Compound Blend
Compound Blend
(OP)
I am modeling a compressor blade in NX4. The blade calls for a "compound" or "eliptical" blend between the airfoil and platform. This means a small radius blend grows into a large radius blend between the two surfaces.
This is different from a variable blend where the user can select points along the edge and specify a radius.
Does anyone know how to do this?
This is different from a variable blend where the user can select points along the edge and specify a radius.
Does anyone know how to do this?





RE: Compound Blend
The documentation should help you with all the options on the dialog.
Tim Flater
Senior Designer
Enkei America, Inc.
www.enkei.com
Some people are like slinkies....they don't really have a purpose, but they still bring a smile to your face when you push them down the stairs.
RE: Compound Blend
Cheers
Hudson
RE: Compound Blend
It will do the job but when using that you will need to specify the tangent edges of the blend - sometimes they are easily put in with curves (and sometimes not so easy).
RE: Compound Blend
If you look in the help files, it was designed primarily for turbine blades.
-Dave
Everything should be designed as simple as possible, but not simpler.
RE: Compound Blend
This topic was discussed there.
RE: Compound Blend
It looks like the conic face blend is the way to go, but it can't wrap around the airfoil's leading edge. The blend fails here.
Gunman: I see FACE-BLEND... ISOPARAMETER in the help files, but I don't see it in my menus/toolbars. Is this in MODELING or another application?
Soft blend is an option, but I haven't given up on face blend yet. The advantage to face blend is that the model will be defined by the actual dimensions on the print.
TurbBLD: thanks for showing me the other thread. I swear I searched before posting. I never found this one.
RE: Compound Blend
I'll try to explain.
When you apply a true radius blend using edge blend with say a smaller blend on the leading edge and a larger one on the tip then the software will create a three sided face on the corner. It is as if the larger blend were applied first and the smaller created later on. Try it with the edges of a cube for example and you'll see what I mean.
In face blend the true radius geometric equivalent of the edge blend is termed spherical. That relates to the application of the blend as if it were a rolling ball contact swept between the two faces. The three sided faces you get from edge blends are in fact trimmed spheres, so that is a unique case.
This was historically a problem that required careful ordering of blends in earlier versions of UG. The software has become a little smarter but the range of possible geometry still falls within the same practical limits.
Conical blends pretty much always want to be able to produce four sided faces. In all but a few geometric types, spheres, planes, cylinders and cones, surfaces are described as basically U and V meshes. This can mean that the absence of a fourth side or any condition approaching a focal point where the side becomes too short will be at risk of self intersection. You will almost certainly be facing such a dilemma.
I doubt that you'll be able to achieve the exact result you expected in that case, but I haven't seen your part, so in order to know you'll need to look at the faces with some face analysis tools. In this case using face analysis>radius analysis should tell you what you need to know. I would use minimum radius method, but if the surface is complex try analysing just the U or V direction depending on which way the mesh runs. Select just the face on the leading edge where it won't wrap around to analyse and adjust the range to get a sense of how tight the curvature is at its minimum radius.
You may want to create the conical face blend without trim and attach so that it builds what it can of the surface. Then you can also use that in analysis to compare with your leading edge observations.
You may succeed if you vary either the size of the conic or the amount of blend setback to the tangents. Otherwise it is up to you whether you choose to vary the leading edge geometry or simply build a mesh surface that nearly enough approximates your desired result, and attempt to apply the result as a sew and patch.
Good luck with it.
Hudson
RE: Compound Blend
After monkeying around with this, I stumbled on a "solution".
The platform at the base of the airfoil is cylindrical, so I had modeled it as a cylinder, to be trimmed later.
For some reason, the face blend could not work with this cylinder. (I think it has to do with the Normal Direction arrow appearing at the bottom of that cylinder face - 180° from where the airfoil is). However, if I only used a partial cylinder there was no problem at all. The attached picture should clarify.
I guess this is just one of those NX quirks.
Thanks again to all who helped. I will refer to this thread in the future.
RE: Compound Blend
Just a tip to mention that a smaller Jpeg image would have done nicely.
Cheers
Hudson