top-down design with autodesk® inventor™ using skeletal modelingwidom-assoc.com/ma301-1p.pdf ·...

Top-Down Design with Autodesk® Inventor™ Using Skeletal Modeling Rickard Lindgren – Autodesk

MA301-1P Working with exceptionally large or complex assemblies requires a great deal of planning and organization. In this class, we’ll explore how Autodesk Inventor can use Skeletal Modeling to create new and powerful ways to keep you organized and get the job done.

About the Speaker:

Rickard has been in the Manufacturing Industry working with Autodesk based software for more than 14 year. He has in-depth experience helping customer implementing solutions for their engineering department making and defining methods and workflows for specific tasks and demands. His work at Autodesk started in 2000 as an Application Engineer managing the Nordic & Baltic countries in Europe.

[email protected]

Top-Down Design with Autodesk® Inventor™ Using Skeletal Modeling

The demands when it comes to handle large assemblies are increasing all the time.

There are a lot of different things to take into consideration when trying to push the limit further and further and increase the amount of components in an assembly when trying to create more fully defined digital prototypes.

This class will cover different Skeleton Top Down design methods that will help you in both getting more out off your system. Even more important it will give you a much better way of doing design work and also help working in a collaborative environment.

Skeletal Top Down design is a method of working. Not specific commands in Inventor. It all comes down to that you in the first step of a project put all the known factors into a Skeleton-file which then are used as a base for most of the sub assemblies and parts.

We will take this in three sub-steps.

1: Introduction to the differences between Bottom Up vs. Top Down

2: Different Methods for Top Down design

3: Supporting Inventor features


1: Introduction to the differences between Bottom Up vs. Top Down

Bottom Up is the traditional way of building assemblies. You first define the different parts. Then you put them into sub assemblies using assembly constraints. Then the sub assemblies are placed into higher lever assemblies up to the top level assembly and in this way working your way from the Bottom Up.

This will create assemblies with a lot of relations between parts and assemblies. This will lead to two things. One – it eats up system resources and slows down performance. Two – it makes the models hard to change due to a lot of cross references or that referenced geometry gets deleted.

A typical simplified example of this is building a card house. You start from the bottom leaning the cards towards each other for support and build your way upwards where every new card placed are dependent on the previously placed cards. If you then needs to perform a design change like replacing one of the cards in the first layer with a new one you’ll run into stability problems since later placed cards are dependent on the card you remove.

Top Down is a method where you start defining the end result and put all the known. Then you use this as a base for underlying sub assemblies and parts. In this way you’ll have a single conceptual file containing the overall information of the design with a single place for upcoming design changes. Working this way will give you a much more stable Inventor model, faster updated, more available resources for handling larger data sets, easier way of working in a collaborative environment and a better way of doing design work in general.

Following the previous example with the card house one Top Down approach to this would be to first model a part containing the 2D-layout of how the final Card House would look like. Then every individual card will have this file as a base giving them both the size needed and the location where they fit into the assembly. By doing this it is very easy to replace any of the cards since they don’t reference any other card but just the skeleton framework.


2: Different Methods for Skeletal Top Down design

A: Skeleton file – different possible content

B: Master Sketch – controlling both form fit and function

C: Absolute Origin – limit the need of assembly constraints

A: Skeleton file – different possible content

A skeleton file can contain of any type of elements in any mix. Typical information created in a skeleton file is…

Sketches – defines to basic concept of the final product or are used as a layout of different areas.

Work geometry – defines important connection points, axial directions and work panes that define levels

Parameters – defines important values for sizing parts, angles for placements and other known values for the design

Solids – define volumes for final assembly as a single part or for defining subareas of the design


B: Master Sketch – controlling both form, fit and function. Example

(For less complex or detailed designs skip Step 3 and 4)

Step 1: Create the Master Sketch. Create one sketch per moving sub set of the final assembly

Step 2: Place the Master Sketches into individual sub assemblies. Put these sub assemblies into an assembly and place assembly constraints to define the function

Step 3: Create a new part per moving sub assembly. Start the part by deriving in the Master Sketch for that sub set. This can now easily be used as the simplified representation later on

Step 4: Place the part into the earlier created sub assemblies

Step 5: Create all the individual part by deriving in the Master Sketch for which sub set it belongs to. By doing this the Master Sketch now dictates the size and the position of the part and also ensures that it fits into the sub assembly

Step 6: Insert the parts into the earlier created sub assemblies. Place them at 0,0,0 and ground them


C: Absolute Origin – limit the need of assembly constraints

This is a method where all sub assemblies are placed on the same origin. Every sub assembly will be based on an origin part. This origin part is usually a sketch or a solid defining the volume. All sub assemblies are positioned against its origin parts 0,0,0 and then grounded.

The advantages of this method are…

• Easy to define

• Easy to manage

• No or very few assembly constraints needed

• Fast and predictable changes

• Easy to replace sub assemblies

The limits of this method are…

• No dynamic motion between sub assemblies

Conclusion…

• Use for static assemblies without functional motion

• Good for collaborative work

• Good for driving and supporting modularization


Absolute Origin – Example

Step 1: Create a part with the layout over the design

Step 2: Create new parts for the sub areas and derive in the layout part. Create a volume for each sub area

Step 3: Create a new assembly for each sub areas in which you place the volume file. This enables you to use this as a simple representation for the different sub areas of the design

Step 4: In the respective sub assemblies you now fill the volumes with the detailed design. Make sure to make use of the volume for sizing and making sure to stay inside you work volume

Step 5: Create a new top level assembly where you place all the sub assemblies at 0,0,0 and make sure to ground them. Since everything refer back to the layout it is very fast and easy to perform changes and to replace a sub module with another without disturbing the surrounding modules


3: Supporting Inventor features

As I said initially there are no buttons in Inventor names Top Down or Skeleton since this is just a matter of methodology. But in order to perform these methods we utilize basic functionality in the software. This last section will point out the most commonly used features used for Skeletal Top Down design.

A: Derived Component

B: BOM – Reference and Phantom

C: Level Of Detail – LOD


A: Derived Component

Derived Component is one of the most commonly used features when working with Top Down design. This ensures a fast and easy control of all ingoing parts and assemblies from one single source.

When starting a new part, exit the first sketch and start the Derive Component command. Select the Skeletal part file and make sure to select all the relevant information for the component you are about to create. There are different workflows available for the information that the Skeletal file may contain. Like parameters, sketches, solids and surfaces.

Parameters: In the Skeletal Part file the parameters needs to be marked for export otherwise they will not be available in the Derive Component dialog

Solids: Even if you have created a solid you can derive this as a work surface instead of a solid. This can be a valid workflow when breaking a design concept into sub components


After created a fully detailed sub assembly you might want to be able to present this in a simplified version to minimize to amount of data loaded but still have a placeholder that contains all the important connections and outer boundaries. This can be made by taking the complete sub assembly into a new part using Derive Component. There are some things to keep in mind doing this

• Don’t bring over more information than needed. Don’t put small and internal parts into the calculation

• Use the simplification option to get just a boundary box on the part not necessary to keep in full detail

• Suppress the link and keep the updates on demand


B: BOM – Reference and Phantom

When starting to build up Top Level assemblies you’ll create some extra assemblies that from a BOM point of view shouldn’t exist. And also you’ll build sub assemblies that combines parts into assemblies even thou they should appear as individual components one level higher. To make sure to still get the right BOM we’ll utilize the functionality to set the Default BOM Structure in Document Settings for the parts and assemblies

Reference: Parts marked as reference will be ignored by BOM and Parts List. Assemblies and all its ingoing components will be ignored by BOM and Parts List This can be used on Skeletal Parts and on parts representing the Simplified version

Phantom: Assemblies mark as Phantom will be ignored by BOM and Parts List and its components will be moved up one level, just if the assembly wouldn’t exist.


C: Level Of Detail – LOD

Level Of Detail is a tool function that enables you to define how many components that should get be loaded when opening an assembly. This gives you the control over the system resources used and makes you control the detail level on an assembly. Just create a new LOD in the browser and then right click on ingoing parts and assemblies to control if they should be Suppress or not in this particular LOD


Practical Example

A combined workflow of Derived Component, BOM Reference Part and LOD to create and use alternative representation of an assembly can look like follows…

• In the Base Assembly create a Level Of Detail of the full version

• Create a new part and do a Derive Component of the Base Assembly using the LOD of the full version

• Deselect any “unnecessary” part like small and internal parts. Use simplification on as many parts as feasible

• Suppress the Link. Otherwise you’ll end up with a cyclical reference in the next step

• Place the new Simplified part into the Base Assembly

• Suppress the Simplified Part in the Full LOD

• Create a new Low Level LOD with every component suppressed except the simplified part

top-down design with autodesk® inventor™ using skeletal modelingwidom-assoc.com/ma301-1p.pdf ·...

Documents