[WhiteHare]

https://www.cnczone.com/forums/attac...d=446992&stc=1




Anyone here have experience with these "mechaduino" type closed loop drivers?
https://github.com/jcchurch13/Mechaduino-Firmware

It was a kickstarter thing that delivered and then finished. It's now open sourced. You can either build it yourself from the github files or you can buy clones for $15 on aliexpress. I have 3 of them on order from Aliexpress (I opted for "servo42a") and was wondering if anyone else has tried them also.

I'm using CNC to etch PCB's on a modest 2418 CNC router, and with the low torque that comes with microstepping, I just want to ensure I'm not missing any z-axis steps and/or lateral steps on fine pitch etches.

There's also Ustepper, made in Denmark and of a similar design, and it looks to be nice because it uses Trinamic TMC5160's and can handle a bit more current. It's newer though, so I wasn't sure as to whether it's still in the de-bug phase.

[NIC 77]

with the low torque that comes with microstepping,

There was an article that was published by someone many years ago that is circulating the internet, that is commonly misinterpreted. It was actually about accuracy at higher microsteps, not torque loss due to microstepping. It gets regurgitated just about everywhere.

I'm not really smart with all of the electronics that drive stepper motors, but what I've come to understand is that with a good driver, you won't loose much (if any) torque while microstepping. But you shouldn't expect that using a really high number of microsteps will increase your accuracy proportionately.

Anyone here have experience with these "mechaduino" type closed loop drivers?

I don't think many people on these forums use Nema 17's. Are these available for Nema 23's or 34's?

Really interesting.

So the dev's of this are saying that these aren't closed loop steppers.....that instead they've converted a stepper motor into a true servo motor.

So it's a closed loop system that has no rotary encoder. It still uses a stepper driver, the A4954 as a component on the board...they should have used a trinamic driver.

How is this a servo and not a closed loop stepper? It would be interesting to see a before and after torque chart for a motor with one of these on it!

The encoder without adding any additional rotating parts is really cool.

https://www.kickstarter.com/projects...strial-servo-m

https://tropical-labs.com/mechaduino/

Mechaduino is an affordable open-source servo motor for DIY and professional mechatronics under development at Tropical Labs. Mechaduino is Arduino-compatible for ease of use.

About:

Engineers use servo motors to achieve the precision motion required in applications such as robotics, automation, and CNC manufacturing. Like RC servos, industrial servos actively correct for external disturbances. Unlike RC servos, industrial servos can provide very accurate motion, and often support advanced motion control modes. Unfortunately the cost of industrial servos is prohibitive to the individual maker.

Tropical Labs engineers have been developing an affordable open-source servo motor, opening the door to sophisticated mechatronics applications. Our design leverages the low cost of mass produced stepper motors. We are able to achieve very high resolution via 14b encoder feedback (after calibration routine!).

Is this this the same thing? It still has the salmon skin on 3d prints common with the Allegro drivers.

https://www.youtube.com/watch?v=R1TghZmE6Gs

[WhiteHare]

Is this this the same thing? It still has the salmon skin on 3d prints common with the Allegro drivers.

https://www.youtube.com/watch?v=R1TghZmE6Gs

Yes, that's the model that I have on order. They did their own board spin. The end of the user manuals says "much of the work is based on Mechaduino project by J. Church." At a glance, it looks substantially the same, and I'm hoping that it is, because the Mechaduino seems to have reasonably good documentation.

Teaching Tech reviewed a variant of it (called the SERVO42B), based on an STM32, where he several times whacks a 3D printer hard with a mallet while it's doing a print, and--unlike an open loop stepper-- it doesn't shift any layers:
https://www.youtube.com/watch?v=eM8zSG8fEkk&t=756s
It's a pretty cool demo.

[NIC 77]

These 3d printers can push the Nema 17's too far. Also, sometimes the inexpensive electronics are not the best. These factors can lead to missed steps and layer shifts. Also, running at 12V is not ideal. Better printers will have a Nema 23 moving the bed.

Some of the electronics can be really good though, things like the Duet boards.

For the kinds of routers and such usually discussed here, using the larger stepper motors, Nema 23 or 34 with good quality drivers, missed steps aren't normally an issue unless there is a design flaw, mismatched components, or unrealistic expectations on speed and acceleration in relation to the motor torque.

I read that these claim a resolution of 0.1 degree, but it wasn't on the official website that I could find....if that's true, for a 1.8 degree stepper, it's the equivalent of 18X microstepping with a closed loop guaranteed resolution, and if that's true it's pretty darn good!

Teaching Tech has one video I like about nonplanar 3d printing.

I'd like to see a version of this for some larger motors. It's too bad the salmon skin artifacting is still present.

[WhiteHare]

I'd like to see a version of this for some larger motors.

Wish granted. Makerbase has a similar driver for nema23's called servo57A and servo57B:
https://www.aliexpress.com/item/3296...778b1b968s1qZU
and its priced the same as the nema17 closed loop driver.

What seems like the biggest barrier to nema23 adoption is the greater current requirements exceed the typical inexpensive driver modules.. However, with an inexpensive closed loop driver such as this to power a nema23, I suppose that barrier goes away.

The MKS user manual hints that it might (?) be wired into a duet board through the duet board test pins. It didn't sound terribly definitive though.

[NIC 77]

[QUOTE=WhiteHare;2395338]Wish granted. Makerbase has a similar driver for nema23's called servo57A and servo57B:
https://www.aliexpress.com/item/3296...778b1b968s1qZU

That one is limited to 3 Amps Peak and 24V. Still an improvement. What driver is on the board? I couldn't tell.

I have recently become interested in these:

Home

Trinamic driver based, 4.33A up to 60V. Put that on the makerbase board!

I think the new Duet 3 board's onboard drivers are good for up to 6A, but limited to 24V in practice.

What seems like the biggest barrier to nema23 adoption is the greater current requirements exceed the typical inexpensive driver modules.. However, with an inexpensive closed loop driver such as this to power a nema23, I suppose that barrier goes away.

A good higher current Gecko or Leadshine open loop stepper driver might cost $50 to $100 per driver, so compared to a $10 Allegro driver, yes it's a different kind of thing.

But the newer trinamic based drivers like the one I posted a link to could be a game changer in this area.

The Makerbase board is totally cool, but it still needs a stepper driver on it to run.

The MKS user manual hints that it might (?) be wired into a duet board through the duet board test pins. It didn't sound terribly definitive though.

An expansion board should give the pinouts to run this as an external driver from a Duet board. I'm working on an industrial 3d printer project at the moment. I wonder if I should use some of these makerbase boards for the extruders. Eventually I want to try doing pellet extrusion, but first I need to get the basics running.

[WhiteHare]

I read that these claim a resolution of 0.1 degree, but it wasn't on the official website that I could find....if that's true, for a 1.8 degree stepper, it's the equivalent of 18X microstepping with a closed loop guaranteed resolution, and if that's true it's pretty darn good!

Yup. The acme screw on my cnc advances 2mm per revolution. So, that would be 2/3600=0.00056mm per step, guaranteed. Provided that it has enough holding power, that should be plenty good enough for milling a PCB, including carefully grinding off solder mask above the pads (without grinding off the pads). Well, at least there's reason to hope it might be good enough.

According to package tracking, the package is now in my country. So, I expect I'll receive it sometime next week, or maybe earlier.

If holding power turns out to be an issue, then I'll switch tactics by maybe getting ample precision from using planetary gears, which will surely provide ample holding power as well. With a 100:1 gear reduction, I probably wouldn't need to microstep at all. The only question then would be whether or not I could run the stepper at 100x the speed so that the whole operation doesn't crawl. Seems unlikely, doesn't it? Maybe this is the reason why a 5x gear reduction is the most popular.

[NIC 77]

Yup. The acme screw on my cnc advances 2mm per revolution. So, that would be 2/3600=0.00056mm per step, guaranteed. Provided that it has enough holding power, that should be plenty good enough for milling a PCB, including carefully grinding off solder mask above the pads (without grinding off the pads). Well, at least there's reason to hope it might be good enough.

According to package tracking, the package is now in my country. So, I expect I'll receive it sometime next week, or maybe earlier.

If holding power turns out to be an issue, then I'll switch tactics by maybe getting ample precision from using planetary gears, which will surely provide ample holding power as well. With a 100:1 gear reduction, I probably wouldn't need to microstep at all. The only question then would be whether or not I could run the stepper at 100x the speed so that the whole operation doesn't crawl. Seems unlikely, doesn't it? Maybe this is the reason why a 5x gear reduction is the most popular.

With a 2mm lead, it will be slow anyway.

With 100:1 gear reduction, it would be unuseable. You are stuck thinking that you will loose torque by microstepping. Like I mentioned, that article that has been misinterpreted, it's about accuracy. You need microstepping to smooth out the motor. That's for a regular stepper motor.

Whatever the next increment at 18x or above is for microstepping would be my guess for these drivers. Do you even have the option to adjust it? They've changed up how it works and claim it's a servo now. You just use it as intended. Trying to change it to lower microstepping will not get you more torque.

There are a few things to consider when using gear reduction...low backlash planetaries are expensive, alot more than a larger stepper... inexpensive ones will have backlash.

The rotary inertia of the gear is important when considering the acceleration of the system, and for a 5:1 planetary, the output acceleration of the planetary will be 5 times less than the acceleration of the motor. For what you're doing with a 2mm lead, I can't see this being a good choice. It would be very slow.

You might find that your motors can not keep up when you try to go too fast, and this has a few factors, speed, acceleration, and the motor torque graph. You might be better off to go with an 8mm lead screw, the opposite of using gear reduction.

Not knowing anything about your design or what you hope to achieve for performance, top speed and acceleration, I can't really say more.

With the closed loop motor, the accuracy you will achieve will be limited by your other components, such as your end support bearings, your leadscrew and leadnut, and your spindle. Also your linear bearings and machine design. So in practice if you can get to 0.05mm or 0.002" accuracy then you've done very well.

[WhiteHare]

I read that these claim a resolution of 0.1 degree, but it wasn't on the official website that I could find....if that's true, for a 1.8 degree stepper, it's the equivalent of 18X microstepping with a closed loop guaranteed resolution, and if that's true it's pretty darn good!

It's a wonder that it has taken so long for stepper products to surface in this area. A full 10 years ago magnetic encoders were allowing for 0.08 degree accuracy and repeatability in RC servos in a similar "all-in-one" design:
https://www.youtube.com/watch?v=8jajnIBX2cU

[NIC 77]

What is it that you're building? What's your design? What Nema 17 motors do you have, have you bought them yet?

I had a look at the Bantam tools machine. I was curious what components they used as far as bearing supports for the leadscrews and also the lead of the leadscrews they use. Couldn't find any nitty gritty details. All hype videos. What have you found in your design research?

IMO, if you're making a machine, consider a minimum max speed of 100 IPM. With a 2mm lead, I'm not sure you'll get there at any decent acceleration.

https://www.bantamtools.com/machines...illing-machine

$3600 USD, not inexpensive. IMO, you are better of with an Omio CNC that has square rails...some of them have round...avoid those.

https://www.omiocnc.com/

https://www.omiocnc.com/products/x4-...-800l-usb.html

In general, the unsupported round rails are the worst for CNC. You're doing some very light work for pcb milling, so you can get away with quite alot. It doesn't need to be perfect or expensive. The frame can be made of wood. Do you have a budget for this?

Another option would be 3 of these and a short travel Z axis

https://www.ebay.ca/itm/Linear-actua.../202373227731?

[Al_The_Man]

I'm surprised to still see the usage of NEMA as a power reference for steppers/motors, NEMA is a mounting frame size and has not alot to do with power.
For e.g. I have catalogues for a couple of the very large Stepper manufacturers, they have certain NEMA size motors with different core (body) length, each one has a different Nm torque value, but have exactly the same (NEMA#) mounting .
Al.

[NIC 77]

I'm surprised to still see the usage of NEMA as a power reference for steppers/motors, NEMA is a mounting frame size and has not alot to do with power.
For e.g. I have catalogues for a couple of the very large Stepper manufacturers, they have certain NEMA size motors with different core (body) length, each one has a different Nm torque value, but have exactly the same (NEMA#) mounting .
Al.

That's true Al. Good point.

Typically the Nema 17 motors used on 3d printers are pretty wimpy and on better printers, the bed will be moved with a Nema 23 that has more torque. But it's just a generalization, and you need to look at the specs of each motor to make a valid comparison. I thought that was an obvious thing, sorry if I mislead anyone.

[Al_The_Man]

Something missing seems to be the reason for the higher voltage when using steppers.
Stepper motors have a fixed operating voltage and current stated on the plate, and if you were to run them with a fixed voltage, then that plate voltage should not be exceeded as you would then exceed the current. With possible destruction.
But as you increase speed with a stepper, the inductive reactance increases, therefore limiting the current (torque), In order to overcome this drop in torque, a higher voltage is used for the drive, which in turn maintains the very important plate CURRENT, and should not exceed it.
IOW, from zero rpm to maximum operating RPM, the drive maintains the current as a constant.
Al.
.

[WhiteHare]

Something missing seems to be the reason for the higher voltage when using steppers.
Stepper motors have a fixed operating voltage and current stated on the plate, and if you were to run them with a fixed voltage, then that plate voltage should not be exceeded as you would then exceed the current. With possible destruction.
But as you increase speed with a stepper, the inductive reactance increases, therefore limiting the current (torque), In order to overcome this drop in torque, a higher voltage is used for the drive, which in turn maintains the very important plate CURRENT, and should not exceed it.
IOW, from zero rpm to maximum operating RPM, the drive maintains the current as a constant.
Al.
.

Agreed. That's how I'm assuming it works.

So, based on that, do you agree that being able to drive from higher voltages is a good thing? I mean it may not be strictly necessary (lower voltages just mean arriving at your destination a bit more slowly), but in general it's a good thing and therefore preferable. Right? The only downside I've read is that if you go too high, then you may start to encounter resonance because of the "stiffer" response.

[WhiteHare]

This might be the best so far, except that it comes at a cost of $364:
https://www.cnczone.com/forums/attac...d=447380&stc=1


https://www.grainger.com/product/MITUTOYO-Balanced-Reading-Zero-Setter-54GF31

Great specs though.

[Al_The_Man]

You start to encounter the effects of increased inductive reactance at a comparatively low rpm, so the necessity to maintain the rated current, comes in early in the required RPM range, so modern stepper drives all use a higher voltage, the drive manuf, should offer the required data.
Go to sites such as Gecko, you should find technical info there that explains the difference in drive settings.
Al.

[WhiteHare]

You start to encounter the effects of increased inductive reactance at a comparatively low rpm, so the necessity to maintain the rated current, comes in early in the required RPM range, so modern stepper drives all use a higher voltage, the drive manuf, should offer the required data.
Al.

Which data exactly? Here's the datasheet: https://www.omc-stepperonline.com/do...HS24-2104S.pdf

Is that a typical datasheet? Not much there. Certainly no guidance as to preferred application voltages that I can see. In fact, no mention of voltages at all.

The torque curve that's provided was generated at 24v, if that means anything: https://www.omc-stepperonline.com/do...rque_Curve.pdf That's about the only hint. Are we to assume that 24v is prescriptive? I'm guessing 24v half-step was chosen simply to have a common baseline to compare different steppers, and there's no significance beyond that.

[WhiteHare]

By the way, if you look at time index 20:00 on this video:
https://www.youtube.com/watch?v=otOVJv_FA8k

you'll see that he does the same kind of rapid "return to zero" repeatability test on the z-axis as what I'm aiming to do, except that he's doing it on the upstroke rather than the downstroke. Well, at least in his case, he gets it to work spot-on, and with far more inertial mass than what I'm dealing with. And later in the video he reveals that he's driving his at higher velocity than what I am as well. He's running his z-axis at anywhere from 1000mm/min to 2000mm/min, whereas mine, by the default GRBL settings that override g-code, can't be more than 800mm/min. So, he has more intertial mass and greater momentum and great speed, and yet his setup is not over-running on a retutrn-to-zero. Instead, as shown by the dial gauge, it returns precisely where it should at the end of a rapid. So, I just mention all of that because plainly those aren't limiting factors by themselves.

[Al_The_Man]

That is just motor data, as per my post, I was referring to the manuf. specs of the drive that normally include able to set for a particular motor specs.
Al.

[WhiteHare]

That is just motor data, as per my post, I was referring to the manuf. specs of the drive that normally include able to set for a particular motor specs.
Al.

Thanks for clarifying. I misunderstood your earlier post because I normally understand drive and driver to be two different things. I'll take a closer look at the driver documentation.

Thanks for the pointer!