Degrees of Freedom Indicator???? 2

[adicm]

Exists???? Some of my components show the (-) sign, and as I understand, it means that they are not fully constrained, but I try to drag it to know wich is the constraint that is miss and they just don't move anyway... so, I don't know why is that symbol shown... THnks

Adi Corrales Magallanes
Centro de Ingenieria y Desarrollo Industrial
Queretaro, Mexico

 

[MadMango]

Usually this happens to cylindrical parts, where you are missing a constrant to keep it from rotating.

[green]"But what... is it good for?"[/green]
Engineer at the Advanced Computing Systems Division of IBM, 1968, commenting on the microchip.
Have you read faq731-376 to make the best use of Eng-Tips Forums?

 

[adicm]

Nop.... I always constrain one plane of the cylindrical parts to the main planes with a paralell constrain (that include the fasteners) because I hate to have parts that could move when it should not...

Adi Corrales Magallanes
Centro de Ingenieria y Desarrollo Industrial
Queretaro, Mexico

 

[cninneman]

Is it possible that the component is mated to a part that has the ability to move/rotate? I believe that all parts mated to free moving parts will be considered under defined, even if that part itself is fully defined. Just a thought.

Chris

 

[ElectroMatt]

I have this happen pretty frequently as I do a lot of cylindrical mates. Most times all it will require is a forced rebuild with CTRL+Q. Other times I have to open up the individual components and make forced rebuilds in them first. Solidworks can be very frustrating. Sketching in 2005 is a nightmare.

 

[SBaugh]

Please explain mfshadow (post in new thread). Sketching and working in SW05 is a breeze and better then SW04.

Regards,

Scott Baugh, CSWP
3DVision Technologies

http://www.3dvisiontech.com

http://www.scottjbaugh.com

faq731-376
faq559-716 - SW Fora Users

 

[adicm]

I Don't know... First, after have worked with Autocad, Mechanical Desktop, Inventor, Solid Edge for almost (well, I'm a kid in CAD) five years, I think that solidworks is pretty good and the faster Medium Level CAD, but with 2005, well.... I'm having A LOT of unexpected erros in the program and that's very annoying... I have some other problems, but I still thing is the best.

Well, going back to my question... I don't mind have the symbol (-) in my parts but I really want to know if they could move or not, because, if I share my design, my coworkers could move something that it supposed not to move, so... That's why I need to know if there is something like the degress of freedom indicator, in order to know if the part CAN REALLY move.

Adi Corrales Magallanes
Centro de Ingenieria y Desarrollo Industrial
Queretaro, Mexico

 

[SBaugh]

If you want to know whether the part will move or not is why you get a (-) in the FM. WHen I see that symbol I test the model to see how it's going to move. If for some reason I really don't want it to move, but I test moved it. You can select Undo and the model will return to it's original position.

I don't think there is a Degree of freedom indicator.

Regards,

Scott Baugh, CSWP
3DVision Technologies

http://www.3dvisiontech.com

http://www.scottjbaugh.com

faq731-376
faq559-716 - SW Fora Users

 

[MadMango]

You can always RMB the top assy and View Dependancies, then check to ensure you have the proper mates.

[green]"But what... is it good for?"[/green]
Engineer at the Advanced Computing Systems Division of IBM, 1968, commenting on the microchip.
Have you read faq731-376 to make the best use of Eng-Tips Forums?

 

[sloth4z]

I notice this sometimes with SW2001+. The wierd part is when you try to move it doesn't say that it's fixed, but it doesn't move either. I get this problem only with cylindrical parts. If I use the edges to mate instead of the surfaces, I will occasionally get this problem. I just delete all of the mates connected to the part, and then redo them, or mate it differently. The minus sign usually goes away after that. Hope this helps.

 

[macPT]

To know about degrees of freedom you must think by yourself and count "by your fingers" (I don't know any tool to help you).

You have 6 DOF: 3 translactions (along X, Y and Z) and 3 rotations (around X, Y and Z).

Examples:

When fix a part, you have all 6 DOF constarained.

When you mate 2 faces to be coincident, you are constraining 1 translaction (normal to the faces) and 2 rotations (around 2 normal axes that lay on face plane). So you will need to add mates to fix 2 translactions and 1 rotation

When you mate 2 faces to be parallel (notice the difference), you are constraining 2 rotations (around 2 normal axes that lay on face plane). So you will need to add mates to fix 3 translactions and 1 rotation

When you mate 2 faces to be concentric, you are constraining 2 translactions (2 axis normal to cilinder axe) and 2 rotations (around those 2 normal axes). So you will need to add mates to fix 1 translaction (alog cylinder axe) and 1 rotation (around cylinder axe)

And so on...

If some part is fully constrained, by analysing it's mates, and still have a (-) that's because at least one part that you use for reference (to mate) is not fully constrained. So there's a legacy from parents to children of the uncontrained satus, even if the children have all the necessary mates.

With practice you will have no problem to make this kind of analysis.

Regards

 

[adicm]

Yes, I know that. I always use my own little rule "If it have three constraintes, almost always is fully defined" Because I almost always constraint two axis and a face (my parts almost always have at least two drills for fasteners) three faces or two faces and an axis or two axis and a face(unless I need something different) For cylindrical I always constrain a face an axis and a parallel plane to one of the origin planes...

The real question is Will the part could be move for someone else, in some way that I could not find in my work station, though I try to drag, rotate, even overdefine the part and it just don't move, but SW still show me the (-)?

Adi Corrales Magallanes
Centro de Ingenieria y Desarrollo Industrial
Queretaro, Mexico

 

[macPT]

Well, I don't know the correct answer to your last question, but, for the safety of your design, you must think that it can be possible. If there's a (-), then it can move. And if you are not able to find how to move it, then it will be a more dangerous problem, as it can be moved by someone in an unpredicted way and ruin your design.

So if there's a way that this (-) can afect your design, then you should add all the necessary constraints. You should keep a (-) only in cases that will not afect the final result in anyway.

Regards