Is there a Tangent Mate?

chrisjh777

 I need to mate the end of one cylinder to the surface of a second cylinder.

What I am trying to do is tangent mate the end of the Thumb Screw to the surface of the Shaft in the assembly below:

https://cad.onshape.com/documents/4d648f707f1c47a59321f305/w/51b182b7178c48faa2063497

philip_thomas

For fun I made a number of mating examples typical of weldments including a layout sketch example - https://cad.onshape.com/documents/6ba1e39775d942b78b0c84f1/w/cdfcad3a3d7f4565ad4ffef4/e/61db20db6c0b4197818cef4d

andrew_troup

Refer this recent thread, where a very good workaround was provided:

https://forum.onshape.com/discussion/1507/tangent-mate#latest

andrew_troup

@chrisjh777
A more in-depth and tailored answer: Onshape is optimised to create static relationships between parts in the Part Studio environment.
Although on the face of it, your thumbscrew slides along the shaft, the tangency relationship is not affected by this, so it is preferable to create that relationship in a single Part Studio containing both parts.

Having had a spare moment now to look at your model, I see that you are using a traditional workflow, creating all the parts in separate studios.

I suggest having a look at this video:
https://www.onshape.com/learn/essential-training-series#!lesson-number=3&title=multipart 

It's not an exact match for what you're trying to do, but I think you might find it an eye-opener as to the advantages of discarding the workflows from legacy modellers, when using Onshape. In your case I might even be inclined to model all the parts in a single Studio. When you bring them into an assembly, you can "Fix" the base, then use "Group" to immobilise the non-moving parts (they will remain in the same relative positions to the base as they were modelled with: if you want to change one of the positions, you can simply edit the relationship in the Studio, and the part will move itself in the assembly)

So in your example, you could conceivably manage with only one mate, for the sliding collar, unless you want to go to the trouble of providing a 'screw' mate for the nut.

chrisjh777

Thanks Andrew,

I'll investigate further when time permits.  I am of the age where old habits die hard.

I had considered making a sub assembly of the Thumbscrew and Collar (I like this description) and then adding this to the main assembly.  But as a training exercise, I decided to mate all the parts into the final assembly, the method I use in Solidworks. 

I just recently came to understand the concept of "Multi-Body Parts" in Solidworks, when I assisted a novice with his design.  He had designed his complex sheetmetal assembly as a multi body part, and it took me some time to come to grips with what he had done.  I then understood the concept and the benefits of things like cut lists.

I am using simple projects like this to:

a.  Teach myself Onshape, and

b.  Document things that I have done in the past, so I have a permanent record. Normally I would have done this in SW and backed it up, but because it was a one off, I decided to use Onshape.

andrew_troup

Thanks for clarifying that, @chrisjh777
I should perhaps have added a warning, to the effect that you might be in for a frustrating time if you persevere with trying to use Onshape the way you would use Solidworks: the tangent mate is just the tip of a large iceberg of missing functionality.

Some of it will never be available, because it just does not fit with the way Onshape is architected.

Here's a poor analogy: in spite of the early carmakers seeing the sense of adopting certain features of the horseless carriage, such as wheels, gloveboxes, lights, running boards and cargo compartments, it served no purpose at all to provide reins or whip-holders.

A simple rule of thumb to avoid frustration:
use Part studios for parts and groups of parts, wherever geometric relations will be sufficient to capture relative positions. (or more simplistically: where motion is not involved)
Use Assemblies in Onshape only to provide control of relative motion.

philip_thomas

For fun I made a number of mating examples typical of weldments including a layout sketch example - https://cad.onshape.com/documents/6ba1e39775d942b78b0c84f1/w/cdfcad3a3d7f4565ad4ffef4/e/61db20db6c0b4197818cef4d

andrew_troup

What, @philip_thomas - no dodecahedral weldments ... yet?  (in-joke)

chrisjh777

Thanks for the guidance, guys.

I will use a slider mate for this instance.