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Hi

Its correct that (3.5a) if you make a 2D view and add triangles, sqares or circles, then you can extrude them into 3D, by also adding X-Y displacements, twists, and scaling, but no Z taper that you would need to make directly pyramids.

Could be worht a suggestion for COMSOL support though ;)

The only way around I see, is to make your pyramid in 3D by two bolean "-" operations on a solids cube (or via matlab), and then make an array of these if you need some periodic apperance

Have fun Comsoling
Ivar

Thank you for your reply. I get the impression this is a little tricky!

Could you please explain in a little detail what you mean by 'two bolean "-" operations on a solids cube'. I want to end up with a triangular-based pyramid, I think what you're suggesting would result in a square-based pyramid.

Thank you for your help.

In COMSOL Multiphysics 4.0 you can create tetrahedra (triangle-based pyramids) and pyramids (with a square base) conveniently as 3D primitives.

Magnus Ringh, COMSOL AB

Hi

here is a procedure in 3.5 (as Magnus said in V4 there are far more geometry possibilities):

"Select 3D OK"
"Create a cube - OK" (I use for this demo default 1[m])
"Draw - Workplane settings - Quick tab - Z-X at Y=0 - APPLY - (check view) - OK"
Select Geom2
"Rescale - Draw line from (0,0), (1,0.5) (1,0) (0,0) right-click (note this is the Z-X plane by default)
"Mirror entity" Point:(0,0.5) Line:(0,1) OK
"Select all (Cntr-A) - Draw - Extrude 1[m] - OK)
Select Geom1
"Draw - Workplane settings - Quick tab - ADD (create Geom3) - Y-Z at X=0 - APPLY - (check view) - OK"
Select Geom3
"Rescale"
"Rescale - Draw line from (0,0), (0.5,1)) (0,1) (0,0) right-click
"Mirror entity" Point:(0.5,0) Line:(1,0) OK
"Select all (Cntr-A) - Draw - Extrude 1[m] - OK)
Select Geom1
"Select all - Create Composite Object - "BLK1-(EXT1+EXT2+EXT3+EXT4)" - OK"

there it is !


Have fun Comsoling
Ivar

Now I believe I have corrected fully ;) no, ineed recorrection better now

Thank you for getting back to me, but it doesn't seem to work quite right...

I think maybe there is an error in "Rescale - Draw line from (0,0), (0,0.5) (0,1) (0,0) right-click"?!

Hi

I tried to copy carefully my operations onto the text file, but as usual it's quickly done to type in an error, but normally you should understand the principle no ?

I'll try to repeat it agin in a moment, but just now my PC running COMSOL has frozen in the middle of a long calculations

Ivar

You vere perfectly right I mityped is (0.5,1), I have corrected above, thanks

Thanks for the correction. The line below the one you have corrected is also wrong, it should read...

"Mirror entity" Point:(0.5,0) Line:(1,0) OK

However this results in a square-based pyramid, and what I was after was a triangle-based pyramid!

Thank you for all your help.

Hi

yes agin your are right, its corrected, thanks
Ivar

Hi,

I would like to make a groove structure - a triangle with circular tip (angle and radius given) in 2D. I'm using COMSOL 4.0a. Can u help me how I can draw this ?

thanks in advance !

Hi

For me I believe the simplest in 2D is to draw a triangle, as 3 connected lines, then select one point and apply a fillet of radius "r"

for 3D you can then extrude it to the length required, if you need 3D ;)

--
Good luck
Ivar

Hi,

Thanks. But whenever I apply fillet (with radius) the vertex goes up and I can't control the position. I want the vertex at, for example (0,0) position. Is it possible to fix it.

Hi

you are right that the vertex disappears when you create the fillet, and you do not even have a point, not even at the fillet centre, that you must add by hand, a bit more work. But a simple point in 2D that is floating around without being part of a boundary, will not be considered in the geometry, so you need to link it to the edge via a line

--
Good luck
Ivar

hello...
I tried to make a pyramid in 3D but in micrometer scale. They are showing some error like geometry error. Is it possible to make a pyramid in micron scale??