Hi,

I am trying with all my mental faculties (whatever that amounts to) to use the tools at hand to make up for NOT having ViaCAD 5 Pro, particularly in not having the Surface Trim tool. (But, as you'll probably find out in the drawing, even VC5Pro cannot trim some of the surfaces all of the time....)

I have one-rail-swept a pair of curves (lines, actually) which are the web and flange of a large stiffener. I have a station (a curved, top-to-bottom line I exported from another application) from a given location along my model. I do NOT want to do Change Object Type to curves, surfaces or mesh. Going to Curves creates HUNDREDS of useless, PITA connect/join curves. Surfaces I don't want because I already have one in the sweep, and I don't want to thicken 208 or 104 surfaces.

I thicken the swept lines and then try to use the surface and adjacent solids to trim solids. I generally do NOT care about keeping the underlying surface, as once the two lines are swept, thickened, colored, and given weight, they are not supposed to change. If they NEED to change, i'll export another from the source app.

I admit that some lines I export have some funky curves. Not all of them do. Most of then I can one-rail sweep just fine.

But, ACIS is a PITA in that it is so damned restrictive that it interferes with my using ViaCAD to even sweep the line. I wish ViaCAD would sense this and say, "OH, can make a copy of this that you CAN manipulate..."

Also, I have tried to take a closer look at my lines I am sweeping. The one in particular that is a PITA is the flange portion I swept. I need the flange to have various lengths of say 160mm to 200 mm, REGARDLESS of the nature of the station/curve being swept against. It should not matter whether the originating flange line starts out at horizontal, or any other elevation, as long as the length is settable. The user should be allowed to trim off any excess material via construction of a bounding box, introduction of a surface or a solid by which to cut, or by using the Trim Line tools.

The resulting sweep line is of such a nature that it (by design?) Defies being cut. I cannot turn on nodes (Ctrl D)

Offsetting is pointless, as the radius is either off too much, or the lines converge.

When I use the Trim Solid or the Split Solid tools I get this error message (or some variation of it, but the part number varies, of course):

"ACIS Error
! Inconsistent face-body relationships:Trim Solid_10324009"


Like I really care what *ACIS* thinks. Just trim the bloody solid! The flange top is horizontal, or maybe be at any odd angle. ACIS, I think is too damned restrictive, or not loose enough, not tolerant, and unforgiving. We're not creating DNA inside a solid.

I have considered offsetting the surface and stitching it, but ehhhh....

If ONLY ViaCAD 6 had the Trim Surface tool... But WAIT...

I tried the trial/demo version, and it TOO could not trim this specific line. So, that test quickly resolved any question I had about the ViaCAD code/tools.

I think, ultimately, I will have to knuckle under and just manually tweak the troublesome lines by chopping off the bottom part through trial and error.

So, I created a level plane to the area of interest so I can evenly chop off all the bottoms of my stiffeners. Actually, I want to SPLIT the solids so I don't have to re-import or copy and set aside duplicates.

But, to my disappointment, I am having trouble there, too. If I chop the existing stiffeners (solidified by now), the curves' smoothness and paths all change in small ways. Mayb I should not make a big deal out of it, but if this were precision surgical or implant of other shapes...

Has anyone got any advice for me? Should I just dispose of all my solid stiffeners, use the plane to lop off the kinked/troublesome bottom radii, and then redraw the one-rail-swept webs and flanges so that bottom curvatures are not dictating (or falling prey to ACIS's responses) that such and such lines would intersect?

I would have attached a dxf, but it's now allowed, it seems. I apologize to those who might have "version" problems.

Thanks for any feedback!

Hello ZLC

If I'm understanding your description correctly then the problem you are having is that your surface to trim and surface to trim with have identical boundaries ie their edges are exactly co-incident. ACIS doesn't like things which are exactly co-incident when trimming so you just need to extend your trimming surface so that the surface being trimmed is contained within it completely or use an infinite plane instead which has the effect of doing this automatically. This is not just a limitation of ACIS, most 3D surface modellers also suffer from this issue to some extent or another, hence why this method of extending surfaces to completely bisect other surfaces has been given a name - overbuilding. Just do a Google search for "surface modelling overbuilding" and you'll find articles relating to this issue in lots of other modellers.

Hope this helps

All the best
Nick

Hi Nick,

The upper area of the attached file is what i was aiming for, which is pretty much what your image was showing me. Now that i've been clued in (made to remember) how to trim solids, i can resume working.

Thanks, for your feedback!