4 Best Practices for Sheet Metal Design Modeling to Reduce Fabrication Costs

Feature based parametric 3D models and 2D drawings share parent-child relationships as drawings are generated from models. This bi-directional parametric link between models and drawings allows the design engineer to evaluate changes in 2D sheet metal shop drawings and 3D models simultaneously.

Complex sheet metal components use multiple features to convey design intent and show part functionality. Figure 1 shows a typical sheet metal component model with design features.

Figure 1: Sheet metal features and their categories

If you are working on a single component, you can apply Design for Manufacturing (DFM) concepts and it directly conforms to standard manufacturing processes. Adherence to DFM guidelines for 3D models helps optimize manufacturing operations, such as nesting, bending, holes, and punching.

Benefits of using FBPM:

• Quick changes in parts with parametric 3D designs
• Better alignment of features with shape, geometry, and dimensions
• Unlock opportunities for design automation and rule-based part modeling
• Save 70-90% of time spent in creating separate 2D detailed drawings
• Uplift design and manufacturing drawings quality
• Enhance inter-team communication through a concurrent environment
• Parametric modeling of sheet metal industrial equipment for plant reengineering

A top-down approach is used to model a product with multi-component sheet metal parts. This design approach allows you to create a geometric frame with space constraints assigned to all parts and sub-assemblies. It builds the master model in such a way that it can be used for CTO and ETO feature customization for products such as doors and windows, metal, and wooden furniture, etc.

CAD tools like SolidWorks, Inventor, and Creo allow a top-down approach for very large and complex assemblies. These include heavy-duty bulk material handling plants having 10,000+ components in a single master model. These CAD platforms are also fit to handle small assemblies of sheet metal doorframe having not more than 20 to 30 parts with dexterity.

Figure 2: Top-down design approach for a small sheet metal assembly

Advantages of the top-down design approach:

• Accommodate a large number of components having parametric design features with constraints for customization
• Promote large-scale design automation
• Ease of manipulating space constraints and developing individual parts
• Evaluate changes in dimensions, shapes, etc., and their impact on other parts and assembly
• Meet functional, spatial, and aesthetic aspects of design
• Faster installation of walkway and hopper with a top-down design approach

Design for Manufacturing (DFM) and Design for Manufacturing and Assembly (DFMA) allow design engineers to capture requirements as per shop floor capabilities. Following these guidelines nullifies most of the design errors that arise from nonconformity with the standard shop floor practices.

DFM guidelines help design engineers bridge the gap between the real world and the ideal world while creating features like holes, slots, bends, end reliefs, etc. Figures 3 and 4 are examples of hole creation and bend radius creation, respectively, in sheet metal.

Figure 3: Punching holes in sheet metal plates according to DFM rules

Figure 4: Bending failure in sheet metal plate without considering grain direction

With DFMA guidelines, engineers are empowered to optimize designs by controlling the number of components and steps involved in manufacturing. With fewer components, fabricators can save costs and speed up the production process due to the ease of assembly and fabrication.

Figure 5: Considering a number of sheet metal parts in the assembly as per DFM guidelines

Advantages of DFM and DFMA

• Design by considering 360-degree manufacturing process aspects during the design
• Almost zero design iterations arise from the shop floor
• Design parts that meet the assembly process requirements and shop floor facilities
• Optimize the design assembly by reducing the number of parts
• Saves cost of a product by 70-80% with fewer components
• Improve manufacturing speed by over 30%
• Eliminate manufacturing rework using DFM rules

Advancement in tools like SolidWorks ensures incorporation of a high level of manufacturing and quality information in models. They have provisions to annotate models with product manufacturing information and create a single source of truth for all design and manufacturing stakeholders. By saving all information in one place, this concept has significant potential to meet the needs of Industry 4.0.

Figure 6: MBD representation of a sheet metal plate

A complete set of product information for manufacturing and suppliers, such as quality measurement, tolerances, other footnotes, etc., is communicated using a comprehensive 3D model. This is called the Model-Based Definition (MBD) approach.

MBD creates a single, reliable CAD file for the entire value chain to improve collaboration, save time, and prevent errors. If used efficiently along with DFM, DFMA, FBPM, and the top-down approach, MBD can prove to be significantly advantageous to manufacturers.

Advantages of MBD

• Ease in information management for manufacturing, quality, suppliers, and product catalog
• Eliminate the need to create 2D-detailed drawings for component manufacturing
• Improve speed from design to manufacturing by more than 80%
• Effective ways of representing parts or products to all stakeholders, including customers
• Enhance downstream/upstream coordination and communication for improved quality
• Reduce errors in communication and part manufacturing
• MBD reduces engineering lead time by 50% for electroform systems manufacturers