Homebrew PCBs

Mike,

I am very interested in this subject since I want to convert several 
table top drill-router machines to PC control. Does your machine read 
directly from the CAD system or is another program needed to correct 
the data? I have experimented with the TurboCNC program and it looks 
like it could do the job but needs a little bit of editing to take 
straight XY drilling commands. Can you give us more details on how 
you run your system? I think everyone in this group has an interest 
in this. My weakness is software but I'm willing to learn.

When I ran Excellon CNC-6 machines they would respond to all of these 
commands but we used just a few of them. Here is a simple program to 
drill several holes:

M48
T01C0.0292
T02C0.035
T03C0.125
%
T01
X01234Y01234
T02
X02Y03
T03
X0456Y0789
M30

The data between the M48 and % tells the machine what drill sizes are 
used. For example, T01C0.0292 means tool 1 has a diameter of .0292 
inches. XY coordinates between the % and M30 will be drilled and then 
the machine stops. Many of these commands are left over from the 
paper tape days with the M30 telling the machine to stop and rewind 
the tape until it reaches the % command. When the cycle start button 
is pushed it starts over. The M48 "header" is normally read once per 
job.

The CNC controller also has what is called a "DIAP" page for setting 
tool size vs. spindle speed and feedrates. The DIAP page settings can 
be in ranges or a setting for every individual tool size can be 
entered and the CNC will find the proper speeds and feeds. In the 
paper tape days the drill files deleted trailing zeroes to conserve 
paper tape and is still used today to conserve CNC memory. For 
example, X02Y03 is the same as X020000Y030000. Most Excellon files 
are in a 2.4 format, X12.3456 etc. with the decimal point implied.
Many CAD systems get fancy and try to "help" by inserting all kinds 
of commands that end up confusing the CNC machine and operator which 
results in extra editing time.

Dave mentioned TurboCNC and I hope he can also tell us more about his 
experience with this program. I sent an Excellon programming manual 
to Dave Kowalczyk who wrote TurboCNC and he said he is considering 
writing a version tailored for PCB machines. Maybe he will have this 
available in the future. I'm hoping both Mike and Dave can tell us 
more about their experience with setting up these machines. Thanks!!

Tom

--- In Homebrew_PCBs@yahoogroups.com, "Mike Putnam" <circuit@g...> 
wrote:
> Someone was asking what types of software people use to manufacture 
their boards. My machine is not setup for milling. I have only used 
it for drilling holes in the boards and thus wrote my own program to 
do so. At the time, I could not get any useable information regarding 
excellon files or NC drill files, so I wrote the program to accept XY 
coordinate files. This is very time consuming for complicated boards 
to produce the original file, but if you are making several of the 
same board, it is quite efficient. Actually, some CAD programs can 
output the XY coordinate file and thus most of the work is already 
done.
> Lately, I have given some thought to adding on a conversion program 
so that the program will accept the NC drill files produced by the 
standard CAD programs (still in the research stages). 
> 
> In my research I came across a webpage with a tutorial on what is 
in a drill file (excellon). I thought others on this group would also 
be interested in this. It is at 
http://www.excellon.com/applicationengineering/manuals/program.htm
> This site is packed with a lot of information.
> 
> -Mike
> 
> 
> 
> [Non-text portions of this message have been removed]