Tips on making good drawings

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The better your drawing, the better your part will be. Following are some tips on creating good drawings that will minimize the chance for mistakes.

  • Draw your part to scale
    When drawing your part in your CAD program, use a scale of 1:1, or else when the part is made, it may be off by whatever odd scale you drew it in. It is easy for the jobshop to rescale the part, but they need to know ahead of time that this is needed. This might not be caught until after your part is made; therefore, just draw it to 1:1 scale to start with.
     
  • Keep your drawings clean
    Remember, your CAD drawing will be turned into a tool path eventually. If you have lines on top of lines, or other stray entities in your drawing, it will make it difficult for the programmer to turn it into a tool path, especially if their CAD / CAM system does not have good automatic “cleaning” functionality.
     
  • Make sure your drawing matches your dimensions
    If you draw a circle that is 5.3″ (13.4 cm), but then put a dimension on it that says it is 5.0″ (12.7 cm), it will probably still be cut at 5.3″ (13.4 cm). Therefore, draw it the size you want it, so it gets cut that way.
     
  • Include only the part you want made in the file
    In the file you supply to your vendor, include only the stuff that you want cut to avoid confusion. Don’t include related parts, or information about drawing revisions. Every line in the file should belong to the part.
     
  • Ask your vendor what kind of file they prefer to get
    Your vendor may prefer files from a particular drawing program or in a particular format. There are a lot of different CAD programs available and chances are that your vendor is experienced with only a few. Work with them to figure out what their preferred format is.

If you are using CorelDraw or Adobe Illustrator, then you may need to go through additional file conversions to deal with curves. These programs will typically convert all curves to many short line segments when creating DXF files. This can result in your final part having curves that are faceted (although typically each facet is very very tiny).

There are a few ways to deal with this situation. The first is to just do nothing, and live with the faceted faces if this is low precision artwork. Another suggestion is to save as an Adobe Illustrator AI file, and then use a third party convertor such as Bezarc from Kandu Software to convert the file into a much better DXF than CorelDraw makes. Some vendors may also have the option of a “smooth” command to help automate the task of converting the lines back into curves (OMAX Layout software has such a command).