In this article, a DIY master will tell us how to make a CNC cutter/engraver from old DVD drives and a 250 mW laser.
The master has already made a similar device before, but given the materials used and lack of experience, the assembly was not very successful …
This version, in addition to the above, uses parts printed on a 3D printer in the assembly, and this all together gave an excellent result.
Let's see how this machine works.
-Two stepper motor driver modules A4988 or GRBL controller;
-Laser 250 mW with adjustable lens; < br> -Power supply 12V, 2A, minimum;
-IRFZ44N N-CHANNEL MOSFET; -10 kOhm resistor; -47 Ohm resistor; -Voltage stabilizer LM7805 (with heatsink); – PCB board; -Pin headers; -2.5 mm JST XH-Style; -2-pin plug connector; -1000uF 16V capacitor; -Small neodymium magnets; -2-pin plug in screw terminal block; -Zips (100mm); – Super glue; -6x M3x12 screws; -8x M2x5 screws; -Glasses for laser protection; -3D-printer; -Wires; -Screwdriver; -Multimeter; -Heat shrink tube; -Drill; -ABS thread; -Digital micrometer; Step one: printing parts
To assemble the machine, you need some printed parts.
All parts are printed from ABS material.
Layer height: 0.2 mm
Infill: & lt; 25%
Print details can be downloaded here.
Step Two: Prepare the DVD Drive Mechanism
The machine requires two DVD drive mechanisms, one for the X-axis and one for the Y-axis.
Using a small Phillips screwdriver, the wizard unscrewed all the screws and disconnected the stepper motor, rails and pusher.
Stepper motors are 4-pin bipolar stepper motors.
The small size and low cost of a DVD motor means it can't be used expect high precision. This function is provided by the lead screw.
These motors are usually 20 or 24 rpm.
The procedure for calculating the resolution of a CD drive stepper motor is as follows:
To measure the resolution of the stepper motor of the CD/DVD drive, the master used a digital micrometer. The distance along the screw was measured. The total screw length was found to be 51.56 mm using a micrometer. Next, you need to determine the pitch value, which is the distance between two adjacent threads. At this distance, 12 strands were counted. Pitch = distance between adjacent threads = (total length/number of threads = 51.56 mm)/12 = 4.29 mm/rev. The step angle is 18 degrees, which corresponds to 20 steps per revolution. Now that all the necessary information is available, the resolution of the stepper motor can be calculated: Resolution = (distance between adjacent threads)/(N steps/revolution) = (4.29 mm/revolution)/(20 steps/revolution). ) = 0.214 mm/step. This is 3 times better than the required resolution, which is 0.68 mm/step.
Step three: assembly (mechanical part)
Then the master starts assembling the machine.
First he assembles the carriage. A spring is installed to maintain tension between the guide and the lead screw.
Then he assembles the guide for the Y axis.
Before attaching the carriage to the desktop, the master glued four neodymium magnets … These magnets will hold the workpiece in place.
Next, you need to assemble the X-axis.
Using superglue and a screw, the master attached the holder to the case laser.
Then I installed and fixed the stepper motor. Assembled the carriage. The carriage must move freely along the guides (smooth rods). I installed the side racks of the frame.
He used an old USB cable to connect the stepper motors. This cable has 4 conductors and is flexible.
Use a multimeter to ring the motors and identify 2 coils, coil A and coil B. It uses heat shrink tubing for insulation.
Now it remains to completely assemble the machine, connecting its two axes.
Step four : electronics
GRBL has digital and analog pins for Arduino.
The “Step” pin for the X and Y axes is connected to digital pins 2 and 3, respectively. The Dir pin for the X and Y axes is connected to digital pins 5 and 6, respectively. D11 is responsible for turning on the laser. The Arduino is powered via a USB cable. A4988 drivers via external power supply. Common grounding. VDD A4988 connects to 5V Arduino.
The laser that the master used in this assembly operates from 5 V and has a separate power system. For a constant 5V supply from an external power source, an LM7805 voltage stabilizer is used. The stabilizer must be installed on the radiator.
N-CHANNEL MOSFET IRFZ44N acts as an electronic switch when receiving a digital high signal from pin D11 of the Arduino.
Microstep resolution MS0 MS1 MS2.
Low Low Low Full step.
High Low Low Half step.
Low High Low Quarter step.
High High Low Eighth step.
High High High Sixteenth step. < br>The 3 pins (MS1, MS2 and MS3) are designed to select one of the five steps, according to the table above. These contacts have internal pull-up resistors. If left disabled, the board will operate in full step mode. The wizard used a 16th step configuration for smooth movement.
After installation screws the boards to the machine frame.
After installation need to adjust the stepper driver current.
Step five: laser
The laser that the master used is a focusable laser module 200- 250mW 650nm. The outer metal casing acts as a heat sink for the laser diode. It has a focusable lens for adjusting the laser point.
The laser is installed in a special holder.
Step six: programming
Before using the machine, you must install the library code and configure the device. < br> Download GRBL.
Extract the grbl-master folder to your desktop, it is located in the master.zip file
Start the Arduino IDE
From the app bar menu choose: Sketch – & gt; #include Library – & gt; Add Library from file.ZIP
Select the grbl folder which can be found inside the grlb-master folder.
The library is now installed. To test, open the example called “grbl upload” and upload it to your Arduino board.
Step seven: software for sending G-CODE
You also need software for sending G- CNC code. The wizard uses LASER GRBL.
You can download the program here.
LaserGRBL checks for COM ports available on the device. The list of ports allows you to select the COM port to which the control board is connected.
You need to select the correct baud rate for connection according to the device firmware configuration (default 115200).
To view the settings, you need to enter $$ and press Enter after connecting to Grbl. Grbl should respond with a list of the current system settings, as shown in the example below. All these settings are permanent and stored in memory. If you turn off the power, they will be loaded back the next time you turn on the Arduino.
Step Eight: System Setup
$ 0 = 10 (step pulse, usec) $ 1 = 25 (step idle delay, msec) $ 2 = 0 (step port invert mask & # 58; 00000000) $ 3 = 6 (dir port invert mask & # 58; 00000110) $ 4 = 0 (step enable invert, bool) $ 5 = 0 (limit pins invert, bool) $ 6 = 0 (probe pin invert, bool) $ 10 = 3 (status report mask & # 58; 00000011) $ 11 = 0.020 (junction deviation, mm) $ 12 = 0.002 ( arc tolerance, mm) $ 13 = 0 (report inches, bool) $ 20 = 0 (soft limits, bool) $ 21 = 0 (hard limits, bool) $ 22 = 0 (homing cycle, bool) $ 23 = 1 (homing dir invert mask & # 58; 00000001) $ 24 = 50.000 (homing feed, mm/min) $ 25 = 635.000 (homing seek, mm/min) $ 26 = 250 (homing debounce, msec) $ 27 = 1.000 (homing pull-off, mm) $ 100 = 314.961 ( x, step/mm) $ 101 = 314.961 (y, step/mm) $ 102 = 314.961 (z, step/mm) $ 110 = 635.000 (x max rate, mm/min) $ 111 = 635.000 (y max rate, mm/min) $ 112 = 635.000 (z max rate, mm/min) $ 120 = 50.000 (x accel, mm/sec ^ 2) 121 = 50.000 (y accel, mm/sec ^ 2) $ 122 = 50.000 (z accel, mm/sec ^ 2 ) $ 130 = 225.000 (x max travel, mm) $ 131 = 125.000 (y max travel, mm) $ 132 = 170.000 (z max travel, mm)
This is the most difficult part of the project.
-Adjust the laser beam to the smallest possible point on the workpiece. This is the hardest part and takes time and patience.
-Configuring GRBL parameters for $ 100, 101, 130 and 131.
-The wizard has the following settings for GRBL:
$ 100 = 110.000 $ 101 = 110.000 $ 130 = 40.000 $ 131 = 40.000
For the test, the master engraves a square with sides of 40 mm. If the settings are correct, the lines should be straight, straight and of the same thickness.
-Connection control: here you can select the serial port and the corresponding baud rate for connection according to the grbl firmware configuration.
-File control: shows loaded file name and progress of the engraving process. The green Play button will launch the program.
-Manual commands: you can enter any line of the G-code and press “enter”. Commands will be queued.
-Command Log and Command Return Codes: Displays queued commands, their execution status and errors.
-Adjust Move Mode: Allows you to manually position the laser. The left vertical slider controls the speed of movement, the right slider controls the step size.
– Engraving Preview: This area displays a preview of the final work. During engraving, a small blue cross will show the current laser position while working.
-Grbl reset/hoinging/unlock: these buttons send soft-reset, hoinging and unlock commands to the grbl board. Some custom buttons can be added to the right of the unlock button.
-Feed Hold and Resume: These buttons can pause and resume a program by sending a Feed Hold or Resume command to the grbl board.
-Row Count and Time Projection: LaserGRBL can estimate program execution time based on actual speed and progress.
-Control status override: Shows and modifies actual speed and power override. Overrides is a new grbl v1.1 feature that is not supported in the older version.
Step nine: engraving
Raster import allows any type of image to be loaded into LaserGRBL and converted to GCode without the need for other software. LaserGRBL supports photos, pictures, pencil drawings, logos, icons, etc.
This function can be called from the File, Open File menu by choosing an image such as jpg, png or bmp.
Engraving settings are different for all materials … It is necessary to determine the speed of engraving and the quality of the lines.
A 250mW laser can also cut thin paper, but the speed must be very low because e. no more than 15 mm/min, and the laser beam must be correctly adjusted.
You can also make templates from vinyl. The speed varies depending on the color of the vinyl. Black colors are easier to work with than light ones.
Everything is ready. Thanks to the master for the instructions, and for those who wish to repeat the assembly, I advise you to go to the page of the original article and read the article in more detail and the comments below it