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The role of die wrapping film in plate heat exchanger

Release time:

2025-03-12

In the pressing process of plate heat exchanger plates, wrapping film (or using protective film) is the key process optimization measure, the main purpose is to improve the molding quality, extend the die life and reduce the production cost.

1.Protect the mold surface, reduce wear

Reduce direct friction between metals

Plate materials are mostly stainless steel, titanium alloy and other high-hardness metals, stamping and die steel (such as Cr12MoV) severe friction will lead to scratches on the die surface. Wrapping film (such as 0.05mm thick polyethylene film) can form a physical isolation layer, reduce the friction coefficient (from 0.15 to less than 0.05), and extend the service life of the mold by 30% to 50%.

Prevent material from sticking

When high temperature stamping (titanium alloy needs to be heated to 600~800 ° C), the metal is easy to micro-weld with the mold (cold welding). The film can block the contact surface, avoid adhesion, and reduce the frequency of mold repair.

2. Optimize the surface quality of the plate

Eliminate scratches and indentations

Direct stamping may leave scratches on the surface of the plate due to tiny burrs in the mold (depth > 5μm will affect the tightness). The film can buffer the pressure distribution and ensure the surface roughness of the plate ≤Ra 0.8μm.

Control oxidation and pollution

Stainless steel exposed to air during stamping tends to form an oxide (Fe₃O₄). Wrap the film to cut off oxygen, reduce the thickness of the oxide layer (from 2~3μm to < 0.5μm), and reduce the cost of subsequent pickling.

3. Improve material flow and molding accuracy

Lubrication extension

Film materials, such as PTFE-coated films, act as solid lubricants to promote uniform metal flow in the mold cavity, reducing the risk of cracking (especially when the deep draw ratio is > 2.0).

Stress distribution optimization

The film can disperse the local stress concentration to prevent corrugations or tears during the molding process of the corrugated sheet. The experiment shows that the qualified rate of forming can be increased from 85% to 98%.

4. Balance between process cost and efficiency

The traditional lubricant process was compared

The lubrication effect is uniform without residue, the friction coefficient is stable and easy to distribute unevenly, requiring frequent spraying

Subsequent cleaning does not need to be cleaned, directly into the next process requires alkali washing/ultrasonic cleaning, time-consuming and energy consuming

Environmental protection no VOC emissions, film material can be recycled containing chemical solvents, high processing costs

The comprehensive cost is reduced by 15%~20%

5. Film wrapping material selection and parameters

Film type

Polyethylene (PE) film: thickness 0.03~0.1mm, low cost, suitable for room temperature stamping.

Polytetrafluoroethylene (PTFE) film: temperature resistance 260℃, including lubricating coating, suitable for high temperature stamping.

Composite ceramic film: excellent wear resistance, used in titanium alloy and other difficult materials.

Process parameter

Tension control: The film material should cover the mold surface with a uniform tension of 5~10N/m² to avoid wrinkles.

Replacement cycle: every stamping 500~1000 times to replace the film (depending on the hardness of the material).

6. Suggestions on application scenarios

Recommended wrap:

High precision corrugated sheet (e.g. Herringbone/diagonal corrugated)

Titanium alloy, Hastelloy and other difficult to form materials

Nuclear/aerospace grade products requiring zero surface defects

No film:

Low precision flat stamping

Short term small batch production

Summary: The film wrapping process significantly improves the molding quality and production efficiency of plate heat exchangers through physical isolation and lubrication optimization, especially for high-end manufacturing scenarios. Enterprises need to reasonably select film types and process parameters according to material characteristics, production scale and cost budget.