The transition from 3D designed sheet metal part through to the manufactured component can have many stages, with each adding time, cost, and possibility for human error. Any link in the chain that can be removed can pay dividends. In this article we explore the basics of 3D unfolding and how JETCAM’s new 3D unfolding module for JETCAM Expert can cut lead times by accelerating the time from part to production as well as improving the quality of the finished part.
3D unfolding software is used to convert complex 3D models of sheet metal parts into accurate and flat patterns. It streamlines the transition from design to production by employing algorithms that account for material properties and bending characteristics. The software ensures that the flat pattern compensates correctly for bend allowances and bend deductions. This process removes the risk of errors that can arise during manual calculations, optimising material utilisation and reducing waste.
Effectively, 3D unfolding software acts as a critical interface between digital designs and manufactured flat components prior to bending, ensuring the highest levels of accuracy and productivity in the fabrication of sheet metal parts. By leveraging such technology, you can guarantee that each fold, cut, and bend performed in reality aligns with the original digital part design.
Several 3D file formats are instrumental in bridging the gap between design and fabrication, each serving specific roles depending on the workflow requirements. Here are some of the most popular 3D sheet metal part file formats:
The STEP (Standard for the Exchange of Product model data) format is universally recognised for its ability to store assembly structures as well as geometric data, making it a preferred choice for interoperability between different CAD systems. It uses either .stp or .step file extensions. IGES (Initial Graphics Exchange Specification), although older, is still widely used for its flexibility in sharing vector-based CAD drawings.
The .sat file extension stands for "Standard ACIS Text," and is a proprietary and versatile 3D file format used widely in the industry. Originating from the ACIS 3D Geometric Modeler (or simply ACIS), developed by Spatial Corporation, the .sat file format is designed to facilitate the exchange of 3D data amongst different CAD, CAM, and CAE software platforms.
The .sldprt file extension is associated with SolidWorks Part File, a format native to SolidWorks software, with .sldasm relating to assemblies.
During the bending process the material is stretched on its outer side and compressed on its inner side. The neutral line, where there is neither compression nor elongation, cannot be calculated using geometry alone. To calculate a correct unfolding length for a radius, it is necessary to use bend compensation factors.
The ‘K-factor’ is a value that depend on the bending angle and the ratio between the inner radius and the thickness. JETCAM Unfolding software provides a material file that contains values that generate accurate unfolding in most cases. However, the K-factor values depend on many different parameters. Decreasing material strength, sheet thickness and bending tool friction can result in differing K-factors.
Accurate K-factors ensure that the final bent component adheres closely to the intended design specifications, with minimal requirement for additional processing or compensation for deviations. It is, therefore, a critical factor in the optimisation of production processes, material utilisation, and ensuring the finished part remains of high quality.
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Factors Affecting K-Factor
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In addition to creating an accurate ‘flat blank’ that has modified dimensions to take the changes in the material due to bending into account, being able to pass additional information inside the outputted DXF file can be useful. For example, including bend lines on different layers or colours within the DXF can mean that they are bypassed and ignored during nesting, but still available for staff to view further on in the manufacturing process. JETCAM Expert can allow these to be produced on custom reports using the Advanced Reports Designer. Other information, such as text, can be set for marking or use on labels.
3D files may contain either a single item, or a collection of parts, forming an ‘assembly’. JETCAM's Unfolder allows assemblies to be split down into their individual parts. The operator can then discard non sheet metal items and continue with unfolding the parts that will then move onto nesting. Additional functions include the ability to split a single face into separate faces, merge faces, or perform ‘step bends’; where a single large radius bend is changed into several smaller bend operations. This is also referred to as bump bending or radius bending.
The JETCAM Unfolding module can operate in several different ways:
The ability to quickly convert 3D CAD files into 2D DXFs provide manufacturers with opportunities to simplify and streamline their workflow. The JETCAM Unfolding module removes the complexity of calculating K Factor, quickly delivering automation from the 3D file through to NC code, helping to improve your overall lead times and maintaining part quality in the process.