 |
|
|
|
|
|
| |
| |
|
|
|
|
| |
| |
|
|
> I take it there's more to it then just asking the computer "hey, will this
> break if I put 25 N through it?"
Not much more, just specify which parts are fixed (eg mounting brackets) and
then tell it which surfaces to apply a force to. It will then run some sort
of iteration algorithm until it has "solved" the structure so that all
internal forces are perfectly balanced. Then you can just ask it for the
maximum stress in the structure and see how big it is compared with the
yield stress of the material...
> At what point does it become cheaper to just make the thing rather than
> simulate it?
Hmm, the first samples are always quite expensive to make because you are
making so few of them, but usually it's more a time thing than money. It
can take 2 or 3 months from finalising the design until you have assembled
samples in your hands, and of course the customer usually has a deadline for
releasing the product so you can't just carry on making more and more
samples until you get it right. If you know something is critical to get
right and you haven't done it much before, then you simulate it.
> Mmm, ingenious.
Similar to how your steering wheel is connected to the wheels by a
telescopic tube, so in the event of an accident the telescopic bits collapse
rather than the rod coming through the front of the steering wheel and into
your chest! Although Jeremy Clarkson would say that would make people drive
safer...
> Well yeah, it's going to depend on how safety-critical it is. If you're
> making a coathanger, probably not much need to test it. If you're making a
> karabina... there are probably legal requirements for exhaustive testing.
Well yes, and then you get things inbetween, like the wrist strap for the
Wii remote control, where for some reason they didn't realise it would snap
if you pulled it hard. I mean WTF how can you miss that one? I would have
thought they would have got some really strong guy to throw it around while
measuring the force, and then made sure it could withstand double or
something. Maybe Japanese "strong guys" are not that strong :-)
> One thing I always wondered... You see people doing all these crash tests,
> right? So... where the hell do you get an endless supply of red cars to
> crash into things?!
A car factory? They make lots of prototypes too for many different
purposes, btw I don't think they have to crash very many to pass the
official tests, maybe even only 1 car, IDK.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
>> I take it there's more to it then just asking the computer "hey, will
>> this break if I put 25 N through it?"
>
> Not much more
Mmm, OK.
> just specify which parts are fixed (eg mounting brackets)
> and then tell it which surfaces to apply a force to. It will then run
> some sort of iteration algorithm until it has "solved" the structure so
> that all internal forces are perfectly balanced. Then you can just ask
> it for the maximum stress in the structure and see how big it is
> compared with the yield stress of the material...
I guess like you say, working out whether a component will snap under a
given load is much easier than determining (say) whether a car engine
will explode when you ignite petrol vapour inside it.
>> At what point does it become cheaper to just make the thing rather
>> than simulate it?
>
> Hmm, the first samples are always quite expensive to make because you
> are making so few of them, but usually it's more a time thing than
> money.
Ah, but time *is* money, because...
> of course the customer usually has a deadline for releasing the product
Even so, I'm kinda surprised at the lead-time for a prototype. Mind you,
I guess if you just want to build a model of something, that's quite
easy. If you want to build it out of the real materials for strength
test purposes, that's a tad slower...
> If you know
> something is critical to get right and you haven't done it much before,
> then you simulate it.
OK.
> Similar to how your steering wheel is connected to the wheels by a
> telescopic tube, so in the event of an accident the telescopic bits
> collapse rather than the rod coming through the front of the steering
> wheel and into your chest! Although Jeremy Clarkson would say that
> would make people drive safer...
LOL! Well, Clarkson is a moron. ;-)
> Well yes, and then you get things inbetween, like the wrist strap for
> the Wii remote control, where for some reason they didn't realise it
> would snap if you pulled it hard. I mean WTF how can you miss that
> one? I would have thought they would have got some really strong guy to
> throw it around while measuring the force, and then made sure it could
> withstand double or something. Maybe Japanese "strong guys" are not
> that strong :-)
Hehehe. Apparently the world record for the loudest human shout is held
my somebody from Japan or China. They're pretty crazy people, really.
Not sure how strong though...
>> One thing I always wondered... You see people doing all these crash
>> tests, right? So... where the hell do you get an endless supply of red
>> cars to crash into things?!
>
> A car factory? They make lots of prototypes too for many different
> purposes, btw I don't think they have to crash very many to pass the
> official tests, maybe even only 1 car, IDK.
"And in this test, we're going to crash a new car into an 20-year old".
Uh, and where did you get that from, exactly?
Also, why do they already have to be painted random colours?
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Invisible <voi### [at] dev null> wrote:
> Even so, I'm kinda surprised at the lead-time for a prototype. Mind you,
> I guess if you just want to build a model of something, that's quite
> easy. If you want to build it out of the real materials for strength
> test purposes, that's a tad slower...
Even more so if you not only want to get the real material, but also the real
manufacturing process. It may make a hell of a difference, for instance,
whether you drill a hole or instead punch it. Planes have crashed due to such
details.
I guess machined parts are easy to prototype: Just feed the CAD data into a CAM
machine and wait a few moments, that's it (basically).
However, often you don't want your final product to be machined, because that's
prohibitively expensive for a lot of purposes. Pressed (is that the right
word?) or cast parts or the like are much different: They need special tools
that need to be made first (e.g., the molds in case of cast parts). Again,
they're prototypes.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
> I guess like you say, working out whether a component will snap under a
> given load is much easier than determining (say) whether a car engine will
> explode when you ignite petrol vapour inside it.
Yes, in fact some calculations you can even do by hand without simulation
just by using elementary beam bending mechanics.
> Even so, I'm kinda surprised at the lead-time for a prototype. Mind you, I
> guess if you just want to build a model of something, that's quite easy.
> If you want to build it out of the real materials for strength test
> purposes, that's a tad slower...
I did have a break down of the lead time somewhere, but there are mechanical
parts, optical parts, electrical parts, which all have to be designed in
complete detail and work together (your electrical engineer can't say he
needs a PCB that is bigger than the mechanical housing, and his circuit
needs to give the correct voltages to the LCD etc etc), then the tool-maker
must take those designs and design and build his tools, then the tools have
to be approved and tested to make sure they are making parts with the
correct accuracy, then finally the individual parts can be made (perhaps 500
pieces for a typical prototype run), and then they are assembled. For the
later prototype stages they have to actually be made using the same
equipment that will be used for mass production, so the whole assembly line
needs to be set up and checked etc.
> "And in this test, we're going to crash a new car into an 20-year old".
> Uh, and where did you get that from, exactly?
I think the crash test standards give quite detailed information about what
you have to crash into. All those crash test dummies you see are made to
exact specifications that simulate eg the 95th percentile of human
proportions and weights.
> Also, why do they already have to be painted random colours?
I don't think the colour matters too much, but they usually have all those
circular stickers on them divided into 4 for the software to easily measure
the movement and distortion of the car from the video sequence.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
scott wrote:
>> I guess like you say, working out whether a component will snap under
>> a given load is much easier than determining (say) whether a car
>> engine will explode when you ignite petrol vapour inside it.
>
> Yes, in fact some calculations you can even do by hand without
> simulation just by using elementary beam bending mechanics.
Heh. Rather you than me! ;-)
> I did have a break down of the lead time somewhere, but there are
> mechanical parts, optical parts, electrical parts, which all have to be
> designed in complete detail and work together (your electrical engineer
> can't say he needs a PCB that is bigger than the mechanical housing, and
> his circuit needs to give the correct voltages to the LCD etc etc), then
> the tool-maker must take those designs and design and build his tools,
> then the tools have to be approved and tested to make sure they are
> making parts with the correct accuracy, then finally the individual
> parts can be made (perhaps 500 pieces for a typical prototype run), and
> then they are assembled. For the later prototype stages they have to
> actually be made using the same equipment that will be used for mass
> production, so the whole assembly line needs to be set up and checked etc.
Makes you start wondering how anything ever gets made at all...
>> "And in this test, we're going to crash a new car into an 20-year
>> old". Uh, and where did you get that from, exactly?
>
> I think the crash test standards give quite detailed information about
> what you have to crash into. All those crash test dummies you see are
> made to exact specifications that simulate eg the 95th percentile of
> human proportions and weights.
...20-year old *car*. :-P
>> Also, why do they already have to be painted random colours?
>
> I don't think the colour matters too much, but they usually have all
> those circular stickers on them divided into 4 for the software to
> easily measure the movement and distortion of the car from the video
> sequence.
Oh, is *that* what those are for??
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Invisible wrote:
>>> myself. OTOH, I have yet to write a working Tic-Tac-Toe program,
>>> so... maybe not. :-/
>>
>> I did that in grade school. :) It was unbeatable.
>
> The hard part is figuring out how to draw the graphics on screen and
> register the mouse clicks. Usually you have to mutilate your program to
> fit the window manager's event loop...
Oh, mine was written in QuickBASIC under DOS. (No window manager, no
mouse, just good ol' fashioned keyboard. Fun that was..
Then I changed it so it played itself. I ran it for hours and printed
out the statistics. X wins: 0 O wins: 0 Draw: <insert number of games
played>
Heh. Good fun that was.
--
~Mike
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
scott wrote:
>
>> Usually you have to mutilate your program to fit the window manager's
>> event loop...
>
> Don't see how, if you have written functions like:
> MouseClicked(int xpixel , int ypixel)
> RedrawScreen()
Dangit! Now I have a the urge to write a C# version. I did the Towers of
hanoi problem (with a solver) in C#, that entertained me for a while.
> etc, you just need to call them in response to the correct window
> manager messages. Of course if you write the whole game as just a big
> long chunk of code you are going to find it hard to fit it in with a
> window manager.
>
> BTW why don't you just do a text based version?
>
>
--
~Mike
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
scott wrote:
>
> Some guy sitting at a computerised milling machine I would imagine.
>
> And yes, how do you make that, etc etc I think at the beginning someone
> had to make something with their bare hands :-)
probably a CNC mill with the appropriate toolpath loaded. Push a button
and wait for the finished die to pop out. ;)
--
~Mike
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
scott wrote:
>> The hard part is figuring out how to draw the graphics on screen
>
> Choose a language / IDE / API that gives you easy access to graphics?
Does one exist?
>> Usually you have to mutilate your program to fit the window manager's
>> event loop...
>
> Don't see how, if you have written functions like:
> MouseClicked(int xpixel , int ypixel)
> RedrawScreen()
> etc.
Typically you have to register callbacks with the GUI system, and then
call a "main loop" function which calls your callbacks when it feels
like it. Which is great if you just want something to happen when the
user presses a button, but becomes problematic if you want things to
happen while the user isn't pressing anything. (E.g., if you wanted to
do something compute-bound, now the GUI stops responding until the
compute task finishes.)
> BTW why don't you just do a text based version?
Because that wouldn't be very exciting?
What I'd really like to have a go at is Mahjong... but that would be
absurdly hard.
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
| |
|
|
Mike Raiford wrote:
> scott wrote:
>>
>> Some guy sitting at a computerised milling machine I would imagine.
>>
>> And yes, how do you make that, etc etc I think at the beginning
>> someone had to make something with their bare hands :-)
>
> probably a CNC mill with the appropriate toolpath loaded. Push a button
> and wait for the finished die to pop out. ;)
In that case, why are there more jobs of "CNC mill operators" than there
are for computer programmers? :-P
Post a reply to this message
|
|
| |
| |
|
|
|
|
| |
|
|
