Development of best servo motor for leather sewing machine

[kgg]

54 minutes ago, GerryR said:

12 coils will distribute the heat better, but it is still within the confines of the motor housing.

Agree.

One of the members on the forum has a brushless servo motor that has a fin system moulded right into the small pulley. I am assuming that was done to try and help keep the housing cooler. Lets face it brushless servo motors are designed to last too as long as the warranty period and utilize a design to save on manufacturing costs.

I doubt any brushless servo motor will ever come close to lasting as long as the big old heavy clutch motors that weight about 40 lbs. with real metal housings verses about 18 lbs of plastic and aluminum. Sort of like a Zippo lighter lasting a life time verses a BIC lasting a week or two. 

kgg

[Cumberland Highpower]

1 hour ago, GerryR said:

Power is power, so if it requires a certain amount of power to pierce the leather, both motors, whether 9 coil or 12 coil, will generate the same amount of heat.  It all depends upon the heat management of the motor design, so "should get rid of the heat better" is up for grabs until the longevity of the motor is proven.  12 coils will distribute the heat better, but it is still within the confines of the motor housing.

Actually there are a few other bits at play, such as the elemental composition of the iron used in the stators.  Chinese motors often use some really low quality sheet steel for that.   You'll get oversaturation and more heat as a result.

I'd gamble an Efka motor generates a good bit less heat to dissipate based on the Watt rating than any of these bargain Amazon servos.

Seems like I remember a guy on ebay selling some 4:1 speed reduction bolt on (planetary?) gearboxes for servos.  I don't remember too many details other than they were somewhere around $100.  Anyone here have one or try one out?

Edited July 16 by Cumberland Highpower

[GerryR]

15 minutes ago, Cumberland Highpower said:

Actually there are a few other bits at play, such as the elemental composition of the iron used in the stators.  Chinese motors often use some really low quality sheet steel for that.   You'll get oversaturation and more heat as a result.

 

Yes, I stated that both motors would generate the same amount of heat and meant power; that is where the heat management comes into play, and like you stated, the choice of materials used.

[Wizcrafts]

On 7/5/2025 at 10:06 PM, CowBoyOUTLAW said:

WOW, are you servo engineer?
Few people can talk about optical controls deeply. Now we use 600 line encoder, the minimum speed on CB4500 is about 10 stitch per minute. If use 1200 line encoder, in theory the speed can down to 5 SPM.

I'm not an engineer; just a knowledgeable user. Optical speed control is not new technology. I've had volume pedals for my pedal steel guitars from decades ago that used a small light bulb or LED to emit a focused beam against a photo-resistor. The sensor/resistor controlled the signal transfer between the input and output jacks. When backed off, heel down, a small phenolic board blocks the light beam, so there is no output at all, yielding full resistance. As one moves the pedal with his toe down, the phenolic board is brought out of the line of light, gradually increasing the amount hitting the sensor, decreasing its resistance. This results in an extremely smooth transition from zero to the maximum volume that the volume pedal is able to transfer to the amplifier (~95%). My current electronic volume pedal is still optically controlled, but uses a variable density filter instead of a solid piece of board. It has a small amount of amplification so that it doesn't lose any signal at full volume.

Fast forward out of the world of pedal steel guitars and into the world of digital servo motors on sewing machines. In 2011 through 2013, our main 441 machine suppliers sold them with a digital motor that had a 45mm pulley. Some started with a jolt at 200 rpm. Others started with a similar jerk at 100 rpm. So. somebody took their motor apart and saw that it was optically controlled, just like my old volume pedals. That person had a good printer and some transparent "paper." He went and printed out some strips that had a varying density of gray ink, smoothly ranging from 100% black to 100% transparent. By playing with the spread of the printed filter, he came up with a simple optical filter that anybody could install inside their motor. He sold them through the forum for a modest fee. I installed one in my Cowboy cb4500, in my buddy's Cobra Class 4, and on a Techsew I acquired a little later. This modification worked 100% as designed. The only thing that caused a variation was if the machine hit a bump in the floor when I moved it to sew a log project (webbing strapping or a long rifle case). It was a simple matter to reposition the filter, which I later glued in place.

So, is this new KineDyne motor optically controlled? If so, have you considered using an optical variable density light filter to control the speed? I think I still might have a spare filter in an envelope. Bob Kovar might still have a couple left. We could probably get one to you to experiment with. I'm pretty sure there is a variable density filter in my original digital servo from my cb4500, which is on the floor in a closet. If you try the variable density filter control system and perfect it, then secure it to survive shipping and man-handling, you will be able to offer a motor that smoothly transitions from absolute zero through the top speed as set on the control panel, with good low speed torque from the numerous coils.

A side benefit of having a digital servo motor running this slowly is that there seemed to be much less heat being generated. Originally, we felt the heat as we sewed at 5 to 9 stitches per second. It was even running hot at slower speeds due to it starting at 200 rpm. I also disliked the non-linear speed change which ramped up after I pressed down on the pedal. It wasn't an instantaneous change that I preferred. I grew up using clutch motors on sewing machines, and still do on a few of them.

I have since moved away from touchy digital servos to the analog motors sold by my Cowboy dealer. They contain brushes and replaceable carbon signal transfer blocks on springs. They reliably start at zero and speed up linearly as I press my toe down; just like my volume pedal on my steel guitar.

[GerryR]

Those optical filters are nice, but they defeat the purpose of starting the motor at the so-called required minimum speed, which is probably not necessary in most instances.

Edited July 16 by GerryR

[AlZilla]

1 minute ago, GerryR said:

Those optical filters are nice, but they defeat the purpose fo starting the motor at the so-called required minimum speed, which is probably not necessary in most instances.

If you wanted a certain minimum speed, couldn't you just start the gradation at that point? Then have a smoother ride up to max?

[Wizcrafts]

5 minutes ago, GerryR said:

Those optical filters are nice, but they defeat the purpose of starting the motor at the so-called required minimum speed, which is probably not necessary in most instances.

I didn't find that. I sewed with the optically modified motor on my cb4500 and a couple of walking foot machines.  They worked very well. The Cowboy had a 3:1 reducer. My long arm Singer machine fed directly from the motor's 45mm pulley. They had no hesitance to start turning over.

[GerryR]

31 minutes ago, AlZilla said:

If you wanted a certain minimum speed, couldn't you just start the gradation at that point? Then have a smoother ride up to max?

Yes, but that would defeat the purpose of a softer start, which you are trying to achieve.

[Cumberland Highpower]

4 hours ago, GerryR said:

Yes, I stated that both motors would generate the same amount of heat and meant power; that is where the heat management comes into play, and like you stated, the choice of materials used.

It's easy to mistype these days, especially with all the autocorrects, I do it all the time! 

A person could have an oversaturated motor w/stators made from Chinese bean can steel that draws 600W and a quality built Efka or Misubishi that draws 575W and actually have "more" output shaft power put out by the later.  

When it's a $200 servo vs one a few times more expensive, nobody really seems to care though.   I bet all the ROC made clutch motors I have aren't as efficient as my old Belgian and USA made versions, but I don't seem to care either.

I'm just rambling on GerryR.

Edited July 16 by Cumberland Highpower

[GerryR]

Keep rambling, good info!!