Info on resin casting?

[2-8-8-0]

Hello folks. My first kitbash of a P2K 2-8-8-2 into a B&O 2-8-8-0 (EL-1) is getting to the point where i will need to start adding details like sand domes, air pumps, and smokebox door, and i am gonna need to cast some parts from resin i thinks. Anyone point me towards a book or site that has a breakdown of how to make the mold and cast the part, as this is all new to me.

Thanks, Tim

P.S. I have a newfound respect for all you guys that did these sort of builds WITHOUT articles and forums for guidance.

[CVSNE]

There's a casting group at Yahoo Groups - it's pretty inactive but specific questions usually bring some reasonable responses.  Most of those guys are really into casting, so the advice will be centered on getting vac chambers and the like - - good ideas all, but no really necessary for the kind of parts you're making.  (You can afford to cast 10 pieces to get one truly "good" part.

Craig Bisgeier has a number of items about the experience he has had casting parts, structures, and complete freight cars for his Housatonic RR on his web site - http://www.housatonicrr.com/

One of the best sources for getting started I know of is Tom Piccirillo's "Making More Than One" in the May, 2002 issue of that god awful magazine, Model Railroader.

Some basic advice - watch for undercuts since those are the kind of voids where air bubbles will get trapped - think about how the resin will flow before you make the master or the mold, and pay particular emphasis on minimizing air bubbles.

Good luck!

Hope this helps,

Marty

[up1950s]

There are a few people right on this forum who do castings very well , once they read your thread will no doubt give you the help you request .

[diezmon]

it's a lot easier than you may think.  I'd start with the basic how-to sections on these sites:

http://www.alumilite.com/howtos.cfm
http://www.smoothonsecure.com/store/howto_service.php

or even google "resin casting" and you'll get quite the list of sites.   

That's how I got started.

[asciibaron]

i might have to sacrifice an Atlas car in the name of science and learning - would be nice to bring the unit cost down and be able to correct the doors enmasse.

-Steve

[TrainCat2]

Steve, That sounds more like donating rather than sacrificing.

I would also recommend articles on this site for first timers.
http://www.bare-metal.com/plastic-modeling-molding-articles.html

[diezmon]

i might have to sacrifice an Atlas car in the name of science and learning - would be nice to bring the unit cost down and be able to correct the doors enmasse.

-Steve

That's what I'm doing.. now that I have a master for the 'ol 40' box I can start churning out my own 

[asciibaron]

how are you getting them out with the grab irons and stuck - seems like you'd have to do it as several molds, but in the picture you have a single mold - the car is injection molded with tooling that has slides - you have a single mold - is the rubber flexible enough to remove the shell and still provide good castings?


-Steve

[diezmon]

how are you getting them out with the grab irons and stuck - seems like you'd have to do it as several molds, but in the picture you have a single mold - the car is injection molded with tooling that has slides - you have a single mold - is the rubber flexible enough to remove the shell and still provide good castings?
-Steve

It's basically like a semi-stiff rubber.  You apply mold release which also keeps the resin from sticking to the mold.  You just gently break the "seal" and work the piece out.   I've seen people make molds in several pieces.. but that increases the changes of having seam lines.. but if you lay things out correctly they can be minimized.

I've always used a single mold and plug method with no problems.

It's even easier if you're doing things like domes and doors, since you can mold them flat and they don't need a plug.  They can just be a single piece of material.. know what I mean?

[asciibaron]

what is the unit cost for a car once you have the mold, and how long does the mold last?  next train show, i'll be the one looking for the $1.00 car to practice with...

-Steve

[TrainCat2]

Squirt some alcohol between the casting and the mold. It will wick in eveywhere and break the "seal" and act as a lubricant. The casting wil just pop right out.

[Chris333]

A mold is usually good for about 20 castings, but if you are careful while removing the harden resin casting you can get many more out of it. The problem it there will be some tear out and in time it will get bad enough you won't want to use the mold anymore.

I have cast simple things like car parts and domes.