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STITCH LENGTH VS. SPEED REGULATION

December 4, 2001

The newer and newer entries in the "stitch regulator" arena sometimes confuse wannabe customers, as some recent posts show. One confusion is the name of the feature itself. There are two different methods to automatically control the motor movement, both called "stitch regulator". Although both methods use sensors and electronic motor contollers, there are considerable differences between them:

- SPEED REGULATION is the method when the motor is run continuously, but with a varying speed, that is based on measurements of the speed with which you move the sewing arm. Machines with speed regulation run smoothly and keep fairly even stitches when the arm is moved with medium to high speed. There is a slight delay in the regulation, which may be noticed from stitches piling up when the arm is stopped abruptly.

When the arm is moved slower, the regulator maintains the same continuous needle movement, with about 50% of the time the needle being in the fabric. This may cause noticeable drag on the needle. On the other hand the motor will lose its strength at lower speeds, and unless a special method, "servo control" is used, the motor may not be strong enough to move the needle through the fabric.

The speed regulation does not require learning a different arm movement technique. Those who are used to the constant speed technique will find that they can relax at turns and points of the patterns and speed up more on smoother curves, and the stitches will remain even.


- The STITCH LENGTH REGULATION differs in the way both the measurements and motor control are done. Instead of measuring the arm moving speed, the controllers measure the distance the arm travels. The motor is kept steady, with the needle above the fabric, until the selected stitch length is reached. At that moment the electronic control starts the motor with its maximum speed, moving the needle in and out of the fabric in about 1/20th of a second. When the needle returns to the top the motor is stopped again.

One very noticeable effect of the stitch length regulation is the hammering of the motor, the "firing stitch", as Mr. Gammill called it. Due to the firing stitch the machine may bounce, and run "choppy" at medium to slow speed. As the arm is moved faster, the firing stitch becomes smoother.

The real advantage of the firing stitch method can be experienced at low speed quilting. No matter how slow the arm is moved, the stitch still will be completed in about 1/20th of a second, then the needle will stay above the fabric eliminating any drag or needle flexing. The force of the needle piercing will remain the same even at very slow speed.

To reduce the hammering at slow quilting, the Precision Quilting mode was added to the IntelliStitch design. The PQ reduces the speed of the firing stitch, thus making the machine run smoother at slow speed, yet it maintains the
same stitch length regulation method.

As opposed to the speed regulation, the firing stitch method requires a different arm moving technique. It takes time for the motor to speed up from its steady state, so you need to avoid sudden changes in speed or direction, for it will cause occasional long stitches. Since the constant speed technique does require sudden changes, those
who are used to that technique need to learn the method of slowing down and gradually speeding up at points or corners of the patterns.


When shopping for a machine with "stitch regulator" you need to match your quilting style with the stitch regulation method. The best way is to try the machines, so you will not be disappointed later with the choppiness or the dragging of your new machine.