precision planetary gearbox, NEMA 17 Voltage: 2.7V

[Adalbert]

Hello Pau,

With my Zeiss WL I can easily get 50nm steps with the Wemacro Micromate coupled to the fine focus knob.

Something like that?
https://www.ebay.de/itm/Carl-Zeiss-Mikr ... rk:28:pf:0
BR, ADi

[rjlittlefield]

Hello Rik,

Using this simple relationship for DoF of lambda (green)/NA^2 (think this is right, at office now and don't have my notes) gives ~609nm.

Yes, I use this simple calculation :-)
BR, ADi

That wasn't me. I was quoting mawyatt, just before explaining why I thought that was not the right number for you.

--Rik

[ray_parkhurst]

Hmm, I was dubious about the real need for such small step sizes, but was giving the benefit of doubt and hoping to learn why it would be needed. Having never stacked at 100x I didn't understand the difficulties, but indeed it seems such small steps are required.

However, such small steps are not needed at lower magnifications, so perhaps another option may be an add-on "rail" with even smaller capability...

A voice coil motor (VCM) can have essentially an arbitrarily small step size. I have sourced some small drivers with flat cones for my coin stacking which have travel of ~500um at full scale current. This could easily be reduced to 75% current, 375um range, and with 4096 steps this should give a highly reliable and linear 92nm step. I don't use the VCM for everything, but it works beautifully at 20x and at my max 40x. The steps are so smooth! And there are no side movements which might force alignment calcs. I attach the driver to my regular stage with double-stick tape, and it works beautifully.

This is just another option that gives a "2-mode" system for low and high mags. BTW, I searched and found the flat-panel drivers since I was using a vertical system. If you do horizontal, most anything will work since you will end up attaching the specimen holder to the driver cone anyway, and thus its shape is not as important.

[Pau]

Hello Pau,

With my Zeiss WL I can easily get 50nm steps with the Wemacro Micromate coupled to the fine focus knob.

Something like that?
https://www.ebay.de/itm/Carl-Zeiss-Mikr ... rk:28:pf:0
BR, ADi

Yes, I think that the GFL focus block is similar to the WL/Universal I have
100micron per turn, high precision mechanics but limited to 2mm fine focus travel, so only good for pretty flat subjects
I've posted it at http://www.photomacrography.net/forum/v ... hp?t=37209
A focus block with full fine focus travel is more convenient for general stacking work, for example a 200micron/turn Olympus BH

[genera]

Hello Gene,
Could you please show your solution with the belt-mounting?
BR, ADi

I don't use a belt.

My vertical setup uses a Parker MX80 5:1 gear box inline with the motor, mounted on a McBain Z-Scope vertical stage with a 1mm pitch leadscrew. That's all mounted on a 18 x 18 x 2" granite plate isolated by Sorbothane bumpers. There's a Seiwa focus block (very similar to a Mitutoyo focus block and graduated in um) between the Mitutoyo FS-60 microscope and the Z-Scope stage. Without the gear box I get 0.4um travel/step with microsteps of 1/16 full step. I regret adding the gear box and will remove it at some point. If I ever need smaller steps it's a simple matter to add a motorized drive to the Seiwa focus block.

My setup doesn't have much in common with what you're describing but, if you think they'll be helpful, I can take some pics.

The motor voltage rating means that if you apply that much DC voltage to the stationary coils you should see the rated current flow. It has little to do with performance since most modern drivers operate at a much higher voltage and "current limit" based on settings that you've selected. You should be able to operate safely at any voltage that doesn't exceed the maximum rating of the driver. If you do operate at voltage greater than 12v you'll get a higher maximum speed (probably more than needed for stacking) and if the voltage is too low you may end up limiting the amount of torque the motor can produce. This is, in part, because you not only have to deliver the rated current but you also have to do it in a very short period of time.

[Adalbert]

Hello Gene,

if you think they'll be helpful, I can take some pics.

Yes, please!
BR, ADi

[mawyatt]

Hello Gene,
Could you please show your solution with the belt-mounting?
BR, ADi

I don't use a belt.

My vertical setup uses a Parker MX80 5:1 gear box inline with the motor, mounted on a McBain Z-Scope vertical stage with a 1mm pitch leadscrew. That's all mounted on a 18 x 18 x 2" granite plate isolated by Sorbothane bumpers. There's a Seiwa focus block (very similar to a Mitutoyo focus block and graduated in um) between the Mitutoyo FS-60 microscope and the Z-Scope stage. Without the gear box I get 0.4um travel/step with microsteps of 1/16 full step. I regret adding the gear box and will remove it at some point. If I ever need smaller steps it's a simple matter to add a motorized drive to the Seiwa focus block.

My setup doesn't have much in common with what you're describing but, if you think they'll be helpful, I can take some pics.

The motor voltage rating means that if you apply that much DC voltage to the stationary coils you should see the rated current flow. It has little to do with performance since most modern drivers operate at a much higher voltage and "current limit" based on settings that you've selected. You should be able to operate safely at any voltage that doesn't exceed the maximum rating of the driver. If you do operate at voltage greater than 12v you'll get a higher maximum speed (probably more than needed for stacking) and if the voltage is too low you may end up limiting the amount of torque the motor can produce. This is, in part, because you not only have to deliver the rated current but you also have to do it in a very short period of time.

Hi Gene,

The controller behavior is a little more complicated than this I believe. There is the inductive Ldi/dt effect than must be accommodated by the controller and supply. With motors that have a small inductance you can get a rapid change in motor current that can change too fast for the controller to allow the proper motor current decay sequence in PWM current modes. With some older controller chips you had to set the timing of the decay sequences, with pin selection and sometimes with a resistor/capacitor changes for certain motors & supply voltages. Also, some older controllers have shown some misbehavior with certain motor/supply voltage combos (Ti chips are noted for misbehaving). I also recall someone having problems with higher supply voltages, well within the specification, but things settled down going to a lower voltage.

Another thing to watch out for is motor/controller overheating, this can even happen with small NEMA 11 motors (like the USA THK KR-15) because they have a higher voltage rating which translates to a higher internal resistance, thus higher motor internal I^2R heating. Having the ability to program the current limits under full software control has shown to be very valuable as one can tailor the motor current profile during operation and still retail the desired moving & holding torque.

The newer controllers seem to have a somewhat "automatic" mode which will hopefully eliminate or reduce the motor/supply problems seen with the older controllers, and recently I read where a controller that can sense the motor dynamic and static load situation and adjust the motor current accordingly.

Anyway, hope this helps some.

Best,

[genera]

Hello Gene,
Could you please show your solution with the belt-mounting?
BR, ADi

I don't use a belt.

My vertical setup uses a Parker MX80 5:1 gear box inline with the motor, mounted on a McBain Z-Scope vertical stage with a 1mm pitch leadscrew. That's all mounted on a 18 x 18 x 2" granite plate isolated by Sorbothane bumpers. There's a Seiwa focus block (very similar to a Mitutoyo focus block and graduated in um) between the Mitutoyo FS-60 microscope and the Z-Scope stage. Without the gear box I get 0.4um travel/step with microsteps of 1/16 full step. I regret adding the gear box and will remove it at some point. If I ever need smaller steps it's a simple matter to add a motorized drive to the Seiwa focus block.

My setup doesn't have much in common with what you're describing but, if you think they'll be helpful, I can take some pics.

The motor voltage rating means that if you apply that much DC voltage to the stationary coils you should see the rated current flow. It has little to do with performance since most modern drivers operate at a much higher voltage and "current limit" based on settings that you've selected. You should be able to operate safely at any voltage that doesn't exceed the maximum rating of the driver. If you do operate at voltage greater than 12v you'll get a higher maximum speed (probably more than needed for stacking) and if the period of time.

Hi Gene,

The controller behavior is a little more complicated than this I believe. There is the inductive voltage is too low you may end up limiting the amount of torque the motor can produce. This is, in part, because you not only have to deliver the rated current but you also have to do it in a very short Ldi/dt effect than must be accommodated by the controller and supply. With motors that have a small inductance you can get a rapid change in motor current that can change too fast for the controller to allow the proper motor current decay sequence in PWM current modes. With some older controller chips you had to set the timing of the decay sequences, with pin selection and sometimes with a resistor/capacitor changes for certain motors & supply voltages. Also, some older controllers have shown some misbehavior with certain motor/supply voltage combos (Ti chips are noted for misbehaving). I also recall someone having problems with higher supply voltages, well within the specification, but things settled down going to a lower voltage.

Another thing to watch out for is motor/controller overheating, this can even happen with small NEMA 11 motors (like the USA THK KR-15) because they have a higher voltage rating which translates to a higher internal resistance, thus higher motor internal I^2R heating. Having the ability to program the current limits under full software control has shown to be very valuable as one can tailor the motor current profile during operation and still retail the desired moving & holding torque.

The newer controllers seem to have a somewhat "automatic" mode which will hopefully eliminate or reduce the motor/supply problems seen with the older controllers, and recently I read where a controller that can sense the motor dynamic and static load situation and adjust the motor current accordingly.

Anyway, hope this helps some.

Best,

Sure. The controller has a lot going on behind the scenes and the little I said probably could have been said better. In the end though I was just trying to present a simple example, in response to the question in the original post, in a simple way.

[Chris S.]

Hello Gene,
Could you please show your solution with the belt-mounting?

Adi,

Though you posed this question to Gene, you might be interested in the timing-belt driven system I use, documented here.

As you can see, in my use, the timing belt connects a stepper motor to a microscope focus block, rather than a drive screw; I suspect that a focus block represents a more fault tolerant case than a drive screw does. This said, for my use, a timing belt works very well.

--Chris S.

[genera]

Hello Gene,

if you think they'll be helpful, I can take some pics.

Yes, please!
BR, ADi

Here you go. Sorry it took so long.

Glued together from about a dozen eBay purchases.

1)



2)



3)



4)

[ray_parkhurst]

Beautifully crafted, rock solid system.

What do you use to drive the X, Y, Z motors?

[mawyatt]

Gene,

Very nice setup

Like the lack of randomness of things and neat overall layout.

What is the XY stage from?

Best & Happy Holidays,

[genera]

Beautifully crafted, rock solid system.

What do you use to drive the X, Y, Z motors?

Thanks Ray, but not really much craft. I drilled holes in three flat plates, the rest I bought.

The drivers are Parker OEM350 with step and direction inputs and programmable micro-stepping.

[genera]

Gene,

. . .

What is the XY stage from?

Best & Happy Holidays,

It was an eBay purchase. I don't remember what it was a part of or any other details. It was made by Danaher Corp.

[ray_parkhurst]

Beautifully crafted, rock solid system.

What do you use to drive the X, Y, Z motors?

Thanks Ray, but not really much craft. I drilled holes in three flat plates, the rest I bought.

The drivers are Parker OEM350 with step and direction inputs and programmable micro-stepping.

Beautifully cobbled then!