Difficulty figuring out a solution for door latch with a 3-point locking mechanism mate combination

Sh8dyDan

I have a door a modeled with a rotating handle that actuates a 3-point locking mechanism. Cannot figure out how to go about getting the movement or right mate combination. I have the base rotations setup but sliding parts are eluding me.

Thank you for and assistants.

https://cad.onshape.com/documents/e868d9f1b8e49f68c4eeb4cc/w/8bc6000cabf44341ab976e46/e/3325c363e7948f69a7fbec2b

jnewth

Hi @Sh8dyDan

There's a quite-unlovely way to make this work, but I'm hoping someone else can come up with a slicker way.

The movement for the Lock Rod is very strange. The simplest statement of the constraint is:
The centerline of the Rod has to pass through the vertex that defines the center of the Lock Guide hole.

The only mate I could think that would do the job here is a tangent mate. That requires vertexes and edges. This leads to the following madness:

1. Create a curve that is a straight line that runs through the center of the Lock Rod.
2. Create a composite that includes that curve and the Lock Rod. This is how we get the curve in to the assembly.
3. Replace the Lock Rod instance with the composite part that contains the curve and the Lock Rod.
4. In the lock guide, make a curve that has one of its starting points at the center of the Lock Guide hole.
5. Again, make a composite part that contains this curve and the Lock Guide
6. In your top-level assembly create a tangent mate between the Lock Rod Composite's curve and the Lock Guide Composite's vertex.

This actually works but it is objectively terrible. Let's hope someone comes up with a better solution.

(I also had to tweak your Handle sub mate to convert a revolute in to a cylindrical - some misalignment/overconstraint there).

https://cad.onshape.com/documents/84ff78e0faba8edf3874fd9b/w/80e354ea58f8f59dbb05e411/e/25c33bb46870af20b5990dee

Like I said: I dont like this approach (two composites, with weird curves, just to get this motion?!) but maybe it will help your thinking. Or trigger one of the real modelers on the forumz to save us both!

wayne_sauder

Why not just a tangent mate between the edge of the hole the rod slides through and the rod face? This does not keep the rod centered in the hole (it's not in real life anyway). Make sure to use the edge of the hole. Perhaps not the best option, and the stability of the tangent mate is always a concern (randomly switches sides), but it appears to be close enough for the application.

https://cad.onshape.com/documents/7786a7a371593b42286ffde8/w/7b5ea71cb77b4b789bb04084/e/f2d5034ff826fc855c961b78

eric_pesty

Pin slot mate is the way to go:

Two things needed:

• the bars need to be switched to a cylindrical in the sub assembly so they don't fight the pin slot.
• Setting up the pin slot mate requires re-aligning the mate connectors correctly (can be a bit tricky to figure out at first), and making sure the "pin" is the bracket and the "slot" is the bar.

https://cad.onshape.com/documents/39b72c5a7f48ca21f7442790/w/33f83356c6c30d81bd40dc7d/e/79bb269eae4bc1d3b793c43b?renderMode=0&tangentEdgeStyle=1&uiState=686ebbf446da724ad861cda4

eric_pesty

Couple more things I meant to say…
It might make more sense to move the bars up in the higher level assembly than having them part of the "lock" sub-assembly.

It would make setting up the pin slot mate easier as you would start with that and add the cylindrical mate at the bolt end afterwards

EDIT: never mind, leave the revolutes in the lock subassembly and change the mate between the lock and handle subassemblies to a slider (I edited the public doc shared earlier), that's a good match for what would actually happen as you would tighten the screw locking these two last when everything is aligned and moving correctly.

Sh8dyDan

@jnewth I like your approach to keeping the Lock Rod center to the Guide hole. I appreciate you and @wayne_sauder taking the time to help out.

I'm just shy of a month of learning to 3D CAD Model. Still learning.

Thank You

jnewth

@eric_pesty This is much nicer - really twists my brain to think of the Rod as the Slot and the Guide as the Rod. Clever!

@Sh8dyDan eric's approach is better. It uses a single mate connector and no weird composite part / curve trickery.

Sh8dyDan

Just got back online and saw @eric_pesty reply and I agree with @jnewth that this is the solution. I was initially looking at the Pin-Slot Mate but could not figure it out because it's basically backwards from the tutorials I could find.

Thank you @eric_pesty for the solution.

PS. You look like Airwick from YouTube.

S1mon

Pin-slot is very useful, but it often takes me a few tries to get it do do what I intended.

Sh8dyDan

@eric_pesty I'm getting mate overdefines revolute and slider and not consistent pin slot. Any suggestions. I thought I followed your example exactly. Must have overlooked something.

eric_pesty

https://forum.onshape.com/discussion/comment/118789#Comment_118789

Yes it can be a bit tricky to get everything setup correctly, the primary axes of the mate connectors have to be aligned correctly and the secondary axis of the "slot" (in this case rod) also has to be right, then it has to not "fight" the Z orientation of the revolute/cylindrical.

That's why I recommended putting the rod in the top level directly and doing the pin slot mate first (with no other mate) active.

You could still do this by moving the rod to the top level, deleting the revolute mates to the lock plate, setting up the pin slot, and then adding a new revolute (if you have the lock plate as as slider on the handle), or cylindrical. You can then move the rod back into the lock sub-assy and the revolute/cylindrical mate should go with it.

I can neither confirm nor deny the identity of a certain "Airwick" 😉

Sh8dyDan

I got the mate errors figured out thank you @eric_pesty.