Instead of ranting and risk offending somebody I am going to post something educational about thread tension assemblies and why you might want to pay attention to this when you are buying a quilting system or if contemplating the superiority of your current system.
Thread is tensioned in one of two ways on most any sewing machine: Rotary tension or plate tension.
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| Plate type tension: thread is pressed between plates H |
Plate Tension: This is the most common way of tension thread on a domestic sewing machine. Tension is controlled by pressing thread between two metal plates. This is a simple tension device, it does not require a pre-tensioner to work, though a pre-tensioner will improve it a bit, and it is really easy to do intermittent tension with it, and it is easy to thread.
A word about intermittent tension...All domestic machines have this. Try it out, when your presser foot is up the tension is loose, when the foot goes down the the tension tightens up. That is intermittent tension.
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| Plain ole' plate tension assembly |
Back to plate tension... plate tensions work as a function of thread thickness. If you have thicker thread you need to back the spring off and open the plates, if you have thinner thread you need to close the gap in the plates. Because of this low quality thread with inconsistent diameter will result in slight variation in tension, also debris or "fuzz" from thread that gets caught in the plates will cause tension issues. One of the most common problems I see with sewing machines is a piece of broken thread caught between the tension plates which leads to poor tension control.
A long arm will suffer from these same problems, plus one more, jumping the plates. If a long arm is not pre-tensioned properly what can happen is that the thread comes out from between the plates and all tension is lost, but you don't know this until you roll your quilt, then you swear under you breath and go looking for a seam ripper so you can de-quilt your mess...ask me how I know.
A word about pre-tension...this will almost always be a plate type tensioner before the main tension assembly, its purpose is not to tension your stitch, but to ensure enough tension on the thread so the main tension assembly functions consistently. Pre-tension is usually really light and often makes you wonder why it is there at all. Jump your plates once and you will appreciate pre-tensions subtle awesomeness.
Rotary Tension: This is rarely seen on domestic sewing machines, but they are common in industrial machines, and some long arm machines. Tension is controlled by applying pressure to a disc the thread is spinning on. Proper pre-tension is important in a rotary tension
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| Rotary tension assembly: The slots in the disc help grip the thread |
Unlike plate tension, rotary tension is not effected by thread diameter. As long as the thread is spinning the disc the same tension is applied regardless if it is 80wt silk, or 40wt poly. This also means less stress on the thread because instead of crushing thread between to plates we are applying pressure to the rotating disc. Kinda like the reason we have disc brakes instead of applying brake calipers to tires.
Why is rotary tension all but absent in domestic sewing machines? It is not as easy to thread as a plate tensioner, and plate tension has worked fine for a 100 years so why change now. Most long arm machines are based on domestic machine design and this is the reason that you will find plate tensions on long arms.
Rotary tension is a superior technology for long arm applications and you will find that any long arm that has a reputation for consistent tension and the ability to run any thread will have a rotary tension, even if everybody else is drinking the plate kool-aid.
Okay that was a long but hopefully informative post feel free to comment or question below.
