Introduction: Aligning Laser Cutter Mirrors

About: Hello I'm a college student that enjoys making things with machines and hand tools, using materials like metal, wood, clay, and plastic. I am trying to start my own business in making small crafts, jewelry and…

You finally decided to buy a laser cutter. You buy your material and fire up your laser cutter only to realize after everything is cut, that your pieces don't line up PROPERLY!!!

When it comes to laser cutting, engraving, and marking, having your mirrors clean and aligned can make or break your project. If you're engraving or marking material, you might get away with having a angled beam. However, if you are cutting, a perpendicular beam is a necessity. When laser cutting your beam will already be losing power as it cuts through the material, so you will already be getting a very small angle in your cut, usually not noticeable. When your mirrors are not aligned right, the laser will cut slanted in a much more noticeable way.

That is why I am hoping this tutorial will help show others how to make better cuts with their laser cutter. And if the winner of the Epilog Laser Contest takes a look at this Instructable I hope it helps you out!!!

Step 1: Safety


To begin with most, if not all, laser cutters use a class IV laser, or some powerful laser diode. Laser diodes are powerful enough to blind and hurt you. Class IV lasers are able to blind, burn, cut and lacerate you. Not only are these components able to hurt you, they burn hot enough to easily start fires so make sure you wear eye protection, keep the lid closed on the enclosure any time the laser will be turned on and keep a fire extinguisher close at hand.


Be careful handling CO2 laser tubes, do not touch any of the wires leading to or from the laser tube while the laser is turned on or even plugged in unless you know what you are doing. This is EXTREMELY HIGH VOLTAGE!

Step 2: Materials Needed

  1. Safety glasses
  2. Post it notes (or painters tape)
  3. Pliers (maybe)
  4. Screwdriver (maybe)
  5. Scissors
  6. Laser cutter
  7. Scrap material
  8. Fire extinguisher

Step 3: Main Components and Overview

Co2 lasers have a large long tube that emits a powerful stream of photons that will bounce against (usually) 3 different mirrors before hitting your work piece. The first mirror is right next to the tube and sets the laser beam to go along the Y-AXIS. The second mirror is posted onto the arm that drives along the Y-AXIS and bounces the beam to go along the X-AXIS. The third mirror is attached to the actual laser head which goes along the X-AXIS arm and bounces the laser beam so it goes straight down.

When laser cutting or engraving material, the laser is supposed to be perfectly perpendicular to your work piece at the point where it strikes. With large flat pieces this should prove true from the very top left of the work piece to the very bottom right of the work piece. If the lasers are not properly aligned then when you cut the piece it will cut at a slant. This can be a problem if you are making pieces fit together because they will not fit square. You can also engrave or cut round objects too if you have a rotary device. But the same problem occurs if you are cutting at a slant.

Everything will start with the Laser Tube, if it is not level then the beam will start of slanted. Next is Mirror One, then Mirror Two, and lastly Mirror Three, then it will go through your focal lens into a concentrated beam and mark your material.

The Laser Tube usually has two straps that hold it in place

Reflecting Mirrors usually have four or three adjustment screws that will angle the mirror.

Step 4: Preparing

Look at the path that the laser will take and take note of 4 holes nearby the Laser Mirrors. There should be one BEFORE Mirror One and another AFTER Mirror One. The third will be BEFORE Mirror Two and the last will be BEFORE Mirror Three.

Measure the diameter of these holes, they should be around 3/4 in - 1 in.

Take your post-it notes and cut them into strips the same width as the diameter of the holes (or smaller).

Step 5: Orders of Operation

Simply speaking this will be a trial and error job.

  1. Take the strips of post it notes and cover each of the Three holes with them vertically. (skipping the very first hole.
  2. Close of the laser and turn on the power
  3. Set the Laser head to the top left of work area
  4. Hit the pulse button.
  5. Only punch the button for a millisecond.
  6. Turn the laser power off for safety.
  7. Open of the machine and take a look at the strips of paper.
  8. The goal is to get the burn hole into the exact center of the hole using the paper as reference.
  9. Adjust the mirrors starting from where the laser is first emitted leading all the way to the laser head.
  10. If the laser hole is too far down, either LOOSEN the TOP screws of the Mirror, or TIGHTEN the BOTTOM screws of the Mirror.
  11. If the laser hole is too far up, either LOOSEN the BOTTOM screws of the Mirror, or TIGHTEN the TOP screws of the Mirror.
  12. If the laser hole is too far left, either LOOSEN the RIGHT screws of the Mirror, or TIGHTEN the LEFT screws of the Mirror.
  13. If the laser hole is too far right, either LOOSEN the LEFT screws of the Mirror, or TIGHTEN the RIGHT screws of the Mirror.
  14. LOOSENING screws will tilt the mirrors TOWARDS the direction of where the screws are located.
  15. TIGHTENING screws will tilt the mirrors AWAY from the direction of where the screws are located.
  16. Once you have the Second Hole centered continue on to the Third Hole.
  17. Repeat steps 10 - 13 for the Third Hole.
  18. Repeat steps 10 - 13 for the Last Hole.
  1. Now set the laser head to the bottom right of the work area.
  2. See if the holes are still centered.
  3. If not do minor adjustments and switch back and forth from the top left of work area and bottom right of work space and find a comfortable middle.

  1. Make some test cuts.
  2. If test cuts do not make perpendicular cuts repeat adjustments.

Step 6: Common Problems

Problem One

  • Can't get burn holes centered.
  • Burn holes are showing up outside of hole.

Solutions to Problem One

  • Tube is misaligned, loosen and tighten tube. Add silicon shims where needed.
  • Initial mirrors are misaligned. Readjust.
  • Mirrors are faulty check quality.

Problem Two

  • No holes burned into paper.
  • Paper catches fire.

Solutions to Problem Two

  • Laser power is too low/high, adjust accordingly.
  • Pulse button is pushed to long/short a time, adjust accordingly.
  • Paper is too thin/thick, adjust accordingly.
  • Mirrors are dirty and need to be cleaned.
  • Mirrors are corrupted and need changing.

These are the most common problems when aligning mirrors. If any other problems occur it is probably because of faulty components due to the tube or power supply.


There are 3 main types of Mirrors

  1. Silicon with a thin gold layer (Si)

Inexpensive. great reflection, difficult to clean and easily damaged, good for up to 80W lasers. Clean regularly.

2. Polished Molybdenum (Mo)

Strong/durable material, low reflection, costs more than Si, used for over 80W lasers.

3. Polished Copper (Cu)

In-between quality, durable for most lasers, more expensive.

Make sure to clean your mirrors regularly! After and before every use to be cautious. lenses can get real expensive really fast. Just like with all things, regular maintenance extends lifespan and produces better quality. Using isopropyl alcohol and a micro fiber cloth and carefully cleaning lenses goes a long way.

When cutting, a longer focal length laser lens will make a better cut. Focal lenses can come in lengths anywhere from 1in - 4in (usually). The shorter the lens, the more refined detail you will get so make sure you use shorter focal length lens for high definition engraving and marking. If you are going to cut, use a 4in lens, it extends the beam cutting distance so you get a less angled cut.

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