Modeling tube frame cross sections

[GregAnderson]

I am modeling a steel tube space frame for a car. I have a series of sketches and section sweeps with a circular cross section along their trajectories. I use the "create a thin feature" button to create the tube wall thickness. Pro/E sets limits on the wall thickness I can assign to the tubes and they are very unreasonable. Currently all of my tubes are 0.17" thick because it will not let me assign a thinner value. If someone could explain to me how Pro/E determines the thin feature limits for a cross section sweep that would be great.

I can resort to skething 2 concentric circles and setting a dimension between them but its not

Thanks.

This thread is inactive and closed by the PTC Community Management Team. If you would like to provide a reply and re-open this thread, please notify the moderator and reference the thread. You may also use "Start a topic" button to ask a new question. Please be sure to include what version of the PTC product you are using so another community member knowledgeable about your version may be able to assist.

[DavidButz]

You can also create them as Surface features, and Thicken them afterwards.

[DavidButz]

Also discovered, experimenting a little, that even though the system wouldn't allow me to make a 1" diameter tube with less than a .002" wall, after creating it I could modify the thickness all the way down to .0001". On the other hand, changing absolute accuracy seemed to have no effect when creating a new part.

[GregAnderson]

Its not the decreasing decimal thats giving me a problem. Pro/E literally states "thickness must be between .0962" and 1.985". and it seems the lower limit gets larger with each sucessive tube that we add to the frame, which is one part. So we create one sweep down a sketch trajectory and the lower limit might be .096" and then when we create the next sweep on another sketch trajectory the lower limit is now .098" and so on with each successive tube. I think we can work around it at any rate just explaining the problem.

We are also having problems doing an FEA on the frame becuase the some of the tubes do not merge correctly. What would be a good method to trim one sweep where it meets another and yet still have them bonded to each other if we go to do an FEA?

I would give you a screen sheet but I don't have Pro/E on this computer. I will try and post one later.

thanks.

[DavidButz]

Greg,

Without knowing the details, I would strongly recommend looking at Surface construction because of the merge problems you are having. One of the big advantages of surface modelling is that you don't need to worry about "where the mass lies" allowing edges and ends to intersect and "spill over" and be easily trimmed back when you merge one surface with another. In other words, you could build your entire part with swept surface tubes, merge them all together, then Thicken as a final step. I don't know what your geometry is, but in some cases you could build such a framework from solid sweeps, and Shell at the end. Don't know why the minimum thickness changes the way it does; that does seem odd.

David