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Showing posts from April, 2015

Rookie mistake with Makercam

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This morning I was in the lab of a digital manufacturing subject and I showed my students how they could do simple designs and turn them into a 2D manufacturing g-code without installing any software in their computers or tablets.

I did show them the terrific OnShape.com online service that I have found very easy to learn and yet very powerful 3D design package. I performed a simple design.

And later I showed how that could be exported as a DXF file and with the help of Inkscape it was written into a SVG file that Makercam.com online CAM software can handle.

I selected metric units (though I would expected MM instead of CM but I guess it is ok for grid size purposes) and I proceeded to show the different machining operations available and how we will be cutting the thing.

So minutes later we have g-code file ready to be loaded into our CNC router equipped with LinuxCNC software. After setting the whole thing up the process started and seemed to be working ok, though I had the impressi…

Getting more data from your PID controller

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Just knowing the steady-state error of your controller may not be enough for you to figure out how well your manual adjustment for your PID gains is working. In order to get a better picture of it you need to gather information while the loop is reacting to an input change. 
However, just sending back information over the serial port while the loop is working may alter the very timing of things within the loop. So what I have done is to delay the monitoring information transfer till the loop reaches the steady state. That means actual position is recorded every millisecond and stored in an array so it is later transmitted once the motion is performed. Thanks to that I can see the system response quite nicely whether the response does have an overshoot or it is dampened properly enough. It really comes in handy when trying to set the P, I and D gains by hand. 
The problem, however is that for doing this you need to have enough RAM memory and Arduino UNO is a bit short of it. What I di…