On 10/10/26 14:56, Robin Szemeti via Emc-users wrote:
Yes, exactly, but that is very different to scanning an object like your
first post.
Perhaps more relevant to users like Gene is how I do most of my day to day
CAM ...
I use "Cut2D" from vectric ... I will make a simple drawing using lines,
circles, rectangles to describe the part ... its just in 2D, .. I then add
toolpath "drill these circles with 6mm drill, 20mm deep" .. "this rectangle
needs to be a pocket 10mm deep, 3 passes, cut in a raster pattern with a
finishing pass" ... etc, I can easily add in "bridges" to hold parts in
place, preview the toolpath and when ready, get a set of gcode
automatically. I can edit the drawing and recalculate the toolpaths at any
time.
Interesting. URL?
Gene does it his way, it obviously works for him, I find drawing the design
features first and then letting the software deal with the "how to create a
pocket toolpath to match the shape" etc ... providing the drawing defines
th features accurately, I getthe right result every time, without even
seeing the gcode.
It's a lot less complex than 3D CAD but for many machining operations it
produces a perfectly adequate result.
On Sat, 10 Oct 2026 at 18:54, Chris Albertson <[email protected]>
wrote:
On Oct 10, 2026, at 6:12 AM, maurice e heskett <[email protected]>
wrote:
On 10/10/26 07:42, Robin Szemeti via Emc-users wrote:
Think of it this way: You are Michelangelo carving a statue of
David
OK, let’s make the example more relevant to CAD. Let’s say you are an
architect, not a machinist. Architects are also big CAD users. But no
architect would ever, even once in his life, use G-code or OpenSCAD to
design a shopping mall.
So, a simple use of 3dCAD that shows parameters. The designer thinks a
fake column along a wall might look nice. So he draws a circle on his
screen and then a vertical line to cut it in half. Next, he erases half
the circle and ends up with the letter “D”. Next, he specifies a
dimension of 24 inches for the flat side. Then, finally, he places
the “D” on the floor and pulls it up to make a “half column.” Then he
sticks it on a wall. Then he duplicates the half column 50 times along
the walls.
Finally, he asks the software to make a photo of the building for his
client. The client says “columns are too small.”
Finally, the parametric part: The architect sees all of the columns
“depend” on the first one (because they are all copies) and the first
column depends on the letter “D” drawing he made. He sees that the “D”
is 24 inches across. He changes the 24 to 36. Next, the software changes
every column to be 36 inches wide. You can say that each of those 50
columns “depends on a parent dimension.”
Next, the client says “I like the size, but I’ve always liked those
classical-looking fluted columns.” So the architect changes the “D” to no
longer have a smooth arc and makes a more complex shape and saves it. As
soon as that sketch is saved, every column in the project updates to the
more complex shape.
Of course, it is more complicated; the columns were not just made at some
random height; the designer said to pull them to the ”wall height.” And
then when he changes “wall height,” everything that depends on that
changes: the roof moves up, the volume of concrete needed changes, and so
on.
It is surprising how few dimensions one uses when building with CAD.
Think of a house. Where do the ceiling joists go? You’d be place each
one “8 feet above the floor,” because then when the client says he wants a
100-inch ceiling, you would have to move 300 ceiling joists. SO, the
smarter architect says, “The ceiling joist goes on top of the wall and
makes direct contact with it.” Now when the wall height changes,
everything on top of it moves. How long are the wall studs? Ceiling
height minus the top and bottom rails. You use fewer numbers than you’d
think.
from a rock. There is no text file, only rock. Then 500 years later
someone uses a laser to digitize the statue. This is how 3D CAD
works:
you make an object, then maybe you need an STL file so you can print it;
the software uses lasers or whatever to measure the object and make an
STL
file.
This is entirely incorrect, this is exactly how 3D CAD does not work ...
what you are describing here is nothing more than a capture of an
object,
an uneditable rendering.
3D CAD captures the design intent, a series of decisions and
dependencies,
and from those decisions and dependencies it creates the object. A
much
better way of thinking of 3D CAD is:
You are Michelangelo carving a statue of David from a rock. You have
kept a detailed notebook of sketches, instructions, notes about the the
relative measurements of the statue, the angles of the arms and legs,
the
details of how the skin surfaces are smoothed from the limb joints etc,
everything you need to create exactly the finished work again from
another
lump of rock, even if the orginial is lost and no one even has an image
of
what it looked like. Essentially there is no rock, only the notebook,
the
text file.
500 years later, someone can perform the same task, but they can alter
any
of the design decisions or angles, or parameters used to smooth skin.
The crucial thing to remember is the CAD file usually does not store the
object at all, it stores the set of instructions (th source code if you
like) to create the object when that set of instructions is fed into a
suitable tool that can interpret them (run the code) and build the
object
from scratch.
That sounds like you are agreeing with me. Thank you.
On Sat, 10 Oct 2026 at 04:26, maurice e heskett <[email protected]>
wrote:
On 10/9/26 18:02, andy pugh wrote:
On Fri, 9 Oct 2026 at 22:25, Chris Albertson <
[email protected]>
wrote:
Next problem is the FreecAD just happens to have the worst user
interface of any 3D CAD system. It works, but the user experience is
poorer than with other systems.
I have used worse, but it was a while ago. And I am prepared to
believe that there are worse out there. But that video seems to
suggest that it's improving fast.
Arguably OpenSCAD is worse, depending on how you define "user
interface".
Debatable. I like the text src I can see and edit in real time, but
find
the editor a bit clunky.
But I am not necessarily disagreeing with your statement. I can't say
I am enjoying my ideologically-based switch from Fusion to FreeCAD. I
am not finding myself modelling for fun in quite the same way.
But I _am_ confident that _my_ models remain _my_ models and will
always work with the version of FreeCAD on _my_ computer.
The latter Exactly, Andy.
Cheers, Gene.
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