Closed Molding Blog

John Moore from JHM Technologies, Inc. goes over some of the key elements you need to pay attention to when designing tooling for RTM, LRTM, VARTM (RSB), & HP-RTM.

Weight to strength ratio along with its aesthetic appearance has always made carbon fiber an attractive material choice. However due to it's excessive startup costs and molding complexities it has been out of reach for many, until now!

MTI® hose – "As close to Fire and Forget as it gets for VARTM" The MTI® hose is a spiral tube with an outer jacket that allows for resin to be stopped at the edge of the tube by the barrier jacket, yet air can still pass by.

In the late 90's there were two innovative tooling methods to address the shortcomings of "soft" FRP Tooling as used for the "RTM" molding process at that time.

The MTI hose offers a practical solution to voids common to the vacuum infusion process. Using MTI hose in place of standard spiral tube for the evacuation venting in vacuum infusion process gives unprecedented void free results.

The growth in closed molding continues with the low pressure molding processes of LRTM and Vacuum infusion (RSB) leading the industry away from open molding. The days of using nylon bag film and butyl tacky tape is all but gone with the advancements made using reusable silicone bags (RSB).

The key to repeatable molding process control in a RTM or LRTM tool is to have ACCURATE cavity thickness calibration. Most obvious consideration one would normally make is to use sheetwax of the same thickness desired for the final part thickness.

GAIN THE CLOSED MOLDING KNOWLEDGE – Eliminate the GUESSING ON THE BEST CLOSED MOLDING PROCESS The KEY to success in Closed Molding is in the Tooling and the Operator Training –

Quite often we are sent photos or actual parts to determine root cause and solution for prevention of various part defects. In this example, a base seat of a chair was sent which exhibits gel-coat breaking away exposing a void beneath.