Designed machine in 3D, how best get 2D fab drawings of each part?

[dbg]

I've designed a machine in 3D, and now I need to fabricate it. The components are intended to be cut from plexiglas with a laser cutter, so I need to get each component drawn in 2D now, and eventually into Windows Corel Draw, which controls the machine.

What's the process an experienced user would use for this task?

Just copying and pasting into new sheets seems rather error prone as well as tedious.

[Pat Stanford]

This explanation will assume that you can see each part separately, and that the parts do not align perfectly to the standard (Front, Back, Left, Right, Top, Bottom) view planes. If they do align, then it is even easier.

1. Use the Set Working Plane tool to set the working plane to the face of one of your components.

2. Click the Look at Working Plane button in the Working Planes palette.

3. Use the Extract tool in the Extract Surface mode to click on the face. Use the Next/Previous arrows in the dialog to select the correct face. Click OK. Click the Green Check Mark to extract the surface.

4. Select Convert to Polygon from the Modify Menu. Select the Wireframe option as you should only have one surface selected.

5. You now have a 2D polygon that exactly matches the 3D surface. You can copy and paste this to a different layer or a different drawing.

6. Rotate the view so you can see a different component.

7. Repeat steps 1 to 6 for each additional component in the drawing.

The critical steps are setting the working plane and then looking at the working plane. This way you get a true pattern.

It might help to temporarily set each component to a different color to make it easier to see and ensure that you have selected the right one before extractng the surface.

Pat

[Benson Shaw]

Some of your components may be extrudes or other memory bearing objects. No need to reorient the working plane for these types of objects, no matter their 3d orientation. Double click such an object to reveal the underlying polygon.

Once you have the polys, you need to export them from VW in a file format and version which can be read in Corel Draw. I am guessing dwg or dxf will be your choices. Possibly the pdf, post script or eps formats will work, too.

If you have CDraw, do a trial VW export and import to CDraw tocheck the geometry and scale. If you do not have CDraw, reimport the file into a new VW file. This way you can check that the geometry and scale exported properly. Sometimes they do not, and the VW poly needs to be corrected (stacked points is often the culprit. Then send a single test file to the cutter, try to be there when the file is opened (this is like a press check) and examine it with the CAD person for continuity (no gaps), scale, and geometry. Once you have the export/import process working, make the rest of the files.

Other potential pitfalls:

1. Some cutters' software cannot read the exported polys made with VW spline or bezier vertices. They read arc and corner points only. Ask your cutter, or send a trial.

2. Some machines slow down when cutting files with lots of points. This costs you more. Try to draw with fewer. CDraw used to have a filter to even out the number of vertices. New versions probably do, too. But using the filter may change curve shapes slightly and affect your fit up.

3. As mentioned above, VW poly export sometimes creates extra vertices. Zoom in and look, especially at corner points - drag it and delete if it is stacked, or undo if not stacked. Delete extra points on straight segments.

Good luck!!

-B

[Charlie_P]

Further to the above...

We do this all the time both internally (exporting to a plasma cutter for steel profiles) and externally (laser cutters for steel & plastics or flame cutters for serious steel), so it's a familiar process.

Some repetition but bear with me...

1. extract the 2d polys either Pat's or Benson's way. Be aware that both have pitfalls; Pat's way tends to give more vertices which can generate less than perfect cuts and Benson's of course only works with polys that have been extruded - if any solids operations have been done on the part (holes added, bits trimmed off etc.) then it won't work.

2. I always try to export from a fresh VW file to avoid calamities. Copy and paste the polys over from the drawing file and save it as plexiglass profiles or some such so you can have several bites at exporting without having to worry if the file has changed in the meantime. Centre the profiles around the origin so the other chap can find them easily. When we are doing this for our own cutter I'll nest the profiles at this point as it's easier in VW than other programs. If it's going to a cutting service give them a little room between bits. Do a sheet layer showing the profiles as exported with a few salient dimensions and export as PDF and email to the cutting service with the DXF. This avoids costly mistakes (I leant the hard way)

3. Export as DXF. Talk to the cutting service if you like but the best bet is an old version (I tend to use 12 or 13) and text rather than binary - but this is not hard and fast. You don't say which operating system you are using; if it's a Mac then make sure you decheck "hide extension" from the save dialog.

4. Send or take the files to the service and get them to actively confirm the dimensions (rather than "Yeah, OK it imported"). Stay on the phone or look over their shoulder as they add cut paths (the cutter instructions based on your drawing); it's at this point that open loops or double vertices show up (open loops are unclosed polys)

5. Keep your fingers crossed.

In general things are OK but it helps to draw with profiling machines in mind; draw polys fully formed in 2d then extrude to 3d (no solids modeling) so you can use Benson's extraction method. Avoid ellipses as most cutters break these down into short lines and make a mess of them. Make sure your polys are closed - I use the paintpot poly creator a lot as a check. Check your vertices; if you've used add/intersect/combine into surface a lot this can leave residual useless vertices that would be better deleted. Above all never forget the dimensioned PDF. Inscribe that rule on a vital and often used part of your anatomy.

All the best,

Charlie

[dbg]

Thanks for the help!

All of these sound like one-time snapshot kind of operations, right? I.e., if I later have to make a change, I have to re-extract the surface and replace it in my 2D sheets, right?

I was hoping there'd be a way to do it where the 2D cut plans would automatically update with revisions in the 3D model.

I guess maybe one could do that by designing 2D/3D symbols for each component, so that the symbol would be the thing one revised. Not practical, I guess... and anyway I didn't do it that way.

BTW I just got a Mac Pro 2x4, running OS X.5.1 Server. VW 12.5.3 seems to work (after many days of re-installs, not sure what finally fixed it. Probably some kind of permissions problem combined with old bits not getting deleted. Would launch exactly once after each reinstall.)

Dave

[Benson Shaw]

Can workgroup referencing do this? Maybe with some script to search for each element and extract the edge poly to the cutting file?

Just remembered another tip. One cutting service I work with checks the dxf lines for continuity by performing an offset. A very small radius setting of the offset will work fine for a good poly, but will go wonky if there are gaps or stacks. Or so he says. He uses ACAD Light for this.

Let us know how the cut and assembly goes.

-B

[islandmon]

As a side note ... in the olde days of pen plotters the Houston & CalComp software did all the 2d line & arc segment conversions in order to allow the plotter pens to describe the shapes efficiently via the pens. This is still the way it is done with Vinyl Sign Cutters.

Looking into the resulting Plotter Print file ( which was not postscript but ANSI / ASCI ) would show where the algorithm had fine tuned the vectors for the most efficient XY transits & trajectories.

Of course, when it came to printing Text the plotter either utilized the installed Font Vectors or defaulted to time consuming bitmaps.