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Modeling Accurate Wires w/o Routing Add-In

Question asked by Nathan Cassou on Jan 4, 2013
Latest reply on Jan 7, 2013 by Mike Pogue

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The company I work for uses SW Standard 2012 without the Routing Add-In. I have been put to the task of updating all of our products into 3D assemblies which I am now learning requires electrial routing of small gauge wires. I watched a tutorial on how to model and route a wire manually using a 3D spline and a round profile to sweep. It seems to be working just fine, however I question how accurate are these wires in the assembly. We will be doing shock and environmental simualtions (using SW Premium Simulation) on the product and I would like to know if this would be an adequate method of modeling wires for a simulation. Would the most detailed wire be the best? Meaning should I actually model a small strand of wire, twist several together in an assembly, and then try to model some sort of plastic coating over it? Is the more detail better when these are going in an assembly simulation?

Mike Pogue Jan 7, 2013 10:35 AM

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Nathan,

I really believe it is impractical to try to simulate wires with FEA. The solder joints are the critical points, and these will contain discontinuities precisely at the points of failure which will make it impossible to interpret the results. There has been work done with FEA and solder joints; but I don't think the techniques are accessible for a design engineer working with SolidWorks Simulation.

I think many designers are confused about the level of accuracy that is obtainable from analysis. In academic environments, where people dedicate their lives to solving one FEA problem, 10-20 percent error is described as excellent agreement. With vibration analysis of a CCA, for example, your goal is not to find that exact natural frequency of the board. Your goal is to satisfy yourself that the first mode is more or less out of band. Also to identify areas that need to be shored up. Determining the actual stresses in connectors and wires is, in general, not a design engineer level task.

Use good design practice with staking and strain relief. If you have to analyze solder joints, do it in excel, not Simulation. Take a look at the techniques in Steinberg "Vibration Analysis for Electronic Equipment" and "Cooling Techniques for Electronic Equipment", or do a Google search. Set yourself up some classical analysis tools so you can quickly analyze lots of joints.

These are my recommendations.

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Mike Pogue Jan 5, 2013 1:05 AM

Nathan,

The method you propose, modeling strands and insulation, will not work without a supercomputer. This is true for modeling, but even more true for simulation. For modeling, just continue with the sweeps unless, like me, you get tired of it and stop modeling wires altogether.

For simulation, you can probably model wires as beams. You'd have to work out the physical properties yourself. But you would not get useable results. Wires constantly deform plastically, with enormous amounts of structural and material viscous damping. This sort of thing is simply not reproducible with normal FEA tools, especially the sort of rudimentary tools that come with SolidWorks

Unless you are doing extremely sophisticated analysis, Omit wires, connectors and other details from your simulations. You'll never be able to mesh them, and you'll grow old and die waiting for all of the contacts to solve.

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Nathan Cassou @ Mike Pogue on Jan 6, 2013 12:25 AM

Mike,

What you said is the truth. Modeling these is a real pain in the butt. However the wires seen as a mechanical component in the assembly. The product undergoes Vibration, shock, and thermal stresses which could have an impact on the wiring. Also the wires are soldered to a PCB. Would I need to model the solder? Like weldments feature?

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Mike Pogue @ Nathan Cassou on Jan 7, 2013 10:35 AM

Nathan,

These are my recommendations.

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3 Replies

Mike Pogue Jan 5, 2013 1:05 AM
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Correct Answer
Nathan,

The method you propose, modeling strands and insulation, will not work without a supercomputer. This is true for modeling, but even more true for simulation. For modeling, just continue with the sweeps unless, like me, you get tired of it and stop modeling wires altogether.

For simulation, you can probably model wires as beams. You'd have to work out the physical properties yourself. But you would not get useable results. Wires constantly deform plastically, with enormous amounts of structural and material viscous damping. This sort of thing is simply not reproducible with normal FEA tools, especially the sort of rudimentary tools that come with SolidWorks

Unless you are doing extremely sophisticated analysis, Omit wires, connectors and other details from your simulations. You'll never be able to mesh them, and you'll grow old and die waiting for all of the contacts to solve.
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- Nathan Cassou @ Mike Pogue on Jan 6, 2013 12:25 AM
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  Mike,
  
  What you said is the truth. Modeling these is a real pain in the butt. However the wires seen as a mechanical component in the assembly. The product undergoes Vibration, shock, and thermal stresses which could have an impact on the wiring. Also the wires are soldered to a PCB. Would I need to model the solder? Like weldments feature?
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  - Mike Pogue @ Nathan Cassou on Jan 7, 2013 10:35 AM
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    Nathan,
    
    I really believe it is impractical to try to simulate wires with FEA. The solder joints are the critical points, and these will contain discontinuities precisely at the points of failure which will make it impossible to interpret the results. There has been work done with FEA and solder joints; but I don't think the techniques are accessible for a design engineer working with SolidWorks Simulation.
    
    I think many designers are confused about the level of accuracy that is obtainable from analysis. In academic environments, where people dedicate their lives to solving one FEA problem, 10-20 percent error is described as excellent agreement. With vibration analysis of a CCA, for example, your goal is not to find that exact natural frequency of the board. Your goal is to satisfy yourself that the first mode is more or less out of band. Also to identify areas that need to be shored up. Determining the actual stresses in connectors and wires is, in general, not a design engineer level task.
    
    Use good design practice with staking and strain relief. If you have to analyze solder joints, do it in excel, not Simulation. Take a look at the techniques in Steinberg "Vibration Analysis for Electronic Equipment" and "Cooling Techniques for Electronic Equipment", or do a Google search. Set yourself up some classical analysis tools so you can quickly analyze lots of joints.
    
    These are my recommendations.
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Modeling Accurate Wires w/o Routing Add-In

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