1. Manufacturing process
The metal base or internal support of a steering wheel is a skeleton made of any of these strong but light metals: magnesium, aluminium or steel. Once the skeleton is made, the rest of the components are assembled.
To start assembly, a robot first installs the horn system. Right after, the skeleton is covered with a very durable, soft foam material, usually polyurethane (PU).
Originally, these skeletons were lined with wood, which, over time, has been replaced by plastics. Plastic materials reduce costs and, moreover, wood is a material that can split and cause injury in accidents.
To form polyurethane foam, a process called injection molding is performed. When the two chemicals that make up polyurethane (flexible, full-skin polyether polyol and MDI-type isocyanate) are mixed, they react and an expanding foam is produced. The reaction takes place inside a mold and this dense foam will take on a specific steering wheel shape.
Before injecting the polyurethane, the mold is covered with a release agent so that the foam will not stick on the mold. Also, it is sprayed with protective paint that dyes the foam in the required colour, in most cases black. The paint protects the foam against wear and damage from UV rays, although its use is optional (there are manufacturers that do not paint the foam).
The injection molding process leaves an excess of polyurethane on the flywheel, so the next step is to trim it. Steering wheels using flexible full-skin polyurethane foams have a soft feel and can be produced in a good variety of surface textures and colours.
Once the excess PU has been trimmed, it is time to install the internal components. Switches, which control the features operable from the steering wheel, are assembled into a unit called a wire loom. First the loom is connected to the switches, it is installed on the steering wheel and then a verification that everything works correctly is performed. If this is the case, the assembly is marked to show that it passes this stage of quality control.
While the basics are the same, the features vary from model to model in final adjustments. High-end steering wheels can be leather wrapped and often have additional switch controls for the audio system and for hands-free mobile phone use.
2. The mold release agent
Characteristics
Depending on the process, the release agent to be used will be different:
As we saw previously, the manufacture of the foam body can be done in three ways:
- PU foam steering wheel without painting.
- PU foam steering wheel with ‘in-mold coating’ painting inside the mold.
- Painted PU foam steering wheel with leather or textile covering.
Release agents for Integral Skin Polyurethane Foam or PU ISF (Integral Skin Foam) are specially formulated to produce a mat, uniform surface finish that can then be easily painted.
Internal mold coatings are used to colour the ISF and produce an aesthetically pleasing durable finish. This process also requires a release agent to remove the piece from the mold. ISF is generally mass pigmented with a colour similar to the coating dosage units. This process allows you to change the colour in each take, although it is cheaper to work on colour batches.
Water-based release agents are increasingly common, whereas less and less solvent-based ones are seen.
In addition, there may be quality controls for UV rays and abrasion. The release agent will have to pass these controls.
3. Concentrol range
Release agents
Working with Concentrol release agents provides the manufacturer with the following benefits:
➔ Good mold release that offers superior performance in the manufacturing process.
➔ Provide appropriate gloss / matte and appearance.
➔ Free of superficial defects like ‘pin holes’ and white spots, among others.
➔ Good compatibility for subsequent painting.
➔ Compatible with touch technologies on the steering wheel.
In addition to offering these benefits, our release agents are capable of solving different possible problems: the formation of too much ‘build up’, white spots or ‘white blooming’, small holes or ‘pin holes’ or difficult adherence of leather to the steering wheel.
At Concentrol we have different types of release agents: water-based and solvent-based. Both ready-to-use concentrates and concentrates to dilute, with a matte or glossy finish.
Other products
In addition, we have other products such as stabilizers: the CONCENTROL STB PU® range improves the emulsification of the system components, offering sufficient stabilization in the foam expansion process, in addition to controlling the size and distribution of cells. And the range of mold cleaners allows easy cleaning of the molds after long work cycles.
