Tooling goes soft

A soft tooling technology for resin transfer moulding is spelling success for a number of manufacturers.

Important innovations are distinguished by their broad impact on process improvement, and a new soft tooling technology for Resin Transfer Moulding, pioneered by UK based Plastech TT, is doing just that.

RTM is generally seen as superior to open moulding for the controlled production of multiple composite parts, but the cost of matched metal tooling, long regarded as essential, has prohibited many manufacturers from using it.

However, Plastech claims that its MIT (multiple insert technology) process combines the best advances in tooling with automated RTM injection equipment.

According to Cincinnati Fiberglass of Ohio, the process has been key to producing more, higher quality parts at a lower cost, while reducing VOCs and improving working conditions for employees.

Plastech says its thin, dimensionally stable MIT `skins’, which it produces from a master pattern, are critical to the process; making it possible to gel coat and load glass into several moulds offline, and at optimum temperature, eliminating downtime in the moulding cycle.

Jeff Burgess, production manager for Cincinnati Fiberglass, claims that multiple insert tooling enables the company to cycle its presses quicker by taking advantage of the out-of-press operations available with MIT. Offline gelcoating has also reduced the pinholing that used to occur when gel coat was applied to online moulds that were too warm.

Manufacturers accustomed to metal tooling have voiced concerns about mould life and mould maintenance. However, while composite tooling does not have the life span of steel tooling, the low cost and easy reproducibility of MIT `skins’ compensates for the cost of mould replacements. Mould maintenance comes into question because it is generally more difficult to release composite parts from composite tools rather than from metal mould surfaces. This problem is remedied by selection of a proper mould release.

Cincinnati Fiberglass selected XTEND, a proprietary, solvent-based semi-permanent mould release manufactured by AXEL Plastics that requires no mould sealer and resists styrene buildup. Burgess reports that composite moulds coated with XTEND are stripped only after 80-100 parts are moulded.

AXEL is also working on internal mould releases specifically for RTM. These are being employed to improve cavity fill and wetting of reinforcement, with new development centred on reducing scumming.

AXEL Tel: +1 718 672 8300; Fax: +1 718 565 7447

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