Hi there

I had someone I know contact me for advice on CAD programs.
We share a science specialism, by the way.

I visualised he was making a career-significant decision, so gave him
a huge answer.

Turns out he needed to draw in 2-D plan the position of a garage for a
neighbour...(!)

So - I offer what I wrote to my colleague.

For what it's worth...

Issues - what you will have to choose:
* pointy-clicky (eg. "Solidworks") or interpreter / command (eg. "AutoCAD")
* 2-D drawings or 3-D visualisations
* how many computer architures do you want / need to be able to work
on? (see further on - some leave you "trapped" on just one
computer-family)

I self-taught.

Was 20 years ago.
Results were like as in
http://www.weldsmith.co.uk/tech/casting/casting_fdry_credentials.pdf
see page 3

That is using AutoCAD in 3-D.

The tutorial I used was:

May 2000
"AutoCAD 2000 in 3D - A Monkish Shot Tower"
University of New South Wales
Faculty of the Built Environment
Tutorial Introductions to CAD
AutoCAD 2000 in 3D - A Monkish Shot Tower
Jim Plume

This is a PDF, obviously.

When you can get through that, you can probably run from there.

Now is your big choice - "be assimilated by The Borg, or run free as a
maverick".

"AutoCAD" has been around for a long time - as have others with that
"computer architecture".

I am writing in "emacs" (plausibly it's an abbreviation for "editor
macros").
It has been around since the late 1970's - 46 years now.
(maybe see https://en.wikipedia.org/wiki/Emacs)

I'm putting a steel beam across a 14m span - it's 200by20 flange and
400mm tall with 10mm web (that's a fictitious size), from S275 steel
(275MPa yield). What force will it bear at the midspan before
bending?

(/
(beam-fmax-ibeam-simple-cload 200e-3 400e-3 10e-3 20e-3 14 275e6) ;; 128836.19047619044
9.81 ;; g, N.m^-1
1e3 ;; kg per Tonne
) ;; 13.13314887626814

I did not type those answers.
The text editor inserted the answers into the buffer because I told it
to do so.

So, that's 13 Tonnes...

How did that happen?
I accessed the interpreter and got it to run my program - actually a
suite of functions where I started off with little ones down at
calculating the Second Moment of Area, and built from the bottom up
until the top invocation is like a language for expressing the
challenge.
I've even written a simple computer-numerical solution for heat flow.
That runs for ever, until an inspect-the-current-situation function
it calls every time it goes around the solution says "stop" (you've
got there).

AutoCAD has that architecture. At the core it has an interpreter,
written in a compiled language and compiled to a machine-code binary.
Just about all the functionality you see - it's layers and layers of
functions "riding" on the interpreter.
My little "beam load-bear" function is a simple version of that.
You read from the inside-middle outwards to the top-and-bottom.

"
...
(simple-support-dblbeam-loadcap
(beam-moment-capacity
ib-stl-sigmamax
(z-plt-ibeam ib-width ib-depth ib-web-thk ib-flange-thk))
ib-length)))
"

"z" hides inside it 2nd moment of area "I"

Programs with this architecture have gone on for decades, only
terminating if something major changes (equivalent of steam-engines to
diesel-engines).
All the commands stay the same.
You do get additions in time - eg. when computers became powerful
enough and had enough storage to handle images, you got image handling
and inserting commands... But in the totally familiar style of all
other commands.
And - they the run on any computer... The interpreter is the only
thing which needs to be "compiled" into the machine code of another
physical computer type. All the "scripts" / "functions" - they are
unchanged. The "ported" interpreter swallows them unchanged. It
presents the same interface swallowing "functions". That's the point.

I think "Solidworks" only works on "MSWindows" computers, and is
"trapped" there.
And such programs get superceded. So all your work gets "orphaned"
occasionally.

If there were a computer the "McKludge ZYX321" (eponymous other
less-well-known computer), all interpreters of the interpreter/scripts
architecture would have been "ported" onto it - including "emacs",
including "AutoCAD", etc.

AutoCAD exposes its command-line interface for drawing, and I used it
as an educational tool for developing the first principles of
geometrical thinking in my students. I could see who'd "got it"
because I could stand at the back of the class speaking instructions
and watching what was coming up as the shape expressed on their
screens.

You should search the Web.
Find your own way.

Best wishes,

"Richard Smith" wrote in message news:ly35cxptya.fsf@void.com...

For what it's worth...

-------------

The engineers kept the juicy parts for themselves, Solidworks and Spice, and
I had to content myself with the leftover crumbs which were CAD design of
printed circuit boards and simulation of digital circuits. I use a 2007 demo
version of PADS board layout software for mechanical drawing but it can't do
any mechanical simulation and doesn't export .dxf properly, and anyway I
didn't retain enough of Statics and need to practice manual beam strength
calculation. Then I proof test my assemblies with load cells.

Your work is impressive. I could immediately see why the initial casting was
flawed and the revised one sound.

I learned sand casting at age four at the small foundry next door. They
expected me to play in the sand pile but I was more interested in what
sprues and risers did, which I could see when the mold cooled enough to
approach. They used simplified patterns and sculpted the details by hand.

"Jim Wilkins" <muratlanne@gmail.com> writes:

> ...
> Your work is impressive. I could immediately see why the initial
> casting was flawed and the revised one sound.
> ...

Not really.
This is "Foundry 101"
Commercial foundries use chills all the time in sand-casting, I
understand. Blocks of steel embedded in the sand where they need to
force the casting to solidify first. In order to get sound castings.

If the comment were relating to clear style of explaining, I will have
that...

> I learned sand casting at age four at the small foundry next
> door. They expected me to play in the sand pile but I was more
> interested in what sprues and risers did, which I could see when the
> mold cooled enough to approach. They used simplified patterns and
> sculpted the details by hand.

:-)

"Richard Smith" wrote in message news:lyy1upzg2e.fsf@void.com...

"Jim Wilkins" <muratlanne@gmail.com> writes:

> ...
> Your work is impressive. I could immediately see why the initial
> casting was flawed and the revised one sound.
> ...

Not really.
This is "Foundry 101"
Commercial foundries use chills all the time in sand-casting, I
understand. Blocks of steel embedded in the sand where they need to
force the casting to solidify first. In order to get sound castings.

If the comment were relating to clear style of explaining, I will have
that...

----------------

It was.