Variable distance mating possible in NX4? 1

[evansut7]

I am trying to mate a group of 3 objects in a way that would emulate the action of a gear rack for the purposes of creating a sequence. I would like the distance between object 1 and 2 to be twice the distance between 2 and 3. Is this possible in NX4?

 

[jerry1423]

Sure it's possible but you need to use expressions.
It's been a while since I have been in NX4 so I will do my best here:
Attach the distance mates beween object 1 and 2, and object 3 & 4.
Go into your expressions. Tools > expresions
The last couple expressions will have your distance mates.
it will look something like:
p436=34
p437=68
edit the second of the two expressions:
p437=2*p436

 

[edgray]

I agree with the suggestion above but I like to create the variable names and values first.
example:
gap1=34 (I would use a more mnumonic name but I don't know your business)
gap2=gap1*2(or 2*gap1)

Then I create the assembly constraints using the expression names. Try to create your expression names so that you can easily sort them using wild cards. for example don't name them "first_gear_gap" and "second_gear_gap", name them "gear_1_gap" and "gear_2_gap" this will get then listed together when sorted by gear*. You can probably already see a better way. It's worth some thought.

 

[JohnRBaker]

The thing to remember is that even if you set-up your expressions this way, the Sequencing will not honor them since only positional constraints are maintained, not mathematical ones like recomputing a distance or angle constraint based on some change in an expression. You can still do what you want in Sequencing, it's just that it take a lot of drudge work.

However you can do this much more straightforward with Animation. Or even with a simple NX Open (GRIP) program.

I'm working on a series of simple example assemblies which will show the differences in possible approaches. When I get them done I'll post them here.

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

To an Engineer, the glass is twice as big as it needs to be.

 

[evansut7]

Thank you for the replies. There are actually just three objects so object 2 has two sets of distance mates on it. When I set it up I am unable to move individual parts of the assembly. This is for an injection mold assembly.

The goal is to create a movie by using screen capture software during the sequencing. If sequencing wont sort out this formula for me then maybe I am heading in the wrong direction. Does the drudge work involve alternating frame by frame of each motion in order to get what looks like a relatively seemless motion of both objects at the same time?

Thanks for all the help I appreciate it.

 

[JohnRBaker]

Yes, that's what I meant by 'drudge work'. Attached is a simple example using 3 blocks (but I think you'll get the point). Open the assembly and run the sequence found there.

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

To an Engineer, the glass is twice as big as it needs to be.

 

[JohnRBaker]

OK, here's another example where I'm still using the 3 blocks only this time I'm using an NX Open (GRIP) program to achieve the desired results. In this case the assembly has the distance constraints set up so that the distance between the 2nd (yellow) and 3rd (blue) block is always twice what it is between the 1st (green) and 2nd (yellow) block. This was done as previously described using a distance express for the 1st constraint and an the second constraint expression set to twice the original one.

To see how this works, open the assembly and execute the GRIP program 'animate_assy.grx'. When the 1st dialog comes up enter the Expression name "Dist". For the second dialog enter your desired values. I would go from '0.00' to '200' and set the speed to '1'. After it runs you will have a dialog where you can repeat the 'animation' or even reverse it or edit the values and try again.

Anyway, give that a try, OK?

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

To an Engineer, the glass is twice as big as it needs to be.

 

[JohnRBaker]

OK, here's another take at my simple 3 block example only this time I'm using the Animation function. Open the assembly and go to...

View -> Visualization -> Create Animation...

...and select the 'Preview Animation' button and when the 'VCR controls' dialog comes up, hit the 'play' button.

Note that if you had selected the 'Generate Animation' button instead you would have created an MPEG movie based on the options set in the 'Edit Parameters' dialog.

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Industry Sector
Cypress, CA

http://www.siemens.com/plm

http://www.plmworld.org/museum/

To an Engineer, the glass is twice as big as it needs to be.

 

[evansut7]

Thanks! I think I like the sequencing the best since I will have a lot of other stuff going on in the animation besides just this step. Thanks again for the help.