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JWayman1-Visitor
1-Visitor
September 16, 2013
Question

Surface Blends

  • September 16, 2013
  • 13 replies
  • 8758 views
Hello,
I'm stuck on this wretched dome again!

I have a thin plastic dome - think of one of those white hard hats construction workers wear. All over the head part, it is nominally 5mm thick. Around the base, where it grazes the ears, it has a 50mm wide flange. The flange is at 45 degrees to the dome (so it partly covers the ears and partly obscures the vision). The flange is 15mm thick. The dome blends down to its nominal 5mm from the 15mm at the flange over a distance of 50mm.

I only have the data defining the outer surface of the dome/flange complete. I have modelled the inner surface of the head/dome by offsetting the outer surface by 5mm and the inner surface of the flange by offsetting the outer surface by 15mm.
I have then cut out the flange surface to leave the outline of the dome surface and cut off the outer edge of the dome surface to match the outline of the flange. They are modelled as surfaces, not solids. I therefore end up with two surface features, nestling one inside the other, with a 10mm gap between them around the flange/dome join.
Now I need to blend the two surfaces together.
I can't get Pro/E to do the blend.
I thought I could insert a blend, surface. project sec and select the two surfaces to blend between.
I get all the way through until the last few clicks, when I try to select the surfaces of the flange and of the dome and Pro/E decides that neither of them is a surface. I am left with the option of quitting out and starting again.

I am sorry, I can't attach the part, as it is confidential.

Have I explained it clearly enough to make sense? If so, have you any suggestions for alternative methods, or where I am going wrong with this one?

Thanks,


John

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13 replies

J
JWayman1-VisitorAuthor
1-Visitor
September 16, 2013
In order to make it easier to understand, I have modelled something similar, but not confidential.

WF4, by the way.

I have attached my model for your delight, when you are feeling bored and want a challenge! 🐵
Again, I tried to make a blend with projected sections and was unable to select either of my surfaces.
I am clearly missing something about these blends, but I can't see it. The help: I don't even understand the words, to be honest. It's like English, only different...


Any assistance would be greatly appreciated.

By the way, I think , in this case, I could use a VSS, but it's not such a simple shape in the real thing. I am unable to make a single, continuous curve around the real thing, and it is kind of blending from rectangular to elliptical, so it's not as simple as it looks, honest!


Thanks,

John


D
DeanLong1-Visitor
1-Visitor
September 17, 2013

John,


Here are a couple methods.



Cheers.



Dean

D
DamianCastillo1-Visitor
1-Visitor
September 17, 2013

Here is a video response on my YouTube channel.


Not sure if this is what you were asking, so let me know.


http://www.youtube.com/watch?v=338aCJI2BdE&feature=c4-overview&list=UU89vS9l-hjWue8YteZ56esA


ΜΟΛΩΝ ΛΑΒΕ

D
DamianCastillo1-Visitor
1-Visitor
September 17, 2013

John,


I realized that I did not look at all your layers to see the additinal surfaces you had. I created another video response just to make sure I covered how to blend these surfaces together.


Once again, I apologize if I still don't understand your question.


http://www.youtube.com/watch?v=kkgHPKwaff8&feature=c4-overview&list=UU89vS9l-hjWue8YteZ56esA


ΜΟΛΩΝ ΛΑΒΕ

J
JWayman1-VisitorAuthor
1-Visitor
September 23, 2013
Sorry to resume this topic, folks, but I am continuing to learn about surfaces this way.
I am still having trouble with my original surface blend. I can use a Boundary blend to join the two surface together, but Pro/E decides to add in some extraneous lumps & bumps along the way! If I look at the finished blend in wireframe, I can see squiggly lines that double back on themselves where I would expect only straight lines.



Squiggly lines:



[cid:image003.png@01CEB861.B6E03AD0]

Just one of the four corners of the real part, with its squiggly lines.



As an experiment, I created a picture frame (or something similar). It comprises a sketched datum curve in the shape of a rectangle on one datum plane and another rectangular sketched datum curve on another datum plane, parallel to but offset from the first plane

[cid:image001.png@01CEB85F.18A6C6B0]

If I create a Boundary Blend between the two curves, tangent to each curve, I get the thing shown above.
Again, I would expect straight lines like those in the top left and bottom right corners to describe the shape of the blended surface, but I see a pair of random-looking lines in each of the top right and bottom left corners.
They are not as squiggly as those in the real problem part, but this part is much more simple - it's planar, whilst the real part is curved around both the TOP/SIDE axis and the TOP/FRONT axis.

Can you explain to me why Pro/E puts in those two random-looking lines (I'm sure they are NOT random at all) instead of just joining all four corners of one sketch to the corresponding corners of the other sketch?

I tried creating curves between corresponding corners and using them as Direction 2 curves. That works as I would expect, but I can't make the resulting blend tangent to the two planes.
If, instead, I use the corner-to-corner curves as Influencing Curves, the thing will not regenerate with tangency.

I thought this was a pretty simple surfacing problem! I'm glad I don't have a hard one to sort out...

Any assistance gratefully received, as usual.


Thanks,


John

M
mapiskin11-Visitor
1-Visitor
September 23, 2013
Hi John,

There is a tab in the dashboard "Control Points".
Using this option, you can select the points in two rectangles to connect each other as you wish.
By this way you can prevent these random looking lines.

Sorry I can't add a screenshot. But it is easy to figure out how to proceed.
By the way I'm on WF4. In Creo the name in the dashboard may be different.

Hope this helps.

Mehmet Ali PISKIN

ASELSAN Inc.
MGEO IR Systems Design Department
Cankiri Yolu 7. km
Akyurt 06750
Ankara / TURKEY
+90 312 847 5300 / 4580

D
DaveClark1-Visitor
1-Visitor
September 23, 2013
Maybe this will help:

Under the control points tab of the boundary blend panel, there's a drop down list called "Fit". The default is Natural. There are options for Arc Length, and Piece to Piece. Piece to Piece only shows up when there are the EXACT same number of curves in each chain. This would create the edges you're looking for in your second image, where the corners would line up.

As to why Piece to Piece is not the default when using the same number of curves is a chain is beyond me.

I hope this helps a bit.

Dave Clark
Sr. CAD Application Engineer
Dukane Corporation
Intelligent Assembly Solutions Division
2900 Dukane Drive
St. Charles, IL 60174
630-797-4922 (Phone)
630-797-4949 (Fax)

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I
iceblink11-Visitor
1-Visitor
September 23, 2013
On 2013-09-23 14:35, WAYMAN John wrote:
> Sorry to resume this topic, folks, but I am continuing to learn about
> surfaces this way.
>
> I am still having trouble with my original surface blend. I can use a
> Boundary blend to join the two surface together, but Pro/E decides to
> add in some extraneous lumps & bumps along the way! If I look at the
> finished blend in wireframe, I can see squiggly lines that double
> back
> on themselves where I would expect only straight lines.
>
> Squiggly lines:
>
> Just one of the four corners of the real part, with its squiggly
> lines.
>
> As an experiment, I created a picture frame (or something similar).
> It comprises a sketched datum curve in the shape of a rectangle on
> one
> datum plane and another rectangular sketched datum curve on another
> datum plane, parallel to but offset from the first plane
>
> If I create a Boundary Blend between the two curves, tangent to each
> curve, I get the thing shown above.
>
> Again, I would expect straight lines like those in the top left and
> bottom right corners to describe the shape of the blended surface,
> but
> I see a pair of random-looking lines in each of the top right and
> bottom left corners.
>
> They are not as squiggly as those in the real problem part, but this
> part is much more simple - it's planar, whilst the real part is
> curved
> around both the TOP/SIDE axis and the TOP/FRONT axis.
>
> Can you explain to me why Pro/E puts in those two random-looking
> lines (I'm sure they are NOT random at all) instead of just joining
> all four corners of one sketch to the corresponding corners of the
> other sketch?
>
> I tried creating curves between corresponding corners and using them
> as Direction 2 curves. That works as I would expect, but I can't make
> the resulting blend tangent to the two planes.
>
> If, instead, I use the corner-to-corner curves as Influencing Curves,
> the thing will not regenerate with tangency.
>
> I thought this was a pretty simple surfacing problem! I'm glad I
> don't have a hard one to sort out…
>
> Any assistance gratefully received, as usual.
>
> Thanks,
>
> John

You will note that the 2 curves created by Pro/E start at each of the
corner points of the curves.
What Pro/E is doing, is taking the total length of each of the curves
you are using, and then create a surface by:
* taking a certain ratio of the total length of each curve
* create a point at that ratio on each curve
* create a curve connecting those two points
Of course all this is done below the hood, so you never get to see the
points and curves, *except* on certain spots like corner points in the
geometry, hence the two curves in the corner.
Half way in your surface, (ratio 0.5 on each of the curves), the two
virtual points created by Pro/E end up exactly on the corner point for
both line, so there you only get one line.

In this case, it seems like the product should be symmetric in two
directions. So the best thing to do would be to model only a quarter of
your current surface, and then mirror it in two directions. (Right now
your surface is not symmetric!)

That is my theory anyway.

Best regards,
Patrick Asselman

"Guns Are One Thing But Phone Calls Are Too Dangerous To Go Unchecked"
D
dgschaefer21-Topaz II
21-Topaz II
September 23, 2013
It looks like much of this was covered while I was typing.  It might still help, so I'm sending it on anyway. 😄

It's hard to see what's happening in your first image, but perhaps talking through the second will help you out.

First, I have no idea why Proe doesn't default to joining the corners, but it doesn't.  I'm sure there's a mathematical reason, but who knows.  There are a few things you can do to help.

One is look for the 'start' points on the curves. IN your rectangle image below it's the white dot.  They only show up for the curve that is currently selected.  Usually, but for some reason not always, you can drag it around the curve.  This can help in situations where the surface is twisting radically around between the curves.  Note the difference here from having that start point on the outer curve on the far right to the top:

[cid:image008.jpg@01CEB842.A1736650] [cid:image009.jpg@01CEB842.A1736650]

Second, you can control what points get connected under the 'Control Points' tab in the boundary blend dashboard.  There are drop down options there that change the way Proe calculates those surface breaks:

[cid:image007.png@01CEB841.AE665490]

If your two curves have the same number of segments, the piece to piece option forces the joint to line up.  Otherwise, you can explicitly tie pairs (or sets if you have more than 2 curves) together by clicking 'New set' and then clicking in the RH box to define the points.  The points on one curve highlight in open circles.  Click one of them and the points on the other curve highlight so you can pick the corresponding curve.

[cid:image010.png@01CEB842.4C24B730]

Hopefully that helps you work through the issues you're having.

--
D
DamianCastillo1-Visitor
1-Visitor
September 24, 2013

I think everyone's response should cover how to correct this.


Let me know if you want another short video on this. 🙂


ΜΟΛΩΝ ΛΑΒΕ

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