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.


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.

Discuss this post in the forums.


How to draw a rectangle in Gcode

So you’ve played with the Makelangelo‘s generated Gcode and now you want to experiment on your own. Cool! Here’s a simple rectangle to get you started.

Now let’s give some values to these parameters:


My method is to lift the pen, drive to a corner, put the pen down, and then trace the rectangle. That means going to five points because we have to come back to the start.

G0 Z90; # pen up
G0 X-10 Y20;  # p1 
G0 Z40; # pen down 
G0 X30 Y20;  # p2
G0 X30 Y-40;  # p3 
G0 X-10 Y-40;  # p4 
G0 X-10 Y20;  # p1 again
G0 Z90; # pen up

And voila! I’ve deliberately done this with the origin away from the center so the numbers are more obvious. I hope you see that in a cartesian system the origin could be anywhere. For example, if it were below and to the left of P4 all the X and Y values would be positive.