Electronic Lead Screw Project

[Tony Pratt 1Participant @tonypratt1]

Posted by John Haine on 05/12/2019 13:25:48:

Tony, when you say 2.5k spindle speed is that stepper RPM? That's a step rate of at least 200 x 2500/60 = 8 khz which is pretty fast for a stepper I think! Torque and therefore power drop off quite quickly with speed. I assume you mean Type 23 stepper? On my CNC Myford the leadscrew motor is a size 38.

No the 2.5k is the lathe spindle speed so the stepper is running a lot slower, I am using a Nema 24 stepper motor which is what Clough42 used.

Tony

[LoftyParticipant @lofty83899]

Evening all, I successfuly tested my setup today.

Nema 34 closed loop stepper and driver on a Warco 280VF.

just got to figure out an enclure for the key pad a micro board, may put in the head where the existing taco is located.

Testing

[LimpetParticipant @limpet]

Well I'm committed now, ordered the Texas board and led key pad today. Tomorrow I'm hoping to find the encodes I squirreled away a couple years ago and see what they are. I'm still undecided whether to use the stepper motor or servo motor and what size for am ML7, is a nema 24 big enough?

Lionel

[Tony Pratt 1Participant @tonypratt1]

Based on my Warco WM 290V lathe set up I'm sure a Nema 24 will be plenty big enough for an ML7.

Tony

[Roger ClarkParticipant @rogerclark]

Yes but what rating? Voltage, Newton's etc, it all has a bearing on suitability

[blowlampParticipant @blowlamp]

Posted by Lofty on 05/12/2019 18:00:15:

Evening all, I successfuly tested my setup today.

Nema 34 closed loop stepper and driver on a Warco 280VF.

just got to figure out an enclure for the key pad a micro board, may put in the head where the existing taco is located.

Testing

Plus 1 for the closed loop setup. Definitely the way to go for this kind of application where losing steps will spoil the thread..

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Lofty on 05/12/2019 18:00:15:

Evening all, I successfuly tested my setup today.

Nema 34 closed loop stepper and driver on a Warco 280VF.

just got to figure out an enclure for the key pad a micro board, may put in the head where the existing taco is located.

Testing

.

Forgive me please, if I am being dim

… I can’t see any details of the stepper but I do see a hybrid servo driver

Could you please detail what you are actually using.

Many thanks

MichaelG.

[blowlampParticipant @blowlamp]

Posted by Michael Gilligan on 06/12/2019 13:36:44:

Posted by Lofty on 05/12/2019 18:00:15:

Evening all, I successfuly tested my setup today.

Nema 34 closed loop stepper and driver on a Warco 280VF.

just got to figure out an enclure for the key pad a micro board, may put in the head where the existing taco is located.

Testing

.

Forgive me please, if I am being dim

… I can’t see any details of the stepper but I do see a hybrid servo driver

Could you please detail what you are actually using.

Many thanks

MichaelG.

It's probably something like this, although its holding torque may be different.

Still a stepper system, but one with a local feedback loop.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by blowlamp on 06/12/2019 13:52:21:

.

It's probably something like this, although its holding torque may be different.

Still a stepper system, but one with a local feedback loop.

.

Thanks for that … I was blissfully unaware of ‘servo driver’ being used in the context of stepper motors.

MichaelG.

[ZanParticipant @zan]

 

Nema 23 and 24 describes only the frame size and has nothing to do with its holding torque . some 23’s have 4.5 Nm while some 24 have only 1.65nm. So get the full details!

23 has a 56 dia flange, 24 has a 60

 

 Edit….. Another point is that if you use a step down pulley  say 2:1 to increase the torque it’s not that simple.  As the speed of a stepper increases, the fall off in torque is very dramatic, so you gain with the gear ratio, but loose on the motor torque itself! 

Edit 2   Just checked on the jeffree blog mentioned earlier, he used only a 1.8 mm type 23.   With a 40 v drive. I will go for something a little more powerful, a 3 or 4, as rthere is little price difference.

 

Edited By Zan on 06/12/2019 16:08:24

Edited By Zan on 06/12/2019 16:16:31

[Tony Pratt 1Participant @tonypratt1]

Posted by Rockingdodge on 06/12/2019 10:19:45:

Yes but what rating? Voltage, Newton's etc, it all has a bearing on suitability

I'm not an electronics expert [my son is] but the motor I used was meant to give 4 Nm holding torque.

Tony

[ZanParticipant @zan]

Tony.

Jeffree talks about changing the voltage which gave a lot more power. What are you running at. And what power does your psu put out?

Edited By Zan on 06/12/2019 16:44:31

[Tony Pratt 1Participant @tonypratt1]

Posted by Zan on 06/12/2019 16:44:07:

Tony.

Jeffree talks about changing the voltage which gave a lot more power. What are you running at. And what power does your psu put out?

Edited By Zan on 06/12/2019 16:44:31

Hi Zan,

I will have to ask my son who I am seeing on Sunday, as I really don't want to give you guys false info.

Tony

[Phil GrantParticipant @philgrant54580]

Usually the stepper driver will have an upper voltage which could be upto 40 volts and it provides the current to the stepper motor (set with jumpers).

I'm using a 24v supply in my setup and it drives the lead screw OK but I've not tried threading yet.

[LimpetParticipant @limpet]

I'm just wondering but does anyone know if you can attach another encoder to a normal stepper and where would it plug in, as I have a few encodes and several types of stepper,us t trying to save a few penniesj

[ZanParticipant @zan]

Are you trying to make it a servo type to get a closed loop system? Clough42 shows this, but looking at the eBay stepper listings, the servo steppers seem to come with a blue rather than black driver. I don’t know where any servo adjustment for the closed loop takes place but I think it’s in the driver which monitors the pulse out to moratorium then compares it to the sensor and adjusts the output.

so I think it’s a different system altogether ant I think that’s a no no, but perhaps somebody has full info

[LimpetParticipant @limpet]

Thanks Zan I remember now that Clough42 plugged the encoder into the driver so it looks like I will be getting a servo motor and driver. I might try it with just a stepper to check what torque motor I need as I have some. I'm still at the thinking/waiting stage until I get some parts arrive, i also thinking of adding a magnetic clutch in the lead screw drive chain so i can still use the handle on the end without worrying about induced voltages generated by the motor, as i said still at the thing stage

Lionel

[blowlampParticipant @blowlamp]

The closed loop steppers are a direct replacement or substitute for conventional steppers. There's no reason that I can think of why a closed loop stepper/driver couldn't be used in this project.

The closed loop only exists between the motor and its driver – there's no need for any additional wiring back to the ELS itself.

Martin.

[ZanParticipant @zan]

Great blowlamp exactly what I thought then. Only prob is that the closed servo system is a lot more expensive, eBay seems to have them at abt £90 as opposed to abt £30 fir open loop

[Dennis RParticipant @dennisr]

Came across this example of an all in one package for a Nema 34 with driver and power supply, do you think this is a good deal and would be OK for an ML7?

Dennis

https://www.ebay.co.uk/itm/8-5Nm-NEMA34-Stepper-Motor-Driver-Power-Supply-Closed-Loop-8-5N-m-Hybrid-Drive/223770601237?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D61046%26meid%3D273350ecaba14a628828b44ff26609cb%26pid%3D100005%26rk%3D1%26rkt%3D12%26sd%3D283094369235%26itm%3D223770601237%26pmt%3D1%26noa%3D0%26pg%3D2047675&_trksid=p2047675.c100005.m1851

LINK

Edited By Dennis R on 06/12/2019 23:07:34

[ZanParticipant @zan]

That’s massive! Would power an els on a 12” lathe!

[Phil GrantParticipant @philgrant54580]

I bought my kit (just a stepper motor and driver) from Stepperonline, they were quite cheap and deliver from different countries and they have some offer codes at the moment (I have no affiliation with them)

LINK

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Dennis R on 06/12/2019 23:04:29:

Came across this example of an all in one package for a Nema 34 with driver and power supply, do you think this is a good deal and would be OK for an ML7?

Dennis

https://www.ebay.co.uk/itm/8-5Nm-NEMA34-Stepper-Motor-Driver-Power-Supply-Closed-Loop-8-5N-m-Hybrid-Drive/223770601237?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D61046%26meid%3D273350ecaba14a628828b44ff26609cb%26pid%3D100005%26rk%3D1%26rkt%3D12%26sd%3D283094369235%26itm%3D223770601237%26pmt%3D1%26noa%3D0%26pg%3D2047675&_trksid=p2047675.c100005.m1851

LINK

Edited By Dennis R on 06/12/2019 23:07:34

.

This is of no consequence, Dennis … but you might like to know

Everything from the question mark onwards, in that long ebay address is superfluous

it’s tracking information, to tell ebay how you reached the page.

MichaelG.

.

Try: https://www.ebay.co.uk/itm/8-5Nm-NEMA34-Stepper-Motor-Driver-Power-Supply-Closed-Loop-8-5N-m-Hybrid-Drive/223770601237

 

Edited By Michael Gilligan on 07/12/2019 08:34:30

[Phil GrantParticipant @philgrant54580]

I have a question about the type of stepper motor to use for this application, why is the servo option considered to be better?

My understanding is that a servo with feedback is Ideal where positional accuracy is required, say a cnc axis control.

This application requires synchronisation between the spindle and the leadscrew if steps are missed due to external factors then the synchronisation is lost and adding steps on will not recover that synchronisation between the spindle and leadscrew.

I would think spending extra on a more powerful stepper motor would make more sense leading to no missed steps in the first place.

Or have I missed something?

[ZanParticipant @zan]

Iv been mulling this over as well. I don’t know how many steps would actually be lost, but here’s my calcs

1 turn of the 8 tpi leadscrew takes 200 steps x 8 micro steps = 1600 per rev

Lost motion per lost step …… cutting an 8 tpi thread, so 1 turn of  Leadscrew gives saddle move of

0.125” / 1600= 0.000078” Not very much!

So 10 lost steps = 0.00078”. Still very little.

as most threads I cut are at 24tpi+ this is reduced by 1/3 to 0.000026” and 0.00026”

can a humble myford work to these limite? Are my tools ground accurately enough? What effect on the thread does my chaser present? How accurate is my leadscrew?

conclusion, servo ain’t worth the extra cost

 

Edited By Zan on 07/12/2019 10:30:08

Edited By Zan on 07/12/2019 10:32:12

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