Tuesday, October 06, 2009

A Modern Fairy Tale

(A Guest post from Cabbage)

Once upon a time……in a little known valley…..on a north facing hill….was a man stuck inside with three kids at home for the school holidays and the misses out working (don’t know why I call her the misses, she hardly ever does)… so with a lot of time to think and dream and only six other railway projects on the go and a dozen more ideas waiting for info

The thought from Amfet and Mac Druff started a discussion on the lack of good bogies for NZ120.

With all the time in the world and little to do but referee the fighting the mind turned to web surfing on the subject of injection moulding.

With a few contacts from the yellow pages, the cold calling began with Stephen and Richard from Uniplas in Lower Hutt answering all the silly questions the mind could dream up about injection moulding.

A visit to the factory was arranged and the 3D model of the items to model were brought along to get an idea of the complexities and the cost of the injection moulding process.

Stephen and Richard were very helpful and approachable and happy to talk about a Wheel set and Bogie frame for NZ120 modelling.

Of course you can see where this is all going; and you will know that if you are not sitting down then the shock from finding out the cost of the things involved in the injection moulding process will make you fall over....hard....

Luckily (in my case) a chair was at hand and the piece cost for the machine time and the plastic at 0.6 grams per shot was a light 25 cents for 2000 shots. However, it was the tool cost that was the killer!

I can’t say any of us have this kind of money lying around and if we did it would be spent by the better half long before we knew about it.

So I’ll try and say it as fast as I can ……. (Drum roll please)……… six thousand six hundred dollars for the tool to do 2 wheel sets and around twelve thousand for a tool to do the bogie frame and 2 wheel sets.

Of course a tool like this is made to stand the pressure inside the injection moulding process and is good for at least 250,000 shots…..so looking at the tool life is only adding 5 cents to the piece cost.

How is that for a thought? A correctly scaled one-piece bogie and wheel sets for NZ120 for 30 cents each! And after all the "think-tanking" taking place, a wheel would look like this:

Who wants one.... or to really help things along 1,000 of them?

If we could find 1000 people who would buy 250 bogies each (at $75 all up) it would be worth the investment....which equates to 125 wagons, or 5 decent sized trains of container wagons......

So where are the other 996 people going to come from??


Luke Ueda-Sarson said...

Wow, that sounds a rather cheap injection mould cost to me! (Try talking to people who want to make miniature figurines, typically for wargaming purposes, to replace white metal with plastic) Prices must have rally come down. I guess it's only to be expected since making the thing is all computerized these days.

Cheers, Luke

Darryl said...

Is that a steel die or 'shorter run' aluminium one?

What is the plastic? Delrin-like?

As this is my "#1 thing that NZ120 needs" I'll pledge enough funds for a lifetime supply.

ECMT said...

Would it be cheaper to get a bogie frame done by RP, then use that to get a master cast, which in turn could be used to cast frames in brass ?

ben scaro said...

I once did a master for an Nn3 bogie that Peter Boormann cast in Australia.

It was molded from grey urethane and worked OK. Probably not as good as delrin, but beggars can't be choosers.