- Introduction
- Key Takeaways
- What is a Sheet Metal Drawing?
- 2D Sheet Metal Drawings
- 3D Sheet Metal Drawings
- Summary
Introduction
Good sheet metal manufacturing relies on good sheet metal drawings. Sheet metal drawings provide a representation of a component, detailing precise dimensions, tolerances and fabrication processes to be followed in production. Having accurate drawings of the correct type allows the manufacturer to quote for and manufacture a component cost effectively and to a high standard.
On this page, we’ll look at how to produce high quality 2D, 3D drawings and what PDF drawings are used for.
Key Takeaways
- 3D drawings are normally best for accurate and efficient manufacturing. 2D drawings can be used in place of 3D drawings in some situations. 2D drawings are also a requirement in some situations.
- Flat pattern drawings are essential for parts that will be CNC bent.
- Drawings must be submitted in a manufacturer supported file format. DXF is the best choice for 2D drawings. STP and STEP are the best choices for 3D drawings.
What is a Sheet Metal Drawing?
Sheet metal drawings are used to quote for the manufacture of a component and in the actual manufacture of a component. They are made with design software such as SolidWorks, AutoCAD and Alibre Expert. Drawings provide precise details for dimensions, tolerances and manufacturing processes. They are used to program CNC machines, and engineers also follow them when designing manufacturing processes.
Here are some important basic requirements:
- Designs should be submitted in the right format for the fabrication processes that will be used. They can be supplied as either 2D or 3D drawings. PDFs are also used.
- They should also be supplied in a file format that is supported by the manufacturer.
- A separate drawing should be provided for each component that will be manufactured if an assembly has more than one component.
2D Drawings
Fig. 1: 2D Drawing Example
A 2D drawing is a flat representation of a sheet metal component. It includes dimensions, tolerances and annotations that detail how a metal component will be fabricated. 2D drawings are useful for simple parts because they are quick to generate and interpret. Designs can also be supplied directly to CNC machines.
At Komacut, we primarily work with 3D drawings. It is always helpful, however, if 2D drawings are supplied alongside 3D drawings. They can also be used in place of 3D drawings in some situations. 2D drawings are also essential at Komacut for components that will be laser cut, bent or CNC turned or fabricated in certain other ways.
3D Drawings
A 3D drawing is a digital representation of a sheet metal component that can be looked at from any angle. Unlike 2D drawings, 3D models display depth as well as height and width. They are used for visualizing components and assemblies and are particularly useful for components and assemblies with complex geometry.
At Komacut, we use 3D drawings for accurate design analysis and for calculations related to design for manufacturability. We primarily work with 3D sheet metal drawings.
Komacut can convert your 2D files to 3D and update old 3D designs to the latest version with our 3D CAD drafting and drawing revision service.
Fig. 2: 3D Drawing Example
PDF Files
PDF drawing files are often used in sheet metal fabrication for record keeping, version control and in approvals processes. PDFs are helpful because they are non-editable and secure. PDFs can be created as a reference point and referred to when needed.
Fig. 3: PDF Drawing Example
2D Sheet Metal Drawings
2D drawings give a flat representation of a sheet metal component. They are particularly useful for simple components.
At Komacut, we primarily work with 3D drawings. It is, however, always helpful to have 2D drawings as well as 3D drawings when they’re available. We also require 2D drawings for components that will undergo certain fabrication processes.
At Komacut, we require 2D drawings for:
- Components that will be bent, laser cut or CNC turned.
- Components that feature countersinks, counterbores, threaded holes, bend angles, blind holes or laser engraving.
- Components with milled features, such as edge fillets or edge chamfers.
Key Components of a 2D Drawing:
2D drawings should be annotated with all the information required in fabrication.
Some basic information that should be included is:
- Company name, part number and drawing revision number
- Scale and measurement units
- Material information
The drawing should also show all the dimensions and features of the component and be annotated to show the fabrication processes that will be applied. A complete 2D sheet metal drawing will clearly show:
- The dimensions of all bends, cuts, holes, countersinks, counterbores, flanges and other formed features.
- Critical tolerances, including dimensional, angular and other tolerances.
- Material thickness and thickness tolerances
Designs should also provide detailed information about surface finishing. Basic information about the type of finish should be shown as well as detailed information, such as color codes for colored finishes.
Fig. 4: 2D View (PDF), Unfolding
Isometric Views of the Part
It’s important to show multiple angles of a component. Normally, it’s best to provide three different angles.
Tolerances
Tolerances should be detailed on all sheet metal drawings.
It’s important not to set tolerances that are too strict. Advancements in manufacturing techniques have made it possible to achieve tight tolerances, but doing so can be more expensive. When you set tolerances, you should align them with the actual requirements and avoid using tight tolerances that do not add value to the function or structure of the component.
Tolerance markup methods:
- General tolerances for unspecified dimensions are normally displayed in the title block of the drawing. For example, the title block might read, “Unless otherwise specified, all dimensions are ± 0.1 mm.”
- Tolerances for specific dimensions are displayed with the dimension they apply to. For example, a specific dimension might be marked as 50.0 mm ± 0.2 mm.
Fig. 5: 2D View (PDF), Oblique View
Features
All features should be clearly identified, supplied with clear and accurate dimensions and shown with any relevant specifications. Holes, for example, should be identified as either threaded or through holes, with specifications provided for threading in threaded holes.
Fig. 6: 2D View (PDF), Chamfer
Flat Pattern Drawings and CNC Bent Parts
Flat pattern diagrams are used in CNC bending. A flat pattern drawing is a 2D overhead view of a sheet metal component. They are helpful in the planning stage, allowing a manufacturer to plan material use more quickly, speeding up quoting time and fabrication planning time.
As other special considerations, drawings for parts that will be bent should also feature:
- Angular tolerances
- Relevant isometric views – isometric views are important for parts that will be bent
Fig. 7: 2D View (PDF) - CNC Bent Part
Supported File Formats
2D drawings should be supplied in a manufacturer supported type. At Komacut, we work with DWG and DXF files. These are standard file types used for 2D drawings, with DXF being the most widely used. Almost all CAD software can import and export DXF files using a CAM or DXF plugin. This makes the DXF file a universal format for manufacturers all around the world.
Parts with bends should be exported using the given DXF layer map.
| Layer | Description |
|---|---|
| X Layer - 0F | Solid geometry Everything except defined in the following layers |
| X Layer 1F | Bend Down bend lines only No other entities |
| X Layer 2F | Bend up bend lines only No other entities |
| X Layer 3F | Bounding Box layer |
| X Layer 4F | Sketches |
Table 1: Layer Specifications
Different CAD software can have more or fewer options available for layer mapping. The option given above is available with most applications.
PDF copies of all designs should also be supplied for reference, record keeping and version control.
3D Sheet Metal Drawings
At Komacut, we mainly work with 3D drawings. With 3D drawings, we’re able to perform more calculations for accurate design for manufacturability feedback and optimal part pricing. Having 3D drawings allows for accurate nesting, part simulation and other processes.
3D drawings should be annotated with all information required in fabrication.
The same basic information should be provided as with 2D drawings:
- Company name, part number and drawing revision number
- Scale and measurement units
- Material information
Fig. 8: 3D View - Sheet Metal Part
The drawing should also show all the dimensions and features of the component and be annotated to show the fabrication processes that will be applied. The drawing should show:
- The dimensions of all bends, cuts, holes, countersinks, counterbores, flanges and other formed features.
- Critical tolerances, including dimensional and angular tolerances.
- Material thickness and thickness tolerances
Designs should also provide the same detailed information about surface finishing as 2D drawings.
Komacut can update your old 3D drawings to the latest version and convert 2D drawings to 3D with our 3D CAD drafting and drawing revision service.
Tolerances and Features
All features should be identified by type, shown with all necessary dimensions and with any relevant specifications. Tolerances should also be detailed in 3D sheet metal drawings. See the information the 2D drawing section above about tolerances and sheet metal component design.
Fig. 9: 3D View - Part Analysis
Supported File Formats
3D sheet metal component drawings should be made with purpose built sheet metal design software and supplied in a manufacturer supported file format. Drawings should also be solid objects and not planes.
Some widely accepted 3D file formats are:
- STP (File Extension: .stp)
- STEP (File extension: .step)
- SolidWorks (File extension: .sldprt)
Note that it’s best to use STP or STEP files with 3D drawings because these are universally accepted file format that can be converted without losing detail or being corrupted.
| Drawing Type | Typical File Format | Essential For | Special Considerations |
|---|---|---|---|
| 2D | DXF | CNC bending | Isometric views required Flat pattern drawings required for bent components |
| 3D | STP, STEP and SolidWorks | Complicated designs | 3D drawings allow a manufacturer to better optimize designs for manufacturability |
Table 2: Drawing Types and Formats for Manufacturing
Summary
High quality designs will save you time, help you avoid mistakes, and they could save you money in manufacturing. You can follow the guidelines we’ve set out here to make sure you’re addressing the key factors in sheet metal component designs. Make sure you always supply all the necessary details in your designs and that your designs match your fabricator’s requirements.