"Lloyd E. Sponenburgh" lloydspinsidemindspring.com wrote in message
. 3.70...
jon_banquer fired this volley in
:
Note the request by another commenter for a 3D surfacing video.
I'm still waiting for Mark Wieber, or any of his clique of idiots, to
discuss machining parts that need surfacing. I've seen no evidence
whatsoever that a liar like Mark Wieber, or any member of his clique
of idiots, has ever created surfacing toolpath. I have also seen no
evidence that these losers can machining anything other than simple
prismatic parts.
There is a lot more to CNC machining than just doing prismatic parts
and converting an old knee mills to Linux CNC.
Show us an example of what you call "3D surfacing".
Even the low-priced UK CamBam (primarily targeted to hobbiests) can do 3D
surfaces, roughing to approximate shape with flat end mills, and then, if
you have the time, pretty good surfacing at small stepovers and small
depth increments, using ball and bull-nosed cutters.
So, I'm not sure what you mean when you say most CAMs can't do it, unless
I don't understand what sort of 'surfacing' you're referring to.
Lloyd
I do a fair amount of 3D with CamBam, but to be fair anything I can do with
2D (2.5D) I do. For me its about the price. I tried a lot of different
free and low price CAM software, and CamBam was the only one I could afford
that does do 3D ok.
It's a one man show so forget arguments based on the documentation. The
documentation is way behind what it can currently do. I would rather Andy
work on bug fixes and new features than spend all his time writing doc
files. That being said, my opinion was reversed when I started learning how
to use it a few versions ago. I was frustrated by the lack of detailed
documentation in some respects.
Somebody was talking about surface accuracy of a tenth. As near as I can
tell the limitation here is the processing power. CamBam does 3D machining
of a surface in two different manners, and that's pretty much it.
1: Waterline - It does waterline at a depth increment either as a finish
(0-X roughing clearance) where it cuts the contour lines of the part only,
or it does waterline roughing with (0-X roughing clearance) where it removes
all material in the defined area to finishing that depth increment at the
contour line. For some reason the waterline method seems to leave material
I would not expect sometimes.
2: Vertical or Horizontal (scan line method) This traces the surface
either with horizontal or vertical passes, and it can be by depth increment
or no depth increment. No depth increment is nice for a finishing pass as
it will trace the surface exactly (within the set resolution) on each pass.
Using this method with boundary shapes, defined cut areas, or a cut limit
based on the surface itself is modestly powerful.
There are some tricks also... For instance you can rotate the surface (and
other associated geometry if needed), and then rotate the MOP back to the
original position to get diagonal scan lines. The transformation matrix is
pretty powerful in that respect, but there are things it gets confused at.
Fortunately they are things that confuse me to so we agree not to do those.
LOL.
What affects surface accuracy is of course the resolution of the surface
mesh (STL or 3DS) and the defined resolution of the machining operation. In
a 3D machining operation it calculates the depth of Z based on a percentage
of cutter diameter along the scan line. For example with a .0625 diameter
cutter and a machine operation resolution of .01 it will recalculate the
depth of Z every .000625 inches. With a large operation that can be quite
time consuming to calculate tool paths. The higher the resolution the
longer it takes to calculate the tool paths, but the cut time is based on
the run mode of the machine, and the acceleration rate. Sometimes I
generate tool paths that take 45 minutes to an hour just to calculate them
on my little dual core processor CAD/CAM computer. As of the last time I
checked CamBam can actively use 2 worker threads for a MOP, but that's it.
(I seem to think it might only use one worker thread per MOP.) More
processors helps to calculate multiple MOPs at a time, but doesn't help
speed up a single MOP. It can also be memory intensive. I occasionally get
out of memory exception errors, but I am running it on a 32 bit OS that
doesn't even address all the memory I can socket on the motherboard. I do
wish that Andy had set it up to swap out to the hard drive (or maybe an
external memory drive) like we used to do back when memory was expensive and
the local computer gurus carried RAM in their fanny pack with their sidearm.
LOL.
So in theory atleast you could possibly get scan line resolution
calculations to within a tenth for a very simple small operation, but with
comparable step over it might take days to generate the tool paths. More
processing power, 64 bit OS, and more memory could probably help some, but
there really are practical limitations. I've generated code before that has
taken hours. For most of what I do with 3D I am happy to be within a .0015
for depth. As somebody else mentioned the fish don't really care. My
machines aren't accurate enough to get any better than that anyway. Well,
my Hurco mill is fair, but I run in CV mode with a 90 degree mode switch
limit and a .003 rounding limit most of the time.
The one thing that CamBam does that also looks like 3D is engrave a
polyline. With an engrave MOP the cutter will follow with the tool centered
on the line at the whatever depth RELATIVE TO THE LINE you set in the MOP.
This is handy for things like engraving a name on a surface. If the
polyline is not defined with bulges or arcs it will follow the line using 3
axis anywhere in 3D space that the line goes. It does not have to be on a
surface. I used this method to trick it into doing some 3D work before I
got a 3D CAD program and learned to use 3D MOPs in CamBam. CamBam also has
a nice tool to project lines to a surface. I use that with an engrave MOP
as a "trick" to engrave certain types of details into molds sometimes, and
its child's play that way to engrave a clients name into a mold that way.
CamBam is the best "affordable" hobby CAM program I have tried and in many
respects easier to use than some more expensive programs I've had the
opportunity to try.
It does not do "remaining material removal" machining. It would be nice,
but I have to figure that out for myself. If it did I would have saved
myself a dollar or two on broken cutters when I switch to a smaller cutter
for detail work. "Remaining material removal" machining is a fairly complex
bit of code to write. Constant engagement tool paths, trachoidal tool
paths, etc... HSM tool paths. Those would all be nice, but they aren't in
there. To some degree you can do it manually with good planning, but its
not powerful enough to do it all for you and take the thinking out of the
button jockey.
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