Cutting Fabric on the Laser Cutter

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Pattern pieces on the laser bed after cutting
Edge of a laser-cut pattern piece
Proof that laser-cut fabric turned into a real item of clothing

Why laser-cut fabric instead of cut it?

Anyone who has experience sewing knows that cutting out the pattern pieces creates a foundation for the rest of the work to go smoothly and for the pieces to fit together as intended. Advantages of laser-cutting vs traditional cutting methods

  • More precise than scissors or rotary cutter. No distortion from scissors pulling up on the fabric, no jagged lines, no human error.
  • Perfectly straight lines and sharp corners make aligning pattern pieces very easy.
  • Repeatable - make as many copies as you want and they'll all be the same
  • Seals edges - On fabrics that tend to fray, like satin or brocade, using a laser seals them better than cutting with scissors. (For super delicate fabrics, overstitching is probably still a good idea for long term durability)
  • Crazy intricate designs are possible!
  • You can add in pilot holes for snaps, rivets, buttonholes, etc

Disadvantages

  • You need to be fairly comfortable with illustrator, inkscape, or other vector graphics programs
  • Editing commercial designs in Illustrator will still take some time, especially if the PDF is of poor quality.
  • Sometimes you don't want a charred/melty edge. Especially important if the edge is going to rub against your skin a lot, of if there's going to be multiple layers of fabric. The edges can always be finished after sewing though.
  • Darts and other pattern markings on the inside of the pattern piece can't be easily lasered.
  • The laser bed can be dirty and you can't work with large amounts of fabric easily (like more than 3 yards at a time)

Safety

The most common question I get asked is if fabric can be cut on the laser-cutter safely. The short answer is yes, anything but pleather. All fabric is required to tell you the fiber content, so just check what you buy. No vinyl! (AKA patent leather, pleather, PVC)

The other safety concern is watching your air assist. More details are below, but basically you want to make sure that there's enough air flowing to keep the laser from igniting your fabric.

Fabric Types

There are 2 main categories of fabric material

  • Natural (i.e. plant-based): cotton, linen, rayon, viscose, modal, bamboo, etc. All of these are laserable and end up with burnt edges, similar to laser-cutting wood or MDF, because the base material is cellulose, the same as wood.
  • Synthetic: polyester, nylon, neoprene, etc. These are plastic-based and the edges will melt instead of burn. This is not a complete list of synthetic fibers! Some synthetic fibers might not be ok to cut so do your research on anything that's unusual.

Both categories of material are generally fine to laser-cut, they'll just end up with crispy edges or melty edges, depending on what you use.

There are also 2 main types of fabric construction

  • Woven: These have fibers going in straight lines perpendicular to each other, and have very little stretch. These are very stable and easy to laser-cut, but not as popular for modern clothing because they aren't stretchy.
  • Knit: These are constructed by a series of loops. They're very stretchy, commonly used in T-shirts and other clothing. If you're cutting intricate designs, be aware of the fact that the edges of knit fabric curls. This isn't super noticeable on large piece, but once your pieces get narrow, like under 2 inches, the curl can make them hard to work with. Some tips on dealing with that are below.

In addition to fabric, there is also interfacing and iron-on adhesive, both of which can be very useful for complex designs!

Making/Editing Patterns

There are a lot of options for where to start with a pattern.

  • Download a commercial pattern as a PDF and edit it in illustrator. More detail below.
  • Trace a paper pattern and turn it into vector paths. I've done this with mask patterns by scanning the paper pattern, then tracing over the image in illustrator. I haven't done this with larger patterns yet, but please add more info if you have!
  • Use commercial pattern drafting software. I haven't done this, so I don't know how easy it is. If it were me, I'd probably export from the pattern software to illustrator and then check everything, but my tool/design chain is pretty illustrator-centric.
  • Start totally from scratch! Use geometry to make your own design, or measure some existing clothes, etc. This is what I did for the [Hurricane Cape]. This requires a lot of prototyping!

Working with commercial pattern PDFs

Commercial pattern PDFs will either come sized for a large-format printer, or as multiple sheets that you're supposed to print out on a normal printer and tape together. If available, start with the large-format printer version. There will be a ridiculous number of clipping masks and groups. Try to release as many clipping masks as you can find, and ungroup as many groups as you can find. (There may be scripts to automate this in illustrator). If you only have the multiple-sheet version of the file, sometimes releasing all the clipping masks will show you the whole pattern piece. If not, you might have to manually join together the different parts of each pattern piece. Commercial patterns for clothing will have different sizes, so just delete everything except for the size you want. This may involve cutting and re-joining lines and it can be very tedious.

Some tips

  • Don't rotate the pattern pieces unless you know where the grain line is on the pattern.
  • If your pattern piece has you cutting around a fold (like for the back of a symmetric garment), you might consider mirroring that so you don't have to perfectly align the laser to a fold. Aligning the laser to a fold is definitely possible, but isn't always worth the effort. If you are going to align to a fold, delete the center line just in case you're a tiny bit off.
  • Be careful about which pieces are going to be doubled. Most pattern layouts will have you cutting a double layer with right sides facing, but for a few fabric types, I would recommend only lasering a single layer at a time. If going that route, you'll need to either mirror the pattern or flip which side faces down on the laser.
  • Notches in the seam allowance can be lasered quite easily. You can make a wedge or just a line if you're only using it to line pieces up.
  • Delete any labels you don't need. There's nothing worse than accidentally lasering text onto a piece of fabric.
  • Sometimes dashed lines come in as tiny individual lines, which is super annoying. Delete all the individual lines and make a new path where they used to be. You can add dashes to the stroke in illustrator for visualization purposes, and if you really want to cut dashes, the LaserCut software can do that from a solid stroke.
  • Be really careful about double lines. There are a few ways to know if you have double lines. One way is to just try to move the piece you're working on and see if anything was underneath it, then move it back.
  • Once you have a pattern piece isolated, it can be helpful to make it and it's associated markings a group. That way you can move it around without the markings wandering off.
  • Once you're close to being ready to laser, I usually make one layer for the laserable lines, and one layer for any notes and markings I don't wan't to be lasered.
  • Join together all the paths that make up each pattern pieces, or make sure to join them in LaserCut before you cut. If there are many tiny line segments, the laser might not cut them in a logical order, resulting in increased laser time or possibly crappy cuts.

Designing your own patterns or heavily modifying existing patterns

This is where the vector path + laser-cutting tool chain really shines. As mentioned above, you can start totally from scratch just using geometry, but it can be easier to start from a commercial pattern, cut & sew a prototype, see how it fits, and then go to town on the pattern to make it as customized as you want.

Base Pattern vs. Pattern w/ Seam Allowances

  • Most commercial patterns come with seam allowances baked in. Read the pattern notes to find out what the seam allowance is. It'll probably be 3/8", 1/2", or 5/8". Use "Offset path" in Illustrator (Ojbect > Path > Offset Path) to offset the path by the seam allowance. This will give you the base pattern piece.
  • Work only with the base pattern piece until you're all done making changes, then reverse the "Offset path" operation to get the seam allowances back. You can also use this to change the seam allowances
    • Don't use 1/4" for your seam allowance like i did on my first project. Seam allowances aren't just there for tweaking the fit, they also make it a lot easier to press the seams, and to finish the seam allowances later if that's something you want to do.
  • When you use Offset Path, you can choose Miter or Bezel. I recommend Bezel, as it lets you see the true seam edge, but Miter is the more typical looking corner. For some pattern pieces, using miter can make the resulting seam seem longer than it should.

Tell Jamie to insert the picture of the Mad Hatter Coat sleeve bottom for visual reference

Some really helpful tools in illustrator

  • Dynamic Measurement - part of the Astute Graphics set of plugins (available on the Media Lab VM), this allows you to measure distances along a curved path. Use it to make sure that the seams on 2 adjacent pattern pieces will be the same length, and check any aspect of fitting.
  • Scissors and Join. Cut apart paths and then re-join only the segments that you want
  • Pathfinder tools - specifically Outline and Divide. Outline just cuts everything into tiny pieces, kind of like a mass Scissors operation, and Divide will divide a segmented pattern piece into individual pattern pieces.
  • Offset path. Use it for seam allowances and for some design elements
  • Expand Stroke or Expand Appearance. Use Illustrator to make fancy swooshy stroke profiles, text, or other graphic elements, and then use one of the "Expand" options to convert that into tool paths.
  • Align tools for aligning holes, Dynamic Shapes tool for adjusting hole size on multiple holes at once
  • Pen, Anchor Point, and Direct Select tools. Use these to tweak anchor points and handles to make curved seams exactly how you want them.
  • Path > Simplify. Use this for when a curve comes in with a ton of anchor points, which makes it hard to edit the overall sweep. If you can't reduce the number of anchor points this way without changing the shape of the path, try manually tracing the path: Copy the current path into another layer, change the color so there's contrast, and lock that layer. Then edit the unlocked layer by deleting anchor points and adjusting handles until it's as close as you want to the original path.

Fabric Layout

  • Most fabric you buy will either be 60" wide or 45" wide.
  • For 45" wide fabric, I would assume the 45" dimension will go across the laser bed (since the laser is ~48" wide).
  • For 60" fabric, i would assume the 30" dimension will go from the front to the back of the laser (since the laser bed is ~36" deep).
  • Make sure you know the direction of the grain on your pattern pieces! Pattern pieces meant for 45" fabric will be perpendicular to pattern pieces meant for 60" wide fabric.
    • All fabric has a grain, which is the direction of the primary fibers. It'll be perpendicular to the fabric width. You can test where your grain is by pulling on the fabric. The grain will be the direction of least stretch.
  • If this perpendicular nonsense makes your brain hurt, just lay your fabric out however you want, but know that it'll be harder to nest all your pattern pieces efficiently if you're not making use of the full size of the laser bed.

Tell Jamie to draw some pictures of the 2 layout styles and put them here

To get a rough sense of the layout, make an artboard that's either 30" or 45" wide, and then make it arbitrarily long. This will tell you about how many yards you need. When you're ready to get the final layout, make multiple artboards that approximate the size of the laser bed. I usually have a "work" file that has a single large artboard with multiple work layers, and then multiple "laserable" files that are single artboards ready to be exported to the laser.

Laser Cutting

Preparing the Fabric

  • Ironing: Just like with manually cutting the fabric, you'll want to iron the fabric prior to laser-cutting so that there aren't any huge wrinkles. I recommend using the iron in the Sewing Zone so that your fabric doesn't re-wrinkle itself on the way to the space.
  • Pre-cutting: I have had occasional problems with trying to stuff too much fabric in the laser at once. You'll probably roll up whatever fabric you aren't currently using, but there's a limit to how tall that roll can be before it runs into the laser gantry and causes the gantry to get stuck and make unhappy noises. For this reason, I would advise cutting fabric down before putting it into the laser if you have a lot of fabric. 1 to 4 yards should be ok, but more than that it's going to be hard to arrange. I've also heard that the back of the laser can be removed for a pull-through type setup, but that's not part of the machine capability currently.
  • If you're going to get fancy with iron-on interfacing, iron that on before laser-cutting.

Arranging the fabric on the laser bed

This is the hardest part. Plan to spend a few minutes gently stroking the fabric to smooth it out on the laser bed. If you're doing two layers, sometimes it's easier to pull back the second layer, smooth out the first layer, then put the second layer back on top. You'll probably also have to do some tugging. If you're using a knit, be mindful not to stretch the fabric. Try to use the selvedges to line up the grain square to the laser bed.

The laser bed honeycomb is pretty high friction, which can be good or bad depending on the fabric. Since the laser bed can be dirty, turn the fabric with right sides together (for double layered), or with the right side facing up. The char will mainly end up on the bottom of the fabric.

Synthetic fabrics will melt slightly onto the honeycomb. They're easily peeled up, but if this will be a problem for your design (like delicate/intricate designs on knit synthetics), consider cutting on top of a piece of paper or cardboard. You can also use iron-on interfacing first to stabilize the fabric.

Software settings

Cut Order: If you're cutting an intricate design inside a pattern piece, cut the design first, then the outline of the piece. This will minimize the risk of the piece blowing out of position before the design is cut.

Power settings: Always do test cuts, but for fabric, Power 50, Speed 100 is a decent place to start. There is definitely a sweet spot for melty obnoxious fabric like brocade. If you use too high of power/low of speed, the fabric will melt more and be a pain to pry apart, and the fancy metallic threads will want to bunch up. When you do test cuts, make sure to test a curved cut, as the deceleration on a curve can have a big impact on fabric.

Giant intricate designs: There is a limit to the size of the file that you can send to the laser from the computer, and apparently the Hurricane Cape pieces exceeded that limit. If that happens to you, there is a USB port on the laser itself, you can put the .MOL directly onto the laser.

Laser cutting

Air assist: Fabric has a tendency to blow away if it's natural fiber (it burns and doesn't melt onto the honeycomb) and light-weight. Turn down the air assist until the fabric isn't being violently blown around, but be mindful that the air is what keeps the laser beam from igniting the fabric. If the air is off or too low, the fabric will catch on fire. Make sure to turn the air back to about where you found it when done so that there will be less of a risk of other people's projects catching on fire. If you don't need to mess with the air assist, just leave it at a high level. You'd be surprised how much fabric will stay put with just some weights.

Testing: If you need to do more tests than just the standard test box for alignment purposes, run your full pattern with the lid open. The laser won't fire with the lid open, so you can see exactly what path the laser's going to take.

Future Possibilities

There are so many things I want to do now that I discovered how easy this is. If you get a pattern online, you can laser-cut onto tracing paper or muslin to do cheap, fast fittings. You can modify the vector paths to come up with an altered fit and try it right away. You can design a ridiculously complicated dress (Herve Leger bandage dress, anyone?) and instantly have all the pieces cut out. I might even make a dress version of one of my Voronoi Lamps with fusible interfacing and layers of fabric....