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variable section sweep

2

2ms1

New member
Could someone tell me what I'm doing wrong here? When I try to click the little sketcher button (pencil on paper icon) in variable section sweep dashboard in order to sketch the third curve(the one to connect the origin with the start of x curve, the sketcher just doesn't open. Nothing happens.


View attachment 4104





View attachment 4105
Edited by: 2ms1
 
It has to do with your features orientation at the start of the sweep which from your picture is the one with the arrow and the N box checked off in the references list. If you create a plane Normal to and at the arrow side of the origin trajectory, it will fail to intersect the curve chosen as your X-Trajectory. This feature seems to be more of a boundary blend feature.

You may be able to get into the sketch by extending the end of the x trajectory curve nearest to the origin until it intersects the plane you will be using for your origin trajectory. Once it intersects you will be allowed into sketcher. The Variable Section Sweep has a pretty strict "Bouncer" if you will and it doesn't take bribes.

Another method to use is to sketch another trajectory to use as your Normal To Trajectory this curve would be normal to what looks like the flat back face of your part and would then match the curvature of the origin trajectory near the end or just be a straight line.

Try this out Monday or Tomorrow since it's a student edition. I also might be able to send you a file created on my WF2 Student Edition WF2SE that you can look at.

Michael
2007-09-07_231651_geo-shapes_equilateral_triangle_piece.jpg
 
I can't see anything wrong. What Michael said about the sketch plane not intersecting the chain-1 isn't strictly true. What will happen is that the initial placement of the sketch plane will happen at the first location along the origin that also includes the start point of chain-1.

vss3.png
 
yeah, I'm beginning to see that. As I say, I'm brand new to surfacing. The thing is that the surface like mine that you see in thetwo images in my last post was created with a VSS. The pics are from a tutorial. So I figured there must have been a reason he chose that method rather than curves and a boundary surface.


Maybe you can answer me a larger question: when do you use VSS and when do you use boundary surface?
 
I think that frotime tutorial you are looking at was created from one of my tutorials from 1997. That is a question you answer when looking at the example.


Edited by: design-engine
 
I went back and read through the whole tutorial again and about all it explicitly said was that VSS are ruled surfaces so they are higher quality than blends. It didn't say anything else about when not to use them or anything else about when to use them versus boundary blends. I am completely baffled as to why this VSS won't work. It makes no sense and I seem to have tried everything. Dammit it's frustrating that spent like 10 hours or something changing little things trying to get it to work but still it doesn't and I don't think I've learned anything. I mean, I'm moving on out of necessity and going to try boundary blend...I just wish I could've at least had some "closure" :)
 
http://gkb.servehttp.com/parts/tip3x/

Here's the solution.
One: Sketch 10 has more than one open loop. Selecting it as a feature will cause the sketch icon of the VSS to fail.

Two: That doesn't have to be a problem if the desired portion of Sketch 10 is query selected.

Three: If Sketch 8 is set to control the sketch normal plane, the
orientation of the sketch at the beginning and end of the sweep,
especially at the nose, almost fails to intersect sketch 10.

notes.png
 
drats Glenn.... WF3se not WF2se
smiley2.gif



and .... dem bones are looking much more rectangular then I would think, seems that pacman would be a little less circular....


2ms1...Isn't there some plan later down the road to connect all this in mechanism?
 
I took gkbeer's suggestions and indeed came up with a successful protrusion. The only problem is that it isn't capturing the rounding top to bone that I was hoping to achieve. I was basically hoping to use the sweep to accomplish something like a classic round to get rid of the rectilinearity. The reason I can't use rounds is that then the "pacman" wouldn't be part of the same roundedness across entire top of bone that you see in the original pictures of what I'm trying to emulate.


I tried using a different x trajectory - a diagonal line - in an effort to bring the rounded curve inas the protrustion travels down the curve but as you can see in the second picture that didn't accomplish anything -- still rectilinear rather than rounded top of bone.


I feel like having the protrusion be normal to origin trajectory might give me what I want, but that's what I can't get the sketcher to open in.
smiley35.gif



Any more ideas?


View attachment 4135





View attachment 4136
Edited by: 2ms1
 
Several people have already given you the only good idea & that is to use either boundary blend or ISDX.
 
View attachment 4145

This is what I was originally talking about Norm 2 Traj but not the Origin Trajectory notice the check mark for N or Normal is on the Chain 2 straight line reference.

Or you can use the constant normal and pick a plane that specifies the normal for your feature or parallel to your sketched section.

Michael


Edited by: mjcole_ptc
 
mjcole what you made looks great. I tried doing it though and it still won't work. I can't believe it. Any last thoughts from anyone on whythe failureyou see below might be the case? I really would like to know why in the hell this VSS just won't get a green check mark.Unless anyone has any morelast second ideas Iguess I'm just going to shelf this part and/or settle for something crude because the curves won't work with boundary blend either :( Thanks for all the advice though, I've learned a lot.


(Notice the grayed out preview and green check buttons)


View attachment 4146





View attachment 4147
Edited by: 2ms1
 
2ms

Your Chain 2 is wrong and is what's causing problems (it's parallel to your sketch section) check the images you posted vs mine. I believe you were stuck in the Boundary Blend methodology. The chain 2 I showed is highlighted red and is a straight line. Here is an image of the constant normal option, The chain 2 is not even required for this option so instead of re-sketching it you can just remove the reference.
View attachment 4148

Here's the section spline by two points and tangency driven.
View attachment 4149

Michael
 
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