Possibility to edit expression values in different levels

[Sillen]

Hi,

I can't find any way to create an expression which value can be edited on the part level and also in the top-level of the assembly.

I'm also wondering if there's any "expression document" available, to all, that states possibilities with expressions. I guess there's a lot more to learn than what's stated in the help section.

Thanks in advance,
Sillen

 

[MickyV007]

If you want something like that maybe think in the direction of deformable parts or family tables or reuse library.
Many ways lead to Rome.

Best regards,

Michaël.

NX7.5.4.4 + TC Unified 8.3

 

[Sillen]

Thanks for the input Micky,
I will try those suggestions but a possibility to change a value on different levels would be the easiest way I guess. I will play a little with those functions and see if I ever get to Rome =)

Two situations where I would like to use this is:

1: Use "suppression controlled by expression" for machine features in order to use one part instead of two for casted and machined parts. Would be nice since the assemblies are very heavy and reduce the amount of parts by almost 50% would a great success (haven't evaluated this way of working thoroughly yet, guess there's a good reason why it's not used as standard)

2: The expression for the length of a base component is used in instanced features and instanced geometry as well as pattern face in the same component but also many other components are using that specific expression. If this value could be changed in different parts and assembly levels it would be great.

By the way I'm running NX 6.

 

[JohnRBaker]

Have you looked at Interpart Expressions?

These will allow you use expressions at different levels of an assembly and depending on the direction of the link, you can either 'bubble' the value of an expression UP to a higher level in an assembly where it can be used to say control a constraint on a component or change a deformable part, or the Expression could be created at some HIGHER level and then used to drive some expression value DOWN to some component part where it overrides some parameter causing the component to change size or shape. Note that these overridden expressions would only be in effect for the assembly where they are used and does not change the actual piece part if it's used in some other assembly.

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.com/museum/

To an Engineer, the glass is twice as big as it needs to be.

 

[Sillen]

Hi John,

Yes I have played with those. I tried both to link it up and to link it down but I would like to not only reference a bubble in higher levels of the assembly but also edit it.

Let's say I create one (or one per sub part) expression "machined" at the top level then I, in the lower level parts, use interpart expression to create suppression controlled by expression (machined) features.

This lets me switch from casted components in the assembly to only machined components just by changing one value in the top level, however I would like to be able to open one of those sub parts separately and switch from casted to mahined. Therefore I'm wondering if there's any way to create "bi-directional/editable" expressions. I'm still not sure this is a good way to handle casted and machined versions but there's more situations where I reckon this to be useful.

Best Regards,
Sillen

 

[cowski]

For cast/machined components you should look into promotions and/or wave linking.

 

[Sillen]

Cowski I've seen that promotions and then wave linking are the preferred methods but I can't figure out why not use suppressions controlled by expressions instead. This reduces the amount of parts in an assembly by almost 50%. I guess there are some resons but what are those?

The only downsides, that crossed my unexperienced mind, are that you get the same part nr for the casted and the machined version but that must be possibe to handle with attributes or similar and the fact that you're only able to edit in either the top level or on the part level not both hence my thread.

And even if there are some good reasons as I mentioned there are other situations where I would like to use "bi-editable" expressions.

//Sillen

 

[cowski]

The 'one part number for 2 different parts' scenario is potentially a huge downside to this approach, especially if the department/company that machines the part is separate from the department/company that casts the part. The only way I see this working out is if you are part of a small company with great communication that is in complete control of the design and manufacture of the part(s).

I can't figure out why not use suppressions controlled by expressions instead. This reduces the amount of parts in an assembly by almost 50%

I'm not sure I follow your reasoning here. I've never seen the 'as cast' and the 'as machined' part used in the same assembly, if the casting is going to be machined before use I can't think of a reason the 'as cast' part would show up in any assembly. Not to say it should never be done, just that I have not seen it.

 

[Sillen]

Cowski the company I just started at are going from Ideas to NX and the approach some of the designers are using to handle machined and casted parts is that they create the casted part and then create new parent in which the casted body are linked and the machining features are added. So to use the machined parts in an assembly they have to add both the casted and the machined (since the casted is a subcomponent to the machined)

Comparing this approach with my idea of using one part having machined features controlled by expression gives you a reduction of parts with almost 50% in assemblies.

However if the linking of the casted body is done to a part on the same level this problem is resolved since you don't have to use an assembly in the "big" assembly.

If it would be possible to use "bi-directional" expressions and also possible to assign an alternative part number to a component I would definetely use one part with machined features controlled by expression since this let's you easily swap from casted to machined and you don't get any links that requires updating and which also might slow down the PLM system.

As it is now I will go for the method where the casted body is linked to a part at the same level.

Thanks for your input.

 

[moog2]

If you add the cast part as a component, to the machined, and wave link it, you'd then replace the reference set of the casting to "empty".
Then when you load the machined part in an assembly, the casting won't even be loaded, so i don't think it can slow the assembly down.

 

[cubalibre000]

Hi Sillen,
there are different approach :
- Interpart link approach
- Geometry wave link approach
- Hole series approach
- Promotion approach

All depend what you have to do.

For what you are talking with cowski, he's has right.
Maybe you have confusion or doesn't know for performances.
For casting and machined part, this is the best solution (promotion).

If you want to design at the assembly level (top-down), depend what you have to pilot.
For holes I suggest Hole series.
For shape, I suggest wave geometry link.
For some dimension value, I suggest interpart link.

Thank you...

Using NX 7.0.1.7 MP3 and TC8.1