For the punching process of small bag food, can replacing the die with a 6.35μm size improve the punching yield?

1. Wstęp: Core Requirements of Blanking Process for Small-Pouch Food Packaging

The blanking process is critical for small-pouch food packaging (NP., 10-50g nuts, 20ml seasonings). Its core requirements include: no burrs (≤0.1mm), no tearing, and reliable heat-seal tightness (oxygen transmission rate ≤0.3cm³/(m²·24h·atm)).

Notably, blanking defects (burrs, rozdzierający) disrupt heat-seal adhesion, raising seal failure rates by 40%-60%. This directly shortens food shelf life—for example, nuts may see their shelf life drop from 6 Do 3 miesiące, which harms both product quality and consumer trust.

Obecnie, 6μm aluminum foil/plastic composite film dominates the market, holding a 55% share. Jednakże, its inherent thinness creates two key issues during blanking.

Pierwszy, excessive burrs: burr lengths range from 0.15 to 0.3mm, exceeding the limit set by GB/T 18454-2019 by 50%-200%. This excess leads to heat-seal misalignment, further compromising packaging integrity.

Drugi, rozdzierający: the blanked area of 6μm material has an 8%-12% tearing rate, which directly generates scrap and increases production losses.

To address this challenge, the industry has proposed switching to 6.35μm material (equivalent to 2.5mil, an international standard for thin packaging). This 0.35μm thickness increment is designed to enhance both mechanical properties and blanking adaptability.

To justify the adoption of 6.35μm material, we analyze how the advantages of 6.35μm over 6μm in blanking improve yield from five key dimensions: defect causes, performance comparison, blanking mechanics, experimental verification, and economic analysis.

2. Core Causes of Blanking Defects in 6μm Material

The root cause of defects in 6μm material lies in a “mismatch between material properties and blanking stress”. A reverse examination of the advantages of 6.35μm over 6μm in blanking reveals three critical limitations of 6μm material.

(1) Weak Mechanical Properties: Insufficient Shear Resistance

Blanking relies on the principle of “shear fracture”—die edges apply vertical force to split the material along predefined edges.

6μm material has a shear strength of approximately 45MPa (per GB/T 1040.3-2006), which is 13.5% lower than 6.35μm material’s 52MPa.

Under typical die pressure (0.8-1.2MPa), 6μm material lacks the strength to achieve “neat fracture”. Zamiast, it undergoes “edge extrusion deformation”, which directly forms burrs along the blanked edge.

(2) Weak Mechanical Properties: Poor Tear Resistance

Beyond insufficient shear resistance, 6μm material also suffers from poor tear resistance. Its right-angle tear strength is roughly 0.8kN/m (per GB/T 11999-1989), a value that is only 72.7% of 6.35μm material’s 1.1kN/m.

After blanking, microcracks inevitably form on the edges of 6μm material. Worse still, its crack propagation rate (0.5mm/s) is nearly double that of 6.35μm material (0.3mm/s).

These microcracks easily expand into visible tearing during subsequent handling or heat-sealing, which highlights the advantages of 6.35μm over 6μm in blanking when it comes to crack resistance.

(3) Poor Thickness Uniformity

Adding to mechanical weaknesses, 6μm material exhibits poor thickness uniformity. Most small-pouch packaging materials use a three-layer “folia aluminiowa + PE + ZWIERZAK DOMOWY” structure. The ultra-thin aluminum layer in 6μm material leads to a thickness deviation of ±5%—local thin spots can be as thin as 5.7μm.

By contrast, 6.35μm material has a much tighter thickness deviation of ±3%, with local thin spots no thinner than 6.15μm.

This uniformity gap significantly amplifies stress concentration: the stress concentration factor (σ_max/σ_avg) at thin spots in 6μm material is 1.8, compared to just 1.4 in 6.35μm material.

Thin spots in 6μm material reach their fracture strength first, forming irregular burrs. If these thin spots align with the die edges, they directly cause tearing—statistics show that 65% of total tearing in 6μm material stems from this issue.

This observation further confirms the advantages of 6.35μm over 6μm in blanking for stress dispersion.

(4) Poor Process Adaptability: Die Clearance Mismatch

Another critical limitation of 6μm material is its poor process adaptability, particularly regarding die clearance. The optimal blanking clearance for small-pouch packaging is 10%-15% of the material’s thickness. For 6μm material, this translates to a narrow range of 0.6-0.9μm.

In real-world production, Jednakże, the machining accuracy of blanking dies is typically only ±0.5μm. This discrepancy leads to frequent clearance deviation.

When clearance is insufficient (<0.6um), 6μm material is squeezed into “extrusion deformation”, creating raised burrs with lengths of 0.2-0.3mm.

When clearance is excessive (>0.9um), the fracture surface of 6μm material is pulled apart, forming serrated burrs and raising the tearing rate to 15%—a sharp contrast to 6.35μm material’s 8% tearing rate under the same conditions.

This comparison clearly demonstrates the advantages of 6.35μm over 6μm in blanking: its wider clearance adaptation range reduces sensitivity to die machining errors.

3. Mechanism of 6.35μm Material Improving Blanking Yield

6.35μm material leverages its 0.35μm thickness increment to improve blanking yield through three interrelated mechanisms. Each of these mechanisms directly reflects the advantages of 6.35μm over 6μm in blanking.

(1) Mechanical Property Enhancement

First and foremost, the most impactful advantage of 6.35μm material is its targeted mechanical optimization, which compensates for the inherent weaknesses of 6μm material:

From a mechanical perspective, the thicker cross-section of 6.35μm material (5.8% larger than that of 6μm) reduces the shear stress borne per unit area, thus avoiding die-induced extrusion deformation.

Dodatkowo, its thicker aluminum layer acts as a “stress buffer”, dispersing blanking stress evenly across the material and lowering the risk of tearing. This stress dispersion and load-bearing enhancement form the mechanical essence of the advantages of 6.35μm over 6μm in blanking.

(2) Stress Distribution Optimization

Beyond mechanical enhancement, 6.35μm material also excels at optimizing stress distribution. Its ±3% thickness deviation (compared to 6μm’s ±5%) minimizes thickness fluctuations after compounding.

This uniformity directly reduces stress concentration: the stress concentration factor at thin spots drops from 1.8 (in 6μm) Do 1.4 (in 6.35μm), and defects caused by thin spots fall from 65% Do 30%.

Ponadto, 6.35μm material has better die clearance adaptability. Its optimal clearance range (0.635-0.95um) fits within the standard machining accuracy of dies (±0.5μm), resulting in a deviation rate of only 15%—far lower than 6μm material’s 35%.

When clearance is properly matched, 6.35μm material achieves “neat shear fracture”, with burr lengths ≤0.1mm—fully meeting the requirements of GB/T 18454. This result underscores the advantages of 6.35μm over 6μm in blanking for process compatibility.

(3) Expanded Blanking Process Window

The third key mechanism is the expanded blanking process window of 6.35μm material, which reduces sensitivity to parameter fluctuations—a critical advantage for mass production.

For blanking speed, 6μm material’s safe operating range is a narrow 100-150mm/s (tearing risk rises sharply outside this range). W przeciwieństwie, 6.35μm material extends this range to 80-200mm/s, offering greater flexibility for adjusting production line speed to match order volume.

For blanking pressure, 6μm material requires strict control between 0.8-1.0MPa (tearing rates rise beyond 1.0MPa). 6.35μm material, Jednakże, tolerates pressures from 0.7-1.2MPa, which mitigates the impact of minor air pressure fluctuations in pneumatic systems.

For die temperature, 6μm material softens when temperatures exceed 40℃ (causing burrs). 6.35μm material’s thicker PE layer dissipates heat more slowly, allowing the die temperature upper limit to be raised to 45℃—this reduces the impact of ambient temperature fluctuations in workshops.

4. Experimental Verification: Yield Comparison

To empirically validate the advantages of 6.35μm over 6μm in blanking, a leading enterprise specializing in small-pouch nut packaging conducted a controlled experiment.

Test conditions were standardized to simulate real production: blanking specification was 50mm×30mm pouches, equipment used was a high-speed rotary die-cutter, and process parameters were set to industry norms (120mm/s speed, 0.9MPa pressure, 40℃ die temperature). A total of 10,000 samples were tested for each material.

(1) Blanking Defect Rate Comparison

Breaking down the defect data, clear differences emerge between the two materials:

This data confirms the advantages of 6.35μm over 6μm in blanking: 6.35μm material reduces total defects by 66.2%, thanks to its enhanced mechanical strength and improved stress control.

(2) Impact on Subsequent Heat-Sealing

Beyond blanking defects themselves, the experiment also assessed how these defects affect downstream heat-sealing—a key indicator of final product quality.

6μm material’s 18.5% heat-seal failure rate (defined as oxygen transmission >0.3cm³/(m²·24h·atm)) stems directly from burrs disrupting adhesive layer adhesion.

In sharp contrast, 6.35μm material’s heat-seal failure rate is only 4.2%. Its smooth blanked edges ensure even adhesive bonding, with oxygen transmission rates stable at 0.2-0.25cm³/(m²·24h·atm).

This result demonstrates that the advantages of 6.35μm over 6μm in blanking extend beyond the blanking process, improving the reliability of subsequent manufacturing steps.

(3) Full-Process Yield Calculation

Wreszcie, to quantify the full impact on production efficiency, yield was calculated using the standard formula for small-pouch food packaging:

Yield = (1 – blanking defect rate) × (1 – heat-seal failure rate) × (1 – inspection rejection rate)

Inspection rejection (caused by minor appearance defects) was ≤1% for both materials, so it was excluded from calculations to focus on core process impacts.

This represents a 38.9% yield improvement, providing data-driven proof of the advantages of 6.35μm over 6μm in blanking for boosting production efficiency.

5. Economic Trade-Off: 6.35μm vs. 6um

At first glance, 6.35μm material may seem less cost-effective: its raw material cost is 8%-10% higher than 6μm material (1.2 RMB/m² vs. 6μm’s 1.1 RMB/m²). Jednakże, the yield improvement driven by the advantages of 6.35μm over 6μm in blanking ultimately offsets this cost premium.

To illustrate this, we analyzed annual costs for a production scale of 100 million small-pouch nut packages (each requiring 0.002m² of material):

(1) Annual Cost Breakdown

(2) Core Economic Conclusions

From this cost breakdown, key conclusions emerge:

6.35μm material’s total annual cost is slightly lower (-12.5k RMB) than 6μm material, despite its higher raw material cost.

Ponadto, the yield improvement from the advantages of 6.35μm over 6um in blanking boosts production capacity: z 629,000 pieces/day (for 6μm) Do 874,000 pieces/day (for 6.35μm). This allows manufacturers to meet peak-season demand without investing in additional equipment.

Dodatkowo, 6.35μm material reduces annual scrap by 38.1 million pieces (equivalent to 7.62 mnóstwo), aligning with global sustainability goals and potentially lowering regulatory compliance costs.

These factors collectively confirm that 6.35μm material is economically feasible—further validating the advantages of 6.35μm over 6μm in blanking.

6. Wniosek: 6.35μm Is the Optimal Solution

W podsumowaniu, switching from 6μm to 6.35μm material significantly improves blanking yield for small-pouch food packaging, with the advantages of 6.35μm over 6μm in blanking serving as the core driver.

Pierwszy, performance adaptation: 6.35μm material’s 0.35μm thickness increment enhances shear and tear resistance, optimizes stress distribution, and cuts blanking defects from 26.0% Do 8.8%.

Drugi, process tolerance: its wider process window reduces sensitivity to fluctuations in die clearance, speed, and pressure, stabilizing production lines.

Third, economic feasibility: the 38.9% yield improvement offsets raw material costs, resulting in lower total annual costs and higher production capacity.

Fourth, standard compliance: 6.35μm material meets the strict requirements of GB/T 18454 and GB/T 31985—with burrs ≤0.1mm and post-heat-seal oxygen transmission ≤0.25cm³/(m²·24h·atm).

Looking ahead, for high-precision micro-pouches (NP., 5mm×10mm seasoning packets), 6.35μm material can be paired with “micro-clearance dies” (0.5-0.8um) to maximize yield (targeting ≥95%).

This combination will drive the small-pouch food packaging industry toward a future defined by “high precision, low loss, i zrównoważony rozwój”.