My Very First (Almost) Homemade Sewing Machine

[bikemaniac]

Hi,

Background:

From reading this forum I decided I needed a leather sewing machine, but I was unsure about so many things. Thus, I visited Trox in Oslo for 1 day and had a look at his workshop, his machines and we had many discussions on my needs etc etc. Particularly I was interested in the small frequency convertor he had in his shop, but as I remember it was not powering a sewing machine.

I went back to Denmark and had many thoughts on what to do. I decided to buy a Global WF1575

http://www.globalsew.com/en/wf1575.htm

which I bought at Frank Brunnet in the Southern Part of Germany (http://www.frank-brunnet.com/). By car I drove 700 kilometers to his shop to get my machine and he introduced me to the machine and we spent a few hours on the setup so it would work properly on leather. Without knowing one single person in Denmark who can setup my leather sewing machine I had to know how to make changes if you change thread sizes, leather thickness etc.

But I did not want to buy a motor from him. Not a servo motor and not a clutch motor and not an Efka motor - I wanted to make my own design. And Frank had a hard time understanding this. Thus, I only bought the head and some needles.

I'm a mechanical engineer and have have had many projects with motors, frequency convertors etc. Thus, slowly the drive system slowly emerged in my head and I planned precisely how to do it. Without ever having used a leather sewing machine before, making a drive system for a leather sewing machine, I jumped right in.

The basic setup was to use a frequency convertor, a 2nd hand foot pedal, an industrial 3 phase electric motor, 2 pulleys and a timing belt, and a bracket for attaching the motor directly onto the sewing machine.

The reason for doing this was, I realized I never wanted to do any fast sewing and I only needed a setup with a max speed of 150-200 stitches pr minute.

Purchase list:

1 ABB ACS150 frequency convertor with a max load of 0,37kW motors. Staying below 0,37kw ensures you will get a convertor that does NOT have an annoying fan. The frequency convertor is of the type where 1x240V is on the primary side (used in every European household) and the convertor splits the single phase into 3x240V besides being able to also changes the frequency from 0 to 500 Hz. Price 145 Euros.

2 A Cantoni 3 phase industrial induction asynchronous motor with a rated power of only 0,09 kW. It is a 4-pole motor with a max speed of approx 1350 rpm. Such a motor runs both on 3x400V but ALSO 3x240V. These motors are the most robust workhorses in the industry and can almosyt not be killed. Price 80 Euros.

3. A timing belt with a width of 10 mm and a corresponding large 80 tooth large pulley which a bolted to the hand wheel of the sewing machine. A small 10 tooth pulley attached to the axle of the motor. That would give me a gear ratio of 1:8. Total cost approx 15 Euros.

4. A used 2nd hand foot pedal from a domestic household sewing machine shop nearby. 10 Euros.

5. A 6mm mild steel bracket laser cut in a factory for bolting the motor directly to the sewing machine. I designed the bracket in a CAD program and sent the file to the company. Cost was below 10 Euros and it looks beautiful

With a friend we cracked the foot pedal open to investigate the electronics. Based on lots of testing we needed to buy a new sliding potentiometer at a cost of 0,50 Euros. It was soldered into place instead of the existing potentiometer.

So, with the current setup I can both run the machine from the foot pedal but also manually from the knobs of the frequency convertor itself.

Everthing was put together, the cables were attached to the frequency convertor, I threaded the machine and after a bit of hand cranking on a piece of leather I engaged the frequency convertor and the machine just started sewing without any problems the very first time making beautiful stitches just like in Southern Germany. I am extremely happy that this has worked out and serves my needs perfectly - plus I have learnt so much during this process. I am now ready for my first project this Winter. Beware my motor is only 90W but that works perfect because I only operate the machine at 150-200 rpm - and not 2500 rpms. Due to the gearing ratio, I have approx 5 Nm torque on the main shaft of the sewing machine.

I spent many hours on this drive project - and totally it would have been cheaper to buy a servo motor, cluth motor or something else already proven in the industry. But I wanted to do it myself and have a slow moving machine. With the setup I am now able to run as slowly as 20 stitches pr minute!

The only annoying thing about this setup is the humm from the motor when engaged but not moving - this is just part of everyday life when using frequency convertors.

Lucas

[Cascabel]

Interesting !!! I am much more familiar with the large converters used with heavy shop machines like lathes.

[bikemaniac]

Large converters are the most common ones in the industry: They get 3 phases in and 3 phases out while the operator can change the frequency. In my converter I get 1 phase in, 3 phases out, plus I can change the frequency. So basically my converter does 2 things :-).

Lucas

[biglew]

you should do a you tube video so we can see it run and sew'n on

thanks

Lew

[VanRhodes]

Sweet! Very well done and an extremely interesting project, I only wish you would have taken pictures during the process to allow us to follow that as well. :D

[Constabulary]

Great Job! Very impressive! A Video would be cool!

But I´ll stick with my servos anyway - no annoying sound when not running - but I´m honestly impressed!

[TwinOaks]

since that is a direct drive, how does it do for speed vs. torque?

[bikemaniac]

Because I am using a frequency converter, the torque is constant between approx. 5 to 50 Hz ... in the US it would be 60 Hz. Between 50 and 500 Hz, the torque drops steadily. Between 0 and approx 5 Hz the torque is almost zero. Actually, it would be more safe to say I have full torque between 10 and 50 Hz and there is a slight drop between 10 and 5 Hz. But basically it means I have full torque of 5 Nm between approx 25 rpm to 150 rpm. If I want to go faster than 50 Hz, i.e. faster than 150 rpm, then the torque starts to drop slowly. I guess, when running at 300 rpm, the torque is 3 to 4 Nm.

Lucas

Ps: But if I want more torque I could just buy a 4 pole 0,18 kW motor and have 10 Nm on the main shaft and then maybe have 7 Nm at 300 rpm. My frequency converter goes to 0,37 kW so I could also buy a 0,37 kW motor and have 20 Nm on the main shaft. I would only need a slightly longer timing belt. A 0,37 kw motor is very common and can be bought used for maybe 50 USD.

Edited November 20, 2014 by bikemaniac

[bikemaniac]

Great Job! Very impressive! A Video would be cool!

But I´ll stick with my servos anyway - no annoying sound when not running - but I´m honestly impressed!

What I could do: Build a switch into my foot pedal ... but I just have not done it (yet). As soon as I depress the foot pedal slightly, it turns the converter into the standby humming mode. When I depress a bit more the machine starts sewing. When I fully release the pedal again, the switch goes in the off mode and the converter becomes silent.

Lucas

[bikemaniac]

I just wanted to add, that if I would buy a 8 pole 0,09kW motor which runs at approx 700 rpm nominal speed, then I could stitch as slowly as 10 stitches pr minute with full torque :-).

Lucas

[catskin]

Isn't calling this DIRECT drive false, it is BELT driven. Direct drive would be with the motor coupled directly to the machine shaft.

[Trox]

Hi Lucas, Takk for sist.

I did not see your topic before now. I happy to see your project was a success, very nice built. And that a 90 W motor is proven enough is a bit of surprise, but I see the gear ratio. The time you where visiting I had no sewing machine set up with a converter, but I have had many before. I have used them mainly on 3 phase clutch motors because the lack of such power in my workshop. Even on 3 Ph old Efka variostop`s ( position clutch motor with electronic brake and clutch) They always have worked out great. I haven't had any use for the pedal (pot meter) on any of them, I only limited the top speed on the converter and used the clutch. I could alway go as slow as I wanted on the regular clutch motors, a stitch an hour if I wanted to. On the Efka variostop`s they only worked as converters because the motor control box regulate 6 to 12 pre set speed on the pedal and will compensate for any speed limitations set on the frequency converter (in the lower speed end that is). I recognize the humming you talk about, thats just the wrong frequency (speed) on the motor. Then I just set the hertz a bit different, some hertz up or down and it disappeared. I understand that can be difficult on zero, but then I guess the problem must be the pedal. Perhaps an adjustment or changing it will get rid of it. I am glad the Global worked out well to, it looks like a very nice machine. Overall a job very well done.

Tor

[Gregg From Keystone Sewing]

That's one heck of a setup, glad that you are happy with that. Just so that folks here know and to add to the conversation, Efka for example has on thier DC1250 and DC1550 motor control boxes an input for a external potentiometer for speed limitation, among other things, that would operate in the same way Bikemanic has it here. Not that Bikemaniac would have it any other way, but just to put that out there, and again, thanks for sharing.

Edited February 26, 2015 by Gregg From Keystone Sewing

[Trox]

Thats right Gregg, and I have moved up to using the Efka DC 1550 on my 441 machine. Very happy with it, more than enough power and a time saving setup. Expensive, but no need for a speed reducer and life time support.

I also use the older DC 1600 on a smaller machine (a DA 267), a very good motor too but not for sale anymore. You will understand why these motors cost more when you use them and get free support by Efka on Skype (if needed).

[Gregg From Keystone Sewing]

Thats right Gregg, and I have moved up to using the Efka DC 1550 on my 441 machine. Very happy with it, more than enough power and a time saving setup. Expensive, but no need for a speed reducer and life time support.

I also use the older DC 1600 on a smaller machine (a DA 267), a very good motor too but not for sale anymore. You will understand why these motors cost more when you use them and get free support by Efka on Skype (if needed).

That's the case, Efka support is pretty awesome for sure. I don't know about prices, but I would think the Efka DC1250 with control box in the $700USD range is not a bad option for most here. Not everyone, as you know, has your level of technical knowledge to put something like this together. Thanks again.