Stepper Options

[blkexp98]

I have a SX3 and a CNC Fusion kit that I plan to install soon. Ive been thinking about this for a while now and keep going back and fourth. I know I want to go with seperates as far as the drivers are concerned but am unclear on the brand of steppers and drivers. I also plan to buy dual shaft steppers and install encoders on them either now or upgrade them to that later. Does anyone have any experience with that? The closed loop stepper and servo setups are out of my price range for now. I was going to use mach 4 but have really been leaning more towards Linuxcnc the more I read about it.

Ive been under the assumption that the stepper motors and drivers from automation technologies are Leadshine or at least a US rebadged import. Is that correct or not? My plan initially was to go with the Gecko G203V or G213V drives but read the leadshine drives had some superior features and the Geckos were very reliable but aged technology. The following is what I am currently looking at for the build. Feel free to tell me if I need to rethink anything, if it looks like a good idea or if im missing something significant.

2x - KL-5056D Digital Bipolar Stepper Motor Driver-32 bit DSP Based https://www.automationtechnologiesin...k-is-included/
1x - KL-8070D Digital Bipolar Stepper Motor Driver-32 bit DSP Based https://www.automationtechnologiesin...k-is-included/
1x - Unregulated Linear 960W/ 48 VDC/20A Toroidal PSU (KL-4820) with 5VDC https://www.automationtechnologiesin...l-psu-kl-4820/

I dont know what I should do about the BOB just yet. Ill have to look more into what will work with Linuxcnc and give me spindle control options as well as the ability for at least 4 axis's.

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[ger21]

I also plan to buy dual shaft steppers and install encoders on them either now or upgrade them to that later.

Imo, that's a waste of time and money, and provides almost no benefit. If you don't try to run the machine faster than the motors are capable of running it, you'll never lose steps.
And if you are losing steps, the encoders won't stop that from happening.

Ive been under the assumption that the stepper motors and drivers from automation technologies are Leadshine or at least a US rebadged import.

I don't think their steppers are Leadshine, but I could be wrong. Their drives are Leadshines, though.

I would say that the steppers used by 97% of the members here are some unknown brand of chinese import. Steppers are pretty simple devices, and for the most part are very reliable. You rarely here about faulty steppers.

My plan initially was to go with the Gecko G203V or G213V drives but read the leadshine drives had some superior features and the Geckos were very reliable but aged technology.

That depends on who you ask. I think they are both good drives.

Another option is Leadshine AM882's, from China. No support, but you get a better drive for less money.
Leadshine AM882 Digital Stepper motor Drive 80VDC 0.1A - 8.2A protect function

What motors do you plan on using? Usually you buy your drives to match the motors, not the other way around.

[Torchhead]

You need to rethink adding encoders to a stepper. You can use them in closed loop only to verify position for throwing a fault. Steppers are constant current devices and torque comes from current. You cannot force them to have more torque at a given RPM . In short if you are at a point where the motor is losing steps there is nothing you can do to make it stop (stalling) unless you decrease the load or decrease the RPM. Just adding more steps deepens the "stall". Like pulling back on the stick harder if your plane stalls instead of increasing power.

Either you have servos or you don't . Stepper motors have different Physics than servos. The good news is a properly sized and designed stepper system operated inside the RPM-torque curve of the motor does not lose steps. Steppers generally lose torque at a linear rate up to about 50% of their top loaded RPM . After that they lose at a sharper rate . Your gearing to the final drive should reflect these constraints . If you projected top cutting speed is 100 IPM then you need a final transmission that will offer you that speed at about 1/2 the static loaded RPM. Use 600 RPM if you don't have motor torque curves as the top RPM so 300-400 for the mid range.

You may find on some larger motors that a higher voltage might be in order to overcome the inductive effects to get top RPM. Most of the larger stepper drivers are rated up to 80VDC. Gecko site has lots of documents on stepper motors.

[SCzEngrgGroup]

You may find on some larger motors that a higher voltage might be in order to overcome the inductive effects to get top RPM. Most of the larger stepper drivers are rated up to 80VDC. Gecko site has lots of documents on stepper motors.

The optimal voltage for a stepper has absolutely nothing to do with the size of the motor. It has everything to do with the inductance of the motors coils, and the target operating RPM - high inductance motors NEED higher voltage to achieve higher RPMs. There are very small motors that have high inductance, and require high voltage, and there are large motors with low inductance that operate well with lower voltage.

Regards,
Ray L.

[blkexp98]

Thats the kind of info I was looking for and it will save some money and trouble as well. Ill try to find out some more info on these motors. Ill also take a look at those drives and see what they offer as well.

These were the two steppers I was looking at.
- NEMA23 570oz/in 5A 3/8” Dual Shaft Stepper Motor (KL23H2100-50-4B) https://www.automationtechnologiesin...lat-570-oz-in/
- NEMA34 Stepper Motor – 906 oz in 6.1A Single Shaft (KL34H295-43-8A) https://www.automationtechnologiesin...l34h295-43-8a/

[ger21]

I haven't tried it on a machine yet, but I've been testing that 570oz motor with the AM882, and it seems to work very well.

[109jb]

I disagree that encoders on steppers are useless. A perfectly set up machine can lose steps simply because of a dull tool, a gib adjusted a bit too tight, or even a coding error. You can set them up so that if the encoder position doesn't match the commanded position the machine will fault and stop letting you examine the reason for the fault rather than totally scrapping a part, milling into a vise, etc. I actually have encoders purchased to do just that on my G0704, but family issues have kept me out of the shop for quite some time.

[ger21]

If you are losing steps because of a dull tool, you're trying to get too much out of your steppers. A properly setup machine should never lose steps from a dull tool. If they do, then you don't have enough power for the application.
Steppers get a bad rap because people expect too much from them. There are millions of machines (of all kinds) that use steppers that never lose steps.

[Torchhead]

Useless in terms of having closed loop control (adjusting the torque as it cuts to maintain position as it cuts) . Possibly useful to fault if the motor stalls and to only screw up a small area. it only works if the fault causes a system e-stop. No one says that a machine that loses steps is not "setup right", it says that either the original design is flawed and its being operated outside its limits, or something has occurred that forces the machine outside of its normal cut parameters.

The statement about larger motors may need a higher voltage was too generalized. It is all about inductance and the charge time of a given coil when a given voltage is applied. Because of the Physics of magnetic structures and coils often a larger motor has more inductance (just as a larger transformer has more inductance) That is not always true. A smaller motor can have higher inductance. The concept is to understand the charge/time relationship of a motor to its top RPM. The current density (amp-turns) of a magnetic device effects its inductance and also its core saturation point and heat loss. Its a balance for a designer to make a device that has the power in a given size and have the best characteristics to perform the job it has to do. Sometimes when you simplify and generalize not all variations are covered.

[SCzEngrgGroup]

I disagree that encoders on steppers are useless. A perfectly set up machine can lose steps simply because of a dull tool, a gib adjusted a bit too tight, or even a coding error. You can set them up so that if the encoder position doesn't match the commanded position the machine will fault and stop letting you examine the reason for the fault rather than totally scrapping a part, milling into a vise, etc. I actually have encoders purchased to do just that on my G0704, but family issues have kept me out of the shop for quite some time.

Nonsense. A properly designed drive will have more than enough reserve to handle anything short of a hard crash without losing steps. I ran steppers for years, and never once lost a step, except when I crashed the spindle into my vise, or some other immovable object. Even breaking a 1/2" endmill did not cause lost steps. If a dull tool is enough to cause lost steps, you're drive is under-powered, and you're living on borrowed time.

Regards,
Ray L.

[109jb]

If you don't have encoders then saying that you have "never" lost a step is only a guess. Can you see 0.0001" or even 0.003". Each microstep on my machine is 0.0001" theoretical resolution. I plan to set my encoder up to fault the machine if commanded position is off by more than 0.005" and if you say you have a way to detect that without an encoder then then please tell how????

A dull tool in aluminum can heat and then clog by welding the aluminum cuttings to the tool. That tool no longer cuts and you wind up trying to push it through the stock. Are you saying that a tool that is no longer cutting because of this can't cause lost steps??

I am not bashing steppers. I think they are great and absolutely fine for the task, but still disagree that encoders are useless on them.

[arizonavideo]

With the Nema 23 steppers most are really not a good match with small mills. The 150 oz to 300 oz range are a little small so only a few are larger and most have fairly high inductance so are poor at high speed unless you run a 80V driver.

The one stepper that stands out is the 570oz 5A stepper. It has a really low inductance so is way faster at high speed and has more power than you need.

Run it at 4A on the X and Y and you will get 150 IPM at 50V all day long.

Really no reason to spend more. For normal use it will be fast and you should never loose steps.

Best stepper ever.....

For small mills at 50V

[fifa]

Comment to one previous post: If stepper loose step you will see it , motor will start stall. You can not see failing of micro stepping, however if position error increases to step motor will stall.

Micro stepping helps to improve vibration reduction, its purpose is not to improve resolution. Leadshine drivers works fine. Almost like servos. But the price is too high. Cheap and reliable servos can be found for same money.

Check this page: CNC | Galil

They are very good.

kr

[ger21]

Each microstep on my machine is 0.0001" theoretical resolution

You can be off several microsteps without losing steps. They will eventually catch up. Consider your actual resolution to be 1/2 step. You aren't losing steps until you lose a full step or more. And the chances of losing a single step are incredibly slim. If you are losing one step, then you'll lose a lot more than one.

If you don't have encoders then saying that you have "never" lost a step is only a guess. Can you see 0.0001" or even 0.003"

If you can't tell if you're losing steps, then you're probably not, and don't need encoders.

[RCaffin]

The funny thing about steppers is that once you have lost ONE step, you are very likely to lose the rest as well (as Gerry said). So it is not a case of having to detect 0.0001"; rather it is a case of having the machine stall.
In addition, you can usually hear when a stepper loses just a few steps.

A dull tool in aluminum can heat and then clog by welding the aluminum cuttings to the tool. That tool no longer cuts and you wind up trying to push it through the stock. Are you saying that a tool that is no longer cutting because of this can't cause lost steps??
That is called Built Up Edge (BUE). It is not always due to a dull cutter; it can be due to the aluminium alloy (some are chewing gum) or the surface of the cutter. (Mist lubication is the cure there.)
Regardless, when it happens you do not lose a few steps: you usually lose the whole cutter with a big bang. And probably the job too.

Cheers
Roger

[ger21]

A dull tool in aluminum can heat and then clog by welding the aluminum cuttings to the tool. That tool no longer cuts and you wind up trying to push it through the stock. Are you saying that a tool that is no longer cutting because of this can't cause lost steps??

Either the tool breaks, or the machine stalls.
You need encoders to tell you that?

[SCzEngrgGroup]

If you don't have encoders then saying that you have "never" lost a step is only a guess. Can you see 0.0001" or even 0.003". Each microstep on my machine is 0.0001" theoretical resolution. I plan to set my encoder up to fault the machine if commanded position is off by more than 0.005" and if you say you have a way to detect that without an encoder then then please tell how????

There are so many things wrong with that argument, I wouldn't even know where to begin. It is clear you do not really understand how stepper motors work, nor how using encoders to detect "lost steps" is actually implemented. You will NEVER be able to detect one of your theoretical 0.0001" "lost steps", even it if were possible to "lose" a 0.0001" step (which it is most definitely not). And if you did somehow manage to build a system that could detect such a small loss, it would be constantly false-tripping due to following error alone. In reality, you'd be lucky to reliably detect even a 0.003" static position loss. And I can assure you a 0.003" loss is easy to detect visually.

I suggest you spend a lot of time reading and researching how stepper motors really respond, in the real world, where things like friction, stiction, inertia, and other physical factors interfere with the "theoretical". Learn how a real stepper motor responds to micro-stepping, and you'll realize even talking about 0.0001" is ridiculous. Factor in the real-world characteristics of the machines being talked about here, and it becomes downright ludicrous. Learn that micro-stepping has virtually nothing to do with increasing resolution, but is, rather, used primarily to reduce resonance at low-to-moderate speeds, and that many drivers automatically switch to full-step mode at higher step rates.

And, if I follow your argument, I am wrong to suggest that I can tell if my open-loop machine is losing steps, because I can't possibly detect a 0.0001" position error, but you are going to allow a 0.005" position error on your machine before you trip a fault? Do you see a logical contradiction there? How is a 0.005" position loss acceptable, when a 0.0001" loss is not? How do you suppose you are likely to ever achieve a 0.005" position loss without stalling the motor? The fact is, with steppers, once you've lost a single step while moving at anything other than extremely low speed, the motor is almost guaranteed to stall. THAT is easily detected without encoders.

Finally, consider this: If simply adding inexpensive encoders to a stepper motor (and decent optical encoders can be bought for a few $ now) has such wonderful, wide-ranging benefits, why is it so very, very rarely done, even in the industrial world, where cost is not nearly as much of an issue as it is here? A great many extremely high-precision machines use open-loop steppers, with virtually 100% reliability.

Regards,
Ray L.

[arizonavideo]

Ont thing that happens with a stepper that looses a step is when a coil does not "sink a load" or transfer its power to the armature of the stepper, it just dissipates the field all around and disrupts the surrounding magnetic fields.

Often under heavy load a stepper will just give up and loose 100 steps or stall. So you dont have to guess if you lost a step.

Again running a stepper at 60% of full load to leave room for peak loads and you will almost never loose steps.

The only time I have problems with steps is if a tool clogs and melts the metal. You can hear this from next door when this happens and its not much better with my servos.

After years of milling with both steppers and servos, only a few times would encoder have helped, and only if they would have stopped the mill and not re set like I have the encoders set now.

If money is not a issue and the extra wires are OK then do encoders. To me it is just one part part to fill with chips and water.

[Torchhead]

If you don't have encoders then saying that you have "never" lost a step is only a guess. Can you see 0.0001" or even 0.003". Each microstep on my machine is 0.0001" theoretical resolution. I plan to set my encoder up to fault the machine if commanded position is off by more than 0.005" and if you say you have a way to detect that without an encoder then then please tell how????

You DO NOT have .0001" resolution. You cannot count micro stepping to increase resolution. Those who claim that are called "Marketing" people. It's there to smooth out the motion at lower RPM and prevent mechanical resonance. It eats power so you only get about 70% of the torque to the load. Most modern drivers disable mircostepping over about 200 RPM because it is basically ineffective due to motor and load inertia and is a waste of power, and limits upper torque. Couple that with the inherent 5% step error and you have a lot less raw "accuracy" than you think. Your linear mechanics have error as well . Something the encoder on the motor cannot compensate for.

Having an encoder on an axis for absolute positioning so it has to move to a given spot and stop is a useful design. Trying to use it in a PID servo type loop is less so. It's your money and your idea. Its obvious you are a man of conviction and like to plow your own fields. Go for it. If you want high accuracy you go with servos , high encoder counts, precision slides and precision anti-backlash ballscrews. Gantry mass is important to prevent flexing. All costly, but high accuracy has high costs.

A dull tool in aluminum can heat and then clog by welding the aluminum cuttings to the tool. That tool no longer cuts and you wind up trying to push it through the stock. Are you saying that a tool that is no longer cutting because of this can't cause lost steps??

Having cut literally hundreds of miles of aluminum with both steppes and servos I can tell you this: As soon as a bit starts to clog , about 1.5 seconds later it either snaps off (if its smaller) or makes a cut that looks like you cut it with a chisel! So there is no making up lost steps it will simply finally stop motion.

I am not bashing steppers. I think they are great and absolutely fine for the task, but still disagree that encoders are useless on them.

[109jb]

Either the tool breaks, or the machine stalls.
You need encoders to tell you that?

I have personally had a tool load up, the machine lose steps, the tool break below top of part, and the machine then went merrily on its way. The remaining upper portion of the tool with some of the upper part of the flutes intact then destroyed any possibility of salvaging the part while milling into my soft jaws as well. I definitely could tell that it happened after the fact but was not in the shop to stop it when it did. If I would have had encoders installed the machine would have faulted, and at a minimum saved my soft jaws, and possibly the part I was making.