Tangent and Pin slot both impossible to use

dan_engerer

Hi. Tangent and pin slot almost never work intuitively, you usually have to try about 10-20 times before something works. 

Question: What is the magic "trick" to getting Onshape's pin slot/tangent mates to work? There's no indication that order matters, but I know that it does. 

Disclaimer: The solution should not involve the creation of extra mate connectors because that should not be necessary and no other CAD software requires so much extra work. 

bradley_sauln

Hey Dan, before I give my full response do you have any examples of when you are struggling with these that you can share or is this more 'in general'?

michael_mcclain

Pin-slot requires that the mate connectors be planar in the XY plane. For example, to have a connection where a slotted hole matches to a normal hole you need to set a slider mate (free Z-axis linear motion) on the normal hole and then set a pin-lot mate to the one of the half-cylinders on the end of the slot, but on the plane where the faces will end up touching each other. This mate only works in straight slots. Not curved slots. Use tangent for curved slots, but it may be best to set up a sketch in the assembly to control it better and accurately.

"Pin-Slot - Mate two entities allowing rotational movement about the Z axis and translational movement along the X axis. (Rz, Tx)"

https://cad.onshape.com/help/Content/mate-pin_slot.htm?tocpath=Desktop Help|Assemblies|Mates|_____6

"Tangent - Select a face, edge, or vertex of one entity, then select a face, edge, or vertex of the second entity"

https://cad.onshape.com/help/Content/mate-tangent.htm?tocpath=Desktop Help|Assemblies|Mates|_____9

michael_mcclain

As far as order, the only thing I can think of that is important is that the first selection will move to the position of the second selection when using any mate.

KatieHuffman

Hey Dan,

Examples like Brad requested would help with your specific use case. The tip I find useful is the first click of the Pin slot mate defines the "slot" meaning the X-axis of the first Mate connector is defining the slide direction. 

The second click is the "pin" Mate connector. Even if the X-Y axes don't align, the first Mate connector (X-axis) determines the slide direction.

Some other quick tips for understanding the Pin slot mate. Don't be confused by the name, "Pin slot" mate- really just allows translation in the X-direction of the Mate connector and rotation about the Z-axis.

I like to compare new things to concepts I already understand, so to compare a Pin slot mate to Cylindrical mate- the Cylindrical mate translates and rotates in the Z-direction of the Mate connectors.


And remember you can always realign a Mate connector to a specific edge of a part. Say my slot was slanted in the block, I can align the X-direction to be parallel to the slanted edge by editing the Mate connector and choosing the Realign option.



As far as the Tangent mate goes, that is a completely different animal, and does NOT utilize Mate connectors. Instead you pick a face, edge, vertex, or sketch entity to be tangent to a face, edge, vertex, or sketch entity of another part. Typically I use the Tangent mate for cam followers or when a part should follow the surface of another. Check out the Hahn-Sternmotor which is a public document that is a good example of when to use a Tangent mate, the rocket valve subassembly follows the Cam subassembly with tangent mates.

Don_Van_Zile

I too struggled to get the desired results with the Pin Slot mate until I figured out the tip well presented by @KatieHuffman - Great Tip and Well shown.

coleman

I also struggle with pin slot mates.  Improvements are needed.  I don’t feel like we should be required to guess and check over and over again to finally get the desired result.  

Don_Van_Zile

dan_engerer  is making a good point (even with the tip).

If I have an angled slot, but I need it's motion restricted to another linear direction (actuator driven with the Cam Roller), then it looks like I have forced to manually set the angle of the second Mate Connector shown in the gif below towards the end.I would've liked to to simply "Align" the Cam Roller's Mate Connector to the Slot (so it's not manually entered), but that's a current limitation so I'm forced the manual way. If that angle changes it won't match and "later" I won't know why.    

This is my quick workflow, but after sometime with trial and error to be sure.


In addition, when it's complete it's not limited by the size of the slot (i.e. the geometry), but that's another IR.
https://forum.onshape.com/discussion/9725/assembly-mate-limits-set-by-geometry-rather-than-dimensions

In any event, we're still far away from something like this workflow it seems.

KatieHuffman

@Don_Van_Zile you can achieve the same thing in Onshape (I believe this is what you are trying to do). In my example, I fastened the two vertical pins to a sketch (that I fixed in space). Then added three pin-slot mates between the plate and each of the three pins. I edited the X-direction (secondary axis entity) of the Mate connectors that belong to the plate to align to each respected slot. Here is that document if you are interested. I did not use any extra Mate connectors in this example. I did set a limit on one of the Pin slot mates.

From your gif it looks like you are setting the primary axis, not the secondary axis to the edge of the slot, which is why the Mate connector did not rotate as you expected. The x-axis is the secondary axis entity. Let me know if this is what you were trying to achieve.

Don_Van_Zile

@KatieHuffman - This looks to be exactly what I'm looking for! Thank you for looking into this example and I'll look into the Document setup after lunch. Looks like I'm going to be learn'n a new trick to this.  The only other thing I would be concerned about is if the angle changes (geometry of slot), does the mate still reflect the correct angle?

Don_Van_Zile

@KatieHuffman

Was this Part (Pin) rotated to this position to get the angle of the Mate Connector (See arrow) to by default on selection prior? How was this "re-aligned angle achieved with respect to your "I edited the X-direction (secondary axis entity) of the Mate connectors that belong to the plate to align to each respected slot."

KatieHuffman

@Don_Van_Zile After editing the X-axis orientation of the plate Mate connector with the Realign option, editing the Pin slot mate realigns the pin Mate connector to the new X-axis direction. That is how I got the Mate connector in that orientation, thanks for asking for clarification!

Don_Van_Zile

I think I see where I went wrong and confused coming back to assemblies after digging into creating drawings for a couple weeks. I knew I could "Realign", but it's only within the Mate Connector itself can you do this and editing post addition.

Adding or Editing an Implicit Connector it's in the dialog during creation.


Adding or Editing a Mate it's not in the dialog during creation:


You have to expand the Mate type and edit one of  the connectors post-op in order to get to the "Realign" options.

Not sure what to make of this yet as I believe this was the source of a lot of my confusion. Seems like the workflow could be improved... 

KatieHuffman

@Don_Van_Zile You can realign the Mate connectors relative to the part geometry as you discovered here. You can also realign two Mate connectors of a mate with the Flip and Reorient options. Think of the Mate connectors as defining a local coordinate system. A mate is lining Mate connectors (one from each part) on top of each other. You can flip them, clock them, and offset (in some mate types). But you can also reposition/realign the actual coordinate system, aka Mate connector, separate from defining the Mate.

An improvement request to be able to edit the Mate connector position/alignment while still editing a Mate dialog would be cool though

Check out the mating tech briefings in the Learning Center, Mating Basics, and Advanced Mating Techniques. These might help you wrap your head around some of these strategies.

Don_Van_Zile

@KatieHuffman

Thanks for the extra info again. I've watched those a few weeks backs, but am just now delving into an example I'm struggling with today to be completely honest and ironically this post from the OP.

I haven't been able to successfully add the 3rd Pin Slot mate (without overdefinig my current mating scheme I want) and simply resorted to a Tangent mate and it gives me what I want/expect, but I thought I would use 3 Pin and Slot mates.

KatieHuffman

@Don_Van_Zile looking at your Mate features list it seems you have 3 pin-slot mates already (one named Cylinder Travel). I am unsure what the planar mate is doing in the assembly. At this point it seems you have a specific document you need help with, create a support ticket, so you can share the document with our support team and get help on this specific assembly. Don't hesitate to reach out with a support ticket for help like this.

Don_Van_Zile

I just ended up getting it working by putting the Implicitly defined Mate Connector in the Part Studio for the 3rd Pin Slot Mate aligned to the angled slot; my goal was to do it at all at the assembly level. The Cylinder Travel and Planar mate is to Position the Cam Follower and limit it's motion to left to right. 

KatieHuffman

@Don_Van_Zile
I think the planar mate and the pin slot mate named Cylinder Travel might be why its over-defining when you add the pin slot mate to the angled slot- (that is my guess without actually digging into the document). In almost all cases, you only need one mate between any two parts. In my example, I added a limit to one of the pin slot mates defining the pin in one of the vertical slots. That limits the motion of the cam follower, without need for another mate. If you are still interested in setting up everything on the assembly level (I think it can be done), contact support with the feedback tool so we can better assist you on this specific design.

Don_Van_Zile

Good morning Katie,

You are partially right in that the planar mate was for "setup" purposes initially is just a redundant mate that can now be deleted without issue or change in behavior; it doesn't over define the system though (at least with my current setup).

I've created 3 versions in this document below. Please see the version name and its descriptions for my process to get it to work. I had to "manually" change the angle to 45 degrees which I don't want to resort to; I want to align it by physical geometry. I actually prefer to use the Tangent mate on the final angled slot now (limited by geometry which is optimal if done right so that the other 2 vertical slots can actually be designed "In-Context" with the motion limts with a bit extra for clearance), but there are issues with that which you can see by the dynamic drag behavior that make me question for use moving forward.

I've shared with doc with support as well.

https://cad.onshape.com/documents/d0a03b901314177801a61230/w/d32cac38c29a83f62046ff97/e/321dc4113b7c9fa80c2ff807

KatieHuffman

@Don_Van_Zile
I looked at your document, and it seems your V1 WORKS version is close. I copied that Version and made some adjustments:

1. I suppressed the planar mate and the tangent mate- for now.
2. The first thing I noticed was your Mate connector locations, I changed the Mate connectors on the Jaw to be at the ends of the slots instead of the middle. Then I made sure the X-directions were aligned in the way I wanted the Jaw to slide (relative to the slot). I did a combination of realign and reorient secondary axis button to adjust the Mate connector alignment on the Jaw and Cam rollers respectively.
3. I did move and unfix and re-fix the pins so that they both are at the bottom or top of the slot.
4. I added a limit on the Vertical Bottom Pin slot in the X-direction.- I measured the slot length and used that to define the limit.- This limits the motion instead of the planar mate.
5. For the Pin slot- Angled mate I first made sure the Mate connector for the jaw was aligned to the slot edge, then I edited the Pin slot mate and clocked the pin by clicking the Reorient secondary axis button, this gets the Mate connector orientation for the Cam roller correct.
6. I deleted the other mates- tangent and planar, and extra mate connector.

I only have three pin-slot mates for the 4 parts, and the only value I inputed was the slot length to limit the motion. Let me know what you think:

3 Pin slot mates- I shared you into my copy explicitly. 

Don_Van_Zile

Looks good! Thanks for your attention on this @KatieHuffman Those two vertical slots can be designed "In context" now as they should be with the simulated cylinder travel - AWESOME.