We have a table designed in SW and export the file as dxf into Corel draw. In Corel we ungroup the nested parts in the sheet and make sure everything is hairline width. Yet the laser wants to run over certain sections 3 or 4 times as if it sees lines on top of lines. How to ensure that all lines are in fact a single hariline?
Does your exported DXF have any overlapping paths?
If several paths are in exactly the same location they may appear to be a single line onscreen. But the lasercutter is faithful to the instructions it receives so will cut each one regardless.
As far as I know overlapping paths have to be manually removed until there's only a single path for each cut. (It would be cool to know if there are any tools to do this automatically!)
If you like I could have a look at the file to see if this is the problem - just attach it here.
Its quite likely your dxf export is exporting all the polylines that compose the outline of your shapes in 3d. - leading to the 'reverse sides' of objects and the 'bottoms' of holes being exported as paths.
Most vector editors can join paths and remove doubled points, but at least in inkscape, which i use, this is a very tedious point-by-point job.
My first approach would be to use a 3d app for this (personally, i use blender http://www.blender.org). - i would join any separate objects into a single one, select all points and scale them to zero on the axis perpendicular to projection (so every point is on the same flat plane) and use the 'remove doubles' tool.
I'm not sure if solidworks has an option to do this - there may be a 'omit back faces' option which may reduce the amount of manual point-merging you need to do in your 2D vector program.
I have never had Solidworks give me the problem of doubled up lines if I have exported the DXF from a drawing. I have had the problem if what I exported was not an elevation but rather a 3D view of some kind or maybe if it was an elevation of an assembly not a single part. I have heard of Auto CAD giving trouble with doubled lines.
Usually you can get an eye for doubled up lines as they appear darker or more intense in color if you have zoomed out to view the whole page.
I don't know of any tools in the software to remove doubled lines, I normally just delete the ones I suspect are doubles. If it turns out they are not doubles I always have the ctrl-z option to undo the delete