topic Re: New revolve joint disconnects existing revolve joint in Fusion Support Forum

New revolve joint disconnects existing revolve joint

sotooleAC4DP — Fri, 21 Jul 2017 00:02:29 GMT

Hi f360 community!

I am trying to complete a tutorial on you tube:

https://www.youtube.com/watch?v=Muj4c_eCK3A&t=210s

When I attempt to make the joints that connect the arm to the two sliders, the second joint seems to result in the first joint suddenly no longer being "joined." I have no idea what the problem is and have attempted to make joints at least 2 dozen times.

Any chance someone could take a look and let me know what I'm doing wrong?

The file is here: http://a360.co/2ufEqxK

Many thanks.

-= Shar

Re: New revolve joint disconnects existing revolve joint

lucasproko — Fri, 21 Jul 2017 06:03:13 GMT

Hey @sotooleAC4DP,

I'm glad to see you picking up Fusion 360! It looks like you handled most of the modeling steps in that tutorial well, but you missed one step in the video that's integral anytime you're doing assembly modeling.

Anytime a new part is created in Fusion, the part is completely free to move (translate, or rotate) in any direction. This is why whenever you create a new component or body, you're able to click and drag it across the screen. Adding joints is the way to reduce the number of ways your components can move. However, if you create a joint between two components that are both free to move in any direction, then even though the two parts are joined to each other, they'll still be able to move in any direction together. Thus, the step you're missing in your file is grounding one of your components. At 20:57 in the video you linked, it suggests you ground the dovetail base which then means the dovetail base will no longer be able to move in any direction. Then, if you start adding joints between all the other components and the dovetail base, the other components will only be allowed to move relative to the dovetail base in the direction the joints permit. For example, a rigid joint allows zero movement, whereas a slider joint allows for translation in one direction, but rotation in none.

tl;dr - ground the dovetail base!

Best of luck getting to know Fusion! The Fusion 360 YouTube Channel has a log of great content for learning certain features, and feel free to post in this forum when you run into issues you're not able to find the solutions to online.

Re: New revolve joint disconnects existing revolve joint

sotooleAC4DP — Fri, 21 Jul 2017 20:48:16 GMT

Thanks for looking at this and trying to help! I did ground the
dovetail base, and can see a little red pin on that component.

The joints still declare conflict when I add the 2nd revolve joint
that connects the handle to the 2nd slider.

No idea what I'm doing wrong still.

Can you take another look and confirm that the base is indeed
grounded? If it is, then what do you think the problem is?

MANY thanks!
-=shar

Re: New revolve joint disconnects existing revolve joint

lucasproko — Fri, 21 Jul 2017 21:27:10 GMT

Hey @sotooleAC4DP,

What was going on was that your two dovetail sliders had slightly different Z heights because the two dovetail channels you extruded through the base were dimensioned differently. If you ensure Sketch 2 and Sketch 3 are correct, then you should be able to get the rest of the model to work. I recorded a little screencast of me thinking through the problem that you can follow below for more help.

Let me know if you have any other questions!

Re: New revolve joint disconnects existing revolve joint

TrippyLighting — Sun, 23 Jul 2017 13:15:50 GMT

The tutorial you are following is full of bad practices! My eyes are hurting just looking at it.

I am even more surprised that @al.whatmough who is directly involved in Fusion 360 development thinks it's a great tutorial.

1. The tutorial does not follow Fusion 360 R.U.L.E.#1 and with this simple design there is no need to turn a body into a component. He should have started with making a component and ensure it's activated.

2. He does not fully constrain and dimension his sketches, which from a mechanical engineering standpoint is totally unacceptable.

3. Copy/pasting a sketch to create identical geometry without parametrically linking it to the original sketch is also a bad idea. In fact he could have easily created all of the dovetail slots and sliders from a single sketch. Copying sketches that are not fully constrained and then pasting them int o a new sketch and not properly constraining them there either is unforgivable.

4. When he creates the sketch for the handle he states he wants to create tangential lines but then fails to notice that bot the top and bottom line joined to the circle with a coincident constraint but not also an tangential constraint.

5. Later on he states that the circus need tube trimmed, which is entirely unnecessary.

6. the spline he's drawing has way to many points for that simple geometry.

7. By ny means, components should be assembled no all at the end of the design, but as you go.

8. Applying chamfers and fillet in sketches is a solid modeling no-no.

9. Creating a modeled thread on an already chamfered cylinder will not create the proper thread start and will throw you for a loop if you want to 3D print a design. You'll have to apply the chamfer after the applying the thread.

10. He grounds the base before starting the assembly a the end o the video. A component can and should grounded right at the point of creation so very early on in the timeline. Grounding ties the component origin and the design origin together, so a component can be grounded without any geometry it!

While @lucasproko's tips might make your design functional, when going through the timeline I see potential for a number of improvements.If you're interested I can create a screencast of how I'd build this piece.

Re: New revolve joint disconnects existing revolve joint

sotooleAC4DP — Sun, 30 Jul 2017 01:31:16 GMT

Thanks!

I'm messing with it now and will let you know if I hit another wall.

Really appreciate you taking time to help me out.
-=shar

Re: New revolve joint disconnects existing revolve joint

sotooleAC4DP — Sun, 30 Jul 2017 01:31:46 GMT

Thank you!!

Much appreciated!

-=shar