jon_banquer wrote:

On Wednesday, December 18, 2013 5:20:57 AM UTC-8, jim wrote:
Bob La Londe wrote:





What affects surface accuracy is of course the resolution of the surface

mesh (STL or 3DS) and the defined resolution of the machining operation.



That is not all that affects accuracy. Even if you have the time

and computational power and storage capacity to produce g-code

files with millions of data points there is still the question of

whether your CNN can fluidly move to all those data points and cut

the part to within .0001".



If you had a machine that could do that

it is unlikely you would be using CamBam.



If you are making fishing lures and the end product

conforms to the original CAD surface geometry to less than

0.002" then you are doing exceptionally good job.



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There are some CADCAM programs that can produce toolpath directly from a surface model and don't triangulate the surfaces in order to produce toolpath.

This one mentioned in this discussion has a reputation for producing very high quality surface finishes that don't need any polishing:

http://lnkd.in/baa9swf

The issue with producing toolpaths from meshes is not entirely
about accuracy. 3d surface cutting usually requires a ton of point
to point tool moves to cut the part. Ideally, at the micro level each
pass of the tool across the surface should be parallel to the last
pass such that the tool is constantly removing about the same amount
of material. To do this with point to point moves, each point to point
move in one pass should line up with the point to point moves of the
previous and next pass. Creating tool moves from well constructed meshes
is a way of making sure the point to point moves in each pass match
up to the moves in neighboring passes.

In most cases when the CAM software people tell you that they
create toolpaths from surface data what they mean is that an
ideal mesh is created that is aligned with the projected motion
of the tool across the surface. If you set the toolpath tolerance
parameters loose enough you will still be able to see in the
surface finish the underlying mesh pattern.

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