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View Full Version : The Best Steppers/Servos Setup Thread



andy_con
22-03-2017, 01:29 PM
I know different people have different opinions, but what have people used in terms of steppers/servos and what do you regard as the best. so servos and drivers.

please don't claim something is the best if you have never used them, just reading something someone wrote web doesn't count for a lot.

I had a cracking day at southern manufacturing and electronics yesterday and I really want to improve the setup on my triac.

currently my triac has stock steppers in and stock drive cards, id love to improve. id like to get more speed for when doing g00 commands, currently my max and better repeatability.

I wouldnt mind spending a few quid on a setup that's quality and offers good results.

let the banter begin...

m_c
22-03-2017, 06:20 PM
Your budget is the limit!
However, the problem with a Triac, is you're limited on space to mount servos, unless you start doing some major rejigging of motor mounts. As part of my retrofit, I measured things to see how much room is available for upgrading at some point. X would need the motor flipped and mounted in front/behind the table other wise it'll hit the enclosure. Y would either need the motor flipped and sticking out the rear, or the ballscrew extended to give enough room. I think Z is the only one with plenty room to keep the existing mounting position.

However, ignoring fitting issues. Drive upgrade will give a noticeable speed improvement. I've got Leadshine EMs fitted, and I'm no where near pushing them to the limit. I still need to see just how fast I can push the original motors, but not got that far yet, as I'm still fixing/finishing other things.
Modern motors would also give a boost, but I'd rather spend money on servos.


I've got Kinco servos (400 and 700W) on my lathe, and they work well. I'm running them using +/-10V using a KFlop+kanalog, and they tuned up well.
I know DaveK fitted some cheaper Chinese servos to his Bridgeport, but the lack of separate logic power supply (means if you kill power to the drive, you lose position - better drives use a separate 24V power for logic, so the encoder works even when drive power is lost), and I know he had some issues tuning them. I am tempted to get one to try, but I've yet to find a suitable use for one.

Boyan Silyavski
23-03-2017, 05:43 PM
IMHO used Panasonic or Samsung Servos +drives + cables from flea bay in a very good shape are unbeatable as quality per $. Around 250- 300 the pair, having in mind new only drive is 500 wholesale price, same for motor. quality cable is 100 per cable at least for 4-5m. So do your statistics.

Most of these motors/ mine including/ are rated flat line to 3-4krpm and falling curve 6k rpm. Meaning you can make exceptionally fast and precise machines. They have tons of functionality a cheap chinese drive will never have and a visual software for free usually. best thing is that almost all of them could work on slow BOBs as the have internal gearing and so on, not that i advise to do so.

From what i have bought till now, all were like new without problems. Of course i buy the best looking from a certain seller. Have to check the name if you are interested. Spartan or sth similar it was.

PS. The said brands usually accept all kind of signals good for us, including differential.

andy_con
23-03-2017, 11:40 PM
but the machine doesn't need the worlds biggest servos, its not like it will take massive heavy billets. are there no small decent servos?

the table doesn't need to move at 1000mph.


Your budget is the limit!
However, the problem with a Triac, is you're limited on space to mount servos, unless you start doing some major rejigging of motor mounts. As part of my retrofit, I measured things to see how much room is available for upgrading at some point. X would need the motor flipped and mounted in front/behind the table other wise it'll hit the enclosure. Y would either need the motor flipped and sticking out the rear, or the ballscrew extended to give enough room. I think Z is the only one with plenty room to keep the existing mounting position.

However, ignoring fitting issues. Drive upgrade will give a noticeable speed improvement. I've got Leadshine EMs fitted, and I'm no where near pushing them to the limit. I still need to see just how fast I can push the original motors, but not got that far yet, as I'm still fixing/finishing other things.
Modern motors would also give a boost, but I'd rather spend money on servos.


I've got Kinco servos (400 and 700W) on my lathe, and they work well. I'm running them using +/-10V using a KFlop+kanalog, and they tuned up well.
I know DaveK fitted some cheaper Chinese servos to his Bridgeport, but the lack of separate logic power supply (means if you kill power to the drive, you lose position - better drives use a separate 24V power for logic, so the encoder works even when drive power is lost), and I know he had some issues tuning them. I am tempted to get one to try, but I've yet to find a suitable use for one.

andy_con
23-03-2017, 11:42 PM
ive got a PMDX126 in my triac so a pretty decent board.

link me up...


IMHO used Panasonic or Samsung Servos +drives + cables from flea bay in a very good shape are unbeatable as quality per $. Around 250- 300 the pair, having in mind new only drive is 500 wholesale price, same for motor. quality cable is 100 per cable at least for 4-5m. So do your statistics.

Most of these motors/ mine including/ are rated flat line to 3-4krpm and falling curve 6k rpm. Meaning you can make exceptionally fast and precise machines. They have tons of functionality a cheap chinese drive will never have and a visual software for free usually. best thing is that almost all of them could work on slow BOBs as the have internal gearing and so on, not that i advise to do so.

From what i have bought till now, all were like new without problems. Of course i buy the best looking from a certain seller. Have to check the name if you are interested. Spartan or sth similar it was.

PS. The said brands usually accept all kind of signals good for us, including differential.

andy_con
24-03-2017, 12:19 AM
ive heard this is a good start to a good setup

http://www.zappautomation.co.uk/electrical-products/cnc-motion-controllers-18/motion-controllers-from-cs-labs/csmio-ip-a-ethernet-motion-controller-analog-10-v.html

m_c
24-03-2017, 12:20 AM
but the machine doesn't need the worlds biggest servos, its not like it will take massive heavy billets. are there no small decent servos?

the table doesn't need to move at 1000mph.

There are, but gearing is the problem.
Stock steppers are 1.1Nm stall, with a gearing ratio of 12:30, giving roughly 2.75Nm at the screw.

A 50W 3000rpm servo, which from Kinco is 83mm long (should fit in a similar place to the steppers), gives 0.16Nm. So to get similar torque you need in the region of 17:1 gearing, and you limit screw speed to 176RPM (roughly 880mm/min).
Move to a 100W version, which from Kinco is 110mm long (I think this was very borderline for fitting to the X, and wouldn't fit on the Y), gives 0.32Nm. Ratio needed is about 8.5:1, and you'd get 1.6m/min speed. If you could manage the gearing ratio, this size would probably be a good match specification wise, but 8.5:1 involves a very big pulley. A gearbox would be a good option, but you add cost, and length.
A 200W 3000RPM servo, again from Kinco is about 120mm long, and gives 0.7Nm continuous torque. You need a ratio of about 4:1, which is very achievable., and you'd be up over 3m/min if you ran it at full speed.

Off course all those figures are based around the continuous/rated torque of the motor. Instantaneous/peak torque is typically 2-3x the continuous figure, but you normally rely on that for acceleration, which is where you should get the real benefit over steppers. If you were to run the figures above using the peak torque, then you would have to limit acceleration, and performance gains would be far more limited.

IIRC, the servo Triacs used about 200W DC servos. I'm sure I read the Y servo stuck out the back of the machine, but I've got no idea how the X was fitted.

andy_con
24-03-2017, 12:25 AM
I'm guessing all the leadshine and other Chinese AC servos on ebay are naff?

m_c
24-03-2017, 01:17 AM
I'm guessing all the leadshine and other Chinese AC servos on ebay are naff?

Some of them are perfectly good. Kinco is Chinese. Leadshine is good.
The big thing is making sure whatever you buy will do what you expect it to, and comes with reasonable documentation.

Skiprat
24-03-2017, 07:28 PM
I bought a full set up of hybrid closed loop stepper motors and associated drivers etc (Purelogic and leadshine) from Zappautomation a few years back and have had nothing but praise for the setup and zappautomation.
Closed loop does exactly what i wanted and i think i oversized the hybrid steppers but at least i can sit on the machine and take a ride...obviously only done under the influence of alcohol ..:ambivalence::hypnotysed::sour:

Tommy

andy_con
24-03-2017, 08:14 PM
there are lots of things like this over ebay

http://www.ebay.co.uk/itm/CNC-AC-Servo-Motor-750W-Drive-Kit-2-39NM-NEMA32-3000RPM-20Bit-Absolute-3M-Cable-/262605862329?hash=item3d248775b9:g:6fgAAOSwMgdXyS7 x

and even cheaper stuff??

http://www.ebay.co.uk/itm/EU-Stock-Nema34-8N-m-Servo-Motor-Closed-Loop-116mm-HSS86-Driver-for-CNC-Router-/272602665389?hash=item3f786291ad:g:b14AAOSwoBtW58K V

I don't mind spending a few quid to get good results

Boyan Silyavski
24-03-2017, 08:53 PM
link me up...

usedparts-pk (http://www.ebay.com/usr/usedparts-pk) He is very decent seller from Korea. Check his listings for servo motors and drives and combos. Normally he will have nice 400w packs. Most of all he checks them, have seen videos, has 100% feedback and can combine for you stuff for better price even, outside of ebay also.

m_c
24-03-2017, 09:02 PM
there are lots of things like this over ebay

http://www.ebay.co.uk/itm/CNC-AC-Servo-Motor-750W-Drive-Kit-2-39NM-NEMA32-3000RPM-20Bit-Absolute-3M-Cable-/262605862329?hash=item3d248775b9:g:6fgAAOSwMgdXyS7 x

and even cheaper stuff??

http://www.ebay.co.uk/itm/EU-Stock-Nema34-8N-m-Servo-Motor-Closed-Loop-116mm-HSS86-Driver-for-CNC-Router-/272602665389?hash=item3f786291ad:g:b14AAOSwoBtW58K V

I don't mind spending a few quid to get good results

750W would be overkill for a Triac. I'd aim for 200W, or maybe 400W.

The second link is actually a closed loop stepper system. Technically it is servo system, however it won't have the same performance as what's more commonly referred to as a servo system.

I had been hoping DaveK would of chimed in with his views on the generic Chinese servo systems, but I guess he's too busy playing with his new toy...

Davek0974
24-03-2017, 09:39 PM
Hi all,

I got my servo's from AliExpress direct from China, they are fitted to a Bridgeport mill(ex manual style machine) I got 700W on X&Y and 400W on Z.

Having only used steppers until this job, i was not expecting them to be as good as they were as the Nm figures do not compare with steppers at all. I used a CSMIO IP-A with 10-0-10v control.

The issues i had/have are all tuning related really - the manual i was sent by the guy was in strong Chinglish so not really much use to a beginner like me. To get a really good tune i am convinced i need to alter the parameters in the drives but cannot do this.

The tuning in CS Labs plugin is all i have so worked with that. It is a time consuming process, forget the auto-tune ;) Apart from a slight resonance on the Z drive I have it running really well now, very little following error and good acceleration, top speed is pretty low at 2500mm/min but this is only an old Bridgeport so no point in flogging her to death. Acceleration was more important to stop corner-rounding in Mach 3's trajectory planner.

I must admit that i had the 400W on the bench to play with and even running at maybe 5 rpm i could not stop the shaft rotating no matter how hard i grabbed it, the torque is phenomenal and start / stops at speed are sharp enough to make the motor jump off the bench!

I could probably have fitted smaller motors on the mill, they have 2:1 reduction drives but this size seemed a good price :) I think they were about 400 for 700W with drive and 5m cables.

I would love to fit them to the plasma cutter, may do one day.

JAZZCNC
25-03-2017, 11:49 AM
The issues i had/have are all tuning related really - the manual i was sent by the guy was in strong Chinglish so not really much use to a beginner like me. To get a really good tune i am convinced i need to alter the parameters in the drives but cannot do this.

Ok I've been watching and stayed out of this until now because don't have any experience with Triac's or there power requiements but need to make this clear to defend chinese servos.
Dave I'm not having a go at you so please don't take it this way just want to point out for sake of others that the parameters can be changed in the drives to give better tuning. Yes it's fiddly process with lots of parameters and the Chinglish manual doesn't help or make it simple but this is why they are so cheap.
If folks want simplicity in tuning then buy branded name but expect to pay the same amount of money for one axis as you would 3 axis worth from China and still have spare change.!

To the OP.
In terms of performance then servos are no comparison to steppers in most cases. However that doesn't mean Servos are always better for the application. IMO for DIY level Mill or router then steppers are perfectly fine. Much simpler with far less hassle for not lot of money.

I can tell you with absolute confidence because I fit both on nearly all machines I build that the AM or EM drives give excellent performance which I've yet to see beaten for the money. Reliabilty so far after fitting good few hundred has been 99.9% with only one none starter. By that mean never had one fail in use and only one which didn't work out of the box.

The Cslabs Controllers are Top notch which ever you use and again you won't get better.

Regards Steppers then provided you buy ones with sensible spec in terms of inductance etc then they all pretty much work the same.

What I will say is that on Denford and Boxford router conversions I've done where all has been replaced with New steppers, AM882 drives and Cslabs controllers the performance difference is Night and Day turns the machine into different animal.

Davek0974
25-03-2017, 12:29 PM
No worries Jazz, i fully realise that you get what you pay for :) All it needs is a knowledgeable person to identify the Pid parameters in the manual and sort out what does what :) Trouble is they dont even call them Pid :)

One drive not mentioned yet is the hybrid stepper-servo - a stepper with an encoder mounted and a suitable drive. I nearly fitted these on the Bridgeport but fell for servo's instead. They do sound interesting though.

Skiprat
25-03-2017, 07:43 PM
Hybrids are what i have and mentioned them earlier in the thread......excellent piece of kit and work brilliant.

I have two on the y axis, one on x and a smaller one on the z....all connected with leadshine drivers and purelogic boards....

Excellent but i did pay 2K+ for set up inc all power supplies etc...

Tommy

m_c
25-03-2017, 08:35 PM
Andy, the main thing you have to consider, is what do you want to achieve?

Faster rapids, faster acceleration, better positioning, just to spend some money???

JAZZCNC
25-03-2017, 08:42 PM
Closed loop steppers are just now becoming cheap enough to be worth thinking about. I've just started fitting them to machines but In truth they offer very little more than normal stepper (open loop) when sized and tuned correctly. The smaller ones do have the advantage of using 3phase motors which give smoother action than 2 phase but other than that there isn't any advantage in power terms.
The closed loop side isn't really anything to pay thru the nose for IMO because at best all it does is throw a fault if position is lost. Thou to be fair this is the same for servos which only close the loop between motor & drive rather than fully closing the loop back to control.

Servos however get there advantage from the smooth linear power and speed they provide but the same holds true that if pushed too hard or tuned to high they will still lose position and the only advantage then is the fact they fault the drive. However this does come with a cost, both in money and technical knowledge required. They don't tolerate any corner cutting in control system or sloppy ness in machine. This means often the cost doesn't stop at just buying the servos.
Standard steppers cannot do this but if sized correctly and tuned correctly they are very accurate and reliable. They don't match servos in performance but they do Match Closed loop steppers in every way. They are simple and reliable which is why they suit DIY perfectly.

JAZZCNC
25-03-2017, 08:58 PM
Andy, the main thing you have to consider, is what do you want to achieve?

Faster rapids, faster acceleration, better positioning, just to spend some money???

All Good Questions but also while at it ask your self WHY.?

Do you really need machine that travels at light speed.? . . . . . At this size I'd say 100% not.!!
Do you really need machine that goes from 0 to 100 in 0.01's.? . . . . . . . . . . . Probably not.!!
Can machine handle the higher speeds.? . . . . . . . . . . . . . . . . . . . . . . . . . . Probably Not.!!
Can the rest of machine match the positioning accuracy.? . . . . . . . . . . . . . . .Probably not.!!

So only probable reason is because got money burning hole in pocket which is fine if your loaded.:yahoo:

Chaz
26-03-2017, 04:17 PM
My Triac uses 400W Kinco servos and works well.

andy_con
26-03-2017, 10:57 PM
were not talking about money here were talking about a good setup and a good setup doesn't come cheap.

anything is cheaper than buying datron or haas machine.

Zeeflyboy
26-03-2017, 11:08 PM
I bought a full set up of hybrid closed loop stepper motors and associated drivers etc (Purelogic and leadshine) from Zappautomation a few years back and have had nothing but praise for the setup and zappautomation.
Closed loop does exactly what i wanted and i think i oversized the hybrid steppers but at least i can sit on the machine and take a ride...obviously only done under the influence of alcohol ..:ambivalence::hypnotysed::sour:

Tommy

I'm also running closed loop leadshine steppers and drivers, very happy with them.

andy_con
26-03-2017, 11:15 PM
so these?

http://www.ebay.co.uk/itm/CNC-Leadshine-Closed-Loop-3-phase-Hybrid-Servo-Drive-HBS57-Driver-Servomotor-/281993490339?hash=item41a81f2fa3:g:iQEAAOSwsN9XA89 p

Zeeflyboy
26-03-2017, 11:37 PM
Yes, looks to be the same as what I'm using.

They are nice, work great for me... but then I've never used servos so can't comment on that front. Even if you just view them as normal steppers they are a good (if not the cheapest) option in my opinion, they are quite literally plug and play with no tuning required at all and are very quiet, smooth at all speeds, stay very cool in operation and have the must-have features such as stall detection and error signal.

It was quite fun playing around with the closed loop system before installing them. You can fit a coupling to the shaft and then try to prevent it from rotating as an experiment. Long before it will throw a fault and disable the drive, you can see a sort of rubber band effect.... where a normal stepper would have thrown steps, these keep trying to fight you and then just ping back into place once you release them.

In theory the closed loop stuff also has better torque curves, acceleration and speed due to the controller having a better idea of what position the motor is actually in, along with higher efficiency and lower noise.

Edit:

Quite an interesting read on closed vs open loop steppers where they've actually done some lab testing http://www.motioncontroltips.com/torque-better-efficiency-closed-loop-versus-open-loop-stepper-systems/

Boyan Silyavski
27-03-2017, 01:46 AM
Servos i like just for the pure pleasure of watching them move fast and silently. I could stand an hour watching my machine doing ultra fast high speed machining just cutting the air... Its just pure joy watching 200kg gantry accelerate, in fact its quite unsettling sometimes and my hair raises when i run a slow program and when program finishes and machine go to 0 with astonishing speed. For sure wakes me up.

andy_con
27-03-2017, 01:42 PM
are they actually proper servo's or "Chinese" servos?

the price is great, cheaper than I was expecting to pay for a new setup and if they work well then excellent

http://www.ebay.co.uk/itm/CNC-Leadshine-Closed-Loop-3-phase-Hybrid-Servo-Drive-HBS57-Driver-Servomotor-/281993490339?hash=item41a81f2fa3:g:iQEAAOSwsN9XA89 p&clk_rvr_id=1190344795218&afsrc=1&rmvSB=true

JAZZCNC
27-03-2017, 09:10 PM
are they actually proper servo's or "Chinese" servos?

the price is great, cheaper than I was expecting to pay for a new setup and if they work well then excellent

http://www.ebay.co.uk/itm/CNC-Leadshine-Closed-Loop-3-phase-Hybrid-Servo-Drive-HBS57-Driver-Servomotor-/281993490339?hash=item41a81f2fa3:g:iQEAAOSwsN9XA89 p&clk_rvr_id=1190344795218&afsrc=1&rmvSB=true

They are 100% steppers not servos. They are however 3 phase steppers rather than 2 phase which is standard hybrid stepper. This means they run little smoother with slightly higher torque. Also take note that larger motor sizes above 3Nm are only 2 phase so offer no advantage over normal stepper.

Now don't be fooled by Comparison Zeeflyboy posted because IMO it wasn't a fair comparison.? They made no mention of the open loop stepper drive used and given the results which are massively off from my experience between open and closed loop steppers suggests to me they used Old technolgy drives.

New modern Digital drives like EM/AM from lead shine are world apart from old Analog drives and my experience with using both (I was one the first to test leadshine Closed loop drives) is that other than being little smoother because of motor difference there isn't much between them. In fact the AM/EM can be run with more voltage so can be run faster.

The Example Zeeflyboy gave of motor playing catch up is great when playing on the bench but in real world means very little because if did fall behind the error will still show in the finished part. The controller knows nothing about the error because the loop is only closed between drive & motor. This means there will be discrepancy and errors between axis has the controller just carrys on pumping out pulses for each axis and doesn't allow for fact one axis falling behind.
This means there is no difference between Closed or Open loop in real world of cutting provided the open loop is correctly tuned/sized.

The only difference or advantage of closed loop is that you can set the Max following error allowed in which case it will then fault the drive. This is exactly how servo drive works and why they get the name "Hybrid servo" because they work just like servos do. However they don't have the positional accuracy or linear torque servo's provide.
People think that because they always return to same place due to encoder positioning this is good. Which it is to some small degree. However it can also mask other issues in the system which show in the work but would normaly be seen due to not coming back to same place.!! . . . Things are not always good as they appear.!

To me bottom line is if you want high feeds/accelleration/smoothness then you need REAL servos. If you just want accurate machine which is reliable and easy to setup etc then save your money and go with standard stepper system with Digital drives like EM/AM.

Zeeflyboy
28-03-2017, 09:45 AM
are they actually proper servo's or "Chinese" servos?

the price is great, cheaper than I was expecting to pay for a new setup and if they work well then excellent

http://www.ebay.co.uk/itm/CNC-Leadshine-Closed-Loop-3-phase-Hybrid-Servo-Drive-HBS57-Driver-Servomotor-/281993490339?hash=item41a81f2fa3:g:iQEAAOSwsN9XA89 p&clk_rvr_id=1190344795218&afsrc=1&rmvSB=true

They aren't servos at all, they are closed loop steppers...

Jazz - all very well saying don't be fooled by that link, but I have yet to see any quantitive testing that shows there is no or very little difference between closed loop and open loop steppers... all the comparisons I have seen have shown them to be superior. Have you come across any evidence to support the assertion that there are open loop systems that can get close to the efficiency of a closed loop system? The 3 phase ones also have a higher resolution at 1.2 degrees per step rather than the 1.8 of most 2 phase steppers, which is about a 30% improvement.

As for being able to use higher voltage, the model he linked to is also rated to 2,000rpm - higher voltage is unlikely to help you get beyond that speed on traditional drives I would say? The closed loop steppers manage to maintain higher torque at high speeds too when compared to open loop which is useful to consider when talking about performance at higher speeds.

As to the playing catch up - it really depends on what you are making and where the problem occurs. Lets say your g-code has a slight blip and you lead out from a contouring cut into a full depth cut of the surrounding stock (it's happened to me!) - were open loop steppers to lose some steps from that they would then go on to ruin your work piece where the closed loop would have caught back up before it even moved to the next operation... also depending on the work and the point that it happens, a small defect may be acceptable (or may not even show on the final piece if it happened while clearing or doing any work away from a final contour or surface) and the rest of the operation would still be dimensionally correct. Lost steps would go on to offset the entire work from then on and completely ruin the whole piece.

As I said, if you just view them as normal steppers I think they are a good choice, and arguably one of the better choices if staying with steppers. They aren't really that much more expensive than good digital drives and decent quality stepper motors but do honestly have some advantages too so if the extra expense isn't an issue then I don't see why you shouldn't consider them among your options. Personally I just consider them as a high end stepper system, and they've fulfilled all my expectations so all I can say is I've been very happy with them

:beer:

JAZZCNC
28-03-2017, 07:37 PM
They aren't servos at all, they are closed loop steppers...

Jazz - all very well saying don't be fooled by that link, but I have yet to see any quantitive testing that shows there is no or very little difference between closed loop and open loop steppers... all the comparisons I have seen have shown them to be superior. Have you come across any evidence to support the assertion that there are open loop systems that can get close to the efficiency of a closed loop system? The 3 phase ones also have a higher resolution at 1.2 degrees per step rather than the 1.8 of most 2 phase steppers, which is about a 30% improvement.

Zeeflyboy- The reason you probably haven't seen any evidence in tests is because they are trying to sell or promote Closed loop. Also they are not comparing Apples with Apples in most cases.

Like you rightly point out Closed loop motors are 1.2degree and 3 phase. I'd bet strong wagger they are using 2phase 1.8 degree motors on the Open loop test.
I'd also put another wagger that they are not using Digital drives on the Open loop but old Analog drives.

True test would use Digital drives with 3phase motors (which can be bought.) In this case the only difference is the Encoder and Closed loop side of the DSP which doesn't make any difference to performance of the motor. Closed loop drive is just Digital drive with Closed loop option inside the DSP. This can be proven by turning the closed loop side off which can be done via software in some drives. The performance of the motor doesn't change with it turned off.

Do this then the only difference between Digital drives like leadshine EM/AM and the Closed loop system is the motor which is connected. My argument was never that standard steppers equal 3 phase steppers and I said all along 3ph motors are smoother which is mostly because of the 1.2deg resolution.

Now my comments regards standard 1.8 Degree steppers and Digital drives comes from years of experience building machines which use them. My comments regards Closed loop come from using and testing them on several machines over the last 18mths. I can tell you and everyone else that the difference in performance is minimal, yes slightly smoother but thats about it.
Now where the AM/EM drives do trump the Closed loop is that they have 80Vdc limit not 50Vdc. This translates to more speed and more torque which for router is crucial, not so much for mill.

Your argument regards Catching up is weak at best because simple truth is that if falls behind there will be some error. Chances of this happening only on that one axis while others are not moving and on part of the work piece which is not important have Odd's higher than winning the lottery.
What happens if this happens 10hrs into 12hr job of 3D mould with 3 axis moving together cutting expensive piece of aluminium.?? . . . . What good is Closed loop here if falls behind.?

Also if the Open loop is losing steps then it's in-correctly tuned or pushed too hard. In which case this would happen to closed loop just the same if pushed past it's capabilty's. Only difference is it would or should Fault before stalling. Good Digital drives like EM/AM will however quickly Fault when it see's Stall so again very little difference because both have messed up.!!

Now to the Price argument.! . . . I agree Closed loop are now lot cheaper but still they have way to go. AM882 can be bought for 60-70 3-4nm Motor for 35. The Leadshine Closed loop shown was 179 and is only 2Nm.!! . . . . Nearly 80 difference PER AXIS. for very little gain other than bragging rights.!!

Boyan Silyavski
29-03-2017, 08:17 AM
I never understood the significance of closed looped steppers at that price point. Plus i pointed already a couple of times in forums where cheapest servos could be bought.

400w AC servo motor could be bought for ~180$ together with drive. JMC motion. 60ASM400 +MCAC808 , not sure of actual prices so have to check. Also they sold the closed loop stepper 3nm motor and 2HSS86H driver for around 130$ . that prices were when you buy 4x. Obviously a PSU must be fashioned. That includes cables so price was great.

So forget about the Leadshine for the moment, there are other players. That was an year ago. Now may be even sth else new on horizon.

Zeeflyboy
29-03-2017, 07:42 PM
I never understood the significance of closed looped steppers at that price point. Plus i pointed already a couple of times in forums where cheapest servos could be bought.

400w AC servo motor could be bought for ~180$ together with drive. JMC motion. 60ASM400 +MCAC808 , not sure of actual prices so have to check. Also they sold the closed loop stepper 3nm motor and 2HSS86H driver for around 130$ . that prices were when you buy 4x. Obviously a PSU must be fashioned. That includes cables so price was great.

So forget about the Leadshine for the moment, there are other players. That was an year ago. Now may be even sth else new on horizon.


Seems to generally be about $220-250 (before postage) to source from china for those? Comes in at around $100 more than the leadshine closed loops per axis from the same sources (which vary from around $120-170 before postage), certainly not bad if they work well.

They are definitely on the cheaper end of what I've seen for servos (400W I've always seen more for $450 ish), are they what you are using? Could be tempting to try out at that price in the name of... science...

Jazz - we'll have to agree to disagree on the usefulness of the closed loop in terms of error, I'm still of the opinion that for certain applications it is nice to have even if not essential. I believe it worked out at around 130ish per axis for me all costs included (although granted the dollar was significantly weaker back then pre-brexit) so a premium of about 40 quid per axis over the setup you are speaking of.

I just want to be clear though, I have absolutely no doubt that the setup you are speaking of is fantastic... I'm sure had I gone with those I would be equally happy. Yet again I am just sharing my experience that I have been very happy with the performance of my easyservo setup, it's up to the individual to decide what features they particularly value.

andy_con
29-03-2017, 07:55 PM
I'm assuming people are referring to these?

http://www.ebay.co.uk/itm/CNC-400W-Digital-MCAC806-Servo-driver-AC-servo-motor-CNC-KIT-Router-Mill-Plasma-/251405625254?hash=item3a88f167a6:g:4Q8AAOSwsN9XCzy W

Boyan Silyavski
29-03-2017, 08:40 PM
I'm assuming people are referring to these?

http://www.ebay.co.uk/itm/CNC-400W-Digital-MCAC806-Servo-driver-AC-servo-motor-CNC-KIT-Router-Mill-Plasma-/251405625254?hash=item3a88f167a6:g:4Q8AAOSwsN9XCzy W

referring to similar as that combo but for 180$ , bought directly from JMC motion.

Greeny
29-03-2017, 08:57 PM
These servos look interesting (the SDSK models), price is around $250-$400 per motor, but interestingly they have built in drivers, so all they need is 75V Dc and Step & Dir signals.
https://www.teknic.com/products/clearpath-brushless-dc-servo-motors/clearpath-sd/

$319 (~257) +postage gets you a 4.4nm nema 23 that still gives ~0.9Nm at 2500rpm !!
https://www.teknic.com/model-info/CPM-SDSK-2331S-RLN/

They have a USB port for diagnostics & tuning and have autotune software to run once installed on the machine.
I have no idea how effective the autotune is, or how good the motors are but they get generally good reviews on Youtube from our American "cousins".

I must admit to being interested, but at about 300 an axis (with postage, import duty etc), thats more than double an AM882+Nema 23 Stepper!

JAZZCNC
29-03-2017, 09:32 PM
Jazz - we'll have to agree to disagree on the usefulness of the closed loop in terms of error, I'm still of the opinion that for certain applications it is nice to have even if not essential.

If you paid 130 for genuine Leadshine closed loop inc delivery then you've bought very cheap. I've never seen any that cheap before or after brexit so well done.

We don't actually disagree too much, Closed loop are worth having over Standard steppers if only because of the 3phase 1.2 degree motors but only if there isn't great price difference. 80 or even 50 per axis is too much IMO
I've actually got 12 sets of closed loop on route to me which will be fitted to routers but this is only because they are larger motors and hardly any price difference between standard motors/drives.

JAZZCNC
29-03-2017, 10:07 PM
These servos look interesting (the SDSK models), price is around $250-$400 per motor, but interestingly they have built in drivers, so all they need is 75V Dc and Step & Dir signals.
https://www.teknic.com/products/clearpath-brushless-dc-servo-motors/clearpath-sd/

Don't understand why would want drives clattering up down with motors getting covered in shite. Given time can't do them any good. They are great for machines working in clean enviroments like pick n place etc but wouldn't stick them on router or Mill.

Greeny
29-03-2017, 11:13 PM
Don't understand why would want drives clattering up down with motors getting covered in shite. Given time can't do them any good. They are great for machines working in clean enviroments like pick n place etc but wouldn't stick them on router or Mill.

Fair point, I suppose it depends on how well they are sealed.
Not sure i want to spend 300 to find out though :whistle: