> in my shop we have used small offsets in EMC2 for a long time
> we have had no issues of resulting incorrect geometry from entry or exit
> motion

If you look at the docs on radius comp you will see that if you don't 
have a lead in, the first move will become the lead in. The start of the 
move will be un compensated and the end of the move will be fully 
compensated. I don't know what happens if the first move is an arc.

> if you have artistic designs and generate tool centerline code with a lot of
> small linear (and possibly circular) moves then EMC2 and its radiusing of
> the outside and inside corners will be problematic at best and unworkable at
> worst

Which is why I am adding G41/G42 support. If SheetCam knows about the 
offset it can generate the correct tool paths to allow for it. In some 
cases it does mean that parts of the original drawing may be optimized 
out but the generated tool paths will be completely legal for EMC or any 
control as long as you don't specify a larger radius in the control than 
you specified in SheetCam.

> if you change to part geometry code (offset by the tool radius) you will
> have a different program but you will still encounter the same problems with
> the cutter comp
> the same amount of change ie .002 inch
>               with centerline code total adjustment is -.002
>               with geometry code total adjustment is still -.002 even though
> the number for a 1/4 cutter is .123 instead of .125
> both will not work for the same reason

The difference is that if SheetCam knows about the offset then it can 
make sure that for instance inside corners always have a big enough 
radius to allow for the tool without any warnings that you will gouge 
the part.

> I ,too, would like to have the choice of using this feature or not
> I have requested this option and argued this point more than one time (to no
> avail YET) :)
>
> I want 5 axis cutter comp - with this 'feature' enabled 5 axis cutter comp
> is not workable - with this feature disabled then 5 axis cutter comp would
> be possible

My brain hurts trying to think about 5-axis comp. I assume you could 
only use it with a ball nosed cutter. Thinking about it, surely 
kinematics would have to add the comp, not the interpreter. The 
interpreter doesn't know about the kinematics of the machine so it 
doesn't know the cutter orientation.

Actually adding squared corners isn't that difficult. Instead of 
calculating the angles of the two lines to add an arc you simply find 
the intersection of the two lines. The difficult bit is finding someone 
motivated enough to do it. I am afraid I don't have a plasma or waterjet 
so I don't have a lot of incentive to do it myself. Unfortunately my 
spare time is rather limited.  I am only just finishing off my EMC 
controlled lathe now and I started that about 2 years ago...

Les

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