Data Protection

Hi all,

I provide drawings and such as part of being a consultant, and was
asked today for the first time to provide models. I will comply of
course, but I have a major concern. Is it possible to "write-protect"
a model indefinately, you kknow like it's possible to protect Excel
spreadsheets, Word documents, etc? My concern (and I have seen this
happen) is that for whatever reason, a change is needed to be made to
a design that I've done. The design owner decides, hey it's just a
little modification, let's get our CAD guy to change it. Now it could
be something like a change for manufacturing purposes, or anything
else actually. The change is made, but I'm never notified for
whatever reason. The part gets made and as a result of a minor
change, a failure takes place. The next thing I know I'm named in a
lawsuit. The rest of the story is painful, time consuming and costly.

This has not happened to me personally, but I know of people that it
has happened to. Yes, I know that is why I have insurance, but it
certainly would be nice to have a fairly solid line of defense against
this occuring.

Is there an existing way to either prevent the modification, or place
a some sort of date signature in the file somehow to provide a leg of
defense against these issues? If not, I will write a VB thingy to do
a some sort of signature in the drawing.

Thanks,

Chris

 

I don't think you can write protect the file as you describe, but a checksum
should be all you need--you don't really care WHY the file changes once it
leaves your hands, just IF it changes--and you can tell that from the
checksum

 

the multi-cd approach is probably your best bet.
some things to help with keeping records that will last:
read this website: http://www.mscience.com/faq52.html
burn the cd's at a lower rate - don't burn at hyper speed. why? bob z. is
just paranoid about this one.

--
bob z.
p.s. shot through the heart...

"people with less brain power than you are doing more difficult things
everyday"©

 

another informative site about cd-r's
http://www.athensmusician.net/archive/2001-10-17_cdr01.shtml

--
bob z.
p.s.

"people with less brain power than you are doing more difficult things
everyday"©

 

I agree with Michael's suggestion, having used it myself . I always hand off
files in a zip archive. Winzip calculates a CRC checksum for each file in
the archive, and by backing up a copy of the archive you have access to the
checksums if the 'originality' of a file is questioned.

Art Woodbury

SNIP

 

you store the checksum by writing it down on a sheet of paper-- it's about
six digits long. Storing that for 20 years shouldn't be any big deal.

Changing the binary file will change the checksum (there are some exceptions
to this, but I think we can neglect them--and there are more robust methods
if you really care).

And you don't need the original file as proof--all you need is proof of what
the checksum was at the time you delivered it--a notarized letter from a
witness should be sufficient. It goes back to my original point--it's not
Chris's responsibility to find the changes if the file was altered--he
simply needs to be able to demonstrate whether it was altered or not.

If the customer chooses to migrate the file to CAD systemX (and that
includes SW2005) two years in the future, he does so at his risk--the
original engineer is not liable for any translation errors that may result

 

I'll also concur with the idea -- but be sure you include the checksum
in a message to your client(s). That way they can't come back to you
later and blame you -- they can see for themselves that the checksum
with their modified model doesn't jibe.

'Spork'

 

bob zee wrote:
.. . .

....and you're to blame. You give love a bad name.

 

Philippe Guglielmetti Wrote the following.

"If you look in apihelp.chm under "macro feature security" you'll see:
swMacroFeatureSecurityCannotBeDeleted (this is my favourite...)
swMacroFeatureSecurityNotEditable
swMacroFeatureSecurityCannotBeSuppressed
if you create a macro feature with those options and call
Feature::SetUIState(swIsHiddenInFeatureMgr) you could invisibly run
any code........"

Maybe you could use this to create a Macro Feature that would not let
any changes to be made, unless your username was found or something to
that effect.

 

Philippe Guglielmetti Wrote the following.

H'mm interesting answers from you all. I'll give it some thought and
come up with some sort of scheme before I have to do this again.

Thanks to all,

Chris

 

Even so, did they alter anything that mattered?

I (and my lawyer) disagree--in the event that a design is modified, it is
the responsibility of the modifier to document the changes, and demonstrate
that changes are not significant.

A set of (unspecified) modifications after the part leaves your hands is
essentially a "get out of jail free" card...

 

They can just say that their changes did not correct (or cause) the
fatal

and if they hope to prevail with that point, they have to demonstrate what
their changes were....


I'll stick with my current lawyer, but thanks for the suggestion....

 

Chris,

In my estimation, are not the DRAWINGS supplied adequate documentation
to define what you as the engineer have specified?

You are providing models as a convenience to a manufacturer (or end
buyer), which as I understand it is a GREAT thing. In my experience,
when a model is shared, you as the designer have a better chance of
getting the part you designed as you get rid of all "re-creation
errors".

If something is added after your design for manufacturing purposes,
this will be done regardless of your supplying models or not.

Some Ideas:

Option 1 - Supply data but with the the disclaimer that the models are
being supplied for reference puposes only.

Option 2 - Write out PDF's of your drawings to document (and freeze)
what was designed. Make this the "build" standard.

Option 3 - Supply a dumb format.

Option 4 - If you are making hybrid prints (i.e. paper print + cad
model for undimensioned features), then document this in the print by
mentioning a specific "dumb" file -> "Undimensioned features are
defined by the cad file 12345.igs"

Option 5 - Never underestimate the value of sharing your best data
with your builders. It will help them better make your parts as you
designed them.

For the legality, I have no idea what is best. Maybe don't supply
anything, including part prints, as it reduces your risk to zero.
(grin)

Regards,

SMA

 

What about just exporting and reimporting to and from Iges or
something. The advantage is they will have all the data but none of
the features can be changed without adding new features. Any new
features in their Properties will have Created by ThisPerson. Then if
changes are made it is easy to prove that they did not match the data
you sent them, and who made those changes. Seems too simple of a
solution but I think it should work. Forgive me if somebody has
already mentioned this.

Corey

 

I forgot to mention that that will make a dumb solid. Some people
know others may not.

 

Hi Cliff!

If I ran the world (I don’t as last glance) I would abolish
paper prints or rely on them to annotate things like material specs /
finishes and critical to function dimensions. But in the
today’s industry, I have yet to see many strong uses of the
model-only paradigm outside of prototyping or a fully in-company
process (particularly when a part is not designed and made at the same
company things get worse). I have see good implementations of the
CAD/paper hybrid.

I’ve been on all sides of it and have worked with paper only,
paper+cad and cad only. Each has its benefits and weaknesses. I have
worked as the guy building parts (and tooling as well) and the guy
designing parts, so I understand the value of the model.

But, unfortunately paper still holds a very high currency for those
among us who have not yet been blessed with CAD (estimators,
purchasing agents, managers, painters, platers, inspectors (usually),
etc.). The truth here is that a fully dimensioned print still holds
the highest legitimacy for many people, not all of them engineers and
manufacturers.

Regards,

SMA

I just though I might add this in response:

It is great to see that my all-powerful thoughts can still topple the
world (Smile).
Thinking is not dangerous. Tangible things are the end product of the
design process as I recall, engineering drawings (and models too) - a
means to that end. Perhaps this might not be what I think at all.

Cliff – You’re ok in my book!