If you're here you're either you’re thinking about getting into the laser craft hobby, you already own a laser, or perhaps you have a small business - regardless you’re wanting to make a laser cut puzzle with a level of quality that doesn’t turn out like some of my grade-school craft projects. Welcome!
I’m going to assume that you’re looking into this for the long haul and this isn’t just a one-off product. It’s fine if it is a one-off, but know that if you haven’t done it before, you’re still going to have to spend some time and resources to develop the needed skills.
There are many things to think about in puzzle making and tips and tricks at each stage of production. I’ll capture the journey that I went through and some of the discoveries that led us to the point that we’re at in our ability to make puzzles today.
There are a few broad categories to think about in the production of a puzzle - equipment, materials, puzzle design, packaging and the overall process of production. I may touch upon some or all of these here, but I’ll focus on equipment for this post because the laser, its setup, and its use are among the most critical aspects of creating a puzzle that is both aesthetically pleasing and marketable.
There are a lot of lasers on the market these days and they come with a range of features and costs. I won’t get into which one is best because you can make something with all of them, but suffice to say that as you move toward the more expensive end of the spectrum the machine will make your life easier.
Whether you’re using inexpensive diode lasers like Atomstack and xTool, or fall somewhere along the CO2 laser spectrum - from a low-end K40, to Glowforge, OMTech, Thunder, Boss, AEON to high-end commercial quality machines like Trotech and Epilog each will have some ability to make a puzzle if you understand how the machine works and are willing to work with the machine to get the most from it. Regardless of what you might own, I will get into the fundamentals necessary to make something nice.
Materials
You’re going to be using a laser to cut materials. I know I said this post would be about equipment, but you’ll be putting materials into the laser to cut, so it’s hard not to mention a little about materials at the start.
For the puzzles we make, we use 3mm and 6mm plywood (1/8th and 1/4th inch) that is specially designed for laser cutting. We order our materials from well-known laser community sources. We do not use plywood from Home Depot, Lowes, or other nationwide lumber or big-box stores. Yes, it does cost a little more. You may immediately think about how important it is to optimize for costs and you wouldn’t be wrong, but a bad batch of materials that cannot produce a product is far worse. Not only can you not make what you want, but you’ve sunk capital into materials that you now have to repurpose or sell, sometimes at a loss. Spend your money on quality materials that you know will perform. You’ll thank yourself later.
There are a few reasons that I don’t use materials from big-box stores, but the principle one is that it’s simply not designed for laser cutting. From quality and composition of materials, to glues and glitter, to voids in the product - these materials are used for construction and manufacture, not for bespoke craft items.
Plywood from these retailers can contain harmful chemicals, string and plastic strapping for added strength, glitter used to identify batches of product, as well as voids in the material that create a coin flip every time you use them. Heads you win, tails you lose. I don’t like those odds. When you see your laser beam bounce and fail to cut a piece because it hit a bit of glitter or smell something that you probably shouldn’t when it hits a plastic strap, you know it’s just not the right thing. I’d rather pay a little more for a material that I know I can count upon and if things do go bad I can go back to a specific supplier to rectify the problem.
I get my plywood from the sources below. If It’s birch plywood then you’ll want a B/BB grade. That grade is designed to ensure that at least one of the two faces is free of knots, boat patches, and other defects. These days I use wood that is Poplar with Basswood veneers and engineered for laser cutting. It’s almost always free of knots and I’ve yet to encounter a boat patch. It does sometimes have variations in color from the manufacturing process - from a more standard light-brown/white with grain, to a stronger yellow or greenish tints and even sometimes a salmon color. Given that we’re making puzzles this isn’t of much consequence as the bare board is only visible from the back.
LaserPlywood.net - Justin's a great guy and sells quality, engineered plywood.
SmokeyHillDesigns.com - Lots of specialty wood to choose from.
Feel free to experiment and order from different places and I would recommend that you get a set of samples and try them on your laser. Getting to know how materials will cut, what the settings are for your particular machine, how they react to changes in speed, power, and airflow are all important parts of the process. You may be wanting to minimize costs, but if you want to do this well and don’t already have experience with your machine and a given set of materials, then you’re going to have to make some investment to experiment.
TL;DR - don’t use cheap materials. That doesn’t mean don’t control costs, but use something that you know will deliver consistent quality. You’ll thank yourself later.
Prepping Materials
We are choosy when selecting boards for our puzzles as not every sheet of wood we receive is suited to the purpose. Either they have some pattern in the grain that is attractive and I want to use it elsewhere or they may have some defect or slight or not-so-slight warp to them. Plywood is after all still wood and it’s subject to warping - bowing, cupping, and twists are not uncommon. It’s so common in fact that we have a pile in our workshop labeled “twisty birch”. Not that it’s not unusable, we do use the twisty birch for other projects, but it’s not well suited to making a puzzle, given that you need a fairly flat piece to span 8-18 square inches of space. The flatter the better.
Also, before laser cutting we’ll be adhering a printed image to one side of the wood. To do that it’s important that the face is smooth and clean so that the image will have more surface area to which to adhere. I realize this is woodworking 101 but it’s worth mentioning. My wood comes pre-finished and I don’t have to do much to it if I don’t want to, but if you are buying Baltic birch then it’s likely that it will need a few quick passes with a finishing sander to smooth it out, usually 220 grit will do the trick. Be sure to clean it well afterward with a cloth, compressed air, or both in order to minimize the presence of saw dust that could prevent the image from adhering to the board. I typically don’t use water at this point because it will raise the grain and I’ll have to sand it down again.
Securing Materials
Another important part of the cutting process is securing the piece on the bed. I differentiate between securing and positioning as with the former, we’re trying to keep the piece in a given location and with the latter we’re trying to align the piece relative to the laser head for cutting. We’ll focus on the securing part here and cover positioning in another post. There are a couple of things to consider when securing the piece on the laser bed.
One item is flashback. Flashback occurs when the laser beam strikes the underlying laser bed and the beam and heat both bounce back to hit the underside of the piece. If you’ve been cutting pieces flat on your bed then you’re well familiar with flashback and the results. To minimize the effect of flashback we raise the piece off of the laser bed surface by using small risers at each corner to elevate the piece by 3mm. We make these risers ourselves out of plywood. Raising the puzzle material by 3mm when securing it to the bed is sufficient to keep the piece free from debris and laser marking due to flashback.
It’s also worth mentioning that with puzzles a side effect of raising the material off of the bed is that as the puzzle pieces are cut, they will drop a small distance to the bed’s surface. This is fine and won’t damage the puzzle pieces, however it does mean that some careful planning is needed to orchestrate the way in which the pieces drop.
Most laser cutting software like Lightburn will generally compensate for nested pieces, ensuring that inner pieces are cut before outer pieces. However with puzzles, the cuts are much more complex and even an amazing piece of software like Lightburn can’t always work out the optimal cutting pattern. This is something that you’ll have to do yourself and something we’ll cover in a later post. Suffice to say that you cannot just cut a puzzle and expect a successful outcome without some planning in the way the puzzle is cut.
The other item that needs consideration is movement. In a gantry based laser system the motion of the laser head causes vibrations which can cause a piece to move ever so slightly over time. To avoid this we use rare earth magnets to secure the piece to the bed, one at each corner. Our honeycomb bed contains ferrous material and as such magnets are effective holders. We place one at each corner to secure the piece to a riser. Rare earth magnets are fairly strong and a little care around ferrous metal surfaces and other magnets should be exercised. I’ve had many pairs of rare earth magnets snap together and pinch my fingers in the process, hard enough to leave a mark.
Cutting
Now that we’ve got some materials and can secure them, there are a few things to think about next with respect to using our laser for cutting. There are several factors in cutting - focus, power, speed, air flow, and exhaust - all of which you’ll want to consider.
Focal Point
Depending on your laser, you may have a fixed cutting bed or one that is able to move on the Z-axis, i.e. a moveable cutting bed. Our Atomstack diode laser requires that I raise and lower the laser itself to adjust the focal point. Our 100w CO2 laser has an adjustable bed so that the laser gantry stays stationary and the laser bed can be moved up and down relative to the laser focal point through control panel buttons and software control. Moveable beds are super convenient and will add cost to your laser, but I highly recommend them, whether they’re automated or manual.
The important part here is that you must ensure that your materials are in the right spot to take advantage of the focal point of the laser beam. Every time you put a piece of material on the laser, you should refocus the beam. If the beam is out of focus, meaning that the material is too high or low relative to the focal point, then the beam width will increase which causes loss in precision of the cut and if severe enough can translate into an incomplete cut and wasted materials. I can’t tell you how frustrating it is to have to throw away an entire puzzle because it didn’t cut properly. It happened a lot in my early days and still happens on occasion today, usually when I omit the focusing step in my process. Here’s a picture to illustrate.
Optimally the focal point of the beam is slightly below the surface of the materials, e.g. one might set it up such that the focal point is aligned with the center of the material, something like this.
Practically speaking however, most people focus the beam to the surface of the material as an engraver would. This won’t hurt as long as the laser has enough power behind it and sufficient air flow to help the beam lase through the material. Some experimentation may be necessary in order to find the right focal depth in your puzzle making, but generally speaking, just below the surface of the material is better. For our 3mm puzzles I typically just focus on the surface of the material, with a couple of caveats. When cutting materials, we always raise our pieces off the bed by 3mm in order to avoid flashback and increase air flow. Additionally we use an autofocus sensor as part of our setup. An autofocus helps to automate the task of adjusting a moveable bed relative to the focal point of the beam. Together the raising of the piece to prevent flashback and use of the autofocus will cause the board to flex slightly when the autofocus sensor comes into contact with the board. This means that with the slight movement in flexing, my focal point goes just a hair beyond the surface of the material towards its center. The net is my focal point is just beneath the surface of the piece, which is where I want it to be. For our 6mm (¼”) puzzles I will often focus 1-2mm past the material surface because a 6mm board will not flex like a 3mm board. This manual adjustment helps to ensure a clean cut through the entire puzzle but does have the effect of a slightly wider cut line. Keep in mind that we’re talking hundredths of a millimeter in the difference of the cut. In aggregate however, those small changes in the width of a cutline are noticeable when a puzzle is put together. A loosely cut puzzle creates “slop” in the movement of the pieces.
As an extreme example consider this, eleven pieces in a row that have a cut width of 0.12mm versus 0.02mm would net out an extra millimeter’s worth of gap space between the pieces, which creates a lot of wiggle room in a puzzle. Basically the wider the cut is the more slop there is in the puzzle when moving it around on a table while putting it together.
To further underscore the importance of a tight cut, Artifact puzzles has a line of products called Ecru Puzzles. One selling point of the Ecru brand is that the puzzle is closer-cut or “tighter” than other laser cut puzzles. Make a few puzzles and you’ll understand.
Power
Power is one of the most important characteristics of a machine. The power of a laser is expressed in Watts (W) and is effectively the metric that defines the ability to cut and to cut with speed. Typically with a higher value, thicker material can be cut and thinner materials can be cut at a higher speed without loss of fidelity. Can you cut 3mm birch with a 5W diode laser? Sure you can, but you may be making several passes over a piece of birch to do that, and each pass cuts a little more of the material and puts energy (heat) into the workpiece. This can result in an uneven cut and too much heat which can actually burn the piece. Ultimately you’ll want a nice golden brown to brown color, nothing black or charred. It’s best to experiment with your laser to understand how it cuts different materials. On our 100w CO2 laser we’re able to cleanly cut 3mm birch at 25-30mm/sec at about 6mA on our digital ampere meter. We cut 6mm birch at 18-22mA depending on the vendor and weather. What’s important to note is that there isn’t a linear scale there. While 3mm cuts at 6mA, 6mm takes more than 12mA to cut cleanly. That means that the cut goes all the way through and there’s no charring or soot left on the lasered edge. There are a lot of reasons for that which I’ll get to in a moment.
Speed
I mentioned that we can cleanly cut 3mm birch between 25-30mm/sec. While this may sound slow it’s actually quite good, 25.4mm = 1 inch so it’s ~1 inch/sec. You really don’t want to go too fast with a mid-grade machine as it can result in lower fidelity. This exhibits itself in the form of wiggly lines or backlash that cause an entire piece to be ruined because lines don’t match up where they should. While the stepper motors in mid-grade machines are really good these days, there’s usually no feedback mechanism to support the true position of the laser head relative to the origin. They’re actually guessing based on the inputs to the stepper motors, not in knowledge of the actual location of the head, so if there’s any backlash in your laser at higher speeds, you’re going to see it show up in your pieces. Slow it down and shoot for higher quality.
Take your time and do some cutting tests on the materials that you’ll be working with. Try different speeds and power levels. There are several test cards on the internet that can be used with different materials in order to dial in the best cut settings in terms of speed and power for a given material. I’ve used this one in the past which tests a combination of cutting, engraving and vector engraving. There’s also this one from OMTech.
Air Flow
One of the most important elements of laser cutting is air flow. This is the act of pushing air onto the piece while it’s being cut and it serves a number of purposes including keeping the piece from flaming up, clearing the cut of debris, reducing heat from around the laser head and material, and keeping the material clean during the cutting process, which will be -really- important when it comes time to remove the piece from the laser and clean it. I push a lot of air during our cutting process, typically somewhere between 50 and 60 psi. If you’ve been cutting for a while then this may sound high, but I’ve seen articles that suggest somewhere between 60 to 150 psi is acceptable. What I’ve found is that the more air, the cleaner the cut due to the removal of debris including glue residue, wood resins, and soot. What’s great about learning how to set this up properly is that not only is it useful for making puzzles, but generally improves the quality of anything that you’re wanting to laser cut from plywood.
Unless you’re buying a higher end CO2 laser, you’re likely going to have to upgrade your air assist. Low-end lasers like the K40 typically don’t come with one, and even mid-grade lasers are using a repurposed fish-tank pump to push a little air. That’s usually fine for engraving but for cutting you really want to move a lot more air.
Above is a picture of the compressor that I use for airflow. It’s a Kobalt 26 gallon, 150 psi quiet compressor that I purchased at Lowes. Okay, it’s really not all that quiet, but at about 80-85dB it’s quiet enough that we’re able to use it in our workshop while we work. That’s the equivalent of a garbage disposal or a blender running in the room with you. It’s solid and there are louder compressors out there for sure. The one thing that I will mention and offer a word of caution about is removing moisture from the compressor tank. Compressing air causes water to condense and subsequently it’s forced to collect at the bottom of the tank and needs to be drained out periodically. When you prepare to do this and open up your compressor check valve to allow the air to escape, there will still be a little air in the tank once the check valve closes again. That means when you go to drain it, it’s going to initially blow water out of the drain valve. Usually this water will have a fair amount of rust and other sediments in it so it’s not something you want to do in your workshop, garage, or even on your driveway or sidewalk. I’d -strongly- recommend draining your compressor into the grass in your yard and then washing it down after. Ask me how I know.
Exhaust
Finally, let’s talk about exhausting the smoke and other fumes that are produced during the laser cutting process. Exhaust goes hand in hand with air flow. While pushing air into the piece to keep the cut clean and disperse heat is important, it’s equally important to pull away the smoke, soot and other debris that is created during the cutting process.
The more air you can move through your cutting chamber the better, but keep in mind that there also needs to be an intake for air to flow into the laser’s cabinet. We have a fairly large laser with a with a 24 x 40” bed and a sizable cabinet and we find that opening our passthrough flap in the front of the laser allows sufficient airflow through the box. Be sure to be safe if you’re doing anything that would expose you to the beam while cutting.
Fans are typically used to act as an exhaust mechanism by pulling air from the chamber, and unless you’re buying a laser on the higher end of things you’ll probably have to upgrade your exhaust fans as well. Our K40 had a 3000 RPM fan in it but it didn’t really push more than a couple of hundred cubic feet per minute (CFM) because it was designed for engraving, not cutting. I replaced it with a 660 CFM exhaust fan and it created negative pressure within the box.
Likewise with our 100W CO2 I removed the stock exhaust fan, used a die grinder to remove the grate covering inside the lasing chamber, and attached a pair of 720 CFM exhaust fans in parallel. I’m guessing they fight one another a little when running but they pull a lot of air from a fairly large cabinet, enough that I can see the smoke flowing from beneath a piece while it’s being cut and I don’t see smoke above the piece. That’s good enough for me.
Summary
So that’s it. I realize this was a long article but these are some of the essentials and I’m hoping that you caught some of the tricks to optimize your setup for cutting. Here they are with a little summary.
Materials - Invest in plywood made for laser cutting, not cheap material from big box stores.
Securing - Raise your piece from the bed and secure it with magnets.
Focus - Find the optimal focal point for material thickness. Refocus for each puzzle.
Power - I’d recommend a 50-100W CO2 laser for puzzle making. Bigger isn’t always better. Perform some experiments on the materials to find the optimal power settings
Speed - Sure, faster saves time, but this is a marathon not a sprint. Moderate speed with sufficient power for the given materials will always win. Again do some experiments.
Air Flow - Plan to put as much air onto the cut as you can. It will keep the piece clean and ensure a higher precision cut.
Exhaust - Move as much air through the box as you can. Be sure that enough air is getting into the box. If you don’t have smoke collecting in the chamber then your exhaust is working properly. Until next time!
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