I wondered if I should lightly grease the two guide rods too - but perhaps they're designed for "dry" use. If not, is it OK to use Mannol for those too?Thanks.
Macro rail guid rods - lubrication
Moderators: rjlittlefield, ChrisR, Chris S., Pau
Macro rail guid rods - lubrication
I've been maintaining my WeMacro rail and adjusting the pre-loading in an attempt to remove occasional small lateral movements that recently cropped up when stepping (various distances). I lightly greased the central thread (pinion) with a generic bearing grease, Mannol 8098. That improved things a lot, but I still get the odd "hiccup" at various positions along the rail. It's a very small lateral twitch that doesn't spoil any stacks, but it's large enough to inflame my OCD - so it has to go
I wondered if I should lightly grease the two guide rods too - but perhaps they're designed for "dry" use. If not, is it OK to use Mannol for those too?Thanks.
I wondered if I should lightly grease the two guide rods too - but perhaps they're designed for "dry" use. If not, is it OK to use Mannol for those too?Thanks.
Beats,
I've seen this in all the rails except the THK. Think some is due to a slight "stiction" which will cock the rail slightly then release giving the "twitch". I would think that a light oil/grease on the guides might help, but I never tried it.
Another source of repeated "twitching" (meaning having some systematic repeat rather than purely random), was related to the screw thread slightly binding and releasing.
The Off Axis Loading Technique I came up with awhile back solved both problems as well as rail backlash. The best location originally I thought was normal to the screw thread face, and that's where I placed the rubber band load, turned out that was the best place as I tried other locations.
I cant remember the exact angle, but think it was something like 30 degrees.
Best,
I've seen this in all the rails except the THK. Think some is due to a slight "stiction" which will cock the rail slightly then release giving the "twitch". I would think that a light oil/grease on the guides might help, but I never tried it.
Another source of repeated "twitching" (meaning having some systematic repeat rather than purely random), was related to the screw thread slightly binding and releasing.
The Off Axis Loading Technique I came up with awhile back solved both problems as well as rail backlash. The best location originally I thought was normal to the screw thread face, and that's where I placed the rubber band load, turned out that was the best place as I tried other locations.
I cant remember the exact angle, but think it was something like 30 degrees.
Best,
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike
~Mike
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rjlittlefield
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I would not expect lubricating the guides to completely solve your problem. The reason is that the "twitch" happens when the rail hangs up a little more on one side than on the other, especially when it switches from more on the left to more on the right. Lubricating the guides may reduce the absolute amount of drag, but I doubt that it will eliminate the differences that cause the twitching.
I would try first the off-axis loading approach.
If that's not enough, then you can try lubrication, but in that case I would touch base with the manufacturer to see if there are any concerns about exactly what type of lubricant to use. I once lubed a microscope fine focus shaft with oil. It was great at first, then got progressively stiffer until it completely locked up. Turned out that the plastic bushing material was absorbing the oil and gradually swelling. I eventually got the thing back to working well again, but it required shaving off a thin layer of bushing to restore proper fit. Not the sort of experience that you'd like to repeat.
--Rik
I would try first the off-axis loading approach.
If that's not enough, then you can try lubrication, but in that case I would touch base with the manufacturer to see if there are any concerns about exactly what type of lubricant to use. I once lubed a microscope fine focus shaft with oil. It was great at first, then got progressively stiffer until it completely locked up. Turned out that the plastic bushing material was absorbing the oil and gradually swelling. I eventually got the thing back to working well again, but it required shaving off a thin layer of bushing to restore proper fit. Not the sort of experience that you'd like to repeat.
--Rik
Thanks both.
Rik: yes, that's exactly what I was worried about, things getting gummed up. I've added a couple of rubber bands and it's *mostly* fixed - but still does the odd twitch. I think I just need to temper my OCD really. The main issue is that after a "twitch", the FoV takes 2-3 secs to drift back to it's original alignment. It can be as much as a 5-pixel shift at 20x but that's a rare worst case (4.5 micron pixels). Alignment is no problem of course, and the drift back is slow enough to not cause motion blur for most stacks - but might blur when I'm doing longer exposures at 50x (up to 0.5s). This means I need a longer settle time for all images in the stack just to allow for the 1 or 2 in a hundred that twitch. At 50x, I often end up with 500+ steps in the stack too, so it is a bit of a pain time-wise, especially if imaging wilt-prone plant parts.
I have some dry PTFE lubricant (wet when applied), but that has gummed other stuff up before, so it's definitely not suitable IMO.
I'll check with William before taking that lube step, but meanwhile it looks like there are sweet spots along the rail where it happens least, if at all. I'll spend some time to find some consistently good regions - if there are any.
Rik: yes, that's exactly what I was worried about, things getting gummed up. I've added a couple of rubber bands and it's *mostly* fixed - but still does the odd twitch. I think I just need to temper my OCD really. The main issue is that after a "twitch", the FoV takes 2-3 secs to drift back to it's original alignment. It can be as much as a 5-pixel shift at 20x but that's a rare worst case (4.5 micron pixels). Alignment is no problem of course, and the drift back is slow enough to not cause motion blur for most stacks - but might blur when I'm doing longer exposures at 50x (up to 0.5s). This means I need a longer settle time for all images in the stack just to allow for the 1 or 2 in a hundred that twitch. At 50x, I often end up with 500+ steps in the stack too, so it is a bit of a pain time-wise, especially if imaging wilt-prone plant parts.
I have some dry PTFE lubricant (wet when applied), but that has gummed other stuff up before, so it's definitely not suitable IMO.
I'll check with William before taking that lube step, but meanwhile it looks like there are sweet spots along the rail where it happens least, if at all. I'll spend some time to find some consistently good regions - if there are any.
Just a thought, if sand or some other hard substance happened to get onto the threads it could get between the nut and thread face and cause a jump or twitch. The threads are exposed and greased, so basically a magnet for all kinds of stuff.
Best,
Best,
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike
~Mike
Yes, my first thought and hence the bout of "maintenance". I do keep the rig covered when not in use though and it all looked pretty clean. Just greasing the pinion and re-jigging the pre-loading seems to have fixed 99% of the glitches, so I'm reasonably content now.mawyatt wrote:Just a thought, if sand or some other hard substance happened to get onto the threads it could get between the nut and thread face and cause a jump or twitch. The threads are exposed and greased, so basically a magnet for all kinds of stuff.