Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: Robhi on January 02, 2011, 11:19:06 AM
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hello...
happy new year....
i have a cnc machine with stepper motor, gecko drives and campbell breakout board, i would like to change stepper motors into servo ones, i do not really know which kind of motor i have to buy, AC or DC ones? will my breakout board will work with? and my drives gecko? i guess they are G230 thanks in advance for your help
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You can use the same breakout but you will need different drives. AC or DC is up to you, DC is much cheaper and most of the normal drive makers such as Gecko have drives for DC.
Hood
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OK thanks hood...
i would like to use G340...
could you give me a web site where i could order servo motors that can work with G340 drives, DC servo motors please?
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I am from the UK and not sure where you are from but if you are USA or North America then possibly www.kelinginc.net would be a good place to start.
Hood
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am from switzerland
Robhi
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Oh one thing to bear in mind is Keling and often others state the peak torque most prominently, so make sure you look at the continuous and size by that value.
Hood
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Not really sure of any place you could get them in Europe, maybe try searching for DC servo online shop in Google
Hood
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Oh one thing to bear in mind is Keling and often others state the peak torque most prominently, so make sure you look at the continuous and size by that value.
Hood
could you explain me please, peak torque and size by value? thankx hood
Robhi
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Just remembered about the Whale and Dugong drives from Hungary, they get a very good name and they also sell servo motors.
http://www.shop.cncdrive.com/
Servo motors have ratings for torque they can produce, it is often quoted in two values, one is continuous and the other is peak. The continuous torque value means the motor can produce this torque 100% of the time but the Peak is also available for short periods. The Peak torque is often 3 to 4 times the continuous torque so if you for example try and compare a stepper and a servo and use the Peak rating then you may find that you dont actually have enough torque for the machine. So if you know the torque of your steppers then get servos with approx the same rating for continuous torque and you should be ok.
Hood
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OK thanks Hood,
but am sorry if I bother you with my questions, they are servo motors with encoders and someones without encoders, what is the difference between them? and what should i buy?
Robhi
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You will need encoders, so you can either buy the ones with or buy the ones without if you already have encoders. Also no problem asking questions :)
Hood
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ok thanks so much I will have a look, but before buying anything I will let you know to advise me more in order not to make mistakes... thanks again
Robhi
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hello,
what is the encoder please? every servo motor has its own encoder or an ecoder works for all the motors?
Robhi
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DC motors can use any encoder that is of a suitable type for the drives, normally it will be incremental encoders with ttl square wave output.
Hood
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OK thanks hood...
now I would like to buy the following items, i would to tell if the will work togother please:-
1) KL- 7220 Specification: $189/pcs
Unregulated Power Supply 1440W, 72VDC/20A ,120VAC or
230VAC
2) Gecko 340 for servo motors
3) KL34-170-90 (NEMA 34) Dual Shaft, Front Shaft
1/2" Rear shaft 1/4" 850 oz-in Peak 90V, $139 Special
Sale:$129 Specification (Skewed Rotor Design,
Green is Ground, Red is +, Black is Common)
thanks in advance
Robhi
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The thing I see that may be an issue is the motor has a peak current of 30Amps where as the Geckos have only 20Amps max. I am not 100% sure but I think it will be fine but your best bet would be to email Keling and ask them as then you would have some comeback if they did not work.
How many axis will you be using as possibly the power supply will be on the small side for 3 axis unless you had one for each axis.
Hood
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i will use one power supply for the axis...
do you think it will not work well?
Robhi
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I think 1 supply for 1 axis would be fine, it may also be ok for 2 axis but I dont think it will work for 3 axis if you will be moving all 3 at the same time.
Hood
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ok thanks a lot so i have to buy 2 power supply...
thanks Hood
Robhi
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Ask Keling to make sure but as the motors you are buying have a continuous current rating of 7.5 amps you would be over the 20 amps of the supply if running all three at their continuous current, if drawing peak current (during acceleration for example) then you would be well over the rating of the power supply.
Hood
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I guess you are right... i have sent un mail to have more information...
thanks Hood .. that is so kind of you
Robhi
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I am sure they will keep you right :)
Hood