challenging 3D sketch

[MattBD]

I am making a fixture for a part that has a 3D chamfer around a curved surface edge. The chamfer is 3D because its Z changes as you go around the curve. I only have the parasolid to work with so I can't see how the original part was modeled.

In any case, I was able to convert the two edges of the chamfer to 3D sketches. What I want to do now is to 3D sketch a curve that is always equidistant from the two chamfered edges (so it's really a curve in the plane of the chamfer, which changes as you move around the part).

I'm not sure (1) if I can do this in SW, (2) if I can, how, or (3) if there is a better way to achieve the same result. The reason for wanting a curve halfway up the chamfer is that I am only allowed to use that much to hold the part in this fixture.

Thanks,
Matt

 

[Theophilus]

Maybe you could do this using a different method. Offset your chamfer surface at 0.00". Offset your joining surfaces at the distance you want the chamfer extended (to meet with the "new" chamfer). Extend the edges of the 0.00" offset chamfer surface to pass the offset joining surfaces. Use a mutual trim to create the new surface--or if you only need the extended chamfer surface use a regular trim and keep only the new chamfer.



Jeff Mowry

http://www.industrialdesignhaus.com

Reason trumps all. And awe transcends reason.

 

[CorBlimeyLimey]

To clarify; you want a convex curved feature of the jig to clamp mid-way along the chamfer?

Does it have to be exactly mid-way all the way along the chamfer? Could it be an offset from one surface which places the contact line at or below the mid-point?

An image of the chamfered part would be very helpful.
faq559-1100

 

[Eltron]

I'm not sure I'm getting the problem, exactly. Can you post a pic? Can you sweep a triangle along the path of your new 3D sketch, then convert the edge to a 3D sketch?

Dan

http://www.eltronresearch.com

 

[MattBD]

I'm guessing I can't do an offset in a 3D sketch. I can make a plane that approximates "midway" along the chamfer and see how close that comes.

@CBL: I could probably live with that so long as they can make it on the floor. The chamfer is .020", so halfway is .010" - getting pretty small already.

 

[Eltron]

Let's not all talk at once....

Dan

http://www.eltronresearch.com

 

[MattBD]

http://img219.imageshack.us/my.php?image=fixturevr7.jpg

 

[MattBD]

That is a view from the underside (cut away so you can see the chamfer). I hope that helps and doesn't make things more confusing. I can post one that is marked up or has the chamfer highlighted if that helps.

 

[CorBlimeyLimey]

Wow ... that's pretty small. I was envisaging something larger. That's not much to clamp on. What process is being performed after clamping?

An image would definitely help.

 

[MattBD]

See above for image - heh, we are all posting at the same time. After clamping, this thing is being 5-axis blasted for surface treatment.

 

[CorBlimeyLimey]

This is getting away from a SW answer, but;

Is the material non-magnetic?

Is the jig clamping the chamfer against something on the flat surface opposite the curved surface?

Instead of clamping the chamfer, could you use an expanding type clamp on a portion of the hole profile?

 

[gatz]

What is it that is being machined/processed ?
What edges/surfaces are relative?

.020 actual surface (or max .010 depending on direction of clamping force) is an extremely small area to clamp on and still not distort the part.

What quantity ? Sometimes one or two parts are not that big of a problem; for instance, "Facsimile" or similar replicating material can be used for holding, then disolved out.
But if you're talking production, that's a whole different situation.

 

[TheTick]

You can not do this with a 3D sketch.

You can bisect the chamfer surface with a surface sweep. [ul][li]Use the original uncut edge as your main sweep path (exctract via 3D sketch before making chamfer).[/li]
[li]Use chamfer edges as guide curves[/li]
[li]In section sketch, create a construction line with endpoints on each of the guide curves with PIERCE constraints. Create a regular line that is constrained to the construction line's midpoint and perpendicular to the construction line.[/li]
[li]Create a surface sweep w/ above curves and sketches[/li]
[li]one end of resulting surface will be your "midcurve"[/li][/ul]

You may need to extend ends of your guide curves to make sweep work.

You can also make surface extend through chamfer and get the resulting intersection curve.

Honesty may be the best policy, but insanity is a better defense.

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