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NX MCD Joint rigidity

Experimenter
Experimenter

Hello,

I am trying to simulate injection moulding machine in NX 10 MCD. The point is, I need to close the mold with specific force. The force is a result of joint mechanism pushing (connecting) the mold togetger. I have calculated requested force and stiffness of the whole mechanism. I am trying to emulate this mechanism in MCD with the mechanism pushing against the spring damper.

 

Naturally the stiffness is really high and to create a specific force, I need to accomplish specific deformation of the spring damper. My problem is, that there is some undefined deformation in hinge joints of the mechanism. I need to have absolutely rigid hinge joint so I can accomplish the calculated deformation of the spring damper. I don´t know how to do that.

 

Výstřižek.PNGdislocated hing joint as a result of big forces applied

10 REPLIES

Re: NX MCD Joint rigidity

Siemens Phenom Siemens Phenom
Siemens Phenom

Hello 2amaze

You can tweek the physics tuning parameters in MCD preferences.

Say set the "Error Reduction Amount" to 200 and "Maximum Iterations" to a large number, say 40,000 worked on my simple test.

It's not 100% rigid but much better than the default. Depending on the complexity of your kinematics you may need to trial and error the numbers a bit.

I have also emailed the MCD product manager to see if we can get some more solutions for you. The product manager is out of the office until he 5th April so we will have to wait a few days for a respoce.

Regards

Paul

Re: NX MCD Joint rigidity

Experimenter
Experimenter

Hello Paul,
thank you very much for your advice. I will definitely try it out! Looking forward for informations from the product manager!

Kind regards

Re: NX MCD Joint rigidity

Experimenter
Experimenter
@Paul_Hartrick wrote:

Hello 2amaze

You can tweek the physics tuning parameters in MCD preferences.

Say set the "Error Reduction Amount" to 200 and "Maximum Iterations" to a large number, say 40,000 worked on my simple test.

It's not 100% rigid but much better than the default. Depending on the complexity of your kinematics you may need to trial and error the numbers a bit.

I have also emailed the MCD product manager to see if we can get some more solutions for you. The product manager is out of the office until he 5th April so we will have to wait a few days for a respoce.

Regards

Paul




May I ask you to update your answer? I would like to know the opinion of the manager you wrote about. 

Kind regatds

Re: NX MCD Joint rigidity

Siemens Phenom Siemens Phenom
Siemens Phenom

Hello @2amaze

I'll follow up today. I'm in Japan time zone and the product manager is in the German time zone so he won't get my email for a few more hours.

Regards

Paul

Re: NX MCD Joint rigidity

Siemens Phenom Siemens Phenom
Siemens Phenom

Hello @2amaze

I got some more tip from our expert who wroks closely with the PD team.

I hope this helps. There is also an attached sample file.

Regards

Paul

 

I have looked into your post and you are right increasing the Iterations and the Error Reduction Amount helps.

But as far as I know this will help MCD to calculate better (more Iterations in the same time and higher influence on the Errors with the error reduction factor) not increase the “joint stiffness” in the calculation.

 

In terms of “joint rigidity” it is only possible to increase it by changing the two rigid body components of a joint. MCD (or Bullet Engine) will calculate joint stiffness automatically given the inertia and the mass values of the two components of a joint.

You could simulate a “stiffer” joint If you change the mass calculation to “User Defined” and increase the values drastically (especially for the lighter components of your kinematic chain).

 

 

If the simulation performance is not an issue then I would use both methods in combination.

 

There is actually also another (3rd) method but this requires in most cases programming with the runtime behavior (calculate specific Joints/Rigid Body positions/orientation w/o the physics engine) but I would only use this if everything else fails since it is work intensive.

 

 

I already made a small report tool that will output the comparison of the rigid body masses in all joints to identify big differences (these are often critical, for example if you have 0.02KG and connect it to an object with 20KG).

Re: NX MCD Joint rigidity

Solution Partner Creator Solution Partner Creator
Solution Partner Creator

Hello, Patrick,
that report tool sounds good.

That's a common problem.
Can you share that?

regards
 Christian

Re: NX MCD Joint rigidity

Siemens Phenom Siemens Phenom
Siemens Phenom
Hi @ChristianS
I’ll see if it’s simwthing that’s shareable and if there is any pre-requisites or caviats.
It won’t be until next week now till I have an update.
Regards
Paul

Re: NX MCD Joint rigidity

Siemens Phenom Siemens Phenom
Siemens Phenom

@ChristianS

Small update, my colleague is busy this week at the Hannover Fair so we should have an update for you next week.

I appologize for the delay.

Regards

Paul

Re: NX MCD Joint rigidity

Siemens Phenom Siemens Phenom
Siemens Phenom

Hi @ChristianS

Due to an update to the DLL there was a longer than expected delay. Good news is that we can share the DLL and there is a small video to show its usage. Be aware this is not supported software and is provided as-is as a POC tool. In the video you can also see the utility was added to the ribbin bar for ease of use.

Enjoy.

Paul