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Creating dished surfaces

A

andrewyair

New member
Can anyone offer me advice on the best way to create dished features in ProE? The image below hopefully shows what I want to achieve - I've cut a straight extruded hole through a fairly complex surface and I want to fill this with a recessed dimple.


View attachment 3760


What, in users' experience, is the best way to create this type of feature? I've always tended to go for boundary blends by creating a central curve to control the depth of the dish and creating a pair of semi-circular features as shown below:


View attachment 3761


However, even when adding a tangent constraint on the second feature, ProE creates a nasty 'pinch point' at one of the intersections as shown below:


View attachment 3762


This prevents the model from solidifying, as well as having obvious visual ramifications for the produced part. I've tried using a variable section sweep witheven less success(see below) and am a bit stuck for ideas so any help would be much appreciated.


View attachment 3763


Thanks, Andrew.
 
Forget the hole & justbuild the dish, then solidify or thicken to cut away.


If the dish is symmetrical, build one half & then mirror across a dividing datum.Project curves for the boundaries of the dish but make sure their ends are normal to the dividing datum Make sure you add normal constraints to the boundaries. And just to avoid any controversy, I must also mention that you use 3-sidedquilts at your own risk because of the degenerate edge, so you might want to edit it further to end up with a better surface.


View attachment 3767
 
Thanks for your reply mgnt8,


Unfortunately the dish isn't symmetrical, the top surface of the part is a free-form surface, so the curve that's projected onto it is fairly irregular as can hopefully be seen in the image below:


View attachment 3770


I've had a go at creating the feature as you suggest above, but I still get the 'pinch point' on one corner of the intersection of the two parts as before:


View attachment 3771


The other 'corner' is fine though, which perplexes me slightly...


Is there any way of creating the dish as a single feature to prevent there being any joint between the sections?


Thanks, Andrew.
 
I may be missing something, but why not revolve a surface in here? Build it out past the existing surface and soliidy...
 
Have managed to bodge it by running a smallvariable section sweep around the edge of the hole...


View attachment 3776


...and filling in the gap with a couple of boundary blends controlled by curves:


View attachment 3777


Bit of a messy solution, mind you, so if anyone has a cleaner way to do it I'd be very grateful for your suggestions.


Thanks, Andrew.
 
As you stated originally, "I've cut a straight extruded hole through..." OK then,forget about mirror, but...


If this dish is filling a true 'hole' than you should be able to place a datum plane at the center axis. Then build both'halves' with curves and surfaces as I suggested. The key is to constrain the ends of your outer boundary curves so they are normal to the center dividing datum. You don't have that condition now and it is resulting in the pinched edge.
 
Hi mgnt8,


Thanks for your response. I'm struggling to apply the constraints to the end of the boundary curves - here's what I'm doing:


View attachment 3781


1. Create datum plane through centre of hole.


View attachment 3782


2. Create sketched curve on datum plane through 'endpoints' of hole.


View attachment 3783


3. Create boundary blend with'normal' constraint on central datumto form first semi-circular dish.


View attachment 3784


4. Repeat process to produce second semi-circular cutout, adding the 'normal' constraint on the centreline again.


View attachment 3785


Witness the pinch point on one of the intersections.


Have tried messing about with influencing curves, but it only seems to make the situation worse...
 
Any chance you could post your part? I've created a couple that appear similar, but the blends are going right in...
 
There is another way to attack this one. I call it the toupee method. You can even use influencing curves to manipulate the geometry. Use a four part boundary to create a draping sheet then project an ellipse up to that surface and trim. The resulting area is built using only four part boundaries. I can post an example if anyone still cares.<?:namespace prefix = o ns = "urn:schemas-microsoft-com:eek:ffice:eek:ffice" />
 
Yeah,I'd like to see your solution.Just as importantly, I'd like to understand what is driving the surface to wrinkle like that. I thought a VSS would work, too, but it gets crazy in the middle. Can anyone enlighten us?
 
Glad it's not just me then! I'm still watching and hoping for a solution, so I'd be very interested to see Design-Engine's toupee method.


Cheers, Andrew.
 
After Lunch (3PMCST)I'll post a detailed solution or two.


BTW I partied with the guy who owns Rhino last week at a Fisher-Price round table. After one beer I start teasing eveyone for being married. I don't think he liked me much ;)


Rhino is for kids
Edited by: design-engine
 
These two examples. One using 3 part boundaries where there is some globing that occurs. and the other that uses the Toupee method where only four part boundaries occur.

scallup02.jpg

the completed scallop function.

scallup00.jpg

start out like this with a curve between to points connecting the ends of the egg shape. (not shown in this shot)


scallup03.jpg

Build the surface as a boundary blend with three curves on one direction and non in the second.

PROS: Quick... works every time....

CONS: Gets the globing effect however a designer can often justify this three part boundary plan of attach because he or she plans to add a radius to the model.

The zip file for both versions HERE.
 
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