Development of best servo motor for leather sewing machine

[CowBoyOUTLAW]

We are trying to delvelop excellent servo motor for leather sewing machine, by now we have reach below features/functions:
1. Low speed: minimum speed 50 RPM only
2. High torque:  an awesome 8.6 Nm of torque 
3. Soft Start: make the machine far more manageable
4. “Jog-Dial” (suggested by Italian dealer): ectronical needle positioning
5. Speed Controller: allow you to adjust sewing speed in a second
6. Half Stitch (suggested y Sweden dealer) : micro-adjustment stitch length
7. Needle UP/DOWN position

Any requirement else?

[friquant]

I'm in search of the perfect hundred-dollar servo motor. I've had two motors, both of them good but neither perfect. Here are some requirements that would make me happy:

1. Distance in degrees between needle-up and needle-down should be configurable
2. Motor should use standard 15mm cylindrical shaft with key hole, since a range of aftermarket pulleys are available for this shaft size
3. There should be a long range of travel in the foot pedal between slow and fast
4. The maximum speed should be configurable
5. When the maximum speed is set to something slow such as "900 rpm", the range of pedal travel should be spread across the entire usable range. Meaning you should have to push the pedal all the way to get to 900rpm if 900 rpm is your max.
6. Slow start, ideally, would be a gradual transition up from 0 rpm into some minimum speed. (The slow start I have used before still immediately jumped from 0rpm to 200 rpm, which was not gradual at all)
7. When you tap the gas pedal to ask for one stitch, you should ALWAYS ALWAYS ALWAYS get exactly one stitch. If you give two stitches instead of one now there's an extra hole in the leather that I hadn't planned on. Also, giving more stitches than asked seems like a safety issue.
8. When you heel-tap to ask for the needle to come up, the needle should come up. It must not do a full turn and then come up. That also puts unwanted holes in the leather and seems like a safety issue.
9. The power switch must be in easy reach of the operator
10. The power switch should light up so we can see when it's powered on
11. When the power switch is turned off, the motor should immediately stop. (Safety)
12. Pressing the gas pedal after the power switch has been turned off should have no effect. (Safety)
13. Instructions for operating the manual should be provided in clear language. (I'd be happy to help you write the instruction manual)
14. Ideally one could limit the amount of torque through the control settings
15. There should be no settings visible in the menus that don't do anything.
16. The settings in the menu should be numbered incrementally. No skipping numbers, as this is confusing.
17. Ideally, needle position sensor would stop within one degree each time. Five degrees may be acceptable, but one would be better.
18. If the gas pedal is pressed down while the power button is turned on, the motor should not start. (Safety) Rather, the motor should wait until the gas pedal is released and then pressed anew before motor starting.
19. Ideally, the minimum speed would be 30rpm. This would alleviate the need for a gear reducer for many people. Though if small pulleys are available, 60rpm may be fine.
20. The factory default maximum speed should be something medium slow like 1000rpm. Let the user increase it through the menu if they need it faster.
21. If the belt slips such that the motor has to turn farther than it expected for the needle position sensor to register one complete cycle, the motor should stay in needle detection mode.
22. Ideally, the needle position sensor should have an LED that lights up when the positioner is in the needle-down position. (Makes for easier setup)
23. Assuming this unit comes with a needle position sensor, the controller should have needle positioning enabled by default.

 

 

Edited July 4 by friquant
Added 20-23

[Cumberland Highpower]

I think the Jog dial is pretty lame on a stitcher, unless you have a machine that's a mile's reach to the handwheel.  

LCD screen with multi function display/features is just as lame, confusing to new users and equally annoying to a seasoned one.

So is the typical plastic Chinese made rocker switch/power switch that is good for about 25 cycles.

 

What you need is a basic  quality steel toggle switch on/off, a knob that you can twist for speed control (speed control only) and an option for a positioner needle up/down also controlled by basic toggle switches.    (flip on, twist flip and done)

Those features along with some serious low speed torque and you'd have it.

An additional plus, would be one that can actually be compatible with a speed reducer and positioner at the same time and not throw an error at a 4:1 ratio.

The problem with the modern programmable servos is that they're made to a price point and expected to function with a wide array of machines of various designs.  Lots of functions can be a good thing, but most here that buy a "Cowboy" stitcher or something similar want simple, smooth, easy to use and lots of torque.

Edited July 4 by Cumberland Highpower

[CowBoyOUTLAW]

18 minutes ago, Cumberland Highpower said:

I think the Jog dial is pretty lame on a stitcher, unless you have a machine that's a mile's reach to the handwheel.  

LCD screen with multi function display/features is just as lame, confusing to new users and equally annoying to a seasoned one.

So is the typical plastic Chinese made rocker switch/power switch that is good for about 25 cycles.

 

What you need is a basic  quality steel toggle switch on/off, a knob that you can twist for speed control (speed control only) and an option for a positioner needle up/down also controlled by basic toggle switches.    (flip on, twist flip and done)

Those features along with some serious low speed torque and you'd have it.

An additional plus, would be one that can actually be compatible with a speed reducer and positioner at the same time and not throw an error at a 4:1 ratio.

I am sure the JOG Dial is strong enough. It is essential for for long arm industrial sewing machine that difficult to reach the handwheel. Most long arm sewing machines come with front wheel, but very difficul to turn it. 

But why use speed reducer? The minimum speed of servo motor is 50 RPM only, if use it on CowBoy CB4500 or other Juki TSC-441 type machines, the sewing speed is about 12 stitches only per miniute!!!

[CowBoyOUTLAW]

5 hours ago, friquant said:

I'm in search of the perfect hundred-dollar servo motor. I've had two motors, both of them good but neither perfect. Here are some requirements that would make me happy:

1. Distance in degrees between needle-up and needle-down should be configurable
2. Motor should use standard 15mm cylindrical shaft with key hole, since a range of aftermarket pulleys are available for this shaft size
3. There should be a long range of travel in the foot pedal between slow and fast
4. The maximum speed should be configurable
5. When the maximum speed is set to something slow such as "900 rpm", the range of pedal travel should be spread across the entire usable range. Meaning you should have to push the pedal all the way to get to 900rpm if 900 rpm is your max.
6. Slow start, ideally, would be a gradual transition up from 0 rpm into some minimum speed. (The slow start I have used before still immediately jumped from 0rpm to 200 rpm, which was not gradual at all)
7. When you tap the gas pedal to ask for one stitch, you should ALWAYS ALWAYS ALWAYS get exactly one stitch. If you give two stitches instead of one now there's an extra hole in the leather that I hadn't planned on. Also, giving more stitches than asked seems like a safety issue.
8. When you heel-tap to ask for the needle to come up, the needle should come up. It must not do a full turn and then come up. That also puts unwanted holes in the leather and seems like a safety issue.
9. The power switch must be in easy reach of the operator
10. The power switch should light up so we can see when it's powered on
11. When the power switch is turned off, the motor should immediately stop. (Safety)
12. Pressing the gas pedal after the power switch has been turned off should have no effect. (Safety)
13. Instructions for operating the manual should be provided in clear language. (I'd be happy to help you write the instruction manual)
14. Ideally one could limit the amount of torque through the control settings
15. There should be no settings visible in the menus that don't do anything.
16. The settings in the menu should be numbered incrementally. No skipping numbers, as this is confusing.
17. Ideally, needle position sensor would stop within one degree each time. Five degrees may be acceptable, but one would be better.
18. If the gas pedal is pressed down while the power button is turned on, the motor should not start. (Safety) Rather, the motor should wait until the gas pedal is released and then pressed anew before motor starting.
19. Ideally, the minimum speed would be 30rpm. This would alleviate the need for a gear reducer for many people. Though if small pulleys are available, 60rpm may be fine.
20. The factory default maximum speed should be something medium slow like 1000rpm. Let the user increase it through the menu if they need it faster.
21. If the belt slips such that the motor has to turn farther than it expected for the needle position sensor to register one complete cycle, the motor should stay in needle detection mode.
22. Ideally, the needle position sensor should have an LED that lights up when the positioner is in the needle-down position. (Makes for easier setup)
23. Assuming this unit comes with a needle position sensor, the controller should have needle positioning enabled by default.

 

 

Wow！ So professional!! I need some time to sort out the data. I may reply after my vacation (July 15).

[kgg]

8 hours ago, CowBoyOUTLAW said:

We are trying to delvelop excellent servo motor for leather sewing machine, by now we have reach below features/functions:

Need a basic servo motor that has:

1. Has to have excellent low speed startup.

2. Has to have a 12 coil servo motor or at less 9 coils if it is a brushless electronic servo motor.

3. Give the customer the option of a Brush or a Brushless servo motor.

i) If the customer chooses a Brushed servo motor if the speed dial was able to be mounted on the front of the table rather then on the motor's body they would be perfect particularly for new users. 

ii) If the customer chooses a Brushless servo motor it should be just a simple matter of being able to flip a toggle switch like @Cumberland Highpowerhas suggested rather then having to disconnect the needle positioner plug from the electronic control panel or having to go into the menus.

I prefer the brushed rather then brushless servo motor. No fancy menus or electronics, no needle positioner just set the max speed hit the " go" pedal and sew. I have two brushless servo motors, one on a LS-341 clone and one on a TSC-441 clone and two brushed servo motors, one on a Juki DNU-1541S and one on a Juki du-1181N. The needle positioner on both the Brushless servo motors have been Disconnected. 

The brushed servo motors are much simpler to use for new people and are a lot easier diagnosed when a problem arises.

4. All new features like "Jog" should be options that the customer can choose to purchase if needed. 

I follow the "KISS" rule.

7 hours ago, CowBoyOUTLAW said:

But why use speed reducer?

To reduce startup jump, more controllable sewing speed. However even through you get increase torque it from adding a speed reducer it should be not used as the main reason for installing one as you don't want to over stress internal parts on some class of machines.

7 hours ago, friquant said:

If the gas pedal is pressed down while the power button is turned on, the motor should not start. (Safety) Rather, the motor should wait until the gas pedal is released and then pressed anew before motor starting.

I disagree. Push the "go" pedal and sew.

kgg

 

 

[Tastech]

Perhaps 2 versions of motor 120 volts for north America and 220-240 volts for the rest of the world .

[fibersport]

Talk about having your cake and being able to eat it!  A few thoughts - keep the price comparable to the Reliable or Sailrite (before their price jumped) models so under $200-$250, 12 coil, some sort of trade in program for those that bought analog units from you, made in the USA (that might be tough).  Great thoughts - hope it happens.

[Wizcrafts]

One problem I have had with digital servo motors vs analog servo motors is the jerky start up. I can understand that lowering the startup speed to 50 rpm will be less jerky than a 100 or 200 rpm startup, it will still engage with a hit. Analog servo motors I have start at zero and smoothly increase in speed as the pedal is pressed. There is no jerk at startup on those motors. I have helped convert several Cowboy and Cobra 441 clones and one Union Lockstitch machine from digital to analog servos for this very reason. Once the change was made, the owners never complained about being able to control the machine or position the needle as needed.

I would be happy to have a digital servo motor that started at zero and increased in speed only as I pressed down more on the speed pedal. I don't like motors that start fairly slow, then speed up on their own ("ramp up"). The motor speed should be pegged to your foot position on the speed pedal. If one needs an external speed knob, the same should apply. As the knob is rotated, the speed should increase.

5 hours ago, kgg said:

  13 hours ago, CowBoyOUTLAW said:

But why use speed reducer?

Because many servos lack high torque at lower speeds. I can see that the ones having more coils will have more low end torque. I would gladly pay more for an analog servo motor that eliminated to need for a speed reducer. However, when sewing thick veg-tan leather, the faster one sews, the greater the heat that is generated on the needle. I found that when I sewed at 15 stitches per second, smoke came from the needle! This also began melting the bonding agent on the nylon thread. The result was a weakened stitch line. I doubt that I am the only person who prefers to sew slowly to maintain control of the stitch line and needle placement, as well as to keep down the heat on the needle. I typically sew within a range of 1 (for detailed designs) to 6 or 7 (on straight edges) stitches per second. When I sew at higher speeds, I use an edge guide. When the leather is thinner, I can sew faster than when it is very thick. It can be dangerous to sew 3/4 inch at 5 or more stitches per second. If a fast moving needle is deflected by thick layers and breaks, it could embed itself in one's skin! Ask how I know this!

[dikman]

I guess it depends what market the OP is aiming for. I think it's fair to say that most don't want fancy options that they will never use, once one is set up for leather sewing it's doubtful they will fiddle around with the options in most servos - other than speed control. Yes, I know some like an NPS but once you have your machine setup for sewing leather, which generally means slow-speed, then an NPS isn't necessary. 

Having fiddled around with several different generic servos/speed reducers my optimum for sewing leather would be very low speed startup, lots of torque and variable speed using a knob placed near the machine. Having converted my lathe to a VFD I can use a knob to vary the speed at will, it is a much better system that anything else. And make it affordable!!!!! The OP has a "high-torque" motor currently available and it is apparently pretty good but at 2-3 times the price of generic servos I won't be buying one.