servo motor startup speed

[GerryR]

7 minutes ago, dikman said:

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.

It really isn't that big an issue.  I have a Pfaff 1221 machine that I refurbished; it came without a foot pedal.  For ~$30.00 I bought a used Tig welder foot pedal (I have a TIG welder, so knew how they were made) which has a pot and a microswitch inside; the Pfaff requires a pot, but I also used the switch to my advantage.  The VFD's require a pot.  It was very easy to convert to run the Pfaff, and it is way more substantial than the plastic junk that passes for foot pedals these days.  I only offer these suggestions so others realize that there are options;  you don't always have to follow the "party lines."

[Wizcrafts]

The Consew analog servo motor sold by Toledo Industrial Sewing Machines is probably all you will need. It can be ordered with a pulley as small as 45mm. This is less than 2 inches diameter. I'm pretty sure that the pulley on your Pfaff balance wheel is at least 4 or 5 inches diameter, giving you more than 2:1 speed reduction/torque multiplication. You can install it yourself. Your local hardware or auto parts store will have a selection of type 3L v-belts to connect the motor and machine and leave 1/2 inch of slack in the center. The knob on the front of the motor limits the top speed and can be changed on the fly as you sew. I do it many times. I might start with a slow speed setting until I get to a long seam. Then, I reach down and spin the knob and it's off to the races. Still, it is possible to slow down the motor gradually from the top speed setting. It's just not as smooth on the ramp up compared to a much lower setting.

[Gump]

Get a treadle machine.

[dikman]

GerryR, I wasn't aware that TIG pedals had a pot inside, I'll keep that in mind, thanks.

[GerryR]

1 hour ago, dikman said:

GerryR, I wasn't aware that TIG pedals had a pot inside, I'll keep that in mind, thanks.

A pot and a switch.  The switch initiates the arc, and the pot regulates the welding current.  The pot can be used directly for the Pfaff machines with the built-in speed control electronics (minor mod), like the 1200 series, or you can install a triac motor speed control and use the pot to control the triac output.  Many options!

[fibersport]

Since this was such a popular p[ost, I thought I would give an update.  I decided to take the plunge and upgrade my existing servo motor to the Consew 550-1 analog servo motor from Cowboy Bob.  I also took Wizcrafts comment and ordered it with a 45mm pulley.  I received it yesterday and disappeared to the basement for the evening.  I couldn't install it with my speed reducer without drilling holes in my table to I decided to try it motor only.  That required a new belt so I picked that up this morning and got it all put together.  

I have to say it gives me the ramp up speed that I was looking for.  It's nice and slow which allows me to back tack at the start and not really feel like I need 3 hands to get things started.  It's nice and quiet but it does seem to have a little less torque than what I'm used to - granted the other servo motor I had started at a higher speed and really could not be started slowly.

Overall I'm very happy with it.  Down the road I may reinstall my speed reducer just to see if that helps with the start up torque.  For now though, I'll concentrate on enjoying nice smooth starts.  Next on the learning curve is using the max speed settings to see how that affects things.  Thanks to everyone for their comments and sharing their experiences.

[Wizcrafts]

1 hour ago, fibersport said:

It's nice and quiet but it does seem to have a little less torque than what I'm used to

Turn the speed dial up a notch. You'll still be able to feather the pedal for slow speed, although it will be a little touchy until you get the hang of it.

1 hour ago, fibersport said:

Down the road I may reinstall my speed reducer just to see if that helps with the start up torque.

A 1:2 speed reducer is also a 2:1 torque magnifier.