Alrighty...I'm by no means an expert at this technique, and to be quite honest, this was my first attempt at machine smocking. I'm working my way through my sewing machine's manual, and I thought that this would be a fun technique to try out.
I'm sure that most of you have seen the beautiful hand smocked dresses. Hand smocking a dress involves pleating a dress, and then hand stitching or embroidering your design onto the gown. Recently I've seen some smocked baby dresses in the stores, and seeing them filled me with a desire to try out a simpler approach to smocking.
Machine smocking a piece of fabric involves gathering the fabric rather than pleating it. Gathering rows are sewn 3/8" apart along the smocked section of the material.
Once the gathering rows are sewn, the fabric is gathered as uniformly and tightly as possible by pulling the bobbin thread. You can see that my gathers aren't perfectly straight. You can pull the gathers slightly to straighten the "pleats" a bit. It's important that your pleats are uniform, as it will make the stitching process go much smoother.
Once your "pleats" are made you can press the gathered material so that it sits at relatively the same height, and feeds through your machine nicely.
A look at my pressed "pleats".
My sewing machine manual lists three separate decorative stitches that will work with smocking. All of the stitches involve some sort of zig zag pattern. The angled stitches allow you to connect your pleats, and also allows for greater stretch in the garment.
Once you have selected your stitch you can adjust the stitch width and length to your desired size.
My sewing machine requires the monogramming foot when smocking. Center your needle between the gathering rows, they will act as a guide to ensure straight rows.
I found that it was helpful to maintain a consistent speed when using my smocking stitches. Any irregularity in speed would effect the stitch quality. With my machine a slower speed was better. You can see in the photo above that there are places where the stitching doesn't quite match up, often in places that my gathers are not as uniform.
Once you have smocked between each of your gathering rows, you can pull (or pick) out your gathering stitches. You will be left with rows of smocking that are both decorative and functional (proving stretch). Using machine smocking you can avoid pleating and hand embroidering a garment. I still prefer the look of a hand smocked garment, but I won't be doing much of that in the near future.
If you'd like more information on hand pleating or hand smocking these are some great resources.
Hand Pleating Fabric
Smocking by Hand