Development of best servo motor for leather sewing machine

[GerryR]

7 hours ago, CowBoyOUTLAW said:

Our motor do not use buit-in gear box. No need of it

So, you have a high torque, slow start-up speed motor, which means you have a special controller for it (?).  What are the power requirements for it?  How big is the motor?  What are the output shaft dimensions?  What are the mounting requirements for the motor and controller?  Is the speed controlled by a foot pedal or a dial on the control box?  Do you have provisions for a position stop (needle up-dwn)?  These are just some questions I have for any new system I would consider.  It sounds like your system already exists, so should be easy to answer.   

[dikman]

Gerry, my understanding is that it's simply a Hightex 750w servo with 12 coils to give it lower startup speed and low-end torque, nothing more (other than a higher price because of the extra coils). I still believe that unless someone goes down the path you have to obtain effective slow-speed control and torque then a speed reducer is needed with a servo used for leatherwork (particularly with the big harness stitchers).

[GerryR]

27 minutes ago, dikman said:

Gerry, my understanding is that it's simply a Hightex 750w servo with 12 coils to give it lower startup speed and low-end torque, nothing more (other than a higher price because of the extra coils). I still believe that unless someone goes down the path you have to obtain effective slow-speed control and torque then a speed reducer is needed with a servo used for leatherwork (particularly with the big harness stitchers).

I know, I just wanted him to say it.  I still prefer VFDs with 3-ph gear motors over DC systems. JMO, YMMV.

Edited July 15 by GerryR

[AlZilla]

This is usually such a friendly place. He's made no secret that he's the marketing guy, not the tech guy.

Would torque increase the same way speed reduces? As in 3:1 on speed equals 1:3 on torque?

I'm definitely skeptical that a motor in this size range can achieve the same increase as 750 Watts with a 1:3 speed reducer.

[dikman]

Its ONLY advantage over other servos is the claimed startup speed of 50 rpm. Just how practical that is in the real world of leather sewing I don't know. All I do know is that with my limited abilities I need to be able to sew slow and know that there is enough torque to punch through heavy leather - which means a speed reducer.

[AlZilla]

10 minutes ago, dikman said:

Its ONLY advantage over other servos is the claimed startup speed of 50 rpm. Just how practical that is in the real world of leather sewing I don't know. All I do know is that with my limited abilities I need to be able to sew slow and know that there is enough torque to punch through heavy leather - which means a speed reducer.

I've got a machine with a servo that does 100RPM startup and a speed reducer. Today I counted 14 stitches in 30 seconds.  50RPM would give me 7!

But, I'm slow enough.

[GerryR]

Torque from a motor depends upon current in the windings and the number of poles (basically, I'm not a motor expert) so without a speed reducer of sorts, the motor has to be very robust to maintain high torque at slow rpm and cooling is paramount.  The speed reducer gets the motor rpms up where cooling is better, current is lower and torque is higher because of the gearbox.

As far as the OP is concerned, I don't understand why he can't just tell us his new motor/system specs; why all the mystery?

[dikman]

http://hightex-solution.com/blog/technology/2024/0425/315.html?1714026959

This is the Hightex site with info on the 750SH model, which I assume is what we're discussing here. There is a video at the end showing it in operation. It does appear to have reasonable torque at slow speed, but no better than running a cheap servo and speed reducer. For a factory maybe it's an advantage not to have to fit a speed reducer so paying a higher price for a servo may make sense? I said earlier though that for the hobbyist is it cost effective? Not for me, particularly with more than one servo, if a cheapy servo dies I'll simply replace it with another cheapy servo (and save $300+).

Interestingly, the link shows a 9-coil motor. Gerry does raise a point about heat generation when running a motor very slow.

[kgg]

My experience with a cheap digital brushless servo motor that came with my TSC 441, 16" cylinder arm clone has a speed range of 500 - 5000 rpm on it's 800 watt, 9 coil and with no reducer pulley on the machine:

Calculated:

1. Top speed of the hand-wheel pulley should come in at 156 rpm using:

i) a 160 mm hand-wheel pulley size,

ii) a 50 mm motor pulley

iii) with the motor speed set to the minimum speed of 500 rpm's. This particular servo motor is a 800 watt brushless 9 coil servo motor with a speed range of 500 to 5000 rpm's.

Measured:

i) The hand-wheel pulley measured out to be 159mm.

ii) The small pulley at the motor measured out at 49mm.

Measured results:

i) with 500 rpm's showing on the controller screen

ii) with the foot pedal fully depressed the rpm's with my digital tachometer showed 154.5 rpm's with no material under the needle

iii) with the foot pedal feathered to get the minimum hand-wheel pulley speed the digital tachometer showed a low rpm reading of 61 rpm's with no material under the needle.

From that I can assume a no load ramp up speed of 61 rpm's.

I'm assuming the 50 rpm speed they are quoting is done in a similar manner. 

6 hours ago, dikman said:

Interestingly, the link shows a 9-coil motor. Gerry does raise a point about heat generation when running a motor very slow.

With everything being equal a 12 coil should get rid of the heat better then a 9 coil operating under the same load conditions.

kgg

 

[GerryR]

6 minutes ago, kgg said:

 

With everything being equal a 12 coil should get rid of the heat better then a 9 coil operating under the same load conditions.

kgg

 

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.