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Offline Robhi

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servo encoder ?
« on: April 29, 2012, 12:21:57 PM »
hello,

I would like to change my stepper into servo motors, I am using gecko for stepper motors, and sound logic breakout board, I would like to use gecko for servo motors.

is it easy to wire servo motors to gecko? could i use my sound logic breakout board? or Should i need to change all my system? how and where we wire the encoder?
am very sorry i do not know anything about servo motors.. hoping to have your help..

thanks à lot for all of you
Re: servo encoder ?
« Reply #1 on: April 29, 2012, 12:49:54 PM »
You will need new motors, encoders, new Geckos (G320X instead of whatever you have), almost certainly new power supplies, and you'll have to add belt or gear reducers to all axes.  The BOB is about all you'd be able to re-use.  Why on earth would you want to do that?  What "problem" are you trying to solve, other than perhaps having too much money in your bank account?

Regards,
Ray L.
Regards,
Ray L.

Offline Robhi

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Re: servo encoder ?
« Reply #2 on: April 29, 2012, 01:01:21 PM »
Thanks for your reply...

really i do not have tout much money, but am workink with wood, turning etc... and my machine is not faster enough, I would like to have a fast machine and save time, as it is said time is money.
so I can re use my sound logic breaktout board? it is good news for me..
what about the encoder? where it is should be wired? I sometimes see servo motors with too many  wires and that makes me à little bit afraid.
Re: servo encoder ?
« Reply #3 on: April 29, 2012, 03:13:27 PM »
What kind of machine is this?  Unless it's very large, you should be able to get all the speed you need with the proper steppers, and do it for a lot less money.

What motors, controllers, and power supplies do you have now?  Speed problems are most often the result of using motors that are too small, and/or controllers that have limited voltage/current capability, and/or power supplies that do not provide enough voltage/current.  Switching to servos will not solve your problem any more than steppers will, if the whole system is poorly designed.

Regards,
Ray L.
Regards,
Ray L.

Offline Robhi

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Re: servo encoder ?
« Reply #4 on: April 29, 2012, 04:39:56 PM »
you can have a look at theses links. they are my first tester on my machine
http://www.youtube.com/watch?v=dgzQKTd4Z14

http://www.youtube.com/watch?v=AbOTqzYmDy8
I use gecko drives for stepper motor and 24 volts


thanks again
Re: servo encoder ?
« Reply #5 on: April 29, 2012, 04:53:15 PM »
I use gecko drives for stepper motor and 24 volts

And there, in a nutshell, is your real problem.  A machine that size should be able to easily run several hundred inches/minute on steppers, IF they're properly driven, which yours are definitely not.

Getting good high-speed performance from a stepper motor requires MUCH higher voltage.  Most steppers require on the order of 50-70V to get optimum high-speed performance.  At 24V, you'll be severely limited, due to the coil inductance, and will never actually reach full current except at very low speeds.  Increase your supply voltage to the appropriate value (based on the inductance of your motors), and your performance will be improved dramatically.  Do some reading of the Gecko FAQs for steppers, and proper power supply sizing.

Regards,
Ray L.
Regards,
Ray L.

Offline Robhi

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Re: servo encoder ?
« Reply #6 on: April 30, 2012, 03:25:46 PM »
hi Ray L and of you of course...

to continue the discussion, I use exactly gecko 201 and my steppers are as the following




Code

160-010-00400



Type

Hybrid Stepper



Holding Torque

220Ncm



Step Angle

1.8°



Rated Voltage

7.5V



Rated Current

2.5A/Phase



No. of Wires

8



Size

57x57x115mm



Shaft Dia.

10mm



Shaft Length (Front)

30mm



Shaft Length (Rear)

30mm



Net Weight
My power supply is 24 volt for 10A,
what kind of power supply could I use?  I would like to have the best for my gecko and my steppers in order to increase  the performance of my machine.
best regards
Re: servo encoder ?
« Reply #7 on: April 30, 2012, 03:53:08 PM »
Well.....  Assuming this is your motor:  http://www.arceurotrade.co.uk/projects/stepper/220Ncm%20Stepper%20Motor%20160-010-00400.pdf  I'm afraid if you want high speed the first thing you need to do is get new motors.  Those have VERY high inductance, which makes their high-speed performance very limited.  A good motor in that size will have an inductance of around 2mH, rather than the 10mH those have.  You also probably should go up a step in torque, to something on the order of 300-400 N-cm, to make sure you have plenty of torque at high speed.

The Gecko 201s are fine.  You could increase the speed with the existing motors some by increasing your power supply voltage.  Given the high inductance, you could run it up to the max on the Gecko drives, about 75-80V.  But if you get some good 2mH motors, you'll only want about 48V for optimum performance, and you'll get considerably better performance.  In either case, power supply current rating should be about 70% of the combined rated motor currents.  So if you have three 5A motors, you'd want about 10-11A.

Regards,
Ray L.
Regards,
Ray L.

Offline Robhi

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Re: servo encoder ?
« Reply #8 on: April 30, 2012, 04:24:12 PM »
Thanks too much for theses good information that you gave me, I am very happy of your reply thanks à lot again.
I may have some others question, but, I guess later...


best regard
robhi