Imagine this scenario: Your stamping production line is running at high speed, with a rhythmic hum from the presses, but the red bin for defective parts is piling up higher and higher in the quality control area. Parts are dimensionally unstable, burrs are abnormal, and occasionally there are tears or wrinkles. You can't help but wonder: Is it a problem with the die design? Or is there an issue with the material quality?
Before chasing down all the potential culprits, perhaps we should first examine something that is often taken for granted but is the invisible language that connects the three major elements of "press, die, and material"—the parameter settings.
Stamping parameter settings are far from being as simple as turning on the power and punching in numbers. It is a comprehensive art that combines engineering theory, material science, and practical experience. A slight adjustment to a single number can have a profound impact on product quality, die lifespan, production efficiency, and even operational safety. Incorrect settings not only put your expensive die at risk but are also a silent killer of corporate profits.
Today, leveraging over 70 years of industry experience, HIROKI will completely demystify the three core stamping parameters—die height, press tonnage, and stamping speed—to help you master this "golden code" that unlocks production line performance.
Summary of the 3 Core Stamping Parameters
| Core Parameter | Parameter Meaning | Risks of Improper Setting | Key Considerations & Solutions |
|---|---|---|---|
| 1. Die Height | The Foundation of Precision: Determines the closed clearance and stamping depth between the upper and lower dies. | Set too low (over-pressured): Catastrophic consequences, causing die cracking and press crankshaft damage. Set too high: Incomplete shearing, improper forming, and unstable quality. | Strictly follow SOPs, use tools like gauge blocks for precise measurement; manually "inch" the press to confirm the stroke; implement First Article Inspection (FAI). |
| 2. Tonnage | The Control of Force: Provides the necessary pressure for stamping and forming. | Insufficient Tonnage: The finished part cannot be fully formed, and long-term operation can damage the press. Excessive Tonnage: Wastes energy, exacerbates die impact and wear, and increases vibration. | Scientifically calculate the required pressure based on the material and process; maintain a 20-30% safety margin; choose a machine with a matching tonnage to avoid "using a sledgehammer to crack a nut." |
| 3. Stamping Speed (SPM) | The Rhythm of Efficiency: The number of stamping strokes per minute. | Too Fast: Insufficient material flow time leading to cracking, lubrication failure, die overheating, and slugs "floating" back up. Too Slow: Low production efficiency. | Adjust based on processing complexity (drawing is slow, blanking is fast); start at a low speed and gradually find the optimal balance between quality and efficiency; monitor die temperature. |
Parameter 1: Die Height — The Foundation of Precision
Of all the parameters, the die height setting is the most critical and least forgiving. It directly defines the "endpoint" of the force applied, making it the fundamental basis for success or failure.
What is Die Height?
In simple terms, it is the vertical distance from the bottom of the press slide to the press bed (bolster) when the slide is at its "bottom dead center" (the lowest point of its stroke). This distance must precisely match the die's own "shut height."
Fatal Consequences of Incorrect Settings
- Set Too Low (Over-pressured): This is the most serious error in stamping. When the die height is set lower than the die's shut height, the press attempts to compress the die into a space that doesn't exist. The results are catastrophic: at best, the die's cutting edges chip, guide pins deform, and punches break; at worst, it creates hundreds of tons of instantaneous overload, directly leading to the deformation or fracture of the press's crankshaft or connecting rods, with extremely high repair costs.
- Set Too High: While not causing immediate equipment damage, this leads to a series of quality problems. The pressure cannot be fully transmitted, resulting in incomplete shearing, unfinished forming, insufficient drawing depth, and final parts that are out of spec.
HIROKI's Setting Philosophy
- Follow SOPs: Before setting up the die, it is essential to clean both the die and the press bed. Strictly follow the SOP, using precision measuring tools like gauge blocks and calipers.
- Manual Stroke Confirmation: Before engaging automatic operation, you must switch to "inching" or manual mode and have the slide slowly complete at least one full stroke. Use your ears and eyes to confirm all components move smoothly without any abnormal interference or sounds.
- Impression or Lead Wire Test: For precision dies, a lead wire or special impression paper can be placed inside the die. After one stroke, measure its compressed thickness to deduce if the actual closing pressure and clearance are uniform.
- First Article Inspection (FAI): The first product manufactured must undergo a full dimensional inspection by quality assurance personnel. Only after everything meets the drawing requirements can mass production officially begin.
Parameter 2: Tonnage — The Control of Force
Tonnage represents the maximum force a press can output. Knowing how to correctly use this force is the dividing line between an amateur and a professional.
More Tonnage Isn't Always Better
A common misconception is that "using a large-tonnage press is always safe." While a high-tonnage press can provide sufficient pressure, the release of excessive energy brings many negative effects.
The Dilemma of Insufficient vs. Excessive Pressure
- Insufficient Pressure: The most direct consequence is an inability to stamp; parts cannot be formed, or they are not completely sheared. Operating a press at its tonnage limit for a long time, like a person under fatigue, accelerates the aging and damage of its mechanical structure.
- Excessive Pressure: First, there is massive energy waste. Second, every stroke is like a "heavy blow," creating unnecessary huge impact and vibration on both the die and the press itself. This not only accelerates die wear but also affects the press's own precision lifespan.
How to Scientifically Select Tonnage
- Pre-Calculation: During the die design phase, the required basic shearing and forming forces should be calculated using engineering formulas based on parameters like material shear strength, thickness, and part perimeter.
- Safety Factor: Considering factors like material hardness fluctuations, lubrication changes, and die wear, the actual selected press tonnage is usually based on the calculated value with a 20% to 30% safety margin.
- Reference Production History: Maintain a file for each die, recording which press and what tonnage pressure were most suitable for its production in the past. This big data aids in decision-making.
Parameter 3: Stamping Speed (SPM) — The Rhythm of Efficiency
Stamping speed (Strokes Per Minute, SPM) is directly related to production efficiency, but it is also closely linked to product quality and die lifespan. A delicate balance must be struck between the two.
The Trade-off Between Speed and Quality
Increasing speed means increasing capacity, but it also compresses the time the material has to "react" inside the die.
The Hidden Killers of Excessive Speed
- Insufficient Material Forming Time: Especially in deep drawing processes, an excessively high speed does not allow enough time for the material to flow and stretch, leading to thinning and tearing at the corners of the part.
- Lubrication Failure and High Heat: Lubricants need time to form a film. If the speed is too high, the film doesn't have time to form before being broken, causing severe friction. The die temperature rises sharply, which can scratch the workpiece or, worse, anneal and soften the die's cutting edge, drastically reducing its lifespan.
- Ejection and Slug Removal Issues: A speed that is too high may prevent the punched slugs from falling out of the lower die hole or the finished parts from being ejected by an air jet or robot. This can lead to "slug stacking" in the next stroke, with unimaginable consequences.
Finding the Optimal Production Rhythm
- Based on Process Characteristics: Generally, simple blanking and punching processes can tolerate higher speeds, while complex drawing, bending, and embossing require a slower speed to give the material enough time to form.
- Gradual Adjustment: Start trial production at a low speed recommended by the equipment and die, and then gradually increase it once stability is achieved. During the increase, closely monitor product quality and die temperature. If a degradation trend appears, stop immediately and dial back.
- Listen to the Machine's Sound: Experienced technicians can judge whether the current settings are smooth and stable from the sounds and vibrations of the press. A steady rhythm is a healthy rhythm.
Common Questions about Stamping Parameter Settings (FAQ)
A1: All three are important, but for a novice, the correct die height setting is an absolute red line that concerns safety. Improper tonnage and speed settings usually first show up as a quality problem, giving you a chance to adjust. However, an incorrect die height setting (especially if it's too low) often leads to immediate and catastrophic consequences. A novice must, under the guidance of an experienced technician, repeatedly practice and confirm the die height setting process.
A2: This is key to ensuring a smooth progressive die operation. The feeder's length and speed must precisely match the press's SPM and stroke angle. Generally, the feeding action should be completed when the press slide is near the "top dead center" (approximately the 9 o'clock to 3 o'clock position). If the feeding is too slow, the material won't be in position, resulting in a half-formed part. If it's too fast or too long, it will cause material waste and interference. Modern servo feeders can usually be connected to the press's encoder to achieve precise electronic synchronization.
A3: A tonnage monitor is an extremely powerful quality control and die protection tool. It can monitor the actual pressure curve of every stroke in real-time. Its two main functions are: 1. Quality Monitoring: If the pressure curve suddenly deviates high or low, it indicates an anomaly (e.g., material thickness variation, lubrication failure), and it can trigger an alarm and stop the machine. 2. Die Protection: You can set a pressure limit. If an accident like slug stacking causes the pressure to spike instantly, the monitor will immediately stop the press, preventing fatal damage to the die.
A4: Deep drawing is one of the most difficult stamping processes, and parameter settings are even more critical. In addition to a slower stamping speed, special attention must be paid to the "Blank Holder Force." The blank holder force is the pressure that the blank holder applies to the material's edge. If it's too high, the material flow will be difficult, causing cracking. If it's too low, the material will wrinkle. This force is usually provided by the press's air cushion system and requires fine-tuning based on the material's properties, which is key to the success of deep drawing.
A5: Absolutely! This is a blind spot for many factories. Even if the grade is the same, materials from different steel mills or different batches can have subtle variations in their yield strength, ductility, and even surface roughness. These differences will directly affect springback and forming force. Therefore, after changing material suppliers, you should at least conduct a rigorous dimensional inspection of the first part and micro-adjust parameters like die height and blank holder force based on the inspection results to ensure stable quality.
Conclusion
Stamping parameter setting is a dynamic process of seeking the optimal balance between precision, force, and efficiency. There is no one-size-fits-all formula. Only through a deep understanding of the core principles, combined with a rigorous Standard Operating Procedure and accumulated practical experience, can one truly master it.
HIROKI CO., LTD. not only provides high-quality stamping services, but we also integrate our expertise in parameter management into every aspect of our daily production. We believe that stable parameters are the foundation of stable quality. If you want to get rid of your parameter setting headaches and seek a reliable partner who can manage all the complex details for you, feel free to contact our team.