How to create an arc slot with a ramped floor between the endpoints?

[raymus.houston]

I am trying to create an arc slot with a floor that ramps between the slot endpoints following the contour of the arc, but haven't had any luck getting fusion to do what I want. I tried a loft between 2 circular profiles and extruding a 3d sketch, but neither produced the outcome I have described.

Attached is an F3D of a sample part with an arc slot extruded normally to the depth of the lower end of the slot if anyone is interested in helping me figure this out. The higher end should be -.125 from the top of the part and the lower end should be -.1875 from the top.

[jhackney1972 · Accepted solution]

Attached in your model with a different name.  I did your measures to the extreme ends of the slot, not the centers.  I labeled one sketch and one construction workplane you can adjust to get different values. 

[raymus.houston]

Thanks for the quick reply!

If I understand correctly, you did a surface sweep using those 2 tangent lines in sketch 2 as the profile and the vertical line in the sketch which controls the height is the path and then extruded the slot profile to the surface to make it the floor of the extrusion? I never would have thought to do anything like that since I haven't really worked with surfaces all that much.

Seems like something I should look into a bit more.

Thanks again @jhackney1972

[chrisplyler]

Depending on whether you want to control the depths from the very ends, or from the end's center points....

(You could also control with a single depth and an angular dimension if you preferred.)

https://knowledge.autodesk.com/community/screencast/0ae5aa93-d3eb-4a43-a2fc-be49c4f48484

[TheCADWhisperer]

Let's back up for a minute.

1. How are you going to manufacture that?  Cut slot with endmill?

2. What mathematical ramp do want?  Uniform helical pitch?

[chrisplyler]

Oh...an ARC slot. I'm stupid, so I missed that bit.

Same as before, only you can't use a construction plane as the TO OBJECT. So you've got to make a lofted helical surface body to use as the TO OBJECT. So it's more complex to set up, but still the same idea.

But I'm with @TheCADWhisperer ... how the HECK are you going to mill it? I guess it could work if you're 3D printing it, but milling it with a bottom like that seems impossible.

https://knowledge.autodesk.com/community/screencast/d999dbc8-315c-4567-832d-fa81a37d1abe

d999dbc8-315c-4567-832d-fa81a37d1abe,640,620

[raymus.houston]

@TheCADWhisperer & @chrisplyler The lower end of the slot will have a flat diameter, so that it can be milled using a flat endmill. I was able to get it to work this way using a variation of @jhackney1972's method, but using the inner radius of the lower slot end to sweep the surface. the original file I posted was just a sample part to get the method worked out. This is an image of the feature that I made for the actual part.

[TheCADWhisperer]

I am in the process of creating a video for illustration.

It looks like you got it right - can you Attach the file here?

https://youtu.be/VAJQ_y87oqA

[raymus.houston]

@TheCADWhisperer Attached is a sample file with the flat bottom lower end.

[chrisplyler]

I did it in Fusion by surface sweeping the lower end flat bottom circle up the helical ramp guide surface, then splitting the squished tube it made with the helical ramp and removing the upper half. Left me with the dished bottom. Pretty sure the bottom is an ellipse.

[TheCADWhisperer]

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@chrisplyler wrote:

Pretty sure the bottom is an ellipse.

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I my test - it is not symmetrical across the bottom going around the arc ramp. 

While "elliptical" in shape, not true mathematical ellipse.

[chrisplyler]

Weird. I would think it would be an elliptical cross section at any single point, assuming the section cut was through the radial center point of the arc. If the section cut isn't radial to the arc slot, then of course the bottom is going to be deeper on one side and more shallow on the other.