Curved surface, how increase volume of surface at certain points only?

[Anonymous]

Hi All

I would like to know how I can add more volume to curved object surface?

Say for example I have a plastic cup.

You can think of this as cylinder object ,which was the shelled out using the shell tool and then had its base sealed.

Now at certain parts, I would like to increase the thickness and then blend it the rest of the surface(may be chamfer its edges) .

At certain parts on curved surface I would like to add an extra mm, I think if the surface was flat I would just sketch the shape, then extrude it by few mm and smooth the edges by doing a chamfer

But how can this be done on surface that is curved? Or multi curved for edges?

Regards

DJ

[sam_m]

who are you talking to?  you've replied to JD so are you asking him (but can't remember him posting an example), or are you asking about my example?

If you mean mine, i'll try to explain the processes in my example.

If you have a curved/complex face and you want a bulge to match that then you need to offset the face, which will match the curve/undulations of the parent face.  An extrusion will extrude to a face to match it, but its start will be flat so you either need to offset the face and do an extrusion from/to or use an offset surface to split/skulpt the flat-side away.

So... basically, the easiest way to have a face that is an offset of another is to, erm, offset it...  Hope that's explained that.

With that sorted, we've got an offset surface above our existing "parent" one, which can be used for our power-bulge.  So, now we need to consider where we want the bulge and how to blend it into the existing geometry.  Create a sketch with a loop to represent where we want our power-bulge to exist (the inner loop on my sketch) and use that to trim the excess of the offset surface away - leaving just a disc of the offset surface as the crest/top-face of our bulge.  Now we need to think about where we want the original/parent face to start to deform and blend into that bulge, so in that same sketch as above I offset the "bulge loop" out to represent a perimeter of the original face, where I'm wanting it to start the bulge.  I used this outer loop on the sketch to split the original face and then used delete face to remove the area under the bulge - this turns the original solid into an open surface with a hole where I'm wanting the bulge to start to grow out.

So, now we have 2 surfaces...  the original form with a hole in it and a smaller disc being the crest of the bulge - all we need to do is link them together in a smooth blend...  So, use a loft and select the edge of the hole in the original and then the perimeter edge of the disk and it will show a preview of a loft going straight from one edge to the other - getting there, but it's not a smooth blend so use the "conditions" tab to specify you want both ends of the loft to be tangential, which will change each end of the loft into a smooth blend.  (if it's having problems, or is a complicated surface then I would imagine a number of rails might be needed to help with this blend - if this doesn't make sense then you need to learn/research lofts).

so, now we have 3 surfaces:  the original with a hole, the smaller "bulge" disc and the loft blending the two others together.  Use stitch to add the loft and the bulge to the orginal part and if it was a solid previously then it should "ping" back into a solid again.

sorted...

note: If you use extrusions and try to model this as solids then you may well have problems trying to get the blend to work with the loft - you really need to work with surfaces (and thus my breaking the original solid into a surface for the blend).  It's not "day 1" beginner stuff, so if surfaces are something new then I'd really suggest working through JD's surface tutorials (they might be a little old now, so some commands might be a little different, but it's all about getting the correct mindset to work with surfaces and his tutorials are great): http://home.pct.edu/~jmather/content/DSG322/inventor_surface_tutorials.htm 

Hope that all makes sense, Sam

[Anonymous]

Ok, been playing around and its been progressing.

Now when I do a loft, am I correct in saying this is between to offsets?

One ofset will be at a height e..g 4mm and the other will be at the surface.

When I do this is do see the gradual blend, but this part of the object is still seen in light tranparent brown as you would see an Offset.

What must I do so that can be the same material as the object.

I had to also create my outer sketch again, as when made an offset of the inner sketch the outer disappeared.

DJ