Re: Radius Compensation---Leadin

--- In CAD_CAM_EDM_DRO@y..., "IMService" <imserv@v...> wrote:
> > Date: Thu, 26 Jul 2001 01:24:21 -0000
> > From: dougrasmussen@c...
> >Subject: Re: Radius Compensation---Leadin
> >
>
> Doug- The EMC requires that the D offset be called out on the
approach
> line where Cutter comp is turned on
>
> N10 G41 D1 G01 X7.8491 Y-4.5326
>
> That is the issue that I dealt with in the closing note about the
contour.
> EMC team should have known better but they didn't and even though
this
> was pointed out to them a couple of years ago, it's not
been "fixed".

Yes, I understand that. It does seem ridiculous to need the D1,
could lead to problems if you change the original tool call up and
forget to change this "D" call out.


>
> Also I always recommend that people position to depth before
turning on
> Cuttercomp. Some controls will allow Z positioning inside a cutter
comped
> activity, but many will automatically turn off cutter comp and move
from edge
> cutting to center cutting and result in a gouge or broken cutter or
both.

This is very control dependent. I think most controls will allow Z
moves while in CC.


> >Fred, What's the point in the circular entry/exit from the
contour?
> >Won't it leave undesireable evidence of the entry/exit on the
part's
> >straight contour section? Isn't line N16 extraneous?
> >
>
> The point of the arcing start and end cuts is that you cut all the
way around
> and have no divots from starting or stopping, and if you try to
start cuttercomp
> with a cut onto the final geometry, you can easily end up with an
uncut area
> and tool deflection at startup. My sample toolpath has both arc in
and arc out
> which leaves no dwell marks like you get if you plunge straight in
with a
> Z move, and the .2mm overlap assures there is no missed material.
This kind
> of cut would normally be used for finishing not roughing and you
would have a
> very difficult time detecting the actual location of the start or
stopping point.
>

This is a point where I think you're dead wrong. Why begin/end a
profile on a straight section when you could just as easily start/end
off the part profile? There is no doubt most machines will show
evidence of that start/end since you are running over a short section
of the profile twice. This is especially true of the less rigid,
slow prcessing "homemade" machines most on this list are using.
IMHO, poor programming/machining practise.

Some profiles, like a circle, do require a start/end ON the profile.
But not a straight sided one like this.




>
> Line N16 is needed because I changed the start and end of the
cutting from
> the corner that was originally used (0,0) to the center of the
first line along the
> X axis. (x=5). I also changed the direction of cut and comp side
to allow climb milling.

Huh? Your ultimate target point is X4.9, why the X5 line?

It seems to me you have turned a simple shop floor programming job
into one requiring CAM (unless you can compute those circular moves
in your head). Did you find my example code to be in error?

Most CNC guys could program simple stuff like this in less time on
the shop floor than it'd take to boot up a PC.

Comments?

thanks,

Doug