my positioning stack: X, Y, yaw, pitch

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JohnDownie
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Joined: Tue Oct 18, 2011 6:57 am

Post by JohnDownie »

Prediction:

These will sell out today.

I just got mine.

The stage stack looks to have been used very little, if at all - the bag was sealed. Almost no doinks to the anodizing, no visible wear on tracks, fresh looking grease that isn’t fully distributed, paper stickers that look perfect.

Some crude, empirical testing indicates that the center of rotation for the bottom goniometer is near the top of the lower of the X axes, maybe 45mm-ish above the surface of the upper goniometer.

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Time to get the allen keys.

Update:

The bolts are tight and I need to get some really good hex keys - I am not going to risk any damage.

Just ordered a set of Bondhus keys.

Two units remain...
Last edited by JohnDownie on Tue Jan 07, 2020 12:11 am, edited 2 times in total.

JohnDownie
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Post by JohnDownie »

Chris S. wrote: 5) Vertical stage on bottom. (Optional, as I doubt this stage has enough travel to be sufficient in most rigs; perhaps include this stage for fine vertical positioning, but add some other vertical stage for coarse positioning and added travel. It is imperative that this axis of adjustment be addressed, whether or not this component is part of the solution.)

--Chris S.
Chris,

What do you recommend for the main Z axis stage? I see what appear to be Chinese copies of Newport Fast stages that seem interesting.

Chris S.
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Post by Chris S. »

JohnDownie wrote:What do you recommend for the main Z axis stage?
John,

The subject stage I detailed a decade ago is still what I use, and it works very well; a part-by-part description is here: The Bratcam. My Z-axis is a microscope focus block adjustably mounted on a post. There is a right-angle bracket on the focus block, which provides a shelf on which are mounted the other elements of the subject stage.

On the upside, a microscope focus block generally provides about 30mm of coaxial fine and coarse movement, while the post provides vastly more coarse adjustment--essentially as much as you want. I use all three of these adjustments with almost every shoot. As an additional bonus, I can rotate the subject stage around the pole, effectively extending the reach of my left-right actuator.

On the downside, an Olympus BHMJ focus block can be hard to source, and a post of the right diameter may have to be custom made. (Balanced against this, I have an extra BHMJ focus block that I could probably share, and my fabricator has made posts to fit these blocks at modest prices.)

I think many other focus blocks could be made to work, if cut out of a microscope stand. This can be done with a common hacksaw. (Or contact me--I have a metal-cutting saw specifically chosen for this job.) I suspect that many such cut-out microscope focus blocks could be modified to mount on off-the-shelf posts.

As an alternative to a mounting post, I've been wondering about using a solidly-built linear actuator for the job of holding a microscope focus block that is holding a subject stage. As I'm familiar with Velmex's linear actuators, I naturally consider them for this job. The Velmex BiSlides, if obtainable in a short version, would be ideal (though these are expensive new and uncommon on eBay). Velmex UniSlides, while less robust for vertical orientation, might also serve well--especially if used in pairs, with one of the pair having its drive screw removed.

Another alternative to a post might be a very high quality lab jack. While many lab jacks are jiggly, the best are quite solid. I have a Newport 281 Lab Jack that holds 300 lbs, has 76mm vertical travel, and is rock solid--never a quiver. On the downside, it's big, expensive, and the knob takes moderate torque to turn. This must be a design requirement, as I've taken it completely apart, cleaned it scrupulously to remove old, hardened grease, and put it back together. It's a fine piece of gear; if I integrate it, I'll add a stepper motor to the adjustment knob to make raising and lowering it easy. If I sell it, I'll advise the buyer to do the same.

As much as I appreciate my current Z-stage (I do like it and recommend it), I've spent some time considering improvements. If I do undertake improvements, I think I'll keep the BMHJ focus block, but try mounting it to a Velmex linear stage or perhaps the lab jack. If so, I'd motorize the Velmex stage or labjack. If I undertake such a project, I'll likely also increase my left-right movement with an additional linear stage--longer then my current one. This longer stage should be more coarse than the current fine one, for quicker movement across the greater range.

In such a project, I'd probably add stepper motor control to as many movements as practicable. Even though my current subject stage works very well, I find appealing the thought of moving my subject smoothly, precisely, quickly, and for long distances, with joystick, lever, and pushbutton control.

Sorry for the digression! Please consider the subject stage on the current Bratcam as established technology. My speculations beyond this may or may not work.

Cheers,

--Chris S.

--Fixed typos
Last edited by Chris S. on Sat Jan 18, 2020 5:30 am, edited 1 time in total.

ray_parkhurst
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Post by ray_parkhurst »

I received my 60x60mm component stack today from Korea. It was sealed in a bag and in very good condition, seems barely used. Here are my observations:

Both goniometers seem reasonably smooth and not over-tight. Each was limited in range due to the lock screw, which after removing allowed full movement. Both have a small amount of backlash but not excessive. This is my first 60x60mm matched pair so I am glad to have it.

Rotation stage worked as expected. Lock screws make adjustments difficult since they are in the way of the adjuster knobs, but after removing them it was easier to turn without interference. Movement was a little stiff, but after a full revolution it was a bit smoother. Only a small amount of backlash in the adjuster screw. Very nice component, glad to have it, especially in 60x60mm.

Micrometer sliding table is limited also by the lock screws. After removing, the table has full motion, with 15mm total adjust range. Micrometer accurately positioned so 7.5mm readout is center of range. Smooth operation, very nice table.

Rack/pinion sliding table is a bit stiff, but large knobs on both sides make it fairly easy to use. Good 40mm adjust range with vernier.

Z-stage has wide-spaced bearings, so seems quite stable and should handle heavy loads. Micrometer adjust would not go to "0", needed to remove the limit screw, but would still not go quite to 0 until I re-positioned the micrometer a bit. Has a little less than 12mm of adjust range. Better quality than the typical Z-stage available from China.

Overall the components seem like a very good deal. I personally was interested mostly in the 360-deg rotation table, but I'm glad to now have the 60mm matched goniometers, so it was a good purchase.

Chris S.
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Post by Chris S. »

Mine arrived as well. As in John and Ray's reports, my product-containing bag was sealed (I think by the vendor, not the original supplier), and wear is very minimal, requiring careful scrutiny to detect at all. All components seem well-designed and machined.

On the downside, some of my components move with too much difficulty for my taste. I suspect that whatever grease was used has hardened. By comparison, similar components in my current subject stage move with silky smoothness and little manual effort.

In this assemblage, the rotation stage I received can be moved only a few degrees in either direction, and then only with considerable pressure on the knobs. In this condition, I consider it unusable.

My specimen of the Z-stage works pretty well, though it is a bit stiffer to operate than similar Z-stages I've had in hand. And as Ray reported, travel is only about 1/2 inch. While this amount of travel is standard for this type of stage, it is very limiting. For practical use, an additional, coarse-adjustment, Z-stage with greater range should be added.

My specimen of the rack-and-pinion transverse stage is a bit too stiff for convenient use. Also, it includes a brake lever, but full release of this lever seems to be blocked by the adapter plate fastened atop this stage. My guess is that this brake lever would work more effectively with intelligent rearrangement of the component stack.

The micrometer transverse stage is perfect.

The goniometers are workable, but stiffer than my current pair.

My sense: If I take every one of these components apart, remove the adapter plates that connect them (and that in some cases perhaps constrain their movement), then clean out the old grease, re-lube, and reassemble, it's a reasonable bet that each component would end up working with silky smoothness as if new. I've done this successfully a few times, and found it to work well.

Question is, do I want to add this work to my project list? Personal preferences for my project list involve not just money saved, but lessons enjoyably learned. Would I learn enough from rehabilitating this component stack to make the effort worth my time? Since I've rebuilt similar components, and learned from the experience, my answer is "no." I'm disinclined to undertake this project, which to me it seems repetitive. But for a forum member who enjoys DIY projects, and for whom this is new territory replete with learning, the answer may differ.

I'm thinking of returning the product instead. In new condition and properly re-arranged, this component stack would cost far more than its $300 price. But I'd guess it will take me two solid work days (I'm a slow-working amateur) to bring these components into as-new condition.

My version of a proper eBay listing for this component stack would be: "Stack of high-quality components for micro-adjustment in most axes of translation/rotation; signs of use verge on undetectable. However, old grease has hardened in some components--buyer should expect to disassemble, clean, and re-lube. Also, assembly order of component stack is questionable for most uses--buyer should have requisite knowledge and time to re-order component stack and perform needed maintenance."

--Chris S.

viktor j nilsson
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Location: Lund, Sweden

Post by viktor j nilsson »

Chris S. wrote: On the downside, some of my components move with too much difficulty for my taste. I suspect that whatever grease was used has hardened. By comparison, similar components in my current subject stage move with silky smoothness and little manual effort.
--Chris S.
A year ago, I picked up a matched goniometer pair from the same seller (dy-global) for $99 (free shipping). They were branded Toptek.

My experience was similar to Chris S. in that they were very stiff to operate out of the box, either from dried up grease or from using a too heavy type of grease (I suspect the latter).

After diassembling and cleaning (easy) and re-greasing with a lighter grease (I think I used a standard litium grease), they work very well. Although I might at some point change to an even lighter grease.

Anyway, the thick grease seems to be a common problem with these parts. Still a good seller offering items that have been hard to find at decent prices lately.

Troels
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Post by Troels »

Back in Oct. 2019 I bought a set probably similar to Viktors:
TOPTEK X,Y Goniometer Tilting Stage Used 40X40X36 mm.

They were also very dificult to adjust. But I discovered that the row of small allan screws on the sides (flush with the surface) were ment for adjusting the tension. After loosening all of them the changing of positions became very smooth. As if stiffened grease had been changed for soft.

In addition the units were mounted in the wrong way: The unit with short turning radius was at he bottom while the one with long turning radius was at top. Fortunately rather easy to fix.

Apart form this they seem to be well built and work as intended. For less than $ 100 I consider it a good purchase.
Troels Holm, biologist (retired), environmentalist, amateur photographer.
Visit my Flickr albums

ray_parkhurst
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Post by ray_parkhurst »

Chris S. wrote:My sense: If I take every one of these components apart, remove the adapter plates that connect them (and that in some cases perhaps constrain their movement), then clean out the old grease, re-lube, and reassemble, it's a reasonable bet that each component would end up working with silky smoothness as if new. I've done this successfully a few times, and found it to work well.
Hmm, it seems you got a lemon, and it may not be the same configuration I received either, since mine have no adapter plates.

viktor j nilsson
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Post by viktor j nilsson »

Troels wrote:Back in Oct. 2019 I bought a set probably similar to Viktors:
TOPTEK X,Y Goniometer Tilting Stage Used 40X40X36 mm.

They were also very dificult to adjust. But I discovered that the row of small allan screws on the sides (flush with the surface) were ment for adjusting the tension. After loosening all of them the changing of positions became very smooth. As if stiffened grease had been changed for soft.
Troels, I do think we have the same 40x40mm Toptek t2-418-A4-R(Y) goniometers.

I'm very glad you pointed out the adjustment screws along the side (tiny recessed screw heads along the curved intersection between the upper and lower half). I had not thought of that at all. Changing to a lighter grease helped make my pair acceptable, but loosening the adjustment screws made a huge difference. My pair is now very smooth and easy to turn. Thank you!

Worth checking on the MMT goniometers as well.

Nikotiana
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Re: my positioning stack: X, Y, yaw, pitch

Post by Nikotiana »

Hi, I am new to the forum and this is my first post here. I would need advice regarding a mounting problem of a xy stage.
rjlittlefield wrote: Starting from the bottom, this consists of:

1. Block of wood with Arca rails screwed to it on several faces
I bought on Aliexpress a xyzr stage 60x60mm but did not anticipate how to fix it on my support, a Wemacro vertical stand with 1/4 inch holes.

Here is the picture of the bottom plate seen from below:
Image

I saw here the solution with a block of wood, but I am not a handyman at all.

In the Wemacro site, you can see a xy platform with a bottom plate pierced with a 1/4 inch threaded hole, what I would like to get, but it appears to be available nowhere.

So if someone has advice or a solution to give me, I would be very grateful!

elimoss
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Post by elimoss »

I have same problem where I would like to find some base plates or other mechanism for fastening 40mmx40mm and 60mmx60mm stages to breadboard. Any ideas other than the wood block (which is great idea, thanks!)?

JohnDownie
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Joined: Tue Oct 18, 2011 6:57 am

6 axis stack

Post by JohnDownie »

I ended up ordering a copy of a Newport fast lab jack with a stepper plus manual override.

The order follows Chris S’s layout description.

Image

The stack includes coarse and fine stages in X and Z.

Chris S.
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Re: 6 axis stack

Post by Chris S. »

JohnDownie wrote:I ended up ordering a copy of a Newport fast lab jack with a stepper plus manual override.

The order follows Chris S’s layout description.

The stack includes coarse and fine stages in X and Z.
John,

Your implementation of this subject stage looks great! :D

In particular, your inclusion of a high-quality Newport lab jack, with stepper motor movement plus manual override, seems very apt, and is an approach little discussed in our community. Bravo!

As always, one can only go so far in the planning process, and the using process may suggest alterations that may work better. My sense is that you have done very well in thinking through your assembly. Once you have time to use your rig extensively, you may be able to suggest even better enhancements. I look forward to this.

--Chris S.

JohnDownie
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Joined: Tue Oct 18, 2011 6:57 am

Re: 6 axis stack

Post by JohnDownie »

Chris S. wrote: John,

Your implementation of this subject stage looks great! :D

In particular, your inclusion of a high-quality Newport lab jack, with stepper motor movement plus manual override, seems very apt, and is an approach little discussed in our community. Bravo!

As always, one can only go so far in the planning process, and the using process may suggest alterations that may work better. My sense is that you have done very well in thinking through your assembly. Once you have time to use your rig extensively, you may be able to suggest even better enhancements. I look forward to this.

--Chris S.
Thanks so much, Chris.

This is such an informative and inspiring forum with none of the typical forum stuff.

Just to be clear, the lab jack is from PDV, not Newport.

https://www.pdvcn.com/

They make(?) various stages, but also sell Mitutoyo, Nikon, Olympus and Sanfeng microscope objectives. Sanfeng hasn’t come up on the forum before, as far as I can tell. No hits on eBay, either, though they might be sold under other labels.

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