servo motor startup speed

[CowboyBob]

1 hour ago, GerryR said:

Is that motor shaft speed or gear reducer output speed?

Shaft speed

[GerryR]

3 hours ago, CowboyBob said:

Shaft speed

So, with a 5:1 reducer you would have 30 stitches per minute, or 1 every 2 seconds, as your slowest speed: am I interpreting this correctly?  If so, there should be plenty of starting torque to pierce most any thickness of leather.

[CowboyBob]

12 hours ago, GerryR said:

So, with a 5:1 reducer you would have 30 stitches per minute, or 1 every 2 seconds, as your slowest speed: am I interpreting this correctly?  If so, there should be plenty of starting torque to pierce most any thickness of leather.

The 150 is w/o a reducer,the motor will run slower with one since there's less friction.Our box style reducer has a 4:1 ratio & the speed is 15 RPM sewing 20 oz of leather on a CB341,so motor is down to 120 RPM.

[Gump]

Fibersport; What machine are you putting a servo on? Sewing at 1.7 stitches a second is a snails pace. You will grow tired of that really fast. These new servos have full torque at minimum rpm. I have the same variety of servo on Techsew 3800/cb 3200, and I removed the speed reducer as it wasn't necessary. It eases the needle through 1/2" vegtan for fun. My Artisan Toro also has a digital servo with 5:1 reduction that sew 7/8" without a hesitation. I can't compare them to a Consew servo, but I don't have a lack of torque problem.

[fibersport]

It's a Pfaff 545.  I already have a servo motor on it but it's a few years old and probably a low end one.  I'm not looking to sew at that speed, I just don't want to have the motor start turning at a high speed for the first few stitiches.  I built a speed reducer that is about a 5:1 ratio which really helps, I'm just looking to see if I can make it any better in terms of a slow ramp up speed.  The higher the max speed setting on mine, the less control I have on my ramp up speed.  It's like anything else, the less you spend the less you get, so my less expensive servo motor gives me less control.  

[Gump]

At 5:1 ratio, a sewquiet 6000 will give you 40 stitches per minute minimum. Thats 1.5 seconds per stitch, that is slooooow.

[fibersport]

Again, I'm not looking to maintain the slow speed, only to have a slow ramp up speed, 

[GerryR]

25 minutes ago, fibersport said:

Again, I'm not looking to maintain the slow speed, only to have a slow ramp up speed, 

Not trying to belabor an issue, (and I don't have any financial interest in 3-ph AC VFD's), but this is where 3-ph VFD's / motors excel over other systems.  You can set accell / decell speeds in Hz-per-seconds or some systems use time-in-seconds up to your programmed or foot pedal top speed.  One Hz per second would be a very long accelleration time.  Just something to think about.

On the system Gump is talking about, your foot would control the accelleration time from a very slow start, so either method should do what you want.  

[CowboyBob]

2 hours ago, fibersport said:

Again, I'm not looking to maintain the slow speed, only to have a slow ramp up speed, 

I checked the speed again you can ramp it up slowly with your foot anywhere from 25 to top speed of 410

[dikman]

The big problem with using a 3-phase motor/VFD combination, in this particular case, is finding/making a suitable foot-operated pedal to control it (not as simple as you might think). I just tried to make one for a speed controller for a small sewing machine motor and gave up.