In stamping dies, nitrogen gas springs are typically used to provide holding force, unloading force, or ejection force. A characteristic of standard nitrogen gas springs is that they return to their fully extended position immediately at full speed after one stroke of the press ram. While this poses no problem in most operations, in processes such as deep drawing, forming, and oblique wedge side punching, “immediate return” can actually lead to a series of issues, including workpiece deformation and die damage.
Delayed-return nitrogen gas springs are specifically designed to address this problem.
I. What Are Delayed-Return Nitrogen Gas Springs?
Delayed-return nitrogen springs (also known as delayed-reset nitrogen springs) provide stable spring force during compression, just like standard nitrogen springs. The difference lies in the fact that during the press’s return stroke, they can remain compressed for a period of time or return slowly in a controlled manner, returning to their initial position only after the upper die has cleared the workpiece and the relevant mechanisms have completed their operations.
Simply put:
Standard nitrogen gas spring: As the slide moves upward, the spring immediately springs back.
Delayed-return nitrogen gas spring: As the slide moves upward, the spring “pauses” briefly before returning to its initial position at the appropriate time.
II. What problems do standard nitrogen gas springs cause in stamping operations?
1. Workpiece Deformation
After deep drawing is complete, if the flange ring is rapidly lifted before the punch has left the workpiece, the workpiece’s flange or side walls will be subjected to a reverse impact, causing deformation, wrinkling, or dimensional deviations. For appearance-critical parts such as automotive body panels, such defects often result directly in scrap.
2. Workpiece Ejection or Jamming
The impact force generated by the instantaneous return of the hold-down plate may cause the workpiece to be pushed off-center or ejected, interfering with automated part removal and, in severe cases, leading to safety incidents.
3. Interference with the Tapered Wedge Mechanism
In dies featuring side punching or side trimming with a tapered wedge, if the hold-down plate returns before the tapered wedge slider retracts, interference between the two is likely to occur, damaging the die or the workpiece.
4. High Impact and Noise
When the spring returns at full speed, the hold-down plate strikes the stop block, generating significant impact and noise. Over time, this accelerates wear on die components.
III. How Do Delayed-Return Nitrogen Springs Solve These Problems?
Protecting Workpiece Quality
During the return stroke, the holding ring or hold-down plate remains stationary and resets only after the punch has completely cleared the workpiece. This eliminates reverse impact on the workpiece, significantly reducing deformation and dimensional issues.
Ensuring Orderly Process Sequencing
Delayed reset allows time for mechanisms such as the inclined wedge and side punch to retract, ensuring components operate in sequence and avoiding interference.
Improving Automation Stability
Workpieces are no longer ejected or pushed off-center, allowing robots and conveyor lines to retrieve parts more reliably, which helps increase production cycle times.
Simplifying Die Structure
In the past, achieving similar results often required the installation of additional hydraulic delay systems or complex mechanical locking mechanisms. Delayed-return nitrogen gas springs integrate this functionality into the spring itself, resulting in a simpler die design and easier maintenance.
IV. Typical Application Scenarios
· Deep-drawing dies for automotive body panels and structural parts
· Dies with side punching and side trimming featuring inclined wedges
· Forming processes requiring delayed ejection
· Processes on single-action presses that require a double-action effect
· Applications in automated stamping lines and multi-station dies where high part-removal stability is required
V. What to Consider When Selecting a Model?
When selecting delayed-action nitrogen gas springs, it is recommended to focus on the following parameters:
· Initial spring force and final pressure: Calculate the required quantity and specifications based on the required holding force and ejection force.
· Stroke: Allow for a safety margin to prevent the spring from being fully compressed.
· Delay mechanism and delay time: Determine whether adjustability is required and whether the delay matches the press cycle time.
· Installation space and mounting method: Verify that the mold closing height and installation location meet requirements.
· Operating frequency: For high-speed production lines, pay attention to heat dissipation and service life.
Nailite Nitrogen Springs is a brand under Dongguan Tengfei Hardware & Mold Co., Ltd., a technology-driven enterprise specializing in the integrated R&D, production, sales, and service of nitrogen springs (robot balancing cylinders). Our products hold multiple national patents and EU certifications and are exported to numerous countries and regions worldwide. For inquiries, please call Ms. Zhou at +86-13922516997.
