fibersport Report post Posted September 12, 2023 Are there any servo motors that actually have a zero speed startup? I bought from a supplier a few years ago but it doesn't start at zero, the controller says 200 I think, not sure if that is truly 200 rpm or not but it isn't zero. I see conflicting specs on some of them saying the speed range is 0-4500 - but will it actually start at 0 rpm? Quote Share this post Link to post Share on other sites
Tastech Report post Posted September 12, 2023 I remember watching a youtube video where this guy worked out how to make a servo motor variable speed without a reduction wheel . From memory he used a specific motor which i believe was a consew brand . What he did was quite genius in that the tweek was counter intuitive and used a simple piece of paper . The basic principle of what he did was fooling the machine . The motor speed is activated with a beam of light . When the light beam is broken the motor activates . The way it is on a standard motor is a piece of metal cuts the beam and it activates the motor . What the guy did was to either replace or extend the metal with a simple piece of copy paper . For some reason the paper cutting the beam makes the motor start of slow like the accelerator on a car . I have made a half arsed effort to find the video over the last couple of weeks but i would like to do it to mine so i will have a good search and if i find it i will post it . In the meantime if anyone else finds the video please post it as i am sure 50% of us will find it handy . Quote Share this post Link to post Share on other sites
Northmount Report post Posted September 12, 2023 2 hours ago, fibersport said: 0-4500 - but will it actually start at 0 rpm Just semantics, but 0 rpm is stopped, not running. The question really is, what speed does it start out at, and does it have enough torque to punch through the leather? Quote Share this post Link to post Share on other sites
Wizcrafts Report post Posted September 12, 2023 This must certainly be a digital servo motor and probably an early design at that. When servos first appeared on industrial sewing machines, they either started rotating at 100 or 200 RPM. Cobra came up with a variable density transparency that replaced the existing light blocker attached to the control lever on the left side of the motor. Some folks made their own variable density filters with pencil strokes on clear plastic. I got the filters from Cobra and they worked well for about a year, then began to have a hiccup as the motor started up. About that time, the new style analog motors made their appearance and I bought one for every machine in my shop. These motors have a knob that is attached to a pot or a rotary switch that limits the top speed. I usually set mine about three steps up from the minimum setting. The startup from zero is totally smooth. I get my analog servo motors and speed reducers here. Quote Share this post Link to post Share on other sites
Gump Report post Posted September 12, 2023 I have 2 Sewquiet servos, and startup is as slow as you would like no matter motor what setting you use right up to max. Quote Share this post Link to post Share on other sites
Uwe Report post Posted September 12, 2023 (edited) The short answers is NO, none of the brushless sewing machine servo motors you can buy today can do 1rpm, which is what you’re implying by starting from 0rpm. 1rpm means you’ll wait a minute for the motor to make a full rotation, three minutes or so for the machine to make a stitch. Not really practical. The spec on most servo motors should really read: 0rpm, then 300rpm-2000rpm. There is generally nothing between 0rpm and 300rpm. Most servo motors I have worked with have a starting speed of 300rpm, some can start at 200rpm, very few can start at 100RPM (including the 1,500 Watt motors I’ve been buying.) None of the motors I’ve seen can start slower than 100rpm. With a small pulley, that 100rpm starting speed translates to a stitch every two seconds or so on the big 441 style machines. That’s all I want, personally. The minimum starting speed is kind of a design feature inherent in servo motors, and the controllers that drive them. While it’s technically possible to make a servo motor start veeeery slowly (or one tiny step at a time), the sewing machine motors on the market here in the US are not designed that way. Edited September 12, 2023 by Uwe Quote Share this post Link to post Share on other sites
dikman Report post Posted September 12, 2023 Tastech, that method of speed control adjustment was used in early servos and as far as I know stopped being used some time ago. They tend to use Hall effect sensors these days, which work on a magnetic field variation to generate an electrical signal. It's pretty hard to tinker with these. Quote Share this post Link to post Share on other sites
fibersport Report post Posted September 13, 2023 Perhaps I should have worded my question along the lines of a slow ramp up in speed from 0 rpm to whatever maximum might be. I do realize that 0 rpm is stopped but one has to start somewhere, and I know what revolutions per minute means - and really why would anyone want to sew at 1 rpm? Wizcrafts you seem to understand my initial question, starting at 200 or 300 rpm is what I have but not what I want. It's that initial start up speed that I'm trying to lower. A clutch type motor could be made to start up slow by slipping it but I don't sew enough to be able to master that technique even though I've driven vehicles with clutches for decades, slipping a clutch on a sewing machine just eludes me! Thanks for all the suggestions and comments, nice to have a great brain trust from which to tap in to once in a while. Quote Share this post Link to post Share on other sites
chisel Report post Posted September 13, 2023 12 hours ago, Tastech said: ....In the meantime if anyone else finds the video please post it as i am sure 50% of us will find it handy . If these aren't the videos then hopefully they will help. https://www.youtube.com/watch?v=X6CCxv3i4No https://www.youtube.com/watch?v=wu2OT9MtzMc Quote Share this post Link to post Share on other sites
Tastech Report post Posted September 13, 2023 Chisel , They are the videos i was referring to . I now realize that the new servo motors are of a different type and this modification is not applicable . I guess the only option is to reduce the motor pulley size or fit a speed reduction pulley . In relation to speed reduction pulleys . Why are they so expensive . ? There is nothing to them really .By the time i get one sent to Australia i am looking at over 300 bucks . Twice the cost of a servo motor . I need about 5 of them .As i am also a mechanical engineer i might just make up my own using off the shelf components and maybe just a little machining. I think i can do it for under 100 bucks a piece . The way i see it i will need 2 pulley wheels of different sizes , shaft to suit .( might need machining ) 2 bearings and the bearing housings , some grub screws and maybe 2 hours . Quote Share this post Link to post Share on other sites
Burkhardt Report post Posted September 13, 2023 Quote Share this post Link to post Share on other sites
fibersport Report post Posted September 13, 2023 Tastech - a picture of the speed reducer I made is on the second page of the link that Burkhardt posted. Quote Share this post Link to post Share on other sites
kgg Report post Posted September 13, 2023 12 hours ago, Tastech said: As i am also a mechanical engineer i might just make up my own using off the shelf components and maybe just a little machining. Here is a good link to save you some time when designing your speed reducer and get a pretty accurate estimate of what you design will give you. https://www.blocklayer.com/pulley-belt kgg Quote Share this post Link to post Share on other sites
dikman Report post Posted September 13, 2023 Tastech, there have been many posts on here regarding building a speed reducer. As you say, not too difficult to cobble something together. Quote Share this post Link to post Share on other sites
Tastech Report post Posted September 14, 2023 (edited) 15 hours ago, kgg said: Here is a good link to save you some time when designing your speed reducer and get a pretty accurate estimate of what you design will give you. https://www.blocklayer.com/pulley-belt kgg That is so cool. I love it . Thanks KGG dikman . I ordered the parts for 1 reducer last night after reading this thread . I have 12 machines with 5 different table variations . I have a plan in mind to make a "universal" type but i might opt for maybe 3 different varieties . I want to make them aesthetically pleasing as well as functional. I will road test the first one to make sure i have the pulley combination correct to suit the machine and base the others on that I am starting off with a 45mm and a 120mm pulley combo with my motor at 100 rpm i would be somewhere in the less than one stitch per second range which is ideal for wingtips and brogue stitching on shoe uppers . Edited September 14, 2023 by Tastech save posting another reply Quote Share this post Link to post Share on other sites
fibersport Report post Posted September 14, 2023 I used that pulley calculator too just to see what speed I would be getting. I also downloaced an app on my phone to use it to measure speed, while probably not perfect, it worked consistently. My pulleys are, measure on the OD of the pulley, 50, 120, 42 and about 80mm on the machine. My measured motor speed was 502, my machine speed was about 106 which matches up really close to the pulley calculator. That gives me about 1.7 stitches per second. I would like to be able to get slower than that, thinking it's the servo motor start-up speed that's keeping things faster than I would like. Quote Share this post Link to post Share on other sites
kgg Report post Posted September 14, 2023 8 hours ago, Tastech said: I am starting off with a 45mm and a 120mm pulley combo Who did you order the 120 mm pulley from? kgg 8 hours ago, Tastech said: That is so cool. I love it . That calculator saves a few of the old remaining brain cells. kgg Quote Share this post Link to post Share on other sites
fibersport Report post Posted September 14, 2023 I ordered the same pulley combination, got them off of ebay, they came direct from the C country and cost something like $15 for both. I would have liked to go bigger on th large one but had a tough time finding one that was cheap. Quote Share this post Link to post Share on other sites
Tastech Report post Posted September 15, 2023 Who did you order the 120 mm pulley from? Hey Kgg .I got the pulleys on Ebay here is the link https://www.ebay.com.au/itm/314035306394?var=612710007766 Now in hindsight i should have got a few more in various sizes just in case . I have been using poly belts instead of fixed size V belts . They are a red color ,they come in various diameters can can be cut and joined with a little insert able 2 way plug . Pretty cheap at $3-4 per meter . They stick well to the pulleys therefore no slip and have a fair bit of spring in them so things are always tight . I measure the length i need and deduct 10%.and cut it at that . So far so good . I don't do astronomical speeds or use the machines for a very long time .However if i was working a machine in a sweat shop i would go the best belt i could get . Quote Share this post Link to post Share on other sites
dikman Report post Posted September 15, 2023 I had the same problem with pulley sizes when I was experimenting with speed reducers. 120mm appears to be the largest a lot of ebay sellers have, and trying to buy anything local was expensive. Fortunately I had a bit of an assortment of old pulleys, which I managed to make useable by sleeving the oversize shaft holes. I used the 45/120mm combo on one machine and also replaced the hand wheel with a larger pulley, this gave me 1 stitch every 3 seconds! Impressive but not very practical. Quote Share this post Link to post Share on other sites
Uwe Report post Posted September 16, 2023 (edited) I made a short demo video showing the 100rpm startup speed on my Adler 30-1 and Juki LS-341 using the 1500 watt servo motors I source on Alibaba.com. They cost around $150 each shipped to the US (minimum order quantity is 4). I’m not trying to sell these motors, just giving a demo of the motor that works for my needs. https://youtu.be/4Uc7uEdmcK4 Edited September 16, 2023 by Uwe Quote Share this post Link to post Share on other sites
Uwe Report post Posted September 17, 2023 (edited) Just trying to embed the video in the post … https://www.youtube.com/watch?v=4Uc7uEdmcK4 Hmmm, not sure why I can’t do this right now. Edited September 17, 2023 by Uwe Quote Share this post Link to post Share on other sites
Tastech Report post Posted September 17, 2023 Very informative video Uwe . Is that a 45mm pulley on the motor ? That Adler runs at a perfect speed for doing shoe repairs You say you have 4 motors . The next time you fit one of the motors could you please make a video of how you installed the needle positioner . Quote Share this post Link to post Share on other sites
shelr1 Report post Posted September 17, 2023 I purchased a 6" OD 1/2" bore pulley from Amazon, 22.20 including tax. Quote Share this post Link to post Share on other sites
kgg Report post Posted September 17, 2023 (edited) Here is Uwe's video @Uwe. kgg Edited September 17, 2023 by kgg Quote Share this post Link to post Share on other sites
