Category: Laser Cutter

StippleGen2

Today I have been trying out StippleGen2 by Evil Mad Scientist. Stippling is when you create an image from little dots of the same color but with different sizes and with different density. StippleGen2 is built in Processing and uses an algorithm written by Adrian Secord. To try it out I used this classic picture of Louis Armstrong playing the trumpet. Once you load the picture you want to stipple the StippleGen2 starts crunching numbers and the algorithm continues to refine the result by applying the algorithm over and over again and the resulting image gets better and better.

After letting StippleGen2 crunch the numbers for a while I imported the resulting vector graphic file into inkscape and generated the G-code so that I could use my laser cutter to cut the image into a black paper. 2 hours and 23 minutes later I had a 20×20 cm piece of paper with about a 1000 holes in it and it looks awesome! Would be perfect for a lamp shade or just nice to put up in a window and let the sun shine through. I can highly recommend StippleGen2 it’s super easy and a lot of fun.

What can you cut with a 300mW DIY laser cutter?

I built this laser cutter after being inspired by this laser cutter and the design is almos identical, there for I will not go into details about my build but will instead focus on what you can do with it.

Since the diode (LPC-826) I have used is from a DVD burner and have an output power of 300-400 mW, it can’t be considered very powerful when it comes to cutting lasers. It should not be confused with a CO2 laser which have an output power of 50W, which is the type of laser that is normally is used in professional laser cutters.

The materials I have tried so far are:

  • Adhesive plastic (stickers) – Cuts right through
  • Art Foam/EVA foam – Cuts right through
  • Wood – It burns the wood but does not cut. Can be used for engraving.
  • Paper – Black copy paper can easily be cut but thicker paper does not work. White paper does not work.
  • ABS Plastic – The surface melts so it is possible to engrave but it can’t be cut.
  • Plexiglass – Not a mark.
  • Plasticard – The thinnest sheet I tried could be cut at low speed but only after having been painted black.

Adhesive plastic

This is what I find by far the most useful application for this laser cutter. So far it has been able to cut through any type and color of the adhesive plastic that I have tried. It is quite easy to cut stencils or stickers. I often use it for cutting custom drilling and cutting templates for other projects. If you want to know how to use photoshop to create stencils from pictures stencil revolution has a good tutorial.

I did some experimentation with masking off parts of a steel plate with laser cut stencils and then I created rust by using Hydrochloric acid and Hydrogen peroxide. It worked pretty well however I need to work some more on the proportions between the Hydrochloric acid and the Hydrogen peroxide to get a nice rust coating on the unmasked metall. A word of caution, do NOT do this inside. I did and now I have a nice rust coat on every un protected piece of metal in my lab. Also wear gloves and eye protection. If you want more details about on the method I used to create these look in the comments for the video.

Art Foam/EVA foam

I have not done much cutting in EVA foam, mainly because I have not had any use for it. But if you are building small models and need laser cut parts this laser will get the job done for you.

Wood

Wood can be burnt but not cut. So if you are the woodworking type you might have a use for it. Sometimes I have seen that the laser does not start to burn instantly and that it takes a darker part of wood for the laser to get started, once it has started to smoke it goes on burning from that point.

ABS Plastic

ABS_plastic

When it comes to hard plastics like ABS it can melt the surface but not burn through. So just like it is with wood it is possible to engrave on ABS. The picture shows a quick test and is not the most beautiful thing I have done but it gives you an idea what to expect.

Hardware

If you are still interested in the hardware here is a quick rundown of the parts.

Mechanical

The whole frame is made from wood and the sliding tray slides on drawer sliders. Both x and y-axis are propelled by an M6 threaded rod.

The coupling between the frame and threaded rod consists of a M6 extension nut that I have incased in Polymorph plastic, Polymorph plastic softens enough to be molded by hand if you put it into boiling water and after it cools down it feels as hard as vinyl, very handy for motor mounts and this type of applications.

Motors

Both motors are NEMA17 stepper motors, 200 steps per revolution.

Laser

The laser is a MITSUBISHI/658nm-660nm 300-400mw CW Red Laser Diode/LPC-826 that I bought from eBay. It is mounted in a standard 5.6mm Laser Diode housing with a round heat sink. It is powered by a LM2596S based power module with built in current limitation. This way you will not risk feeding the laser to much power.

The LCP-826 diode should be run at an operation current <400mA and operation voltage <2.2V. To achieve this I started by connecting the 12V I use to drive the stepper motors to the IN on the DC-DC step down module. Then I connected a multimeter in Voltage measuring mode to the output on the board and adjusted the potentiometer closest to the input terminal on the card until I had 2.2V on the output. After I hade the desired voltage I changed the multimeter setting to Ampere measuring mode, remember to move the cable, and then adjusted the potentiometer closest to the output until I had a current output of 400mA. The middle potentiometer controls one of the diodes on the charger circuit and you can adjust it to set at what current the diod should light up.

LM2596S DC-DC Step-Down power supply. Picture made by coachlam.

LM2596S DC-DC Step-Down power supply. Picture made by coachlam.

 

The laser is turned on and off from the spindel on/off pin of the Arduino nano. Spindel on/off is connected to an Logic level Mosfet which enables me to control a 12V signal from the Arduino.

Remember that you should always wear laser eye protection when using this kind of lasers. When I started to build this laser cutter I decided to buy a pair of laser protection glasses. After doing some reading I decided on a pair from dragonlasers.com called LSG08. The LSG08 are designed to block light at the frequency 190-450nm and 598-752nm which covers this laser. I am no expert but from what I found after some reading I wanted a pair that was OD5-6 certified. OD stands for optical density and each step on the scale is a factor of ten. So OD1 will reduce the amount of light of a specific frequency by 10, OD2 would reduce it by 100 etc. Here is a diagram of the LSG08 light blocking properties.

LSG08 OD diagram

I am not saying that the really cheap glasses that you can buy of e-bay for around won’t work but I didn’t want to take that chance. The ones I got from dragon lasers does seem to work very well since I can still see! What is important is that the laser protection glasses are designed to block the frequency of your laser. If you are using a infrared laser then this is extremely important since the light is not visible to the naked eye.

Electronics

The stepper motors are controlled by two Easy driver stepper motor drivers. The Easy drivers are connected to an Arduino nano which is running grbl 0.8. They are connected as described on the grbl wiki page. Power to the laser is turned on and off using a logic level mosfet.

Limit switches

I have connected two micro switches to both sides of the x-y table, the limit switches as they are called serve two purposes.
1. Stop all movement if the end of the x-y table is reached.
2. Serve as indicators for the homing sequence.
The homing sequence is used when starting up the cutter to find the starting point every time you start. When you initiate the homing sequence the machine will run both motors until both switches in the negative directions are triggered. Then the motors will reverse direction and run slowly until the switch is released and that is the starting point. The homing sequence is initiated by sending the command $H to the controller and most G-code sender applications has a button to initiate the homing sequence.
One very very important thing to have in mind when using grbl as a base for a laser engraver is that you have no z-axis. However the homing mechanism used in grbl expects the limit switches for all three axis to trigger, there for you have to wire a pushbutton to serve as your z-axis during the homing sequence. If you don’t have the faked z-axis limit switch, which you manually push, the homing sequence will never finish. An option to get around this would be to wire one of the x or y axis limit switches to the z-axis pin so that it serves as switch for both.
The limit switches are simple normally open micro switches that you wire from ground to pin 9 (x), 10 (y) and 11 (z) on the Arduino.

Software

For software I use UniversalGcodeSender-v1.0.6 to send the gcode to the Arduino that has been loaded with grbl 0.8. To create the gcode from an image I use Inkscape together with the LaserEngraver plugin. The whole procedure is very well documented in this instructable written by Groover.