Homebrew PCBs

More:

It was very easy to modify the Sillhoutte to feed pcb accurately. The 
machine comes apart easily and 4 pieces of  3/8 x 9/16 o-rings did 
the trick.  I tried cutting a few pcbs and found:

1 - I couldn't cut through 1 oz copper (approx 1.6mil), but I could 
cut through a thinner board with (I think) 1/2 oz copper. Modifying 
the head to apply more pressure might work?? I believe the downward 
pressure is controlled by the current in the down solenoid, but I'm 
not sure. Have to take it apart more to see. The specs say it can 
deliver up to 210 gms of force, software controlled.

2 - The length of exposed knife is not critical, since the copper is very thin.

3 - The trace cuts are asymmetrical. This, I think, is because knife 
is not symmetrical, and it does not rotate as the cut is made. The 
knife is in a cylindrical holder that is clamped in whatever position 
you drop it into the head and clamp it to. It is rigidly held in 
place. "Cutter Compensation" as Mike Sinclair describes it does not 
occur since the machine has no way of knowing what orientation the 
offset of the knife is. Perhaps more sophisticated vinyl cutters make 
this compensation, but unless I am missing something, it isn't happening here.

4 - In a short experiment I was able to make 16 mil traces. Of 
course, I haven't actually measured the widths, but they seem about 
right in the horizontal plane. The vertical traces look to be about 
twice as wide. All the traces are isolated correctly and intact; I 
"sanded" the board lightly with a pad and all is okay.

5 - I did not get any of the "waviness" that Mike got. As Mike 
suggested, I think that is an artifact of the "tracing". I am using 
svg files directly and am not having problems.

6 - I want to find a conical router blade as is used in a cnc mill 
and see how that works as a drag knife.

7 - I'd also like to get a lighter weight drill. One thing I might 
consider is a small air powered turbine, like is used in a dental 
drill. Another thought is a small, high speed motor like a large pager motor.

8 - The machine is powered by two very small steppers. It should be 
very easy to replace the electronics with a simple stepper driver 
that could be driven by standard cnc software. I'm not sure I want to 
do that, but it would be an easy way to get a very versatile, 
relatively inexpensive lightweight  cnc that could do a lot of 
different things.

Mark







At 10:28 AM 9/14/2012, you wrote:

>I just received my Sillhoute Cameo and have a few first impressions.
>Mike, if you could chime in here I'd appreciate it because I can't
>seem to achieve your results.
>
>1 - I cannot get a pcb to track through the machine accurately. The
>cutter seems to hang the board up so that it feeds irregularly,
>skewing sideways back and forth as it goes in and out of the machine.
>This seems to be true whatever speed I select.
>
>2 - Most of the tracks I get are not completely through the copper. I
>am using the highest setting on the cutter.
>
>I am using Gerbv to convert gerber files to svg, then importing the
>svg files using the "Designer Edition" of the Sillhoute software. It
>seems to work well, but the feed problems make it hard to tell if
>everything is accurate. I ordered a pen holder for the machine, so I
>should be able to use it as a plotter to see exactly what is happening.
>
>The machine looks like it would be very easy to modify to feed copper
>clad reliably. All  it should take is putting a few o rings on the
>shaft for friction and removing the plastic rollers. Hopefully I'll
>have time to take it apart over the weekend.
>
>Mark
>
>
>
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