A few days ago, I received a new Sewquiet 4000 servo motor from Reliable Corporation. This motor is designed as a replacement for a conventional clutch motor for industrial sewing machines and has both pluses and minuses compared to the previous model (the Sewquiet 3000) and to clutch motors.
The unit weighs about 24 pounds. It has the usual hinged mounting frame for attaching to the bottom of the sewing table and tensioning the pulley belt. On the bottom of the motor is a small control box with a power switch, a ready light and a four-position speed control. On the back is a switch that controls which direction the motor rotates. The control box comes wired to plug directly into a 110V outlet. At the end of the motor is a lever that attaches to a normal treadle rod.
The speed control switch sets the top speed of the motor. Setting #4 (all the way counter-clockwise) yields a top speed under load of about 4500 RPM. Setting #3 gives a top speed of about 2500 RPM. Settings #2 and #1 are progressively slower. The actual speed is set by depressing the treadle. Light treadle pressure gives very good control of slow speeds up to about (I am guessing, not measuring) 1/3 of top speed. Past that point, motor speed abruptly changes to top speed.
I have about four hours of use with the motor after installation on my Juki DDL-8700, so these are early impressions.
What I like:
Unlike many servo motors, including its predecessor, the Sewquiet 4000 does not buzz at slow speeds. Motor noise is minimal and more or less proportional to motor speed. Like all servo motors, and unlike clutch motors, it is dead silent when not in motion. My Juki is now as quiet as most household machines, at all speeds.
The Sewquiet 4000 has excellent slow speed control, better than most servo motors and vastly superior to a clutch motor. Also better than the typical household foot pedal speed control. This is by far the nicest industrial motor I have ever experienced for slow detail sewing.
It is easy to adjust the “dead band” of free treadle motion before you get a noticeable spring pressure. You can make it very predictable how it responds when you first put your foot on the treadle, and how far you have to press the treadle to get the motor turning.
What I don’t like:
When the Sewquiet 4000 is switched off (using the power switch or unplugging it), its control box retains enough energy to sew another stitch or two. The predecessor Sewquiet 3000 did not do this: off meant off. This bothers me as a potential safety problem, since unlike a clutch motor there is no audible indication that the switched off servo motor might still have some “oomph” to it.
I called Reliable technical support about this. They immediately tried a machine in their facility and it also had enough excess energy to sew a half stitch after being switched off. They have apparently received no complaints about this, but it bothers me.
The transition between low-speed and top-speed is very abrupt. And if you hold the treadle “just so”, you get speed surges between high and low speed which I find extremely disconcerting. The effect is like a very grabby clutch, where you are nicely slipping the clutch to get partial speeds then WHAM it locks up. Reliable technical support confirms that this is the designed behavior. For full-bore production sewing this makes sense, but I usually do not sew at 4500 stitches per minute.
The precedessor Sewquiet 3000 had another knob which controlled how motor speed responded to treadle position (the “pickup” response). The Sewquiet 4000 has a fixed pickup that definitely takes some getting used to. After an hour or two of sewing up some samples, I was getting used to the pickup with fewer unexpected transitions to “hyper-drive”, but would still prefer a pickup that gave a hint about the near-by transition to full speed.