Novoflex Castel Micro- stepper controlled

lothman · Post by **lothman** » Sat Sep 29, 2018 5:23 am

Yesterday I saw a new macro rig on the Novoflex booth

https://www.novoflex.de/en/focusing-rac ... ro.en.html

looks fine but 1700.-€ is quite a number.

I also saw the pototype of the Laowa 100mm macro reaching until 1:2
Edit: I meant reaching until 2:1 Laowa 100mm f/2.8 2X Ultra Macro

regards
Lothar
P.S.: I hope it is OK to link to this pic from the Novoflex homepage

Admin edit RJL: fix URL

rjlittlefield · Post by **rjlittlefield** » Sat Sep 29, 2018 7:01 am

Looks interesting. Expensive, but available off the shelf, good specifications.

I'm OK with hot-linking this advertising picture, but I did fix the URL (missing "l" at end), and I made the link from the image more explicit.

--Rik

ray_parkhurst · Post by **ray_parkhurst** » Sat Sep 29, 2018 7:39 am

That is a beautiful linear actuator from Novoflex! Linear rails on both sides with what looks like fairly long contacts, possibly nearly the full length of the carriage. Should be very stable.

Image 7 is very interesting. Looks like they are offering some nice accessories similar to what Robert and Mike are using, though I must say that image looks more like a CAD drawing than a photo...

JKT · Post by **JKT** » Sat Sep 29, 2018 8:54 am

The price was a bit of shock, but then I saw the minimum step size...

ray_parkhurst · Post by **ray_parkhurst** » Sat Sep 29, 2018 9:27 am

JKT wrote:The price was a bit of shock, but then I saw the minimum step size...

Well, any technical marketing guy can do the calculation of 1mm pitch, 400 step motor, and 16 microsteps and come up with that number, but it doesn't mean it's true. There is nothing in that rail that screams sub-micron precision. Maybe it's a 0.7mm or even 0.5mm pitch screw (it does look fine in the pics), so that only 8 microsteps are required, but still the same caveat. Plus it would move very, very slowly.

Lou Jost · Post by **Lou Jost** » Sat Sep 29, 2018 10:18 am

The specs say "smallest repeatable step size" is 0.2um so so I suppose there might be an empirical component to that spec. Nice that it integrates with a dedicated bellows to move either the front or rear standard. Unfortunately I am sure the bellows is also extremely expensive.

mawyatt · Post by **mawyatt** » Sat Sep 29, 2018 1:09 pm

Agree, this looks like a very nice setup, maybe not so expensive considering it's a complete standalone system with some nicely integrated additional components and beautifully detailed.

I suspect the "smallest repeatable step size" comes for 1mm pitch, 400 step motor with 16 micro-steps which produce 0.156 micron steps. This doesn't actually say its the actual rail "position" repeatability tho. With my recent deep dive into stepper motors and controllers I wonder what stepper motor, control algorithm and chip set they are using?

Best,

ray_parkhurst · Post by **ray_parkhurst** » Sat Sep 29, 2018 2:21 pm

mawyatt wrote:Agree, this looks like a very nice setup, maybe not so expensive considering it's a complete standalone system with some nicely integrated additional components and beautifully detailed.

I suspect the "smallest repeatable step size" comes for 1mm pitch, 400 step motor with 16 micro-steps which produce 0.156 micron steps. This doesn't actually say its the actual rail "position" repeatability tho. With my recent deep dive into stepper motors and controllers I wonder what stepper motor, control algorithm and chip set they are using?

Best,

Mike...wouldn't .156um be 32 microsteps? Or do I misunderstand the way "microsteps" divides the step size?

mawyatt · Post by **mawyatt** » Sat Sep 29, 2018 2:48 pm

ray_parkhurst wrote:
mawyatt wrote:Agree, this looks like a very nice setup, maybe not so expensive considering it's a complete standalone system with some nicely integrated additional components and beautifully detailed.

I suspect the "smallest repeatable step size" comes for 1mm pitch, 400 step motor with 16 micro-steps which produce 0.156 micron steps. This doesn't actually say its the actual rail "position" repeatability tho. With my recent deep dive into stepper motors and controllers I wonder what stepper motor, control algorithm and chip set they are using?

Best,
Mike...wouldn't .156um be 32 microsteps? Or do I misunderstand the way "microsteps" divides the step size?

Think it's just screw 1mm pitch, divided by 400 motor steps/rotation, divided by micro step, or 16 micro steps /motor step.

The micro steps divide the motor steps by a fixed integer amount. This is accomplished by high speed Pulse-Width-Modulation of the motor coil currents. The PWM causes the current induced coil magnetic fields to be fractional parts of the normal full step field which causes the permanent magnetic cogged rotor to move in between normal full steps, but as you can see this comes at a reduced holding torque penalty. The really clever part of this technique is allowing the current through the coil to continue to flow in the same direction by momentarily reversing the H bridge causing the coil current to return to the power supply as it decays because of the stored inductive energy (1/2 LI^2). Creating an overall "smoothing" effect on the motor current, and torque and thus motor movement, while reducing the supply current requirement! Clever indeed!!

Best,

ray_parkhurst · Post by **ray_parkhurst** » Sat Sep 29, 2018 3:50 pm

mawyatt wrote:
ray_parkhurst wrote:
mawyatt wrote:Agree, this looks like a very nice setup, maybe not so expensive considering it's a complete standalone system with some nicely integrated additional components and beautifully detailed.

I suspect the "smallest repeatable step size" comes for 1mm pitch, 400 step motor with 16 micro-steps which produce 0.156 micron steps. This doesn't actually say its the actual rail "position" repeatability tho. With my recent deep dive into stepper motors and controllers I wonder what stepper motor, control algorithm and chip set they are using?

Best,
Mike...wouldn't .156um be 32 microsteps? Or do I misunderstand the way "microsteps" divides the step size?
Think it's just screw 1mm pitch, divided by 400 motor steps/rotation, divided by micro step, or 16 micro steps /motor step.

The micro steps divide the motor steps by a fixed integer amount. This is accomplished by high speed Pulse-Width-Modulation of the motor coil currents. The PWM causes the current induced coil magnetic fields to be fractional parts of the normal full step field which causes the permanent magnetic cogged rotor to move in between normal full steps, but as you can see this comes at a reduced holding torque penalty. The really clever part of this technique is allowing the current through the coil to continue to flow in the same direction by momentarily reversing the H bridge causing the coil current to return to the power supply as it decays because of the stored inductive energy (1/2 LI^2). Creating an overall "smoothing" effect on the motor current, and torque and thus motor movement, while reducing the supply current requirement! Clever indeed!!

Best,

I swear I calculated that 5 times over the last few hours and every time I got (1/400)/32=0.156u. I did it twice before I asked the question. Now I calculate it and get half that. What a day.

lothman · Post by **lothman** » Sun Sep 30, 2018 2:04 am

mawyatt wrote: Think it's just screw 1mm pitch, divided by 400 motor steps/rotation, divided by micro step, or 16 micro steps /motor step.

As far as I saw on Photokina the pitch screw is finer than 1mm I would estimate 0,5mm, the nut is just a piece of brass. Everything looks very fine and well designed, but not the screw and the nut. A THK KR railguide is mechanically a league above.

By the way this Laowa lens was demonstrated on a fish tank. Laowa 24mm f/14 2X Macro Probe

mawyatt · Post by **mawyatt** » Sun Sep 30, 2018 6:20 am

lothman wrote: As far as I saw on Photokina the pitch screw is finer than 1mm I would estimate 0,5mm, the nut is just a piece of brass. Everything looks very fine and well designed, but not the screw and the nut. A THK KR railguide is mechanically a league above.

That's a shame for the poor screw and nut design, and would limit the rail performance.

Agree that the THK KR series are a well engineered and build rail.

Best,

ray_parkhurst · Post by **ray_parkhurst** » Sun Sep 30, 2018 7:04 am

lothman wrote: As far as I saw on Photokina the pitch screw is finer than 1mm I would estimate 0,5mm, the nut is just a piece of brass. Everything looks very fine and well designed, but not the screw and the nut. A THK KR railguide is mechanically a league above.

0.5mm pitch will for sure slow the thing way down. My vertical setup is a KR20 with 1mm pitch, and initially had a 400-step motor on it, but replaced it with 200-step because it was impossibly slow to make any significant movements. Great for stacking, but I don't typically need sub-micron steps.

For such an expensive rail I would have expected a pre-loaded ball screw drive, but recently I've picked up some acme screws with "anti-backlash" brass nuts. A typical solution for backlash is what Mike does with rubber band loading, either on-axis or off-axis depending on the problem being solved. The "anti-backlash" nuts are actually duals, one attached and one captured, with a spring between them. This keeps a constant spring force in one direction to reduce backlash. I was going to build my own XY with this system but ended up just integrating the KR15's. I may still experiment just to find out how well the anti-backlash nuts work. One nice thing about the anti-backlash nuts is they get compensated for wear, so no increase in backlash vs use. I would presume this rail uses such an arrangement. There is certainly enough room under the carriage to do this.

Edited to add: the terminology is "anti-backlash" so I changed the above, and here is a link to an example:

https://www.ebay.com/itm/T8-8mm-Anti-ba ... SwiSJbjN-r

mawyatt · Post by **mawyatt** » Sun Sep 30, 2018 9:00 am

Ray,

I hope to be able to get good speed (>1mm/sec) rail performance and simultaneously achieve sub-micron resolution (~0.3um) with 400 step motors and 1mm pitch screw threads (as on the KR20) with very smooth rail performance with minimum vibration impact and no missed microsteps.

These are my goals for the precision stack & stitch setup I'm creating now. The new control algorithms and controllers should allow this I believe, at least that's what I'm working towards.

Best,

ray_parkhurst · Post by **ray_parkhurst** » Sun Sep 30, 2018 9:04 am

mawyatt wrote:Ray,

I hope to be able to get good speed (>1mm/sec) rail performance and simultaneously achieve sub-micron resolution (~0.3um) with 400 step motors and 1mm pitch screw threads (as on the KR20) with very smooth rail performance with minimum vibration impact and no missed microsteps.

These are my goals for the precision stack & stitch setup I'm creating now. The new control algorithms and controllers should allow this I believe, at least that's what I'm working towards.

Best,

Well, 1mm/sec is what I consider impossibly slow. I move my rail +/-100mm fairly often and waiting nearly 2 min would drive me nuts. Guess I am impatient.