I've given you a fast and CHEAP method!
Fill an inkjet printer cartridge with Future or other brand acrylic floor polish! Print that to
the board, then etch away! After it's etched, wipe it off with ammonia!
If you get .014 thick single sided PC board blanks they will feed through all the printers
I mentioned without modification. If you want to do doubled sided boards, you'll have to
remove the printer mechanism and change the platen roller to a linear Y axis to move the
length of the PC board laying on a plotting table.
An easy ( and cheap ) way to do this is first calculate the gear ratio of the stepper to the platen
roller. Then put a simple pulley on each end of the plotter. Attach a wire 'cable' loop around these
pulleys and attach the printer mechanism to that cable. Of course the printer mechanism is riding
on two standard linear rails. ( polished shafts and bronze bearings ).
The Lexmark I first used needed more gear reduction than a single pulley could provide so I used
a microcontroller to catch the phase steps to the micro and output a reduced set of steps to the
original stepper motor. I used a 16F628 PIC and an L298 for this. The steps ratio was adjusted via
a serial connection to a PC.
I was able to modify an Epson 1520 wide carriage printer to feed a standard .062 board through but
that didn't solve the double sided problem. The only way I found to do that is convert the printer to a
flatbed arrangement. The nice thing about the Lexmark and cheap Epsons I looked at is the power
supply and all electronics are on a PC board that's mounted to the mechanism. Take it out of the
plastic and you've got a nice small "rail" to mount on your Y axis linear rail. The only cables you
need to connect were the wall wart and USB cable.
Oh, there is an issue with the "out of paper switch" that some printers pull a sheet of paper in until
it hits a switch or optical sensor then they back it out to a preset location. I was able to get around
this with the same gear reduction microcontroller. I just used the "paper" switch for a "home" switch
and that let the mechanism return to 'home' between each run. A manual "run" switch served as
"paper out" so you had to flip this switch after you got a board blank on the bed. That lets you easily
plot one side, flip the switch when it's returning home, flip the board over, flip the switch again and
let it plot the other side.
By the way, the floor polish works well in plotter pens for etchant resist also.
I can't take credit for the thought of using acrylic floor polish for etchant resist. Evidently artists that do
copper plate art stamping have been using it for years.
I also left a board with .020 traces in ammonium persulfate for a week to see if the acrylic would stand up to it. It worked
great. However, I did the same thing with some .005 wide traces and the etchant undercut the traces and it
all floated away.
You could also use floor polish for scratch and etch resist but you'll need to color it with something to easily
see it. I do think the machinist blue is best for this approach.
The machineist blue is a nitrocellulose base with several alcohols for solvent. It drys too quick to use in an inkjet
in case some is thinking of trying that. ( been there, done that, clogged up the cartridge). It doesn't work all that
well in a plotter pen either.
Oh, I almost forgot, you'll also need another board to lift the PC board blank surface up towards the inkjet head.
What I did is measured the distance between the paper and the platen roller on the existing printer, then cut
a piece of MDF to thickness with a wood planer. Just subtract the thickness of the PC board blank you plan
on using from the needed thickness. You could automate this with some screws a stepper and a belt on your
Y linear rail attachment points to make it work with varying thickness PC board stock.
later,
Larry E.
----- Original Message -----
From: crankorgan
To: Homebrew_PCBs@yahoogroups.com
Sent: Sunday, September 15, 2002 3:56 PM
Subject: [Homebrew_PCBs] Re: Inkjet printing PC boards
Hi Alan,
So many people messing with underpowered plotters, I
just had to remedy the problem. Everytime I had it done I
found a way to make it cheaper. I would be nice to find a really
simple and cheap way to make PCBoards. I mean fast and cheap!
John
--- In Homebrew_PCBs@y..., Alan Marconett KM6VV <KM6VV@a...> wrote:
> Hi John,
>
> Saw your site. Nice implementation on Morph!
>
> Alan KM6VV
>
> crankorgan wrote:
> >
> > Hi Alan,
> > Yes using a spinning scribe would make a wider path. I
> > have an animation on my webpage. Let it load and you will see
> > a pic of each side of the machine. One guy built a clone of the
> > Morph by just looking at the pics.
> >
> > John
> >
> > --- In Homebrew_PCBs@y..., Alan Marconett KM6VV <KM6VV@a...>
wrote:
> > > Hi John,
> > >
> > > What about a small rotating burnishing tool, so the "scratches"
> > would
> > > have some width? I can see that this would be very similar to
> > milling
> > > the isolation traces.
> > >
> > > Alan KM6VV
> > > P.S. Heard you've got a new mill/plotter working? pix?
> > >
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