On 2005-07-20, K7ITM wrote:
So, the question becomes, if the plates (rotors
and stators) were available in maybe two or three different basic
sizes, how many frustrated hams would be interested in buying them?

This would be a good emachineshop.com order. You can choose any of the
processes that people are discussing on this thread, depending on the
expected volume. When I played with their estimating software, my
experience was that pretty much everything cost roughly:

$100/ea in qty 1 = $100
$11/ea qty 10 = $110
$1.20/ea qty 100 = $120
$0.13/ea qty 1000 = $130

etc. I figured the biggest risk in using them would be the temptation to
get 10x more units for 10% more and then have a zillion whatevers (eg
rotor plates around the garage. I've been trying to think of a project
that needs 100 identical widgets, and a homemade air variable might be it.

--
Ben Jackson

http://www.ben.com/

Cool, Ben. Thanks. I'm wondering what part you put in to get 13 cents
each at 1000 parts. That would be very attractive, but I keep getting
over a dollar a plate for 3" diameter semicircles with a tab/hole for
the shaft, for rotor plates. Admittedly, the 0.063" aluminum thickness
is more than needed for many applications, but dropping it to 0.024"
doesn't help a lot. I don't figure that making your own cap for low
power applications is going to be very attractive, so I'm figuring the
larger sizes. Also, what machining technique did you pick?

Cheers,
Tom

On 2005-07-20, K7ITM wrote:
Cool, Ben. Thanks. I'm wondering what part you put in to get 13 cents
each at 1000 parts.

That was just an example. I just made a quick 3" diameter rotor with
center hole, laser cut from 6061T6 .047 and 1 is $103, 10 are $123,
100 are $264. It's not quite as steep a curve as the other parts I was
playing with. Since that's laser cutting you can group parts, so if I
throw on a stator too it only goes up to $404 for 100. If I go to slightly
thinner mild steel it's $254 for 100 pairs. Not sure how much difference
Al vs steel makes for this application.

I bet the turret punch would be cheaper, but it can't make the convex
curves.

If you make a die for the rotor it looks like the tooling is about $1k
but the per-part cost can go down to 15 cents each at quantity 10k (for
a net price of about 27 cents each). On the other hand, the lead time
is 72 days!

--
Ben Jackson

http://www.ben.com/