Secret to Eliminating Open Boundaries when converting DXF to Gerber.
25 October, 2016
I'll give you the answer, before I explain: Join Interactive
Probably the most frustrating experience for anyone who has attempted to convert a DXF file to Gerber, is the dreaded "boundaries are open in the Gerber Viewer and won't fill". If the boundaries won't fill, then those converted Gerber files are useless and cannot be sent out to manufacturing.
Why does this Gerber Fill Problem happen?
Gerber files have stringent fill rules and requires the following:
- All boundaries must be closed & continuous.
- No overlapping or self-intersections (like a bow-tie).
DXF files are typically constructed as outlined boundaries and have no fill requirements. When the above Gerber fill rules are violated in DXF, we call them Boundary Errors.
2D CAD Software Unknowingly Facilitates these Boundary Errors.
2D CAD software (like AutoCAD and Draftsight) typically display the entire DXF drawing as outlines & wire-frames only. It's visually very easy to mistakenly include overlapping lines/arcs, and leave unconnected vertices when exporting to DXF. In fact, 4 out of 5 DXF files generated for conversion to Gerber will typically have some type of boundary error.
To remedy these boundary errors, AutoCAD has command called: PEDIT along with the Join option can be used to ensure constructed boundaries are continuous. However this command can be cumbersome, slow, and there is really no way to check if all Boundary errors have been eliminated.
Use Automatic Join and Fill - During DXF to Gerber Conversion
Any competent DXF to Gerber conversion software must have the ability to automatically join and fix boundary errors during import. Both ACE 3000 and FAB 3000 have exceptional Join algorithms to ensure all boundary errors are eliminated.
What happens when a DXF boundary is constructed so poorly, that Automatic Join still does not remedy the Boundary Error?
Use the command: Join Interactive. Join Interactive was built for the worst case boundary errors, and to prevents having to "re-design" the DXF. To use it simply select one object one the open boundary. Join Interactive will attempt to close the boundary; however if there are any ambiguities it will stop and prompt for your input.
Using Join Interactive will eliminate the frustration when having to perform DXF to Gerber conversion on poorly constructed boundaries that won't fill. Here's a tutorial movie showing how to use "Join Interactive" in FAB 3000 to eliminate open boundaries (sorry no sound on this movie).
Note: DWG files are the binary representation of DXF, and have the exact same problems.
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