Ho Hsing G60 servo or what?

[dikman]

Matt, I hate you! You piqued my curiosity, I knew the synchroniser wouldn't work with a pulley reduction system (I tried it), but you got me thinking "did I actually try it with a (very) large pulley?". So I just spent all day to prove it one way or the other - and you're right (unfortunately). I had to make a new sleeve to fit the pulley to the shaft as I needed it more accurate than the existing one and also machined the end to take the synchroniser. Took most of the day! Then I had to move the control box from the left side of the table to the right side 'cos the cable wouldn't reach. While I was at it I swapped the motor and controller over, as one of my tables had a 750w motor which I felt would be better on the Seiko. So at the end of the day I tried it and found after 1 1/2 stitches it stopped and gave an error message indicating a synchroniser problem. The two pulleys, by the way, are a 1 3/4" on the motor and an 8" on the head.

I wonder at what ratio it stops working?

[Constabulary]

I´m also wondering if there is a setup with speed reducer that makes the NP work. 

Trial & Error science - I love it... go on please

[R8R]

18 minutes ago, Constabulary said:

I´m also wondering if there is a setup with speed reducer that makes the NP work. 

Trial & Error science - I love it... go on please

I was using an Artisan ACF-652C with a standard reducer wheel. Worked really well as long as you kept the top speed somewhat controlled. It didn't like trying to brake from over 2500 rpm - it might add a stitch or two before burying the needle but it was consistent if you kept the speed realistic. Never had a positioner error though.

 

This one btw -

http://artisansew.com/pdf/ACF-625cInstructionManual10_2017.pdf

[Matt S]

1 hour ago, dikman said:

Matt, I hate you! You piqued my curiosity, I knew the synchroniser wouldn't work with a pulley reduction system (I tried it), but you got me thinking "did I actually try it with a (very) large pulley?". So I just spent all day to prove it one way or the other - and you're right (unfortunately). I had to make a new sleeve to fit the pulley to the shaft as I needed it more accurate than the existing one and also machined the end to take the synchroniser. Took most of the day! Then I had to move the control box from the left side of the table to the right side 'cos the cable wouldn't reach. While I was at it I swapped the motor and controller over, as one of my tables had a 750w motor which I felt would be better on the Seiko. So at the end of the day I tried it and found after 1 1/2 stitches it stopped and gave an error message indicating a synchroniser problem. The two pulleys, by the way, are a 1 3/4" on the motor and an 8" on the head.

I wonder at what ratio it stops working?

 

52 minutes ago, Constabulary said:

I´m also wondering if there is a setup with speed reducer that makes the NP work. 

Trial & Error science - I love it... go on please

I believe it's a feature to detect broken or slipped belts -- a bit like when the machine jams -- obviously a firmware issue, and as such each model of motor is unique with regards to how much reduction it'll tolerate. I think most servos will tolerate a 2:1 reduction, as I currently have. Reports vary as to which models will tolerate a 3:1 or greater reduction with a synchro installed. Clearly some do, as they are supplied fitted to machines like the Cobra 441 clones. It's another characteristic that motor manufacturers don't publish that would be hugely useful to us leatherworkers, but I guess we're a tiny sector of the market, as usual.

I'm leaning more and more towards building a MCU- or PLC-controlled stepper, like @Uwe made. I'd get total, full-power control from 0RPM and all the fancy features I want. Problems would be the time I spend on it and reliability. Component cost would be a about equal with one of the better entry-level servos.

[dikman]

Could be a fairly involved project, Matt.

I guess my next step is to replace the motor pulley with a 3" and see if that works. This will give me a ratio of 2.67:1 compared to the current 4.5:1. I don't particularly need the synchroniser, but now that I've invested this time and effort it would be nice to get it working.

And I need to know.........

[dikman]

A bit more info for those who might like to know these things. I fitted the 3" (actually 75mm) pulley and it works fine! Actual ratio is 2.73:1.  Whether it's firmware or software is probably irrelevant but I would assume that it's programmed to only work up to a particular ratio, and if so then logically one would expect it to be a whole number and 3:1 would be a good guess. What I need now is a 2 1/2" pulley in order to prove this, unfortunately it's not a common size.

Now to experiment with settings and see if it suits my needs with the 3" pulley.

It's now an hour later and it's not as simple as I thought. If I go slow it stops fine, needle up or needle down, but if I run it fast it appears to get very confused when I take my foot off the pedal and shudders slowly for 3 or 4 stitches and then throws up an error. Next thing is to swap the 3" pulley for a 4"  (2:1) and see what happens. Only problem is I'm running out of belt adjustment! It's obvious that it's no longer going to be an option for me as I'll lose the slow speed and torque I had, but I need to know at what point the synchroniser will work (the info may be of some value to others).

Edited October 2, 2018 by dikman

[Kohlrausch]

I don't remember the exact values, but in older user manuals I have seen values like 600 spm for backtacking, 300 for needle up/down and 150 for thread cutting. So trying to do that at full speed may be a bit adventurous.

Greets
Ralf C.

[Gregg From Keystone Sewing]

On 9/29/2018 at 4:29 PM, R8R said:

Btw I tried out a reducer on that SP-1100 motor I posted and it worked great, positioner worked fine with it. I ended up removing it though as the 100 rpm start was fine and I will prob put the reducer on another machine.

Of all the motors I've looked at or used, this one is a winner. Great balance of power and utility vs cost. Other motors with similar power and low speed control have extra features I didn't need and it drives the cost up (auto back-tack, trimmer, etc)

Often the handwheel position speed being slowed down, it can give errors on some sync motors.  Glad to hear, I have not tried it yet.

[dikman]

Well, I've gone as far as I can to get the synchroniser working. The belt wasn't long enough to try the 4" wheel and my other belts are either too short or too long. I recall that when I first got it it worked fine but the pulley ratio was pretty much 1:1. It might work at 2:1, but I'm beginning to suspect not. The unit I have appears to be a pretty generic type as supplied with several servos, so probably pretty basic.I suppose the last two days haven't been completely wasted as I've learned something (and made a nice bushing for my big pulley). Matt, good luck with trying to achieve what you want, I'm sure it can be done - with enough money!

Me, I'm back to a tiny pulley on the servo and I can crawl the Seiko and it easily punches a #140 needle through 1/2" of veg.

[brmax]

In my setups I havent noticed any errors unless a belt slipage. Although the full NP functions are not available using a reducer,  as in typical needle positions with the heel the treadle application.

 If a different shnchronizer head with separate adjustments for up and down needle settings is an option for use that may prove to be a benefit on other servos.

With that, possibly ? This may Re-enable full/all functions of needle positioning. Just my thoughts on the subject today, this needle positioning is always a hot topic. Thanks for the tips

good day

Floyd