Making for Beginners - Part 6

Making the Cut and Troubleshooting Laser Cutters

Andrew pullin

Issue 65, December 2022

How to use LightBurn laser cutter software, and use a laser cutter to create a simple Tangram project.

In this exciting episode, we are going to be setting up and cutting out our Tangram project. We will also be looking at a few other things we can do with our laser cutter, including engraving images and using masking for colour. We will look at a few resources to get free models and useful things from the internet. So, stoke up your PC and make yourself a Homilo (Hot Milo) and let’s get into it.

Setting up the Cut

Now that we have finished our Tangram design (see Issue 64), we have to set up the file to be actually cut by the laser. The first thing we will do is set up the order we want to cut. This is important because if you cut in the wrong order then strange things may happen. The most important thing is that you should do any engraving or images first. The reason for this is that if you cut first, it may change the position of the material you are engraving and that will mean the engraving might not be in exactly the right place. Laser cutters are precision machines so if the work material is out of position, the cutter may not actually know that and make the cut anyway.

The area of the software we are looking at is the right-hand side of the screen in the Cuts and Layers section. We have four “Layers” we have created. The black layer is the outline of our Tangrams; the blue layer is our Tangram pieces; the green layer is our engraving; and the red layer, which we have previously turned “Off”, is our construction lines. If we select each layer with the mouse by clicking on it, we can use the arrows to move them up and down and change the order. The problem is: what is the correct order? Well, a little logical thinking will be needed to work this out.

The first cuts we want will be the engraving, so we want the green layer first. The next layers are a little more tricky so let’s have a think. If I cut out the Tangram first, then potentially the square may drop slightly if the material is a bit warped.

We try and avoid using warped material because it can ruin our precision, but sometimes it just cannot be avoided. We try to bend it in the opposite direction to remove the warps but it sometimes cannot be avoided because it may break. Good storage to avoid warping and dry materials kept in humidity-controlled areas will help here.

Getting back to the cut, it is not a good idea to make the outline cut first. If we make the Tangram piece cut first, there are two pieces that are not directly attached to the outline. These pieces may drop, but it will not be a big problem because we will have engraved them already, and it should not affect the other pieces. We could have made this a completely separate cut using layers, but in this instance, we are happy it will not cause a problem. The end result is that we will make the Tangram pieces cut second.

The final cut (sounds like a great name for a Pink Floyd album!), will be the Tangram outline. We will put the construction line layer last. It will not affect the overall cut, but it is a convenient place to put it if something goes wrong. After moving around the various layers, it should look like this.

The next thing we need is to set the material for the cut. We will be using 1mm Beech-Laser plywood that was supplied by Darkly Labs. Obviously, any material supplied by the manufacturer has been tested and will be suitable for the laser cutter. The Emblaser II has a materials library of pre-tested materials.

Remember from our previous article that some materials can be DANGEROUS so make sure they have been tested BEFORE you cut. At the bottom right of the LightBurn screen you will see some tabs; click on the one called library and this will be displayed. If you select each of our layers in turn and click on “Plywood (Beech-Laser) > 1mm” in the library, you will see the default settings for this material, for our cuts we want the “Line” settings. Use the assign button on the right to set the material.

It should look like this:

You might have noticed a couple of other settings called “Fill” and “Image”. These settings are used to engrave texture within a boundary and to actually engrave mono-colour images onto material. More on this later.

The last thing we need to check is our speed and power settings for our cuts. You may have noticed that our construction lines layer was changed when we set the material for it. For now, click the output, show and air buttons so that they are all red or OFF. The engraving layer right now is set to 300mm per minute speed and 100% laser power. If we cut at these settings, the laser will cut through the material, which in this case we DO NOT want to happen.

We only want to engrave here, so what settings should we use? Well, these settings are a bit of hit and miss and a bit of experience. It really depends on the amount of power applied to the material as to what actually happens. If you speed up the laser cut settings, less power will be applied to the material, it will also speed up our overall cut as there is a lot of text we are printing.

If we also set the Pwr settings to less than 100%, this will also reduce the amount of power and make a shallower cut. This can be important with fine, precision cut lines very close together. The laser is producing huge amounts of heat, and if the heat does not dissipate quickly then the material can catch on fire. The safest method with really fine cuts is faster speed and lower power, but cut two or more times if you want to cut out very small pieces. We will be changing our engraving layer to 600mm per minute and 30% power. It may not be enough, but we will know quickly because it is the first cut.

If it doesn’t work, we can stop the cut and change the numbers without really affecting the overall project. To change these settings, double click the Spd/Pwr numbers on the engraving layer and a box pops up. Change the speed (mm/min) to 600, and the max power to 30%. Before we close this box, notice that the number of passes can be set here if you wish. For now, most other settings are a bit advanced for us so close the box and we are almost ready to cut. By the way, it should look like this.

Ok, we are almost ready to stone and rotate (Rock and Roll in the old language). We have set up our layer settings. Make sure the output, show and air switches are all green on the Cuts/Layers box. The two most important ones being Output and Air. Output is obvious; Air is about the cutter’s air extraction system that helps cool the cuts and reduces the possibility of fire. Now we click on the laser tab at the bottom right of LightBurn.

Setting up the laser to cut is fairly straightforward but there are a few tricks to know. Firstly, check all our layer settings are correct. The speed and power for all our cuts we should have set, so here we are just double-checking (marked in red); the material should be pre-set (marked in yellow); the support is marked in blue and is very important.

The support is the actual distance the material will be at when the laser cuts. The laser is focussed and so knowing the support distance is critical to a good cut. The Emblaser II has the support height actually printed ON the support.

With the support on the library Emblaser II we are using, it is not always in the correct place and has to be manually moved so that the origin of the support is in the same place as the origin of the laser. It is a bit fiddly to get it correctly positioned, especially as the laser “Sighting Light” is hard to see under the orange safety perspex, but it will not go on unless the perspex is closed. This is a safety feature of this machine.

After positioning the support, it is now time to put the material into the laser. The support has some rulers on the edges to help with this if you are not using material that is easy to position. One of the reasons we set up our project so that it was not right on the edges is so that if the support is not quite correctly positioned it will not matter. We are sure there is a better way to set this up but we don’t know what it is yet – hey, we are still learning just like you guys!

When the support is correctly placed, lining up the material is a doddle. Just line up the edges with the support. Close the lid of the Emblaser II; turn on the laser safety cut-out (the red button on the other end from the power button; go to the software and press the home button (marked with green arrows) then press the Go to Origin button; check the laser sight light is about right with the material; then press the square frame button just above the home buttons to check it will fit the material. If the sight light remains ON the material when framing, then all of the cuts will be ON the material, which is what we want.

The last couple of things we want is to check the project will cut correctly and save the program. To do this, click on the little screen icon next to the camera on the LightBurn toolbar (in yellow). This will open the preview window. Press play on the preview window to see what the LightBurn software has worked out with the optimal way to make the cuts for this project. It will basically run the G-Code program that will be sent to the laser cutter on-screen. Sometimes you might pick up issues here, so it is a good idea to run the play function at least once. You can fast forward if it is particularly complex. Notice it will calculate the cutting time – close enough to 38 minutes for this project. Close this window and save the G-Code using the button on the right (in blue).

We are now finally ready to cut. Check the Emblaser II is powered up; make sure the lid is closed; make sure the red laser safety cut-out is lit; make sure air extraction is ON; take a deep breath; press the start button.

I hope you were not planning on going anywhere for the next 40 minutes. It is VERY IMPORTANT to be close to the laser cutter and monitor it regularly. I have had two small fires when cutting our projects! Not serious because we caught them before they became so. This technology is GREAT but it also needs to be WATCHED to stay SAFE. I also had a cable get caught and interrupt the cut. It was almost finished and didn’t really affect the Image we were cutting, but it was a bit annoying.

Note: Check out our smoke detector project from Issue 18 to add to your fire prevention strategies in your workshop.

“Houston – we have a Problem.”

In the image here, you can see that the laser didn’t quite have enough power to completely cut through this Material. It is not a disaster (this time) as we can easily finish it off.

The annoying thing is that there is no way to know until you move the material and then it is too late to re-cut. We have bumped up the power and speed to 450mm/min and 100%. That might be a bit overkill but should be ok since we will be passing twice and we want a quick cut if we can. If it doesn’t work then on our last set, we will bump the speed back down and still do two cuts. You learn with experience; this is the first time we have cut with this particular material and so a few teething problems can be expected. Usually, we use 3mm generic plywood. The stuff we are using today looks a little better and will be slightly more resilient with ‘teenaged fingers’.

Just finished and the same thing happened. On investigating, the plywood has slightly warped which would have meant the laser was out of focus for the cuts. Again, it isn’t a disaster, but it is annoying. The last cut we will set for 300mm/min, 100% and make two cuts. If that doesn’t work, we might have to get onto the internet for more troubleshooting.

There is no shame in getting onto the internet and researching problems. That is the way I have learned most of the stuff I am writing about. There are heaps of forums and additional sites apart from the manufacturer's websites. There are some good YouTube channels, including an Australian one that regularly uses the Emblaser II.

By the way, the image shown here is what we saw before we picked up the sheet and found it had not cut all of the way through. The finished product will (hopefully) work. All we had to do to finish with the other two sheets was snap off all of the pieces and a quick sand with paper and a block. It also made the edges a bit cleaner as the laser “burns” the material and so black charcoal is left on the edge of the cuts. Not a big problem but something to be aware of.

Other Projects and Resources

There is obviously quite a lot more that can be done with a laser cutter, and there are a huge number of free and “Pay for Plans” out there on the internet. Be careful with projects that you download from the internet. Apart from the usual precautions, make sure you know what format these plans are in and if you can use them.

We have discovered plans in AutoCAD dxf format, SVG and other vector files, but we have also seen files in Jpeg that need to be converted before use. It isn’t that you cannot use them, just that you may need to process or convert the files first. One very useful trick we have learned was to take a line drawing in JPEG or PNG format and use the LightBurn software’s “Trace Image” function to convert it to a vector image. It is possible to just print the image, but it will take a great deal longer as the laser will treat the file like the Bitmapped image that it is and create it like a fax machine – one line of pixels at a time. The project here is a line drawing from Wikipedia we converted to a vector image and cut.

There are some other pretty cool projects that can be downloaded for free. This project is from the Darkly Labs website. It is a quite complex cut and assembly but it has come out brilliantly and is now a centrepiece of our room.

It wasn’t exactly cheap either as it was 36 individual pieces of 3mm plywood but it was well worth it. The sanding of each piece after took ages but the different edges from all of the pieces really add to the look. We are intending in the future to create another one a bit bigger and cut from Aluminium. It will need a bit more work to save on materials but should look great when finished.

There are a couple more techniques we also want to show you to get the most out of basic a laser cutter. The first is how to cut an image. This is really simple to do. The first thing you need is a decent image you want to cut. Images with good contrast work best, but any image will work to some extent. Just simply cut and paste the image you want into LightBurn. There are a number of image formats that will work but we find SVG and JPEG will work best. You can convert any other formats with free online converters easily enough.

The way to laser cut an image is straightforward. Remember when we set the cut type to line and there were fill and image options? Just set your cut to image and it will work. It works best if you have all images on a separate layer. Before you cut any images, it is an excellent idea to read the LightBurn manual about image settings, found here:

The two most important things to remember are that power and speed settings can vary with different materials, and that even default settings will not always work. You may have to play around to get it right. The other thing to know about are the different image modes. Image modes are settings about how an image will be dithered prior to the laser cutting. Some are better than others and some are specific. The webpage in the link has a great comparison of the different types.

In this image we printed, we don’t recall the cutting speed but we do recall using the “Jarvis”, which is a very high-quality setting. Obviously the higher the quality, the more time it takes. This particular image took a great deal of trial and error before we went for the full-size cut. It took about four hours to cut, and this was the cut where the cable got caught and we lost the last 20mm off one side. It still looks great. This image was a free download from a Neon Genesis Evangelion fan site. You may notice that there is some texturing from the material used but it is otherwise very good.

The last technique we want to share with you is called masking. Masking involves literally covering up the material with painter’s tape to mask the surface. The laser cuts through the tape as if it wasn’t there and into the material as usual. When the cut is finished, the tape can be removed and painted with different colours. The tape keeps the colours from spreading and nice clean lines. Below is a shameless plug for what the author, Andrew, does when he isn’t writing magazine articles.

You will notice that the blue lines are the tape, it is just lifting under the word School. There is a little "bleeding" on the "a" in Teach. Otherwise, as a first attempt, it came out ok.

Well, that brings us to a close on this exciting episode on Making for Beginners. Unfortunately, the vacuum former machine is out of service for now and we cannot write the article we intended for it just yet, but keep a lookout in the future. We hope you have enjoyed the series as much as we enjoy writing them. We look forward to some of you people out there in the real world showing us what you can achieve with a few simple lessons.

Andrew pullin

Andrew pullin

Hobbyist with Diploma in Engineering