Main Manufacturing Processes of Custom Carbon Fiber Steering Wheels

There are some different ways to manufacture custom carbon fiber steering wheels but here at donfoo, we usually utilize the two main manufacturing processes known as carbon fiber autoclave molding process and carbon fiber skinning. In this post, we’ll explore the whole manufacturing process of carbon fiber steering wheels from the raw material to the finished product.

Carbon Fiber autoclave molding process

Autoclave molding is a composite manufacturing process that utilizes a pressurized chamber to cure resin-impregnated materials under heat and pressure. The detailed process flow as follows:

1. Raw Material Preparation

1) Pre-impregnated Materials: The first step we need to select unidirectional or woven carbon fiber cloth. Unidirectional carbon fiber cloth has all fibers aligned in the same direction, maximizing strength and stiffness in that specific orientation. However, it can be more brittle and less damage-tolerant than woven fabrics.

on the other hands, Woven carbon fiber cloth has fibers interlaced in a pattern, which provides better impact resistance and drapability. It also tends to have better impact resistance and damage tolerance due to the interlacing pattern.

Comparing with unidirectional fabrics, the crimping of fibers in the weave can slightly reduce the overall strength and stiffness in the woven carbon fiber cloth. And then pre-impregnate with epoxy resin or other thermosetting resins such as phenolic, polyurethane.

2) Mold preparation: The upper and lower molds(usually steel or aluminum molds) need to be processed with high precision. The surface of molds are polished and applied the release agents such as silicone oil, wax to remove from molds smoothly.

2. Cutting

1) Cutting: Cut the prepreg into sheets of specific sizes and angles according to the three-dimensional shape of the steering wheel. This process ensures the final products have the strength, stiffness and aesthetic properties.

2) Layup design: Adopt multi-layer stacking technology. Each layer of carbon fiber is staggered in all direction to enhance the isotropy, thus can improve mechanical properties and make the material suit for applications more where load is applied from various angles.

3. Pre-forming

1) Properly Lay the prepreg into the lower mold and align them with the design specifications. Smooth the prepreg from the center outwards to eliminate air bubbles or wrinkles. Gently compact the prepreg to ensure them adheres to the mold surface, but avoid excessive pressure that could distort the material.

2) Pre-compaction: Use a vacuum bag or cold pressing to expel air initially, making the fibers fit the mold surface closely. This process compacts the layers, removes trapped air, and optimizes the fiber-to-resin ratio, so the The quality of parts has been greatly improved.

4. Compression Molding

1) Mold closing: Align and close the upper and lower molds. Apply pressure (usually 5-20 MPa) and heat the temperature to 120–180℃ depended on the resin type.

2) Curing: Keep the temperature and pressure for 10-30 minutes to cure the resin. Curing time is up to the resin properties(Different resins have different chemical compositions and curing characteristics) and the physical dimensions of the cured object.

3) Key controls: Precisely control the heating rate to avoid the bubbles, at the same time control pressure uniformity to prevent fiber displacement as well as and other defects during manufacturing processes.

5. Demolding and post-treatment

1) Demolding: After curing, the temperature of the molded part should be lowed to below 60°C before using an ejection mechanism to release it from the mold. The molded part can be safely removed from the mold without damage at this temperature.

2) Trimming: Cut off burrs by waterjet or CNC (Computer Numerical Control)machines, and subsequently drill holes and polish the surface to achieve the finished products.

3) Painting: Spray a UV protective layer or matte/high-gloss varnish to improve wear resistance and aesthetics.

6. Quality Inspection

1) Visual inspection: uses vision, potentially aided by tools, to examine that products or systems are free from any faults or defects like delamination, bubbles, or cracks.

2) Dimensional inspection: Use a Coordinate Measuring Machine (CMM) to measure the dimensions and geometry of manufactured parts.

3) Mechanical testing: Utilize JIS and ASTM standards to do the torsion and impact testing for samples,ensuring meet design specifications and quality standards.

This process is mostly used for economical vehicles, focusing on cost control and durability.

Carbon Fiber Skinning

Skinning is the process of applying carbon fiber material to the surface of an existing steering wheel skeleton (usually metal or plastic) during molding. The detailed process flow as follows:

1. Prepare the steering wheel

The first step we prepare the steering wheels by stripping down any existing leather, plactic, alcantara and other materials. Remove oil stains and oxide layers from the skeleton surface, and roughen the surface (such as by sandblasting or sandpaper).

2.Reshape the steering wheel

Our custom carbon fiber steering wheels are shaped according to your request that come with a sporty look and more ergonomic feel on the hand grips.

3. Carbon Fiber Covering Molding

1) Method 1: Wet Wrapping. Cut arbon fiber cloth to fit the shape of the steering wheel, leaving edge allowances. Lay dry carbon fiber cloth layer by layer on the skeleton, and brush or spray resin impregnated uniformly. We offer many different carbon fiber materials such as regualr black twill carbon fiber and also offer other weave style carbon fiber such as honey comb, forged carbon, and more.

The prepared carbon fiber fabric is then applied to the steering wheel and pressed into place. Cure at room temperature for 2-5 days or accelerate curing by heating 4-8 hours at 60-80℃.

2) Method 2: Prepreg Wrapping. Cut the prepreg and directly wrap it around the skeleton, compacting between layers. Evacuate and heat 120-150℃ for curing, allowing the resin to flow and fill gaps spontaneously.

4. Trimming and Surface Treatment to the steering wheel

Cut off excess carbon fiber at the edges by using a waterjet or precision tools, and sand the joints until smooth. Use resin putty to fill bubbles or dents and perform local secondary curing. Sand with sandpaper, and finally polish to a mirror finish.

5. Coating Protection

Spray 2-3 layers of high-transparency polyurethane or UV-cured varnish to enhance wear resistance and gloss. Bake them for 30-60 minutes at 60-80℃ to cure the paint.

6.Finish the steering wheel

Proceed with adding the leather, Alcantara material or other materials for the grips after coating. Finally install necessary hardware and components such as the buttons, paddle shifter, and LED display If request.

7. Quality Inspection

1) Appearance check: Examine and ensure no bubbles, wrinkles, uneven resin, or scratches.
2) Adhesion test: Apply peeling force to separate the two materials and test the bonding strength between the carbon fiber layer and the skeleton.
3) Functionality test: Install and test its grip and then turn the steering wheel to check for any slippage or instability, especially at different steering angles.

This process is mostly used for Mid-luxury vehicles, focusing on comfort and luxury feelings.