All mechanical and thermal systems are controlled by an arduino mega 2560 which connects, as usual in the world of arduino, to a "shield" or expansion board. The most typical is known as "RAMPS", an acronym for "Reprap Arduino Mega Pololu Shield". It's an expansion board with Sockets for the connection of several driver or stepper motor controllers, the most widely used being the better known as "pololu" A4988. This plate also contains some mosfet outputs to control the current hot bed and the "hotend" of the extruder as well as inputs for Thermistors that will control the temperature of these elements. This provided also with two Resettable fuse that cut the current in case of overcurrent. It contains all necessary connectors for the various elements of the system.
Thanks to the Rep-Rap movement, today anyone with a bit of skill and for little money can enjoy 3D printing. The ease to create all kinds of parts opens new horizons for those who love innovation.
At the beginning of 2014, since the purchase of a 3D printer kit was finally affordable I decided to plunge into this exciting world. I purchased a kit with all the parts (some made with other similar printer) needed to assemble my own 3D printer, model Prusa-i3 and enjoy, finally, of this technology. Then I will discuss briefly each of the parts
3D printing technology is based on depositing some amount of plastic cast in certain positions (x, y, z) of the points that form the object to create.So they are needed 3 axes that allow us to move the print head to the necessary coordinates, but to simplify the construction details what is done is to move the head in X, Z axes and, on the other hand moving the object in the Y direction. Thus, the mechanical structure is formed by:
Y-axis: Two threaded M10 bars and four M8 United by 4 pieces printed in ABS and secured with washers and nuts form a basis on which are fixed two steel smooth bars where slip through thrust bearings the platform on which are printed objects, which will be equipped with a heating surface called hot bed whose mission is to keep printing surface at certain temperature, usually a mirror or glass, since cold most of the plastics that are used are not fixed to the base. This platform is moved in direction of the axis, i.e. forward to backwards, driven by a belt by a NEMA17 stepper motor.
Z axis: It consists of two vertical smooth bars on which slides up and down the X axis together with the extruder or print head. These guides are usually fixed on a vertical frame which can be of methacrylate, aluminium or other materials and providing strength to the structure. The movement of this axis must have accuracy of the order of the tenth of mm even though it does not require high speeds, why is he actuated by two vertical screws rotating trailers through a flexible union to two NEMA17 motors.
X axis: Is formed by two horizontal guides, which moves the print head in the transverse direction. It is powered by a motor and a belt.
Extruder - E Axis: creeps strand of plastic that will be cast using a toothed shaft which is moved through reduction gears for a last step motor. From the logical point of view the extruder is one axis more.
As I've said before, the extruder, motor-powered push strand of plastic that will be cast, what happens in the piece known as "hotend". Thanks to a ceramic resistor heater, usually of 40W, is accomplished, very localised at the end of the hotend the necessary temperature to melt the plastic (220 ° C - 240 ° C for ABS), that flows being extruded through the "nozzle" through a hole of 0.3 - 0.5 mm generating a uniform bead of melted material. Thanks to a thermistor placed next to the heater the firmware can precisely control the working temperature.
The program that runs on the arduino ATmega2560 and through the Ramps shield controls all movements of the printer as well as temperatures, is what we call firmware and there are several options. I use Marlin but I also know grbl, perhaps more oriented for the control of CNC machining systems. This software uses the gcode language which is a type of numerical control code in which are coded entries that must be the print head displacements, as well as the amount of plastic to be deposited at each site. The gcode language instructions are received from a PC via USB connection, although it is possible to connect a LCD module with SD card reader where we can store the gcode and allow the printer to operate without connection to a PC.
It is common to use a computer to control and monitor the work of the printer. In my case I use the software Repetier Host that includes the "Slicer" tool to generate the gcode commands that govern movements of the printer.
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