Common DXF Conversion Problems (and How to Avoid Them)

Updated Dec 8, 2019
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Convert PNG to DXF When it comes to DXF conversion, you want it to be as quick and painless as possible. After all, the CAD/CNC file you require should only be a few mouse clicks away. In most cases, just following our quick guide to converting an image to DXF should get the job done. Sometimes, though, you may run into a few problems. To help you tackle them, we’ve put together this list of some of the most common mistakes made during the conversion process – and what you can do to avoid them.

“I’ve lost the scale information after converting my file to DXF”

The first thing to consider is which type of file you converted to DXF. One of the most common uses of Scan2CAD is conversion from PDF to DXF. As PDFs can be opened universally, images saved under proprietary CAD file types are often converted to PDF before going on to be converted to DXF. The trouble with this approach is that PDFs only store print dimensions, and discard the scaling information from CAD software. PDFs only preserve the relationship between objects (e.g. point A is 20 pixels away from point B). This problem is compounded by the fact that DXFs don’t define physical dimensions using measurements like millimetres or inches.

Save DXF File with Scale

Define the scale of a DXF file with Scan2CAD

To solve this issue, you’ll have to set the scale again after DXF conversion. Scan2CAD offers three different ways to add scale to your DXF image: DPI, distance or geo scaling. Check out this article in our User Manual for detailed instructions on changing the scale on a vector image.

If you’re converting a PDF file into DXF, you may also lose hatching information. This is because PDF files stores the hatch as a pattern fill, a feature which isn’t supported by DXF. This is also easy to fix post-conversion – just map the resulting value into a hatch entity.

“I want to convert from JPG to DXF”

Image Conversion - Pixelated raster to vector

It’s difficult to extract a clean vector from a pixelated image

Although JPG is one of the most popular image file formats around, it’s not always ideal for conversion to vector formats such as DXF. JPG is a compressed file format, which means that some information is discarded in the interest of saving file space. The downside, however, is that JPG images are usually very distorted when zoomed in. This is an even greater problem for images which could be 2 color (black and white) for example, line drawings for part schematics, or architectural floor plans. This is because JPGs don’t save these drawings in black and white, but as grayscale images, with blocks of pixels in varying shades of gray. Conversion software is unable to group together these pixels, and thus distinguishes the black parts and gray parts as separate vector entities.

We always recommend using a high quality image format like the TIFF file format if possible, which is the standard file format used to exchange raster images between programs. TIFF, or Tagged Image File Format, is commonly used among graphic artists and photographers, as well as in the printing and publishing industry. PNG and GIF formats are also acceptable for images with few colors—to learn more about GIF to DXF conversion click here.

Struggling with converting your JPEG file? Don’t despair—check out our ultimate guides to converting JPEG to DWG and JPEG to DXF to help tackle your vectorization issues!

“I can’t import my DXF file”

Not every DXF file is the same. Every third version of AutoCAD comes with a new version of the DXF file format. Think of it like MS Office – you couldn’t open a Word 2016 file in Word 97. CAD software is much the same – whilst backward compatibility comes as standard, an older version of your software won’t necessarily be compatible with more recent versions of DXF. This issue is especially common when transferring files to a milling machine. It’s good practice to save the file in AutoCAD 2000/DXF format, as this avoids compatibility issues. You can use Scan2CAD to convert between versions of DXF, with support for all versions back to DXF 2000.

When converting a DXF file to an older version, the conversion program either strips out information that is specific to the current version or converts it to another object type. Always remember that converting a drawing to an earlier release format may cause some data loss. To avoid overwriting the original file and losing this data altogether, remember to save the file using a different file name.

“I’ll design my drawing in one CAD program and export it to another using DXF format”

Often, a designer will forget to check the requirements of the output CAD program. This is a common problem if your converted DXF file is meant for manufacturing. DXF files support hundreds of entity types such as hatches, blocks, tapered polylines, TrueType fonts, multi-line text, splines, regions – and many, many more. All of these are very fancy entity types. (For more info, check out our overview of the DXF file format.) In contrast, simple manufacturing formats only contain X-Y coordinates and shapes. It’s therefore very important to make sure that your DXF file contains the necessary information for its intended use.

“It doesn’t matter which file converter I use, they’ll all give me a usable DXF file”

Not all file converters are created equal. It’s tempting to go for an online converter – after all, it’s free, and there’s no need to download any software. Unfortunately, the output is unlikely to be good enough for use in CAD. Often, dashed lines, arcs, and curves will be converted into a series of short straight lines instead of the appropriate line type.

S Shape represented by Raster Image, Vector Lines and Polybezier - Scan2CAD

There’s a right way to convert to vector – and a wrong way.

Not only is the choice of converter important, but choosing the right image is key too. You know what they say – “garbage in, garbage out” – and it’s especially true when it comes to file conversion. Make sure to clean up your image before conversion – a few quick retouches can work wonders, and give you vastly improved results. Want to know more about getting rid of speckles, getting crisp lines, and fixing that annoying skew? Head over to our Ultimate Guide to PNG-to-DXF Conversion for all this – and more!

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