Re: Re: How to go from 2.5 D to real 3 D ??

Message: 21

> Date: Thu, 22 Nov 2001 06:06:34 +0000
> From: Jon Elson <elson@...>
>Subject: Re: How to go from 2.5 D to real 3 D ??
>
>tom.kay@... wrote:
>

>> I think I get the concept about what's 2.5 D and what's 3D. In 2.5 D,
>> you do some x-y movements, then stop, lift the tool in the z axis,
>> then stop, and do more x-y cutting. In 3D, all three axes can move at
>> once. Or 4, if you have a rotary device.

Tom this is very close to the concept. However think also of the tools that are used. In 2 1/2 D the tools generally have square corners, like an End Mill or are used in only one direction, like a drill. 3D is usually thought of as using either V-tipped cutters or Ball End Mills. Historically the 2 1/2 axis machines replaced 2 axis machines that could only control 2 axes at once and the Z was hand operated (Bridgeport and SW industries still sell a 2 axis machine controllers). These are VERY productive and cost effective, compared to manual. The 2 1/2 axis machine adds a 3rd axis of control, the Z. Since this is the usual case today that all 3 axes have full control, the distinction between 2 1/2 and 3 axis control has become quite blurred. In fact it is usually found in the Cad-Cam program and not the machine as the machine is responsive to either kind of commands. Corel draw is strictly a 2D system. Someone corrected me the other day by reminding me that Corel draw (I think 7) included Corel 3D. While that is true, it is not included with the latest versions. So Corel is a 2D system. It can NOT generate any Z. You can utilize additional programs to make Z moves, like Ace does.

The predominant application of 3 axis machining is for surfacing molds and prototype parts, probably followed next by 3D sign making. The basis of 3D machining is the ability to make 3 axis simultaneous moves and it is absolutely not in any way related to whether or not the machine is cutting arcs or lines. Most 3D surfacing is done with huge files consisting of point to point moves that have been compensated for the desired surface and the geometry of the tool that will be used.

>Designing 3-D solids and then machining them on a 4-axis system
>is not doable on any of the very low-cost systems like Bobcad/CAM.
>
>Jon

Not useful in Bobcad, but there is a lot more world than just Bobcad. Vector can easily generate rotary 4th axis code from any 3D wireframe drawings. The code can be oriented about any of the 3 axes as a rotary, and it can work with StlWork to produce rotary code for the surface from STL models of a 3D solid.

On our StlWork page is a list of low cost 3D solid modeling cad programs that are available on the internet(available from Free to $1000).

http://www.stlwork.com

In addition there is a "FREE" program called ProDesktop that is being made available by PTC the company that produces ProEngineer. ProD is a first class solid modeler. Combining this with StlWork will get you going in 3D in about 4 hours.

http://www.prodesktop.net

Hope this clears up a little misunderstanding about where 3D is today.

Best Regards, Fred Smith- IMService
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