green trimming in the mold- removeable flange?

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#1

I’m currently working on a new mold and since I’m planning on potentially using VIP in the future, my thought of late has been to add a 4" flange around the whole mold. (3-peice mold of a front bumper skin).

Now, the problem with this is that since adding a flange means the mold extends past the point at which I would want to trim the part, green trimming would appear to no longer be an option.

So what should I do? I see my options as:
1)have bolt-on flange sections.
Pros:best of both worlds
cons: super complicated, potential sealing issues- maybe I should use a massive envelope bag anyways since the mold is multipiece?

2)use aluminum tape or something?
pros:no potential sealing issues or release issue
con:have to re-do the tape for every part.

3)skip the flanges altogether- super 77 the fabric in, trim it to “within sanding distance” before even doing layup or infusion
pros:no flanges is simple. fabric is pretty easy to cut dry
cons:have to be pretty exact in cutting to keep the bag from messing up the edge where the fabric overhangs.

I’m kinda think of just skipping the flanges.

Basically it’s a huge part wil LONG trim lines that are brutal to try to jigsaw/bandsaw straigt.

Smooth, straight trimmed edges seem to be the thing you immediately start to chase after once you’ve got the general process down hey? :smiley:

Thanks guys. Sorry to be so long winded.

#2

Make and use the flanges to tape seal the bag.

But since you are going to VIP, you can take the time (or if mass producing, make reinforcement master cutting templates) to cut and lay it up exactally that you want it when finished as you do that when itis dry.

#3

One of the great positive properties of using vacuum infusion is you have all the time in the world to position your laminate layers perfectly. There’s no hurrry to get everything thrown into place.

Another option is to make some tooling patterns to clamp or secure to the finished part to use as a guide for trimming after the part is pulled from the mold. These can easily by making a “scrap” part and cutting up pieces to use as master trimming templates. These are sometimes just as fast (and ususally more accurate) as trimming a green part.

#4

Speaking of master templates.

What cloth are you guys using to make them?

I am set up for infusion now (all my molds have flanges) and I hate to say it but the trimming thing sucks.

I got some carbide sawblades but mad does that take forever to do.

#5

If you are talking about the dry cutting templates: bath tub white board!

#6

Do you guys have some pictures of your master trimming templates ???

#7

I’ll take some this night at my classroom and post them tomorrow when I have the time…

#8

Thanks guys! The trimming templates are a great idea. The top edge of the bumper can/should literally be shaped like the top of a stock one, so that gives me a perfect line to trace onto a template.

Sounds like tacking the fabric to the mold and trimming it perfectly while dry and then infusing will the the 100% most painless though.

Yet another reason to bite the bullet and buy that pump! :smiley:

#9

Here’s a picture of a Pinto front fender cutting template for a 1 piece front end:

#10

Sweet. I am so going to try that. The ability to not have to trim cured parts would be a spectacular christmas present. :smiley:

#11

Anytime you are going to do production on a part, using a cutting template saves time with any process.

#12

tried that today. What a paint to get my stuff done. I got one of them done and the rest I am going to try after this lay up. My parts are curved more convex really so its a test of patience to “chalk” a line in paper, cut and tape the next peice and so forth till I get a pattern and then the one I have still kinda sucks to be honest.

#13

What we use is 10 oz fiberglass cloth to lay into the mold straight and trim to fit. Then pull it out and lay it on the board to trace and give a little extra fudge factor too. Sometimes we have to trim the template a little a couple of times before getting it fully correct. But it saves time in the long run.

#14

Im gonna have to try that. Seems a bit better in the long run than what I am doing now.

#15

That sounds like how I imagined doing it- laying some glass in, trimming it, pulling it out of the mold, then tracing it.

I thin it’ll be a bit tricky because it’s a concave mold with a lot of curvature, so it’ll be tough to get it laid in the mold flat. I might have to use a bit of tack spray or something and then try to pull it off…

another theory was to attempt todust the mold with some sort of powdered dye, lay some glass in dry and apply vaccuum, then pull it out and use the dye outline.

Probably best to just give it a little fudge factor and refine the template a few times though…

#16

Make any and all cuts or darts to the template to save time every time you go to make a part…even use templates for peel ply and vacuum bagging too.

#17

vac bag templates- now yer talkin’! :smiley:
This is going to be cool.
Once I have this new plug done I’m going to photlog the whole mold building process and the template making.

#18

It even blows me away the race car fabber’s I supplier PC race windows too never use templates to make their alum interior panels, even tho they make them for the same make and models for years…:rolleyes:

My PC race car windows templates were close to 10 years old until I made new improvements and had to get around to making all new ones

I hate to reinvent the wheel every day! LOL.

#19

Stumbled onto a mistake with my too light of gelcoat problem that will help me make these templates.

When I did them with so little gelcoat and I didnt add much fabric to the part becuase I was so suspicious…They were incredibly flexible. I was bending the part almost on top of itself. I imagine that I should be able to do it again and just flatten the part out to trace it on some poster board and have an accurate template (once the part is trimmed of course!

#20

or you could be a real cheap a$$ like me and send it down the street to have someone laser trim all your parts for you. I do this for most all of my parts now.

It takes a quick and simple holding fixture, and I can get my parts back trimmed as close to the line as I want. Then I just wet sand the edges and after drying, spray it up and polish it.
Here is the C-6 Corvette trim kit that we make . It is only >030 inches thick and can be installed without removing any of the original equipment. It just slips on over the original part and is held inplace with only a few short pieces of double faced tape.
All laser trimmed (3 pieces for $50.00 I can’t get that repeatability if I tried it myself.
And no scrap (screw up’s) this way.