How to Mate these Parts?

Don_Van_Zile

I have 2 Instances of the Links (gray) that I would like to have the Pin mated cylindrical and centered between as shown in the pics below.



I tried to create an "implicit" Mate Connector between the 2 Links, but cannot because the error says they can't be from the same instances (as shown below).



What's the best suggestion on how to mate this scenario with that design intent in mind. I want to avoid offsetting by an input distance to keep the Pin centered between the 2 links because that may change and I want the system to deal with that math as the design changes.

Thank in advance for any guidance.

brucebartlett

In your assembly creating mate connector using the between setting across 2 instances seems like the obvious solution and not sure why it hasn't been allowed.

Not the ideal solution but can you mate to the hole with a cylindrical mate and position central with a planar mate off the central mate connector on the pin and the central mate connector in the purple parts pin hole. 

brucebartlett

In your assembly creating mate connector using the between setting across 2 instances seems like the obvious solution and not sure why it hasn't been allowed.

Not the ideal solution but can you mate to the hole with a cylindrical mate and position central with a planar mate off the central mate connector on the pin and the central mate connector in the purple parts pin hole. 

larry_hawes

The webinar went over this exact scenario today but I've spent the last half hour trying and googling the technique but cannot remember nor duplicate what looked so so simple in the webinar. What I don't remember is using an edge for an origin entity but I realize that's very little help. I'm not giving up yet but really have no clue from any of the online help or what little I can remember from the webinar....

larry_hawes

My feeling without seeing the document is that the 2 instances of the link need to be set up in a way they are perfectly aligned in order to get the between entity mate to line up. If they already have revolute mates and they can rotate about the orange pin or rod perhaps that freedom of movement will not allow the between mate to be generated?

larry_hawes

I can get it to work in one type of assembly but not another. Stumped again...

http://www.youtube.com/watch?v=VJBkMytVI-o

https://cad.onshape.com/documents/aeb2995e3630b634343bfff4/w/fb7b492387a8063f23ba8e25/e/249fa2e265b0ad56cf3825b7

owen_sparks

Hi @Don_Van_Zile

Great screen mark ups

I can't think of an easier method than Bruce's for just working in the assembly.

If you've modeled the purple part in the same studio as the grey problem part then things get easier.

You could:-

(a) Use a layout sketch and project the width of the purple part onto it, use split to cut it in half, then add a vertex for the mate on the grey part and add an equal constraint to make it match the length of the split line. 

(b) Use the measure distance featurescript (to grab the width of the purple part and store it in a variable) and then set the mate offset to that variable / 2

Either of these is pretty ugly, but they are at least parametric.

If they're not in the same partstudio then there is a way to build global variables but it's not as mainstream as I'm sure OS will make in in due course. 

It's usually at this point that @philip_thomas jumps in and points out something simple we've missed.

Owen S.

brucebartlett

brucebartlett said:

In your assembly creating mate connector using the between setting across 2 instances seems like the obvious solution and not sure why it hasn't been allowed.

Re-reading this, what I meant was that I believe we should be able to go across part to get a between mate connector maybe we need an IR unless there is a technical reason why this is not possible, like taking to much computing power when parts are floating. 

In the past, I have used the studio modeled mate connectors for things like this but it annoys me when I have parts that end up with mate connector that hang out in random positions if the same part is used elsewhere in the assembly. 

NeilCooke

@brucebartlett 's method of using planar mate from purple part and cylindrical mate is the only way to do it. I never understood why a "between entities" mate connector has to belong to the same part - IR time people ---->

owen_sparks

NeilCooke said:

@brucebartlett 's method of using planar mate from purple part and cylindrical mate is the only way to do it. I never understood why a "between entities" mate connector has to belong to the same part - IR time people ---->

Hi folks, I believe the current strategy of not allowing between makes sense if the parts can move relative to each other, but if they're a group then it should be allowed.

Hands up, who's gonna do the IR?

O.S.

brucebartlett

@NeilCooke another way is using the linear relation. I had to check as I thought it may fail but it did not.  This could be handy if no purple part was available. 

Go for it with the IR @owen_sparks I'll vote

MBartlett21

brucebartlett said:

Go for it with the IR @owen_sparks I'll vote

@owen_sparks
So will I!

NeilCooke

brucebartlett said:

@NeilCooke another way is using the linear relation. I had to check as I thought it may fail but it did not.  

Never would have thought of that!

Create two cylindrical mates - one between the pin and the hole on one part and the same on the other. Then set a linear relation of 1 between those two mates. Genius!

owen_sparks

Wow, good lateral thinking Bruce

IR here for those interested:-

IR to allow mates between multiple instances

Cheers,

Owen S.

philip_thomas

@owen_sparks - i am slammed until noon - i will look at this then. Neil is on the case and i am pretty sure that whatever he comes up with will be the most efficient

larry_hawes

larry_hawes said:

If they already have revolute mates and they can rotate about the orange pin or rod perhaps that freedom of movement will not allow the between mate to be generated?

Is this the basic problem when trying to create a mate between entities in this model's case?

billy2

Here's the issue:
-in an assy
-there's only one part in the assy, there are many instances of that part
-mate connector between instances of a part won't work



Currently they have to be 2 different parts, not instances of the same part.

larry_hawes

Using 2 parts instead of 2 instances of the same part seemed to make no difference in this simple public doc. In my brief experience it has to be one part, not 2. I boolean unioned the parts in to one part and the between entity mate worked fine. Wouldn't between 2 different parts, or instance of same part. Probably some good logic for same but in the OP's example there seems to be a need to create between entity mates between 2 different parts or instances of the same part.

https://cad.onshape.com/documents/aeb2995e3630b634343bfff4/w/fb7b492387a8063f23ba8e25/e/249fa2e265b0ad56cf3825b7

billy2

Here's another mate connector bug, IR or what ever; mate connector owner is surface:

Don_Van_Zile

 larry_hawes said:

The webinar went over this exact scenario today but I've spent the last half hour trying and googling the technique but cannot remember nor duplicate what looked so so simple in the webinar. What I don't remember is using an edge for an origin entity but I realize that's very little help. I'm not giving up yet but really have no clue from any of the online help or what little I can remember from the webinar....

I believe you're referring to the toggle clamp within the Learning Path example. However, this is a single part and not two instances. I originally thought the same thing.

brucebartlett said:

Not the ideal solution but can you mate to the hole with a cylindrical mate and position central with a planar mate off the central mate connector on the pin and the central mate connector in the purple parts pin hole. 

Bruce's solution gets me what I want, but I agree that it's not ideal... The workflow I was trying to do that doesn't "currently" work is what I'm after. 

owen_sparks said:

IR here for those interested:-

IR to allow mates between multiple instances

Cheers,

Owen S.

Thanks Owen for the IR.

brucebartlett said:

@NeilCooke another way is using the linear relation. I had to check as I thought it may fail but it did not.  This could be handy if no purple part was available. 

Go for it with the IR @owen_sparks I'll vote

Bruce, you're a genius!

billy2

wow, it just doesn't work:



You're right.

-in an assy
-2 different parts
-mate connector between 2 different parts, doesn't work

NeilCooke

@billy2 - none of what you mention are bugs, they are working as designed. Please add your vote to the IRs to change their behaviour.

Don_Van_Zile

brucebartlett said:

brucebartlett said:

In your assembly creating mate connector using the between setting across 2 instances seems like the obvious solution and not sure why it hasn't been allowed.

Re-reading this, what I meant was that I believe we should be able to go across part to get a between mate connector maybe we need an IR unless there is a technical reason why this is not possible, like taking to much computing power when parts are floating. 

larry_hawes said:

Using 2 parts instead of 2 instances of the same part seemed to make no difference in this simple public doc. In my brief experience it has to be one part, not 2. I boolean unioned the parts in to one part and the between entity mate worked fine. Wouldn't between 2 different parts, or instance of same part. Probably some good logic for same but in the OP's example there seems to be a need to create between entity mates between 2 different parts or instances of the same part.

  It would seem like bad practice to go between 2 parts (same instance or not) that are floating or have all degrees of freedom open. However, adding mates limiting this freedom is the reason for adding mates and creating mate connectors!    I suppose it would depend on how many degrees of freedom are open for this to make sense. In my example (OP), the "Between Entities" are mated to always be Parallel to each other based on other mate connectors which would make sense to be allowed.

philip_thomas

OK - i have played with this and agree -  Bruce is the winner

larry_hawes

Don_Van_Zile said:

  It would seem like bad practice to go between 2 parts (same instance or not) that are floating or have all degrees of freedom open. However, adding mates limiting this freedom is the reason for adding mates and creating mate connectors!    I suppose it would depend on how many degrees of freedom are open for this to make sense. In my example (OP), the "Between Entities" are mated to always be Parallel to each other based on other mate connectors which would make sense to be allowed.

Yes, it would require some careful thought as to when 'between entity' mates should be allowed between different parts, depending, as you suggest, on the degrees of freedom between those 2 parts. A bit sticky me thinks but I can see where your desires in the OP are very relevant to many design scenarios.

philip_thomas

@Billy2 - I hope you watched the Webinar - an entire slide was dedicated to you!!!!

billy2

got it! in-context!

So I created a pin in context that'll expand as link are moved apart keeping link centered:


Design link part in-context with assy:


This seems a little complicated.


FYI

I tried using a sketch via incontext (sketch will update based on links position): 


Reading @larry_hawes post, I could have used the 3D spline feature script and not forced a plane, line & midpoint. This would've / could've allowed the mating links to be anywhere & any orientation satisfying Larry's want. Except the line, curve or wire won't work with mate connectors because it's not a solid.


I'm trying to keep this assignment small, neat & understandable. Mate connectors must attach to a solid body.

larry_hawes

Brilliant thread and posts and information. Many thanks for all the insights.

billy2

@philip I'm on an airplane currently flying across country. Working on OS on airplane's wifi.

Did you post? Looking for webinar "Billy2 the magnificent".

You know, there's going to be a lot of assembly use cases. Please keep in mind that these are obvious things a user will do and in the end, OS will be better. We all have the same end goal.

bug vs. IR, kindly & sorry, from your perspective it's not working as intended and it's an IR, from a users perspective it's a bug. I'm hoping these things are lifted up in status with higher priority sooner than your IR process.

philip_thomas

@billy2 - you make a guest appearence in my webinar at 1:11:10

https://www.onshape.com/videos/onshape-assemblies-for-solidworks-users-071018

billy2

@brucebartlett got your idea to work, I'd never figure that one out. Good Job!

philip_thomas

Whats really nice about that solution is that my guess is that it works even if you change the length of the pin!