I've evaluated them for high volume production, and calculated the quantity
as being a pallet at every build station, and spaced at line rate
throughout the line and solder machine. Then put a .5 hour of pallets at
load and unload (so the operator didn't have to get up and down every 5
minutes). No .5 hour hold was envisioned if the line had (or would have) a
pallet return conveyor. I also added 10% extra for spares so we wouldn't
shut down while repairing a pallet.
Quantity depends upon line length, line rate and conveyor issues.
-------------
Original Text
From: C=US/A=INTERNET/DDA=ID/TechNet(a)IPC.ORG, on 4/29/98 11:29 PM:
Hi Ken!
I've not done a formal study, but I've always recommended the number of
wave fixtures based on what kind of wave machines I have, and how many
fixtures will fit inside the machine while waving them. For instance; with
a
Electrovert Ultrapak and normal sized board (not a 18" X 20" monster) I
would
figure 5 in the machine, 1 being unloaded, 2 already unloaded and cooling
down, 1 getting ready to go into the machine, and 1 getting loaded up to be
put into the machine...so 10 fixtures total.
It never made any difference what the yearly quantity was, just as
long
as it was going to be an ongoing thing I would always recommend 10
fixtures...we would never be waiting on a fixture while waving that way. If
the quantity was going to be a lot more and we were using another wave
machine, I would double the quantity...this is to prevent bottle-necks...
Now if the customer balked at paying for 10 fixtures and the quantity
was
low, but ongoing, I'd let the production manager (or someone at that level)
make the call to go with less than 10...after all, it's gonna slow down the
thru-put outta wave when you hafta wait on boards to finish waving before
you
get a fixture to put the next board into...
So the short answer is, it depends on how many fixtures you can cram
in
the wave...I know it's not scientific, but everytime I've had to explain
why I
need 10 fixtures to a customer, they've understood...
-Steve Gregory-
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