servo motor startup speed

[fibersport]

There have been many good comments on my original question.  After doing more research and actual testing, it seems that my biggest problem is the ramp up speed of my Goldstar servo motor.  With that said, I'm really leaning towards just replacing it with a better motor.  The two that seem to be popular are the Consew CSM550 (or equivalent) and the Reliable 6000sm (or equivalent).  I know Wizcrafts has the analog type motor and Uwe has the digital type and I value both of their knowledge and opinions.  The price is minimal between the two types although the digital model can use a needle positioner, which might be a nice option but not required.  Brush wear is not an issue for me as I would probably never wear a set out.  I guess my question really is which one has a slower ramp up speed?  

[Constabulary]

Or add a speed reducer. That slows down the speed when you start sewing and increases torque. I have speed reducers on all my machines. I have digital servos and stepper motors (you don´t have them in the US AFAIK or at least they are not wide spread). On my side of the pond (Germany) they are called "Anlasser Motor".

Speed reducers add a lot of comfort IMO.

Just my 2 cents.

Forum search for speed reducer via Google - just to give you an idea

https://www.google.com/search?client=firefox-b-d&q=speed+reducer+site%3Aleatherworker.net%2Fforum

Edited September 20, 2023 by Constabulary

[fibersport]

Thanks Constabulary but I already built a speed reducer.  It does bring the overall speed down nicely but it's the ramp up speed that I'm looking to slow down.  My current motor starts at about 500 rpm, I have brought the machine rotation down to about 100 rpm which is nice and slow but it literally goes from 0 to 100 with no ramp up.  My current motor also has a digital control so unless it can be reprogrammed, there is no way I can adjust the start up speed.  One other thing, using a speed reducer means I can't use a needle positioner due to the rpm differences of the different pulleys involved - although not having one isn't that big of an issue with me.  I'm just trying to see if there is a difference in ramp up speed between the two motors that I think I've narrowed things down to.

[Quade]

Quote

 After doing more research and actual testing, it seems that my biggest problem is the ramp up speed of my Goldstar servo motor. 

Did it come with a table you bought from them?  I got a machine from them last week with table and the servo is pretty cheeseball.  While it's the same design as the "Consew" I recently bought, the consew is an altogether better motor. 

You can reduce the start speed of this motor by programming the box. The default start speed is 200.  It's functional but I am planning on switching to a smaller pulley for now.  

Quote

The two that seem to be popular are the Consew CSM550 (or equivalent) 

https://www.amazon.com/gp/product/B07Z7F6W79/

I have this on one table. Pretty happy with it. Better than the one that came with the new machine. 

[fibersport]

No it didn't.  I bought it some years back to upgrade from a clutch motor on my old Singer.  I'm really hesitating to buy another digital controlled motor that looks a lot like what I already have.  From what I'm reading, the Reliable motor is a 12 coil motor which should give me better start up torque and what looks like a stronger physical designed motor.  It seems the Reliable and the Sailrite are the same motors except for price.  The brush motor that Wizcrafts talks about looks like its a tried and true motor, just more old school in terms of servo motors.  Those reasons are why I'm looking to find someone that has one of these motors, to basically compare actual experiences rather than just reading about them.

[kgg]

26 minutes ago, fibersport said:

I'm really hesitating to buy another digital controlled motor that looks a lot like what I already have.  From what I'm reading, the Reliable motor is a 12 coil motor which should give me better start up torque and what looks like a stronger physical designed motor.  It seems the Reliable and the Sailrite are the same motors except for price.  The brush motor that Wizcrafts talks about looks like its a tried and true motor, just more old school in terms of servo motors.

Yes according to the specs the Reliable and the Sailrite motors appear to be clones of one and another with both being 12 coil designs.

There is more at play here when trying to find the min startup speed of the motor. You need to know the size of the small pulley on the end of the motor and the size of the hand-wheel pulley on the sewing machine. So finding someone with the exact same setup and an rpm digital tachometer maybe difficult. Since you can measure the size of your hand-wheel all then left is to determine the size of the small pulley on the motors and their speed range. Once you know those parameters you can use a pulley calculator to determine what to expect on your machine whether it is a brush or brushless servo motor.

What I found is that Reliable does not list the speed range but I'm assuming it to be like the Sailrite Workhorse. They say " which let you set your top stitching speed while maintaining variable speed control. Variable maximum speed settings range from 400-3600 stitches per minute.  " which does differ from the max rpm of the motor being rated at 4500 rpm. So from that the motors low start up speed is 400 rpm. Sailrite lists two pulleys a Black one and Silver one with the Black one being a clogged 33mm and the Silver being a V-belt 60mm. These specs are from their webpage ( https://www.sailrite.com/Sailrite-Workhorse-Servo-Motor-110V )

The specs for the Consew I could not find.

My experience with a digital servo motor with a speed range of 500 - 5000 rpm on a 800 watt, 9 coil and with no reducer pulley are

Calculated top speed of the hand-wheel pulley should come in at 156 rpm using a 160 mm hand-wheel pulley size, a 50 mm motor pulley and 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 pulley and hand-wheel sizes were.

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

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

 

Measured results with 500 rpm's showing on the controller screen

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

ii) 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.

Hope this helps,

kgg

 

 

[Tastech]

Reading these comments and the dilemma of the start up speed makes me appreciate the machines i have on treadles .  mind you treadles are not created equal .Not essentially true but you need the right size fly wheel to suit the machine and your purpose . My favorite combo is my Pfaff post bed with a 29K patcher treadle which has been modified into a flat bed . The secret is the smaller diameter flywheel . 12 inches .. Nice and slow for doing the curves of shoe uppers . Above all they are reliable , 100 years old and still going . You also need the right chair /stool to minimize ass and hip cramps . 

[Quade]

Quote

The brush motor that Wizcrafts talks about looks like its a tried and true motor, just more old school in terms of servo motors

I had one of these.  I'm going to let it go with a machine I'm getting rid of.  It functions, but I don't like the feel as much as the digital motors.   The digitals seem to have more slow speed torque. 

Looking at the "workhorse".  It seems pretty decent. I might have to try one. 

[Wizcrafts]

1 hour ago, Quade said:

I had one of these.  I'm going to let it go with a machine I'm getting rid of.  It functions, but I don't like the feel as much as the digital motors.   The digitals seem to have more slow speed torque. 

I agree that the analog servo motors have low starting torque. On the machines where I need low speed with high torque, I add a speed reducer. That cures the problem entirely. Some are 2:1, others are 3:1 speed reduction/torque multiplication. These motors and reducers came from Toledo Industrial Sewing Machines.

One of my 10 machines is mounted on a table I've had since 2010. I've change the machine heads several times, but kept the table and motor. The motor is branded SewPro 500GR. It is an analog servo motor with a built in 3:1 speed reducer. That motor powers any machine that fits in the cutout through the densest leather. I tried to buy another SewPro 500GR motor two or three years ago but learned they are no longer made. Evidently, the people who made them in China went out for lunch and never came back! No motor for you!

[fibersport]

Keep in mind that I am not concerned with the minimum speed, what I am looking for is a ramp up speed, or actually time.  As I have said, I have a speed reducer installed.  My minimum motor speed is 500, my final output speed is about 109.  I have an app on my phone that uses the camera light to act as a strobe to tell you what the rpm is, both my phone app and calculations are in agreement with my measurement of the pulleys and machine handwheel.  I am looking for the slowest ramp up speed between the analog and digital servo motors.

[Gump]

Your speed setting doesn't have any bearing on slow speed start. My Sewquiet 6000 is set on maximum with a speed reducer. I can do 1 stitch at a time or 1183 spm flat out. Without reducer I get max machine speed at setting 22 out of 30. For high speed work the motor can be set higher, but you lose slow speed start. I got this from the manual, as it isn't in the spec. literature. So apparently it has slow start speed built in.

[Quade]

Quote

 Evidently, the people who made them in China went out for lunch and never came back! No motor for you!

Haha that's China for you.  

[fibersport]

Gump - I caught the start up speed setting in a video on setting the parameters on the Sewquiet 6000, zero disables the slow start but it didn't say what the highest number is nor what the different settings actually do. 

With my current set up, it's either zero or 500 rpm at the motor.  On your sewquiet, can you slow the stitch down just by feathering the treadle? 

[kgg]

2 hours ago, fibersport said:

I am looking for the slowest ramp up speed between the analog and digital servo motors.

From the information I have seen a Brushless servo will have anywhere from 5 percent to 15 percent advantage of converting electrical power to mechanical power over the Brushed servo motor. The big but to this has a lot to do with how many coils the brushless servo motor was constructed with and particularly how good the box of electronic controls are. The performance advantage of a brushless servo motor when using a speed reducer probably will be unnoticeable. From a durability point when comparing quality built motors will probably the same.

However the brush motors with the manual speed knob are much simpler to track problems which typically means replacing or cleaning the motors brushes. When the electronics and some brushed servo motors did have some electronics give problems and particularly the brushless it is probably cheaper just to replace the whole unit.

I feel the only reason the brushless servo motors are becoming more available is that they are considerably cheaper to manufacture.

kgg

 

[Uwe]

EFKA is one of the high-end motor and controller options for sewing machines, for a price (roughly $1,500+ range for motor+controller+control panel).  These are designed for industrial production applications and are not targeted at the home/hobby market.

The spec sheet for DC1550/DA321 combo states a minimum starting speed of 70rpm. I have a feeling this is the state of the art in motor controls. 

 

For speeds slower than 70rpm, you have the option of using an electronic thumb controller, that you can twirl as slowly as you want with your thumb.

 

 

 

Edited September 22, 2023 by Uwe

[Uwe]

Depending on your expertise in electronics and programming, you can also build your own motor and controller that does exactly what you want. I did that once using a stepper motor and Arduino controller, just as a demo project for a thumb controller retrofit. The stepper motor I had on hand for testing was not suitable for actual sewing, it was super noisy.

Here’s the demo video I made of that experiment. Aside from the thumb controller, you can also see the super slow ramp-up speed I got with the foot pedal.

 

Using a modern servo motor like the Clearpath line made by Teknic  you could build a usable system that truly ramps up as slowly as you want with no jump from zero to some minimum starting speed. Cost would be around $700-$900 for the parts, I imagine. 

Edited September 22, 2023 by Uwe

[fibersport]

Uwe - great information and really am impressed with your home built unit.  As for the Efka - way too rich for my blood.  The Teknik would be a very interesting way to put together a great system but right now I already have way too many projects!

Kgg - good information, thanks, I'll put it all in my memory bank as I continue my quest.

[GerryR]

You might want to consider a 3-phase AC motor with a variable frequency drive (VFD).  They are at rest (0 rpm) and go to whatever frequency in their max spec.  Under line frequency (60 hz) they are in constant torque mode and above line frequency, they are in constant horse power mode.  A simple pot varies the speed (think TIG welder's foot pedal).  I used one for an old singer 153W103 machine that I had.  The 3-phase controller runs off 1-phase power (does the 3-phase conversion internally) and was less than $200.00 at the time.  I had the 3-phase motor from an automation project I was involved with; It was 1 hp, way overkill for the sewing machine, but the price was right.  You can get fractional hp 3-phase motors reasonble priced, so I would expect you could do what you want for way less than $500.00 and make the ramp-up speed whatever your foot can control.  Just another approach you might want to consider.

Here's an example for $151.00 for a unit that will handle up to a 1 hp motor off of 120VAC 1-ph input.  Many options available.

https://www.automationdirect.com/adc/shopping/catalog/drives_-a-_soft_starters/ac_variable_frequency_drives_(vfd)/micro_vfds/gs11n-11p0?gclid=CjwKCAjwmbqoBhAgEiwACIjzEPTZASfk6Z5gjXMFhUpfdFMd8IOdoPKZY2FSaUI4c0NeXNRC6rN19xoCR9AQAvD_BwE

Edited September 23, 2023 by GerryR
Spelling

[Gump]

I can run the needle slow enough to thread it on the way down. Ramp up is as slow as you can ease the pedal down. Slowing down is a little more abrupt, but that is because of so little resistance from the pedal.

[fibersport]

Gump - that's what I'm looking for, however my eye's aren't that good, I would probably sew through my finger!  Your comment reminded me of a video I once saw of someone changing a fan belt on an old VW beetle with a screwdriver when it was running.  I've been doing some reading up on the Sailrite Workhorse, they too say that you can basically go stitch by stitch when starting up or in intricate areas.  Any idea what the minimum speed might be of your motor, I can only find range and a maximum but not a minimum.  Maybe because you can't really measure the minimum as it's ramp speed is variable so they just say it starts out at 0?

Edited September 25, 2023 by fibersport

[GerryR]

17 hours ago, Gump said:

I can run the needle slow enough to thread it on the way down. Ramp up is as slow as you can ease the pedal down. Slowing down is a little more abrupt, but that is because of so little resistance from the pedal.

The same would be true with the VFD and 3-ph motor.  I used a 5:1 gear reduction motor giving a max output speed of 345 rpm, so you could vary the top speed down from there through the VFD setup.  As you stated, ramp up is as slow as you can ease the pedal down.  (I wouldn't try threading a needle while it was moving!  )

[fibersport]

GerryR - as they say (not that I would), many ways to skin a cat.  I think your method would be great for a system that is run full time as it sounds very robust, it sounds like it would be at home in an industrial environment.  Right now, I don't have the time to devote to yet another project putting everything together for the drive system - I like to tinker but I'm more mechanical than electronic, but still I like your approach.

[Gump]

At dead slow, you can pretty much feel the fields of the motor as it almost bumps from one to the next. With a needle positioner you get 1 stitch for one tap of the pedal.

[GerryR]

1 hour ago, Gump said:

At dead slow, you can pretty much feel the fields of the motor as it almost bumps from one to the next. With a needle positioner you get 1 stitch for one tap of the pedal.

Being a DC motor, you would get that effect.  With a VFD you would not.  One thing I didn't mention about using a 3-ph motor with a VFD is that the motor has to be an "inverter duty" motor to tolerate the slow speeds (low frequencies)  They are more robust and can handle the extra heat generated not having the cooling fan running at full speed.  I expect that using a needle positioner / sensor would have the same effect, one stitch per tap of the pedal.  The advantage of the DC servo over the AC system would probably be in the motor size.  DC motors generally get more power in a smaller package size.  The AC system is just another option to think about.

[fibersport]

Has anyone installed a smaller drive pulley on a digital servo motor and if so, were there any issues?