What is Your CAD File Type?

Your CAD software uses either a proprietary file format or an open format that satisfies a common standard. Importing different file types is a complicated process and you want to make sure that the imported file represents the part properly and that important characteristics have not been lost in the translation process. How a sheet metal fabrication shop processes customer files on the way to generating the code that runs the cutting and punching machines is a key factor in output quality and in how quickly they can deliver the required parts. Ideally the sheet metal CAD/CAM software will import customer files quickly and accurately to allow production of parts that correspond exactly to the original CAD files.

Common File Types

Merry Mechanization's SMP/IS software can import a wide variety of files, including those listed below, and can rapidly convert them for CNC machine use.

  • DXF - the .dxf (Drawing Exchange Format) file type is a common 2D file format that has become a standard for flat sheet metal part files. It is a text-based file type and can be read and generated by many CAD programs. SMP/IS can import this file type quickly and can display the imported part for review.
  • IGES - the .iges (Initial Graphics Exchange Specification) file format is a standards-based file type designed to allow 2D and 3D CAD files to be exchanged between different programs. SMP/IS can import IGES files and, if they are 3D files showing parts to be formed from sheet metal, it can flatten the parts to generate code for the cutting and punching machines.
  • SAT - the .sat (Standard ACIS Text) files are open format 3D files written in ASCII code. SMP/IS imports the text-based code and converts it to a 3D image that the sheet metal software can analyze and flatten into a part ready for production.
  • DWG - the .dwg file type is a native 2D and 3D file format for AutoCAD and a number of other CAD applications. DWG files may have versions that limit which applications can work with them. SMP/IS can import the file type and flatten the 3D images.
Depending on the file type and the type of part, additional steps may be necessary before the parts can be produced from sheet metal. SMP/IS allows operators to review the drawings, showing the imported files and the resulting parts. Different views are available, and imperfections or missing details can be corrected, a lot of times automatically. At this stage, operators can also decide how to flatten 3D parts so they can be produced from sheet metal.

Importing 3D files

After the importing process and the review, 2D sheet metal files are ready to be situated on a metal sheet, but 3D files have to go through several additional steps to produce the flat patterns for sheet metal parts. You have to generate a flat piece of sheet metal that can be formed into the original part while making allowances for bending and stretching. The SMP/IS software helps create such flattened files.

The first step is to specify the material and the material thickness. The bend radius specifies the inside radius of sheet metal bend and the K-factor gives how much the material will stretch on the outside bend. These four parameters allow the software to create the flattened drawing of a sheet metal part that, when formed according the selected bend radii, will become the formed part with the original dimensions.

SMP/IS shows you the original part and displays the required bends in a different color to visually see the contrast to the edges. Once the four parameters are set for each bend, the software carries out the required calculations and shows you the new flattened part. At that point you can again review the part drawing to make sure all the required features of the part are present. Once you accept the part, you can then further define the job by specifying how many of the parts you need and by situating them on the corresponding metal sheet.

When your sheet metal fabrication line uses powerful CAD/CAM software with many import features such as SMP/IS, importing files is quick and precise leading to fewer problems with parts down the road.

Key Factors in Successful Importing

Although most CAD/CAM software has the ability to draw sheet metal parts, if you have a CAD file of the part already, you’ll want to import them because you don't want to spend unnecessary time re-drawing the part from scratch. This will potentially add unwanted errors in the finished part by, for example, mistyping a dimension or incorrectly adding a hole in a place that shouldn’t have one. When you start with a common file type and use CAD/CAM software with many import features such as SMP/IS, you end up with a usable part drawing. But even then, there may be problems with the original file, versions may not match and features may not be reproducible during import. When you review the part after importing it, you have to look at the drawing in an organized way so that you can identify any problems.

The first thing to check is that all features of the original part have been imported. Check that all holes, edge configurations, profiles and similar features have been imported and that they are positioned correctly. Perhaps a layer was not transferred or lines were not recognized. If there are missing features, it may be easier to add them manually, or you may want to try re-importing the file.

A second key factor to check is the make-up of curves and shapes. Some CAD programs approximate curves and shapes with line segments or the drawing may have been prepared using such a software feature. While it may look smooth in the original application, when converted during the import process, such line segments may give a visibly uneven curve or a shape that is not smooth. Such problems can be corrected within the importing CAD program or in a powerful CAD/CAM software like SMP/IS with its unique CleanUp and CurveFit features.

Finally, it is important to check the precision of the new drawing. The original drawing may have placed features without specifying highly precise positions or, if it did, the precision may not have translated adequately during the import process. You'll have to check the precise placement of key part features on the imported drawing to make sure its precision is the same as the original drawing.
Over time, you will get more and more comfortable with the CAD/CAM sheet metal software to import your CAD files and gain trust that it is handling everything it needs to. You will, over time, skip a lot of these steps because you know SMP/IS will handle it properly and won’t let you down.

How easily you can generate part files for your CNC machine depends on the type of CAD file you start with. When your sheet metal fabrication line uses powerful CAD/CAM software with many import features such as SMP/IS, importing files is quick and precise leading to fewer problems with parts down the road.