Re: 3D machining

>Message: 9
> Date: Tue, 08 May 2001 22:31:30 -0600
> From: Doug Fortune <pentam@...>
>Subject: 3D machining
>
>Ian Wright wrote:
>
>> Can someone who is familiar with 3D machining on a cnc machine please
>tell
>> me what form the DXF file should take. I need to draw up some parts for a
>> project which I hope to be able to make on my little mill when it gets
>> finished but I can't decide whether I need to draw them as Autocad
>'Solids'
>> or as 'extruded planes'.
>
>I'd model it as as a solid, then export it as a 'sufficiently high'
>resolution
>STL (Surface Triangulated Language - or - STereo Lithography ) because
>several affordable (I'm not going to say 'low end') packages can take that
>format. In particular, Millwizard ($250), Deskproto ($1500), Fred Smiths
>STLWork ($ ?).
>
>The problem with STL is that you still have tiny triangular planes,

When memory was $100 per meg STL was a more expensive format to use than IGES. Now that it costs about $1 per meg, the tables have been turned. The difference between the two formats is somewhat like the difference between analog & digital, with STL representing the digital method. An stl file looks like a closed surface (a solid), comprised of small adjacent triangles at various angles. It can be represented in either an ascii or binary format. Autocad has a similar entity format in the DXF files called a 3D face. This is the entity generated by software in small 3D scanner programs like the Picza scanner.

StlWork is still $250. That price will increase with the release of StlWork 2, in about a month. It will include waterline machining which is much less stressful to small machines with underpowered Z axes, while still maintaining planar cutting patterns. Since so many machines have or are getting continuous contouring now, it will take advantage of this feature. We should also have a technique to use the Vector rotary 4th axis to make a spiral cut about the centerline(any theoretically convenient rotation axis), combining the capabilities of both programs. No gouging and planar cutting strategy. There will be a free upgrade policy for the first month or so for prior StlWork customers.

There are several other 3D formats that can be translated to Stl using the StlTrans program that is included with StlWork. These are primarily formats developed for 3D animation and web based formats like VRML.

http://www.stlwork.com

The nature of the work still should determine the file format to use. If you are making flat, edged parts, as opposed to surfaces, stick to DFX wireframes and forget the fancy 3D crap. Draw the top view and machine it. Why waste time with pretty pictures when you can be making chips instead? ;-)

Best Regards,

Fred Smith
IMService

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