6 Benefits to using Sub Assemblies in Machine Design

Discover How Sub Assemblies Save a Ton of Time and Money in Machine Design.

Sub Assemblies in machine design are fun and easy and the really help save time and money in a lot of ways.  Once you learn how to use them efficiently you will see all kinds of places that they can be used.  Then, you can be the CAD wizard at your company!

A sub assembly is just a 3D CAD Assembly that is inserted into the Main 3D CAD Assembly in machine design.  If that sentence doesn’t make sense, keep reading and watch the video below to get a good idea of how Sub Assemblies are super tools for Machine Designers.

For example these Jergens Jig Feet along with RAPid Shims and manufactured risers are used several times in a fixture.  As sub-assemblies they save time, and unclutter the assembly drawing.

 

 

 

 

This configuration of RAPid Blocks and RAPid Shims is used in several places on a weld fixture.  Only the pin changes.

 

 

 

So this configuration, without the pin, is a good candidate for a sub assembly.
It will save engineering time to create it once in a Sub Assembly and then insert the Sub Assembly into the Main Assembly several times.

 

This goal post is part of a change over fixture.  A change over means that more than one product is welded within this fixture.  To “change over” the fixture to hold a different product, one sub assembly can be removed, and another sub assembly (or cover plate) can be put in its place.

In a fixture with lots of parts, it is easier for the machine assemblers to read the assembly drawing and assemble a machine when the drawing is less cluttered.

Benefits

1)      The Machine Assemblers will love it!  The drawings are easier to read.  There are less Balloons on the Main Assembly Drawing.

2)      It is easier to job out parts of the fixture to be made by contractors or machine shops.

3)      If sub assemblies are contracted out to be made, more people can be working to create the machine at the same time, moving the machine into production faster.

4)      Faster CAD design because the same sub assembly can be inserted several times into the main assembly.

5)      Assembly model checking time is reduced because each sub assembly only has to be checked once.

6)      The MAIN BOM can contain all the parts for the whole machine, just like always.

Numbering

It depends on your numbering system.  All parts in a sub assembly get normal part numbers.  Even the sub assembly gets a normal part number.  If a 3/8” jam nut is part 103, you can use part 103 inside a sub assembly and also elsewhere in the main assembly and it won’t be a problem.  The main Bill of Material will reflect the total quantity of parts both inside and outside the sub assembly.  And the Sub Assembly Bill of Material will contain only the quantity of part number 103 used in the Sub Assembly.

We find it helpful to use the words “sub assembly” in the name or description of the sub assemblies.  That way they are easy to identify in the BOMs.  Your company may use a special group of numbers for your sub assemblies.

Now discover how to get the Bill of Material (BOM) to show all the parts but balloon only the parts not in the sub assemblies!  Watch this short video.  (The demonstration is using Pro/E Wildfire 4.0. )

So the instructions for flattening  the Bill of Materials for the purpose of ballooning only those parts not included in the sub assembly is as follows.

Steps

  • Select Table from Top Menu
  • Select Repeat Region
  • Select Flat/Rec Item from the pop-up window
  • Select the Bill of Material (Table)
  • Select Default or Flat (to flatten the Bill of Material)
  • OR Select Recursive (to expand the BOM show the parts that are in the Sub Assemblies)
  • Select the sub assemblies in the BOM
  • Click OK or “Done”

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Leave a comment below… tell me, do you use sub assemblies?  Why or why not?

‘Til next time…

The Queen

About rentapen

Susan Straley, aka Queen of Lean Machine Design, is the President of Rentapen Inc. in Waukesha, WI. She helps manufacturers reduce costs through excellence in 3d desing services, RAPid Tooling Components(TM), and Just-in-Time Laser Cutting Services(TM). Susan can be reached directly at 262-542-8891.
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