Why doesn't Ramp reach the bottom of the slope?

[juliangall]

I have a shallow bowl form. The sides are formed by sweeping a sketch shape around the rim. The sketch has a spline that tapers gradually to the base of the bowl. This means the sides of the bowl taper gradually down to the flat base.

I use Adaptive Clearing at first (Stock to Leave Axial 0, Radial 0.5 mm), and then apply a Ramp to the sloping sides.

The problem is that the ball end cutter for the ramp won't quite go down (and towards the centre of the bowl) far enough. It leaves a little lip at the bottom of the side. It doesn't remove all the rough edges from the Adaptive Clearing.

I have created the attached model to demonstrate a problem I am having on a real model. My real model also shows a lip when physically cut. i.e. It isn't just a display artifact in Fusion.

If you Simulate the setup, then fast forward to the final stages of the ramp, you can see that the cutter really could do with going round again a couple more times.

Is this a "bug" in Fusion or is there a setting I'm missing?

Thanks for any suggestions.

Julian

[tom_pVDRPJ · Accepted solution]

It's to do with how the toolpath is generated. This toolpath is done on z-levels, not stepped over on the surface. So, as the base of the radius comes into contact with the base of the bowl the stepover becomes larger as the step down remains the same. Spiral Does the opposite and leaves a gap in the steep section of the radius. As it steps over perpendicularly to the Z axis, so when the surface is steep a small stepover is a large stepdown.

Flow does a great job here of keeping the spacing consistent...

It's knowing the difference between stepdown and stepover and understanding cusp heights.

Hope this helps, if you think my answer is sufficient, please select "Accept Solution".

[juliangall]

Thanks for that. I understand what you say about Ramp stepping down in equal Z amounts for each revolution. That ties in with what the documentation says about Ramp: "It is best applied to steep areas and walls that are near vertical"

I wasn't aware of Flow, but I've now tried it and it seems just what I need.

Thanks again.