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Kurt Magness

export to rapid prototype modeling

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anybody familar with exporting vwks files to rapid prototype modeling companies? when I export as .stl file my modeler sees rectangular doors & windows as triangles. Seems only 1/2 the Ds& WDws com thuoght. any suggestions? also iges and sat does not work well either. is there a cad translator program that works with vwks?

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Kurt,

I wouldn't try it.

I have numerous problems everyday trying to export to our CNC toolpath programs and it does not work. I have tried all variations of export and always with the same results. We have found that if we use Rhino as a filter we can import in and export out a usable file. The way VW exports its files is not liked by machining programs, at least in our experience with our programs. We would never use a VW file unless it was just a very simple part. Curves, arcs, fillets etc do not translate well at all.

Hope this helps,

tom in pa

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Kurt,

It very much depends on the process you are using. For outputing layer based rapid prototyping systems (stereolithography, Fused deposition modelling, Laser sintering, and loads of others!) the file format every bureau prefers is STL.

STL is a triangular based polygonal mesh format. What I suspect you are seeing is a resolution issue. When you export STL you get a slider for more or less polygons - slide it along to the right a bit and also try choosing Binary.

This generally works OK.

In any case (and this is a strong recommendation!) get hold of a common STL viewer and check the output in that. Sometimes you need to adjust the settings to get the triangulation right.

I recommend Materialise Next Day software. This is free and lets you open STL files and check their quality before sending off to the bureau. This software is based on the common Magics RP software used by a lot of bureaus. So if its OK in this it should be OK for any bureau.

Download from www.materialise.com and follow links to Next Day.

This site has loads of information on RP as well.

In the tests I have run using VW 11.5 for walls with windows and doors all the elements do export, but often there are numerous errors (bad triangles and contours) in the STL file. The resolution is fine though. Most of these errors are minor and easily fixed by Bureaus using their software (Magics does this really well).

Where the geometry is more product like and solids the STLS are generally OK.

What I suggest doing for architectural modelling is to not use plug in objects for doors and windows, but to pierce the walls the "old way". In fact don't use walls either when you are closing it off as there seems to be a common face error in most files where the start and end point meet to close off the wall plan.

What I tell all my trainees is decide at the start what the outcome needs to be. If it is drawings and visuals then any tool will do. If it is 3D output or CAM then choose carefully and build more methodically.

As for exporting to 3D CAM systems, ACIS (.sat) is the most robust as this is the modelling kernel the software is built on.

For 2D CAM profiling (laser cutting, routing etc), dxf or dwg work fine.

There is no perfect system out there. Even the mega bucks systems like CATIA and UG have problems moving from design to production (CAM) on some parts. Understand the production process and you will be in a far better position to deal with the problems as they happen.

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Kurt, you have got my curiosity up. If I may ask, what are you doing, or trying to do, with rapid prototype modeling?

[ 07-11-2005, 06:04 PM: Message edited by: Kevin ]

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KQ: thanks for the info. Unfortunately I'm on a Mac so "Magic" will not work for me. I will tell one of my RPM guys about it and maybe he can use it to fix the meshes. I guess I will google around the web to see if there is a Mac stl viewer / fixer. Yes for general 2d laser cutting the guys I use can use the dxf export. And that works OK. Some scaling problems but I just give them the actual size of the object I need. One guy prefers corel draw though. seems everybody is a little different on what they like. For the RPM 3d stuff stl seems to be the prefered file format for sure. Some guys have more software than others and the export settings seem to make a difference. Solidworks seems to popular. I have had better luck with the ASCll than binary though. One guy calls stl "many little triangles", which is what it does I guess. Converts everything to a bunch of little trianglular meshes. Seems some RPM guys know more than others on file translations. I have use 3 different RPM companies. i am modeling very complex buildings (multi story school buildings 200' x 100' x 60' ) with a small output @ 40th scale ( 6" x 4" x 2"). The most expense guy has the software to fix anything and can model using a "laser/ liquid" process. He actually likes form z for modeling. he provides great smooth output. The least expense guy uses the "inkjet type /layering " process and has problems with my stl exports. the laser process is way cleaner and more higher rez so you you see no laying. All surfaces are very smooth and no post modeling sanding is required. I guess you get what you pay for but it would be nice to see what they are getting and be able to fix them. I haven't had problems using the plug ins for door and windows, or the wall tool either. I have been using the "cased opening" option for doors and windows since it just leaves a hole in the wall which is what the machine does. You also have to be aware of the wall or part thickness at the scale of the output, since the material can get too thin. I have been using 2 to 3 ft thick walls for models that endup at say 40th scale. Hear too I have to specify what my final output size will be because the export carrys no scale info. Maybe a nemck moderator will chirp in on some hints. I am not sure if all stl exporters are equal. Keven: I am making architectural models, RPM for the buildings, laser cutting sheet styrene for flat site work, site topo using a 3d foam router.

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Ok so I found a free stl viewer at http://www.ripplon.com/products.html it's a classic app but it works. No fixing anything but at least I can view stl files for review. And I figured out what was happening. Seems it was my fault of course. Or actually my draftsperson. All the doors & windows in the model were done using a the door plugin, cased opening option, but to create a window my dp raised the door up in the wall so that the bottom of the door was above the floor line. This rendered ok in vwks but when stl exported, They came in as a triangle, 1/2 the opening. I guess because the bottom of the door symbol was up in the wall vwks could not resolve the opening correctly. duh

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ok so there is more weirdness than I thought. walls work ok. if you create a door or window with the plug in it works sometimes, sometimes not. If you turn it into a symbol it works better. I have had to get a door that works, check it out with the stl viewer, then duplicate it and change the parameters to insure it works ok. They all look ok in vwks but when you export it to stl and check it out with the viewer some do not show up at all or they show up as triangles, half of the opening. any clues nemchk ?

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