NX9 - MEASURE BODIES / SOLID DENSITY

[Kenja824]

Quite often I have solid bodies that are not correct on the insides because it doesnt matter. I cannot add a material and get a correct weight, but I do know what the weight is supposed to be. The only way I know to get the weight correct is to keep playing with the Solid Density until I get the mass correct.

Is there a way to select a solid body and give it a specific mass and the solid density will adjust accordingly? I do need this body to be correct when doing a Measure Bodies. It cant just have a mass attribute given to it.

 

[JohnRBaker]

If you have an Advanced Assemblies license you 'Assert' the weight and other mass property values to a Component.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[Kenja824]

Doing a search, I can use something called Weight Management that allows me to control the weight of components. I was hoping to give it right to the solid body but this may be workable.

I dont know if that is what you are talking about or not. I have never heard of Advanced Assemblies and nothing comes up with that name in a search.

 

[JohnRBaker]

Yes, that's it. Give it shot as they may have changed the license behavior since I last had to verify it.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[Kenja824]

Starting to think this may not work for me, as it allows you to control the weight of components. Where I would need it most often is not necessarily a component but when making family parts. Sometimes it is easier to make the family parts using different bodies rather than one body that has features that change. Family parts are automatically read only and therefore I cannot control their weights and keep them that way.

I do see where Weight Management has a check box for "Use Spreadsheet", but I am not seeing how to make that work for a single file with multiple bodies and no components.

 

[JohnRBaker]

If I recall correctly, there's an option when creating a Family Table Part to assign weights (I know you can do densities) from the same spreadsheet data as you would parametric dimensions.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[Toost]

Yes, you can assert mass both using the weight management or in the part family .
If you search for weight management, the sub dialog has a button Assert Values : work part where you can assign weight, area, COG etc

The part family option is only mass ( not COG)
It's assigned to the part , not the body.
IF you include asserted mass in your assembly, you need to calculate the assembly using the weight management dialog. The "measure bodies" does not include asserted values. ( for some un-known reason...)

Regards,
Tomas

 

[Kenja824]

Unfortunately our weights seem to all be driven from doing Measure Bodies. I need the mass to come out correct when doing Measure Bodies and it looks like the only way to set that for solid bodies is

A) Assign Materials - Which will automatically go by the solid body and will come out wrong if the inner working parts of the body are not designed right. Make a Shotpin and leave the cylinder as solid and the mass ends up extremely high.

B) Edit the Solid Density - Which is to just take a basic guess and work from there until you get the Mass to come out right. Edit the Solid Density, check the Measure Bodies mass, change the density check the mass, edit the density... etc

If there is a suggestion box we can use, put me in for a UG Function that you actually enter the MASS and it changes the solid density to what it needs to be for that mass. ) I run into this problem a lot and it eats up a lot of time to get each part right.

 

[cowski]

Sounds like a great time to put the expression system or a journal to work...

Measure the body to find the volume then divide the desired mass by the body's volume to find the density value that would result in the desired mass. Assign that value as the solid's density. No guess work required.

www.nxjournaling.com

 

[Kenja824]

Well it sounds like someone has an engineering degree and its obviously not me. lol Thanks, I will give that a try as soon as I can get back to it. I seem to get yanked around with new jobs so much lately, one would think I worked with my wife.

 

[Toost]

I don't really understand this.
You know the weight but still want to calculate it ?
There is something enforcing you to use the measure bodies instead of the weight management ?
( provided you have that license.)
Yes , there is another calculation option in the weight management dialog, which includes asserted values. Including COG.

Regards,
Tomas

 

[Kenja824]

Its a weird multi-part scenario I guess.
1) Of around 100 people in the company, I would be surprised if more than 5 are even aware of the Weight Management way. Everyone has always been taught by the others to simply do a Measure Bodies. No matter how much I push for it, there are going to be those who continue to do it the old way. When it comes to teaching new tricks, old dogs have nothing on old engineers.
2) Weight Management seems to be great for checking the weights to assemblies and components and work files. When modeling with solid bodies and designing a large end effector that has many bodies and needs to stay within a specific weight limit, the designers are not going to have details to check the weights to. They will have multiple solid bodies and are not going to turn them into details until after the end effector is right and under the weight limit. They wont want to make the bodies into details and then find out they need to redesign it all. So they will continue to do measure bodies.
3) When making family parts with a lot of solid bodies in them, I often will get someone complaining to me that this component or that component is coming out with the wrong weight. Usually because I forgot to adjust that to the bodies. The Weight management way would be great and easy for me to make these family parts, but then when they add the components to their tools and do their measure bodies, they get a different number all together.

At least this is how it works the way I am understanding it.

It looks like I will either have to do it the hard way of changing the density or get a group of old designers to change how they do things. I am betting I lose this fight. But Cowski's math trick will save me a lot of trouble I think. Cant wait to get back to that.

 

[Toost]

Ok. I see the point. I ( we) kind of have the same issue here. We have a lots of components which are bought from other companies where we know the weight and the COG , and the exterior shape. - the weight management - assert weight etc fits like a glove, but the damn measure bodies don't bother about asserted weights....

What is an Effector ?

Regards,
Tomas

 

[Kenja824]

An "End Effector" is a tool designed to attach to the end of a robot arm and pick up car body parts. A robot can only lift so much weight depending on its reach and so quite often the designers need to keep changing their original design to make it light enough for the robot to handle swinging it and a body part around.

 

[JohnRBaker]

Are you sure about Measure Bodies not working as expected? If you're working in an Assembly and select the Components themselves, you should get the correct overall weight even if some of the Components have Asserted mass properties.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[Kenja824]

I am as sure as I can be with my knowledge level. I created a family part yesterday and used the Asserted Mass (kg) added to the spread sheet. I gave one of the parts a 1.02 kg. When I brought the part into another file and did a Weight Management check, it gave me the correct weight. When I did the Measure bodies, it gave me something like 11kg because it was a solid body where in real life the part would be hollowed out for wires and such.

I guess there is a chance I am doing something wrong, but Toost seems to have faced the same problem.

 

[JohnRBaker]

Make sure that you're in the context of an Assembly and that you're selecting ONLY the Components.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[cowski]

2) Weight Management seems to be great for checking the weights to assemblies and components and work files. When modeling with solid bodies and designing a large end effector that has many bodies and needs to stay within a specific weight limit, the designers are not going to have details to check the weights to. They will have multiple solid bodies and are not going to turn them into details until after the end effector is right and under the weight limit. They wont want to make the bodies into details and then find out they need to redesign it all. So they will continue to do measure bodies.

Perhaps I am not interpreting this correctly (details = components?), but it sounds like they are using a top-down approach where they start with a bunch of bodies in a part file and break them out into components later. I'm not sure that asserting weights via weight management would work in this scenario.

www.nxjournaling.com

 

[Kenja824]

Cowski - Yes in both cases. They do the Top Down approach usually and Details = Components. We have grown accustomed to calling any standard item we bring in that is already designed and purchased from other companies Components. Any child of an assembly we created to be made special for our tools by a build shop are Details. Sorry for the confusion.

John - After creating the family parts, I went into a completely different file and added one of the family members through ADD COMPONENT. When I did the Measure Bodies, I selected it off the screen. The problem I believe is that in Measure Bodies, it selects the solid body of the component and not the component itself. When asserting the weights through Weight Management, it adds the weight to the component and not the solid body. I would be great if I could use Weight Management and add the weight to the body as well, but it doesnt seem to work that way.

 

[JohnRBaker]

I believe (if I recall correctly) there's a selection setting/option controlling whether bodies of a Component are included when selecting the Component itself.

John R. Baker, P.E. (ret)
EX-Product 'Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without