How to limit degrees of freedom in mates

robert_westling

Is it possible to provide limits on movement in a mate?  For instance, if you use a slider mate, can you assign values to the max distance a part can slide along an axis?  The intent here is to be able to build assemblies where interference would limit the degree of freedom.

Thanks in advance for any assistance.

-robert

viru

@robert_westling , Currently this capability is not available. In future we hope it will introduce by onshape

andrew_troup

Two things for future users who may bring this thread up in a search:

Firstly, the title is potentially slightly misleading as to the OP's question, because "degrees of freedom" has a different and important significance in motion control and analysis, rather than the notion the OP is seeking help with, the ability to set limits to movement along or about a particular axis.

An item which is unconstrained has six degrees of freedom (three rotational, and three linear translation); whereas a fully constrained (fixed) item has none. Mates are essentially ways of tying down some or all of these degrees of freedom, by aligning them with axes external to the component.

So: for those who want to see how to align particular degrees of freedom for a given component, I recommend this clip, starting 15m20s in:

https://youtu.be/ANfOBv-R2tQ?t=920

... And for those who on the other hand (like the OP) wish to set limits to motion, the good news is that, as of 08 AUG 2015, Onshape now has a "Limit" checkbox in all applicable mate types to do exactly that.

viru

@robert_westling , Currently this capability is not available. In future we hope it will introduce by onshape

robert_westling

Thank you for the quick reply.  This is sort of a non-starter for my work, so I look forward to Onshape introducing it.  I believe that in SW this would be done using 'distance' mates.  (I'm not an SW user, just learning the solid modeling lingo.)

raj_Onshape

@robert_westling A distance mate could can be achieved by using fastened , planar or slider mate depending on the your requirement and using appropriate offset on the mate connectors

robert_westling

@ptrajkumar Thank you for your reply. I'll look into making this work for me. I'm partly motivated by the quote I just received from an SW dealer here in the UK! Cheers, Robert

robert_westling

@ptrajkumar  It appears there are two distance mate types in SW.  One is like the offset in OS, the other, which is the one I am looking for, allows you to provide limits for a range of motion, rather than a fixed offset distance.  So, with a slider, you can set constraints on how far a slider can travel along it's free axis. And, with interference checking, you can base the mate setting on the distance the part would run into another part.  So, I hope this is being worked on by OS.

brucebartlett

@robert_westling has definitely gone in as a request in the past, make sure you put a request in, to build a case for this feature, more requests more attention it will get to be worked on, you will also get an update when it is implemented.,

You can also use RMB "Reset" on the slider mate and other mates. This is a great feature to get you back to your initial set position.  

robert_westling

brucebartlett thanks, I've used the ? feedback button to request this be added.  Yes, I've been using the reset feature as I've been messing about with mates.  I do find it surprising that this was not implemented right off the bat.

peter_hall

+1 for constraints on mates movements as @robert_westling  last comment. Is there an easy way to add oneself to a past request or do we need to put in individual requests each time we support an idea?

andrew_troup

Two things for future users who may bring this thread up in a search:

Firstly, the title is potentially slightly misleading as to the OP's question, because "degrees of freedom" has a different and important significance in motion control and analysis, rather than the notion the OP is seeking help with, the ability to set limits to movement along or about a particular axis.

An item which is unconstrained has six degrees of freedom (three rotational, and three linear translation); whereas a fully constrained (fixed) item has none. Mates are essentially ways of tying down some or all of these degrees of freedom, by aligning them with axes external to the component.

So: for those who want to see how to align particular degrees of freedom for a given component, I recommend this clip, starting 15m20s in:

https://youtu.be/ANfOBv-R2tQ?t=920

... And for those who on the other hand (like the OP) wish to set limits to motion, the good news is that, as of 08 AUG 2015, Onshape now has a "Limit" checkbox in all applicable mate types to do exactly that.