Parallel mating query

Gary_Creaney

I have attached an (extremely crude) image to better explain my query.
Imagine that the 2 parts are sheets of metal extruded down into the page. I am trying to maintain the parallel distance, achieved using a custom mate connector but mate the other two faces as indicated. Again, apologies for the crude image.

NeilCooke

Use a planar mate with an offset

Gary_Creaney

Neil, thanks for the reply. I am fairly new to onshape and whilst I understand some of the basics of mating and I can see the options of the offset within the planar mate command, I'm not sure at all how to fully carry out what you have suggested. I'm sure it's not easy to explain either but can you or anyone offer a little more detail?

NeilCooke

Hi Gary - here's how you do it. Don't forget that in some cases it may be better to create all the parts together in a Part Studio if they are fixed relative to one another. We only really use Assemblies for motion or for duplicating many parts like fasteners.

Gary_Creaney

Thanks again Neil, your advice regarding the creation of this in a part studio makes sense that I will take on board for this type of thing.
I have followed your demo exactly as above and it is almost there. The only difficulty I have is that the planar movement in your demo i.e it slides in the direction of the offset does not seem to work for me, the blue item only wants to slide along the length of the yellow one rather than away from it. If I could get that worked out then I'm sorted here.

NeilCooke

Is it possible you selected an edge instead of a face for the mate connector?

Gary_Creaney

I double checked to be sure but my first step is exactly like the one in the demo. The planar movement allows only allows the 2 parts to move away from each other but not in the direction that yours does i.e the one I am hoping to achieve.

Gary_Creaney

Though now that I look at yours Neil, it appears to be drawn on the front face whereas mine is drawn on the top. Does that make the difference?

NeilCooke

Direction makes no difference - before the video I added a planar mate between the two part end faces so the parts couldn't move along the bend axis relative to each other, then the first planar mate in the video makes the two angled faces slide up and down each other, then the third planar mate (which has a 15mm offset) fixes the distance between the two flat faces.

philip_thomas

If you want the distance between the parts to be able to vary, then a SLIDER mate would be what's needed.

The trick with this methodology of using high-level mates is to always think about which degrees of freedom (DOF) you want to exist.
In order (of mate connector based mates) of increasing DOF
Fastened - 0 DOF
Revolute - 1 rotational DOF
Slider - 1 translational DOF
PinSlot - 1 translational DOF
Planer - 2 translational DOF
Cylindrical - 1 translational and 1 rotational DOF
BallSocket - 3 rotational DOF

The benefit of this system is that it will typically take fewer high level mates than the same mechanism created with low level mates.

Gary_Creaney

Thanks again. I want exactly what Neil's demo has shown. The offset dimension I require is 55mm and when I use a planar mate as per the demo, it so happens to come out at 55.16mm so I am able to continue. It appears that the step carried out before the video is what I need to do to make this work. In future though this type of thing would be better done together as parts rather than an assembly as has been suggested. 

Have to say, loving the community and onshape in general. Excellent guys.