Re: Vinyl Cutting Algorithms

Hello,

Steering angle, as you say it, is easily found using the arctangent
(ATAN). A few lines of code to handle crossing zero and quadrant
boundaries, and you have the makings of a c axis "tangential" cutter
for vinyl...

As to the drag knife problem, Rab may want to add a small circle for
the trailing blade to follow during a "turn-around". At least a
triangular motion, which could be accomplished with a single straight
line "sideways" added movement (is that the squiggle of which you
speak, Rab?)

Hope this helps,

Ballendo

P.S. You are correct in assuming the problem is from the depth of
cut. As you increase the cutting pressure (and therefore the depth)
two things happen, both bad: first, the effective trailing distance
is shortened (this is the drag in drag-knife), which makes a shorter
lever arm to turn the knife. And second, the already harder to turn
knife is more deeply embedded in the material, which also makes it
hard to turn. So set the knife pressure for as shallow a cut as
possible, until you can change to a stepper driven tangential cutter
c axis...




--- In CAD_CAM_EDM_DRO@yahoogroups.com, "alex likhterman"
<telecom@i...> wrote:

> Yes!
> Therefore it should be fairly easy to calculate steering angle.
> Alex
> ----- Original Message -----
> From: fortino <fortino_tan@h...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Thursday, July 17, 2003 9:15 PM
> Subject: Re: [CAD_CAM_EDM_DRO] Re: Vinyl Cutting Algorithms
>
>
> > I would think that the direction of the blade is parallel to the

first

> > derivative of the curve
> >
> > fortino
> > ----- Original Message -----
> > From: "alex likhterman" <telecom@i...>
> > To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> > Sent: Thursday, July 17, 2003 10:18 PM
> > Subject: Re: [CAD_CAM_EDM_DRO] Re: Vinyl Cutting Algorithms
> >
> >
> > > Rab,
> > > may be to put a stepper on the blade to steer it?
> > > Alex
> > > ----- Original Message -----
> > > From: rainnea <rainnea@b...>
> > > To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> > > Sent: Thursday, July 17, 2003 5:12 AM
> > > Subject: [CAD_CAM_EDM_DRO] Re: Vinyl Cutting Algorithms
> > >
> > >
> > > > Hi,
> > > >
> > > > I've taken account of the blade offset and have written in an
> > > > algorithm that corrects for this.
> > > > Looks like I'd need to write in an additional algorithm to

account

> > > > for the occasional times when the blade reverses direction

between

> > > > cuts. It would probably just need a short squiggle cut on an

unused

> > > > piece of the vinyl to turn the blade.
> > > > This problem only occurs when the blade is set slightly

deeper than

> > > > normal, a light shallow cut seems to allow the blade to turn

more

> > > > easily in these instance.
> > > >
> > > > Blades and holders from http://www.blades.uk.com
> > > > good service and the owner really knows his stuff.
> > > >
> > > > Rab
> > > >
> > > > http://www.rainnea.com/cnc.htm
> > > >
> > > > --- In CAD_CAM_EDM_DRO@yahoogroups.com, "fortino"

<fortino_tan@h...>

> > > > wrote:
> > > > > Rab,
> > > > > Typically, the blade is not centered. It is offset about

0.1-0.2 mm

> > > > from the
> > > > > center.
> > > > > This offset would allow the knife to swivel/ turn every

time it

> > > > changes
> > > > > direction.
> > > > > Beside, how about your knife? do you buy it or make it by

yourself?

> > > > >
> > > > > I have two vinyl cutting machine that was driven by Gecko.

The

> > > > mechanical
> > > > > part
> > > > > was build using chinese brand vinyl cutting machine. It uses
> > > > stepper motor.
> > > > >
> > > > > fortino
> > > > >
> > > > >
> > > > > ----- Original Message -----
> > > > > From: "rainnea" <rainnea@b...>
> > > > > To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> > > > > Sent: Thursday, July 17, 2003 7:30 AM
> > > > > Subject: [CAD_CAM_EDM_DRO] Vinyl Cutting Algorithms
> > > > >
> > > > >
> > > > > > I've added drag-knife vinyl cutting capability to my CNC

Toolkit,

> > > > > > however it encounters a problem when the blade direction

makes a

> > > > > > complete about turn of, or near to 180 degrees as often

the drag

> > > > > > blade wont turn by itself and ends up going backwards for

a while,

> > > > > > ruining the cut.
> > > > > > I'm considering various approaches to add an extra

movement to

> > > > help
> > > > > > the blade turn into the cut, just wondering if this is

something

> > > > > > anyone else has come across before ?
> > > > > >
> > > > > > thanks,
> > > > > >
> > > > > > Rab
> > > > > > http://groups.yahoo.com/group/CNC_Toolkit/
> > > > > >
> > > > > >
> > > > > > Addresses:
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> a
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> for
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> > timg@k...
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reach it

> if
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> > > http://www.metalworking.com/news_servers.html
> > >
> > > http://groups.yahoo.com/group/jobshophomeshop I consider this

to be a

> > sister site to the CCED group, as many of the same members are

there, for

> OT
> > subjects, that are not allowed on the CCED list.
> > >
> > > NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY

POSTING THEM.

> > DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
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> timg@k...
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> >
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> > If you wish to post on unlimited OT subjects goto:
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reach it if

> you have trouble.
> > http://www.metalworking.com/news_servers.html
> >
> > http://groups.yahoo.com/group/jobshophomeshop I consider this

to be a

> sister site to the CCED group, as many of the same members are

there, for OT

> subjects, that are not allowed on the CCED list.
> >
> > NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY

POSTING THEM.

> DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
> > bill
> > List Mom
> > List Owner
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> >
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http://docs.yahoo.com/info/terms/

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