Need a McGyver Solution

MoldMaker · 03-22-2008, 02:39 PM

I have a female mold for a complicated part. It is complex and detailed. However, what I really need is a male mold. So I am planning to pour a male mold using the female. So far so good. The problem is that I am planning to hammer my parts from 1mm thick sheet metal. So the male mold needs to be exactly 1mm smaller than the female. So I need to somehow coat the female mold with a 1mm "filler" substance to take the place of the metal. It turns out this is a lot harder than it sounds.

1) I tried using aluminum foil. However, it it very thin and does not conform to the complex details of the mold. It folds and tears and does not communicate all of the fine details. Adding multiple layers to achieve the 1mm thickness only makes the problems worse.

2) I tried 1mm plastic sheeting. It also does not conform to the fine details and also refuses to stay in place.

3) I tried silicone sheeting and it is about the same as plastic sheeting and aluminum foil.

4) I tried using multiple layers of duct tape. It stays in place. But it also loses all of the fine details.

5) I decided to try a spray on product. So I went with "Plasti-Dip". This is the stuff you use to apply plastic handles to tools. It covered the piece VERY nicely and captured every detail beautifully. But it was only about .20 mm thick. I tried applying multiple layers but only got it to about .47 mm thick - even after about 25 coats. If someone can explain to me why one sprayed coat is .20 mm and 25 coats is only .47 mm, then I'll be very impressed.

6) I tried the "brush on" version of "Plasti-Dip". This stuff was actually terrible at capturing details. It looked good at first but then shrank during drying and cracked.

7) I tried a product by Devcon that supposedly provided a smooth 1mm coat. Unfortunately, it was total crap.

8) Then I tried some "rubberized" coating for roofs that I bought at Home Despot. This turned out to be nothing more than thick paint and left a very thin coating. It was also a total PITA to remove.

So I am at a total loss. I have no idea what to do and I am at my wit's end. I considered using the original part to make a male mold - but that would require destroying the part and losing the shape in the process. The resulting male mold would be crap.

You guys seem smart and resourceful. I am sure there are more than a few McGyvers here. So if you have any ideas, I'd genuinely appreciate them.

TIA.

island911 · 03-22-2008, 02:54 PM

why not lay-up a glass twill, or such? --tough to comment w/o more details.

what's the part? (pic?)

gassy · 03-22-2008, 03:00 PM

some kind of solvent based wax? pics would be good

gassy · 03-22-2008, 03:09 PM

http://www.mjgordonco.com/

maybe

dad911 · 03-22-2008, 03:14 PM

Pour a male mold, then 'remove' 1 mm?

MoldMaker · 03-22-2008, 04:00 PM

Quote:

Originally Posted by gassy

http://www.mjgordonco.com/

maybe

You know, I think you are on to something there. I took your idea and ran with it and found a product called "sheet wax" whose purpose is to simulate the thickness of materials in mold making. Here it is...

http://www.cstsales.com/mold_making_supplies.html

That just might work. Thanks very much for the ideas. I think you guys have helped me a lot and I genuinely appreciate it.

Tobra · Tobra's Garage

Quote:

Originally Posted by dad911

Pour a male mold, then 'remove' 1 mm?

what shape is it, would this be possible?

WolfeMacleod · 04:32 PM

I've done some work for the special effect - film and theater industry.

There is a small magazine/book title you can pick up at Barnes & Noble or other large bookstore called CineFX. It's a quartely pubnlication I think, found on the magazine racks.

In there, look through the advertisers.

There is a company located around Redmond, WA that makes a moulding material. I forget what it's called though. It holds exceptional details, dries VERY hard and durable.

If you need a male mould, just pour some of this into the female mould and let cure.

I'll do a bit of searching to see if I can come up withthe name of this stuff. I haven't used it since the early 1990's. I do recall it was not very cheap, but it was very, very good stuff...

EDIT

I found it. It's called Smooth-on.
http://www.smoothon.com/

Apparently, they are no longer located on Redmond...

idontknow · 03-22-2008, 04:27 PM

Quote:

Originally Posted by MoldMaker

2) I tried 1mm plastic sheeting. It also does not conform to the fine details and also refuses to stay in place.

Does/can you install an air injection port on the female mold? You could heat the plastic sheet and suck it into the mold with vacuum.

Chocaholic · 03-22-2008, 04:31 PM

Hand lotion and tampons.

Problem solved.

island911 · 03-22-2008, 05:32 PM

find some 1mm BB's /bearings/shot ...spray-glue the mold to a tac, dump the shot on, spread around evenly, let dry. then spread in filler to topsof shot.

--the idea being, the shot won't build-up, ...will hold the desired offset.

lendaddy · 03-22-2008, 05:51 PM

I just used some Smooth On product yesterday. Small world.

lendaddy · 03-22-2008, 05:54 PM

There are also products that shrink a certain percentage as they cure.

M.D. Holloway · 03-22-2008, 07:40 PM

Google Rapid Prototyping and see what you find. Dow Corning and Shin Etsu Silicones used to have a pretty good mold making material. You may also find some info on the Conap site.

WolfeMacleod · 03-22-2008, 09:00 PM

Quote:

Originally Posted by lendaddy

I just used some Smooth On product yesterday. Small world.

No kiddin? What stuff? What'd you do with it?

We make moulds for foam latex facial appliances. Stuff like that.

lendaddy · 03-23-2008, 06:23 AM

Quote:

Originally Posted by WolfeMacleod

No kiddin? What stuff? What'd you do with it?

We make moulds for foam latex facial appliances. Stuff like that.

One of the urethane resins. We used it to mold some custom drive rolls for an automatic tube feeder on an industrial cold saw. Nothing terribly sexy

Zeke · 03-23-2008, 08:17 AM

I used to make plugs and molds. Mostly FRP stuff. You say you are hammering 1 mm metal. Is this "mold" actually a buck? What is the final male mold to be made of? If steel, you would have to use a tracer on a multi axis mill. Female to male reverse is possible methinks.

If you are pouring the male just to get a plug and start all over with the molding process, I'd think about the reverse duplicator. I watched a program last night about striking coins. The reducing duplicator is a neat machine.

WolfeMacleod · 03-24-2008, 07:41 AM

Quote:

Originally Posted by lendaddy

One of the urethane resins. We used it to mold some custom drive rolls for an automatic tube feeder on an industrial cold saw. Nothing terribly sexy

Funny you should mention that. Last time I used Smooth-On stuff, it was to make a third breast for the girl I was with at the time...

Haven't done that sort of stuff in years. Sure do miss playing around with it though.