Accurate dosing of release agent

Have you ever seen cars with a nice ‘leather look’ dashboard? One of our customers in the automotive industry manufacturers these ‘skins’ that look like leather. These ‘skins’ are produced by spraying liquid - coloured polyurethane - into moulds. 

To allow an easy skin release from the mould, a release agent must be applied onto the mould surface. The amount of release agent is essential in this respect and must be perfectly dosed as it determines the quality and look & feel of the product. The ‘skin’ will remain adhered to the mould when too little agent is applied, whereas too much agent will give glossy spots on the skin.

The customer asked Bronkhorst for support in designing a dosing solution which can dose the release agent very accurate resulting in less production loss. Besides that, the offered dosing solution reduced the downtime necessary for calibration and maintenance significantly. 

Process solution

A Bronkhorst Coriolis mass flow controller (series mini CORI-FLOW M14) combined with a C5I valve forms the basis of the solution to accurately supply external release agent to the nickel mould surface. These compact devices are mounted next to the robot arm that sprays the agent by means of a spray nozzle. The robot arm moves along the surface of the mould, where the required amount of agent is sprayed homogeneously. This setup is being used for water based as well as solvent-based release agents.

This solution results in a stable flow, even with low flows of less than 5 grams per minute. Compared to the old solutions, the overall release agent application process stability has been improved, with respect to the colour and gloss of the manufactured car dashboard skin. Also, reproducibility is high, as the linear flow curves have the same output for all installations. After change of setpoint, the response time is excellent.