Return Flange Idea - Guidance Needed

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#1

I’ve completed a mold and I need to add a return flange to it. The idea is to bolt some material to the VE mold flange then using my router with an offset trim bit create the return flange surface; the router tool will have a nose mounted bearing which will ride along the VE mold surface.

Like this:

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mold_flange_2_.jpg

Here’s my issue - I’m struggling with selecting the best material for the return flange. I’ve considered epoxy tooling board but its damn expensive and not offered in the thickness I need. I need something with a low thermal expansion coefficient, good finish after machining, and decent temperature resistance. I’m starting to wonder if wood would be up to the task. When molding with a wood solution I’m thinking I would place release film over the wood before laying up. Or maybe some sort of sealer on the wood. Do any of you have experience using wood for such an application?

#2

What about sheetwax? You can order it based on thickness, or double, triple it up to obtain your desired width and height for it on the flange.

#3

Thanks for the reply SLS.

I considered machinable wax but was concerned about how robust it would be with multiple uses (5-10 parts maybe) and temperature. However the machinablity would be great. I didn’t really mention the scale we’re talking about - the thickness of the return flange will be 1.5 and the mold is +20ft long. I’ll need quiet a bit of material.

#4

Aluminum plate… Easily machined

#5

yeah, I quoted that - $1600 for the plate not including the water jet roughing. Allot of time in the roughing.

My initial reaction to the quote on the epoxy board was I can do it cheaper with aluminum… I was wrong. So now I’m considering wood. The return flange isn’t really cosmetic so it doesn’t have to be absolutely perfect.

#6

Is this for a joggle gasket seam on a two piece mold? Do you still have the plug that was used to fabricate the mold? If so I can give you detailed instructions for how to fabricate the flanges with composites that will fit perfectly.

#7

What about HDPE?

#8

The joggle/step in the finished part will receive an adjacent part. I do have the plug and was considering doing the return flange (with zero offset) using the plug set in the existing mold then applying sheetwax to the molded return flange to create the needed offset. Honestly, I’m just really loathing the idea of doing any more mold layup after the 85 gallons I’ve been through…

What are you thinking?

Not a bad idea. Relatively cheap too.

Thanks for the ideas guys this is helping.

#9

Here is how I make them.

  1. Put the plug back into the mold
  2. Cut a piece of sheet goods that will bolt to existing flange. I often use acrylic. The cut just has to be close to the existing plug surface. There will be a gap between the sheet goods the plug. This will become the joggle tool.
  3. Pipe in some thickened resin into the corner between the plug and the existing flange. Bolt the cut sheet goods into position. Using more thickened resin you fill any unfilled area in the gap between the plug and the sheet goods. I often build up a fillet.
  4. Once cured you can unbolt the joggle tool and remove them. The joggle tools will now have an representation of the opposing part surface. You can use sheet was to build up an offset onto the joggle tool…or…
  5. Layup a part in the opposing mold that will be thickness of the finished part + the required added thickness for the bonding adhesive thickness.
  6. Once cured the opposing part is demolded and the edge portion gets glued to the face of the joggle tools. This will make a perfectly contoured offset on the the joggle tools. I do this if I’m expecting to fabricate quite a few parts. This sames time and money from having to apply the sheet wax for every use.

Make sense?

#10

Yep, makes sense. I like the first method - do you use the acrylic/resin tools in elevated temperatures? I’m just curious how the dissimilar materials cop with temperature.

I think for the purposes of this project having the option to change sheet wax thickness on the return flange is a good thing. Because the composition of the mating structure might change in the future.

Thanks for the advice.

#11

I’ve only had the Acrylic up to 145*F.

Another option is cast them. You can put the plug back into the mold and build a dam around the existing flange and cast the joggle tools. I often mix epoxy and playground sand for casting operations. You can quadruple your resin volume. It works with low exotherm resins like epoxy. I don’t think that it would work with VE or PE due to the higher exotherm temps. If you need to drill holes in it you can use a rotary masonry bit. Put some light glass on each side and they can be very durable and stable. I usually lay down some glass against the existing flange, then pour/pack the epoxy/sand mix, then put mirrored glass on top.

#12

What I’m leaning towards is using the same tooling resin the mold is made from so I don’t have issues with dissimilar expansion rates of the return flange and the molds. I’m going to build a dam to reduce the amount of layup and material usage. I’ll use CSM and some fiberglass tape as reinforcement. No gelcoat though, just resin as the actual molding surface will be sheet wax anyway.