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Eagle 3D PCBs with Alibre: Assembling the Model Part II

Before starting to put all the pieces together, spend some time planning.   Things to think about include:

  • What is your naming convention?  A good naming convention for parts and assemblies really helps you remember what is what.  Which is a more useful name for a connector model, Part_21 or AMP 5499206-IDC-26?
  • How are you going to assemble the part?  Are you going to use any sub-assemblies?  Good use of sub-assemblies makes assembling the model easier and more logical.
  • Do you have all your part models?  I like to have all my models ready before assembly, but you could start with what you have, and download or create as you go.
  • Do you need to modify any manufacturer provided models?  For example, your part might be slightly different from the closest manufacturer model, or you may need to modify the part (e.g. by adding reference geometry) so you can easily add constraints.
    • I’ve come across both these cases, and will discuss them more in the future.
  • Are you going to directly import your manufacturer models into your assembly, or convert them into Alibre parts first?  Alibre Design 2011 can directly import STEP, SAT, and IGES parts into assemblies.
    • IIRC, previous Alibre versions couldn’t directly import into assemblies, which is why my current designs convert all imported parts into Alibre parts.

Here are my tips on adding constraints:

  • Come up with a naming convention for constraints: J1_Align_Pin1 provides much more information than align22.
  • Position the parts so you can see all the features you plan on using to mate the parts together.  I really like using the triad tool, with minimum motion mode off.
  • I’ve had much better results using the manual constraints dialog than trying to use quick constraints.  Sometime I’ll give quick constraints a try again.
  • I’ve found it’s always necessary to move and zoom all around, and every time I use the icons, my constraints dialog goes away, so shortcuts are the way to go:
    • Pan: press and hold middle mouse button, then move mouse pointer
    • Rotate: position the mouse pointer where you want to rotate, then press and hold right and left mouse buttons, then move mouse pointer.
    • Zoom in: press Page Up
    • Zoom out: press Page Down
  • Be careful where you click; it’s easy to select a feature you don’t want.
  • I like anchoring one part (for example, the PCB) so I know which part will be moving when I add constraints
  • Check the defaults.  Often, the mate constraint will show the current distance between parts, so I have to change it to zero.
  • Use your PCB layout as a guide.  OK, if I could get Alibre to handle the silkscreen layer this wouldn’t be necessary, but it’s handy when I have a PCB full of holes and no silkscreen information on the PCB model.


1 Alex P { 01.16.11 at 11:37 am }

I find quick constraints works really well in the current alibre version, and the last one before that compared to before. I tend to use it for the vast majority of assembling now. They also have a button in the quick constraint dialog box now, not sure what it’s called, but it essentially means ‘other way around…’ when it’s first attempt at constraining mates the parts the wrong orientation d

2 Tony { 01.16.11 at 4:02 pm }

Thanks for the tip; I’ll give quick constraints another look in the (hopefully) not too distant future.

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