Laser cutting is something that I use a lot in my prototyping process because it is a (relatively) easy way to make a 3D object with a certain degree of speed and precision, but it can be a tricky thing to navigate if you’re just starting out with digital prototyping. There is a lot of ground to cover so this post will be separated into 2 parts. The first will cover basics such as vectors, file preparation, materials, and ordering. The second part will get into the nitty gritty of prototyping with a laser cutter, taking a look at various techniques, types of joinery, and resources.
How does a laser cutter work? Basically, a laser beam is reflected off a lens that is focused on a material, moving on an XY (and sometimes even Z) axis as it burns through that material in order to cut through or take away surface material.
A laser cutting machine is generally capable of doing 3 things: cutting, scoring, and engraving (also known as raster etching). What’s the difference between the 3? Cutting is pretty self explanatory - the laser cuts through the material by following lines drawn on a computer program. Scoring is essentially the same thing as cutting but using a lower power level so that the laser doesn’t cut all the way through. Raster etching is similar to scoring, only instead of following a line it renders a black and white image on the surface by going back and forth and cutting material away, similar to how a printer cartridge moves back and forth while leaving ink on the surface of a page. If you want an engraving that has areas filled in, you would only be able to do that with a raster etching.
Vectors and File Preparation
One important thing to note is that laser cutting and scoring require graphics in the form of a vector drawing, whereas a raster etching can handle other types of files, like .jpgs for example. However, if you’re doing something that only requires linework, you’re much better off drawing it as a vector because scoring a line takes significantly less time than engraving a line from a raster drawing. Why? Because instead of following a line around a shape, the laser head has to go back and forth dropping little dots like a printer. Keep in mind that the depth of scoring or engraving can also be controlled in the power settings, so you can request a lighter or heavier engraving, or even make use of both to create contrast.
But what is a vector, anyway? A vector graphic uses lines and curves to create shapes rather than using pixels. This allows the image to scale up and down without losing resolution or becoming “fuzzy.” Text is usually rendered as a vector, which is why it doesn’t get blurry when you zoom in, but in order to cut or etch some text, you will need to convert it to an outline, otherwise it would be raster etched by default. In Illustrator you can do this by selecting the text and going to Type > Create outlines. Note, however, that once you convert the text you will no longer be able to edit it. You will also need to set your line thickness to either “hairline” or .001, depending on the program you’re using. Otherwise, it may not be properly interpreted by the machine and could be engraved instead.
Popular programs for drawing with vectors are Adobe Illustrator, AutoCAD, and Rhino. I’m not going to teach you how to use these, but there are plenty of great YouTube tutorials. (If you are looking to hire someone to do this for you, it is a service I provide on a freelance basis, so feel free to contact me about your project.) Most laser cutting vendors offer this service for a fee as well. You can also read more about vectors here.
Laser cutting facilities usually have their own preferred file setup. Most of the time this will just mean changing your canvas size (to match either the size of their laser bed or the size of your material) and changing the colors of your lines. It’s best to keep your raster, scoring, and cutting lines on separate labeled layers. Here’s an example of one company’s file prep guidelines, where they specify different color coding for rastering, cutting, and scoring. What they don’t mention is that your selected colors should also be “pure,” meaning that in the RGB color selector your black must read as 0,0,0, red is 255,0,0, green is 0,255,0 and blue is 0,0,255.
If you have shapes that are made up of many lines, be sure to “join” those lines in your vector program so that the laser reads them as one continuous line rather than cutting them in segments. This will not only save time but will also prevent additional burn marks as the laser starts and stops. If you have shapes or lines that cannot be joined, I recommend ordering the layers in a way that makes cutting more efficient. To give you an idea of what I mean, pretend you’re cutting these shapes out of a piece of paper - you’d probably start on one corner and work your way down or across, rather than cutting out pieces from all sides randomly, right? The laser wants to do the same thing. Causing the laser head to move back and forth across a large area will waste a lot of time and end up costing you extra.
Common materials used for laser cutting and etching are paper, cardboard, wood, MDF, acrylic, metal, and even leather. Materials like wood and paper can sometimes end up with burnt-looking edges from the laser. When it comes to wood, some companies offer a masking service where they tape over the surface of the wood to prevent the burnt look. Whether or not it is worth paying extra for really depends on the company, the cost, and how much that matters for your project. If it’s just a prototype, don’t worry about it too much. If it’s a finished piece, see if you can get a sample from laser cutter, because some providers leave more burn than others. Here is a fairly drastic example of no tape vs. tape. Keep in mind that if they don't take off the tape for you, that's more work you need to factor in for yourself, (which doesn't seem like a big deal unless you're doing it 100 times.)
Also, if your wood is warped, an etching/scoring may not come out perfectly even across the whole image. This is because the laser is focused at a certain point on the Z axis, and if the material is not flat, the line can go out of focus and become thinner or thicker in some areas. Here’s an example where the snake on the bottom was scored correctly, but the top piece of wood must have been sitting warped on the cutting bed because the line looks thick and inconsistent.
One other thing to note with wood is the grain direction. If you’re making any small parts out of wood, make sure the grain direction is running the long way. Otherwise, the piece will easily snap in half. Think carefully about your tolerances in general as well. Lasers can cut with great precision, but anything thinner than 1/8" or 3mm can easily break regardless of material. There is also the type of wood to consider. The most "laser-friendly" wood tends to be birch plywood, but you can also use hardwood and other specialty plywoods. The boxes from Tale of Ord are made out of maple plywood, which cut and engraved nicely, but I had also experimented with a cherry plywood at the time, which was completely unusable. The wood itself was beautiful, but it turned out that the core of the plywood was made out of a material that was not so laser-friendly, and the edges of each piece were so covered in soot that it was impossible to touch it without turning your fingers (and consequently much of the wood) black. Anyway, the lesson is, if you're using a new material, experiment with it first before putting all your eggs in one basket.
Acrylic is an awesome material to use because the edges come out really clean and you can create interesting effects with surface etching. Etching on a clear or translucent acrylic will create an opaque area; etching on an opaque acrylic will create contrast in color and turn a glossy surface matte; and etching on a mirrored acrylic can create a non-reflective area, and is especially interesting when you do it from the backside. (But remember, etching a lot of surface area will be costly.)
Similar to how the wood masking technique works, acrylic typically has a mildly sticky paper layer by default. It protects the surface but also prevents the laser from reflecting on the material. You will most likely need to remove this paper yourself, as most vendors do not do this by default. This is often not a big deal with cut shapes, but if you’re etching something very detailed, especially in volume, it can get annoying to clean up the surface of all the little paper bits.
There are probably hundreds of companies offering laser cutting services, so who do you use? For one thing, I highly recommend getting multiple quotes before proceeding with a project, as prices and cut times can vary drastically. You’ll generally need to upload or email a file to get a quote, so make sure you look at that company’s website first and see if they have any file prep guidelines. From what I have seen, standard pricing for laser cutting services is about $1-2 per minute, but just because someone has a lower per minute price, it doesn’t necessarily mean that it will be cheaper to make your project there. The actual cutting speed can vary based on the vendor’s settings and the machine itself, and there is also quality to consider. Sadly the 2 times I have found a service charging less than $1/min, their communication was terrible and my pieces came out burned to the point of not being presentable.
If you’re making something that requires multiples, always make one sample first. Sometimes ordering multiples seems more cost effective, but if your piece doesn’t come out perfect on the first try, you’ve just wasted a bunch of money cutting multiples of the wrong thing. Trust me, I have learned this lesson the hard way! Because of this, and also for the sake of saving on shipping, I would normally recommend trying to find a local service if you can. In the days of social distancing though, that might not help as much...
When I was working on Tale of Ord, I spent some time compiling a list of every laser cutting service in the US that I could find and get a quote from. Ultimately I ended up working with Oaklabs in California (despite the distance) because of their quality, communication, and willingness to work with me on a big and complicated order. I have also worked with Fabberz lab in NYC (local to me) on some smaller projects so that I could pick them up quickly and not waste time on shipping. To compare, Oaklabs’ per minute prices are mid-high with no price breaks, whereas Fabberz offers some great packages if you’re going to do a lot of cutting. However, the cutting time at Oaklabs was often much faster, negating the discount I would have otherwise gotten, but adding on the burden of shipping... In any case, I am happy to recommend both of those companies, and would use either one again, depending on the project.
There are online services like Ponoko (US-based) or Polulu (for UK and Europe) that make it very easy to order (basically like a print on demand service), though they tend to be pricier and mark up their materials as well. Independent vendors often have their own stock material but will allow (or even prefer) you to provide your own, as long as it meets their requirements. If you are supplying your own material, be sure to confirm with the vendor that they will be able to cut it before you place the order. If I am making a test piece or a small item I will usually opt to pay for stocked material, but if I am making a larger order I will normally supply my own because ordering wood or acrylic directly from a supplier is usually more cost effective than buying it from the vendor.
On a closing note, if you're not too cost-sensitive then you might consider using the negative space left from your cuts to do some experimenting. As I was working on some pieces for The Emerald Flame I had a little extra space on my turquoise acrylic board, and voila! Adorable jellyfish earrings. :)
That’s all for now! In the next post I will talk about joinery, curved surfaces, hinges, and other fun laser cutting experiments. What’s your experience with laser cutting? Do you have any advice or insight into the process?