A longarm quilting machine is designed to make quilting large quilts easy and fun. The obvious difference compared to a traditional sewing machine is the extended arm, giving a much-larger throat space to work in. Longarms come in two main flavours: a sit-down table version; and a frame-based version.
A sit-down longarm machine looks like an oversized sewing machine with a large table for the sewing bed and an extended arm to hold the needle and foot. The machine is stationary and the quilt is moved under the needle much like traditional sewing. The large work space makes it easy to slide the quilt around and the extended throat reduces or eliminates the need to roll up or bunch the quilt to fit within the limited throat space of a traditional sewing machine. The quilter sits in front of the machine, as they do not need to move around to operate the machine.
A frame-based longarm machine works in reverse - the quilt is stationary and it is the machine itself that moves. Instead of a table, there is a large quilting frame that holds the entire quilted top, batting and backing together. The top and bottom edges of the three layers are attached to a series of rollers and held tight, while the sides are clamped together and held snug by means of straps. The needle and throat assembly then moves around the quilt to quilt the top, batting and backing together.
The machine can be moved manually in two directions (up/down and left/right) simultaneously, allowing for smooth curves and intricate designs. Or, it can be computerized and the movements automated by the machine. This allows for precise patterns to be combined and repeated across the quilt at any size.