Critical LRTM Flange Details

[00:00] Hi, it's John Moore with JHM Technologies, and here today we're gonna talk about the

[00:05] critical details to the Lite RTM flange. Now, uh, we had our virtual school both yesterday and then the topic came up again today, uh, in talking about the details of the seal placements in relation to the flange width, and there's a lot of question around that, so I thought it'd be a good tip to put on today was to talk about those points of interest for the critical design. So first off, what you see here is a profile cut shot of the, of the flange detail. So this lower red line would represent the top of the flange on the lower mold half, the cavity. This upper line here

[00:45] represents the upper mold, the contra, the B mold, whatever you wanna call it, the second mold half, that's... this line represents. So on that basis, the minimum width from the outer edge of the mold to the part cavity starting is gonna be at least eight inches, so that's the first point of concern. So when we're cutting our flange, our flange of our pattern must be at least eight inches. Another inch extra and we could do some vacuum infusion, but we'll talk about that, uh, another time. So first seal concern, the wing seal, which is the outer perimeter seal, the 1680 wing seal everyone knows about. That should be in a groove that's 540,000ths deep or tall by one inch wide. Now, 540, that comes from... we've got on the top of that cavity flange, we'll put a layer of 40,000ths or one millimeter sheet wax, all then the profile grooves and such are designed to sit on top of 40,000ths wax. So we've got a half inch by one inch profile that's sitting on the wax will give us a groove height or width, uh, top to bottom of 540. Okay. Then we come over and we, we take a strip of the wax away and we've got a hard stop, usually about a quarter of an inch, three sixteenths, quarter of an inch wide. That goes right past the wing seal, and then we come over here just before the dynamic seal and we've got another hard stop, right? That would give us a cavity of one millimeter or 40,000ths between the upper mold and the lower mold, and these two hard stops represent our Z plane, our Z plane stops. That's the registration to come down in Z for thickness in that fashion, and then there's dowels on the mold for X and Y placement. So we come over to our next hard stop here, right before the dynamic seal. But before we talk too much further along, let's point this other very critical dimension. We need four inches between the hard stops, in effect, between the two seals. At 23 inches of vacuum, that four-inch width will give us the compressive force to make sure we're engaged on our wing seal and our dynamic seal by design and be holding us closed during our injection process. So, minimum of four inches, that will be a gap underneath there of 40,000ths. Then we come over here to our dynami- dynamic seal, and that's the 1114GR. The GR represents the heavy-duty gray material, uh, f- much different than the white you may have seen, the gray. So highly recommend using the gray.

[03:39] Then you come down and you've got your resin channel, right? Right next to it. Now, the wall coming down to... You've gotta be able to laminate, be it infusion or hand layup, so you've got a, a distance in here, usually about a quarter of an inch, comes down to a bit of a radius at the bottom. We go into our profile over the top of that for the resin channel, but this is the other point that really caught me off guard when... b- both, both times I talked about this in the last two days, was the pinch. Appears that many are building their Lite RTM molds without the pinch at the edge of the resin channel. Now, what do I mean? All right, so we come down here around the resin channel and then this, this darkened area represents the part... sheet wax, ca- part cavity. We like to bring our sheet wax just up over the flange. Gives us something to start with, also helps us, uh, when we're closing the mold that we don't drag glass down. But this is what I'm talking about right here. That, in effect... Easy way to illustrate that is if we had a round tube, comes around kind of like a donut and, and butted together. Now we got this tube and we're gonna inject resin into the tube. If we cut a slit right in the center around the perimeter, right on the seam as it were of that tube, when we inject in, now the resin's gonna tend to go around the tube and leak through the slit. Very important. See, if we don't have that one millimeter pinch, so again, that gap's one mil- 40,000ths, 39, 40,000ths, one millimeter gap. So when the resin's coming in, it doesn't just flood right into the re- into the glass. If it does, then what... and that was the experience discussed today, was you come in where your injection port is and you're gonna rush in there much faster into the f- dry fiber than what's going on around you, which then gives you an offset flow pattern. We want the resin to circumvent the cavity and flow in as evenly as possible all the way around, and that's achieved in part by this pinch. It's also achieved by the rate, the flow rate you're injecting, but the pinch is critical. So wanna point out, you must have that pinch, your resin channel, your dynamic seal, four inches of distance between the two, and at least eight inches overall to give you the right clearance to get in and, and fit all this together. Well, I hope this tip helps.