Hello Frank,
Ya, I mean that's what I thought because I spent like hours trying to comb through options to see if I could isolate this curve. But thinking about it now, you are right, sketcher only uses planar dimensions then extrusions and more comples shapes can be pulled from that. But here's the thing, I really don't understand how ProE can be so good if you can only sketch in planar form. What if I'm pulling geometry off of an organic shape that has curves that flow through 3D space...how is this done, sketching in planar to try to achieve that very precise organic shape must be a nightmare if not impossible. Basically, I'm trying to create siderails for a motorcycle frame, they are basically organic in shape, at a certain sections they curve in 3d. I also need to adhere to precise dimensions being pulled from real life, i.e motor clearance etc. I know of about 3-4 ways I could accomplish this with ProE but it's all the basic stuff, making tons of datum planes or making small parts in 2d and then welding them together. That's all easy to do, But I want to make my core lines in 3d then build off of that. What program can I do that with? I'll save proe for smaller 2d parts like brackets, mounts etc.
I understand I could also use the CurveID's to build from while in part mode but there are usually referencing surfaces associated with their creation that get in the way, I just want a nice simple, accurately measured 3D line to sculpt from.
If you look at the picture I've attached, I'm trying to make lines for the main "side rails" or perimeter beams in the frame similar to that of a CR125 dirtbike. Starting from the bottom they move up, fairly flat but then dip in for leg clearance and buldge back out where the gas tank sits, Very organic and shaply. I need to be able to draw lines that will let me build a similar geometry, but very accurately to measured spec. I know that if I could get atleast two main 3d trajectory lines in there, I could build a chain, although difficult to form most the rail by doing a boundary blend. But I can't figure out how to make these first two initial lines through 3D space. I can't just throw it into "styling" to stretch and pull a 2D sketch, it needs to be sketched with accuracy. Any tips, suggestions?
Do you have the frame in CAD already? This is actually pretty easy with an Offset onto the surface.
This command allows you create a 2D sketch on a plane, but the feature is projected onto the curved surface and the thickness is applied to the selected face for a consistent thickness. Pretty cool!
The attached is a Creo 2.0 version of the part file roughly similar to the OP's request...
Hi Tom!
Great to get some more input from others aswell! No, no part file, otherwise I would use it as referrence but if you search CR125 frame on google, there are plenty of pictures and references to base a design plan. I like Honda's frame design, the split frame concept, and I'm using their design as the basis for my own. Hopefully if I ever produce any I won't run into patent issues )
Anyhoo.
Oh ofcourse, I'm familiar with the offset option, but think about it, you need to first create the curved surface on which to throw the offset sketch. I will definately need to use this feature later as I will need to "carve" out pockets through out the siderails for weight reduction etc. If you notice in the pictures of the frame above, on the inside of the lower part of the siderails, it's pocketed for weight reduction. That's a perfect candidate for the offset feature. The part is probably die cast or sand cast. Atleast that lower section.
You see, I'm really leaning towards sculpting the side rails using a swept blend along a tradjectory line, hopefully it will give me enough control in creating the shape of the entire siderail, the part thickens in area's, changes shape and dimension, it's really complicated but not impossible, with each sketch I can tweak the shape and keep dimensions accurate. I'll plan to have perhaps 20 or so sketches for the whole rail, positioned about every 2" along the trajectory line. Does anyone see any complications with this? suggestions?
Here's a very rough example of how far I've come with this method. Keep in mind, the sketches I used were just rediculously quick hidious things just to prove concept and see what kind of shapes came out. I think there are about 4 sketches in total, about 10 entities each. I was even able to experiment with offset to make pocketing (circled in green). Again, just proving concepts at the moment and pre-thinking the design steps...
the more feedback, the better!
Top down means you can reference features in your assembly to create your model. And yes, a sort of skeleton that you can use for references in your piece parts.
When you have -say- 3 parts in an assembly and you click on one of the parts (try the last one as it is order dependent) and select Activate. You are now editing the part, not the assembly. Create a new sketch and create dimensions to a different part in the assembly. That "part" sketch is now dependant on the assembly.
of course, this can get you in a whole lot of trouble too 
Many companies have policies forbidding this kind of practice. But properly done, it can be a really powerful tool.
