Advice with motorized rail

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Irisoratoria
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Advice with motorized rail

Post by Irisoratoria »

Hello everyone.

I'm new to this forum. I have experience in macro and microphotography world but automated stacking rails (and stacking macro photography too) are a mistery to me, I need advice. I don't know if this theme has been discussed before (if did, apologises), but I didn't find it. I would like to do stacks between 10x to 25x magnifications and i want to buy a motorized rail. My choices (I understand that both kits do the same and don't need any other accessory. Of course I've lenses, bellows, etc):

http://www.mjkzz.com/product-page/preci ... -bluetooth

and http://www.wemacro.com/wp-content/uploa ... uct-_s.jpg

It seems that both are good but could'nt find any review about Precision Focus stacking kit SR-90P Bluetooth.

Apparently Mjkzz model is more accurate. The prices, shippment included, are similar. Can someone advise me of the two devices? and for what reason?

Thank you very much in advance.

Irisoratoria
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Post by Irisoratoria »

Is there anyone who can help me decide? I'm lost. :roll:

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Post by ChrisR »

I doubt anyone has more than one make, other than the makers of the rails!

Some are represented here so you may get some answers from them.
Another one to look at is Cognisys Stackshot.
Chris R

Irisoratoria
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Post by Irisoratoria »

Thank you very much for your answer Chris.

My budget doesn't reach to the Cognysis.

There's some reviews about Wemacro rail, very few about the Precision SR-90 rail (almost nothing). My doubt is which one is most adequate to me (cause the prices seem similar). I suppose both are good items (both are China products, not clear in the sites), but there's some differences (construction, accuracy, etc.) that could be important.

I'll continue searching.

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Post by mawyatt »

ChrisR wrote:I doubt anyone has more than one make, other than the makers of the rails!

Some are represented here so you may get some answers from them.
Another one to look at is Cognisys Stackshot.
Chris, Iris,

I have all three, Cognisys Stackshot, WeMacro and MKJZZ, as well as the modified surplus THK KR20 type with MKJZZ adapter kit. I've had the Stackshot for quite some time now, so an updated version is highly likely. It has served me well, without any issues, a testament to the design and quality of build. I think Johan over at Extreme Microphotography has all three rails as well.

I would say the Stackshot is the most complete system of the bunch and can be directly controlled from Zerene. Very well done IMO. Both WeMacro and MKJZZ are both good alternatives to Stackshot and lower cost. I can't say which is "better", both are very good IMO. I've only used the WeMacro up to now, and mostly with the Stackshot controller since it interfaces with Zerene. I made an adapter to allow the Stackshot controller to control the WeMacro rail, and the two work very nicely together. Zerene allows you to put in the screw pitch parameters and the effective number of motor steps (I'm using 400), so you get accurate information about step size, position and step range and don't have to fiddle with the math in your head because you are using a non-standard rail. So hats off to the Stackshot Controller and Zerene for working together and not having to fiddle with things!!

So why do I have these other rails? Well I was seeing some strange effects in the chip images I take and thought it was due to the focus rail. So I purchased the WeMacro system to try it out, well it works very well indeed but has the same issues as the Stackshot rail. Then I went on a fact finding search for the source of the problem, which I found as rail micro-wobble as it moves.

I figured out a solution that works well utilizing an off-axis rail loading utilizing a bunch of rubber bands. This works equally well with the Stackshot and WeMacro rails, and suspect will also with the MKJZZ rail (when I can get chance to use it).

The MKJZZ rail came by way of Peter's stitching setup (why I purchased it), which I am seriously delinquent on getting up and running!! Other priorities have surfaced and prevented me from moving forward with the stitching effort.

Lastly the surplus THK KR20 rails are a beautifully engineered rail that cost big $ new. Sometimes you can spot them on eBay for under $200 USD. MKJZZ has a kit that supplies motor & adapter, and a couple of small brackets that allow the rail to be mounted onto the standard "T Guide" system. You still need a controller though. These THK rails have ball bearings in the guide rollers and screw "nut" and are build extremely well, I suspect they will perform very well at the micron level, which is why I have them. Yes, another project well behind schedule!

Anyway, I hope this helps.

Best,

Mike

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Post by Irisoratoria »

Dear Mawyatt, thank you for your answer. Really useful information.


I can't afford Stackshot (unfortunately). I need something ready to start to take pictures without spending a fortune. My aspirations are over 20x. Do you think wemacro or Sr_90 could do it without many issues (as backlash, wobble, etc.?).

Thanks.

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Post by ray_parkhurst »

mawyatt wrote:...
So why do I have these other rails? Well I was seeing some strange effects in the chip images I take and thought it was due to the focus rail. So I purchased the WeMacro system to try it out, well it works very well indeed but has the same issues as the Stackshot rail. Then I went on a fact finding search for the source of the problem, which I found as rail micro-wobble as it moves....
I had this problem to various extent with all the gear-based rails I've tried, which is why I was so intrigued by the voice coil rail. It doesn't have this problem at all.
Last edited by ray_parkhurst on Thu May 04, 2017 7:08 am, edited 1 time in total.

Irisoratoria
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Post by Irisoratoria »

ray_parkhurst wrote:
mawyatt wrote:
ChrisR wrote:...
So why do I have these other rails? Well I was seeing some strange effects in the chip images I take and thought it was due to the focus rail. So I purchased the WeMacro system to try it out, well it works very well indeed but has the same issues as the Stackshot rail. Then I went on a fact finding search for the source of the problem, which I found as rail micro-wobble as it moves....
I had this problem to various extent with all the gear-based rails I've tried, which is why I was so intrigued by the voice coil rail. It doesn't have this problem at all.

I suppose this is a big problem with high magnification. Over 20x is a real issue?

mawyatt
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Post by mawyatt »

ray_parkhurst wrote:
mawyatt wrote:...
So why do I have these other rails? Well I was seeing some strange effects in the chip images I take and thought it was due to the focus rail. So I purchased the WeMacro system to try it out, well it works very well indeed but has the same issues as the Stackshot rail. Then I went on a fact finding search for the source of the problem, which I found as rail micro-wobble as it moves....
I had this problem to various extent with all the gear-based rails I've tried, which is why I was so intrigued by the voice coil rail. It doesn't have this problem at all.
Ray,

Agree, the Voice Coil would be a good solution for high magnification because of short throw requirements. One idea I've been tossing around is putting the Voice Coil on a conventional stacking rail, this allows large throw stacks and short throw high magnification stacks from the same fixture, would also allow easier initial setup for the subject getting into position along the optical axis.

I'm hoping the THK KR20 will show considerable improvement wrt the micro wobble, when I can get some time and a bracket to mate it to my Thor sliding clamp I'll give this a try. I'll make an adapter cable to run the THK KR20 directly from Zerene thru the Stackshot controller.

I believe these THK rails were used in semiconductor processing and thus very precise. If you can grab one off eBay I think you will agree they are well designed and very sturdy. The bearings are beautifully smooth and precise, and with a 1mm pitch screw and 400 step motor the potential for some micron level stable precise stepping may surface for high magnification stacking.

Best,

Mike

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rails

Post by ohdeeremee »

and take a look at Johan's site under the Equipment/macro Stages
http://extreme-macro.co.uk/
George

mawyatt
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Post by mawyatt »

Irisoratoria wrote:Dear Mawyatt, thank you for your answer. Really useful information.


I can't afford Stackshot (unfortunately). I need something ready to start to take pictures without spending a fortune. My aspirations are over 20x. Do you think wemacro or Sr_90 could do it without many issues (as backlash, wobble, etc.?).

Thanks.
Iris,

20X is a very large magnification and any subtle effects from rail will show. The WeMacro and SR-90 are good rails, and with off axis loading might be up to the task, but honestly I don't know since I haven't done much 20X work yet.

One advantage of conventional stacking with these rails is repeatability isn't a big issue as you usually run thru the stack once, if you need to rerun then you might require resetting the starting point. Another advantage is that having absolutely uniform stacking steps isn't required unless the steps get so far out that you exceed your DoF and you will see focus banding in the final rendered image.

One thing I have found is that operating near the motor end or screw bearing end sometimes produces slightly better results. I suspect this is because the stage is slightly more secure at the ends of the rail, rather than towards the middle where there is no support for the screw.

Best,

Mike

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Post by ray_parkhurst »

mawyatt wrote: Agree, the Voice Coil would be a good solution for high magnification because of short throw requirements. One idea I've been tossing around is putting the Voice Coil on a conventional stacking rail, this allows large throw stacks and short throw high magnification stacks from the same fixture, would also allow easier initial setup for the subject getting into position along the optical axis....
Take a look at the pic I showed of my setup for testing the voice coil rail...I did exactly this. It is also how I did the displacement measurements of the voice coil rail, ie by offsetting it by the known step size of my vertical stepper.

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Post by ChrisR »

Someone does have several, good!

It would be worth seriously looking at microscope focus blocks if much of your work will be 10x and up, they're much better. You can leave the camera alone and move the subject - the distances are small so the lighting can be stationary. You can drive the rail from a stepper motor - either one of the mentioned systems, or one of the free applications on the net.

Off the top of my head, search for "stepduino".
Chris R

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Post by mawyatt »

ray_parkhurst wrote:
mawyatt wrote: Agree, the Voice Coil would be a good solution for high magnification because of short throw requirements. One idea I've been tossing around is putting the Voice Coil on a conventional stacking rail, this allows large throw stacks and short throw high magnification stacks from the same fixture, would also allow easier initial setup for the subject getting into position along the optical axis....
Take a look at the pic I showed of my setup for testing the voice coil rail...I did exactly this. It is also how I did the displacement measurements of the voice coil rail, ie by offsetting it by the known step size of my vertical stepper.
Yes I see. Good work!! So you could move the subject stage with the voice coil on it and the lens/camera was fixed? Actually if the subject voice coil stage is fixed and the lens/camera is on a precision focus rail, this is even better because you can use the setup with the subject fixed for long stacks and move the subject with the voice coil for short stacks. Either way seems like a good setup for covering a wide range of stacking options.

This is probably where the THK rails will show their value with precise repeated micron level performance.

Best,

Mike

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Post by lothman »

I went for a THK rail, but not the small KR20 but the bigger KR26.

Peter (mjkzz) provides a KR26 conversion Kit with all you need:
http://www.mjkzz.com/product-page/thk-k ... ersion-kit

He also provides the control software for free :-) what lets you choose pitch, stepping width, number of frames, settle time, triggers camera, start and end point...

The THK rails are not only much stiffer, have more precise guides for the block, they also have a ball screw. This has no backlash and low friction, so ideal for constant small steps. You can find the KR26 wit a 2mm pitch what will allow steps of about 0,5 µm (Peter correct me) with fine stepping mode.

So with a used THK Rail in good shape (100-250$) and the conversion kit for 96$ you get a rail solution which is far superior (IMHO as a mechanical engineer) than all the other stuff around.


P.S.: what might occur, the low friction THK rails with ball srews are no longer self locking, so on a vertical setup the camera might slide down when the stepper is powered off.

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