The Best Steppers/Servos Setup Thread

[JAZZCNC]

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]

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]

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]

I'm assuming people are referring to these?

http://www.ebay.co.uk/itm/CNC-400W-D...8AAOSwsN9XCzyW

[Boyan Silyavski]

I'm assuming people are referring to these?

http://www.ebay.co.uk/itm/CNC-400W-D...8AAOSwsN9XCzyW

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

[Greeny]

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/clea.../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]

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/clea.../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]

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

[JAZZCNC]

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.