transforming free form circular arrays. UG v17 1

[scrimy]

Hi,

Does anybody know of a way to generate an circular array of freeform features that is editable and can be moved within the model? E.g. to form involute gear teeth. A feature group has to be used including (say) a ruled and a unite, which can then be instanced. But when the geometry is moved the subsequent array is not transformed with the rest of the model and falls off! Even if the circular array is generated around a datum axis which IS transformed with the rest of the model.

Arrays of regular features can be moved at will but not free-forms. Most frustrating.

Am I missing something or is this a flaw within UG? I would be grateful of any solutions or insights somebody may have.

Yours faithfully,

Scrimy.

 

[looslib]

Go to the internal UG BBS. Search in the CAD conference on the word 'gear'. Look at the part file John Baker attached to a note in July 2000.
Ben Loosli
CAD/CAM System Analyst
Ingersoll-Rand

 

[scrimy]

Thanks for the response. What is the internal UG BBS? I shall check it out, it may be of assistance.

However, my main problem is with circular arrays of free form features for gear teeth or otherwise. In the example I gave I should have described it as involute bevel gear teeth, which I formed with a ruled between 2 scaled gear profiles then instanced around a central axis. Sorry about the omission, I realise it makes quite a difference.

Thanks again and please bring on any further ideas or suggestions,

Scrimy.

 

[looslib]

bbsnotes.ugsolutions.com

You will need a Webkey to access the site. You can get a Webkey if you know your site ID and Webkey password. Both of these are on the license file that UG sends to the system administrator at your site.


I guess my other question is: Why do them as free form features? You should be able to construct the shapes and extrude. Maybe I am wrong, but in my thinking, free form means surfaces, not solids. I realise that these can be sewn into solids but can you start with a sketch of the profile and then use extrude along a path to get the solid shape. Ben Loosli
CAD/CAM System Analyst
Ingersoll-Rand

 

[zilla74]

I have described below one method that I know of. I'm not sure if the article you were referred to mentions this but here goes:

Create your freefrom geometry in a seperate part file.

This part defines that exact freeform shape that you with to array.

In a new part file, that will be the actual part file, create the rest of the geometry without the freeform shape.

Using the assemblies tools of Unigraphics, add the freeform shape into the actual part file.

By doing this you can not position this shape exactly were you would like it by using mating conditions (very powerful).

You can then use the instance array capabilities of the assemblies tool to array the freeform shape with any number of anstances (completely parametric).

Then what you need to do is WAVE Geometry link that freeform part and all of the instances into the actual part file. This will create the actual freeform geometry in that part.

Lastly you can unite the freeform feature and all of the arrays to the actual part.

You now have to ability to edit that freeform shape and have everything update completely associatively.

A good example of usage of this technique is in propellor design such as that of a nuclear powered submarine where the propellor is one machined piece of metal.

Best Regards,

 

[scrimy]

Thanks Zilla. I haven't used WAVE geometry linking before but will check it out, it sounds like it may do the trick.

Its interesting that you mention a propellor. I have modelled an impellor similarily and the whole problem arose when I tried to trasform the geometry in a direction other than along the Z-axis of the feature array. It seems that there is no associativity between the array axis and the rest of the model. This only seems to be the case when you move free form grouped feature arrays such as you require for impellor blades. Arrays of regular features can be transformed away from the original z-axis.

I thought that I was maybe missing something but it seems it is a gremlin within UG.

I'll try WAVE to get around it!

Thanks again,
Scrimy

 

[scrimy]

Slight problem with learning more about WAVE let alone using it. We don't have the WAVE license! Guess I'll have to find another way around this one. Any other approaches?

regards,
Scrimy.

 

[zilla74]

Dear Scrimy,

Everyone has the WAVE geometry linker capabilities. This capability is standard in Unigraphics. You are required to turn the capability on by opening your ug_english.def file in the UGII subdirectory. Find the string called Assemblies_AllowInterPart: and set it equal to yes.

This will give you the ability to use the WAVE geometry linker in Unigraphics.

To use the capability you must (this is in V18 at least. I don't have V17 to explain where exactly it is) select the assemblies pull down, select WAVE geometry linker and the WAVE linker dialog will display.

When working in the context of an assembly you must make sure that your work part is the part that you wish to link the geometry into. Change the link type to body, select the freeform geometry and now the freeform geometry is associatively linked into the other part file.

By using the assembly tree, select the freeform part an blank it from display.

Now you can use the unite boolean feature to unite the two bodies together.

If you have any other questions let me know.

Good Luck!

 

[guyinfun]

Another working around which I usually use is :

- Create your teeth in the free form feature. (dont unite or subtract with your master blank)
- Create "Extract" feature by picking the free form body from above. ( This is just an associated solid copy of free form feature).
- Now do the boolian with the new extract solid. You should be able to do array on that boolian.

This should help if you dont want to see too many files in your assembly navigation tool.

raikotia@yahoo.com