Smooth, Automated Fastener Connections
I am always looking for ideas that eliminate the need to sketch and apply similar features in multiple files, such as mating holes in assemblies. Manually managing common features in assemblies can be tedious and is begging for mismatches.
Bolted Connection Generator in Autodesk Inventor® was developed to solve this problem and to automate the insertion and maintenance of related hardware. It’s not perfect, but it is a powerful tool that can be leveraged to streamline the design process.
Here’s what I want to discuss:
- What is the Bolted Connection Generator?
- Leveraging the Connection Features
What is the Bolted Connection Generator?
Autodesk developed a great set of tools that automate various tasks Inventor users need to perform. These are the Design Accelerators, found under the Design ribbon tab, and offer a wealth of capabilities and power.
The Bolted Connection Generator is one of my favorites from this collection. It was designed to create fastener connections in the assembly environment. It pulls components from the Content Center and leverages the Hole tool and Assembly Constraints to complete the process. All necessary features such as threaded holes are inserted into each relevant part file. Even when you are joining multiple parts together in a single location, the generator will apply the features to as many affected parts that it detects.
How Does the Bolted Connection Generator Work?
For each connection made, Inventor creates a new assembly file and adds all relevant fasteners. The positions of these are maintained through iMates found in the fastener part files and those generated during the hole feature process.
Figure 1: The Bolted Connection assembly file structure.
The Bolted Connection Generator Dialog Box
The generator uses a dialog box to guide the user in creating the hole feature and placing the fasteners. The dialog is fairly well developed and if you are paying attention, requires little training to operate properly.
Figure 2: The Bolted Connection Generator dialog box.
Briefly described, the relevant features include (from left to right):
- Type – Blind and Through-All
- Placement – Linear, Concentric, Existing Hole, and On Point
- Thread specifications
- Fastener selection and arrangement
Tip: Below all of these is a Templates Library section, which allows users to create a named template representing their fastener selection. When the generator is used numerous times to create additional similar connections, this gem helps reduce the number of steps dramatically. Add creates a named template from the existing connection in the dialog, and Set allows users to replace the connection details with those in the named template.
As users work through the dialog, they select start and termination planes for the connection and features that Inventor will use to develop the assembly and size the fasteners properly. In Figure 4, existing holes in the furnished frame flanges were used to place the connection.
Editing the Connection
Connections can be edited and deleted through the assembly context menu. Simply pick an assembly and then select ‘Edit using Design Accelerator’ near the top of the right-click menu.
Figure 3: The Edit option on the Assembly Context menu. Notice Delete option is available as well.
Leveraging the Connection Features
You could create hole features yourself in the assembly, but these features are not applied to the parts, and only appear at the assembly level and above. As you might imagine, this is useless if you want part drawings and model exports to reflect the true intended model definition.
The power of the Bolted Connection lies in the fact that Inventor will insert and maintain the hole features it creates into each relevant part file. This is a powerful method of maintaining fastener holes throughout the assembly design.
Figure 4: Notice here that no fasteners have to be selected. The Connection Generator can simply be used to transfer holes to each part.
In Figures 2 and 4 you can see that we have developed a single connection. Ideally, we’d like to duplicate these in areas of the design where the placement is clearly patterned or mirrored.
There are two main methods of duplicating the Bolted Connections.
Using the Follow Pattern Option
This is a gem of an enhancement to the Bolted Connection Generator and is available when using the ‘By Hole’ placement option. Checking this allows users to select an existing Hole Pattern, whereupon Inventor will fill the pattern with the selected fasteners and create the holes in all remaining parts being assembled. The hole features as well as the fasteners are maintained within a single Bolted Connection in the Assembly Browser.
Figure 5: Using the Follow Pattern option to automate the patterning of fasteners and holes. This is the best method as it creates all holes in all parts automatically.
Tip: Using this option depends on the existence of a hole pattern in an existing component. There are many instances where the hole placement is clearly best decided in the assembly rather than in the part. However, in areas where hole placement can be decided (or should be decided) in the part, then create the hole and patterns there. This will permit the greatest amount of automation when using the Bolted Connection Generator.
The only drawback that still exists in the generator is that Inventor is detecting the Pattern parameters, and not the hole feature data. In Figure 5, the selected holes are sized for 1/2” bolts, but the generator has no clue.
Using Assembly Patterns
Associative Patterns
If you are using an older version of Inventor or leveraging patterns that are not related to hole features specifically, then this is the next best alternative. Inventor will detect the Pattern from a Part file, and hand off the parameters to the assembly pattern being created.
After the Bolted Connection assembly file is in place, simply use the Assembly Pattern tool to duplicate the fastener assembly. The Associative tab will allow users to pick the part’s pattern feature from either the graphics window or the expanded model view of the Assembly Browser. Inventor will automatically create a matching fastener pattern in the assembly. Since it’s associative, when the part’s pattern updates, so will the assembly.
Figure 6: Using the Associative Pattern tool to extract the pattern information from the part. Here I have used the patterned mounting faces in the Part file to drive the patterned mounting fasteners in the Assembly.
Non-Associative Patterns
Lastly, users can add a Bolted Connection to an existing assembly pattern by simply editing the pattern and selecting the newly created fastener, or create an entirely new assembly pattern if needed.
The main problem with using assembly patterns to duplicate Bolted Connections is that only the fasteners are duplicated, not the holes. The holes will have to be duplicated in a similar manner from within the part (see below).
Figure 7: The unfortunate tradeoff of patterning Bolted Connections: Hole features are not duplicated in the part.
Duplicating the Matching Holes in the Part File
This section applies to using the Pattern Components tool in the assembly environment in situations where the Bolted Connection Generator’s ‘Follow Pattern’ option is, well, not an option.
You can create a pattern in the part file to duplicate the hole features that were created with the Bolted Connection Generator. You can mirror these holes as well in areas of symmetry. These patterns will update as the assembly updates.
Closing Thoughts
The Bolted Connection Generator is a fantastic tool for what it was designed to do—automate the fastener installation process. Moreover, I feel that the application of the resulting hole features in the assembled components is the most powerful part of this tool. The not-too-recent addition of the ‘Follow Pattern’ option is utterly beautiful.
The generator allows users to place the joining components where they are needed, and then hand back the respective fastener location from the optimum component placement.
The falloff in this entire process is at the assembly level. Inventor should be able to detect the existence of the hole feature in the Bolted Connection when it is patterned in the assembly, and apply it to the respective components as needed. You are not selecting a fastener assembly to pattern, you are selecting a ‘Bolted Connection,’ and it has a hole feature, too. This issue was addressed well within the Bolted Connection Generator, but not sufficiently in the assembly pattern tool.
Until this problem is addressed, users can continue to pass the holes into the part using the Generator, and then pattern them in the part as needed.
Figure 8: The Bolted Connection’s engineering calculator
There are more features in the tool such as the engineering calculator to answer basic questions about the fastener joint and the design loads as well. All this goes together to make the Bolted Connection Generator one of my favorite Design Accelerators in Autodesk Inventor.
