Frequently Asked Questions (FAQ)
- What is a Knuckle Joint Press?
It’s a type of mechanical press that uses a knuckle joint mechanism, which delivers high force near the end of the stroke. It’s commonly used in deep drawing and precision forming applications.
- What’s the difference between an eccentric press and a knuckle joint press?
Knuckle joint presses wait longer and apply more force at the bottom dead center than eccentric presses. They are slower but more precise.
- What kind of jobs are knuckle joint presses used for?
Ideal for deep drawing, panel radiator production, coin minting, powder metal forming, and gear surface shaping—applications that need both force and precision.
- What are the disadvantages of knuckle joint presses?
They are slower than eccentric presses, not suitable for continuous high-speed stamping, and require more maintenance due to their complex joint mechanism.
- Can a knuckle joint press run at full tonnage all the time?
No. Like all presses, it should ideally run at 70–80% of its capacity for longer life. Full tonnage should only be used briefly.
- Can the stroke length be adjusted?
In most knuckle joint presses, the stroke is fixed.
- Why does the press apply more force at the bottom?
The knuckle joint slows down as it nears the bottom, almost locking in place. This creates a mechanical advantage, generating very high force at the bottom.
- Can these presses be used for high-speed production?
No. Due to their design, they work slowly—usually between 10 and 80 strokes per minute.
- What maintenance is needed?
The joints, arms, and pins must be regularly lubricated and checked for looseness. Poor maintenance can cause misalignment.
- How noisy are knuckle joint presses?
They are generally quieter than other mechanical presses due to less vibration, but hearing protection is still needed above 80 dB.
- Which industries use knuckle joint presses?
Used in panel radiator manufacturing, automotive parts, home appliances, watchmaking, coin minting, powder metallurgy, medical implants, and thin-wall aluminum parts.
- Can knuckle joint presses cut thick sheet metal?
No. They’re not suited for impact operations like cutting or punching. They’re better for forming and drawing.
- What should you check when buying one?
Look at frame structure, stroke length, speed, bottom dwell time, joint quality, lubrication type, and automation options.
- Can knuckle joint presses be powered by servo motors?
Yes, newer models may use servo motors for better precision and energy savings—but this is rare. Direct servo presses are usually preferred.
- What’s the difference between classic and servo-driven models?
Servo types allow adjustable stroke and pressing time, offering better precision and lower energy use.
- Are they better for forming or cutting?
Forming, deep drawing, and shaping are ideal. For cutting, eccentric presses are better.
- Do they follow the same CE and safety standards as eccentric presses?
Yes. Standards like EN 692, EN ISO 12100, and EN ISO 13849 apply to both.
- How does bottom dwell affect part quality?
Staying longer at the bottom helps fully form the part, improving surface finish and extending die life.
- Can dies be changed automatically?
Yes, on modern presses. Older models usually require manual or semi-automatic die change.
- Can the dwell time at bottom be adjusted?
Only on servo-controlled models. In traditional presses, mechanical limits apply, and the mechanism must be redesigned to change it.
- Is springback a problem during forming?
Very little. The long pressing time at bottom helps the material fit the die better, reducing springback.
- Do joints wear out over time?
Yes, pins and bearings can wear. Regular lubrication and clearance checks are necessary to prevent problems.
- How is the press force curve different?
Unlike a sinusoidal curve, force increases as speed drops at the end of the stroke, resulting in better forming quality.
