[rfenn]

This is the first time I noticed that there was a Viacad section here on CNCZone. Shout out for mmoe who assisted me on the Bobcad forum a few months back by recommending this CAD package. It is a great value for the price and is much more intuitive for basic 3D work than BobCad.

I had a design change where I had to go from a pure symmetrical object to one that transitions from round to nearly square (see screen shot). Think of this as a bowl but I won't go into details about what it is exactly. My objective is to 3D print this, so I need an enclosed solid. For something produced from primitives, this is fairly straight forward in Viacad (I use version 8). Problem is that I had to create this by transitioning from a circle to a radiused square and then skin it. First I couldn't figure if it was even possible to skin it in Viacad, so I sent it to BobCad V25 where I was able to put a skin on it. It has some wrinkles but I can try a higher resolution (ie more transition rectangles) later if I get this basic concept to work.

So first question is 1) Should I be able to do all of this in Viacad? If so, how would you go about it. I couldn't figure it out from the surface utilities or find a tutorial/video on it.

Second question 2) Assuming you can't do this in Viacad, how would I go about properly closing my inner and outer shells so I can print this? I have two surfaces here and not a solid, so can't use solid add/subtract.

I'm attaching the screen shots and a zip file with the wireframe viacad file, the shell one is too big to upload.

Attachment 217048Attachment 217050

[mmoe]

Glad you're enjoying ViaCAD!

I'd say that you should be able to achieve what you're after by using the "Skin Solid" feature from your initial wireframes. This feature basically takes your profiles and creates a smoothly transitioned solid through them. One trick to the feature is that you must first create a "Group" out of each set of profile curves/lines (found in "Edit" menu "Group -> Group". If it's not a group, the tool will error. A circle does not need to be changed to anything. The vertical lines will not be used, only the planar curves/lines. To make the part, you select the tool and then Shift+select all of the profiles that you've grouped.

Once you have that made, it then depends what you are trying to do with it. If there is supposed to be a bottom, you could use the "Shell" tool and create an even wall and bottom thickness with an open top. If you want the bottom to be empty like your sample, but want a wall thickness to the sides, you could achieve this two ways. First, you could offset your profiles inward the amount of your desired wall thickness and run another "Skin Solid" to create the volume of the inside void. Then subtract that inside void mass from the whole. The downside here is that the wall thickness may not end up perfectly even depending on how your 2d geometry is designed. For that reason, it would be my second choice. The other way, which I think would be the better option, would be to change the solid to surfaces using the "Change Object Type" under the "Edit" menu, then delete all but the outer skin. Once you are down to that outer skin, you should be able to use the "Thicken" tool to offset the surfaces by the desired wall thickness and it will generate a solid. The "Skin Solid" tool would have likely made the outer skin as one surface, so you probably will be able to offset it all at once. If the "Thicken" tool goes the wrong way (outside the surface instead of inside of it), just add a minus sign in front of your thickness value and it will reverse.

I did a very quick test and these processes will both work, again depending a little on your specific geometry. Even a pretty ugly part was able to be done with the "Thicken" tool after changing it to surface and deleting all but the outer most surface. One thing to keep in mind is that you're using a lot of profiles to define the shape of your object. While this may initially seem like it will give more precision, the problem is that it will also generate warped faces if the profiles are not exactly the way they should be. If the transition through some of the middle profiles tugs at the skin in a bad way, there will be warps or large wrinkles. This is not an issue with the tool, it just means that your conceptual profiles do not define a smooth transition from one to the next the way you think they should. Nurbs surfaces are a bit like B-splines when they run through control points as opposed to when the control points are just tugging the B-spline. If those control points (the profiles in this case) are well thought out, the resulting curve will be smooth. If they are not well thought out, they look rough. Doing this shape well is going to be more about how you design each level of your profile than the tools themselves, so if you are finding the results unsatisfactory, you'll need to go back to your 2d geometry and make your adjustments there just as you might make an adjustment to a control point to fine tune a B-spline.

[rfenn]

Got it. I probably would never have figured out the grouping trick to make this work. I had to experiment a bit and I carefully read your post and have an actual solid that I needed. Huge, huge thanks for the help. Unbelievable how quick and detailed your assistance was. I owe you one. If I was getting paid for this, I'd send you the money for this section. If you need a minion for some stupid work, let me know, since unlikely I could return the favor via Bobcad of Viacad assistance for quite some time.

Here is the part I was struggling to achieve. I do have parts to merge into the bottom, but that should be fairly straight forward relative to this challenge I had.
Attachment 217072