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Nominal Height for 3D STEP Parts
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JJonas View Drop Down
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Points: 113 		Post Options Post Options   Thanks (0) Thanks(0)   Quote JJonas Quote  Post ReplyReply Direct Link To This Post Topic: Nominal Height for 3D STEP Parts
    Posted: 13 Apr 2015 at 4:05am
I would like to be able choose whether max or nominal height is used when 3D models are generated. I think consistency is a key feature of a well-organized library.

I have not yet found a 3D part supplied by manufacturer that would be drawn using max height.

They use nominal values for everything.

So, I would like all 3D parts generated by your tool to have nominal height as well.
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Tom H View Drop Down
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Points: 5718 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 13 Apr 2015 at 5:29am
The component Dimension "A" controls the 3D STEP model height.
 
You can put any value you want there. Minimum, Nominal or Maximum.
 
99.9% of all the Library Expert users want the 3D STEP to be Maximum Height as it compensates for the solder volume under the component.
 
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jameshead View Drop Down
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Points: 576 		Post Options Post Options   Thanks (0) Thanks(0)   Quote jameshead Quote  Post ReplyReply Direct Link To This Post Posted: 13 Apr 2015 at 5:31am
I prefer having the maximum height rather than the nominal height.

I'm outputing a STEP file of my board with the components on for a Mechanical Design Engineer who's going to be running clashing tests with the mechanical model and telling me if it fits or not.  He's not a PCB Design Engineer and he's also got a lot of other work to get through.

He doesn't want a nominal model to check and then to look more in depth at a possible conflicting area to double-check something tight to see if the maximum height is going to be an issue.  All he wants to do is a quick check against the maximum hieght and a quick feedback to me yes/no.

If we use nominal height on STEP models then I can foresee problems in the future and my boss isn't going to be satisfied with a "we didn't check the maximum height because the STEP model is nominal" explanation.

Choice is good if many people prefer nominal but I think the default should be maximum.
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Points: 113 		Post Options Post Options   Thanks (0) Thanks(0)   Quote JJonas Quote  Post ReplyReply Direct Link To This Post Posted: 13 Apr 2015 at 5:57am
Originally posted by Tom H Tom H wrote:

The component Dimension "A" controls the 3D STEP model height.

You can put any value you want there. Minimum, Nominal or Maximum.
It is a workaround, in row A you are only asked to type max height. Other entries in that row are discarded.
If you have a bigger library of components, I am sure you will not be willing to go and manually change height before exporting each part. Of course, you can specify nominal height instead of required max height, but then part name and description will be wrong.
 
Originally posted by Tom H Tom H wrote:

99.9% of all the Library Expert users want the 3D STEP to be Maximum Height as it compensates for the solder volume under the component.
That is a bold statement statement, I would like to see a survey that concludes this.

Originally posted by jameshead jameshead wrote:

I prefer having the maximum height rather than the nominal height.
I do understand why maximum height is chosen. My two arguments against it are:
 - Complex 3D models provided by manufacturers use nominal height and I am pretty sure users do not redraw them, so you end up with a design where one part of 3D models are drawn by nominal sizes and another part that is not. I see this as a mess.
 - If we are not talking about small parts, not only height but also nominal width and length could introduce clashing. Does your Mechanical Design Engineer put that into consideration? 
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Points: 576 		Post Options Post Options   Thanks (0) Thanks(0)   Quote jameshead Quote  Post ReplyReply Direct Link To This Post Posted: 13 Apr 2015 at 6:06am
The majority of our STEP models come from PCB Libraries and use the maximum height.
Where I can't get a standard model out from PCB Libraries, and if it's within my very basic capabilities in FreeCAD, I'll create a simple model myself.

Any non-standard part in PCB Libraries where the STEP output will suffice for a mechanical clearance check then a basic shape of the maximum height will normall suffice.

We will use STEP models from Molex and SAMTEC for their connectors but here we are very careful because we know that we are looking at connecting boards/mechanical fittings together so we'll talk over these.

Any other parts I will ask very nicely for the Mechanical Engineer to model up - which he does to the maximum size.
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Tom H View Drop Down
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Points: 5718 		Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 13 Apr 2015 at 6:32am
Dimension "A" value is totally up to the User. That value represents the Height of the 3D model.
 
Since 99% of the users asked for and want Maximum Height that is what we labeled it.
 
But it's a free world (at least to the people we work with) and you can put any value you want for the "A" dimension.
 
We have no intention on adding another feature to Library Expert to force our customers to put in a Nominal and Maximum Height. Our programmers are paranoid that adding too many features turns the software from a "User Friendly" tool to something that is so complex that the learning curve goes up to several weeks to learn about each new feature. We want Library Expert to be easy to use while delivering high quality results.
 
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