Strange muliple lead-in lead-out moves in 2D Contour

[Muzzerboy]

I've got the fairly simple toolpath I was aiming for but the tool wants to spend ages leading in and out many many times at a transition between 2 segments of the profile. Turning leads on and off and keeping the tool down affects the severity of the problem but I can't eliminate it no matter what I do.

Any idea what I can do to clean the path up, short of manually editing out the noise afterwards? I've also tried fiddling with tolerances to no avail. Really can't see what to do about this. 

Contour selection may be at the root of the problem. I need to avoid machining off the boss with the hole in it, so the contour takes in some edges from that feature. 

I've attached the file and a screenshot.

[Anonymous · Accepted solution]

You're right about contour selections. Try this; I made a sketch of the entire contour, seems to be working!

David

[Muzzerboy]

Ah, so you created a sketch to define the profile. As you say, that seems to have fixed the issue. Seems a bit of a compromise to have to do this but is probably a pragmatic workaround here - thanks!

I really struggled to select the profile to start with - when selecting segments one by one, it would suddenly decide to include the entire chain including the inside which I don't want, despite having selected open contour. I had to add the patch over the slot which helped to some extent but even so it was a nightmare. 

Selecting and (even more) unselecting segments in 2D Contour is a nightmare unless the profile is a simple, continuous contour. There are quite a few posts expounding how simple it is to include non-planar segments but once you open the contour it seems to fall apart.

They should try this model if they think it's simple - try to select only the external profile (without machining away the boss) and see how you get on!!

[Anonymous · Accepted solution]

I find myself using this workaround quite often, as you wrote, selecting and deselecting contour elements can be a royal pain... But the sketching really works quite well, it snaps really fine to the existing contours.

David

[Muzzerboy]

Presumably the sketch will update to reflect any changes to the underlying model? I'm never 100% certain about whether sketches (projections?) will do so. I'm bound to finesse the model before the day is done.

[Muzzerboy]

In fact, the sketch you created had several unconstrained (blue) arc segments which presumably wren't linked through to the model and could cause issues if I went back in to revise the model. 

But your approach got me thinking and I made visible the original sketch that I used to generate the part from and was able to select the contour from that. Presumably the path is now linked to the model, so any changes will flow through. I ended up with 2 chains - one derived from the basic extrude profile and the other from the boss. Then removed the segments I didn't want, set the correct direction of tool travel(!) and the result is just what I was after.

[Anonymous]

Good observation. Never thought of that. 

[Anonymous · Accepted solution]

More often then not, with stuff like this I just move into the CAD side and create a quick solid to assist in chaining the elements.  For example, with your part I just extruded the slot closed (creating a new body, not joining).  Then, when selecting the geomtery for toolpathing you can simply use the new CAD to close the loop.  Quick and dirty work-around.  I know you can also achieve the same result with sketch as others have mentioned but this works for me.  

[Muzzerboy]

Yes, creating a new body is better than deleting features - hadn't thought of that. As you say, it makes selection easier - but doesn't compromise the actual model. And I expect it will update if changes are made to the model.

That's another approach to keep in mind when fighting 2D Contour.