Small Part Stuck in Mold

[wcnfl]

I built a small console plug with seat / storage box attached (20"W 38"L 28" T) The console has little taper and tight corners with little radius.

Wood plug, Oil based Paint, Waxed 5x, PVA 3 coats, Orange Tooling Gel, 3 layers 3/4 oz mat, 1 layer 8 oz cloth

Obviously not enough taper and radius on corners.

My question is what is a rule of thumb for enough taper? and radius?

As I destroyed the mold getting it off the plug it seemed like the lack of radius on the corners was the problem.

[Itchy&Scratchy]

Minimum 5 degrees draw angle and as much radius as you can get away with.
You say you destroyed the mold getting it off the plug.

You put PVA on, did you try soaking the whole thing in warm water, thats what PVA's for, it dissolves and frees the mold.

Sometimes, they like to stick in the corners. Boxes can be a bit tricky and sometimes is worth the effort to use a diagonal flange and two part mould.

Did you leave it enough time, ideal time is two weeks, unless you can postcure, but in reality a day or two at normal room temperature is adequate.
Personally I prefer two pack polyseter filler coat as a surfacer or Durabuild, sand easily and polishes up nicely.

Dont worry , most moulders have had a f*ck up at one time or another, even though this lot might make you feel like they havent.
good luck with the next one
Itchy

[SamSam]

At least two degrees taper/draft and as much radius as you can do, mainly for looks, 1/2 " radius (1"diameter) as a minimum. You can also drill a hole and inject air to help pop a part off.

[wet feet]

I would be concerned about a number of things;the geometry of the part would be one and the finishing and use of release agent would be another.I have never used oil based paint as the basis for a mould and would strongly question the wisdom of doing so.The advice offered on corner radii and draft angles leans toward the generous and less has been used successfully.Was this your first attempt at moulding?

[wcnfl]

Yes this was my first attempt...The I used a marine top side oil base paint with good gloss and waxed it...seemed slippery enough and even after mold was broken off it still feels very slippery.

Probably got to aggressive on removing the mold. Should have tried drilling holes and blowing air into the holes...I tried water didn't seem like it was getting into the corners and bottom of mold...maybe it needed more time to work.

I'm tring to build a small lightweight compact console with baitwell / storage. I would like to keep it as large as possible...when you start radius corners and putting alot of taper you loose storage and insulation space.

The sides of the console had 1" of taper over 28" not sure of degree will have to check...the front to back had no taper...and the corners were rounded not really what I would call a radius...Obviously not the ideal plug.

I think I need a 2 piece mold...which I was hoping not to do...my thought is If one can't sucsessfully make a one piece mold why would one think he could build a two piece mold???

[TeddyDiver]

You could use water flange molded fast in your mould. Just set it on top of the plug and laminate the mould. Assembly pressurized water on the flange..
You might also use epoxy for mould laminate bcs it doesn't have as much shrinkage and thus releases a bit easier.

[wcnfl]

Please eplain water flange...

I used polyester do you think is shrunk causing difficult release?

[gonzo]

Many molds have an air valve to put pressure and help release the part.

[wcnfl]

Air Valve / Water Flange how do you attach to mold?

If you have open hole in mold what keeps the from sealing over? when you are laying up...

[TeddyDiver]

Polyester is tricky bcs of the shrinkage on a male plug/mold and thats the main reason for generous taper. That's also important to have an oversized plug (and mold) to get the final product in right size.

Flange..

[TeddyDiver]

Originally Posted by wcnfl

Air Valve / Water Flange how do you attach to mold?

If you have open hole in mold what keeps the from sealing over? when you are laying up...

Set it on top of the plug and laminate fast when doing the mold. On a finished mold set a clip of pvc tape over the opening to close it..

[gonzo]

In a console you put it in a place that will get cut off. For example at the steering. Use a small piece of masking tape to keep the resin from filling the hole.

[TeddyDiver]

Magic word.. tape
Anyway with a flange installed you can inject about anything you want to get it of.. thou nitroglyserine is not recommended

[wcnfl]

Thanks for all the input...what would the recommendations be from here?

1. Build new mold with Water / Air Valve
2. Build 2 part mold
3. Build new plug with more taper and radius

[TeddyDiver]

I'll vote 3 and 1 in that order..