JEC COMPOSITES MAGAZINE - Issue #50 - July/August 2009 - 32

FEATURE “RTM” The latest innovations to the LRTM moulding process The excitement continues with the growth of the Light RTM (LRTM) process around the world. In these uncertain economic times, the LRTM process is being redefined with heightened focus on cost reduction and ecological responsibility. LRTM injection systems which offer low-cost automation, thus eliminating the reliance on operator skills. JOHN H. MOORE, PRESIDENT, JHM TECHNOLOGIES, INC. Background Historically, the conventional RTM process relies on a central injection point with a “diverging” resin flow path towards the vents located at the outer extremities of the mould cavity. In contrast, the LRTM process takes advantage of a “converging” flow path beginning with a perimeter resin feed circumventing the mould cavity in a converging route to the vent located typically in the centre of the mould cavity. In addition, LRTM utilizes cavity vacuum which typically eliminates half of the atmosphere within the mould cavity prior to the injection process and is completed by a perimeter flange under high vacuum which holds the upper and lower mould halves together during injection and cure. The “converging” resin flow path combined with balanced cavity and clamping flange vacuum eliminate the primary challenge faced by the conventional RTM process, which is plagued with flowing resin that “race tracks” around the outer perimeter of the fibre, leaving behind excessive laminate voids and occasional dry fibre. In LRTM, the use of vacuum as a means to retain the mould halves eliminates the need for capital equipment such as presses or excessive mould structure and weight to counteract internal cavity pressure needed for conventional RTM. This has opened the door for moderate-size moulds to be handled by hand with one or two operators, making the LRTM process convenient and practical for even the small moulder. Even with a lighter LRTM tooling structure and the elimination of clamping presses, several challenges still remained to be overcome, as described below. ecent innovations in equipment, resin chemistry and mould building methods have elevated the LRTM process to a whole new level, one that not only offers a very practical moulding technology, but is now also being recognized as a “green” process. The “green” advantage does not only refer to the clear reduction in VOC emissions associated with the closed-mould LRTM process. Resin materials suppliers have released bio-based resin systems which are based on various soy bean formulations, such as Ashland Chemical’s Envirez™ resins. The new Envirez resins are proving to be ideal for the LRTM and vacuum infusion moulding processes, offering low viscosity, excellent wet-out of fibres, and enhanced surface finish. These resins cure well in ambient-temperature tooling or can be accelerated with temperature-condition tooling. Beyond resins there are solvent replacements such as Acrastrip™ which further the green advantage by eliminating acetone needed to flush injection equipment. Material suppliers have made enormous commitments to bringing in ecologically-responsible resins and now these efforts are bearing fruit in support of the LRTM and vacuum infusion processes worldwide. Efforts to conquer the process challenges of RTM and LRTM have been the focus of JHM Technologies (Fenton, Michigan, USA) since their inception in 1992. JHM Technologies has been recognized as one of the world leader in manufacturing and supply of state-of-the-art LRTM injection equipment, along with training classes on mould building and moulding process methods. Their development team is keenly focused on refining the LRTM process to enhance productivity and the quality of each moulding produced. They have developed a full line of R Refinements With these initial advantages of the LRTM process and moulds in play, the challenge of controlling the resin injection feed was enhanced since now the moulds are lighter in structure and there are no hydraulic presses to maintain closure. To meet this 32 jec composites magazine / No50 July-August 2009

JEC COMPOSITES MAGAZINE - Issue #50 - July/August 2009

Table of Contents for the Digital Edition of JEC COMPOSITES MAGAZINE - Issue #50 - July/August 2009