CNC Plotter
Introduction: CNC Plotter
This Instructable explains how to build a CNC plotter, using two NEMA17 stepping motors, a timing belt, a few idler pulleys, an Arduino UNO R3 microcontroller, and some printed PLA parts.
The paper size is A4 ... longer pipes are required for A3
Resolution is 80 steps per millimeter.
Unlike some plotters, in which the arm moves back and forth, the footprint for this plotter is constant.
A mounting base is not required as the plotter is freestanding. Screw-holes, however, have been provided should you wish to add a base.
The design is such that a laser print-head (future project) can be substituted for the pen-lift shown in photo 1. The current design is used for creating watercolor outlines.
The detachable pen-lift is described in my instructable https://www.instructables.com/CNC-Pen-Lift-1/
The plotter runs a modified version of “GRBL- Servo” and works with “UGS” (Universal G-Code Sender).
The timing-belt path is unusual in that the belt passes through the inside of the 12/10 diameter metal arms. This accounts for its simplistic look. 16
The belt is tensioned by moving the end-brackets outwards.
Construction details, including all STL files, are provided … … all you need is a screw-driver, a pair of side-cutters, and a hacksaw.
Excluding the CNC-Pen-Lift, the estimated cost of this plotter is less than $100
Images
* Photo 1 shows the assembled plotter
* Photo 2 shows a sample plot
* The video shows the plotter in action
Supplies
The following parts were purchased from https://www.aliexpress.com/
* 1 only Arduino UNO R3 with USB cable
* 2 only Big Easy Driver motor controllers
* 2 only 12 volt 30 ohm 17HS3430 NEMA17 stepper motors
* 2 only NEMA17 stepper brackets
* 1 only 3m length GT2 6mm timing belt
* 2 only GT2-20 6mm timing pulleys with 5mm bore
* 3 only GT2 6mm toothless idler pulleys with 4mm bore
* 4 only GT2-20 6mm toothed idler pulleys with 4mm bore
* 6 only LM12UU linear bearings
The following parts were obtained locally:
* 2 only 1m lengths 12/10mm (O.D./I.D.) metal tube [1]
* 8 only M3 x 5mm bolts
* 4 only M3 x 10mm bolts
* 4 only M3 x 20mm bolts
* 4 only M3 x 35mm bolts
* 4 only M3 nuts
* 15 only M4 x 30mm bolts
* 15 only M4 nuts
* 2 only cable ties
In addition to the above parts your will need to make the pen-lift described in my instructable https://www.instructables.com/CNC-Pen-Lift-1/
You will also need to print the PLA parts described further on
Excluding the CNC-Pen-Lift, the estimated cost of this plotter is less than $100
Notes
[1]
I used 12mm O.D. aluminium tube
Aluminium tube was all that was available at the time … (stainless steel would be better)
Step 1: Circuit
The wiring diagram for this plotter is shown in photo 1.
IMPORTANT - the Big Easy Driver modules expect the wires from each motor coil to be adjacent. Check that the motor wires don't alternate ... if so swap the two center wires.
Adjusting the motor current(s)
* Attach a 12 volt 30 ohm NEMA17 stepping motor to a Big Easy Driver module and apply 12 volts DC to the motor assembly. [1]
* Now adjust the small potentiometer on the Big Easy Driver module for a current reading of 0.4 amps
* Repeat this process for the remaining motor and Big Easy Driver module.
* Disconnect the power.
Substitute motors
The plotter also works with 6 volt 8 ohm stepping motors in which case a 6 volt power supply should be used and the motor currents set to 0.6 amps (600mA).
Notes
[1]
I’m using a CPS-3205 adjustable power supply which has on-board metering. Any 12 volt power supply/battery capable of 2amps will work equally well … just insert a current meter in series when adjusting the current. 16