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*Stubbington, Scott
Message 1 of 7 (44 Views)

Assembly constraints

44 Views, 6 Replies
11-07-2002 04:44 PM
I have been fiddling with Assembly constraints lately and find something I
cannot explain.... not a bug, just my limited experience probably. I have a
shaft with 1-1/4"-5 ACME screw thread, this is held by a Threaded bushing.

To be able to simulate the movement, I would need to place a rotational
constraint and a mate constraint. Turning the shaft, obviously creates a
lateral movement. I am finding the results I work out to be different to
those Inventor is returning. In the above example, I figure, turning the
handle through 360° would result in the bushing/threaded(depending on your
method of fixing) shaft moving 1/5 of a inch. This is not happening, it is
moving about 1/32 of a inch. Can someone explain what is going on.

TIA

Scott
*Dotson, Sean
Message 2 of 7 (44 Views)

Re: Assembly constraints

11-07-2002 07:59 PM in reply to: *Stubbington, Scott
If you post the files I can take a look.

BTW before you do that you might look into the motion constraints (one of
the other tabs). You can do both of these motions in one step.


----
Sean Dotson
http://www.sdotson.com
...sleep is for the weak...
----
"Scott Stubbington" wrote in message
news:8BC88717D40C8A7292F6984232444DD0@in.WebX.maYIadrTaRb...
> I have been fiddling with Assembly constraints lately and find something I
> cannot explain.... not a bug, just my limited experience probably. I have
a
> shaft with 1-1/4"-5 ACME screw thread, this is held by a Threaded
bushing.
>
> To be able to simulate the movement, I would need to place a rotational
> constraint and a mate constraint. Turning the shaft, obviously creates a
> lateral movement. I am finding the results I work out to be different to
> those Inventor is returning. In the above example, I figure, turning the
> handle through 360° would result in the bushing/threaded(depending on your
> method of fixing) shaft moving 1/5 of a inch. This is not happening, it
is
> moving about 1/32 of a inch. Can someone explain what is going on.
>
> TIA
>
> Scott
>
>
*Stubbington, Scott
Message 3 of 7 (44 Views)

Re:

11-07-2002 09:42 PM in reply to: *Stubbington, Scott
OK, file posted to CF under the same subject heading. My thoughts are in
the drawing, Engineers notes.

Sean, you mentioned the Motions Tab, I understand what your saying, but you
cannot drive these constraints and this is where I'm heading.

Scott
*Dotson, Sean
Message 4 of 7 (44 Views)

Re:

11-07-2002 10:06 PM in reply to: *Stubbington, Scott
I will be posting two example in CF.

The first is your model modified. You had two errors. The first involved
units. Notice that the d56 constraint is highlighted in red. This means
there is an error.

You typed:
d56 = d53 * 0.1411 mm

since d53 is in deg and d56 is in mm there is a conflict of units. The
second mistake is that it should be 0.014111mm you were missing a zero

(.2 in) *25.4 = 5.08 mm / 360 deg = 0.01411 mm/deg

so the correct equation would be d56 = d53 / 1 deg * 0.01411 mm (divide by
1 deg to get d53 to be unitless them multiply by mm)

The second example will show you how to use the motion constraints. Give me
a few mins to do that one and check back.

--
Sean Dotson, PE
http://www.sdotson.com
...sleep is for the weak..
-----------------------------------------
"Scott Stubbington" wrote in message
news:0849D8C313DB4544A3982FF6F2B16B17@in.WebX.maYIadrTaRb...
> OK, file posted to CF under the same subject heading. My thoughts are in
> the drawing, Engineers notes.
>
> Sean, you mentioned the Motions Tab, I understand what your saying, but
you
> cannot drive these constraints and this is where I'm heading.
>
> Scott
>
>
*Dotson, Sean
Message 5 of 7 (44 Views)

Re:

11-07-2002 10:22 PM in reply to: *Stubbington, Scott
OK the motion constrain one is up as well. To be honest I would take the
first approach (your current approach) as it's a bit more versatile. But
you can refer to it for future reference.

--
Sean Dotson, PE
http://www.sdotson.com
...sleep is for the weak..
-----------------------------------------
"Sean Dotson" wrote in message
news:smileyvery-happy:16AB3D3AF707DFF7E70C0EDC1BF8393@in.WebX.maYIadrTaRb...
> I will be posting two example in CF.
>
> The first is your model modified. You had two errors. The first involved
> units. Notice that the d56 constraint is highlighted in red. This means
> there is an error.
>
> You typed:
> d56 = d53 * 0.1411 mm
>
> since d53 is in deg and d56 is in mm there is a conflict of units. The
> second mistake is that it should be 0.014111mm you were missing a zero
>
> (.2 in) *25.4 = 5.08 mm / 360 deg = 0.01411 mm/deg
>
> so the correct equation would be d56 = d53 / 1 deg * 0.01411 mm (divide
by
> 1 deg to get d53 to be unitless them multiply by mm)
>
> The second example will show you how to use the motion constraints. Give
me
> a few mins to do that one and check back.
>
> --
> Sean Dotson, PE
> http://www.sdotson.com
> ...sleep is for the weak..
> -----------------------------------------
> "Scott Stubbington" wrote in message
> news:0849D8C313DB4544A3982FF6F2B16B17@in.WebX.maYIadrTaRb...
> > OK, file posted to CF under the same subject heading. My thoughts are
in
> > the drawing, Engineers notes.
> >
> > Sean, you mentioned the Motions Tab, I understand what your saying, but
> you
> > cannot drive these constraints and this is where I'm heading.
> >
> > Scott
> >
> >
>
>
*Stubbington, Scott
Message 6 of 7 (44 Views)

Re:

11-07-2002 10:30 PM in reply to: *Stubbington, Scott
Just grabbed your files Sean.

Thanks for clearing that up. I was trying to read about units last night, I
know the title is "Units of Measure" but I can't remember where I've hidden
it

Thank you

Scott
*Dotson, Sean
Message 7 of 7 (44 Views)

Re:

11-07-2002 10:33 PM in reply to: *Stubbington, Scott
Just remember that the equations final units have to be the same as the
units declared in the parameter. SO you will occasionally have to divide by
the unit to get a unitless answer and then multiply by the correct units.

Or you can use the isolate() function

--
Sean Dotson, PE
http://www.sdotson.com
...sleep is for the weak..
-----------------------------------------
"Scott Stubbington" wrote in message
news:75B9243A63DE1AA27AC48889392DF649@in.WebX.maYIadrTaRb...
> Just grabbed your files Sean.
>
> Thanks for clearing that up. I was trying to read about units last night,
I
> know the title is "Units of Measure" but I can't remember where I've
hidden
> it
>
> Thank you
>
> Scott
>
>

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