Promising to, “Take you on journey of how to foam without release agent,” Frimo’s Dr-Ing Florian Meyer described a joint project with Kunststofftechnik Wiesmayer GmbH to develop a thermoplastic mould liner, called PURe Liner.
The aim is to eliminate the need to apply mould-release agents with reactive materials such as polyurethane and epoxy.
Release agents are a great bugbear in moulding PU but, as Meyer explained, “We need release agents because reactive plastics have a strong adhesion to steel.”
Release agents can be a semi-permanent layer, but many are waxes which must be applied before every shot and, “you get residues which have to be cleaned.” Recently, permanent treatments have been developed: “We have heard of miracle layers, and some are good solutions,” said Meyer, noting that plasma polymer layers work well, but can be costly.
Release-agent residue can also be difficult to remove completely from the components, causing problems for parts which have to be glued.
“While I think some release agents are able to offer solutions to these problems, costs, both one-time and recurrent costs, are high,” Meyer stressed.
Costs include that of the wax, of maintenance/ cleaning of the mould, of mould-spraying equipment, and also of ventilating the spraying area to protect workers, and remove any solvent.
PURe Liner is an injection-moulded plastic, which is a self-separating compound, which Frimo has evaluated in front-foaming, to prevent the foam sticking to mould, Meyer explained.
The PURe Liner stretches over all the cavity for open foaming, said Meyer, noting that it is easily exchangeable, in a few seconds.
Meyer said one liner can be last up to 500 cycles. A side effect is that the formable material offers good sealing, leading to an increase in process robustness.
Advantages of the method include lower costs, no need for cleaning, and no compliance needed for health & safety and environmental protection.
The liner allows a variety of surface structures, and the process is robust enough for high throughput, Meyer said.
Total investment costs are lower, Meyer said, citing a case study from a customer making front foaming armrests. This involved 6300 parts a day, and the customer saved a total ca €2 million, including €1.0 million rework.
PURe Liner costs are €230 000 for the initial investment and €250 000 for a service package.
Inventor Otto Wiesmayer gave examples to show process-related benefits of the PURe Liner, such as an armrest which showed the addvantage of excellent sealing, and could incorporate a decorative surface effect, or surface texture.
Large-area parts such as spray surface parts can also be made using a PURe Liner, Wiesmayer said.
A PURe Liner offers users a robust, large-batch process, with improved productivity and high part quality, he said. The system is already in use in mass production by several system suppliers in the automotive industry, and surpasses expectations, Wiesmayer said.
Wiesmayer, a Neustadt, Germany based operation, invested four years ago in the liner technology. “This is not a revolutionary idea,” Wiesmayer commented.
For new plants especially, the potential savings are high, Wiesmayer said, noting that for existing plants, the cost benefits may be less.
Frimo and Wiesmayer can also help with design of the geometry of components, so that seams, for example, are avoided.
Lotte, Germany-based Frimo makes moulds and can start making parts for qualification, as well as testing materials and foam systems. “Experience tells us that users quickly reach good part quality,” said Wiesmayer.
The BMW-3 series has an armrest made using a PURe Liner with a grained surface, to give a special structure.
The liner can also be used with an in-mould coating, as has been done for a part for the Golf convertible where the company wanted an homogenous surface, made by using PU coating in a PURe Liner, Wiesmayer explained.
