Re: [CAD_CAM_EDM_DRO] Re: Milling Glass

Ballendo,

I built a tangental vinyl cutter about 7 years ago, and used Dancam. It
worked pretty well. On your drag knife design that you are describing here,
how do you compensate for the fact that the blade is behind? Don't you need
some sort of radius compensation? It would seem that right angle turns
would be cut off.

Tom E.

----- Original Message -----
From: <ballendo@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Thursday, April 12, 2001 7:08 PM
Subject: [CAD_CAM_EDM_DRO] Re: Milling Glass


> Hello,
>
> Walk into a vinyl sign shop and ask them where they purchase their
> cutters...
>
> There are two types used: tangential and drag-knife. The tangential
> is mounted with the ability to turn (C axis) into the direction of
> the cut. The drag-knife type is probably what you will want. This
> cutter is shaped like a TINY #11 ex-acto blade (if it were made from
> rod stock) The top is ground to a point, and rests in a holder. There
> is a magnet in the top of the holder, and a ball bearing (single
> ball). The holder is often aluminum, and some are available shaped
> like a plotter pen, for obvious reasons :-) Techno-Isel sells one,
> but their price (as usual) is ridiculous,IMO.
>
> The cutters are relatively cheap (say 15 bucks), but the holders can
> be pricey; and not much of a lathe project for anyone with some
> experience.
>
> The Drag knife style works fine until you start making small
> designs/letters. Then, the offset from center of the blade point
> (that's why it is called "drag" knife) starts to be more than the
> move length and the cut path is distorted. Tangential cutters solve
> this problem, but require a dedicated axis and software which has an
> integrated C axis for tangential cutting. Dancad/CAM is one freeware
> example which does have this capability.
>
> Hope this helps.
>
> Ballendo
>
> P.S. You will want to have a "floating" head for this. While we're
> here, I'll let you in on a secret. You can do some of this cutting on
> any cnc machine WITH an ex-acto blade and round handle holder! Simply
> drill a vertical hole through a block of plastic, wood or metal,
> sized so the trailing edge of the blade can "turn" the knife. Often,
> you will need to tape a coupla washers (for added weight) to the
> knife holder(handle).
>
> A longer term setup might use a bronze bushing through an alum block
> mounted in Z. With a setscrew collar on the blade handle for weight
> and "lift"-ability...
>
> You can try other ex-acto blade shapes. There IS one which is better
> than the #11 (which works), but I don't know its' number. Remember
> the words above about distortion of cutpath based on feature size
> versus blade "trailing" dimension. Have fun!
> __________
> ________/ /
> _____/ Ascii art of the "better" ex-acto blade shape.
> /
> __________/
>
> Hey, I just realised that you could grind away at the point of the
> #11 until the "trail" dim was whatever you wanted!!! The distance is
> measured from the CENTER of the MOUNTED blade/ holder.
> /| _
> / | / | Modified #11. Flat across top
> / | #11 type blade / | would slope down toward right.
> / | / | (Ascii art limits exact-ness)
> | | | | pun intended :-)
> | |
> | |
>
> > Where can one purchase vinyl cutter suitable for
> > fixing to a mill/router?
> >
> > Peter
>
>
>
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