Focus loss upon microscope stage movement

[Naphthalene]

Hello again!

Please help me to understand another annoying feature of my microscope.

The focus is lost at some point when I move the stage along the X-axis looking for example at the stage micrometer . When I return the stage to the initial position, the image becomes sharp again. Thus, I really doubt this can be a plain stage drift. Moreover, I have tried the different settings of the coarse focus knob, but with no effect .
Furthermore, this can't be explained by a slope of the stage (the stage not being parallel to the table surface) as when I look at larger slides like tissue sections or blood smears, the focus loss is not progressively increased upon the movement in X-direction. Instead, when I move further I see that at some point the image becomes sharp again.
It may be assumed that these samples are not perfectly flat, possessing the uneven relief. But as I perviously noted, the focus is also lost using the stage micrometer. Also, I do not see any focus loss when I move these slides manually.

Presumably, there might be come defect in the stage rail mechanism (I don't know this thing is properly called) that provides the slide movement in left-right directions.
No such problem is observed upon the movement along the Y-axis.

I have tried to replace the slide holder mechanism with one from my older microscope that had no such problem. Though may be there was some modest improvement, generally the problem peristed.

So maybe you give me some clues why this might happen?

[apochronaut]

In a previous thread of yours, I mentioned that your stay stage might not be perpendicular to the optical train. That could be the cause of your current problem too. When I say stage, I mean includive of the carrier mechanism.
I see that you have used a few techniques to test how level it is. Maybe something in the carrier is binding on the slide, tipping it slightly?

[Zuul]

If I understand your description, there is a point in the travel of the mechanical stage where the focus abruptly shifts. Does it happen at exactly the same place every time you move the mechanical stage? If you lightly rest a finger on the stage and move it past that point, can you feel a bump or other unexpected motion at all?

[BramHuntingNematodes]

Maybe the ways aren't straight? Is there a loose gib? can you jiggle the stage at some points and not others?

[Naphthalene]

Sorry for the late response, I was very badly ill during the last week.

I have investigated the X-axis stage movement mechanism but found no apparent irregularities in it. There is no decent point where the focus gets lost, the problem is observed along the whole length of the slide. However the stage movement is gives and even and smooth feeling with no evident stucking.
I have alco checked again the stage with my previous Amscope T340B, and surprisingly found the similar issue is present there too, but to a lesser degree. My previous conclusion on that was incorrect, sorry.
So all these inexpensive stages share the similar problem.
However, I have found that a a bottom surface of the new holder is less well polished. I'm planning to correct it by grinding the holder on a glass covered with suspension of abrasive alumina powder (I'll use first the rough 240-400 grit powder than switch to 600 grit one), and report if I would get any improvement.

I have also checked again the stage angle relative to the table surface on which the microscope is installed. For that purpose I have calibrated the digital protractor until I was able to achieve a zero drift while the device remains stable.
This is a table surface wich was set as zero

And this image shows the angle of the stage X-axis


While there is indeed a slope present, I'm quite confused why I don't see a focus loss when I move the slide manually after removing the slide holder.
Also, it can't be excluded that the optical plane of the objective is not parallel to the surface of the table.

I wonder if there is some way to adjust the stage slope somehow?

[BramHuntingNematodes]

Is the slide getting listed off of the stage at any point? I have a slightly bent arm on my stage and this has given me some terrible frustrations only for me to notice the slide is slightly lifted, tilted on the stage.

[Naphthalene]

I've noticed that the slide holder movement is less stiff compared to my previous microscope, and it appeared that the holder arms too weakly adjoin to the table. This was observed even before I have polished the holder's bottom surface. I attempted to bend the holder arm downwards, while controlling the flatness with a metal ruler. And after that procedure the movement became less smooth, but got a feeling that focus loss during it became a less prominent. At least, this arm evenness contributed to the problem, so thank you for the advice!

[Naphthalene]

Hello! I'm sorry to bother you again with this silly topic,
but I have finally discovered the root of my problem
Please see the image of the X-axis rail. I was blind by not seeing that there are severe defects in the mechanism.


I have contacted the supplier for the possibility of warranty replacement, but I'm afraid that I could not prove this is not my fault.

I'm considering to purchase the new stage - and this rises a question: are there differences in the stage mounting mechanisms ? I have found several offers on Ebay, but in all cases the mounting specifications are lacking.
My stage is clamped to the stand by four screws, as you can see on the image below. The screws are spaced 55,5 mm relative to the stage's X-axis and about 22 mm on the Y.

Please tell, if you know that other microscope suppliers also use this type of stage mounting

[apochronaut]

It isn't an uncommon way but since the stage is cantilevered , the mount is usually much more substantial than that. When you put out you're casting call for subjects you will have to stipulate: NO OVERWEIGHT PROTISTS!

You are being taken advantage of. How could you be responsible for that? I would raise Cain with them. All they need to do is send you a stage. What a bunch of leeches.

[Naphthalene]

Thank you, apochronaut !
Now I'm feeling more confident that I can demand a free stage replacement.
It was a big mistake to forget stating "I'm not using overweight protists in my experiments" in the complaining mail to the supplier

When you say that the mount is usually more substantial, you mean that additional clamping elements are used?
Would it be possible to use, for example, this Zeiss stage with my microscope?

[hans]

Yes it is hard to imagine any reasonable vendor trying to blame that on the customer -- as if it would be possible to apply enough force to crush the hardened way bearing insert without completely destroying the rest of the microscope!? Clearly a manufacturing defect and the person assembling the stage didn't notice or didn't care enough to throw out the bad insert and get another. If the supplier is not cooperative maybe a claim/chargeback through your credit card company would be appropriate, if possible, then buy from someone else.

[BramHuntingNematodes]

Yes it is hard to imagine any reasonable vendor trying to blame that on the customer -- as if it would be possible to apply enough force to crush the hardened way bearing insert without completely destroying the rest of the microscope!? Clearly a manufacturing defect and the person assembling the stage didn't notice or didn't care enough to throw out the bad insert and get another. If the supplier is not cooperative maybe a claim/chargeback through your credit card company would be appropriate, if possible, then buy from someone else.

Yeah uh holy cow this is the textbook example of what warranties are for if you can't get a claim for this then no one can get a warranty claim for anything

[microscoperecovery]

Hi there, I am new to the forum. I saw this post and it is very familiar to me. I am a microscope repair technician in the US.
There may be a solution to this problem without switching the stage. The way material that is used on these microscopes is essentially a drill rod. If you can remove the retaining screw and slide the rod out enough to measure it then a replacement can be found on amazon (example linked)

https://www.amazon.com/uxcell-Lathe-Rou ... 915&sr=8-3

I have taken stages like this apart before. It isn't too difficult to slide one rail out and slide it back in again. As long as you have two rails on one side they will hold the bearings in place.

[Naphthalene]

Thank you so much for your support hans, BramHuntingNematodes and especially microscoperecovery!

There may be a solution to this problem without switching the stage

Thank you for the advice, most probably I will try to purchase the rods soon and try to replace them. In the past people here often said "A true man must be able to repair everything himself"
Please tell how the metal rods are bound to the rails? Is this a superglue or something else?

as if it would be possible to apply enough force to crush the hardened way bearing insert

There are two difficulties in proving anything to the manager.
One is that managers (not only the chinese) often suffer from "insufficient memory disease". That means if you write too many words, the manager will miss the idea.

The other is they often pretend they do not understand you or just play fools (I also do NOT mean that only chinese use it, and there are many nice people in China who don't).
But in this case I have the combo of two, 'cause the last response from the supplier was "Still lose the focus view? can you adjust some steps of the rails?" (and nothing more)

EDIT

If the supplier is not cooperative maybe a claim/chargeback through your credit card

The microscope was purchased almost a year ago, so I can not demand a refund

[hans]

Please tell how the metal rods are bound to the rails? Is this a superglue or something else?

Are you sure there is anything holding them down other than the retaining screw at the end which keeps them from sliding out axially? I have a similar stage disassembled right now and there are actually not even any retaining screws, just a small hole that a bent end of the bearing rod hooks into. The only thing keeping the rods in the channels is the clamping force on the bearing. The balls ride in between the four rods and force them at roughly 45 degree angles outward into the corners of the shallow, rectangular channels on either side of the bearing. Photos may be helpful:
rods laying in channel
side view of the channel with rods removed

[microscoperecovery]

There isn't any adhesive holding the rods in place, just the retaining screw. If you don't mind me asking what is the make/model of the microscope?

[Naphthalene]

Are you sure there is anything holding them down other than the retaining screw at the end which keeps them from sliding out axially

I still haven't checked this, I'm scared to be left with no stage as the reassembly may be not trivial with my skills. I want to complete a couple of projects and gather as much info as possible on this topic before ventruing on disassembling the stage.

The only thing keeping the rods in the channels is the clamping force on the bearing

If I correctly understand that, the rods will fall off as soon as I detach the rails? Please tell, in case the retaining screw is not involved in clamping the rods - how this mechanism is reassembled when one needs to insert the ball back while holding (four?) rods in their positions?

If you don't mind me asking what is the make/model of the microscope?

Sure thing - it is LF-302 from Leader Precision Insruments, http://www.metrology.cc/chanpinok.asp?eid=14&PicID=82
I'm sure it is a replica of some western discontinued model, but couldn't find which one

[hans]

Please tell, in case the retaining screw is not involved in clamping the rods - how this mechanism is reassembled when one needs to insert the ball back while holding (four?) rods in their positions?

Sorry, on yours it does look like the screws at the ends should hold the rods in place during assembly. What I meant was, because the clamping force pushes the rods into the corners of the channel, there isn't necessarily anything else, like adhesive, holding them in the middle.

The lack of retaining screws on mine was not much of a problem. The rods are light enough that the stickiness of the grease held them pretty well, even when turned upside down. So I first stuck all the rods in place with a little grease, then stacked up each axis with the corresponding ways level so there was not too much tendency for stuff to roll/slide out of place. I think as long as you do it in a place where the balls cannot easily be lost in case of an accident there is not too much to go wrong. On one axis of mine the balls snap into place in the plastic cages and cannot easily fall out. The plastic cages on the other axis have larger holes and balls freely fall out which makes assembly more tedious. Not sure why the difference but both stages I took apart were like that.

If you replace rods it will probably be necessary to realign the gear racks that move the stage to get smooth operation without backlash. For me that was the most time-consuming part.

[Naphthalene]

hans, thank you for the detailed explanation! The rail grease is behind the trick, I may take advantage of that.