CNC Mill Conversion Controller

I'm a senior engineering student working on my design project of converting a custom built CNC machine, from a previous design group, into a 3D Printer. This means I already have stepper motors and controls in place for the basic 3 axes of movement, and it appears it won't be too complicated to add another stepper motor into this existing system for the print head.

I'm looking for the best microcontroller to use to just control the extruder head and printing bed temperatures. So it needs to be able to read values from a couple thermresitors and control the temperature of the heating blocks on them accordingly. Most of the 3D printing specific controllers I've found include stepper controls I won't need. Generic controllers I haven't been able to figure out if they would even work for my purposes. I'm pretty new to these kind of electronics, so any help I can get would be much appreciated. Does anyone have any suggestions or good places to start for how to go about doing this?

Thanks.

Buy an arduino mega, upload a reprap firmware, and in that firmware pins.h file, check or alter locations for step/dir/en pins, and from that arduino header take these to each motor.

For a thermistor its a votage divider with a resistor fixed for pullup to 5v, and thermistor on the gnd side, and the voltage divider output has a 10uF cap on it before it goes into the adc pin. This you can do in air or on a stripboard pcb (or whats the name of that).

For a heater its a low side mosfet, a header pin goes into gate, and mosfet can then be wired directly and mounted on a hefty heatsink, with only wires soldered to its legs.

Thats all the basics requirements, if you want a lcd and sd, those are extras and you can figure them out and wire them separately.

Or, if you want some other electronis, you could use any electronics out there, and draw the step/en/dir signals from the pololu headers, but probably wont be cheaper, nor a cleaner setup, and also you will end up with some of extra unnecessary stuff.

To note, you cannot use a controller "to just control the extruder head", because extruder head is integrated with all other movements, meaning extruder head is a fourth dimension, so x+y+z+extruder(s) all need to come from same controller.

An arduino wired to step/dir/en will give basic cartesian movements like that, and everything will run on it, arduino comms goes directly to computer usb, so that part of whatever control you have now would become obsolete.

But on the other hand, depending on your existing setup, especially if you already use something like emc, you could review the EMC2 folder. This way you integrate the extruder dimension into your existing setup.

So you could either move everything onto an arduino, or else you need to extend the existing setup to integrate the extruder. Perhaps there is more than one way for the last part.

....... since this is a senior design project - what's the minimum you can do and still get the grade? Put another way, how complex does this need to get? You could indeed make it very complex, but I doubt that's what's required. If the budget will stretch to fit a Mega / Ramps combo that's the way to go. No pc boards to lay out, no major code to write. Wire it up, figure out all the calibration for the firmware, calibrate it and print.

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uncle_bob
....... since this is a senior design project - what's the minimum you can do and still get the grade? Put another way, how complex does this need to get? You could indeed make it very complex, but I doubt that's what's required. If the budget will stretch to fit a Mega / Ramps combo that's the way to go. No pc boards to lay out, no major code to write. Wire it up, figure out all the calibration for the firmware, calibrate it and print.

Something that at least looks like a good faith effort to build a working 3D printer should probably pass me haha. I am hoping for something that actually is fully functional, but I lost the group member lottery and am pretty much doing the majority of the work myself so quickest and simplest is my goal right now. Only $600 budget at the moment, though we may be asking for donations from some companies. Considering most of the machine is already built, and it looks like I can get a RAMPs kit for around a 100 bucks, I can probably squeeze this into the budget. I was thinking I could do it cheaper with a board without the stepper motors, but if that's going to add a great deal of complexity screw it.

I'd go for a Ramps / Mega combo for the electronics. That cuts out pc board layout and a lot of firmware work. It scales the project back to the point that you might actually be able to get it done. A full set of steppers costs around $75 if they are normal NEMA17 motors. The Mega can be a $15 clone from eBay, they all seem to work ok. The Ramps board it's self is about the same. You can find the Ramps in combination with the stepper drivers for about $40 or so.

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Of course for $600 you could by a full blown printer kit and build it ....then you are sure to have a woking gizmo when you are done.

Edited 1 time(s). Last edit at 11/24/2013 11:01AM by uncle_bob.