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Author Topic: Servos vs Hybrid Steppers with CS labs controller  (Read 3175 times)

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Re: Servos vs Hybrid Steppers with CS labs controller
« Reply #10 on: October 05, 2017, 02:12:17 AM »
Hi Mick,
can you post some more info about your existing servos, rated torque, rated speed, frame size etc. Replacing them will require matching
specifications which can be tricky as different technologies (brushed DC vs hybrid variable reluctance) will use different figures of merit.

Craig
My wife left with my best friend...
     and I miss him!
Re: Servos vs Hybrid Steppers with CS labs controller
« Reply #11 on: October 05, 2017, 02:04:19 PM »
Hi Craig

 Only just seen your message. Unfortunately have to work. I have the manuals somewhere on PDF will post later. Only just seen your message. Rely appreciate your help.

Cheers
Mick
Re: Servos vs Hybrid Steppers with CS labs controller
« Reply #12 on: October 05, 2017, 02:17:53 PM »
Hi Craig

I have attached the Norwin drive manual. The plate on the servo's reads:

MT30H4-33
C.STALL: TORQUE 2.1nm
MAX RPM 4000
130v
37a
Tacho 9.5
G90-1582

Thought I had a manual for motors will have another look.

Cheers
Mick   
Re: Servos vs Hybrid Steppers with CS labs controller
« Reply #13 on: October 05, 2017, 02:22:52 PM »
Hi Craig

Found the manual for the motors.

Please see attached.

Cheers
Mick
Re: Servos vs Hybrid Steppers with CS labs controller
« Reply #14 on: October 05, 2017, 05:46:58 PM »
Hi Mick,
kool the SEM 30 series looks to be 1.2Nm in absence of fan cooling. That works out to about 192 oz.in.

Remember that a servo retains that torque right up to rated speed whereas a stepper does not. Assume a stepper
has about 1/4 of its rated torque at 1000 rpm. For a stepper to have 192 oz.in at 1000rpm means it rated torque
will be about 768 oz.in .

All you have to decide is 'if my stepper can manage 1000rpm will my axes be sufficently fast for my purposes?'
If not the you are into servo territory, steppers of ANY type are going to struggle at high speeds.

Craig
My wife left with my best friend...
     and I miss him!
Re: Servos vs Hybrid Steppers with CS labs controller
« Reply #15 on: October 06, 2017, 09:01:58 AM »
This is my experience;
after 12+ years, a lot/most full time, I got a CSMIO-IP-S about 1.5 years ago.
I also went to step/dir AC servos about 2015.

Both real industrial 220V and 60V cheap 400W ones, I import in packs of 10.

There is just no comparison.
The servos accelerate to 3000 rpm in 10-20 ms, no-load, yes 0.02 secs or less.

On a full, heavy machine, like a mill/VMC the steppers did very well ... and about 800 rpm in 0.7 secs or so.
With a 200 kg table, 200 kg load.
The smallest servos will do 0.05-0.1 secs to 3000 rpm. (I dont want that. Neither will You.).

On a very heavy Very Good, *industrial* lathe, the 220V ac servos I used and import;
will do full-peak acceleration (probably) in the same 10 ms with a 200 kg carriage, and 2 toolchangers massing 100 kg.
I will never try it, because it is a huge impact load and totally unnecessary.
5 less than-possible is still 5x better than the ("best") steppers- for the same money.

A lathe needs max acceleration at threading pullout and blind-bores pullout, where repeatability is critical and rpm is high-as higher rpm = much better finish/accuracy due to better sfm rates.
Steppers have low dynamic range.
So they are strong, or fast in rpm, but not both, and only semi-accurate relative to any modern servos.

But steppers are really cheap and really good .. where one does not need excellent dynamic range, or very fast speeds AND low speeds OR high accuracy all at once.




Re: Servos vs Hybrid Steppers with CS labs controller
« Reply #16 on: October 06, 2017, 01:22:03 PM »
Hi Joe

Thanks for looking at that I will do some research over the weekend.

Cheers
Re: Servos vs Hybrid Steppers with CS labs controller
« Reply #17 on: October 06, 2017, 01:32:00 PM »
Hi Hanermo

Thanks for your time and the info. What would your opinion be on using my existing Sem Mt30 Servos with a CS labs CSMIO-IP-a analogue controller?

Really appreciate your feedback.

Cheers
Mick 
Re: Servos vs Hybrid Steppers with CS labs controller
« Reply #18 on: October 06, 2017, 01:35:55 PM »
Sorry Craig meant Craig not Joe. Been a long day. >:( >:(
Re: Servos vs Hybrid Steppers with CS labs controller
« Reply #19 on: October 06, 2017, 02:47:27 PM »
Hi Mick,
hanermo is quite correct when it comes to acceleration and speed a well specified AC servo is the best answer. He says also that steppers are good,
not in the same performance league as servos but do the job at a lower cost.

For instance
http://www.ebay.com/itm/Leadhine-86HS85D-NEMA-34-Stepper-Motor-8-5-N-m-1-203-oz-in-Sold-by-Leadshine-/252964922672?hash=item3ae5e26530:g:2YwAAOSwDiBZLRmV
with this driver
http://www.ebay.com/itm/Leadshine-AM882-Digital-Stepper-Drive-DC-80V-8-2A-With-Protection-Function-/272579014364?epid=28004592968&hash=item3f76f9aedc:g:yFwAAOSwSlBYvNoZ
combined cost $170US verses
http://www.ebay.com/itm/400W-Delta-AC-Servo-Motor-Drive-Controller-Kit-220V-ECMA-C10604RS-ASD-A2-0421-M-/111589600603?hash=item19fb422d5b:g:Ug0AAOSwEzxYYdfq
Delta servos are not the cheapest on the market nor are they anything like the most expensive so around $600US. You could buy three steppers and drives
for the price of one servo and drive and still have enuf left over to go and get drunk in celebration.
The question is not really whether servos are better/worse than steppers, with attention to specification they both work well. The question is....is the price
premium for servos justified for your machine? Are you intending production runs for instance?. Will you wife kill you if you buy servos without telling her? LOL

Craig
My wife left with my best friend...
     and I miss him!