How a Sewing Machine Stitches
When a seamstress is completing a project, she completes a multitude of tasks to get the job done. The act of stitching requires both her skill and the use of an industrial sewing machine. Home machines can’t handle the speed and strength needed for industrial production, so most fashion designers and manufacturers use sewing machines on a regular basis. Understanding how these machines function, and how the models all differ, is paramount for anyone who sews.
This type of weaving involves complicated interlocking movements between two or more pieces of fabric. The machine has two separate arms, called the sewing needle and the bobbin case. When the trigger is pressed and the machine is activated, the needle and bobbin case are alternately pulled. This creates the weaving motion where bobbin thread and needle thread interlock and make a tight secure stitch. The operators guide the fabric as the machine moves, but the sewing is all done by the needle and bobbin.
Presser Feet
The presser feet of a sewing machine increase the versatility of the machine. Different presser feet are used depending on the level of detail or the number of seams. The straight stitch foot is the most basic, allowing for one stitch at a time. Other presser feet include the zipper foot, rolled hem foot, and the invisible zipper foot, among others. Using different presser feet along with tools such as basting spray and quality fabrics helps to control thread tension and improve the speed of operation.
Adjusting the Thread Tension
The thread tension determines the quality of a stitch. Too much tension can cause the fabric to be pulled too tight, and too little tension can cause the thread to be pulled too loose. For that reason, adjusting the thread tension correctly is essential for successful sewing. Experienced sewers adjust the tension of the machine with each type of fabric they use. For instance, heavier fabrics usually require more thread tension, while lighter fabrics may require less.
Needle Selection
The large range of needles available for a sewing machine is what makes the machines so versatile. Needles are designed for different fabrics, thread weights, and levels of detail. Choosing the right needle for the job is important, as ineffective needles can cause skipped stitches, broken threads, and tears. Basic needles such as the universal and jersey needles are versatile, however, for more detailed tasks such as quilting and embroidery, needles with a large eye are recommended.
Feed Dogs
The feed dogs, or teeth on the outer part of the bed of a sewing machine, move the fabric along as the stitches are created. As the trigger is pressed down and the machine is activated, the fabric is moved forward and then locked into place at the start of each stitch. This allows the fabric to be handled easily and the tension to remain consistent. This also helps to maintain a consistent stitch length from the beginning to the end.
Bobbins
The bobbin is the small spool of thread that sits beneath the needle plate at the base of the machine. To create a stitch, the needle pulls the upper thread down through the fabric and a bobbin provides the lower thread. This creates a secure stitch. Winding the bobbin is a simple process and the modern machines come with a winding system that winds the bobbin with ease. Changing the bobbin is also simple, just remove the existing bobbin and put a fresh one in its place.
Stitch Length
Various stitch lengths can be achieved on a sewing machine depending on the material and preferred seam. Most machines allow you to adjust the stitch length setting. Typically, the stitch length is expressed in millimeters and will increase or decrease depending on the setting. Most garment seams use a 3mm stitch length, while decorative stitches such as topstitching can use a much longer stitch length. To ensure a consistent seam, use a straight stitch foot and adjust the stitch length accordingly.
Motors
The motor of a sewing machine is responsible for providing the power to move the feed dogs and create the stitch. Industrial sewing machines use a motor that is typically more powerful than most home machines. Most machines have an adjustable speed setting or a foot pedal to control the motor. This allows the operator to adjust the speed to the exact need of the project and the fabric.
Needle Points
The needle points play an important role in the stitch formation. The tip, or point, of the needle penetrates the fabric and acts like a hook, pulling the upper thread through the fabric and making the stitch. The point of the needle varies depending on the type of needle being used. Universal needles have a general-purpose point, while special needles such as denim needles have a sharp point. Work with needles that suit the fabric you’re sewing for best results.
Bobbin Winding
Winding the bobbin is important for forming a stitch. To wind the bobbin, the thread is wound in a clockwise direction around the bobbin, with the bobbin in its casing. Doing this helps ensure the stitches won’t knot when the thread reaches the end of the bobbin. Start by filling the bobbin case with the correct thread, then put the bobbin onto the shaft and turn the wheel in the direction of the arrow to begin winding the bobbin.
Types of Machines
The types of sewing machines vary greatly, from industrial and commercial units to consumer-grade machines. Commercial-grade machines feature more powerful motors, industrial-grade needles, and heavier frames and are designed for continuous hours of use. Consumer-grade machines are good for basic sewing, such as stitching hems, mending, and embroidery. Industrial machines offer the most features and speed, making them the most popular choice for garment manufacturing.
Presser Foots
The presser feet are used for a variety of functions on a sewing machine. They help to keep the fabric in place and reduce the bulk of the fabric as it moves through the machine. Different presser feet are suited for different fabrics such as leather, denim, and satin. Presser feet can be changed in a matter of seconds, and some machines have multiple presser feet available. Specialized presser feet such as the zipper foot and darning foot help to make the task of sewing much easier.
Needle Positions
The position of the needle is an important factor in the formation of stitches. Most machines have an adjustable needle position, allowing the operator to move the needle up and down, forward and backward, as well as left and right. This allows the operator to make detailed adjustments and to accommodate different fabrics and materials. The needle position is usually visible on the machine and is adjusted with a lever or a dial.
Threads
Threads are essential for the formation of a stitch. The wrong type of thread can cause skipped stitches, tension issues, and even broken threads. Threads should be chosen to match the fabric type, thread weight, and the task being completed. Generally, polyester thread is the most versatile, although cotton, cotton core, nylon, and poly-cotton blend thread are all good choices for general sewing tasks.
