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How to model timing belt in Fusion360

In this video I’ll show you how to model straight GT2-6 timing belt and how to model continuous belt around two pulleys in a plane.

The centre to centre distance

When modelling a belt around two pulleys we have a few constraints:

  • the pitch circumference of each pulley
  • the pitch of the timing belt

What we need is the ideal distance between the centre of the two pulleys so that the belt fits perfectly. The centre to centre distance is described as

C = \frac{b+\sqrt{b^{2}-32(D-d)^{2}}}{16}

  • C = center to center distance
  • D = diameter of pitch circle of gear 1
  • d = diameter of pitch circle of gear 2
  • b = 4L - 6.28(D+d)
  • L = pitch of timing belt

For Fusion 360 you may find that it is easier to break the large equation into smaller sections like calculating ‘b’ first.

Final thoughts

Should I do a follow up with other kinds of belt? Other designs? Let me know.

News

Have you heard of Crush Ribs?

Crush ribs are a great way to stop tweaking files per-printer and still get that snug fit you need for good mechanisms. Here’s a short video explaining the why, the where from, the how, and more.

Also, here’s a follow up tip about how to make crush ribs draft quick fast.

Did that help you? Did you use it in a design? Let me know so I can share it with everybody.

News

Sixi Robot Gripper Design Adventures

I thought that the hard part would be making the Six robot arm. Turns out making a two finger gripper is also pretty challenging! I would love to see students take on this challenge to make their own gripper. There’s so many ways to tackle the challenge.

Gripper requirements

The gripper must:

  • Attach to the ISO 9409-50-1-M6 hand
  • Have two fingers
  • Weigh under 1kg
  • Be able to pick up at least 1kg and turn it arbitrarily without dropping it
  • Not crush soft objects like grapes, eggs, or empty cans
  • Have a minimum stroke (movement distance) of 30mm.
  • Run at 12v (max 2a) for motor power.
  • Run at 5v (max 500ma) for logic.
  • Have replaceable fingers that can be customized to different tasks

It would be nice if

  • The gripper would use ModBus (RS485) to communicate with the Sixi robot.
  • The gripping strength could be controlled by the robot.
  • The robot could tell the state of the gripper: position, activity right now, etc.

More to follow as this adventure unfolds! Wish us luck.

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