Re: Resin kit problems...

Westerfield <westerfield@...>

As you'll recall, I was the first to manufacture resin freight car kits. At the time Athearn kits were selling for $3.50. We had to charge almost 5 times that much. I was really scared that the market would not support such a price. We came in that low only by using 55 gallon drums of polyester. The urethane we now use costs 5 times as much, ruins molds rapidly and must be handled in very dry conditions - none of which were problems for polyester. And one piece car bodies take 3 times as long to make as flat castings. So as things have become much easier for the modeler the opposite is true for the manufacturer. - Al Westerfield

----- Original Message -----
From: Andy Carlson
To: STMFC@...
Sent: Thursday, January 22, 2009 12:35 PM
Subject: Re: [STMFC] Re: Resin kit problems...

Resin (polyurethane) manufacturers are numerous, and so many resin variations are available to suit their clients with a challenging array of different production situations that few generalizations can be made. Not all, and perhaps not even"Most" resins are white. A white resin tends to be a more expensive resin. Off-whites and yellows are frequently less expensive. I have used products from Permatex and later from B&J of Tustin, CA that were yellow. These were offered as economical alternatives, and Permatex's was called "Castmaster"(if my memory can be trusted). I stepped up to the pure whites for two reasons-tinting to grey and reduced shrinking. I paid an extra $30.00/gallon kit for these options. Properties of resin include mixing viscosity, pot life, demold time, shrinking rates, cured resin hardness, bubble retention,temperature exposure ranges, and more. The challenge is to get the properties most important, for finding a perfect resin is

The service reps also talk about how heat curing many of the resins makes for a more stable part with less chance of post mold-removal warping, though not all resins have this heat curing property.

One generalization that I will make, most of today's resin casters are using a product which gives them useful parts. The junk resins are mostly not used. Cured resin is very stable, and future anthropologists may find religious icons of 20th century train gods in old landfills, still recognized as railroad cars and sharing space with plastic water bottles.
-Andy Carlson
Ojai CA

--- On Thu, 1/22/09, Denny Anspach <danspach@...> wrote:
> 2) Color is no clue as to resin quality. Normal color is
> white, but
> because this color causes such perception problems (the end
> user often
> cannot perceive sufficient detail to properly orient or fit
> parts- a
> problem shared by many with all-black styrene parts!), a
> color
> additive (commonly shades of gray) is added to the resin
> mix.

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