next topic »

[on:]

I am working on a conversion to use my sherline desktop CNC mill as a 3d printer.
I have an arduino mega rev2 board waiting for use and I am looking to design a dual temp monitoring pid system for controlling the hot end as well as the heated bed independent of the controller software. I have a 2x16 LCD and a rotary encoder as well as a good selection of momentary buttons for the user interface, I can get mosfets and thermisters as well as the heating elements or power resistors locally. I just have no clue on the code. Any help on this project would be much appreciated.

thanks.
Kevin G.

[Reply #1 on:]

I think most of this has been done already, take a peek at http://reprapbook.appspot.com/  or anything else google gives with : Arduino 3D printer.

[Reply #2 on:]

There is a pretty nice PID library already for the arduino.
http://playground.arduino.cc/Code/PIDLibrary
http://brettbeauregard.com/blog/2011/04/improving-the-beginners-pid-introduction/

 If you don't need to measure temps over 300F, the LM34/35 monolithic temp sensors can save a lot of work. They are linear and will likely interface to the arduino with no additional hardware.
http://www.ti.com/lit/an/snoa748b/snoa748b.pdf
I don't know if they meet your requirements but, if you can use them, they save a lot of work. They can even be used with cheap DMMs for a direct temp readout.

Think about what you need the arduino to do.
1. Measure temp. (trivial)
2. Control resistive based heater relative to sensor feedback. (I assume)

I once did the same with analog hardware components to control a desktop mini fridge. If I had known about arduino then, it would have been a whole lot easier.

You could probably even get by with a simple high low switching setup and get by.

[Reply #3 on:]

I am pretty sure for a 3D printer you will be well advised to use a P, PI or PID control loop to control the temperature of your extrusion head heating element. Probably best to use a sensor that is fast and rugged as it will be right on the extruder if I recall. Possibly use a PT100 type RTD and bring that into some suitable electronics to feed an analogue input on an Arduino.

Try to find out if anybody else has converted such a CNC as yours for use as a 3D printer, as you can learn what difficulties they encountered.
I am sure there will be plenty of good reading to be had on the 3D printer forums to gain more insight.