How can I scale() right with linear_extrude() ?

On Apr 2, 2021, at 9:42 PM, infocean via Discuss <[hidden email]> wrote:

Hmm...  I replied to this message on March 27 or 28, but looks like it was deleted from the forum although I .

tcdistx = 10.5;
tcdistz = 0;
tcheight = 8;
hacdist = 12.5;
iwdiamo11 = 16;
haddist = 12.5;
haddiamo = 3;

Here are some pictures for illustrations of the my problem

A. scale=[1,1], that is no scaling

From the side:
Screen_Shot_2021-03-27_at_8.png

from the back:
Screen_Shot_2021-03-27_at_8.png


B.  scale=[1,0.3]

From the side:
Screen_Shot_2021-03-27_at_8.png

from the back:
Screen_Shot_2021-03-27_at_8.png
As you can see the scaling was not at the bigger pipe, but at the smaller one and it was radial, that is y-direction.


C. scale=[0.3,1]

From the side:
Screen_Shot_2021-03-27_at_8.png

From the back:
Screen_Shot_2021-03-27_at_8.png

In this last case the scaling was again at the small pipe and in the x-direction.

What I need is an y-direction scale down at the big pipe.  To create these images of course other modules are involved to draw the big pipe and the small pipe, but they have no effect on the scaling.

Thanks ahead,
Infocean
P.S. OpenSCAD does not allow extruding to negative z-direction.  Interestingly, negative’s scaling is allowed. ;-)

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On Apr 3, 2021, at 10:26 AM, (null) (null) via Discuss <[hidden email]> wrote:

On Apr 3, 2021, at 2:22 AM, Hugo Jackson <[hidden email]> wrote:

Hello again…

Thanks for supplying the variables and now i’m a little confused as the render your code produces seems to have no relevance to connecting pipes. :)

Also, all the images you provided were the same image so they didn’t provide me with any greater insight into what you’re trying to accomplish.

Your code produced this:

<Screen Shot 2021-04-02 at 11.16.56 PM.png>

All your pictures were this single image.

Well, Looks like the forum interface messed it up.  Now I am sending the images from my computer via email.

A. scale=[1,1], that is no scaling

From the side:

<Screen Shot 2021-03-27 at 8.54.47 PM.png>

From the back:

<Screen Shot 2021-03-27 at 8.55.01 PM.png>

B.  scale=[1,0.3]

From the side:

<Screen Shot 2021-03-27 at 8.55.50 PM.png>

From the back:

<Screen Shot 2021-03-27 at 8.56.04 PM.png>

As you can see the scaling was not at the bigger pipe, but at the smaller one and it was radial, that is y-direction.

C. scale=[0.3,1]

From the side:

<Screen Shot 2021-03-27 at 8.56.53 PM.png>

From the back:

<Screen Shot 2021-03-27 at 8.57.08 PM.png>

In this last case the scaling was again at the small pipe and in the x-direction.

What I need is an y-direction scale down at the big pipe.  To create these images of course other modules are involved to draw the big pipe and the small pipe, but they have no effect on the scaling.

Thanks ahead,

János

P.S. OpenSCAD does not allow extruding to negative z-direction.  Interestingly, negative’s scaling is allowed. ;-)

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On Apr 4, 2021, at 10:30 AM, Jordan Brown <[hidden email]> wrote:

I'm happy to try to help, but I'm having trouble understanding what you're trying to do and what the problem is.

Probably the best first step is to eliminate unnecessary complexity from the discussion.  When asking a question in any forum, that's a good first step:  isolate the problem down to the thing that you're having trouble with, so that your readers won't have to try to understand parts of the example that aren't really parts of the question.

You say "the first linear_extrude is the culprit".  That's:

tcheight = 8;
linear_extrude(tcheight,center=true,convexity=10,scale=[0.11,1])
    difference() { 
        square([7,3],true); 
        square([6.5,2.5],true);
    }

which produces:

<bhcdhmonkehdifeg.png>

I'm not understanding what you mean by "the radial direction" and "the axial direction".  Can we talk about X, Y, and Z in this picture?

You've got it set up so that the top and bottom are the same size in Y, but the top is smaller in X.  That's what the "scale=[0.11, 1]" means.

Is the bottom of this object the shape that you want, a hollow rectangle with outside dimensions [7, 3] and inside dimensions [6.5, 2.5]?

Is the top of the object the shape that you want, a hollow rectangle with outside dimensions [0.77, 3] and inside dimensions [0.726, 2.5]?

I suspect that one problem is that the walls are scaled down in the X axis, so that they are 0.5 thick at the bottom and 0.055 thick at the top.

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On Apr 4, 2021, at 9:59 PM, jon <[hidden email]> wrote:

The three pictures all look the same to me.   Perhaps you can highlight the places you want us to look at??

Jon

On 4/4/2021 9:51 PM, (null) (null) via Discuss wrote:

Hi Jordan,

Maybe showing the parts in  axiometric will make clear what is my problem.  So, here is 3 pictures.  

On the first one the scaling is 1,1

<Screen Shot 2021-04-04 at 9.35.23 PM.png>

As you can see there are 4 smaller diameter pipes connecting to the bigger pipe in a slanted way.  The width of the connectors along the x-axis is constant and their thickness is also and about the same as the diameter of the small pipes at the location of the connector..

On the second one scaling is 0.3,1

<Screen Shot 2021-04-04 at 9.34.16 PM.png>

Here the width, x-direction, is reduced at the small pipes.  The thickness remained constant.

On the third one the scaling is 1,0.3

<Screen Shot 2021-04-04 at 9.34.54 PM.png>

Here the x-directional width remained the same as on the firs picture, but the thickness, again at the small pipe was reduced.

I want the width remain the same and the thickness be reduced at the big pipe.

I hope now it is clear.  I do not know how to scale that way with linear_extrude.

Thanks ahead,

Infocean

On Apr 4, 2021, at 10:30 AM, Jordan Brown <[hidden email]> wrote:

I'm happy to try to help, but I'm having trouble understanding what you're trying to do and what the problem is.

Probably the best first step is to eliminate unnecessary complexity from the discussion.  When asking a question in any forum, that's a good first step:  isolate the problem down to the thing that you're having trouble with, so that your readers won't have to try to understand parts of the example that aren't really parts of the question.

You say "the first linear_extrude is the culprit".  That's:

tcheight = 8;
linear_extrude(tcheight,center=true,convexity=10,scale=[0.11,1])
    difference() { 
        square([7,3],true); 
        square([6.5,2.5],true);
    }

which produces:

<bhcdhmonkehdifeg.png>

I'm not understanding what you mean by "the radial direction" and "the axial direction".  Can we talk about X, Y, and Z in this picture?

You've got it set up so that the top and bottom are the same size in Y, but the top is smaller in X.  That's what the "scale=[0.11, 1]" means.

Is the bottom of this object the shape that you want, a hollow rectangle with outside dimensions [7, 3] and inside dimensions [6.5, 2.5]?

Is the top of the object the shape that you want, a hollow rectangle with outside dimensions [0.77, 3] and inside dimensions [0.726, 2.5]?

I suspect that one problem is that the walls are scaled down in the X axis, so that they are 0.5 thick at the bottom and 0.055 thick at the top.

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