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Bas Vellekoop

VW > DWG/DXF > CNC-milling / waterjet cutting, getting the correct curve- and linetype

Question

For the production (CNC-milling and waterjet cutting) of several parts I need DWG and DFX-files
I have a problem with the exported lines.
The exported lines from VW should be (to work properly with the different machines)  'polylines', but sometimes they are 'splines' (see image underneath and the difference between how the curves are drawn).

If I convert the splines in Autocad to polylines they get hundreds of extra control points and the different milling/cutting machines aren't able to use those (and the line gets faceted).

My workflow:

- Draw the model in 3D
- extract planar object
- change the objects to screen plane
- export the selected object to DWG or DFX version 2010 or earlier

The odd things is that from different object, but the same file, I get different types of lines in Autocad.

Anybody experience with this? Anybody knows how I can export them so i get clean polylines?

Attached the different files, if anybody could have a look i would be very happy! :) 

(ps I`m not able to attach VW-2017 files on the forum :( )

DWG.jpg

DWG 2.jpg

export test.dwg

export test v2016.vwx

Edited by Bas Vellekoop

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I did some further investigation for solutions, but not really happy with the outcome:

First possibility:

For a polyline to export and import as an polyline in Autocad the line should be build up out of:

- separate arcs and lines that er composed in a polyline
- a polyline that only uses the corner vertex mode and point arc mode

But this means I have to completely redraw my extracted polylines, and  that's a waste of time to be honest.

Second possibility:

Extracted planar object exported as DWG and imported in Autocad  sometimes become polylines (good!), but can become splines (bad!)as well.
Why te difference is unclear to me.

To make sure the polylines in VW are polylines in Autocad I convert them with 'poly smoothing'.
At first sight I thought this worked very well.
But having a closer look showed that radius of curves are changed from bigger to smaller (from 5mm to 3mm)
I'm under the impression this is a to big of a difference to not be seen as a bug.

@JimWcan you have look at the files, and do you know why one polyline exports as an polyline and the other as an spline? And the relative big difference of the radius when converting lines with poly smoothing, should that be considered a bug?

test.jpg

test convert to correct polyline v2016 but drawn in 2017.vwx

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Anything that is or contains a smooth polyline, nurbs or bezier curve will convert as a spline when exported to dwg. The same may happen to some 3D polylines if they are not planar depending on a few variables.

There is a tool to fix such problems for CNC use , and I think it included fixing dxf files, but I'll have to look it up at a later time, as it was on another forum for a different piece of software.

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I've found the fix for DXF output, but it is a plug-in for CorelDRAW and not a standalone product. For those having CorelDRAW and interested in it, the links are below (there is a 32-bit version too)

http://macromonster.com/product/james-leonards-standard-dxftool-64-bit-only/

http://macromonster.com/product/james-leonards-pro-dxftool-64-bit-version/

 

Alternatively you could take a look at this:

https://sourceforge.net/projects/dxf2gcode/

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