inch stroke length in pendulum mode.

In the end, a servo press is still a mechanical press, with its greatest tonnage capacity at the bottom of the stroke. But the advantages in speed, part quality and precision set servo presses apart from traditional mechanical presses.

If you want to learn more, please visit our website Servo Straight Side Double Points Press.