Adding a laser to your LongMill

Last Update: 16 April 2020

Putting a laser on your LongMill or any CNC machine can be a fun and useful tool in expanding your creativity. The LongMill fully supports the addition of a laser module.

Please note that lasers are very dangerous. Sienci Labs will not responsible for injury or damage caused by the use and installation of lasers.

Here are some safety recommendations:

  • Wear eye protection, specifically laser safety glasses.
  • Never point the laser at other people or yourself
  • Cut in a well-ventilated area, or have a way to remove smoke
  • DO NOT CUT/ENGRAVE: PVC, ABS, Fibreglass, and any other materials that emit toxic fumes when cut
  • Never leave the machine and laser unattended, and make sure that you have the equipment to deal with fires

In this application, a laser is used to burn or ablate materials in the CNC machine to cut and engrave them. It works very similarly how many of us would have used a magnifying glass to burn things outside by focusing the sun into a very small point. Because lasers focus down to a very very small point, you can cut and engrave extremely small details. Here are some pros and cons of using a laser with your LongMill:

Pros:

  • Ability to cut extremely fine details
  • No need for workholding
  • No tools or end mills to wear out
  • Burnt engravings and edges provide a contrast against the base material

Cons:

  • Creates smoke and is a fire hazard
  • Lasers can be very dangerous
  • Lasers leave a burned edge where it is engraving or cutting, which can be undesirable at times

Choosing a laser:

While there are a couple different types of lasers used in cutting and engraving, the type of laser suitable for the LongMill is called a diode laser or a solid-state laser. In simple terms, it works very similarly to a LED light, but with the ability to emit coherent light that can be focused into a very small spot.

When purchasing a laser, you want to look for:

  • PWM (pulse width modulation) control
  • Power supply, driver, and laser module

You will also want to choose a power rating that works for you:

  • Lasers can come up to 15 watts of power
  • The listed power may refer to continuous power or peak power (not the same thing)
  • Sometimes manufacturers falsify the actual laser power rating, or overclock a diode with a lower rating
  • Higher power lasers typically do not last as long

Setting up the hardware:

Installing a laser onto your LongMill is fairly easy. There are just three major connections to make.

1) Connecting the laser to the driver:

Typically, you will find a pair of leads to power the laser diode module and a pair of wires for the cooling fan. You can extend these wires to route them through the drag chains.

2) Connecting the driver to the Spindle PWM control port on the LongBoard controller

The laser driver will have a +/- input for PWM (sometimes it is marked as TTL) that can be wired into the LongBoard controller on the Spindle PWM (marked as SpinPWM). Note that if you get the polarity wrong it probably won’t work.

3) Connecting the driver to the power supply

Use the provided power supply and power connector to provide power to the driver.

Setting up the laser in GRBL (the software):

You can find all the info about GRBL and how “laser mode” on this page: https://github.com/gnea/grbl/wiki/Grb… To get enable laser mode, connect your machine via UGSPlatform, and send the command “$32=1”. To disable it (when you aren’t using the laser) you can send the command “32=0”.

The other thing you need to look at is the minimum and maximum spindle speed setting. You can pull up all of the EEPROM settings by sending “$$” and finding the number. It should be under $30 and $31. You should set the minimum to 0 and the max to 100. If you are using a spindle that connects to spindle PWM for speed control, you can keep it at the same value, but you will need this number later on when creating your G-code.

CAM software for laser:

There are a couple different options for generating G-code for laser. One very popular one is called LightBurn. It is a paid program ($40 at the time of writing for the license that works with the LongMill). LightBurn works well and has lots of tutorial videos. LightBurn comes with a 30-day free demo.

https://lightburnsoftware.com/