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Unit parameter nightmares?

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Message 1 of 22
Anonymous
666 Views, 21 Replies
‎09-24-2003 10:07 PM
‎09-24-2003 10:07 PM

Unit parameter nightmares?

Am I the only one that is struggling with units in the parameters table. This thing is impossible to understand and is not user friendly at all. I’ve read all about converting units and all that but I still struggle with this till this day.
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Message 2 of 22
Anonymous
in reply to: Anonymous
‎09-24-2003 11:26 PM
‎09-24-2003 11:26 PM

Give us an example.  It's really quite simple
once you understand it.  All units cancel out until you are left with the
correct units.

 


--
Sean Dotson, PE

href="http://www.sdotson.com">http://www.sdotson.com
Check the Inventor
FAQ for most common questions

href="http://www.sdotson.com/faq.html">www.sdotson.com/faq.html
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Am
I the only one that is struggling with units in the parameters table. This
thing is impossible to understand and is not user friendly at all. I’ve read
all about converting units and all that but I still struggle with this till
this day.
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Message 3 of 22
Anonymous
in reply to: Anonymous
‎09-24-2003 11:39 PM
‎09-24-2003 11:39 PM

I keep having problems when dividing. example 2 mm/1 in it keeps giving me a unit mismatch.
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Message 4 of 22
Anonymous
in reply to: Anonymous
‎09-24-2003 11:48 PM
‎09-24-2003 11:48 PM

Well, for one, you can not divide like types if you want a unit in the end
(length by length, for example.) You can do what you want, but you have to
divide by the conversion factor, not the actual unit. (25.4mm = 1in) (.03937in =
1mm)

--
Dave Jacquemotte
Automation Designer
www.autoconcorp.com



"ohunome" wrote in message
news:f18d64a.1@WebX.maYIadrTaRb...
> I keep having problems when dividing. example 2 mm/1 in it keeps giving me a
unit mismatch.
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Message 5 of 22
Anonymous
in reply to: Anonymous
‎09-24-2003 11:59 PM
‎09-24-2003 11:59 PM

(2 mm / 1in) * 1 in

 

The mm and in cancel (both units of length) then
multiply by 1 in to change units to inch...

 

(2 mm / 1 in) = units of ul (unitless)


--
Sean Dotson, PE

href="http://www.sdotson.com">http://www.sdotson.com
Check the Inventor
FAQ for most common questions

href="http://www.sdotson.com/faq.html">www.sdotson.com/faq.html
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I
keep having problems when dividing. example 2 mm/1 in it keeps giving me a
unit mismatch.
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Message 6 of 22
Anonymous
in reply to: Anonymous
‎09-25-2003 12:39 AM
‎09-25-2003 12:39 AM

HUH?

 


--
Dave Hoder
Product Design
Engineer
idX Seattle

href="http://www.idxcorporation.com">www.idxcorporation.com
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Message 7 of 22
Anonymous
in reply to: Anonymous
‎09-25-2003 12:51 AM
‎09-25-2003 12:51 AM


Just type them in and see what I mean...It
works..


--
Sean Dotson, PE

href="http://www.sdotson.com">http://www.sdotson.com
Check the Inventor
FAQ for most common questions

href="http://www.sdotson.com/faq.html">www.sdotson.com/faq.html
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HUH?

 


--
Dave Hoder
Product Design
Engineer
idX Seattle

href="http://www.idxcorporation.com">www.idxcorporation.com
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Message 8 of 22
Anonymous
in reply to: Anonymous
‎09-25-2003 01:16 AM
‎09-25-2003 01:16 AM

I would expect both multiplying and divinding by 1 inch would have no effect and the end result would be 2mm. Of course the point is moot because IV is going to output the answer in whatever unit the equation is supposed to provide. (IE default units are mm then 2, default units are in then .078....)
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Message 9 of 22
Anonymous
in reply to: Anonymous
‎09-25-2003 01:20 AM
‎09-25-2003 01:20 AM

But your not dividing by 1 in. Inventor is converting the inches (or millimeters) to do the division in/in or mm/mm therefore the units cancel out and the need to multiply by 1(units) to get units back. Do it out on paper.
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Message 10 of 22
Anonymous
in reply to: Anonymous
‎09-25-2003 01:53 AM
‎09-25-2003 01:53 AM

I have no idea what you are saying. IV converts everything to cm internally and does the math. (2mm / 1in) * 1in is certainly dividing by one inch and then multiplying by 1 inch. If you need units of length after dividing length by length then you need to multiply by length. I think we all agree with that. IV will then spit the answer out in whatever the default units are OR what the parameter is specified as so it is really all moot.
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Message 11 of 22
Anonymous
in reply to: Anonymous
‎09-25-2003 02:12 AM
‎09-25-2003 02:12 AM

JD and Rich,


You are both arguing the same point.  I agree with you both.

 

Length/Length * Length = Length

 

You are right that it converts everything to cm (why cm?  why not at
least mm?).


--
Sean Dotson, PE

href="http://www.sdotson.com">http://www.sdotson.com
Check the Inventor
FAQ for most common questions

href="http://www.sdotson.com/faq.html">www.sdotson.com/faq.html
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I
have no idea what you are saying. IV converts everything to cm internally and
does the math. (2mm / 1in) * 1in is certainly dividing by one inch and then
multiplying by 1 inch. If you need units of length after dividing length by
length then you need to multiply by length. I think we all agree with that. IV
will then spit the answer out in whatever the default units are OR what the
parameter is specified as so it is really all moot.
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Message 12 of 22
Anonymous
in reply to: Anonymous
‎09-25-2003 02:17 AM
‎09-25-2003 02:17 AM

I think I spoke too soon.
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Message 13 of 22
Anonymous
in reply to: Anonymous
‎09-25-2003 02:30 AM
‎09-25-2003 02:30 AM

I think because cm is between mm and inch thus round off would occur on both instead of just one LOL. Make 'em both wrong instead of having one right and one wrong!
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Message 14 of 22
Anonymous
in reply to: Anonymous
‎09-25-2003 02:59 AM
‎09-25-2003 02:59 AM

Dunno, but I'd venture a guess that it was simply deemed the best compromise
for working with the ACIS kernel which, if I'm not mistaken, uses 10
significant digits of precision (double float data type with a few digits
lopped off as a margin of safety) to represent all model space entities and a
default dynamic range of 1e-5 to 1e4 (one more digit lopped off as a buffer
for resabs (1e-6)). There are things going on behind the curtains that I
don't pretend to understand, but I remember seeing a problem sometime back in
one of the MDT groups with a ship mast model (or something of that nature;
very long with a very high aspect ratio) that would go bonkers when the length
was in the neighborhood of 20,000 mm. All that was necessary (again, if I
remember correctly) to model the same object without problems was to change
the model units from mm to something larger, thus feeding the kernel numeric
values that were within (or not so far outside) the dynamic range.

=========================

"Sean Dotson" wrote in message
news:398F90A84E48CC699ED6F16E54E2CD74@in.WebX.maYIadrTaRb...
>........
>
> You are right that it converts everything to cm (why cm? why not at least
mm?).
>
> ........
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Message 15 of 22
Anonymous
in reply to: Anonymous
‎09-25-2003 03:09 AM
‎09-25-2003 03:09 AM

A little more articulate than what I was saying - LOL. That was my biggest problem with another Professional package, aspect ratios. Its relative accuracy didn't do long .006" parts well!
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Message 16 of 22
Anonymous
in reply to: Anonymous
‎09-25-2003 07:53 AM
‎09-25-2003 07:53 AM

Sean I'm just missing something I did type it in,
but just to check I added a dimension to another side of the rectangle I drew at
22. My units are set to mm's. So now I have a box that is long on the 22 unit
side and short on the other side at 2. I must of missed something as if I
understood you I was expecting the 2 unit length to be in inches when finished,
not mm's. Did I miss something here? It has been a bad day here so i very well
could have.

       
               
               
               
               
msk
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Message 17 of 22
Anonymous
in reply to: Anonymous
‎09-25-2003 09:16 PM
‎09-25-2003 09:16 PM

If you units are in mm you must type

 

(2 mm / 1 in) * 1 mm = units of mm

 

 


--
Sean Dotson, PE

href="http://www.sdotson.com">http://www.sdotson.com
Check the Inventor
FAQ for most common questions

href="http://www.sdotson.com/faq.html">www.sdotson.com/faq.html
-----------------------------------------------------------------------


style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">

Sean I'm just missing something I did type it in,
but just to check I added a dimension to another side of the rectangle I drew
at 22. My units are set to mm's. So now I have a box that is long on the 22
unit side and short on the other side at 2. I must of missed something as if I
understood you I was expecting the 2 unit length to be in inches when
finished, not mm's. Did I miss something here? It has been a bad day here so i
very well could have.

       
               
               
               
               
msk
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Message 18 of 22
llorden4
Collaborator
in reply to: Anonymous
‎02-06-2012 08:52 AM
‎02-06-2012 08:52 AM

I have to add my  "HUH?" into this as I have a similar conversion headache.

 

In my case I'm trying to convert a length value to unitless so I can calculate material from inventory.  I've dug around and see there's a command called ISOLATE in which I can put in a command line of ISOLATE(*LENGTH;in;ul) in the EQUATION field of my parameter dialog box and that is supposed to convert my variable named LENGTH from inches to unitless.  Keying that in does not work with my Unit/Type flagged as UL or IN. 

 

I have also attempted parts of this discussion using an equation of LENGTH * 1 ul    but that also fails to work.

 

Can someone assist me in figureing how to make this conversion and save my keyboard & forehead?

Autodesk Inventor Certified Professional
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Message 19 of 22
JDMather
Consultant
in reply to: llorden4
‎02-06-2012 09:07 AM
‎02-06-2012 09:07 AM

@llorden4 wrote:

 

I have also attempted parts of this discussion using an equation of LENGTH * 1 ul    but that also fails to work.

That makes no sense at all - you are just multiplying by 1 - not canceling units?
Attach an example file here.
You will need to create a user parameter to take your length dimension and divide out the units.

 

What version of Inventor are you using?


-----------------------------------------------------------------------------------------
Autodesk Inventor 2019 Certified Professional
Autodesk AutoCAD 2013 Certified Professional
Certified SolidWorks Professional


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Message 20 of 22
JDMather
Consultant
in reply to: JDMather
‎02-06-2012 09:46 AM
‎02-06-2012 09:46 AM

Canceling units used to be covered in HS math classes.  Sometimes it is a little trick in Inventor to figure out how to get the syntax just right for some problems.

 

(speeling even earlier)    Smiley Mad  That was supposed to be Count rather than Counrt, but you get the idea.

 

HS Units.png

 


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Autodesk Inventor 2019 Certified Professional
Autodesk AutoCAD 2013 Certified Professional
Certified SolidWorks Professional


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