Understanding relative motion of ball bearing drawer slide joints

[elliekate]

I'm trying to understand my first compound joint: a ball bearing drawer slide imported from McMaster carr. I have a frame and two sliders and I created two rigid groups and grounded the frame. I can animate both sliders through their range of motion, but I can't get the dependency right. I also can't drag slide the compound joint. When I try to manually drive the joint, I move the whole assembly.

I would love any pointers to help me figure out what I'm doing wrong. The attached file "test" is a working example I found on the forums, my attempt is also included.

[wmhazzard · Accepted solution]

Grounding the frame component instead of the frame assembly should give you the results that you are looking for. Not sure why grounding the assembly does not work. 

[laughingcreek]

grounding the frame assembly doesn't work because the components within are still free to move.  if you turn on the origin of each component you will see the origin for the frame assemble doesn't move, but the origin for the subcomponents do. 

[TrippyLighting]

Rigid Group Joints constrain the origins of the involved components in place.

The frame component group (assembly) contains 5 origins but only 4 are involved in the rigid group. That 5th origin belongs to the farm assembly itself. You can edit the rigid group and add it.

Then you could actually ground the frame component. That would work fine if this was you top level design assembly, but as you are going to insert it into another assembly I recommend not grounding it. Grounding is only local to that design.

Use  an as-built rigid joint between the frame component and the top/root  level design origin.

Apply that same principle to any other sub-assemblies.

90% of all assembly problems in Fusion  360 can be traced back to users not properly managing the component origins. 

[WHolzwarth]

I have not much experience with F360 animations, therefore I tried it with Inventor.

Can someone show the same movement as in the attached video with F360?

[jhackney1972]

I did a Blog Article and Video on the process of making a ball slide function.  I will admit, I removed the balls.

[elliekate]

super helpful and it all makes sense. I very much appreciate your advice and wisdom.

[elliekate]

I was able to get the joint to work (super awesome!), but I can't sync the drawer with the slides and get the motion right. I can move each drawer's joints individually so I know they are working. If I join both drawer slides into any type of rigid group, the drawer no longer moves. How can I get the drawer to move correctly with the sliders?

[jhackney1972]

The reason you cannot hook both linear bearings to your drawer and still get motion is because the linear bearings are not parallel to each other.  Your drawer sides are parallel but you are using a Rigid Group between the linear bearings and the drawer and it was created before the bearings were positioned parallel to each other.  If I were you, I would remove this Rigid Group, locate the bearings, on each side of the drawer, and fix them with some Joints.  This way you can make sure they are parallel to each other.  Rigid Groups are great IF all components are in the exact right position when they are created, in your case, the linear bearings were not.  Screencast will show you the angle misalignment.

[elliekate]

What an incredible community. This is excellent. I was able to get everything working quickly by using rigid joints to line things up.

[MichaelT_123]

Hi Herr Walter Holzwarth,

Here it is … the file modelling of a drawer slide with an extension, as well as mp4 video files showing animations of two modes of its movement.

The file’s model is configured as ‘synchro’ ; slide joints are 1:1 synchronized.

In the video file, you will find, perhaps more realistic ‘sequeo’ mode of movement.

How can ‘sequeo’ be encoded into the model’s joints?

The users of Fusion360 love challenge, and particularly the Fusitzens of this Forum, don’t they?

 … thus, the denial of the opportunity to find out how, would be on my part … very brutal constrainment of curious minds.

I can’t do that! … so, I will rest the question unanswered.😣

Attached files:

DrowerSlides_mono.png     4K_mono      (  2MB)    https://a360.co/3ftdVMn

DrowerSlides_mono.mp4    4K_mono      ( 17MB)   https://a360.co/3A3soYO

DrowerSlides_arcd.png       4K_stereo     (   4MB)   https://a360.co/3qwA6rd

DrowerSlides_arcd.mp4      4K_stereo      ( 57MB)  https://a360.co/34LeEWT

DrowerSlides_al.mp4          4K_stereo      ( 38MB)   https://a360.co/3GzuUsg

DrowerSlides.f3d                 F360_model  (0.6MB)   https://a360.co/33HL7g8

To be viewed on 4K media devices (monitors, UHD TVs, projectors...) of reasonable performance. For the best experience, use stand-alone media applications (WMP, VLC) and the native resolution 3840x2160 - full screen. The '_arcd' files require an anaglyph red/cyan glasses, while '_al' is for an active shutter glasses 3D hardware (~30 deg viewing angle is recommended) . Download the files over a network, where the cost of doing so is not a concern. The files are to be used for private, non-commercial purposes only.

Grüße

MichaelT

[WHolzwarth]

Excellent job, Michael.
Too much work in my case with AR/VR versions, because one of my eyes is weaker than the other.

My Inventor version used sub-assemblies for the ball sets. I'll try that with your F360 file, as an exercise.

Thanks

Walter

[elliekate]

This is really interesting and helpful. I would love to be able to do this. I can't get joints to move in animation mode. I can do a motion study, but don't know how to make a movie out of that unless I do a screen capture or have windows record the whole application.

Would you be willing to share your approach or point me at what mode you use to solve this.

[MichaelT_123]

Hi Mr EllieKate,

The simulation results included in my last post were generated with the help of the commercial F360 Ultimate together with its engine extension I call MT123. There is significant bulk of software code behind. The extension is not available to the general public.

Regards

MichaelT