In a small servo press design, stroke length directly determines how efficiently and accurately a forming process performs. The distance the ram travels from top to bottom affects every key factor — forming depth, cycle speed, energy use, and tool life.
In high-precision applications such as electronics, connectors, or miniature brackets, selecting the proper stroke length is more than a mechanical setup. It’s an engineering choice that balances motion range, control precision, and system efficiency. As servo technology evolves, stroke optimization has become a vital step in achieving both speed and consistency on small presses.
Understanding Stroke in Servo Presses
Stroke length is the total vertical distance the press ram travels between top dead center (TDC) and bottom dead center (BDC). It defines the press’s forming envelope — how far the ram can move, and how deeply it can shape a part.
In traditional mechanical presses, this stroke is fixed. The press must travel its full range for every cycle, even if the actual forming depth is small. A servo press changes that. Using an electric servo motor, engineers can program exact positions, speeds, and accelerations with precision as fine as 0.01 mm.
This flexibility creates three types of stroke definitions:
- Total stroke: The full mechanical travel of the ram.
- Working stroke: The active segment used for forming or cutting.
- Adjustable stroke: The programmable range is tailored to each product or die height, ensuring optimal performance.
Modern servo control systems enable the adjustment of these parameters in seconds through digital input — eliminating the need for mechanical modification. The result is reduced setup time, less mechanical wear, and higher throughput.
How Stroke Affects Press Performance？
Stroke directly influences the press’s mechanical behavior, efficiency, and the quality of the final part.
- Forming Capability – Longer strokes provide a deeper forming range but increase cycle time and energy use.
- Speed and Energy Efficiency – Shorter strokes eliminate idle motion, cutting wasted time and lowering power draw.
- Part Accuracy and Die Life – Properly tuned stroke profiles reduce impact load at BDC, improving consistency and extending tool lifespan.
According to servo press forming tests conducted on 2-ton compact systems, reducing the stroke from 80 mm to 40 mm can improve cycle efficiency by 35% while lowering energy consumption by up to 40% per cycle. The shortened travel distance also decreases vibration, which helps maintain flatness and tight dimensional tolerances (within ±0.01 mm).
In practical terms, stroke optimization is not about choosing “short” or “long.” It’s about matching stroke motion to forming load and part geometry.
Core Principles for Stroke Length Selection
Selecting the stroke length for a small servo press involves striking a balance between productivity, accuracy, and tooling safety. The following engineering principles guide this decision.
Matching Stroke to Application Type
Different processes demand distinct stroke behaviors:
| Process Type | Typical Stroke Range | Key Motion Focus | Исход |
|---|---|---|---|
| Blanking / Coining | 15–40 mm | Rapid approach, precise dwell | Maximum speed, minimal wear |
| Формовка / гибка | 40–80 mm | Balanced motion and control | Flexibility across part types |
| Deep Drawing / Multi-step Forming | 80–120 mm | Slow forming near BDC | Reduced wrinkling, uniform wall thickness |
Choosing the right stroke ensures that each process uses the minimum motion necessary to complete the forming process. This minimizes idle time while maintaining the proper pressure profile.
For example, a servo press producing small copper terminals at a 30 mm stroke can reach 500 strokes per minute. In contrast, the same machine, running a 90 mm stroke for deep-drawn aluminum parts, may operate at one-third that speed — yet achieve far greater forming depth and material stability.
Considering Material and Die Requirements
Stroke selection must account for material strength, thickness, and die setup height to ensure optimal results.
- Thinner and softer materials (like copper or aluminum) can form fully within shorter strokes.
- Harder materials (like stainless steel) may need longer strokes and controlled speed profiles to prevent cracking.
Equally important is the shut height, the distance between the slide and bolster when the ram reaches bottom dead center. If the stroke is too short, the die cannot close properly, risking incomplete forming. Too long, and the machine wastes energy or risks excessive wear and tear.
Servo presses address this by utilizing position and force sensors to detect die contact in real-time. The control system automatically stops at the programmed forming limit, preventing overtravel and extending die life.
Balancing Precision and Productivity
Engineers must balance two competing goals: speed and accuracy. A longer stroke allows for gradual forming with a stable pressure distribution, but it extends the cycle time. A shorter stroke boosts speed but can cause incomplete forming if material flow isn’t well controlled.
Servo technology solves this trade-off with programmable acceleration curves. During forming, the servo motor decelerates precisely near BDC — creating a “soft landing” motion that maintains shape accuracy while minimizing tool stress.
Studies on micro-stamping applications demonstrate that applying a controlled dwell time of 50–150 ms near the BDC can reduce springback and improve shape stability by up to 20–30% compared to constant-speed forming.
Servo Technology Advantages in Stroke Control
Servo technology gives engineers a new level of freedom in defining how a press moves. This flexibility enables small servo presses to function like multiple machines in one, adapting to different products without requiring hardware changes.
Programmable Stroke and Motion Profiles
A servo drive allows engineers to program stroke motion with positional accuracy up to 0.01 mm and motion speed profiles as fine as 1 ms increments. That means each part can have its own motion “recipe.”
Например:
- Быстрый подход to shorten idle travel.
- Медленное формирование near the bottom dead center (BDC) to stabilize material flow.
- Short dwell time (50–150 ms) to release stress and improve shape retention.
- Rapid return to prepare for the next cycle.
Servo motion control software can store multiple stroke configurations and automatically load them based on part code or die ID, thereby minimizing changeover time.
This versatility enables a single 3-ton servo press to perform гашение, изгиб, and shallow forming operations without requiring any hardware modifications — saving hours of mechanical adjustment time compared to conventional presses.
Energy Efficiency Through Dynamic Motion
Energy use is a measurable advantage of servo control. Traditional presses consume the same power every cycle because they must move through their entire mechanical stroke, even when the forming depth is shallow. Servo presses use only the motion needed.
By shortening the stroke from 80 mm to 40 mm and using regenerative braking during deceleration, energy consumption can drop from 0.75 kWh/100 cycles to 0.45 kWh/100 cycles — a 40% efficiency improvement measured on small-tonnage systems.
This optimization also reduces heat buildup, mechanical vibration, and noise, thereby improving the long-term life of components.
Over a full production shift, such optimization can save 8–12 kWh per machine, equivalent to several hundred dollars of power cost each month in continuous production environments.
High-Speed Response for Small Parts Production
Precision electronic and medical components require both speed and repeatability. A servo press with a short programmable stroke (20–40 mm) can reach 400–600 SPM (strokes per minute) while maintaining force consistency within ±1%.
This high-speed accuracy is achieved through torque-vector control algorithms that adjust motor output in real-time based on load feedback. Because acceleration and deceleration are independently programmable, the system avoids overshoot and vibration that can distort small parts.
When used in micro-stamping or connector manufacturing, this stability directly translates to fewer rejects, reduced maintenance, and longer die life.
Key Engineering Factors in Stroke Selection
Stroke selection is not only a mechanical range issue — it involves how force, displacement, and motion timing interact to produce optimal results—the following parameters guide stroke optimization in servo press applications.
Shut Height and Die Setup Compatibility
The shut height determines the minimum gap between the slide and bolster at BDC.
A mismatch between stroke range and shut height can cause part deformation or die failure.
To maintain safe margins:
- Maintain a clearance of 10–15 mm between the bottom stroke limit and the die set height.
- Use the servo software’s electronic stop function to prevent over-travel.
- Re-calibrate shut height after any die replacement or tool wear adjustment.
Servo presses with digital stroke positioning automatically verify this clearance via encoder feedback, eliminating the need for mechanical trial-and-error alignment.
Force–Displacement Relationship
In real forming, the press does not apply constant tonnage across the stroke.
The forming force rises sharply as the material yields and reaches its peak near BDC, creating a force–displacement curve that defines how the part deforms.
A typical curve includes four regions:
- Approach: Light load, rapid motion.
- Plastic Deformation: Force rises sharply.
- Peak & Dwell Zone: Maximum forming load; speed slows for accuracy.
- Springback Region: Slight reverse movement to release internal stress.
Servo control enables precise management of each region.
Engineers can shape the curve by adjusting motor torque and velocity, ensuring that maximum force coincides exactly with material flow needs — not before or after.
Tests on 1-ton servo presses forming 0.6 mm stainless steel parts showed that torque-synchronized control reduced peak load variation by 18%, extending die life by approximately 25%.
Cycle Time Optimization
Every unnecessary millimeter of travel adds delay. Servo programming allows the stroke limit to change dynamically between cycles, meaning the ram only moves as far as the forming depth requires.
This optimization can reduce each cycle by 20–30%, resulting in several thousand extra parts per day in high-volume lines. When combined with synchronized feed systems, servo presses can maintain precise timing even as stroke length varies — eliminating wasted motion while preserving accuracy.
For example, shortening a cycle from 0.6 s to 0.45 s may seem small, but over 50,000 cycles, it yields 12,500 more parts per shift with identical power input.
Common Mistakes in Stroke Selection
Even with servo control, incorrect stroke setup can cause energy waste, tool damage, or production delays. Understanding these mistakes helps prevent inefficiency and maintain consistent forming results.
1. Using the Same Stroke for Every Operation
Issue:
Many operators use a default stroke for all jobs, regardless of part height or forming depth.
Effect:
This increases idle motion, adds cycle time, and consumes unnecessary energy.
Correction:
Define specific stroke presets for each product and material type. A 20 mm stroke for thin copper may achieve the same forming quality as an 80 mm stroke, with 40% shorter cycle time.
2. Overestimating Stroke “for Safety”
Issue:
Operators extend stroke length to avoid tool collision, believing longer travel ensures clearance.
Effect:
Excess motion leads to slower cycles and higher wear on drive components.
Correction:
Use servo position sensors and electronic limit stops. They maintain safe clearance without extending motion. The machine stops within ±0.01 mm of programmed limits, eliminating mechanical overtravel.
3. Ignoring Shut Height and Die Stack Tolerance
Issue:
A mismatch between the stroke and die stack height causes either underforming (too short) or excessive load (too long).
Effect:
Poor part quality, uneven pressure, or die cracking.
Correction:
Recalibrate the shut height using the servo’s digital readout. Maintain a clearance of 10–15 mm beyond die closure for safe ejection and consistent part forming.
4. Neglecting the Force–Stroke Curve
Issue:
Setting the stroke based only on geometry, not on how force builds across the stroke.
Effect:
Excessive peak loads or uneven material flow can lead to premature die wear.
Correction:
Use the servo system’s force–displacement monitoring feature. By shaping the curve to match material behavior, engineers can lower peak load by up to 20%, stabilizing dimensional accuracy and extending die lifespan.
5. Failing to Re-Evaluate Stroke After Tool Changes
Issue:
After the maintenance or tool replacement, many operators reuse previous stroke settings.
Effect:
Small dimensional changes can cause overpressure or incomplete forming.
Correction:
Re-run a stroke calibration cycle whenever tooling changes occur. Servo presses with stored motion data enable this process to be quick and repeatable, ensuring consistent setup accuracy.
Summary Table: Common Stroke Errors and Solutions
| Ошибка | Engineering Impact | Рекомендуемое действие |
|---|---|---|
| Fixed stroke for all jobs | Energy waste, slower cycles | Use application-based stroke presets |
| Overlong stroke “for safety” | Reduced speed, component wear | Apply digital limit control |
| Mismatched shut height | Tool damage, poor forming | Recalibrate after die setup |
| Ignoring force curve | Overload, inconsistent parts | Tune motion to peak load zone |
| No recalibration post-tooling | Inconsistent results | Verify stroke after each change |
Заключение
Stroke length selection is one of the most defining parameters in determining the performance of small servo presses. It affects not just how a press forms metal, but how efficiently it operates and how long the tooling lasts. A well-chosen stroke minimizes wasted movement, improves energy efficiency, and keeps part accuracy within tight tolerances.
Seeking to enhance forming efficiency with a compact servo press? Our engineering team can help you define the optimal stroke configuration for your materials and processes. Свяжитесь с нами сегодня to request a free manufacturability review or discuss your next servo press project.
Привет, я Кевин Ли
Последние 10 лет я занимался различными формами изготовления листового металла и делился здесь интересными идеями из своего опыта работы в различных мастерских.
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Кевин Ли
У меня более десяти лет профессионального опыта в производстве листового металла, специализирующегося на лазерной резке, гибке, сварке и методах обработки поверхности. Как технический директор Shengen, я стремлюсь решать сложные производственные задачи и внедрять инновации и качество в каждом проекте.
