Designing in car position or not in Catia V5 3

[Belallali]

Dear all,

I have been tinking a wile about this topic for chassis design in Catia V5. In chassis engineering it is common practice that all components are modeled in car position. However, some company's prefer modeling each component in its origin (model space size and for maufacturing).

From Catia V5 perspective it would make sence to use the suspension hardpoints as input for each single part. If you would decide that each part has to be designed in its origin, than all the hardpoints in the single parts have to be transformed to the origin area without losing its relation with the hardpoints in carposition. As suspension systems have quite complex relations between all its parts, this methodology will bring al lot off problems. I think it is best to model chassis components in car position, but I want to know how other engineers think of this topic.

Best regards,

B. El-allali

 

[ubrben]

My approach was always to model a part in a local axis system. In the context of V5 it always made drafting easier.

The position and orientation of the part within the vehicle's global axis system is then covered by the assembly. Information about the tranformation can then be stored in a VPM database of some kind.

For simple stuff we always used to create a blank .CATPart with just an axis system at 0,0,0 in it, and then import this into an assembly. You can then model the part about its local axis in the .CATPart and it will always be in the correct location in the assembly.

Ben

 

[catiajim]

This is a big topic, especially in V5.

If you are using a PLM Solution (SmarTeam, VPM, or ENOVIA PLM), it becomes even more complex.

Much of the power of V5's Assembly Design tool is in the Constraints. If all parts are modeled in position, then you don't need any constraints other than FIX.

If you are using a PLM Solution, then the real problem becomes, what vehicle are they in position for? Serial number 1? Or Serial number 1001?

Another power of V5 is the ability to start working Detail Designs earlier in the project. If your parts are "in position", what do you do if there is a configuration change?

PS If you are going to COE, you might want to check out General Session G-J on Tuesday, where I will be discussing this topic at length.

 

[ferdo]

Hi,

Catiajim is right. In addition, maybe you can use same CATPart in different assemblies, in different positions, on different products.

Its much easier to position the parts if they have a local axis system.

Of course, there are some situations when you need to create parts in position (for example, some of frames or stringers for aircrafts).

Even in this case, you can use an axis to axis transformation, so your part will have his own axis system but created in a relation with that of the master geometry which you have to use (this is the one of the cases of stringers in aircraft industry).

So, its not a general rule, depends on what you need to design.

Regards
Fernando

 

[Belallali]

Hello fredo and catiajim,

Thanks for your response. I think I have to add some more details to this topic. For suspension design I want to use a skeleton approach. In this skeleton the whole geometry is defined and modifyable through parameters. Geometry from this skeleton wil be used as input for the single parts. This means when the skeleton is modified, all related parts will adapt to their new situation. Then another point, the whole suspension assembly has kinematic definitions for packaging studies.It is important that these definitions stay intact after modifying the skeleton. The suspension geometry has complex and multiple relations between parts. This why it makes it so complex and I am trying to find new, flexible ways for a solution to this topic.

Best Wishes.

 

[catiajim]

In a system this complex, whatever you do, be sure you are consistent.

Personally, I favor the "local coordinate" approach. Especially if you are looking at a system that has Kinematics and Motion.

 

[Akesson]

Hi,

A very interesting discussion. I'm not into building cars but the problems occur in many different areas.

I agree with that the methodology should be adapted to each single case. There is not one single solution to this topic.

However, I agree that it's very powerful to build "skeleton parts" to use for part design. This "skeleton part" combined with a "reference part" makes the metodology even better. The "reference part" is a part containing all planes etc for positioning the detalis (not secondary structure like bolts etc).

By building like this you both have the flexibility of a local axis system in each detail (use the detail in many different positions) and the possibility to manage the positions of many details by only make the changes in one part ("reference part").

If you the drive all planes/lines/sketches of these parts "skeleton and reference part" with parameters and rules you can have a very stable and smart product.

Best Regards
Akesson

 

[Belallali]

Hello Akesson,

I see that you are also thinking in the same direction as I am. I think this is a very big issue in al kinds of industries which needs careful thinking and consideration. The result of this methodology for me should be flexible adaptable parts who are assembly independend and yet have a relation to their final positions (hardpoint locations).

Each industry (company)should decide what will work the best for them. The methdology of which I started this topic is not limited to CAD only. Think of archiving, CAE relations, manufacturing, product configuration managment, etc. Its huge and complex.

With great power comes great responsebility!!. I am looking out to see more reactions to this topic.

Best regards

 

[ferdo]

Hi,

Maybe you can use in this case a very useful function in v5 - power copy, eventualy combined with desgn tables or rules in order to design the parts in their position in assembly.



Regards
Fernando