Re: [ATM] Figuring questions on a 6f6.

["Jerry" <wa4guu@verizon.net>]

Hello Anthony 

Let's check the numbers first.
Are those knife readings inches or mm?
1.9 and 3.8 mm look more like proper numbers for a fixed source tester.
I haven't used FigureXP, I don't know if that does inches or not.

.125" would be knife movement from center to edge with a fixed source
tester. so with the center of the mask opening a little inside the edge
about 1/4" .107" or 3.8mm would be right for a fixed source tester. So I
think I know what you mean on the desired readings but then I don't know
about the actual readings. Maybe those are inches. That looks matches better
what I would expect 10 minutes of work to do. In that case your target
numbers in inches would be .075 for zone 2 and .107 for zone 3. Is your
micrometer calibrated in inches or mm?

You mask dimensions would be helpful.
And what kind of tester do you have? Does the light source and knife mover
together?

Jerry

-----Original Message-----
From: atm-bounces@atmlist.net [mailto:atm-bounces@atmlist.net] On Behalf Of
Anthony Anconetani
Sent: Tuesday, October 09, 2007 10:19 AM
To: atm@atmlist.net
Subject: [ATM] Figuring questions on a 6f6.

Good morning guys,
 
Well, I'm trying to decide where to go next in figuring my 6F6 mirror.
Before I do anything rash, I think I need to consult with the experts.
 
The ideal measurements in FigureXP are 
 
0.000
0.0019
0.0038
 
The room temp is 85-87 degrees (still hot in Texas). The tool is full
sized with G73.
 
 
After about three hours of polishing I checked the figure. The edge
looked good and the mirror looked spherical. I decided to do another
hour of polishing to be safe. I then checked the figure again made the
following measurements:
 
1: 0
2: -0.014
3: -0.023
 
I decided I was high in the center but I knew that would be easy to fix.
So decided to try some parabolizing.
 
I did 10 minutes of MOT using the parabolizing stroke. I tried modified
the stroke to do some extra work around Z2 and Z3. Here were the
results.
 
1: 0
2: 0.043
3: 0.045
 
I was a little surprised at how much I actually took out of the center.
I'm guessing I went to far to the left and right. Anyway, I decided to
go with a basic 1/3 COC TOT stroke. I figured this would reduce the
correction between Z1 and Z2 and would reduce Z3. Ten minutes of 1/3 COC
TOT gave the following.
 
1: 0.000
2: 0.036
3: 0.060
 
I was happy with the reduction in correction from Z1 to Z2. I also
noticed that Z1 had a smoother transition from it's inner edge to it's
outer edge. However, I was really surprised to see the delta from Z1 to
Z3 increase. I thought the TOT would have a tendency to flatten out the
mirror. The above indicates the center became deeper.
 
I mulled this over for a while and decided to try another round of 1/3
COC TOT. My guess was that Z3's increase relative to Z1 was a temporary
dynamic in the glass. I think was wrong. Here are the results of 10
minutes 1/3 COC TOT:
 
1: 0.000
2: 0.053
3: 0.088
 
Well, I'm thinking COC TOT is not a good idea at this point. I'm just
really surprised that the center got deeper.
 
So questions:
 
1) Why did COC TOT deepen the center?
 
2) Since COC TOT does not appear to be reducing the outer zone, how
should I reduce the outer zone? A narrow W stroke with 1/2 diameter MOT?
Or maybe a wide W stroke with 1/6 TOT? How about a stick of dynamite...
 
Thanks,
 
-Anthony, Round Rock TX.
 
 
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