Scott,
  You should not be changing router compensations on the same board. We go
for months without changing compensation, and then it is changed only
slightly to compensate for bearing wear and run-out. And only a technical
person can modify compensation.
  It is true that you will get a slight difference in measurement from one
end of the panel to the other, but that should not vary more then a few
thousandths of an inch. You should be able to hold within +/- .005" across
the entire panel!

  Here are some guidelines that I subscribe to for routing maintenance and
program writing.
1) The first step is determine the "health" of the router. The extreme
variations you are describing lead me to believe that your router is in need
of repair. The first things I would check are for bearing wear and run-out.
Also do a check on table movement accuracy. These can cause the types of
problems you describe. Check with your manufacturer for the "how-to's" of
these tests.
2) You did not say whether you are using tooling pins (assembled boards) or
are routing without pins. If you are using pins (I am assuming so for this
discussion), always write the program to start away from the panel pins and
work towards them, leaving as much attached to the panel pins as long as
possible. Also, perform routing in a counter-clockwise direction to diminish
effects of push/pull with respect to direction the bit spins. You may need
more (or tighter) pins to help contain the boards. Brushes should be
touching the boards to apply pressure during the route, and this also helps
keep vacuum from lifting/scooting the boards around. I am assuming you have
checked the panels dimensionally. I have had uneven/incorrect panel offsets
from the fab vendor, and even one instance where a designer intentionally
put uneven spacing between rows (this really puts a hamper on trying to
step-and-repeat,ha!) Anyway, hope this helps some. Good luck!

At 05:10 AM 5/13/97 +0800, you wrote:
>From: Scott Westheimer
>Date: 5/13/97
>
>I have just recently been put in charge of routing and blanking and I am
>encountering several issues. Do most of you out there let/have operators
>that change the compensations? Do you have to change them frequently and
>over and over again on the same P/N's? Is there software that can help with
>fabrication?
>
>The reasons for my questions is that we have arrays on panels that on one
>side of the panels is fine, but on the other end we start cutting into the
>fingers. We also have arrays with 3 boards and on the outside cut the board
>is 0.020" to wide and the 2 internal boards they are 0.018" to short. Most
>of the problems seem to be that when we move away from on edge of the panel
>during routing that the dimensions of the routed boards and arrays worsen.
>It seem that this has to be compensation because material does not move
>that symmetrical.
>
>Any help would be appreciated.  
>
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----------------------------------
Jeffery L. Hempton              Phone: (219) 429-7335   Fax: (219) 429-4688
Boardshop Manufacturing Engineer			Mail Stop: 25-31
Hughes Defense Communications                           
1010 Production Road, Fort Wayne, IN 46808-4106
Email: [log in to unmask]

"Always remember the distinction between contribution and commitment. Take
the matter of bacon and eggs: The chicken makes a contribution. The pig
makes a commitment".--Jack Mack Carter

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