The JetPreg system developed by Italy’s Cannon comprises a set of solutions for the use of industrial spray foams, which are becoming increasingly popular for the inexpensive production of lightweight composites.
A wide range of products can be produced from a corrugated paper honeycomb lined on both sides with sheets of a nonwoven glass tissue and impregnated with a fast-reacting polyurethane formulation before being immediately clamped to shape in a press.
Typical lightweight parts obtainable with these structures include automotive trunk load floors, parcel shelves, sun shades and headliners.
Chemical suppliers are developing faster formulations, Cannon reports, making an appropriate range of metering and mixing devices necessary to process them efficiently in mass production.
The ability to very evenly distribute fast-reacting PUR formulations over the entire surface of a large mould prior to the clamp closing operation – rather than forcing it into a closed mould by means of high-pressure injection – allows for significant advantages, including:
- There is no resistance to overcome a flow of liquid chemicals generated by the reinforcement in a closed mould, so the pressure needed to maintain the closed polymerisation press is much lower than that required using a classic high-pressure injection method. This results in simpler clamping equipment which is less expensive to buy and to operate.
- The polyurethane foam is applied with an optimum distribution of densities, only where it is required, for significant raw material savings.
- The application of the foam can be run outside the press, while another part is being polymerised, for shorter cycle times.
Cannon’s JetPreg system has a very efficient mixing head, the Cannon LS10, which provides the performances required by the most recent formulations. Its design is derived from the famous FPL model, the L-shaped mixing head patented by Cannon in 1979.
Advantages of this design include:
- The totally airless distribution of chemicals which provides a neat flow of pulverised formulation, totally free from mist. The effect on the working environment is considerable – moulds, robots, floors and the surrounding equipment stay clean much longer and there is a reduced need for fumigation.
- The spray pattern is characterised by a regular, triangular, 2D shape that distributes the chemicals precisely where they are required. This translates into a lower number of passes to cover a large mould, with much better distribution of densities, possible deposition of more material only where it is desired and an overall gain in cycle time that can be quantified at around 20%.
- The dosing machine and the LS10 mixing head can work with the same set of injectors from 30 to 300 g/s. A very fast sequence of a few passes, executed at high output, for example, covers the entire surface of a luggage compartment floor for a large car with a part-to-part cycle as short as only 40 seconds.
- Customers using different chemical formulations (normal or filled with mineral charges) can use the same standard configuration of Cannon equipment since the parts in contact with the polyol side are thermally hardened and treated against abrasion.
- The simplified design of the mixing head allows a very compact construction, with fewer hydraulic pipes, suitable for an automated application using commercial robots of medium-to-small size, that are not capital-intensive to buy and maintain.
Numerous automotive parts manufacturers in Europe, China and the USA, are now using the latest configuration of Cannon JetPreg solutions to mass-produce such polyurethane reinforced, lightweight structures.