How to preflight DXF files for CNC

[cnckeith]

How to preflight DXF files for CNC, great web page covering most of what you need to know.

https://sendcutsend.com/blog/how-to-pre ... sing-qcad/

[cnckeith]

Common DXF and SVG pitfalls are:
- Duplicate Lines and Arcs. These are lines and arcs that are identical and drawn on top of each other.
They do not show up when looking at the cad file in a cad system but if they are there Plasma Intercon
will see them and try and use them. Solution: Most all CAD systems have a “Delete Duplicate”
function which cleans up the cad drawing by deleting any duplicate entities (lines and arcs).
- Extra, unused random points in space
- Endpoint over-run or gaps: Lines or Arcs don’t end at the same start point of the next line. This could
be a gap or over-run. Solution: Most CAD systems and drawing program have tools to automatically
join line and arcs endpoints so they start and end on the same point. Clean up the CAD file in this way
before importing into Plasma Intercon for the best results. Plasma Intercon has a Vector gap tolerence
setting as well. Plasma Intercon will automaticlly join vector endpoints that are within this distance
tolerence setting.
- Hidden Lines and arcs. Lines and Arcs that may not show up in the CAD program may be because of
color or a line thickness of zero. Will show up in Plasma Intercon. Solution: Make all lines and arcs the
same color and thickness.
- Hidden layers, multiple layers. Sometimes hidden layers or multiple layers will cause an issue. Put
all geometry (lines and arcs) on one Layer and delete all other layers.
- Fonts don’t work. When creating text in the CAD system most systems will use any of the Windows
installed fonts so you can easily size and place the text you want. Solution: The last step before saving
the CAD file in preparation for importation into Plasma Intercon is to convert all text into lines and arcs
in the CAD system. Typically in the CAD system there is a feature called “Convert (fonts) to Outlines”
or in Qcad is called “Explode”
- To many nodes. A common problem with art related SVG’s and DXF’s is the vectors that make up
the art are very very short vectors (for example .001” long lines) sometimes there are thousands and
thousands of ‘nodes’ (aka endpoints) this is commonly a result of scanning and using CAD tools to
convert a photo (bitmap image .bmp, .jpg, .png, etc) to vectors. Centroid CNC12 is very good at
running a short vector plasma part program at smooth speeds when using its “Smoothing”
feature. That being said it is always good practice to not have super short vectors especially when it is not necessary. There are
diminishing returns involved, having super short vectors is unnecessary and at some point will start to
degrade the cut performance. When tracing a bitmap with software tools don’t just crank up the resolution as that will create a file with very
short vectors. Only increase the tracing resolution settings to the point that a satisfactory trace is
made. If you are working with a tracing DXF/SVG file created by someone else and you are not the
one tracing it you can still optimize it as most CAD systems and Art programs (inkscape and illustrator)
have optimization tools that will reduce the number of lines and arcs that make up the file by fitting
longer lines and acrs through all the short vectors that closely matches the geometry.
- Drawing is using fill or width parameters. CAD file looks fine in the CAD/Graphics program but looks
complexly different in Plasma Intercon. Commonly found in graphics programs are fill and vector width
values that are used to define a shape. Solution: Use the tools in the CAD/Graphics program to
export/save as only vectors. In illustrator use “Convert to Outlines” to convert shapes to lines and
arcs.