Soft start for servo motor

[Edsbear]

Hi,

I have a Brother LS-B837 industrial machine and added a sevo motor which is great apart from when starting to sew, the motor doesn't come in slow and smooth like the old clutch motor used to. When its running its slow enough but would like a smooth start instead of it jumping straight into the slowest speed which is quite slow.

Does anyone know of a mod that will acheive a smooth slow start like a clutched motor does

Thanks

[fibersport]

1) change the motor pulley to the smallest you can find, usually 45mm

2) go with a larger pulley substituted for the handwheel

3) speed reducer

4) I tried 1 and 3 above, ended up getting a different servo motor that would start at 50 rpmand not 200 or 300, game changer -

[Edsbear]

Thanks for the info, does your new motor creep in like a clutch motor

[kgg]

2 hours ago, Edsbear said:

When its running its slow enough but would like a smooth start instead of it jumping straight into the slowest speed

The main difference is a clutch motor is running at full rpm's (1450 or 1750) as soon as you turn the power on and like a manual transmission in a vehicle you ease the on clutch. The servo motors don't spin until you depress the "go" pedal. All servo motors have a "startup jump" with the brushless typically having a more noticeable "jump" then the brushed servo motors. You can reduce this somewhat by reducing the pulley on the servo motor, installing a speed reducer and buying a better quality servo motor. Typically the more internal coils the servo motor has the less "jump" experienced but check the startup rating of the servo motor a lot of the cheaper ones have a 500 rpm rating.  

kgg  

Edited 22 hours ago by kgg

[Constabulary]

believe it or not - I run a JACK 563 servo (actually 2 of em) for many years and just recently I bought a fxcking cheap Chinese servo (for under 70€ few month ago incl shipping) and it behaves and performs way batter than the Jack - not kidding. It starts at 200 rpm and I can dial down to 100 but than it makes strange sounds.

https://de.aliexpress.com/item/1005007257363563.html

price on my side of the pond is 88.99€ now incl shipping (Warehouse in Germany).

The Jack quality is better, thats for sure but this cheap sucker just performs better.

I however have added a speed reducer too, better too slow than too fast and you still have enough end speed. But to each his own...

Edited 21 hours ago by Constabulary

[AlZilla]

I have read on here that the brushed servos start from zero and have better low end torque. Verify this for yourself! 

I have a few brushless servos, one of which starts at 100 rpms. With a 45mm motor pulley, a 6"/2" speed reducer and the stock 3.5" machine pulley, I have a bottom end of 11 stitches per minute. You'd never really sew that low but it gives me a slow start with good control and torque.

Still, the brushless motors increase in increments of 100 rpms, whereas the brushed versions apparently increase smoothly. 

When I need another servo motor, I think it'll be a brushed version.

[fibersport]

11 hours ago, Edsbear said:

Thanks for the info, does your new motor creep in like a clutch motor

Not exactly creep but the ramp up speed is so slow it almost feels like it.  The creep you mention is what I would call slip.  With my motor and synchronizer, it's set up where I can get one stitch per tap on the treadle.  I think buried down in the settings, I can adjust the speed as well.  I don't want others to think I'm promoting one brand of motor, but if you search in my previous posts and then do a little research, you can find out more details from others to see the motor in action.  After that, then you can make your own decision.

[Wizcrafts]

16 hours ago, Edsbear said:

Hi,

I have a Brother LS-B837 industrial machine and added a sevo motor which is great apart from when starting to sew, the motor doesn't come in slow and smooth like the old clutch motor used to. When its running its slow enough but would like a smooth start instead of it jumping straight into the slowest speed which is quite slow.

Does anyone know of a mod that will acheive a smooth slow start like a clutched motor does

Thanks

If you can't tame your digital servo motor, consider replacing it with an analog model that has brushes. The Consew CSM-550 is a perfect replacement. I use this type of servo motor, under different brand names over the years, on all of my walking foot machines, including my huge Cowboy cb4500. Servo motors with brushes like the CSM-550 start at zero rpm, but with very low torque at the minimum speed setting. They gradually increase their starting torque as you turn the speed knob a little higher. Once in motion, you can back off to maintain your preferred speed. Adding a speed reducer can double or triple the torque. Machines with this motor and a speed reducer can start turning over at less than one stitch per second and punch through whatever is under the foot/feet.