How to subtract a rectangle from a box in HFSS?

[wickedweasel]

how to do "subtraction" in HFSS -need help for master thesis

I need to open a hole to a box.
My aim is to make a slot in a waveguide.
Unfortunately everytime it says "Invalid body types combination found in substract operation"
So I can not proceed to my project.
I have tried to do the subtraction both as "face" and "object".
no result!
can anyone tell me how to subtract a rectangle from a box?

 

[cd79]

Re: need HFSS trick

You cannot subtract a rectangle from a box. A rectangle is twodimensional, but a box is 3D. The problem depends on your design, upload the .hfss-file then I can check.

 

[wickedweasel]

Re: need HFSS trick

Dear cd79,

Thank you very much for your reply.
It will be great if look at my file and explain me how to open a rectangular hole on the box.

Regards

 

[cd79]

Re: need HFSS trick

Now let me guess:
You want to create a waveguide with perfectly conducting walls and vacuum inside.
The easiest way to create this in HFSS is the following:
1. Create a box of vacuum with the size of the waveguide.
2. Set waveports at the sides where the wave should go in and come out.
3. Define all other sides as perfectly conducting boundary. (this is done automacially to all outsides of the modell)

To cut a part out of the boundary condition you have to use a trick. Install a short waveguide and set the correct boundary condition. See the file, I tryed one thing, should work, but you need to check the dimensions. I didn't calculate any modes.

Check out the T-Junction Tutorial, It should explain most of what you are doing.

 

[wickedweasel]

Re: need HFSS trick

Dear CD79,

Thank you very much for your helping me.

When I try to open your file, it says its locked.
So I was not able to open and examine it.
I am using HFSS 9.1.
How can I open your file?

Regards

 

[cd79]

Re: need HFSS trick

I use Version 10, thats why you couldn't open the file.
I made it again with Version 9.2.1, you should be able to open it now.

 

[wickedweasel]

Re: need HFSS trick

Dear cd79,

Finally I was able to open the file and investigated it.
I understand what you mean, but how do you think to adjust the bounderies of the inside sides of the little box?
we must make them vacuum too, unfortunately that option does not exist in the bounday list.

By the way, I have tried to build the waveguide from rectangles instead of boxes.
This time I get "solve inside does not exist"

I am really in a bad situation now, because I can not build a waveguide with a slot on it.

Regards

Yavuz

 

[cd79]

Re: need HFSS trick

There is a big box of vacuum with a small box of vacuum inside. There is no boundary defined between them, so they behave like one box.

You made a waveguide from rectangles? Of course you cannot solve inside, because you didn't define the space inside.

Are you sure, you know how a waveguide works? First you must really understand the physics. Be sure to know what a boundary condition is. It is complete nonsense to define a boundary as a material.
Did you make it through the T-junction tutorial? It should help you to understand how to implement waveguides in HFSS. Remember (see the help): undefined boundary at the model edges are set to Perf_E by default.

And think about this: Undefined space in HFSS is really undefined. It is not air or infinity or something. You must define every relevant space and boundary.

Good luck! By the way, where are you from?

 

[wickedweasel]

need HFSS trick

dear cd,

thank you very much 4 your help.
I was able to do the simulation it is working now.
There is another problem now - i expect it is last- i need to put a material inside the microwave oven (like a potatoe) to absorb the energy.
What material do you suggest me?

 

[cd79]

Re: need HFSS trick

HFSS 9.2 Tutorial No. 5: Microwave Heating

This Tutorial includes the modelling of potatos and pizza. Or at least their electrical properties. On the ansoft support homepage you can download all the Tutorials, just search for "Tutorial". They appear on the first page: 2004-10-18 HFSS Training tutorials

I added the pdf of No.5 to this post. You will find the potato properties on pages 5 and 6.

 

[wickedweasel]

Re: need HFSS trick

u r great
let me check and i will let u know
thx a lot