This blog is Part 3 of a multi-part blog and video series examining the difference of creating a simple bookcase using Top-Down Assembly modeling and Multi-body Part Design techniques. In this blog, we will compare the results and differences between the two methods and examine the output that is generated by each.
Now that we have created this same bookcase using 2 separate methods, what is the difference? They both are controlled by a single 3D sketch, and they both have the same configurations (I’ll address the configurations in future blogs and videos in this series). The question is: “Is it better to use Top-Down Assembly modeling OR multi-body part design technique to create the bookcase?”
The answer is:
What type of output is required? The method you choose depends on the way your manufacturing information needs to be displayed in drawings and product documentation. Let’s compare the two.
With an Assembly:
- You have access to a BOM which pulls information from the individual part files’ File Properties.
- Each panel has its own part file. Some companies require each part to have its own file represented on disk in order to comply with certain national and international standards for document control.
- Parts are created within the context of the assembly and have external references.
- Individual components can be detailed and ballooned.
- Exploded views are available.
- Balloons are available
- Motion simulation is possible.
- Mates are used to associate components.
- When dealing with Large Assemblies there are several techniques for enhancing performance.
With a multi- body part using the Weldment feature:
- You have access to the Cut-list (using the Weldment Feature) which has extra properties available, such as bounding box information which provides individual body size information such as Description, Length, Width, and Volume.
- All of the bodies representing each part are in one file. (steps can be taken to save the individual bodies)
- All bodies reside within the part file, no external references.
- Individual bodies can be detailed and ballooned. (a few more steps than an assembly are required)
- Exploded views available.
- Balloons are available.
- Motion simulation is not possible.
- No mate features are required.
- Large multi-body parts have slower performance than the same product modeled in an assembly.
As you can see there are similarities and differences to both. The big difference lies between using a BOM or a Cut-list. When activating the Weldment Feature in a part, as was mentioned above, a cut-list folder is added to the Feature Manager Design tree.
Refer to the image above for details on using the Weldment Feature in the multi-body part design. Each folder in the cut-list can be renamed. In this case I gave names for the different panels. Each folder holds the solid body of the item(s), can hold a separate material, and in this example holds a 3D bounding box sketch. If you right click on a folder you can select Create Bounding Box from the contextual menu. This adds a 3D sketch into that item’s folder and adds several custom cut-list properties to that item – Description, 3D Bounding Box Thickness, 3D Bounding Box Width, 3D Bounding Box Length, and 3D Bounding Box Volume. If you right click on any folder and choose Properties from the contextual menu you will see the entire cut-list table with all of the information from the properties. These items can be displayed on a drawing that is referencing the cut-lit of this part. This information is valuable for this kind of product and may be more useful than using a BOM with an assembly drawing. I have created 2 drawings which are displayed below. One is the drawing from the Assembly using a BOM, and the other is from the Multi-Body method utilizing the cut-list. Both are quite different and display information in different ways. As I mentioned previously, the method you choose depends upon the kind of output your company needs.
Both the BOM and the cut-list are populated from custom properties found in the part files. Using the cut-list that is created from the Weldment Feature can capture a lot of manufacturing information pretty quickly. With the Assembly method, each part needs to have custom properties defined in each file. Using template files with the required properties already defined, can help to speed that up. The dimensional sizes would need to be detailed for each part, whereas the bounding box provides that information easily accessible in the cut-list table.
From the modeling standpoint, creating either of the bookcase methods takes about the same amount of time, but getting the drawings to look the way you want based on business needs, will determine which method you should choose to get the best results.
Both the BOM for the assembly and the cut list for the multi-body part use an Excel based table to organize information. Columns can be added by right clicking a column header and choosing Insert from the contextual menu. When a column is added, the user has the ability to assign the new column to a file properties value. The choices are a little different between the table types. It is easier to modify the file properties with the cut list items for the multi-body version than it is for the BOM in the Assembly. This is because each individual file in the assembly has to be opened up and the File Properties added and modified. All of this is done within the multi-body part by modifying the properties in the cut list by right clicking a cut list folder and choosing Properties from the contextual menu. This opens up the dialogue box to modify the properties of all the cut list items in one easy to access location. Configurations are also easier to define in the multi-body part.
Which is right for you?
Assembly version with BOM; each individual component must have file properties defined at the part level and configurations have to be defined at the assembly level and the part level. Takes a little more time to set up, results in each panel having its own file, and BOM referencing file properties defined in each component.
Multi-body part with Cut List; the properties of each panel are defined in one single table that represents all of the cut list items. Configurations are easier to define as well with the use of one single Modify Configurations dialogue box. Faster to create, results in cut list properties managed in a single table with extra properties defined from bounding box data. If individual part files are needed, extra steps would have to be taken (using Save Bodies from the contextual menu by right clicking on the Cut-List folder will save bodies into separate files).
Either method is valid and will result in a very flexible system of shelves that represent the sizes in our office that I now can use in the office model.
Stay tuned for more blogs and videos in this series. Topics covered next will be Library Feature Parts and Configurations!