Jack Berry
berry2000@prodigy.net

On Sun Jun 9, Dar S. wrote
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>Well, it's just a little thing -one of those little things that are
>obvious and simple only after one thinks of them-  but the implications could be quite large for certain types of press forming.

>Specifically, forming a bit of depth and some detail into a piece with  just one press cycle with urethane. It's basically the old problem of being able to get some depth with softer urethane, OR some detail with harder urethane, but never both, not really. I get resolution on 26 g. soft copper by embossing a flat part, with 20g rd. wire designs, into solid nylon . I get some depth on the same type of part , with a domed area like a bug's head or something, but
>not the resolution on the wires , using 95 a urethane.

>(Reminder: the urethane we've been using is 'shore a', one of the scales used to designate hardnesses of such materials. Shortly I'll bring up 'shore d'. Some confusion could arise because of the use of the letter d , for 'durometer' , a descriptive term not indicative of
>scale type, and used with different scales.)

> So our '80d '  is actually 80 duro, shore a, and what I just tried is 75 duro , shore d. From now on, I'll drop the duro d, and only call them by their shore and duro number. 80a and 75d , for example

>Anyway , I have some things similar to the balloon that I'm working on that need to be domed AND have details pressed into the fronts .
>Making a solid mold like the dragonfly would solve the problem, but drive the cost too high. The ideal is to have 'regular' one step cut and form dies, affordable and fast to use. Enter 75 d urethane, which is harder than 95a , but has less ability to return to it's original
>undisturbed shape. This always seemed like a fatal flaw, for obvious reasons.

> Well, having made cutting dies, had bronzes cast, and done failed experiments with 95a, I was open for  suggestions, and in need of a small (?) miracle. What ended up working surprisingly well was to  set 1/8" of 75d onto 1/4" of 95a , place the 24 g. silver onto that and then the bronze model onto that stack and go to only 10 tons.
>The 75d was deformed , but sure looks like it will last long enough too be economical in production. Small variation, and small detail, but for this type of project, in my shop, it looks like a revolutionization of the revolution.  
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>Dar
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