Dec 09

Secondary bonding

We know that you’ve heard all sorts of nonsense about molded parts or boards. One of them is that molding creates heavier parts or boards because the resin is trapped inside the mold. Well, those folks figure you’re ignorant and will just assume that is correct, or they literally don’t know what they are talking about. It’s easy to see that logic. Resin IN the mold and there ain’t no way for it to get out! The reality though, is molding is so popular and so widely used outside of the surfcraft manufacturing that almost all of the BS spewed about molded parts has been addressed. Right? NASA uses molding for spacecraft, Boeing uses molding for the 787 composite parts, where literally billions of dollars are spent annually and the molded detractors would have you believe that neither NASA nor Boeing could figure out that resin rich environment issue. THAT’s how stupid that logic and vile BS is.

There is a technology referred to as Pre-Preg, in which the reinforcement material is PRE sprayed with just exactly the correct amount of resin, lets say 45% by weight and then it’s wrapped up and kept cold, like in a freezer. The end user, say NASA takes it out, warms it to room temperature and then lays it into a mold. NO EXCESS RESIN. The reality is that molded parts don’t have any of the issues that are commonly stated about them, it’s just BS to protect some self-interest.

Ok, so here is a picture of one of our first test parts. We want to demonstrate its REAL easy to develop a resin starved part, plus we can also do some labor in the mold.

photo (6)

You’re probably used to seeing carbon fiber in finished parts that’s all shiny and with a perfectly aligned weave. That stuff is gorgeous and tends to have lots of polyester resin on the surface. We don’t need that for these parts and in fact we want ONLY the minimum amount of resin possible. Well…best laid plans and all, we didn’t quite get our resin application right and came up a little short. In the picture above, if you look in the trough you’ll in the lower left corner a dry spot. Our bad! So it’s pretty easy to screw up and create a resin starved part while molding. This test part, however, did allow us to get the correct amount of resin figured out.

Ok and one more failure in that picture. It’s hard to see, but the high spots in the wave structure are nice and shiny and the low spots or the troughs aren’t. We used what is referred to as a peel ply to create that texture or non-shiny spot in the troughs. It’s simply a fabric, but when the resin cures, it will have a pattern in it where it touches the resin. It’s used for areas that will be subject to secondary bonding and at times to soak up any excess resin. Can you see our error though? You don’t want a shiny surface where you’re going to be gluing or what is referred to as secondary bonding. It’s just harder for a glue or epoxy to stick to a slick shiny surface. So guess what we did? Somehow we put the peel ply on the wrong side! We really wanted the high side of the wave in the picture above to have that textured surface. Anyway, we’ll just apply it to everything in our final production part! The peel ply allows us to skip some sanding labor!

There is a vast array of tools, and supplies to manage virtually everything associated with molding parts.

That’s all for today, thanks so much for following along!

Technorati Tags: ,