Thanks for the video, that "inflatable" flow channel is a very smart technique! What I don't quite understand is when and why you would prefer essentially lower fiber content of the LRTM process basically increasing resin consumption. Wouldn't it be better to use more fiber? I thought fiberglass is basically the same price as resin, but more fiber content increases toughness. Oh wait, if you don't use epoxy then the resin is of course cheaper. Never mind! :)
So, as I can understand, there is no way to produse a part of cloth reinforcement with high level ov compaction by LRTM technology, unless super precise layering and super acurate tooling; the only way to achieve a high level of compaction is to aply force on B-side? Correct me if I wrong. Thanks
The point made in the video is that to control the resin flow path, there needs to be fiber in contact with both the upper and lower mold sides in all areas of the cavity crossection. When there are two rigid halves, as such for a "RTM" or "LRTM" tool set, then the fiber must have enough "loft" to touch both sides. When using knitted fabrics this posses an issue, especially in areas of over lapping fiber. When using knitted fabrics alone it is often easier to use a vacuum infusion process utilizing a bag film or re-usable silicone bag. This then allows for the bag to be sympathetic to the changing fiber crossections while maintaining contact with the mold on one side and the bag on the other. When however, we are looking for speed of injection, using knitted fabrics, we can use a hybrid of the mold / process methods. In that case, we have a rigid "A" side with a re-usable silicone bag, then we calibrate a narrow gap over the silicone and build the typical semi rigid "LRTM" upper as the norm today of that tool build structure. In this case, we have the bag packing the fiber, yet with the "LRTM" upper preventing the bag from "ballooning" to an excess. The benefit of this is a bit of injection speed, and by keeping the laminate tightly packed to the "A" side resulting in minimal resin content, while not concerning with the overlapping fiber. This later tooling is normally cost prohibitive however, when you consider the LRTM mold is ~$350 per square foot of area, the bag adds another ~$50 per square foot to the tooling cost.
Thank You for such a grate explanation. That is something I was thinking about. But I wonder then HOW much engenering is it take to develop a process of production frames like TIME company makes. They use in house braided carbon fibre sleeves and wax plugs to lay on. Then they put assembly in mold and inject resin. BUT the resin to fibre ratio realy low (somewhere around 40%)
![Brief Overview of a LRTM Injection System - [6 of 9]](http://i.ytimg.com/vi/W8kFRlDLJm4/mqdefault.jpg)
![Demolding a LRTM Part - [9 of 9]](/img/n.gif)
Cheers for the video and all those pretty helpful information..
Thanks for the video, that "inflatable" flow channel is a very smart technique!
What I don't quite understand is when and why you would prefer essentially lower fiber content of the LRTM process basically increasing resin consumption. Wouldn't it be better to use more fiber? I thought fiberglass is basically the same price as resin, but more fiber content increases toughness.
Oh wait, if you don't use epoxy then the resin is of course cheaper. Never mind! :)
So, as I can understand, there is no way to produse a part of cloth reinforcement with high level ov compaction by LRTM technology, unless super precise layering and super acurate tooling; the only way to achieve a high level of compaction is to aply force on B-side? Correct me if I wrong.
Thanks
The point made in the video is that to control the resin flow path, there needs to be fiber in contact with both the upper and lower mold sides in all areas of the cavity crossection. When there are two rigid halves, as such for a "RTM" or "LRTM" tool set, then the fiber must have enough "loft" to touch both sides. When using knitted fabrics this posses an issue, especially in areas of over lapping fiber.
When using knitted fabrics alone it is often easier to use a vacuum infusion process utilizing a bag film or re-usable silicone bag. This then allows for the bag to be sympathetic to the changing fiber crossections while maintaining contact with the mold on one side and the bag on the other.
When however, we are looking for speed of injection, using knitted fabrics, we can use a hybrid of the mold / process methods. In that case, we have a rigid "A" side with a re-usable silicone bag, then we calibrate a narrow gap over the silicone and build the typical semi rigid "LRTM" upper as the norm today of that tool build structure. In this case, we have the bag packing the fiber, yet with the "LRTM" upper preventing the bag from "ballooning" to an excess. The benefit of this is a bit of injection speed, and by keeping the laminate tightly packed to the "A" side resulting in minimal resin content, while not concerning with the overlapping fiber.
This later tooling is normally cost prohibitive however, when you consider the LRTM mold is ~$350 per square foot of area, the bag adds another ~$50 per square foot to the tooling cost.
Thank You for such a grate explanation. That is something I was thinking about. But I wonder then HOW much engenering is it take to develop a process of production frames like TIME company makes. They use in house braided carbon fibre sleeves and wax plugs to lay on. Then they put assembly in mold and inject resin. BUT the resin to fibre ratio realy low (somewhere around 40%)
Oh god! Forgive me my english!..
What products are they molding?
highest end bicycle frames