ELS for BOXFORD AUD

[Speedy Builder5Participant @speedybuilder5]

That’s OK Jason, I can wind the saddle into the chuck without an ELS !!  Its a bit like putting a saw feed on when turning, and crossing the workshop to pick up some other tool and getting distracted.

I am more certain that I will go ahead with the Electronicleadscrew.eu and incorporate the limit switches – still gives the opportunity of grunching something up.

Bob

[Martin ConnellyParticipant @martinconnelly55370]

I’ve had a timing belt stall and strip teeth on a belt sander when pressing a large area down onto the belt a bit too hard with a fresh, coarse belt surface. So much as Jason suggests it can act as a shearing failsafe when overloaded. On a lathe I would prefer something that stops the tool being driven into the path of the chuck jaws in the first place though. Achievable with a CNC setup that has inputs for limit switches (or soft limits) just make it adjustable to suit different chucks or collets. I don’t know if any, some or all ELS systems have such inputs as supplied.

Martin C

[Speedy Builder5Participant @speedybuilder5]

I am having trouble with my Electronicleadscrew.eu in that the Nema23 stalls under certain conditions.

Typical  840rpm 20tpi – Leadscrew stalls, but dropping down to 560rpm its OK.  The supplier has suggested that the problem lies with the stepper motor size,  but I use the same setup on my power feed to the horizontal mill with a heavier table/load etc without problem. (Warco Economy mill)

Further tests show that for an 8tpi thread, I have to drop speed to 270rpm.

I am wondering if my power supply is too small  36volt 5.0 amp, and that the Nema23 is set to 4.9amp peak 3.5 RMS current. (Max is 5.6/4.0).

Welcome your thoughts on this.

Bob

[John HinkleyParticipant @johnhinkley26699]

Bob,

It would help us to give some advice if you could supply more details about your stepper motor. For example, the holding torque, whether it’s of the closed loop encoder type, reduction gearing to leadscrew, etc.  The NEMA 23 is just the frame size of the motor.  In the example that I linked to earlier, the power supply was 48V at near 5A, not the 36V that you quote.  I wonder if the stepper motor that you have is up to the job? Or the stepper/driver combination are properly matched.  I certainly never had any hint of stalling on either of my ELS installations.

John

 

[Tony Pratt 1Participant @tonypratt1]

Bob, yes more details are required but I do know the stepper motor [NEMA 23 frame] fitted to my Warco 290V ELS does miss steps when pushed hard, I can’t comment off the top of my head reference the current/amps.

It works ok when I use the lathe gearing to give the stepper a 2:1 mechanical advantage so I haven’t really delved into the deeper issues, it’s on my list of things to do.

Tony

PS A quick look at John’s ELS still photo shows a 2:1 drive advantage?

[old martParticipant @oldmart]

Sounds like a great modification for people who cut imperial and metric threads frequently, not to mention the carriage feed rate. Toothed belts have excellent repeatability without the backlash common with gears.

[Speedy Builder5Participant @speedybuilder5]

This is what we have got:-

Headstock to encoder is 60T : 60T  ie 1:1

Leadscrew is 20T : 40T  ie: 2:1  (stepper is the smaller pulley)

Stepper control and motor matched and sold by Stepper On-Line

The stepper motor can be stalled with the belt off and no connection to leadscrew – the system supplier ensures me that it can’t be their system not keeping pace with the encoder.

The stepper motor Nema 23 4.2 amp 3.0 Nm(425 oz in)

The Electronic leadscrew box is set with the correct parameters ie: gear ratios, stepper count etc and the stepper controller matched to them. My only choice is the power output Dip Switches  123 . initially set to off/off/on, now set to off/on/on. (4.9amp peak 3.5 amp Rms)

My only reservation is the power supply which is 36 volt 5 amp.(amazon ref LED 36V 5A – 10A 180W-360W).  It seems that this is intended for LED lighting, cars and public lighting.  Could this be an area of concern? I thought 5 amps was 5 amps But !!!!!

Bob

[John HaineParticipant @johnhaine32865]

Don’t use LED PSUs for general electronics! They are designed down to a price and have poor regulation.  You can get very good switched-mode PSUs from many vendors at reasonable prices.  Here’s one from a CNC supplier.

https://www.cnc4you.co.uk/Breakout-Board-and-PSU/400W-PSU-36Volt-11Amp

By the way, the actual current taken from the supply with a modern stepper driver is usually well below the actual coil current because the driver is in effect a switched-mode power supply.

[John Haine]

On John Haine Said:

Don’t use LED PSUs for general electronics! They are designed down to a price and have poor regulation.  You can get very good switched-mode PSUs from many vendors at reasonable prices.  Here’s one from a CNC supplier.

https://www.cnc4you.co.uk/Breakout-Board-and-PSU/400W-PSU-36Volt-11Amp

Would 48 volts be ‘better’/more powerful?

Tony

[Stuart Smith 5Participant @stuartsmith5]

Bob

Can you post a photo of your power supply?

I have fitted a stepper as a power feed to my milling machine and get what sounds like the same issue if I try to run at high speed. I am using a 48v power supply.

If I start it slower and ramp up the speed it is ok.

My conclusion is that my stepper cannot provide enough torque. I could get a bigger one, but for my application I have just programmed the Arduino I use to provide the pulses to start slower and then speed up.

I don’t suppose that is an option for your application so you will probably need a higher torque motor  and higher voltage & current power supply.

Or it is possible that a 48v power supply would work using the same motor.

Stuart

 

[Stuart Smith 5Participant @stuartsmith5]

This on cnc zone is a discussion on power supply sizing and one of the replies gives more details on why the voltage affects the torque that the stepper can provide at high speed.

https://www.cnczone.com/forums/stepper-motors-drives/376764-stepper-motor-power-supply-option.html

Stuart

[Speedy Builder5Participant @speedybuilder5]

This is the PSU I have (amazon ref LED DC36V 5A – 10A 180W – 360W)  Don’t be confused by 5A – 10A. That is just 2 different PSUs one is 5amp, the other (surprisingly) 10Amp.

[John HaineParticipant @johnhaine32865]

Higher voltage is better provided it’s within the voltage rating of the drive – it will also reduce the actual supply current for a given coil current.  It is very common for steppers to stall if you try to accelerate them too quickly, and driving software should do this automatically.  If using an Arduino the simplest thing is just to use GRBL which deals with the acceleration for you.  The motor will still stall if you try to run too fast or the load increases.

[Tony Pratt 1]

On Tony Pratt 1 Said:

On John Haine Said:

Don’t use LED PSUs for general electronics! They are designed down to a price and have poor regulation.  You can get very good switched-mode PSUs from many vendors at reasonable prices.  Here’s one from a CNC supplier.

https://www.cnc4you.co.uk/Breakout-Board-and-PSU/400W-PSU-36Volt-11Amp

Would 48 volts be ‘better’/more powerful?

Tony

Yeah, but no, but yes!

Stepper motors respond to pulses, and the best power supply for this is high-voltage, because that provides a fast rise-time.  However, the turning power of the motor depends on amps, not volts, so although high-voltage is important at pulse start, the ability of the PSU to supply amps takes over during the pulse.  (The volts can drop.)

This ‘volts can start high and then drop’ is why stepper controllers have amp limit switches.   As a stiff 48V PSU could provide enough amps to damage the motor, the electronics can be set to protect the motor by limiting the current.   They should be set to the motor’s maximum current rating, or a little below.   (Or if the PSU is too small, set them to protect the PSU!)  Don’t limit the amps unnecessarily, because that slugs the motor, making it more likely to lose steps.  Double check the switches to make sure the controller allows 5A.

Volts and amps depend on the motor, but for example one that allows the volts to charge a big capacitor to, say 48V, and then delivers sustained amps at about 36V would be good. No need for regulation, in fact a regulated PSU might well struggle with a pulsed load.  Though I’ve used them to drive steppers successfully cos they’re cheap and available, a LED supply might not cope with a stepper.  Much depends on the PSU’s circuitry, which absolutely wasn’t designed for rapidly varying loads, and we have no idea what it is.  The ideal stepper supply is surprisingly basic – like an old-fashioned unregulated car battery charger.

Bob said “My only reservation is the power supply which is 36 volt 5 amp.(amazon ref LED 36V 5A – 10A 180W-360W). It seems that this is intended for LED lighting, cars and public lighting. Could this be an area of concern? I thought 5 amps was 5 amps But !!!!!”  I think he’s right to worry.  The supply is reasonable on paper but the pulsing electrical load imposed by a stepper is nothing like DC, AC single-phase or AC 3-phase.  “5A” is the average current the stepper can cope with without overheating, and it’s possible the high-speed pulsing is too much for the PSU, which cuts the output in an attempt to maintain regulation – poor thing might even be having an electronic nervous breakdown!    An oscilloscope would reveal if this is a problem.

After confirming the problem isn’t mechanical by turning the drive by hand to make sure nothing is binding (over-tight gibs?), I’d:

• Increase the amp limit up to about 6A, and keep an eye on how hot the motor gets during a long ELS run. If it stays cool, go higher.  If that doesn’t help.
• Up the PSU to 48V, looking for one that’s stepper friendly rather than a LED type.   I’d risk this even if the motor is only 36V

In principle Bob’s set-up looks OK to me – it should fly.

Dave

[Stuart Smith 5Participant @stuartsmith5]

Bob

The power supply you have looks like the standard type used with stepper motors so should be ok.

The stepper driver you have is rated up to 50v so you could try a 48v power supply with it.

The driver controls the current to the stepper so you don’t need to be concerned about the voltage of the power supply as long as it is within the rating of the driver (ie the DM556T you have).

The higher voltage allows a faster increase in current pulse so can cope with high speed/ high torque combination better.

Daves last comment about the motor voltage is misleading. It is the job of the driver to control the current to the motor.

Stuart

[John HinkleyParticipant @johnhinkley26699]

I am not qualified to comment on either of the above two responses.  However, I was astonished to hear that the stepper can be stalled simply by grabbing the output shaft!  If it were my installation, I’d go back to Stepperonline and purchase one of their recommended 48V power supplies.  I note that your stepper doesn’t have the encoder feedback, so errors will go undetected and so uncorrected (as experienced by Tony Pratt 1, earlier in the thread). Another stepper motor would be my choice – but it’s not my money that I’d be spending!  See the stepper/power supply/driver combo in my first link, (sadly out of stock).

John

[Robert Atkinson 2Participant @robertatkinson2]

The main reason Stepper motors run “better” (faster for the same torque) is because of the back emf generated by the rotating magnetic field of the rotor . This opposes the applied voltage reducing the current and thus the torque. Modern drivers have currnet control which helps a lot but it still requires a high enough supply voltage. The supply still needs to supply the peak current.
A cheap power supply designed for LED  lighrts is not a good choice. You could try connecting a large electrolytic capacitor (1000’s of microfarads more is better) at the supply input terminals of the stepper driver if you have one. As a general rule use the highest supply voltage the stepper drive can handle. A simple linear suppy with just a transformer, bridge rectifier and big smoothing capacitor will work as well, if not better than a complex regulated supply. At 30V (or 2 15V windings in series) transformer is good for a driver that will accept 48V input.
A ELS on a conventional lathe has one disadvantage over a typical CNC system, you can’t ramp the speed up, it has to be syncronous with the spindle which you have no control over.
It seems to me that 840RPM is very fast for screwcutting.

Robert.

P.S. Hoping to fit a electronicleadscreweu single axis to my ML7 over the holidays. All the bits are in.

[John HinkleyParticipant @johnhinkley26699]

I thought that I’d posted a follow-up to this thread, but it seems to have gone “walkies”, So I’ll repeat what I can remember of it……

Robert,

You appear to have considerable expertise in the field of electronics, so I, for one, would be interested to see/hear what your collection of “bits” are.  Please post your purchases an a report of your finished project.

John

 

[Speedy Builder5Participant @speedybuilder5]

Thanks to all those who have responded – I will have a look at Stepper on-line for a matched PSU and hope it doesn’t cost more than the motor/controler.

Bob

[John Hinkley]

On John Hinkley Said:

I thought that I’d posted a follow-up to this thread, but it seems to have gone “walkies”, So I’ll repeat what I can remember of it……

Robert,

You appear to have considerable expertise in the field of electronics, so I, for one, would be interested to see/hear what your collection of “bits” are.  Please post your purchases an a report of your finished project.

John

 

Hi John, see the motorun thread

30 Year old MOTORUN 3 Phase Static converter

[John HaineParticipant @johnhaine32865]

I’ll say it again, the current from the supply will likely be significantly less than the stepper coil current.  A 3Nm stepper from Stepperonline has a coil resistance of about 1 ohm.  At 4.2A continuous that’s about 4V drop or 16 watts.  The stepper motor is a highly inductive load and the driver exploits this in effect by operating as a switched mode power supply, pulsing the voltage applied to the motor and commutating the current in the “off” periods to keep the average current at the correct level .  There are 2 windings, so even if both were at 4A the power would be 32W and from a 40V supply the supply current would only need to be 32/40 = 0.8A.  Peak current can be much higher and that’s what jiggers LED supplies that have poor regulation.  As Dave says, transformer/rectifier supplies can be better.  On my lathe I use just that, but my mill has a “component PSU” off eBay rated at 40V and a few amps, it can happily supply 3 steppers (X, Y, Z, and rotary axes) without problems.

As another example, my Ward controller puzzled me at first as though I had the stepper current set to 2A the actual supply current on the PSU meter was much less than an amp.  See also the Polulu website and look up DRV8825 which is a TI driver chip.  There’s a link to an application video that describes how to set the coil current and actually shows the measurement of the supply current and explains why it is so much lower than the coil current you just set.

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

……
A ELS on a conventional lathe has one disadvantage over a typical CNC system, you can’t ramp the speed up, it has to be syncronous with the spindle which you have no control over.
It seems to me that 840RPM is very fast for screwcutting.

Robert.

P.S. Hoping to fit a electronicleadscreweu single axis to my ML7 over the holidays. All the bits are in.

If that’s the case it is a poor design!  Even Mach3 does better than this.  The trick is to have a 1ppr index pulse and use that to trigger the acceleration from a fixed start position for each pass, returning to the same start after the cut.  You can also have an encoder to give finer control of cutting speed as in more advanced lathe CNC controls.

[Colin DParticipant @colind]

For a perfect example of a really neat, well designed and engineered ELS installation, i would strongly advise watching some of John Hinckleys you tube videos showing his asian 9 × 20 lathe. A key factor i think is that it is a closed loop setup, which helps in my opinion.  I did have a career in instrumentation and process control for 40 years, so I’m not totally clueless in these matters ! (just partly).

I’m not sure how to insert a link, but if you search for “bizzi bee workshop” you should find them.

Colin Drakes

[John HinkleyParticipant @johnhinkley26699]

Thanks for the plug, Colin!  For anyone who is interested, this is the link to the first (of four) videos that cover the installation on the 9×20 lathe using the Clough42 hardware and software.  I can only apologise for the adverts – I have no control over their content or positioning.  I don’t even get any payment for them – not that I want any.

I’m not too sure what is being referred to by Robert, when he says the speed “cannot be ramped up” while turning.  When screw cutting, it is obviously the case that it must be synchronised with the spindle.  However, if I recall correctly, the Z-axis feed rate can be altered “on-the-fly” at the press of a button on the Clough42 system as well as the ELS.eu system.  I don’t know for sure, but I can’t see why the two axis version of the latter wouldn’t apply the same logic to the X-axis control as well, for example, altering the feed rate when facing or even parting off.

John

 

[HowiParticipant @howi]

for anyone thinking of fitting an ELS and like to play with electronics, there are dozens of different ways to impliment an ELS on GitHub. They vary from the sublime to the ridiculous but I can recommend NANOELS.

Cheap and simple to make, you can get a PCB from China or (like I did) build on modern day perf (proto) board.

If anyone wants more info I can give you more and “Like wot I did!” sceneario.

 

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