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  #1  
Old 11-23-2009, 02:06 AM
Anabolix Anabolix is offline
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TetraHedron

In Inventor it's easy to create a tetrahedron (Triangular based pyramid). I create a work plane, draw my equalateral triangle, draw an intersecting workplane; draw a line in the centre of the triangle and draw it up into 3D space. Create a work point and LOFT.

How do you do it without hacks in CoCreate? This must be a geometrically perfect tetrahedron, no hack maths etc...
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  #2  
Old 11-23-2009, 04:29 AM
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Mike Swartz Mike Swartz is offline
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Re: TetraHedron

At last, someone found a use for Inventor. It allows you to loft to a point. Lofting in CoCreate requires the same number of edges on each on each end of a loft.

So, you need a math "hack". (That's why there is a built in Calculator)
Create your triangle on a workplane. Then extrude with draft. Don't enter in an extrude distance. For the draft angle, open up the calculator. (I use the RPN calculator.) Enter 1/3, then hit ASin. The angle will be in the x register. select the x and the angle will populate the draft angle. Then, just drag the arrow on the screen up until you go past the intersection point. Hit enter.


By the way, you stated that, in Inventor, you created a work point that you lofted to. How did you determine the height of that work point?

Last edited by Mike Swartz; 11-23-2009 at 07:14 AM.
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  #3  
Old 11-23-2009, 08:44 AM
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Mike Swartz Mike Swartz is offline
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Re: TetraHedron

The absolute "no math" way to create a tetrahedron with a known edge length.
(you choose the edge length)

Adjust your catch settings so you can catch to all workplanes.

Create a workplane. Create a 2D horizontal line (anywhere on your workplane) to the desired edge-length. From the left end of the line, create a line (at an angle) The angle will be 60 deg, the length, is the desigered edge length.
Mirror this line to complete your base triangle.
Create a construction circle through the three points of your base triangle. Create a construction cross on the center of this circle.
Create a new workplane using point and direction. The point is the center of the construction circle, the direction is Positive "V" of your first workplane.
Create a vertical construction line at 0,0. Create a construction circle (center and radius) with the center of the circle located on the very first line you created, and the radius will be the point at the top of the first triangle. (you just calculated the height of your tetrahedron)

Open the 3D curve dialog box. Use the line command from Create Directly to create a line from the base of your first triangle to the intersection of the vertical construction line and the construction circle. Create 2 more 3D curves from each corner of the base triangle to that same point. (all of your curves can be added to the same curve part)

Open the surfacing dialog box and use the insert function to create a surface between each triangle. (all of your surfaces should be added to the same face part)

If you selected correctly, your surfaces will turn into a solid as soon as all the faces are completed.
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  #4  
Old 11-23-2009, 02:41 PM
Anabolix Anabolix is offline
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Re: TetraHedron

Thanks for that - I managed to create the tetrahedron but measurements were off slightly after it was created. How do you get the centrepoint of the circle to be the same plane as W1? If i start at 0,0 it's actually under the first workplane.

I appreciate the response - I wish it was as easy as lofting to a work point. Gah!
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  #5  
Old 11-24-2009, 06:38 AM
Gary Brauch Gary Brauch is offline
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Re: TetraHedron

Like Mike asked, how did you figure where the point was that you lofted to?
Put your second workplane on using that same method if you feel more comfortable doing it that way.

His first solution is extremely easy. Can't quite understand how lofting could be easier than that.
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  #6  
Old 11-24-2009, 11:43 AM
Anabolix Anabolix is offline
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Re: TetraHedron

Admittedly i missed the first method ;-)

To answer your question about how i did it in inventor. Create the triangle, create a workplane extending up into 3d space, create a single line from the centre of the triangle. Then create another workplane from the corner of one intersection at an angle equal to the angle of the existing 2d triangle. Where it intersects the centre line. That's the work point.

Another way is to create an arc measuring twice the distance of the triangle, and revolve it 90degrees. Create a workplane at the very top. That's your point.
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  #7  
Old 11-25-2009, 11:07 AM
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Mike Swartz Mike Swartz is offline
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Re: TetraHedron

If your numbers do not come out correctly, look to your catch settings. In particular, make sure your catch is set to allow you to select from all workplanes. You may think you are selecting something, but in reality, you may be just close.

When it comes to creating the second workplane, Use the point and direction method. For your point, select the center of the very first line you created. (catch must be set to center) For the direction, put your cursor over the base line of your triangle on the first workplane, and the 3D Copilot will display your direction options. Pick the direction running towards you along your base line. Then, when you create your construction circle and the vertical construction line that will give you your intersection point, remember that the catch must be set to allow you to select objects from all workplanes.

Here is a tip to help you with Catch settings. Note that there are three types of catches. Next Catch, Default 2D and Default 3D. These settings will change depending on what functions you are using. Changing the Next Catch setting is a one time only setting. If you want to change a Catch setting and have that setting remembered, you must change it in the Default 2D or the Default 3D mode, then the Next Catch will pick up this new setting.

Another tip. To make catching to the center of elements easy, use the keyboard shortcut <shift><ctrl> select, which will change Next Catch to center.
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  #8  
Old 11-26-2009, 12:11 AM
Anabolix Anabolix is offline
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Re: TetraHedron

Thanks for that; excellent tips. I successfully created one perfect tetrahedron using this method. Kind of easier than Inventor even! ;-)
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  #9  
Old 12-22-2009, 07:20 PM
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Lim Chee Beng Lim Chee Beng is offline
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Re: TetraHedron

Quote:
Originally Posted by Mike Swartz View Post
....Open the surfacing dialog box and use the insert function to create a surface between each triangle. (all of your surfaces should be added to the same face part)

If you selected correctly, your surfaces will turn into a solid as soon as all the faces are completed....
Instead of inserting 4 surfaces from the 3d lines, is there a single command to construct a solid part directly from the confined volume of the 3d edges?
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  #10  
Old 12-28-2009, 04:46 AM
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Re: TetraHedron

Yes

If you have 3d edges, use the surfacing command "insert" you do not need a surfacing lincense for this.

Select the command, pick the 3 edges that make once face, a face is created.

Continue on to the other 3 faces. When all 4 faces are created, the part becomes a solid.
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  #11  
Old 12-28-2009, 06:28 AM
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Lim Chee Beng Lim Chee Beng is offline
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Re: TetraHedron

Tom, thanks for reply.
I was just curious whether there is a single command, something like "solidify". User just needs to run the "solidify" command and then select the 4 joined edges and [enter] to complete. So there are only ~6 clicks to form the tetrahedron, instead of >20 clicks using 4x insert command.
Sorry for ambiguous question.
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  #12  
Old 12-28-2009, 08:42 AM
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Mike Swartz Mike Swartz is offline
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Re: TetraHedron

Sorry, there is no "solidify" function.
For minimum mouse clicks, I would skip the entire 3D curve thing, and just use the "Extrude with draft" solution I suggested in the second post of this thread.
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