Need help on multisection student project

3D Design
1

 

Good evening, I need help with a student project,

 

this project is due in April and consists of modeling a turbocharger on CATIA V5R19. The volume modeling is not a problem for me but the spiral part has to be done in surface and that's where the problem lies.

 

To create this spiral, several sections are given to us in the technical drawings above, so I created splines by connecting the vertices of each section to make guide curves and then used the multisection function.

 

After several tries, I think I understand what to do:

 

- 2 multisections: a 1st one grouping all the rectangular sections and a 2nd connecting the last rectangular section (M section) to a circular sketch that ends the spiral by returning to the plate.

- Variable fillet of 8mm with a circular sketch that gradually decreases to 3 mm on the rectangular section K. So I use a variable fillet on the surface part (the result doesn't work when applied directly to the solid)

- 2.5 mm thick surface towards the outside;

 

However, I can't apply this approach correctly (imagining that, already, it's the right solution):

 

 

- I don't understand how to correctly place points on a circular sketch to make the guide curves pass through it. I place them in my room arbitrarily.


- I can't get a tangency between my 2 multisections, yet the guide curves of my 2nd multisection are tangent to the edges of the 1st multisection.

 

- I don't see how to complete the spiral, at the part opposite the circular sketch. I tried to use sweeps by taking parts of the previous guide curves but the result was bad.

 

 

I'm looking for any advice on these steps because I've been totally stuck on them for several nights already.

in advance, thank you!

 


volute.catpart
2

Hello, the principle for a multi-section scan is to have the same number of segments for each section.
What I advise you to do is to cut your circle into 4 arcs of a circle so that you can pass with a single multi section and therefore this should solve your PB of continuities and placement of points on the circle.

EDIT: To ensure continuity with the variable radius you can cut the circle into 8

3 Likes
3

Thank you for your quick answer,

I went back to my piece by applying that. I had already tried a few evenings ago to do it with a single multisection but I didn't like the result, I should have tried with + guide curves.

Any idea of how to make the end of the spiral that wraps around itself?

4

Hello can you attach the photos of the plans, I think that the two vertical walls of the spiral come together at the intersection of the LL section and the height of the horizontal walls at 18 mm but I can't see very well on the images of the forum.

5

Good evening

Attached are the plans,

I had tried on my side by making an explicit scan of the sketch of the K section following guide curves stopping in the sketch of the L section. It gives a correct result to the visual but the scan fits into the multisection which is supposed to remain hollow and there is no tangency between multisection and scan at the level of the K sketch.

 


img_20210224_175112-converti1.pdf
6

Good evening I'm starting a long weekend so I'll have your answer that on Monday I looked at the pdf and I don't see how you got the angle of 135° for the M-M cut and the dimension of 34.25 // at the winding axis?
I think rather that in view from above the winding connects in tangency with a center circle (the point of construction of the M-M section).
This way we get an intersection between the two curves see red circle.
I could be wrong.

7

Good evening and thank you Franck,

- For the 135° angle, it was during the creation of all my plans for the sketches of the multisection where I relied on the B-B cross-section view of the tech drawing. With the angle of 18.3° of the section F-F with respect to the horizontal axis, we can easily deduce all the other sections that are placed at 90° from each other. For the M-M cut and its 135°, I simply used my protractor on the technical drawing. The front view, where the M-M cut is visible in the identical location of my CATIA model, confirms its good positioning (even if I would have preferred to find it other than by gluing my protractor to the tech drawing).

 

- For the dimension of 34.25, we must first look at the C-C section of the front view: we observe the intersection between the plane of the M-M section (shown but not indicated) and the section, followed by the inside of the spiral. Looking at the view of the C-C section next, we notice that this intersection corresponds to the surface Ø 68.5. By aligning the 2 views and drawing a line (again, having the plans physically helped me a lot) we can see that the intersection is on the surface at this diameter.

 

I'm going to investigate this tangency that you found and that I had completely missed, I'll edit this post if I manage to move forward

EDIT: I redid this tangency that you put in your 2nd photo but I don't understand how to use it to have the spiral winding.

8

Hello, I'm coming back to your dimension of 34.25, the approach seems coherent because from my point of view there is a lack of information to correctly place the section and the sketch M without making the assumptions you made.

On the other hand, in your sketch you dimension a 34.25 from the center (projected) outside the dimension of 34.25 and to be placed along the axis of the C-C section  see screenshots.

Edit: this allows you to draw the axis of the M-M  section between two points X-79; Y -45 and X -34.25 Y 0 (but that gives an angle of 135.16) it would have been easier if he had put the dimension, from my point of view I don't like rounding I would have tandence to stay on 135°.

Re edit :

 

1 Like
9

Good evening Franck,

Thank you very much for the help you have given me and the time you have devoted to this subject,

I'm going to close the discussion because I have too little time to devote to this almost finished turbo while I have other homework and especially a learning report that no longer advances in parallel.

Good luck