Several Common Processes In Automotive Interior Manufacturing

The automotive industry has always been at the forefront of innovation, especially when it comes to the interiors that define the comfort and aesthetics of a vehicle. From the soft touch of a dashboard to the intricate designs on door panels, the manufacturing processes behind these components are both complex and fascinating. Today, we will introduce several common processes in automotive interior manufacturing.

Slush Molding

What is Slush Molding?

Slush molding is a specialized technique predominantly utilized for crafting soft dashboards and door panel skins in automotive interiors. This method has its roots in Japan and was introduced to China only in the early 21st century. Initially embraced by a select few joint ventures, it has since gained popularity among Chinese independent brands, underscoring its significance in automotive interior manufacturing.

Advantages and Disadvantages of Slush Molding


  • Versatile Raw Material Selection: The slush molding process is adaptable, drawing from a broad spectrum of raw materials, which enhances the production flexibility.
  • Economical Approach: The materials employed are not only abundant but also cost-effective, making the method budget-friendly.
  • Rich Design Heritage: Leveraging years of expertise, manufacturers can produce designs with clear, visually appealing leather patterns. This design consistency ensures that every product aligns with the high standards of automotive interior fabrication.
  • Product Durability: The end products are characterized by their excellent elasticity, minimal shrinkage rates, and the ability to incorporate intricate design elements.


  • Mold Investment Considerations: The initial outlay for molds can be substantial, and their durability is somewhat limited, typically ensuring quality for just 20,000 to 30,000 iterations.
  • Equipment Expenditure: The machinery integral to slush molding demands a significant capital investment.
  • Maintenance Requirements: Regular cleaning of molds is imperative, leading to extended auxiliary work periods, which can potentially impede the overall production efficiency.

Understanding the details of slush molding is crucial for manufacturers and automotive interior fabricators. This knowledge allows them to find the right balance between quality and cost in the ever-changing world of automotive interior production.

PU Spraying (Polyurethane)

Introduction to PU Spraying

In recent years, PU (Polyurethane) spraying has emerged as a rapidly advancing skin molding technology, primarily employed for crafting dashboard skins and protective panel skins in automotive interiors. This innovative method underscores the evolving dynamics of automotive interior manufacturing, offering a fresh perspective on material application.

The PU Spraying Process

The PU spraying technique involves a series of steps:

  1. Initially, a mold release agent is sprayed onto the surface of the skin molding mold.
  2. Subsequently, an internal paint is sprayed onto the mold. Depending on the product’s requirements, this paint can vary in color.
  3. Liquid PU material is then sprayed onto the mold. The thickness of this skin layer can be precisely controlled using automated spraying equipment.
  4. The final step involves cooling and demolding, ensuring the formed skin retains its shape and design.

Advantages of PU Spraying Over Slush Molding

While both slush molding and PU spraying are pivotal in the manufacturing of soft dashboard skins, PU spraying boasts several advantages over its counterpart:

  • Dual-Color Capabilities: PU spraying can achieve dual-color dashboard surfaces, offering greater flexibility in design and aesthetics.
  • Simplified Equipment: The machinery required for PU spraying is relatively straightforward, leading to significant energy savings.
  • Cost-Effective Material: Especially in recent years, the price drop in powdered PU material has made it a competitive alternative. The recyclable PU skin prices can now potentially rival traditional PVC skins, marking a significant shift in material preference for automotive interior manufacturers.

Automotive interior manufacturers can add PU spraying to their techniques. Doing so lets them enjoy its advantages and stay ahead in innovative design and efficient production.

In-Mold Decoration (IMD)

Concept and Applications of IMD

In-mold decoration (IMD) is a technique where decoration is integrated with the molding process. By decorating plastic components during molding, it eliminates the need for post-molding decoration, reduces on-hand inventory, and minimizes additional operational steps, leading to significant cost savings. This method is predominantly used for dashboards, air conditioning panels, interior components, headlight casings, logos, and more. The decorative film used typically has a thickness of about 0.5mm. This film can be designed with various patterns and finishes, such as wood grain, metallic brush strokes, aluminum, carbon fiber, glossy, and matte finishes. Thanks to the protective PET layer, the film boasts excellent scratch resistance and corrosion resistance, ensuring the design remains intact even after prolonged use.

HThe Molding Process

Before the mold closes, a film with the desired pattern is attached to the surface of the injection mold cavity. Melted plastic, usually a combination of PC and ABS, is then injected into the mold, fusing the film and plastic together. This integration ensures the design is embedded within the product, enhancing its aesthetic appeal.

Advantages and Disadvantages


  1. Integrated molding simplifies the process, reducing production/inventory costs and work time, shortening the product manufacturing cycle, and boosting production efficiency.
  2. The reliability tests for this method are of the highest industry standards, ensuring product stability and durability.
  3. High automation in production guarantees consistent high-quality output.
  4. The use of automatic printing and eco-friendly inks aligns with environmental standards.
  5. Multi-color printing options, such as wood grain, carbon fiber, and metallic hues, allow for simultaneous coloring of surface textures and indentations. For transparent components, a semi-transparent effect can be achieved, offering a three-dimensional texture.
  6. The surface undergoes a hardening (HardCoat) treatment, reaching a pencil hardness of up to 3H, which ensures wear resistance and aesthetic appeal.


The printed pattern layer on the product’s surface is only a few micrometers thick. Over time, this layer can wear off or fade, compromising the product’s appearance. Additionally, one of the challenges with IMD technology is the longer development cycle for new products, higher development costs, and the inability to flexibly change pattern colors in small batches.

In the realm of automotive interior manufacturing, the IMD technique offers a blend of functionality and aesthetics, allowing manufacturers to produce components that are not only functional but also visually appealing.

In-Mold Lamination (INS)

The Principle Behind In-Mold Lamination (INS)

In-mold lamination, abbreviated as INS, involves pre-attaching a thin film to the molding tool using high pressure. This film takes on the desired shape of the product’s exterior surface. Once shaped and trimmed, the film is placed into the product’s injection mold, where it is combined with molten plastic during the injection process. This method ensures that the film seamlessly integrates with the plastic component, offering a refined finish.

Advantages Over In-Mold Decoration (IMD)

Compared to the IMD technique, the most significant advantage of INS is its ability to produce larger surface stretch decorations. While the process might require additional tools for vacuum absorption and cutting, making it somewhat more intricate and raising the production cost per unit, INS can be directly applied using standard injection molding machines. This eliminates the need for specialized film transfer positioning devices. The two techniques, when juxtaposed, offer distinct surface effects, as can be seen in the comparison below (Note: The original content mentions a diagram, which isn’t provided here).

A Leap in Automotive Interior and Exterior Design

The emergence of in-mold decoration and in-mold lamination technologies marks a significant advancement in the design of color and texture for automotive interiors and exteriors. These methods have entirely surpassed the limitations of traditional water transfer printing techniques in terms of product color and texture. The combination of different color textures on the product surface can cater to the personalized demands of various customer groups. By simply switching between different films, manufacturers can achieve diverse designs. When compared to traditional methods, these innovative techniques not only enhance production efficiency but also promote eco-friendly processes and result in products with higher corrosion resistance.

The world of automotive interior manufacturing is constantly changing. Techniques like INS are leading to more detailed and custom designs, meeting today’s consumer demand for uniqueness and quality.

Water-Assisted Injection Molding

Origins and Global Adoption

Water-Assisted Injection Molding (WAIM or WIT) traces its roots back to the early 21st century in Germany and has gradually found its application across the globe. As a counterpart to Gas-Assisted Injection Molding (GIT), the continuous maturation of this technology promises a broader application in the future. Notably, many successful applications can now be observed in automotive door handles.

Basic Principle of Water-Assisted Injection Molding

The fundamental principle of WAIM involves injecting polymer melt into the mold cavity. Water is then introduced into this melt, naturally flowing towards the low-pressure areas of the part where resistance is minimal. As the water flows within the part, it displaces the material, hollowing out thick-walled sections and forming a hollow component. The displaced material is then used to fill the remaining parts of the component. Once the filling process is complete, water continues to exert holding pressure, addressing the volume shrinkage issues during the cooling process. After the mold cools down, the water is expelled, and the part is retrieved.

Comparing WAIM to Gas-Assisted Injection Molding

When juxtaposed with Gas-Assisted Injection Molding, WAIM offers several advantages. Not only can it reduce or eliminate warping and deformation, but it also facilitates the production of products with thinner, more uniform walls and smoother internal surfaces. This helps in avoiding sink marks, conserving material, and reducing internal stresses in the product. Moreover, due to water having a thermal conductivity 40 times that of N2, in addition to the standard cooling mold, water injection also cools the interior of the plastic product. As a result, compared to gas, the cooling time with water can be reduced by up to 70%, allowing products to reach the demolding temperature much faster. Concurrently, water is significantly more cost-effective than N2.

Challenges in WAIM

Despite its advantages, WAIM requires precise control. If the initial amount of injected melt is too little, water might penetrate the melt and enter the mold cavity. The pressure of the water injection must surpass the melt’s pressure to push the melt to the mold’s extremities. Injection molding becomes unfeasible when there are high surface quality requirements.

In automotive interior manufacturing, techniques like WAIM are pushing the boundaries, offering enhanced efficiency, reduced costs, and superior product quality. As manufacturers continue to refine this process, the potential for further innovation remains vast.

Low-Pressure Injection Molding

Understanding Low-Pressure Injection Molding

Low-pressure injection molding is an encapsulation technique that involves injecting thermoplastic material (Check thermoplastic manufacturing) into a mold at an exceptionally low molding pressure, allowing it to solidify rapidly. This method boasts features like insulation, temperature resistance, impact resistance, vibration reduction, moisture prevention, waterproofing, dustproofing, and resistance to chemical corrosion. With its superior sealing properties and excellent physicochemical performance, it offers robust protection to electronic components.

Molding Process and Applications

The process begins by placing the skin material into the mold. Following this, the molten plastic is injected into the enclosed mold cavity through the force exerted by a screw. Once injected, the material solidifies, resulting in the final product. The skin material used in low-pressure injection molding can be fabric or PVC fabric. Currently, this technology has found extensive applications in the production of automotive door panels, pillar panels, and wrap-around rack panels.

Advantages Over Traditional Processes

When compared to traditional wrapping processes, low-pressure injection molding offers several distinct advantages:

  1. The skin material and the plastic base material are fused together in low-pressure injection molding, eliminating the possibility of detachment.
  2. The absence of the adhesive application process, which is required in traditional wrapping, makes low-pressure injection molding more environmentally friendly.
  3. The internal structure of low-pressure dual-layer injection molded parts can be designed freely. Its surface design flexibility surpasses that of wrapping processes, resulting in clearer and more robust design features.
  4. The production efficiency of low-pressure injection molding is notably higher.

Given these characteristics, low-pressure injection molding has become a preferred method in automotive interior manufacturing, especially for producing door panels, pillar panels, and wrap-around rack panels. This innovative process not only ensures product durability but also aligns with the industry’s push toward eco-friendly manufacturing solutions.

Conclusion: The Expansive Horizon of Automotive Interior Manufacturing”

The processes discussed above represent just a fraction of the contemporary techniques employed in automotive interior manufacturing. Beyond these, there are numerous other methods, including negative mold lamination, genuine leather wrapping, In-Mold Labeling (IML), and many more. As the automotive industry continues to evolve, so too will the techniques and innovations that drive the production of high-quality, aesthetically pleasing, and functional vehicle interiors. The journey of discovery and improvement is ceaseless, ensuring that the future of automotive interior manufacturing remains bright and promising.

Engineering Excellence in Every Detail

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