Machsupport Forum
Mach Discussion => General Mach Discussion => Topic started by: hughes674 on October 03, 2017, 01:48:37 PM
-
Hi All
Looking for some advice regarding keeping original servos and doing a total upgrade and using Leadshine servo steppers. I have a Denford Senior which has a fanuc ot control. A fault occurred about a year ago but never got to the bottom of it. Decided to do something with it now. Don't really want to throw money at such an old control system.
Considering two options : Option 1 keep the original Sem Mt30 Servos along with the Norwin 2110 drives and use a CS Labs CSMIO/IP-A capable of 0 to 10v for the drives.
Option 2 Try and sell the servos and drives and use appropriate Leadshine Servo stepper motors along with a CS labs CSMIO/IP-M.
Seen some good reviews on the forum about Cs Labs products and would really appreciate any comments.
Many Thanks
Mick
-
Hi,
the hybrid 'servo steppers' are just stepper motors with a smart drive, useful to be sure but its still a stepper with the same limitations of speed
and torque. The premium you pay for the smart drive gets you too little....either get plain steppers and drives but the next size up OR get proper
AC servos and drives and be done with it.
You pay a premium for analogue capable controllers, if you instead stuck with a cheaper step/dir controller you have more budget for a servo
and drive.
Bang for your buck, ordinary 34 or 42 size low inductance steppers with 80V drives are still easily the most cost effective for hobbyists, if
you need more performance the AC servos are the answer...no in between nonsense.
Craig
-
Hi Craig
Thanks for your reply. Haven't really looked at going out and buying new servo motors and drivers due to cost. Was trying to utilize the original servos if it was a better option. Did think that using the servo steppers would cure loosing steps. Did a conversion a few years ago and never got it right. Very limited speed and threading was never very good.
What would you recommend on a cheaper step and direction controller?
Cheers
Mick
-
Hi,
the 80V capable Geckos, Gecko have a great rep but reasonably pricey
ger21, very experinenced CNCer, says:
Get some Leadshine AM882's from Ebay, and some low inductance, high current steppers, and you'll get all the speed and power you need. And they'll run smoother, cooler and quieter than what you have.
Craig
-
Hi,
sorry misread your post, I guessed you were talking about stepper drivers.
I personally use, like and recommend an Ethernet Smoothstepper from Warp9. As it turns out there are a few choices.
Don't buy Chinese, most of its rubbish and little or no help when you get stuck.
Beware also the there are some Chinese knock-offs on Ebay trying to pass as a UC100...don't go there!
Craig
-
Hi Craig
Will look into those control boards. Thanks for your time.
Cheers
Mick
-
Hi,
I can find some documentation about the SEM30 and Norwin drives, but doubt the models I've seen are indentical to yours but none the
less can well imagine that you wish to retain them if they are in working order. That would require an analogue output controller.
As you say CSLabs do a nice unit but around $600 and Vital Systems also have a good reputation but their analogue ready controller is $1200.
Galill is really classy gear but three axis analogue around $2000.
An ESS by Warp9 (step/dir) is $180. The difference between the CsLabs analogue and the ESS is about $400, still not enuf to replace the servos
certainly with AC servos but you may find that good sized steppers and drives can be had for that budget.
My concern would be 'what happens if one of the Norwin drives craps out?' Can I repair it? Could it be replaced and how much? So there is a risk
in retaining the old servos and drives over and above the premium paid for an analogue controller.
Price two 34 size low inductance steppers, big suckers, 800 oz.in or better, 72V supply and two AM882s. When set up properly they should not lose steps
and will be quick if not as fast as the servos they replace. You may like the idea that the smart drives can overcome lost steps but if you are pushing steppers
to the extent that they start losing steps then its probable that the drives will throw a 'following fault' error. Don't be taken in by the advertising hype.
Craig
-
Hi Craig
Norwin are still repairing the drives as I had one repaired a year or so ago. Only cost about £100 (May have been lucky). I think it would be nice to use the servo's and existing drives but after further thought it really makes no sense. At some point in the future maybe not this year someone will need those servo's and drives to fix a machine and probably pay decent money. So I think replacement with steppers is the way I will go.
If I was to go for ordinary steppers without encoders is there any particular brand you would recommend? There loads available all over the net but what do you buy?
I looked at the Smooth stepper and found a company in the Uk that has them. Obviously that still needs a breakout board so need to take that into account and what to use? The Cs Labs CSMIO/IP-M 4 is around £270 and doesn't require BOB.
Really want to get this one right. The last conversion was poor to say the least.
Cheers
Mick
-
Hi,
The Cs Labs CSMIO/IP-M 4 is around £270 and doesn't require BOB.
Check out the restricted functionality, it doesn't look quite as appealing.
Plain two phase steppers are as you say very common. I have no recomndation to make that favours one manufacturer over another.
Not all manufacturers list the inductance but is an important figure of merit, go for the least in a given size. 800+ oz.in 34 size are likely
to be 6+A try to find units with inductance less than 5mH.
Craig
-
Hi Craig
Thanks for the info. Will do some more research.
Cheers
Mick
-
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
-
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
-
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
-
Hi Craig
Found the manual for the motors.
Please see attached.
Cheers
Mick
-
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
-
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.
-
Hi Joe
Thanks for looking at that I will do some research over the weekend.
Cheers
-
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
-
Sorry Craig meant Craig not Joe. Been a long day. >:( >:(
-
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 (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 (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 (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
-
Hi Craig
Buying new servos is not an option. Looking for more feedback on using existing DC servos. With Cs Labs controller.
Cheers
Mick
-
Hi Mick,
yeah, servos even cheap ones are still expensive and if you try to buy to match your budget then you are entirely likely to end up with under
specified servos and all that doe-ray-me would be wasted. Go on....your amongst friends....you can admit that the missus will discombobulate you!
What condition are your existing servos in? I'm wondering if you could not build a simple analogue circuit and hook it to your drivers to see how
the servos responded. You certainly don't want to be investing in controllers if your existing servos and/or their drives are faulty.
My training and job is electronics. In the situation where I was trying to evaluate your machine for overhaul/repair or modification I would grab
my function generator and set it to sinusoidal wave of about 5V peak to peak at 1/4 Hz and put that directly into the analogue input of the drives.
Provided you didn't crank the frequency up to much and therefore try to accelerate beyond the servos max then it should move backwards and
forwards smoothly. A sawtooth wave could also be used; the reversal of a sawtooth wave represents a spike in acceleration. The need to keep the
amplitude down and the frequency of reversal low would be paramount otherwise the acceleration spikes would be such that the servo has no real
chance to stay in sync with the input and it would fault out 'following error'
You may have noticed on Ebay Direct Digital Synthesis function generators of modest but adequate performance can be had for less than $20, God
bless or Chinese friends. If you don't have a signal generator or know someone you could borrow one then one of these cheap units would do the
trick.
Craig
-
Hi Craig
Lol yes the wife would have a fit or insist on spending the same on lotions and haircuts.
I don't think there are any issues with the servo's as they were working fine last year up until a point when I changed the membrane on the operator panel keyboard. Since then the keyboard or part of it stopped working not allowing me to do anything with the machine.
Do like the idea of what you are saying though but you will have to go slow. Ill have a look at the Norwin wiring manual to see if I follow you.
Cheers
Mick
-
Hi Mick,
Lol yes the wife would have a fit or insist on spending the same on lotions and haircuts.
don't want too much of that going on, the UK balance of trade may never recover!
Even a simple potentiometer with a 9V battery would be enuf to cause the servo to move.
Twiddle the pot backwards and forwards and the axis should follow. With just one 9V battery I would expect the axis to be restricted to one half
its travel, the right half say, and if you reversed the battery then it would work in its left half. You will have to coax it, if you attempt to cause the
axis to move from point A near one end of it travel to point B at the other end instantaneously as in changing the battery polarity it will fail as a
following error. None the less you should be able to get the axes to move. It will probably require an enable signal.
Given that you are of the opinion that the servos are OK then maybe fooling around with bits of wire and batteries doesn't appeal.
Craig
-
Hi Craig
Happy to knock a circuit up. Have loads of electronic stuff about. I can make a circuit that has 0 to 10v adjustable. The frequency part was confusing me in your previous post.
Would I connect this to pins 4 and 5 and the Norwin Drive?
Cheers
Mick
-
Hi Craig
Sorry meant pins 10 and 11?
Cheers
Mick
-
Hi,
yes. Looks like all of it needs to be hooked up. the -15V,0,+15V supply outputs can be used to synthesise the command input. An +15V enable signal
must be applied to term #8.
0V is applied to pin #10 and a voltage between +10V and -10V applied to pin #11. This voltage could the output of a pot spanning -15V and +15V
or a slowly varying signal from a signal genertor. The speed of the servo should follow the input voltage.
The servo/drive combination has no ability in itself to detect or fault out under following error. It does have an armature over current fault, Thus if the
command input is stepped in a sufficiently aggressive manner the servo will attempt to follow but fail to do so as the armature goes over-current and
faults out.
If you had an oscilloscope you could monitor the encoder output to ensure that it is available for the position control loop.
Craig
-
Hi,
what sort of encoder is fitted?. It will have a bearing on the controller.
Craig
-
Hi Craig
Thanks for the info. Will give it a go tomorrow. The encoders are ACCU CODER 755.
5VDC.
Cheers