Well you can see the results possible with MTI in a YouTube video. The uncutted video shows the demoulding of a carbon fiber part with a glossy finish right out of the mould.
There is also an [ame=“http://www.youtube.com/watch?v=R7OuvO1jZf4&feature=share&list=UUsPC12VbgXA3VP_quU7pgjQ”]animation video[/ame] which explains the advantages of the MTI hose in comparison with Vacuum infusion Process using the usual spiral hose.
Nevertheless I can tell you about my own experiences. First of all, the advantages of the MTI hose depend on which process you are currently using and the performance level you want to achieve. My own composite experience began with wet lay-up 10 years ago and went over to vacuum bagging and finally to vacuum infusion. But the sharp designed lines of the Fast Forward project forced me to review my previous production methods since they were characterized through more or less voids within the laminate and the surface. That causes a tremendous effort with sanding, filling the pinholes, priming etc… Especially with vaccuum bagging or vacuum infusion these voids are caused by entrapped air bubbles which have the chance to expand to maximum size in the vacuum athmospere. Pinholes arises since the resin can escape the mould cavity. Above all there is the risk of getting dryspots when the resin decides to flow through the spiral wrap into the catch pot instead of saturating the rest of the laminate. Particularly with complex designed moulds these risks are always evident. Through my internet researches I came across MTI and gave it a try.
What are the advantages of MTI:
The process is based on a hose which consists of a high-tech textile compound fabric supported by an internal spiral hose. The membrane is permeable to air but impermeable to resin which causes a kind of self-regulating effect which in turn influences two things:
- Resin can not escape the mould cavity and is forced to saturate the reinforcement fabric completely. The advantages are:
[ul]
[li]Minimized risk of getting dry spots[/li][li]Pin-hole free finish which reduces overall costs by avoiding post treatment (sanding, primer, paint particularly if you use an In-Mould coating)[/li][li]No need for complex calculations of resin flow[/li][li]Flexible positioning of the resin feed lines[/li][li]No more wasted resin[/li][li]The resin consumption can be calculated ecactly[/li][li]One can place the MTI hose on top of the laminate to defuse critical points[/li][li]One can adjust the amount of introduced resin to achieve optimum fiber volume fraction[/li][/ul]
2) It leads to an automatically adjusted system pressure. That means, when the resin has once covered the membrane completely it shuts the door to the vacuum pump. That mechanism leads to ambient pressure in the system which in turn leads to a collapse of possibly entrapped airbubbles. To keep a certain pressure within the system one can place the resin source below the mould cavity. One yard height differences results in 150mbar or 4,4 "HG which corresponds to the fiber opening forces. The advantage is a minimized impact from air bubbles which leads to a consistent high quality of the structural components which in turn results in higher resistance to dynamic loading.
The integrated spiral hose provides an effective airflow channel for maximum evacuation performance. This is evident even under difficult conditions including hulls and wind turbine blades and other extremely large or complex designed moulds. Also, the MTI hose is extremely easy to work with since it is flexible and pliable, enabling it to be routed along the profile of the most complex of parts.
What then are the disadvantages?
The material costs are higher in comparison with spiral hose and it is important to follow certain rules to get the best possible results (which actually is the same with other processes). One is that your vacuum system has to be airtight.
To summarize my experience. The MTI hose enables me to produce lightweight cosmetic cabon fiber parts with tremendously reduced overall costs.
Hope this summary answers your questions.
