Inventor Frame Generator: Designing Structural Frameworks and Weldments

Structural frameworks — machine frames, conveyor structures, steel fabrications, racking systems, safety guards — are a staple of mechanical engineering design. Manually modelling each individual member, calculating intersection points, managing end treatments, and generating cut lists would be enormously time-consuming if done from scratch for every project. Inventor’s Frame Generator automates this process, allowing engineers to define skeleton geometry and let the software place standard section profiles along it, handle mitre joints and end treatments, generate weld beads, and produce cut lists that directly feed manufacturing documentation.

This guide covers the complete Frame Generator workflow: setting up skeleton geometry, inserting and configuring frame members, managing joints and end treatments, creating weld features, and extracting the documentation that fabricators need.

Autodesk Inventor Professional is available from GetRenewedTech for £39.99.

What Is Frame Generator?

Frame Generator is a design accelerator in Inventor Professional that creates frame structures from user-defined skeleton geometry. The process works in two stages:

1. Define the skeleton: Create 2D or 3D sketch geometry representing the centrelines of frame members
2. Insert frame members: Use Frame Generator to place standard sections along the skeleton lines, with automatic joint management

The resulting frame is a weldment assembly — a special type of Inventor assembly where the individual members are represented as parts within an assembly, with appropriate weld features and a bill of materials structured for fabrication.

Setting Up the Skeleton

The skeleton is the geometric backbone of your frame. It’s typically created as a 3D sketch in a new Inventor part file that will become the frame assembly context. The skeleton consists of:

• Lines: Representing horizontal, vertical, and diagonal members
• Points: At joints where members meet
• Planes: Optionally used to define reference surfaces for the frame

Skeleton geometry should be fully constrained and parametrically driven where possible. If the overall frame dimensions might change — a customer might require a frame 500mm longer — having the skeleton driven by parameters means the entire frame updates when you change a single value.

Skeleton Geometry Tips

• Draw skeleton lines at the centroid of the section profile, not at the edge. Frame Generator places sections centred on the skeleton line by default.
• Use construction geometry for reference but ensure the structural member lines are normal (not construction) geometry.
• Label key reference points and dimensions — this makes the skeleton readable by anyone who inherits the file.
• For very large or complex frames, consider using multiple sub-skeletons in separate part files linked into the frame assembly via iPart or reference geometry.

Inserting Frame Members

With your skeleton defined, open the Frame Generator by navigating to the Design tab and selecting Frame > Insert. The Frame Member dialogue appears, with the following key settings:

Standard and Section

Select the structural standard applicable to your project. Inventor ships with a comprehensive library of structural sections organised by national and international standards:

• ISO: European standard I-beams (HEA, HEB, HEM, IPE), channels (UPN), hollow sections (RHS, CHS, SHS)
• BSI: British Standard sections (UC, UB, RSC, SHS)
• AISC: American standard sections (W-shapes, S-shapes, channels)
• DIN: German sections

For UK projects, the BSI or ISO library is typically appropriate. Select the section type (e.g., BSI > EN 10210 S355 > SHS) and then the specific size (e.g., 100x100x5 SHS).

Placement Method

Frame members can be inserted using several placement methods:

• Single Member: Click a single sketch line to place one member along it
• Multiple Members: Click multiple lines in sequence to place members along all of them
• Frame Member Loop: Click to select a closed loop of sketch lines and Frame Generator places members along all of them as a connected sequence

For most frame designs, the Multiple Members method is most efficient — select all horizontal members, insert them with the chosen section, then select all vertical members and insert them, and so on by member type.

Orientation

The section orientation parameter rotates the section about the member axis. For sections that have a preferred orientation (I-beams should generally have their web vertical; channels should face a specific direction), set the rotation angle here. A 90° rotation increments the section to the next quarter turn

Orientation

The section orientation parameter rotates the section about the member axis. For sections that have a preferred orientation (I-beams should generally have their web vertical; channels should face a specific direction), set the rotation angle here. A 90° rotation increments the section to the next quarter turn. You can also use a custom reference vector for precise control.

Offset

By default, Inventor places the section centroid on the skeleton line. The offset parameter shifts the section perpendicular to its axis — useful when you want the outer face of a member to align with a reference plane rather than the centreline. For example, if you’re designing a frame where the top face of all horizontal members must be flush, apply a vertical offset equal to half the section depth.

Managing Joints and End Treatments

Where frame members meet, Inventor needs to resolve the joint — cutting or notching members so they fit together correctly. The Change Member tool and the End Treatments dialogue handle this automatically for most configurations.

End Treatment Types

• Butt: One member is cut square and butts against the face of another — the simplest treatment, used where two members meet at right angles
• Mitre: Both members are cut at 45° so that a corner joint is formed flush on the outer faces — common for frame corners visible in the finished product
• Notch: One member has material removed so that it fits around another, commonly used where a secondary member crosses a primary one
• Cope: A portion of the flange or web is removed from one member to allow it to pass another — typical with I-beams and channels
• Trim to Frame: Inventor automatically trims the member to the appropriate intersection with other geometry

To apply end treatments, select the Change End Treatment tool, select the member, and then select the affected end. Choose the treatment type from the dropdown and Inventor resolves the joint geometry. For complex intersections — three or more members meeting at a node — you may need to apply treatments sequentially, starting with the primary member and working outward.

Notching and Coping for Hollow Sections

Hollow sections (RHS, CHS, SHS) are frequently used in welded frames, and they require careful attention to joint treatment. A common configuration is a secondary RHS member meeting a primary RHS member at 90°. If you simply butt them together, there’s a gap between the outer face of the secondary and the outer face of the primary. The Notch end treatment cuts a saddle profile into the end of the secondary member that wraps around the profile of the primary, producing a proper fillet weld preparation.

For CHS-to-CHS joints, Inventor can generate the complex curved saddle cut automatically. This alone saves hours of manual solid modelling for each joint — on a frame with 20 circular hollow section joints, the time saving is substantial.

Creating Weld Beads

With frame members placed and end treatments applied, you can add weld features to represent the joints. Navigate to the Weld tab in the frame environment and select the weld type:

• Fillet weld: The most common type for fabricated frames — placed at the junction between two members
• Groove weld: Used for full-penetration butt joints, common in structural steelwork where full-strength joints are required
• Cosmetic weld: A visual representation only, used where you want to show a weld in drawings without modelling the actual bead geometry

Weld beads appear in the model and are included in the bill of materials. They can be annotated on drawings with welding symbols following ISO 2553 or AWS conventions, which is particularly important for fabrication documentation on UK structural projects that must comply with BS EN 1090 execution requirements.

Generating the Cut List

One of the most valuable outputs from Frame Generator is the automatic cut list. This is different from a standard bill of materials — it lists each unique frame member with its section profile, material, length, quantity, and any end treatment details. To access it, navigate to the Manage tab and open the Parts List dialogue, then select the frame assembly.

The cut list can be placed directly onto a drawing sheet as a table. It updates automatically when you modify the frame — change a member from 1200mm to 1350mm and the cut list reflects it immediately. For fabrication shops, this directly feeds procurement and cutting schedules, reducing the likelihood of transcription errors that can result in undersized or oversized members reaching the shop floor.

Customising the Cut List Columns

Inventor allows you to customise which properties appear in the cut list. Standard columns include:

• Item number
• Quantity
• Section profile (e.g., SHS 100x100x5)
• Material
• Cut length
• End treatments
• Mass per piece and total mass

If your organisation uses a custom property (e.g., a heat number field for traceability, or a surface treatment field for galvanising specification), you can add it as a custom column in the Parts List editor. This information then travels with the model through the iProperties panel and can be exported to CSV for use in ERP or procurement systems.

Weldment Documentation

Frame Generator assemblies work seamlessly with Inventor’s drawing environment. Create an IDW or DXF drawing from the frame assembly and you can place:

• Orthographic views showing the complete frame with dimension annotations
• Detail views of complex joint areas
• Section views through member intersections
• The cut list / parts list table
• Weld symbol annotations on joints
• General arrangement notes and material specifications

For UK fabrication projects, the drawing package typically needs to reference BS EN ISO 2553 for weld symbols and BS EN 10025 or BS EN 10210 for section material grades. These references can be added to the drawing title block and general notes, and once set up in a template, they appear automatically on every frame drawing produced from that template.

Working with Weldment Environments

When you convert a frame assembly to a weldment, Inventor treats it as a single fabricated component rather than a collection of individual parts. This distinction matters for manufacturing: a weldment is a single manufactured item, listed once in a parent assembly’s BOM, whereas a non-weldment frame assembly would list every individual member separately.

To convert, right-click the frame assembly in the browser tree and select Convert to Weldment. This unlocks the weldment-specific features: machining operations that can be applied after welding (simulating post-weld machining of mounting faces, for example) and weld preparation that tracks welding sequence.

Practical Tips for Frame Generator Efficiency

Teams that use Frame Generator regularly develop a set of workflow habits that keep projects clean and efficient:

• Always start with a skeleton: Never try to place frame members by picking faces of existing solid geometry. The skeleton-first approach keeps the frame fully parametric and easy to modify.
• Name your skeleton lines: In the sketch browser, rename key lines to reflect their role (e.g., “Top Rail Left”, “Vertical Post Front-Left”). This makes selecting specific members much faster, particularly in complex frames.
• Use consistent section origins: If you mix section types (I-beams and RHS together, for example), pay attention to where the origin point of each section sits — they may not align the same way, leading to unexpected offsets at joints.
• Create a standard section library: If your organisation repeatedly uses the same set of sections (e.g., always SHS 60x60x4 and SHS 100x100x5 for guards and conveyors), create a custom Frame Generator library containing only those sections. This prevents engineers from accidentally specifying non-standard profiles.
• Validate member lengths against raw stock: Standard structural steel comes in 6m or 12m lengths. If your cut list contains a 6,200mm member, that’s a problem — it requires a special order or a splice joint. A quick scan of the cut list at design stage can flag this before it becomes a procurement headache.

Frame Generator vs Manual Modelling

The question sometimes arises: when should you use Frame Generator and when is it better to model frame members manually as extrusions? The answer depends on complexity and the need for a cut list.

For simple frames of four or five members where the geometry is fixed and unlikely to change, manual extrusion is fast and straightforward. But for anything with more than ten members, parametric constraints, or the need for a cut list that updates automatically, Frame Generator is the right tool. The upfront investment in setting up the skeleton pays back many times over when the client changes the frame dimensions at detail design stage and you need to update the model in minutes rather than hours.

Getting Started with Inventor Frame Generator

Frame Generator is available in all versions of Inventor Professional. If you’re new to Inventor or considering upgrading, Autodesk Inventor Professional is available at GetRenewedTech for £39.99 — a cost-effective way to access the full suite of tools including Frame Generator, Tube and Pipe, and the complete weldment environment.

For teams that also work with Autodesk’s wider product design toolkit, the Autodesk PDMC Collection at £149.99 bundles Inventor Professional with Fusion, Vault, and other tools in a single package.

Summary

Inventor’s Frame Generator is an indispensable tool for any mechanical engineer who designs structural frameworks, machine bases, conveyor structures, or fabricated weldments. By handling the tedious geometry of member placement, intersection resolution, and end treatments automatically, it frees engineers to focus on structural decisions rather than modelling mechanics. The automatic cut list and seamless drawing integration close the loop from concept to fabrication documentation, making the entire workflow faster, more accurate, and far less error-prone than traditional approaches.