topic Re: Selecting axis for pin-slot joints - what is the logic? in Fusion Design, Validate & Document Forum

Selecting axis for pin-slot joints - what is the logic?

lure23 — Sun, 02 Jun 2019 18:33:22 GMT

The larger designI'm doing a design with a swivel for the arm. Had difficulty selecting the right kind of joint (red arrow).

The arm is already limited in its horizontal movement, and tied to the driving wheel in its other end. I then want to limit its freedom as if it comes out of the "box" in a certain slot.

Z axis seems like the natural choicePicked "pin-slot" joint for this, with a custom slide axis (the edge of the arm). And it was stuck...

Then suppressed some of the other joints to see what had become of this. It seems I need to pick the "Y Axis" for this case, in order to have the arm swivel around what seems to be as the Z axis.

Would someone share the logic behind this axis selection?

Autodesk help says "The component can rotate about an axis and translate about a different axis."

In case Autodesk personnel think this behavior is faulty, here is a link to the design.

Re: Selecting axis for pin-slot joints - what is the logic?

davebYYPCU — Sun, 02 Jun 2019 19:24:30 GMT

Not accessed the file yet.

Does the hooked bar remain parallel with the block, with the wheel in It?

If so it’s just a Slider.

You say it is tied the the wheel, then you can’t swivle it - without taking the wheel with it. If you want to swivel at that face position, and slide in the document x direction, then the hooked arm would be a pin slot, at the face of the block, with out any other joints. (pic 2)

Document origins are not nesessarily aligned the same as Joint Origin directions, Joint z axis is always penetrating the face of the Joint Disc. Your case has the document Y aligned with Joint Z, when you zoom in to the disc, the flat centre edge is always Joint X, Joint Y is relative to the other two, refer to Joint disc axis directions in the Joint dialogue box.

Might help....

Re: Selecting axis for pin-slot joints - what is the logic?

chrisplyler — Mon, 03 Jun 2019 13:29:25 GMT

Imagine that it was just a Revolve joint (disregard the sliding motion in your head for now). You would place the coin on the SIDE of the bar, right? As if there were a pivot point running horizontally through the bar, right?

Re: Selecting axis for pin-slot joints - what is the logic?

laughingcreek — Mon, 03 Jun 2019 15:42:48 GMT

I also find this confusion sometimes. the axis of rotation isn't referring to the model or component ordinate system, but rather to the relation ship of the joint location coins. The Z axis is referring to the axis passing thru the center of the coins, regardless of their orientation in the model.