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Agathon
10-07-2017, 12:37 AM
This is probably a bit premature, but I'm thinking of fitting servos to my Fehlmann Picomax 50 CNC table. Originally it had massive Superior Electric steppers rated at 2.1Nm nominal torque.

I like the Teknic ClearPath integrated servos and I think their CPM-SDSK-3421S-RLN will do the trick - https://www.teknic.com/model-info/CPM-SDSK-3421S-RLN/

However, I like a bargain, so I've been wondering about buying used servos and drivers from eBay. The trouble is I know nothing about servos! Can anyone give me some basic guidance on what to look for and what to avoid?

Boyan Silyavski
10-07-2017, 07:38 AM
Hi,
here i organised some info. If something not clear, please ask:

If buying new servos:
-Look for the servos to come with cables if not integrated
-www.jmc-driver.com the cheapest servos around that i know of

If buying second hand:
-cables and connectors, at least the connectors. If servo cables are needed TME.eu sells the cheapest quality cable for servos and generally speaking. Some times a great deal servo without cables could be found, just calculate what will cost you from TME. Otherwise servo cables are extremely expensive. >8-10euro per meter against ~2-3euro from TME
-Samsung and Panasonic servos are the best you could find for the buck on ebay. Light years away from cheap chinese servo, speaking of possibilities. Not that for simple CNc will make any difference, except that manual is better written.
-There are 2-3 reputable sellers from South Corea and Hong Kong/ skmh218, usedparts-pk, and others /. Avoid Yaskawa servos, some are not accepting the necessary signals so no good for us
-Read manuals and make sure you are buying servo rated for around 3000rpm, that accepts Step Dir signal and even better differential signal. Read manual and make sure if motor is general purpose servo not something special purpose
-Absolute encoder is best, but not a must. Just an added bonus
-Look at pictures carefully and buy stuff that only looks newish or not in bad shape
-Servos need or if not needed is best to be geared down 2-3:1. Why? Because gearing down gives better resolution without artificial microstepping, more power from smaller servos $$$ and at the end of the day you probably dont have a machine that could run with a servo spinning at full speed. My Samsung servos are 3000RPm straight line torque rated but could spin to 6-8k RPM without a problem.


-For your scenario 100w-200W servos geared 2:1 will be OK probably.


-Servos need a good controller as more impulses have to be send to them than normal stepper drive. Do not buy servo until you have made all calculations!. 100khz per axis is minimum, normally 400khz and up, depends on machine, feed desired, etc. My Samsung servos for example dont need so fast controller as they are rated


Example:
My 400w samsung servo could have 2000/2048/2500/10000 P/R etc.(Incremental or Absolute type) encoder. It has the 2048 one. Most of chinese servos when say they have 2048 encoder they mean 2048/4=512 Pulse Per revolution. Not so here. The samsung servo has 2048 Pulse per revolution

So i have geared it 3:2 on a 10mm ball screw. That means when once the ball screw turns 10mm distance is traveled. I wanted my machine to have 20m/min real world working speed. It could easily reach 30 or more as my servos could spin to 6-7k RPM but that's another matter. I calculated all based on 3k rpm.

For 20 000 mm/min the ball screw has to turn 20000/10=2000 times as its geared 3:2 / 30 tooth to 20 tooth HTD 5 15mm pulley / if motor spins 3000rpm then i will achieve on theory that 20 000 mm/min. for 3000rpm to happen the controller has to output 3000x2048=6 146000 pilses per minute/60=102.400pulses per sec hence controller should be at least 100khz per channel.

Do you calculation if you have the absolute controller that is 10000 pulses per revolution, you will need at least 400kz controller/ per axis. Now simply said the thing is that most controllers when say the PPR they mean /4 so that means all is multiplied by 4 , so in reality you need a controller in the Mhz not Khz

so for 1mm my motor will make 1/10 turn of the ball screw. ((3/2)* 2048)/10=307.2 pulses per mm which means my machine has electronic resolution of ~0.003mm ( 1mm/307.2 PPR). Not bad for an all purpose woodworking machine. No microstepping or so. Servo drives also support microstepping and internal gearing.



What i am saying get acquainted well with all that mentioned and you will know more or less what are you doing when buying servos

Clive S
10-07-2017, 08:58 AM
I like the Teknic ClearPath integrated servos and I think their CPM-SDSK-3421S-RLN will do the trick - https://www.teknic.com/model-info/CPM-SDSK-3421S-RLN/


Are these not just closed loop steppers. They spin a about 1000 rpm A bit like the Leadshine closed loop stepper/servo

Agathon
10-07-2017, 10:26 AM
Hi,
here i organised some info. If something not clear, please ask:

If buying new servos:
-Look for the servos to come with cables if not integrated
-www.jmc-driver.com the cheapest servos around that i know of

If buying second hand:
-cables and connectors, at least the connectors. If servo cables are needed TME.eu sells the cheapest quality cable for servos and generally speaking. Some times a great deal servo without cables could be found, just calculate what will cost you from TME. Otherwise servo cables are extremely expensive. >8-10euro per meter against ~2-3euro from TME
-Samsung and Panasonic servos are the best you could find for the buck on ebay. Light years away from cheap chinese servo, speaking of possibilities. Not that for simple CNc will make any difference, except that manual is better written.
-There are 2-3 reputable sellers from South Corea and Hong Kong/ skmh218, usedparts-pk, and others /. Avoid Yaskawa servos, some are not accepting the necessary signals so no good for us
-Read manuals and make sure you are buying servo rated for around 3000rpm, that accepts Step Dir signal and even better differential signal. Read manual and make sure if motor is general purpose servo not something special purpose
-Absolute encoder is best, but not a must. Just an added bonus
-Look at pictures carefully and buy stuff that only looks newish or not in bad shape
-Servos need or if not needed is best to be geared down 2-3:1. Why? Because gearing down gives better resolution without artificial microstepping, more power from smaller servos $$$ and at the end of the day you probably dont have a machine that could run with a servo spinning at full speed. My Samsung servos are 3000RPm straight line torque rated but could spin to 6-8k RPM without a problem.


-For your scenario 100w-200W servos geared 2:1 will be OK probably.


-Servos need a good controller as more impulses have to be send to them than normal stepper drive. Do not buy servo until you have made all calculations!. 100khz per axis is minimum, normally 400khz and up, depends on machine, feed desired, etc. My Samsung servos for example dont need so fast controller as they are rated


Example:
My 400w samsung servo could have 2000/2048/2500/10000 P/R etc.(Incremental or Absolute type) encoder. It has the 2048 one. Most of chinese servos when say they have 2048 encoder they mean 2048/4=512 Pulse Per revolution. Not so here. The samsung servo has 2048 Pulse per revolution

So i have geared it 3:2 on a 10mm ball screw. That means when once the ball screw turns 10mm distance is traveled. I wanted my machine to have 20m/min real world working speed. It could easily reach 30 or more as my servos could spin to 6-7k RPM but that's another matter. I calculated all based on 3k rpm.

For 20 000 mm/min the ball screw has to turn 20000/10=2000 times as its geared 3:2 / 30 tooth to 20 tooth HTD 5 15mm pulley / if motor spins 3000rpm then i will achieve on theory that 20 000 mm/min. for 3000rpm to happen the controller has to output 3000x2048=6 146000 pilses per minute/60=102.400pulses per sec hence controller should be at least 100khz per channel.

Do you calculation if you have the absolute controller that is 10000 pulses per revolution, you will need at least 400kz controller/ per axis. Now simply said the thing is that most controllers when say the PPR they mean /4 so that means all is multiplied by 4 , so in reality you need a controller in the Mhz not Khz

so for 1mm my motor will make 1/10 turn of the ball screw. ((3/2)* 2048)/10=307.2 pulses per mm which means my machine has electronic resolution of ~0.003mm ( 1mm/307.2 PPR). Not bad for an all purpose woodworking machine. No microstepping or so. Servo drives also support microstepping and internal gearing.



What i am saying get acquainted well with all that mentioned and you will know more or less what are you doing when buying servos

Many thanks for such a comprehensive and detailed reply. It gives me a really good starting point.


Are these not just closed loop steppers. They spin a about 1000 rpm A bit like the Leadshine closed loop stepper/servo

According to Teknic they're a true servo. They certainly sound like a servo when running. Teknic go to some length to make the distinction between ClearPath and stepper motors.

Agathon
10-07-2017, 12:45 PM
Apart from the obvious, what's the difference between AC and DC servos?

Agathon
10-07-2017, 12:49 PM
I see a few Panasonic and Samsung servos on eBay. However, I notice that apart from the part numbers sellers don't list any specs. Is there somewhere to check specs? Both the Panasonic and Samsung sites seem to be impenetrable.

Boyan Silyavski
10-07-2017, 01:50 PM
The servos come on certain series. So you have to find the manual for the series.

22165



https://www.google.es/search?q=Samsung+sdj+plus+manual&rlz=1C1CHBF_enES719ES719&oq=Samsung+sdj+plus+manual&aqs=chrome..69i57j0l5.9472j0j7&sourceid=chrome&ie=UTF-8#q=Samsung+servo+drive++manual

Boyan Silyavski
10-07-2017, 01:53 PM
Apart from the obvious, what's the difference between AC and DC servos?

The obvious. The AC servo when 230VAC does not need additional transformer. This is best. Then cheaper servos could be 80VAC then you need to feed them 80VAC. But of course depending on price availability sometimes is worth making that PSU.

Agathon
10-07-2017, 01:58 PM
The obvious. The AC servo when 230VAC does not need additional transformer. This is best. Then cheaper servos could be 80VAC then you need to feed them 80VAC. But of course depending on price availability sometimes is worth making that PSU.

So it's not the characteristic of the motor itself but just the driver? So are all servos dc motors or are some ac?

Boyan Silyavski
10-07-2017, 02:06 PM
So it's not the characteristic of the motor itself but just the driver? So are all servos dc motors or are some ac?

Ahh, the AC does not have brushes. The DC servos with brushes are older motors with older drives that may need Voltage control +-10v, not pulse control. That could make things bad, as this type of controllers are expensive cause their only purpose is to retrofit old machines. Hence thats why i told you to search for drives that support Pulse and Direction

Boyan Silyavski
10-07-2017, 02:11 PM
http://www.ebay.es/itm/CSDJ-02BX2-CSMT-02BB1ANT3-200W-AC-Servo-Motor-Driver-controlUsed-Samsung-W-Cable-/221641710227?hash=item339ae01a93:g:HfcAAOSw0vBUl2g B

Thats what i have / the 400w/ and where i bought it from. And what i would recommend. Just check again for the details in the manual (https://www.google.es/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwjypNrm5P7UAhWOyRoKHZgiBFgQFggpMAE&url=http%3A%2F%2Fwww.cnczone.ru%2Fforums%2Findex.p hp%3Fact%3Dattach%26type%3Dpost%26id%3D8233&usg=AFQjCNFOnah9vdTkFUxGou2_uaU-37-Llw). You will not find anything better for the money.

Agathon
10-07-2017, 02:19 PM
Ahh, the AC does not have brushes. The DC servos with brushes are older motors with older drives that may need Voltage control +-10v, not pulse control. That could make things bad, as this type of controllers are expensive cause their only purpose is to retrofit old machines. Hence thats why i told you to search for drives that support Pulse and Direction

Thanks, sorry for being so dim about this - it's begging to make sense. Also many thanks for the links.

BTW. Apart from power, is there any difference between servo motors used for positioning ie x,y,z axis motors and servos used for spindles?

Boyan Silyavski
10-07-2017, 02:37 PM
Thanks, sorry for being so dim about this - it's begging to make sense. Also many thanks for the links.

BTW. Apart from power, is there any difference between servo motors used for positioning ie x,y,z axis motors and servos used for spindles?

Yes and No. Any servo motor rightly belted could serve for spindle. But then comes the RPM. The servos that are meant for spindles could spin at higher RPM and have slightly different curve. We are talking about typical motor that will be connected to BT30, etc spindle via belt. As Yes, you could gear up any servo motor but then you need bigger more expensive motor.

these are the servo spindle motors. they gto up to 15k rpm https://www.aliexpress.com/store/product/bt30-spindle-servo-motor-driver-3-7kw-CTB-43P7ZGA15-60H5J-BKSC-43P7GH1B/324800_32809932059.html

Agathon
10-07-2017, 02:44 PM
Yes and No. Any servo motor rightly belted could serve for spindle. But then comes the RPM. The servos that are meant for spindles could spin at higher RPM and have slightly different curve. We are talking about typical motor that will be connected to BT30, etc spindle via belt. As Yes, you could gear up any servo motor but then you need bigger more expensive motor.

these are the servo spindle motors. they gto up to 15k rpm https://www.aliexpress.com/store/product/bt30-spindle-servo-motor-driver-3-7kw-CTB-43P7ZGA15-60H5J-BKSC-43P7GH1B/324800_32809932059.html

Thanks again. Not cheap then.

While I'm here. Am I right in thinking that the advantage of an absolute encoder over incremental is that the motor position is known after power-down?

Gary
10-07-2017, 03:33 PM
Yes, but there are different types of absolute. you have single turn and multi-turn, the name is self-explanatory.
Also, Absolute encoders have a much higher resolution than incremental.


Thanks again. Not cheap then.

While I'm here. Am I right in thinking that the advantage of an absolute encoder over incremental is that the motor position is known after power-down?

Agathon
10-07-2017, 03:37 PM
Yes, but there are different types of absolute. you have single turn and multi-turn, the name is self-explanatory.
Also, Absolute encoders have a much higher resolution than incremental.

Thanks. I notice that you have both DC brushless and AC servos on your website - what are the advantages and disadvantages?

Boyan Silyavski
10-07-2017, 03:37 PM
Thanks again. Not cheap then.

Servo controller for me is a must for a metal working machine, a heavy gantry router or a high precision machine for miniature machining, industrial production machine that needs to be fast as possible For all else a stepper will do just fine job.

Agathon
10-07-2017, 03:43 PM
Servo controller for me is a must for a metal working machine, a heavy gantry router or a high precision machine for miniature machining, industrial production machine that needs to be fast as possible For all else a stepper will do just fine job.

What I really meant was that servos for spindles weren't cheap. I'm a great believer in "getting what you pay for". I can live without a servo spindle, but I think I need to invest in servos for the x and y axes of my mill.

Gary
10-07-2017, 03:43 PM
Thanks. I notice that you have both DC brushless and AC servos on your website - what are the advantages and disadvantages?

One take DC and the other takes AC, so the AC servo driver has a power supply built in that is rated to the nominal and peak rated current of the driver.
Also Just because it's a DC servo does not mean its brushed, a DC servo can be brushed or brushless.

Agathon
10-07-2017, 03:46 PM
One take DC and the other takes AC, so the AC servo driver has a power supply built in that is rated to the nominal and peak rated current of the driver.
Also Just because it's a DC servo does not mean its brushed, a DC servo can be brushed or brushless.

OK, that's a very concise reply, but why buy a DC over and AC and vice versa?

Gary
10-07-2017, 03:53 PM
There are a few reasons, but this one normally gives you an indication.
Ok, lets say you have a machine with 8 axis and each axis needs a servo, that is not too large.
you can get 8 AC servo motors and driver and you will be paying more because each driver has its own power supply.
with the DC option, you will have 8 DC servo drivers and a large power supply.
Also DC servo motors are typically low voltage DC, so the current is higher, so typically the motors dont go too big (under a KW)
Personally, i would not even consider a DC servo system, unless you know why you need it. AN ac servo system is typically a better option.


OK, that's a very concise reply, but why buy a DC over and AC and vice versa?

Agathon
10-07-2017, 03:57 PM
There are a few reasons, but this one normally gives you an indication.
Ok, lets say you have a machine with 8 axis and each axis needs a servo, that is not too large.
you can get 8 AC servo motors and driver and you will be paying more because each driver has its own power supply.
with the DC option, you will have 8 DC servo drivers and a large power supply.
Also DC servo motors are typically low voltage DC, so the current is higher, so typically the motors dont go too big (under a KW)
Personally, i would not even consider a DC servo system, unless you know why you need it. AN ac servo system is typically a better option.

Right, so AC servo drivers aren't typically 240vac SP input then and need a step-down transformer?

Gary
10-07-2017, 04:02 PM
No, AC is AC, regardless of the voltage.
Typically single phase goes up to about 1.5KW
For a hobby machine, its unlikely you will need anything that big.
Even a mill like Bridgeport MDI /Interact can use 750W easily.


Right, so AC servo drivers aren't typically 240vac SP input then and need a step-down transformer?

Agathon
10-07-2017, 04:07 PM
No, AC is AC, regardless of the voltage.
Typically single phase goes up to about 1.5KW
For a hobby machine, its unlikely you will need anything that big.
Even a mill like Bridgeport MDI /Interact can use 750W easily.

OK, so just to be clear. A 400W AC servo motor would typically be coupled to a driver powered by AC at a voltage less than 240v? So is the power supply simply a step-down transformer or is there more to it?

Gary
10-07-2017, 04:16 PM
it totally depends on what the bus voltage of the motor is.
To make it easy, if and when you buy them get a matched pair with cables, or talk directly to the company and get advise on what they suggest for the application.

Agathon
10-07-2017, 04:25 PM
it totally depends on what the bus voltage of the motor is.
To make it easy, if and when you buy them get a matched pair with cables, or talk directly to the company and get advise on what they suggest for the application.

Thanks - I'll email you in the next few days.

Boyan Silyavski
10-07-2017, 04:26 PM
Personally, i would not even consider a DC servo system, unless you know why you need it. AN ac servo system is typically a better option.
Me too. And honestly valuing my time i will not consider separate PSU but a pure plug and play system.

Ger21
10-07-2017, 10:31 PM
OK, so just to be clear. A 400W AC servo motor would typically be coupled to a driver powered by AC at a voltage less than 240v?

No, most of the currently available 400w AC servos are 220-240V

Agathon
10-07-2017, 11:56 PM
No, most of the currently available 400w AC servos are 220-240V

Nice.

Agathon
15-07-2017, 01:08 PM
What do you think of this: http://www.ebay.co.uk/itm/Samsung-RS-OEMax-400W-AC-Servo-Motor-CMST-04BB1ANT3-3B492-/282340382590

Might it be suitable for my app or am I barking up the wrong tree?

Agathon
17-07-2017, 02:15 PM
Is it important that the servo driver and motor are from the same manufacturer? Or is just that the driver and motor must match electrically speaking?

Ger21
17-07-2017, 02:35 PM
The most important is that the encoder connections on motor match what the drive requires.
Some encoders/drives use 12 or more wires, some use as few as 5 or 6.
Imo, unless you really know what you're doing, it's best to but a matched set from the same manufacturer.

Not sure if they are available over there, but here inthe US, and Canada, DMM are the best bang for the buck.

Agathon
17-07-2017, 02:41 PM
The most important is that the encoder connections on motor match what the drive requires.
Some encoders/drives use 12 or more wires, some use as few as 5 or 6.
Imo, unless you really know what you're doing, it's best to but a matched set from the same manufacturer.

Not sure if they are available over there, but here inthe US, and Canada, DMM are the best bang for the buck.

Many thanks Gerry. Those DMM servos are very good VFM.

Boyan Silyavski
17-07-2017, 03:42 PM
The Samsung servos need a Samsung drive. Or better said, you could not hook other servo motor to a brand drive. As it auto detects motors and will give " Faulty" all of the time. Samsung motors have 9 wires to encoder, some 11. The one on link is with 9 wires.

The only way you could make a similar motor work is Universal servo drive like Granite Devices (https://granitedevices.com/).

And yes, that motors are good price and good ones, but you can check the Samsung PDF manual link i send you earlier and see that for yourself. But remember what i told you about the servo cables. Dont make decisions without knowing what will cost you when you include them. The good thing is these motors are in Europe. You could buy the drives for around 130 each, used.

DMM are out of question in Europe. Going that way is better to buy Chinese drives or the second hand Samsung. I have pondered over that many times last years and every time money and price prevails.

Agathon
17-07-2017, 04:29 PM
Thanks for the reply.

I've taken a punt on these: http://www.ebay.co.uk/itm/322584699618

I spoke to the young lad whose selling them and it seems his grandfather worked in the motion control field. They may not work of course, but not much lost if they are US.

Will keep an eye out for motors to match.

Boyan Silyavski
17-07-2017, 04:56 PM
I think you misunderstood what i said. Drive and motor combo from different manufacturers will NOT work!!!

You need a drive that lets you program the motor parameters, not a drive that lets you choose from certain motors!!! Check that in manual.

Agathon
17-07-2017, 05:03 PM
I think you misunderstood what i said. Drive and motor combo from different manufacturers will NOT work!!!

You need a drive that lets you program the motor parameters, not a drive that lets you choose from certain motors!!! Check that in manual.

Thanks for the clarification. I'll be looking for used Omron or Yaskawa motors for the drives I've just bought (it appears that they had a joint venture).

It does seem that the issue of whether different manufacturers motors can be driven from different drives is not straightforward: http://www.cnczone.com/forums/servo-motors-drives/126010-matching-ac-servo-driver.html

However, I take your point. At 90 for two drives I'm willing to have a play and see what happens.

You mentioned cables in a previous post. Is it impossible to make up cables given the correct plugs and sockets?

Agathon
17-07-2017, 05:12 PM
According to the specs this is the correct motor for the drivers I just bought - http://www.ebay.co.uk/itm/OMRON-R88M-AC-SERVOMOTOR-REDUCED-TO-SELL-/182634177958

Agathon
17-07-2017, 06:03 PM
Just out of interest, via a socket screw axial to the ballscrew, I used a precision torque screw-driver (usually used for very carefully setting the torque on small screws) to see how much torque was required to move the table. As might be expected the initial torque required to overcome the stiction was higher that what was required to keep it moving. However the maximum torque required was surprisingly low - 0.5 Nm. I might just pop a 16mm slot-drill in a collet and see how much torque is required to make it cut steel...

Agathon
17-07-2017, 06:36 PM
Having thought about this for a few mins, I am now a little unsure that a 200W servo will be powerful enough for my table. The Omron R88M 200w motors produce 0.637 Nm continuous torque with a peak of 2.2 Nm.

I think I noted in one of my first posts on this forum about stepper replacement that Fehlmann now fit Omron 400W servos to the P21 which is a similar machine to mine (but with a slightly larger table) - I'd forgotten about this until doing some searches earlier on.

I suppose that if I do as you suggest Boyan and fit the servos with a 2:1 reduction a 200W Omron servo might be adequate. Being more optimistic, a reduction of 3:1 would produce the best part of 2Nm continuous torque - which will probably do the job.

Agathon
20-07-2017, 12:53 PM
http://www.ebay.es/itm/CSDJ-02BX2-CSMT-02BB1ANT3-200W-AC-Servo-Motor-Driver-controlUsed-Samsung-W-Cable-/221641710227?hash=item339ae01a93:g:HfcAAOSw0vBUl2g B

Thats what i have / the 400w/ and where i bought it from. And what i would recommend. Just check again for the details in the manual (https://www.google.es/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwjypNrm5P7UAhWOyRoKHZgiBFgQFggpMAE&url=http%3A%2F%2Fwww.cnczone.ru%2Fforums%2Findex.p hp%3Fact%3Dattach%26type%3Dpost%26id%3D8233&usg=AFQjCNFOnah9vdTkFUxGou2_uaU-37-Llw). You will not find anything better for the money.

Just noticed that your Samsung drivers appear to be the same as the Omron that I have. Obviously all made by Yaskawa and branded to suit.

Boyan Silyavski
20-07-2017, 08:20 PM
Just noticed that your Samsung drivers appear to be the same as the Omron that I have. Obviously all made by Yaskawa and branded to suit.

By Iskawa not, by Parker i believe. But yes...

Agathon
20-07-2017, 09:07 PM
By Iskawa not, by Parker i believe. But yes...

I noticed on the RS (Rockwell Samsung) website that they started making Yaskawa inverters under license in 1989 - presumably the servo drives followed on.

Robin Hewitt
22-07-2017, 11:21 AM
This is not going well. A few people have bits and pieces but has anyone done the full X, Y, Z Monty? Even Gary seems to avoid selling servo motors with driver and cables in one package and most everything is out of stock. There seem to be steppers with encoders masquerading as affordable servo kits just to trap doddery old gits with more money than sense like me. Most of it seems to be a few big name motors and drivers being passed around on e-bay but never actually used.
Or have I completely misunderstood?

Boyan Silyavski
22-07-2017, 11:38 AM
This is not going well. A few people have bits and pieces but has anyone done the full X, Y, Z Monty? Even Gary seems to avoid selling servo motors with driver and cables in one package and most everything is out of stock. There seem to be steppers with encoders masquerading as affordable servo kits just to trap doddery old gits with more money than sense like me. Most of it seems to be a few big name motors and drivers being passed around on e-bay but never actually used.
Or have I completely misunderstood?

What do you need exactly from the aforementioned options? The cheapest JMC servos plus drives / around 180$ each kit where you need 80V transfrormer or PSU, you get cables with them/ , The 220V AC servos second hand /Panasonic, Samsung where you buy them for around 250euro the kit with cables/ or new 230v AC Servos from BST automation/ where you buy the kit with cables again/ .

I would consider only these 3 options and nothing else. If you need help choosing from them then let's discuss it. All other options are no good for my liking, price wise, complexity, support and so on

Agathon
22-07-2017, 12:41 PM
What do you need exactly from the aforementioned options? The cheapest JMC servos plus drives / around 180$ each kit where you need 80V transfrormer or PSU, you get cables with them/ , The 220V AC servos second hand /Panasonic, Samsung where you buy them for around 250euro the kit with cables/ or new 230v AC Servos from BST automation/ where you buy the kit with cables again/ .

I would consider only these 3 options and nothing else. If you need help choosing from them then let's discuss it. All other options are no good for my liking, price wise, complexity, support and so on

Just to chuck in my two penn'orth, I'm not so sure that the cables are so much of a problem. Having done a bit of research on my Yaskawa/Omron drives the plugs are nothing special and available from RS and the like. The manuals give all the wiring information - a bit of suitable cable, a soldering iron and you're away.

Agathon
22-07-2017, 12:45 PM
This is not going well. A few people have bits and pieces but has anyone done the full X, Y, Z Monty? Even Gary seems to avoid selling servo motors with driver and cables in one package and most everything is out of stock. There seem to be steppers with encoders masquerading as affordable servo kits just to trap doddery old gits with more money than sense like me. Most of it seems to be a few big name motors and drivers being passed around on e-bay but never actually used.
Or have I completely misunderstood?


Are you thinking about servos for your mill/drill Robin? If so, I'd counsel hanging on to your cash and buying a Denford Triac or similar then going from there. From what you said about the quill you'd be throwing money at a machine that's never going to quite hit the mark despite all of the excellent work you've done on it:apologetic:

Boyan Silyavski
22-07-2017, 01:02 PM
Just to chuck in my two penn'orth, I'm not so sure that the cables are so much of a problem. Having done a bit of research on my Yaskawa/Omron drives the plugs are nothing special and available from RS and the like. The manuals give all the wiring information - a bit of suitable cable, a soldering iron and you're away.

I agree, though depending on your skill it takes time to sort things out and solder. it took me a lot of time to solder my cables .

Agathon
22-07-2017, 01:22 PM
I agree, though depending on your skill it takes time to sort things out and solder. it took me a lot of time to solder my cables .

Good point, well made. I'd sooner buy a proper factory made cable any day, but they are so expensive. I think if a bargain driver/motor combo turns up with short cables that shouldn't put one off.

Boyan Silyavski
22-07-2017, 01:30 PM
Good point, well made. I'd sooner buy a proper factory made cable any day, but they are so expensive. I think if a bargain driver/motor combo turns up with short cables that shouldn't put one off.

Thats what i did , my beast did not like even 6m cables so i had to make 10m some of them using the TME cables, which honestly for 2euros per meter are incredible deal. They have all possible connectors too

Agathon
22-07-2017, 01:38 PM
Thats what i did , my beast did not like even 6m cables so i had to make 10m some of them using the TME cables, which honestly for 2euros per meter are incredible deal. They have all possible connectors too

I'd forgotten that you mentioned tme.eu. At 2 Euro a metre they're a no-brainer.

Robin Hewitt
22-07-2017, 04:21 PM
If I read it right, Gary would do me a set of three 400W motors and drivers for 1260 + tax. That doesn't sound too awful but I know nothing about servo motors. I'm not shopping, just cogitating.

m_c
22-07-2017, 11:54 PM
The time component of making cables is very often overlooked.
For a hobbyist it's not normally a problem spending a few hours finding the connectors/cable/wiring diagram and physically making the cables, but when time is money, pre-made cables are cheap.

All my servos have been bought from Gary/Zapp. Certainly not the cheapest option, but he's not just a box shifter, and should you need any advise, he's only an email/phone call away.

One thing to bear in mind, is servos should be inertia matched to their load for best performance. Too big or too small a servo for any given load will not give a good tune. The spindle on my mill demonstrates that perfectly. It's a 110 frame medium inertia servo, and the best positional accuracy I can get before things go unstable is about 200 encoder counts, as it's not got enough of a load to help stabilise it. My lathe on the other hand, which has small inertia 60/80 frame servos, holds sub 20 counts without any problem, as the servo load is a good match to provide stability.

Ger21
23-07-2017, 03:35 AM
I plan on making my own servo cables, mainly due to the issue of the available pre-made cable lengths.

Most come in 3, 5, or 10m lengths. When you get to just over 5m, you can end up with a lot of unused cable length. But is you're needs are close to the pre-made lengths, you won't save much at all making your own.

Robin Hewitt
23-07-2017, 09:15 AM
servos should be inertia matched to their load for best performance... the best positional accuracy I can get before things go unstable is about 200 encoder counts

To a lay idiot like me, you seem to be saying that there is some complicated matching that needs to be done on each axis before purchasing a servo system to avoid it being a huge disappointment. My steppers suddenly start to seem like God's gift to His chosen few. Am I misunderstanding?

Boyan Silyavski
23-07-2017, 09:41 AM
To a lay idiot like me, you seem to be saying that there is some complicated matching that needs to be done on each axis before purchasing a servo system to avoid it being a huge disappointment. My steppers suddenly start to seem like God's gift to His chosen few. Am I misunderstanding?

Just a bit maybe. I went from steppers to servos and dont think i will ever look back. The other day i had here a vinyl plotter, was looking to buy. What stopped me was it was not servos but steppers, and somehow the noise put me off.

I got help from knowledgeable members of forum at the time which did the calcs for me what i need for my machine. So 100% here people will help you. Now i know more and can do that myself but surely will ask for advice if i am not sure. That's what the forum is for.

Anyway, as i have concluded many times, servos are a must for a metal working machine, production machine and hi resolution micro mill. All else could be done from steppers



PS. what put me off for the plotter was not only the noise but the ability of the plotter to track correctly longer lengths of vynil, if it was servo

m_c
23-07-2017, 11:45 AM
To a lay idiot like me, you seem to be saying that there is some complicated matching that needs to be done on each axis before purchasing a servo system to avoid it being a huge disappointment. My steppers suddenly start to seem like God's gift to His chosen few. Am I misunderstanding?

Just apply some common sense. Don't go bolting a high inertia motor to a X1, and don't try using a small inertia servo on a quarter ton table. Use something a reasonable size.

Given what Agathon has posted links to, I would of though 400 or 750 watt servos would work nicely.
The smaller machine you've posted a photo of, I would of thought 200 or 400 watt.
To give some idea, IIRC Denford Triacs with servos, came with 200W servos, however they'd be conservatively sized due to being aimed at education. They perform well enough, however 400W would give a good boost to performance and work just as well.

Agathon
23-07-2017, 12:20 PM
Just apply some common sense. Don't go bolting a high inertia motor to a X1, and don't try using a small inertia servo on a quarter ton table. Use something a reasonable size.

Given what Agathon has posted links to, I would of though 400 or 750 watt servos would work nicely.
The smaller machine you've posted a photo of, I would of thought 200 or 400 watt.
To give some idea, IIRC Denford Triacs with servos, came with 200W servos, however they'd be conservatively sized due to being aimed at education. They perform well enough, however 400W would give a good boost to performance and work just as well.

Yes, I think the 200W Omron drivers I've just bought will be too small, but will try them geared at 3:1. They were very cheap, so I'm not worried if I have to put them back on the market. I shall be keeping an eye out for 400W which is what they currently fit to the very slightly larger version of my machine.

Do you know what the ratio was on the Triac servos?

Boyan Silyavski
23-07-2017, 12:36 PM
Yes, I think the 200W Omron drivers I've just bought will be too small, but will try them geared at 3:1. They were very cheap, so I'm not worried if I have to put them back on the market. I shall be keeping an eye out for 400W which is what they currently fit to the very slightly larger version of my machine.

Do you know what the ratio was on the Triac servos?



I am moving a 200kg gantry with 2x400w servos / via rotating nuts which have smaller inertia than spinning a screw / 3000 mms2 acceleration and judjing from the servo tuning and initial calculations, its the perfect thing. Exact sizing. geared 1.5, not 3. So with 200W servos geared 1.5 you could do a lot of things. No need to gear them up so if not needed. As gearing up will increase the spinning mass so maybe you will not benefit as you think ... 20/30 tooth is an ideal relation and pulley size. For lighter load you could go down as 16t but mind the servo shaft size. I would say for 200W servos, 18t pulley will be right, start thinking from there...

I am not sure also how Chinese servos stand up to brand servos. If 400w is 400w really? What i know is that the brand servos stand up to what they say. Thats why i preferred 230V AC servos , for all that benefits. If i buy a chinese servo i will always Up it one level of power so just to be sure. 750W isntead of 400 :tan:

Robin Hewitt
23-07-2017, 12:57 PM
PS. what put me off for the plotter was not only the noise but the ability of the plotter to track correctly longer lengths of vynil, if it was servo

I think it was Calcomp had the patent on using grit for the driving rollers and everyone else looked jealous. I used to repair these things, a long time ago :culpability:

m_c
23-07-2017, 05:06 PM
Do you know what the ratio was on the Triac servos?
I've only got the parts list for the stepper version, and it uses 12:30. Chaz has a servo version, but I don't think there would be much room to go for a higher ratio.

Agathon
23-07-2017, 11:35 PM
What size timing pulleys would you suggest for 200 or 400 watt servos? I was thinking that 5M 9mm wide belt should be about right. Centres should be around 100mm.

Ger21
24-07-2017, 12:01 AM
I'd say 15mm belt width minimum.

m_c
24-07-2017, 04:27 PM
If you download the Gates DF software, it will generate suitable drive options.

Agathon
30-07-2017, 12:37 AM
Just in case you helpful fellows haven't seen my new thread on trying to connect up the drivers to the BOB - here it is: http://www.mycncuk.com/threads/11159-Help-connecting-servos-to-breakout-board-Mach3

lp_felix
26-08-2017, 01:18 PM
Hi guys, I'm going to build a machine to drill and tapping one part, I'm thinking use a servo for tapping and a regular spindle for drilling. Using a regular servo I can do rigid M3 tapping on 2mm aluminium sheet? Have anyone experience with something similar? Tks

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Clive S
26-08-2017, 02:25 PM
Hi guys, I'm going to build a machine to drill and tapping one part, I'm thinking use a servo for tapping and a regular spindle for drilling. Using a regular servo I can do rigid M3 tapping on 2mm aluminium sheet? Have anyone experience with something similar? Tks

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To do rigid tapping you will need a quadrature encoder on the servo and some thing like Linuxcnc to control it.

Here is a link in Portugal where you can buy the Mesa cards 6i25 with 7i77 bob will do it.

Are you think of having the spindle and servo on the same gantry?

Ger21
26-08-2017, 03:07 PM
You can also do rigid tapping with UCCNC, and with Mach3/4 with the right motion controller.

lp_felix
26-08-2017, 03:12 PM
To do rigid tapping you will need a quadrature encoder on the servo and some thing like Linuxcnc to control it.

Here is a link in Portugal where you can buy the Mesa cards 6i25 with 7i77 bob will do it.

Are you think of having the spindle and servo on the same gantry?Yes, spindle and servo on same gantry.. Ok, I have a lot of questions but i will study quadrature encoder and servo first, and do stupid questions later.. Thank you for the help. [emoji1][emoji106]

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lp_felix
26-08-2017, 03:34 PM
You can also do rigid tapping with UCCNC, and with Mach3/4 with the right motion controller.

Hi Ger21, in fact I planing use uccnc. I have a spare Uc300 5lpt (from other unfinished project) I will read the manual.
Thanks for the tip. [emoji106] [emoji1]

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Robin Hewitt
27-08-2017, 12:29 PM
If it is always the same tap, no pitch change, why not gear vertical displacement to rotation? Drive it with anything you like.

magicniner
28-08-2017, 12:25 AM
Just in case you helpful fellows haven't seen my new thread on trying to connect up the drivers to the BOB - here it is: http://www.mycncuk.com/threads/11159-Help-connecting-servos-to-breakout-board-Mach3

I suggest you take the advice of the guy who didn't know what a harmonic drive was and couldn't be arsed to look it up before being clever about being wrong :D

Gary
28-08-2017, 08:37 AM
I know what a harmonic drive gearbox is, i was just incorrect on the technical term used to describe them. I was selling them 15 years ago, but made by spinea.




I suggest you take the advice of the guy who didn't know what a harmonic drive was and couldn't be arsed to look it up before being clever about being wrong :D