Granite Surface Plate

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ray_parkhurst
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Post by ray_parkhurst »

Lou Jost wrote:In my vertical set-ups I now mount the front of the lens onto the moving stage, so the front element or objective is immobilized relative to the subject (which rests directly on the granite base).
Sounds like an excellent way to tightly-couple the two. Is the camera rigid-mounted?

Chris S.
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Post by Chris S. »

Deanimator wrote:I'm thinking that a combination of 40 series profile on top of a 5/8" steel plate, on top of a surface plate on top of my pipe table should be enough. If not, the only alternative is to move.
My guess is that it will be enough, if you place a correct arrangement of Sorbothane under your steel, on top of your pipe table. The goal is to let the world vibrate under your Sorbothane, let the Sorbothan dissipate these vibrations by changing them to heat, and let the steel plate float peaceful and still on top of the Sorbothane.

To obtain the Sorbothane elements you need to this properly, use the calculator at Sorbothane's Website to figure out how many Sorbothane feet you need, what size and shape they should be, and what "durometer rating" (a metric that, oversimplifying a bit, represents how squishy the specific Sorbothane material is). That calculator may seem complicated, but if you read the instructions a couple of times, and maybe ask some questions here, it's not too bad.

In general terms, you want a Sorbothane arrangement that deforms a certain amount under your rig (IIRC, this may be about 20 percent). Then, any vibration that comes up through your pipe table will hit the partially-squished Sorbothane. Sorbothane is an elastomer that converts vibration to waste heat, so that in a properly-tuned system, very little vibration gets through to your steel base. Thus your base steel should be very still and quiet.

One main value of the heavy steel base is that it lets you make broad assumptions about what vibrational frequencies you need to filter out with the Sorbothane. With a heavy base, it will be low-frequency vibration that you select Sorbothane for.

Another advantage of the steel base is that can be made to tightly couple vibration originating within your rig (from motor movement, shutter movement, etc.) If everything is metal, with no rubber or other squishy bits between, anything that bumps your camera bumps your subject almost exactly the same way. This way, if there is slight movement, it's mutual movement, largely unseen by the camera. This is big advantage.

The first time I saw a vibration isolation system for macro photography was in the Manual of Close-Up Photography, by Lester Lefkowitz. When published, Lefkowitz book was like a Bible for macro photographers; these days, we've largely passed him by--but he gave many of us a lot of good ideas that helped us jump ahead.

Something Lester showed was shooting a picture from a tripod, with the tripod standing near a refrigerator compressor. Unsuprisingly, the resulting images were fuzzy. The he repeated the shoot after placing his tripod legs on top of paving blocks, which were floating on small, underinflated innertubes from go-carts or wheelbarrows. In this arrangement, he obtained far sharper images. Lefkowitz point was: Let the floor vibrate, but place something on it that is mushy and energy absorbing. Then upon that, float something heavy enough to experience low perturbation with whatever small amount of energy gets through the squishy bit. The images he made with this setup were worlds better.

The approach you've outlined--thick, heavy steel with components tightly bolted to it, floated upon appropriately chosen Sorbothane components, your table below that, sounds great. I think it will work well. If it does not, I'd turn my attention to suspending your rig from the ceiling.

Clutch (signifies changing gears)--

Gents, some very interesting posts have come up covering what might be called "Theory of vibration mitigation." But I question if all these posts offer any help to Deanimator with his current dilemma? For any posts that do not, could we create a different thread to hold them and further posts along those lines?

Cheers,

--Chris S

Lou Jost
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Post by Lou Jost »

Chris, that indeed seems like it should be a "sticky" theme somewhere, to be added to regularly.

I'll again add my bit again:
This way, if there is slight movement, it's mutual movement, largely unseen by the camera. This is big advantage.
This is probably right for Deanimator, but such movement is not unseen by the camera with subjects in liquid, or nonrigid subjects with significant moment arms (like stalked spore cases). In those cases, inertia keeps the subject still, but the camera moves. Not good.

mawyatt
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Post by mawyatt »

Edit, Chris I didn't see your post until now. I can remove this is you want, or transfer to another thread if you wish. This might be useful to the OP though, since it does deal with vibrations.

Lou,

It seems with your subjects in liquid that any movements will cause an issue with the subject movement in the liquid.

If I understand this correctly then you don't want tight, rigid coupling between the rail/motor/camera/lens and subject (common mode coupling), as any movements in the camera/lens/motor/rail is transferred to the subject which in effect has "memory" caused by the subject in the liquid.

So you want to reduce/eliminate any camera/lens/motor/rail movements which would get transferred to the subject in liquid. So rail/motor/camera/lens to subject isolation seems reasonable. Of course you do need precision stable position retention relative to subject and camera/lens, since at some point you need an image that is tightly position referenced to the previous images.

This sounds like an application where the motor/rail/camera/lens movement induced "vibrations" need attenuation "at the source" with a system where the subject is fixed and the camera/lens is moved for focus stacking.

The techniques I'm working with that attenuate "at the source" what would normally appear as motor/rail induced vibration might help since the apparent motor/rail movement induced vibrations are effectively absorbed or partially canceled by the manipulation of the velocity, acceleration, deceleration, motor current and waveform profiles. In effect the movement induced vibration isn't created outside the motor/rail connection as it gets "absorbed" by the motor. Another way of thinking how this works is that the motor (an electro-mechanical device) is acting like an open loop "active suspension" vibration suppression device.

With the Trinamic controllers there are lots of control parameters that could help with your unique setup requirements, the Pololu Tic controllers are also potentially useful but don't have some of the features of the Trinamic.

Anyway, something to consider.

Best,
Research is like a treasure hunt, you don't know where to look or what you'll find!
~Mike

Deanimator
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Post by Deanimator »

Chris S. wrote:The approach you've outlined--thick, heavy steel with components tightly bolted to it, floated upon appropriately chosen Sorbothane components, your table below that, sounds great. I think it will work well. If it does not, I'd turn my attention to suspending your rig from the ceiling.
My place is a pit. I wouldn't suspend a black light poster from my ceiling!

If the steel plate doesn't work, I'll just have to suck it up.

Lou Jost
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Post by Lou Jost »

Ray asked
Is the camera rigid-mounted?
No, not when stitching. It would be possible to make a rigid mount for single-row stitching, but not for x-y stitching, with my present design.

clarnibass
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Post by clarnibass »

Sorry I haven't read the entire thread, and I understand it might be convenient for you to get a granite surface plate at a good price. Part of the (much) higher price of granite surface plates is they are made to be flat to a very high standard. I have one for lapping and checking flatness. This is a moot point if you glue or attach a significantly less flat material to it (e.g. a metal plate). You could use a much cheaper and less expensive stone block instead.

I know it might not matter but I'm just mentioning this FWIW.
Last edited by clarnibass on Sat Apr 20, 2019 9:47 pm, edited 1 time in total.

Deanimator
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Post by Deanimator »

clarnibass wrote:Sorry I haven't read the entire thread, and I understand it might be convenient for you to get a granite surface plate god a good price. Part of the (much) higher price of granite surface plates is they are made to be flat to a very high standard. I have one for lapping and checking flatness. This is a moot point if you glue or attach a significantly less flat material to it (e.g. a metal plate). You could use a much cheaper and less expensive stone block instead.

I know it might not matter but I'm just mentioning this FWIW.
That's quite true, subject to the local business culture.

I hate to dicker over price, especially on things about which I know little or nothing. I have no idea what it should cost me to have a generic piece of granite cut to 18"x24"x3". I certainly wouldn't enjoy arguing about it, especially in a place like Cleveland where a "Just take what's offered to you and shut up" mentality often prevails. Seriously, a waitress was once surprised that I wouldn't accept sangria as a substitute for rose because "It was the only red wine we had". Likewise, a waiter was genuinely enraged that I wasn't impressed by "lasagna" with no pasta in it.

If I decide I need a stone base for my rig, I know exactly where to go for a surface plate, what I'm going get, and how much it's going to cost.

That's not a dig at you just an honest assessment of my comfort zone regarding haggling. It's very small.

Deanimator
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Post by Deanimator »

I've created a spreadsheet with the 80/20 parts I think I'll need. I calculated using 40mm x 40mm profiles. It didn't come out too badly cost wise.

I did have a couple of questions for anybody with experience with the Misumi/80/20 profiles and accessories:

Please note the corrections.

Is there a LINEAR bearing (like this: Image)



that will work on this type of profile when it's laid on its side:

Image

Is there a way to join profiles side by side along their lengths using the slots?

How would you mount 40mm x 40mm profile to a steel plate?
Last edited by Deanimator on Mon Apr 22, 2019 2:18 am, edited 3 times in total.

elf
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Post by elf »

Deanimator wrote: I did have a couple of questions for anybody with experience with the Misumi/80/20 profiles and accessories:

Is there a roller bearing (like this: Image) that will work on this type of profile:

Image

Is there a way to join profiles side by side along their lengths using the slots?

How would you mount 40mm x 40mm profile to a steel plate?
The profiles weren't designed for rollers. Open Build extrusions would be better, however, I don't think rollers on aluminum extrusions would be good enough for high mag images. I'm using MGN12 linear slides on my 3d printer and MGN15 on my rose engine. Either would be more than adequate for a camera system. I did need to disassemble and clean the carriages in order to get them to work well. I also am using a set of STAF linear slides on my rose engine. They are much higher quality, unfortunately, with a corresponding higher price.

You can tap the ends of the profiles and use endplates that span both extrusions.

Use tnuts and bolt from the bottom. You can also use the 90 degree angle brackets, but this is more expensive.

Deanimator
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Post by Deanimator »

elf wrote:The profiles weren't designed for rollers.
I'm sorry, that's a mistake on my part. There are no rollers in the bearing pictured, just synthetic inserts. I was doing a bunch of things at one time and mis-typed "roller" when I meant "linear".

elf
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Post by elf »

You can attach mgn12 and mgn15 linear slides directly to aluminum extrusions. I made a full length tnut substitute from a strip of 1/8"x1/2" aluminum bar by drilling and tapping holes.

As far as I know, there are no ball bearing carriages which will run directly on aluminum extrusions.

Deanimator
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Post by Deanimator »

elf wrote:You can attach mgn12 and mgn15 linear slides directly to aluminum extrusions. I made a full length tnut substitute from a strip of 1/8"x1/2" aluminum bar by drilling and tapping holes.

As far as I know, there are no ball bearing carriages which will run directly on aluminum extrusions.
I'm not actually looking for something which will mount any sort of ball bearing carriage. I just need something that will allow me to achieve rough focus when the camera is in horizontal mode. It doesn't even have to be smooth in its movement, since once set it will remain stationary.

I've pretty much decided to just use 40mm x 40mm for the vertical AND horizontal members. A wider flat surface for horizontal would be nice, but I'll have to think of something else.

Deanimator
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Post by Deanimator »

Chris S. wrote:My guess is that it will be enough, if you place a correct arrangement of Sorbothane under your steel, on top of your pipe table. The goal is to let the world vibrate under your Sorbothane, let the Sorbothan dissipate these vibrations by changing them to heat, and let the steel plate float peaceful and still on top of the Sorbothane.
I have a call in to Don about the steel plate.

How would you recommend that I mount the T-slot onto the plate?

I was going to use 40mm x 40mm for the vertical and 40mm x 120mm for the horizontal, but that doesn't look like it's going to work out, so I'm using 40mm x 40mm for both. I was going to use a simple L shape. Would you instead suggest that I add transverse legs and feet in the style of the Wemacro rig?

ray_parkhurst
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Post by ray_parkhurst »

Deanimator wrote:
Chris S. wrote:My guess is that it will be enough, if you place a correct arrangement of Sorbothane under your steel, on top of your pipe table. The goal is to let the world vibrate under your Sorbothane, let the Sorbothan dissipate these vibrations by changing them to heat, and let the steel plate float peaceful and still on top of the Sorbothane.
I have a call in to Don about the steel plate.

How would you recommend that I mount the T-slot onto the plate?

I was going to use 40mm x 40mm for the vertical and 40mm x 120mm for the horizontal, but that doesn't look like it's going to work out, so I'm using 40mm x 40mm for both. I was going to use a simple L shape. Would you instead suggest that I add transverse legs and feet in the style of the Wemacro rig?
Are you going to mount both your subject stage and your camera / lens to the horizontal T-slot member? If so, then I'd personally recommend soft-mounting it. I like to use 3M wall-mounting double-stick tape for such purposes (the grey color, not the super-strong black). A few strips of it in strategic spots will hold it firm, and it will be relatively easy to move around. Best of all, no drilling! You can also tailor the resonance characteristics by putting on additional layers of the material. It has high dampening qualities so helps absorb higher frequency stuff coming from the table.

Edited to add: if the subject will mount to a different system which is mounted to the steel plate, then soft-mounting won't work well.

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