Homebrew PCBs

Hi Steve,

Thanks for the detailed description!  I wasn't aware of what is being
done in the sign business!  

I've recently heard of these swivels being about $100, which is a little
high just to play around with, but I'd like to see one run!  I just
couldn't imagine all that vinyl work on a kitchen floor!

Alan  KM6VV
(trying to learn new stuff every day)


Steve Greenfield wrote:
> 
> Tim, smack on the nose.
> 
> Alan, when you see a sign on the side of a vehicle, if it isn't
> painted then there is a 99.99% chance that it is sign vinyl. It
> comes in various thicknesses on a pretty thick backing paper.
> 
> The cutter for it is a tiny Xacto-like blade that swivels in very
> small ball bearings. The vinyl cutter works just like a plotter, in
> fact many also take pens, at least the older ones.
> 
> However, think about how a swivel wheel on a TV cart works- if you
> move the leg of the cart straight, then make a 90 degree change in
> direction, the path left in the carpet is a rounded off corner
> because the swivel has to catch up with the direction of motion.
> 
> You can compensate for this by pulling the leg past the corner
> until the center of the wheel (or point of the blade) is where the
> corner must turn, then you have to arc the leg around that axis
> until it is in a line with the next direction of motion, then
> continue on.
> 
> So it ain't so easy. For a vinyl cutter, it depends on how far off
> from center the point of the blade is, and how sharp an angle the
> blade is. And of course you can't turn on a dime. IE, it must allow
> some curve to the corners to allow the blade to continue traveling
> at all times and not just swivel in place.
> 
> Some sign vinyl cutters (most, I think) do this compensation in the
> electronics. My old Graphtec does this, and of course it is
> adjustable as it varies according to the blade and the thickness of
> the vinyl. You can buy sign cutting software that will perform this
> compensation so that you can use a regular plotter with add-on
> swivel cutting blades, but the few pieces of software that will do
> this typically run in the thousands of dollars. Cheaper just to buy
> a new 12" sign cutter than buy that software.
> 
> Oh, and the way it cuts just the right thickness- on my Graphtec it
> has a thickwalled brass tube the blade sticks out of, the brass
> rides on the vinyl and you adjust how far the blade sticks out so
> that it just barely scores the backing paper through the vinyl.
> 
> Then "weeding" means to remove all the vinyl you don't want
> transfered. A transfer tape is then applied to the surface of the
> vinyl. Transfer tape is sort of like a weak masking tape, only
> really wide (up to 4 feet). The idea is that it sticks to the vinyl
> better than the vinyl sticks to it's backing, but not as well as
> the vinyl sticks to anything else. Anyway, then you lay down the
> transfer tape with the vinyl on it onto the surface, burnish it
> down, then carefully remove the transfer tape, leaving the vinyl
> behind.
> 
> I have a huge roll of black sign vinyl that is very old, so I use
> it for temporary purposes. It wrinkles up and peels away after a
> few weeks of weather. So it works great for PCBs. Unfortunately
> it's age means it is a big pain to weed when cutting very fine
> shapes like PCB traces. Newer vinyl works much better.
> 
> Does that explain it?
> 
> Steve Greenfield
> 
> --- Tim Goldstein <timg@...> wrote:
> > I would guess that he is referring to sign vinyl. It is the
> > plastic film
> > material that is cut then attached to a backing to make signs and
> > banners. The stuff I have played with was about .005" thick with
> > a self
> > adhesive on the back.
> >
> > Tim
> > [Denver CO]
> 
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