I discovered some strange things with Gerber and drill data, and now
I would like to know more about the way how these CAM tools handle
the data.
"Official" Sieb & Meyer is like that:
%%1000
X1234Y5678T1
.....(further hits with T1)
X9012Y3456T2
.....(further hits with T2)
My own little CAM editor produces "so-called" Sieb & Meyer 1000 files
like that:
%%1000
T0T1
X1234Y5678
.......(further hits with T1)
T0T2
X9012Y3456
.....(further hits with T2)
Well, that's more "Excellon"-like syntax, not correct S&M.
My PWB manufacturers did never say anything
against it. Meanwhile, I know, that they repair the incorrect data
without telling me anything. They could spend the whole day only with
telling customers that their data were incorrect.
A leading PC-based CAM-tool does not accept these wrong data, another
CAM-tool does!
If somebody gets the wrong data in his fingers and
removes only the T0, happens the following (assumed, a real Sieb &
Meyer NC machine reads the data)
%%1000
T1 (the machine adds an additional hit at X0Y0)
X1234Y5678
..... (further hits with T1)
X5678Y9012 (last wished hit with T1)
T2 (completes with the XY coordinates immediately before)
X9012Y3456
.....(further hits with T2)
and that means, I have at the last coordinate from T1 an additional,
wrong hit with T2.
The one leading CAM tool accepts these data exactly like the real
drilling machine and shows the additional hits - the CAM operator
can see the wrong hits before scrap production. The other leading
CAM tool (and my own little CAM editor, too) reads the data WITHOUT
the additional hits, that means, with these tools nobody finds the
error, until he gets the first 10,000 wrong drilled PWBs for scrap.
I wonder why so many PWB manufactures never complain about wrong
data, but silently edit the errors (I hope) before the first
production run (that's the experience here in Europe. They are afraid
of loosing customers if they complain too much....)
Perhaps somebody has similar experiences with strange and
different data handling by CAM tools. I have another example, too.
Official RS274X command for "inch" is %MOIN*%. Many postprocessors
use instead "G70". Some CAM tools accept this as RS274X, some CAM
tools do not accept this and ask explicitely for the unit.
Regards
Matthias Mansfeld
-----------------------------------------------
Matthias Mansfeld Elektronik
* Printed Circuit Board Design and Assembly
Am Langhoelzl 11, D-85540 Haar, GERMANY
P.O.B. 1143, D-85529 Haar, GERMANY
Phone: +49-89-4620 0937, Fax: +49-89-4620 0938
E-Mail: [log in to unmask]
Internet: http://home.t-online.de/home/matthias.mansfeld
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