Miscellaneous

3D Printed Thrust Bearing

2012-04-04 Dan

http://www.thingiverse.com/derivative:25706

When two objects are moving together they can have two kinds of contact: sliding or rolling.

  • Sliding produces a lot of friction which leads to extra work, heat, wear, and damage. Sometimes this can be overcome by using two different types of materials: brass slides easily over steel, but steel doesn’t slide well over steel.
  • Rolling is smooth and (nearly) frictionless. Bearings are like wheels on a car: they turn as much sliding friction into rolling friction as possible. Did you know there are bearings inside most of your moving household appliances?

      What makes Thrust Bearings special

      Thrust bearings work like normal bearings except they can take more axial load. (force in the direction the center axis is pointing). Put two of them back to back and you get a Slew Ring, a bearing that can take a great deal of force every which way.

Uncategorized

Drawbot Experimental Branch with Look Ahead Ring Buffer

2012-03-31 Dan

I’ve created a new experimental branch so as not to ruin the latest working version. It has two big changes.

Feed Rates
The old feed rates were units/s.  I’ve adjusted the feed rate setting and display to be in units/minute – call G21 and it will display mm/min, call G20 and it will display in/min. This makes more sense because most machines are rated in in/min. I didn’t think 2cm/s was fast until I converted it and realized I was running almost 50in/min. Not bad for a hobbyist!

Look-ahead Optimization
Let’s say the machine has to draw 5 lines in a row, all in the same direction. In the past the software insisted that the machine come a complete stop between each line segment because the software had no idea what was coming next.
In the latest version the software stores the next several lines in a ring buffer and plans ahead: if the lines are all in the same direction it doesn’t slow down. If they are on a slight angle it slows a little. Anything 90 degrees or more is an automatic full stop.

A generous user on http://reddit.com/r/singleline/ created a new “Hello World” vector that I’ve been using to test and the results are fantastic! Using the old method it took 11 minutes to draw. In the new method it takes only two!

At this point I feel the software is “good enough” and I’m going to focus on pen up/down.

Uncategorized

How to Drive the Drawbot Manually

2012-03-26 Dan

Draw > Start Driving

Click+drag in the Preview window

The black line is your speed and direction.  The red circle is your top speed.  The green circle is the dead zone.  If the black line is inside the dead zone, the robot won’t move.  If the black line is on the edge of the dead zone then it will move very slowly.  In the picture above, it is moving at about half speed down and to the right.