2011/3/26 Les Newell <[email protected]>:
>
> SheetCam will generate excellent tool center line paths. It handles nesting
> of parts within each other correctly and automatically works out which side
> to compensate. As I have a number of customers complaining due to the lack
> of G41/G42 support I decided I had better do something about it.
>

But how does it handle open lines? I had one customer, who wanted to
cut out animals from plywood for small kids and open lines inside the
outer contour were part of the design.

>
>> 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.
>

At least for me it worked correctly in the same way as You said -
compensation is applied during the first move, regardless, if that is
G01 or G02/G03. For best results, please test it and report here :)


> 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.

I think that making amount of optimization to be depending on the max
kerf width, specified by user, is very useful idea! I just would
recommend testing it more than 6 times with different designs, because
I managed to get that "concave corners, gouging needed" error also on
outer corners, where it did not make sense to me.

> 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.

My conclusion was that G41/G42 compensation works correctly for inside
corners, which are created by two straight lines, so creating rounded
corner is not necessary. The problems start, when these straight lines
are shorter than diameter of the tool (or even more, if that is very
sharp inner corner - for example, in a star contour). So I think that
instead of making rounded corners it would be enough to clean up code
and make sure that there are not many small straight lines.

Viesturs

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