Help understanding constraints for sequencing.

[scout67]

We are using nx 8.5.0.23

I have decided it’s time to teach myself about constraints and sequencing, without much luck. I would appreciate any suggestions for training exercises or videos that deal more with sliding components than rotating. Our company uses more slide and lifter arrangements.

Attached is a basic cam-actuator assembly that is causing me problems. The cams are being pushed .72 inches by the actuator pin and following the 10 degree profile of the core block.

My issue is determining what constraints to place, on which surfaces. The core block and core pin are fixed. I’ve tried so many different combinations of constraints/surfaces and still have not found the right combination, or understanding of why this surface needs that constraint, and that surface requires this constraint.

So I’m asking if someone could please walk me through this. This seems so straight forward, however frustration has set in, and without some outside help, I’m beat.

 

[scout67]

File correction. I just noticed a misalignment between the actuator and cam that somehow was created while I was trying various combinations of things.

Please refer to the corrected file attached.

 

[JohnRBaker]

I'm not 100% sure what you mean when you say "following the 10 degree profile of the core block". Are you suggesting the the two 'listers' are to move up and away from each other? Also, you're making more work for yourself since the two lifters aer actually the same exact part. It would have been better to create a model representing just one-side and then adding TWO of them to the Assembly.

Anyway, until we get a bit more info...

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

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

 

[scout67]

John, yes the two 'lifters' are to move up and away from each other. the .72 stroke means the lifters are always maintains contact with the actuator.

The comment about more work is understandable, but this was just an exercise for myself.

Thank you.

 

[scout67]

Interesting to note:

I placed a fixed constraint on the core block and core pin. I placed a distance constraint on the 10 degree face of the core block and lifter. and a parallel constraint on the upper and lower faces of the actuator and lifter. Using the assemblies move component, dynamic position the models behave as expected. Creating a motion sequence however, the actuator is pulled off the core pin on the 10 degree path. Note: I'm only working with 1 lifter in the prior steps, to reduce the variables of errors.

 

[JohnRBaker]

OK, attached is a new modified Assembly (the Components are unchanged). Just open it and play the sequence. Part of the tirck is to use as few constraints as needed to assure that the part will stay where you want them and that they will move as you wish them to. Also keep in mind that for Sequencing to work as expected, you need to leave some degrees of freedom so that items can actually move. If everything is fully constrained then it would be as if the parts were all 'welded' together.

Anyway, look at the constraints I added to the model and I think you'll start to understand how this all works. BTW, I didn't mess with your 'Lifter' model as what you've done WILL work, just that it's not a good practice as it would be confusing to someone else if they had to debug your model or make changes to some of the Components such as the 'lifter'.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

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

 

[scout67]

Thanks John, I'm reviewing it now.