Gymnast Report post Posted July 18, 2019 (edited) I have made a demonstration video on my simple machine. It do have got a simple universal motor, a speed reducer, and I made some electronics for it that make the system act as a servo motor. The speeds demonstrated in the video are from 8 stitches/min to 540 stitches/min - a factor 68. The response to load changes and small moves are shown as well: What is your controlable speed range of your sewing machine with servo motor? Can you do better or worse? I have seen some recent demonstrations on youtube of industrial sewing machines with servo motors. And I am not that impressed of the speed control I see. For most of them, I see them jump start to a quite high low speed, and I do not like that. I did see this video from 2012 showing a resonable good low speed control, but I am not sure about the max speed and speed range: https://youtu.be/-h5U32SDZ38 Back in year 2012, several servo motor types had an issue, that they were hard to control. These issues were discussed in this forum, and I shall like to link to the four threads I just read about it:https://leatherworker.net/forum/topic/40034-question-about-servo-motors/ https://leatherworker.net/forum/topic/40168-cobra-class-4/https://leatherworker.net/forum/topic/41483-servo-motor-mod-diy-easier-speed-control/https://leatherworker.net/forum/topic/41916-having-problems-with-servo-motor-speed-control/ At that time a simple modification to some servo motors was introduced. More US suppliers of servo motors tried to make improvements and contacted their suppliers and manufacturers. I am however not sure, how much change to the designs that were later introduced. Electronic designers of servo motors may have limited knowledge of the needs of a sewing machine operator. Of cause an electronics designer can be incompetent aswell. The discussions here back then indicated, that many leatherworkers like to be able to sew very slow and also fast with the same set up. I think a factor 100 between lowest speed and highest controlable speed should be easy to make for servo motors. It could be from 45 RPM to 4500 RPM. However It seems to me, that most of the servo motors for sewing machines have a range with a factor about 30 only. The pedal construction can also be a limitation. However many leatherworkers were also happy with the motors they had. Others wrote, that they were not aware before the change, that they should like the better control they were able to get. Edited July 18, 2019 by Gymnast low response Quote Share this post Link to post Share on other sites
kgg Report post Posted July 19, 2019 Gymnast you have caught my attention again. I have a servo motor that came with my Juki and have good slow / fast control but nothing like what you are showing in the video. Could you post a couple of pictures of the motor setup and your peddle setup along with greater detail on your electronic modification. Maybe it could be adapted to provide better control for the industrial machines. kgg Quote Share this post Link to post Share on other sites
Gymnast Report post Posted July 19, 2019 (edited) Hi Kgg Thanks for your attention kgg. I did quite a lot of changes to my Singer 201k. It may not have been worth it, but I like its performance now. On my channal I made a small overview of the changes, and the changes relevant for speed are given from 3 min into this video: https://youtu.be/_7ML5U_I6DU A video about the electronics is not made yet. It is like an electronic foot pedal for a domestic machines that includes feed back loop from a tacho generator and a pressure activated pedal. A very small DC motor is used as a tacho generator (speed sensor), and you can see it Pictures. Servo motors will normally have a similar feed back loop internally, but better posibilities to make fast changes in torque and have got more precise rotary encoders. However servo motors shall adapt to more kinds of machines than my setup. Furthermore the control pedal was previously discussed in this forum here: Edited July 19, 2019 by Gymnast Quote Share this post Link to post Share on other sites
dikman Report post Posted July 19, 2019 kgg, I think you'll find it will be more complex to modify a servo than what Gymnast has done. Universal motors are much simpler to work with. The first thing you'd have to do is figure out how the electronics in the servo actually interprets the input from the speed sensor that is being used and then make a unit that can output the same signals to the main control board. Then you would need to make a new sensor that has a greater range of sensitivity and is compatible with the new unit. I'm sure it can be done, but it will be a lot of work and in all likelihood will only work with that particular servo. Whilst it is annoying that most of the servos don't start from 0rpm in reality it's probably not a real issue for most hobbyists as we tend to fit various types of reducers to give us the slow speed we need. Most of us don't need high speed when sewing leather, but if you need to start at 0rpm and still have max. speed available then one of the servos like Wiz uses is the obvious solution. Quote Share this post Link to post Share on other sites
Gymnast Report post Posted July 19, 2019 21 minutes ago, dikman said: kgg, I think you'll find it will be more complex to modify a servo than what Gymnast has done. I agree with dikman, that appart from the shown modifications back in 2012, changes to an existing servo motor are hard to do. There is a lot of complicated software inside a modern servo motor, which are involved in its performance and function. However there is industrial grade motor drives for short Circuit motors (short circuit motors are used for clutch motors on sewing machines). Perhaps some of these drives can be adapted. They are sold in big numbers for general use in industry. But I think this way is not that easy either. I think the best way is to look for the better performance when you search for a servo motor for sewing machines. From this video it seems, that some of the older type servo motors (with brushings) for sewing machines do not have any internal speed sensor. It may be a DC motor with a controlable DC voltage supply: https://youtu.be/SOyQtt3eDLw Quote Share this post Link to post Share on other sites
Gymnast Report post Posted July 20, 2019 (edited) On 7/19/2019 at 4:23 AM, kgg said: Gymnast you have caught my attention again. I have a servo motor that came with my Juki and have good slow / fast control but nothing like what you are showing in the video. Could you post a couple of pictures of the motor setup and your peddle setup along with greater detail on your electronic modification. Maybe it could be adapted to provide better control for the industrial machines. kgg I have seen the Enduro servo motor still using a slotted optical switch to provide input signal like all the references from 2012. It was also an Enduro servo motor, that was used for the the very popular "how to" video SWFLholsters made: https://youtu.be/X6CCxv3i4No Depending of what kind og sensor is used, and how the interface is made, it might be possible to make a retrofit solution by using an air pressure sensor instead. In this way it may be possible to use a pedal like me. When you look 10:30 into this video, you see the slotted optical switch, and 3 wires are leaving it for the motor control. If this is a standard component with a type number on it, I should like to know this type number. Edited July 20, 2019 by Gymnast Quote Share this post Link to post Share on other sites
mikesc Report post Posted July 20, 2019 You do start fascinating threads for the tinkerers amongst us :) Somewhere here*, there are some threads on stepper motors, I think maybe Uwe once set a machine up with one..and a "jog"** button ( as is / are used on many industrial factory machines nowadays ), usually the "jog" switch(es) is / are near the needle, for ease of use..my Juki 490-4 has a reverse "paddle" ( very small ) just above the needle, a "forerunner" of this idea. *I found a few of those threads..put this next line , exactly like it is, including the site: part, into any search engine. site: leatherworker.net stepper motor jog button Then click the search button **Single stitch or even fraction of single cycle of motor rotation Quote Share this post Link to post Share on other sites
Gymnast Report post Posted July 20, 2019 Thank you mikesc for helping to find what I search for. I searched for "servo motor" but got so many threads, that it became meaningless, and therefore I started a new thread. Now I found this 9 month old thread, that I might have continued. But I will look more into the matter. https://leatherworker.net/forum/topic/82673-ho-hsing-g60-servo-or-what/ It seems to me, that most leatherworkers are satisfied with the servo motors they got, but a few like to see a wider speed range and the positioner to Work with the step Down gear. I have tried to make a case about using a better food pedal, but I do not think, I had any luck there Quote Share this post Link to post Share on other sites
Gymnast Report post Posted August 21, 2019 (edited) I hope some of you can help me with at question about servo motors. When I read about servo motors for sewing machines, there seems to be a Group of motors, that looks like this: I think they are called DC motors with bruches. I got a question concerning the torque/speed caracteristics. In this video below, Stephen Feldmeier compares two kinds of servomotors. The other seems to be a bruchless DC motor. https://youtu.be/SOyQtt3eDLw Stephen mention, that this bruched kind of DC motor may be considered the "older" kind of servo motors for sewing machines. Do you agree with that statement? It seems like this kind of motor do not have electronics and speed sensors, that try to keep a constant speed of the motor. The torque/speed caracteristic have a slope, so with a constant setting on the food pedal, the torque drops off slowly when the speed is increased. It is the same way most older domestic sewing machine motors react to the foot pedal position. Do you agree to this statment regarding motors with this apperance? Edited August 21, 2019 by Gymnast Quote Share this post Link to post Share on other sites
kgg Report post Posted August 21, 2019 6 hours ago, Gymnast said: Stephen mention, that this bruched kind of DC motor may be considered the "older" kind of servo motors for sewing machines. Do you agree with that statement? It all depends on what ones needs are going to be. Either brush or brushless servo motors are going to be a good quite, controllable and cost effective solution over clutch motors in most cases. Servo motors that have brushes are more the type that you see being offered on relatively inexpensive sewing machine setups that will probably work great on light fabric / light upholstery rated machines where bottom end startup torque isn't going to be a typical problem. The brushless type is more suited for heavier work of multiple layers of thick materials / leather where the bottom end torque is going to be the priority. Within both brush and brushless servo motors you can have a large variance of quality and it will depend on the what performance specs were ordered. My rule of thumb would be the more coils the motor has the better the performance ( power consumption, noise, longevity, torque, etc. ). A 12 coil servo motor will be better then a 6 coil if the quality of the controls etc. are equal. I think in some cases investing in a servo motor or upgrading the servo motor from brush to brushless maybe a better overall solution then adding a speed reducer pulley but that will depend on the users needs. kgg Quote Share this post Link to post Share on other sites
Mark842 Report post Posted August 21, 2019 I run both types, brushed and brushless. Brushed are inexpensive for the pro and IMO in low torque applications actually have smoother control (could just be a brand thing). The con is if you do a ton of sewing you have to change the brushes. I run a brushless on a Cobra 4 that sees a lot of high torque low sewing and is being run on average 4 hours a day, 6 days a week. All my other machines are smaller for sewing garment thickness leather and I run brushed on them all. Those are all low use, maybe 2-3 hours a week. I 've never really timed the stitch speed on my cobra but I can sew incredibly slow with tons of torque. Most of that machines life is spent sewing 3 and 4 layers of 9-10 latigo. Quote Share this post Link to post Share on other sites
Gymnast Report post Posted August 22, 2019 (edited) Thank you for your answers kgg and Mark842. I just like to say, that this low speed torque, that you like the motor to have for heavy leather work, is a matter of the electronics, and not the brushes. A brushed DC motor can provide high torque at low speed, if it have got internal sensors measuring the speed and electronics control the motor current, so same speed is maintained. But it is my impresion, that all the brushed DC motor servo drives sold for sewing machines do not have this kind of electronics build into them. I saw this supplier selling 4 types of servo motors looking like my Picture above. And the seller argue, that they perform different. Brushed DC motors with no extra Electronics can of cause have smaller differences in torque/speed caracteristics. So if someone using this kind of motors says it have good low speed torque and easy controlled speed, the electronics for it may be inside. https://www.sewingmachinegallery.com/best-sewing-machine-servo-motor/ Edited August 22, 2019 by Gymnast Quote Share this post Link to post Share on other sites
