Melting 3D printed patch stops

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EVILsteve
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Melting 3D printed patch stops

#1 Post by EVILsteve » Wed Jan 12, 2022 5:35 pm

This is on a Nikon alphaphot with a 3d printed holder and patch stops for darkfield mounted right below the condenser diaphragm. The petg starts to melt within 3 minutes if the light intensity is much more than about 1/3 to 1/2 the full brightness or more. It does this right below the iris opening where the light is concentrated from the light source. Is this normal? It's not convection heat from the halogen as I can sit one of the patch stops on top of the light source without melting it just where it seems to focus right below the abbé condenser.

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josmann
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Re: Melting 3D printed patch stops

#2 Post by josmann » Wed Jan 12, 2022 7:30 pm

Hi Steve,

I don't know about this scope in particular, but I would be surprised if any scope was melting filters when properly aligned. I could see a little heat warping or softening but are you saying the light is being focused down to a point at the iris and you're getting melting like you'd get with a magnifying glass focusing the sun? That's definitely not what the light field should be like! It should be rather broad, evenly spread, and roughly cylindrical as it impinges anything at the iris plane.
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dtsh
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Re: Melting 3D printed patch stops

#3 Post by dtsh » Wed Jan 12, 2022 8:11 pm

If I am undestanding correctly, that seems like an awful lot of IR if it isn't simply heat coming off the lamp housing, perhaps there's a missing IR filter?

EVILsteve
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Re: Melting 3D printed patch stops

#4 Post by EVILsteve » Wed Jan 12, 2022 8:42 pm

It's just like a magnifying glass and the sun. I'd held sheet of paper vertically to see the beam path and it's focused but not pinpoint like you'd try to achieve with a magnifying glass. I'd wondered about IR there is no filter that I'm aware of unless it's the clear cover over the light source lens. I ordered a blue filter thinking that would stop some red light.
It fully melts the stops though. I designed a holder with a slot they slide into and it mets them enough to droop and necessitate cutting it out. Even tried printing new stop holders and moving the stops higher and lower to get it out of the focused spot thinking I'd happened to pick a bad spot but I'm just moving a few mm either way and could achieve better results.

Makes me wonder what I've been doing to my eyes.

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josmann
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Re: Melting 3D printed patch stops

#5 Post by josmann » Wed Jan 12, 2022 9:15 pm

Hmmm, we need someone with alphaphot experience here to understand how this might happen. My best guess is that it's missing a diffuser element somewhere but I'm not sure if these had one - same re: IR filter. Halogen bulbs definitely put out enough heat and light to melt stuff if focused to a point but the illuminator system shouldn't be focusing this light so strongly. If you hold a tissue paper between the field lens and the condenser and move it up and down, it should pretty much be a circle with the diameter of the field lens all the way up and down.
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EVILsteve
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Re: Melting 3D printed patch stops

#6 Post by EVILsteve » Wed Jan 12, 2022 9:37 pm

I believe I'm missing a piece I do not have the protruding section on the bottom past the mount like this one on eBay that looks like it has a diffuser attached. theres a frosted lens directly above the bulb. I will confirm this when I'm back home tonight.


https://www.ebay.com/itm/144304671443?m ... olid=10050

Holding a tissue up shows slight focusing from memory checkibg that the other day is guess it would focus at least a meter above the top of the scope.

Hobbyst46
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Re: Melting 3D printed patch stops

#7 Post by Hobbyst46 » Wed Jan 12, 2022 9:52 pm

A blue filter is not an efficient blocking filter. To block halogen radiated heat (namely, IR) you need an IR blocking filter. For example, type KG5 from Schott, Germany or equivalent.

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josmann
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Re: Melting 3D printed patch stops

#8 Post by josmann » Wed Jan 12, 2022 9:58 pm

EVILsteve wrote:
Wed Jan 12, 2022 9:37 pm
I believe I'm missing a piece I do not have the protruding section on the bottom past the mount like this one on eBay that looks like it has a diffuser attached. theres a frosted lens directly above the bulb. I will confirm this when I'm back home tonight.
Ah, interesting, yeah that would make a lot of sense! 10 bucks is a nice price if that's all there is to it. Please take some photos if you can!
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MicroBob
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Re: Melting 3D printed patch stops

#9 Post by MicroBob » Thu Jan 13, 2022 4:10 pm

Which colour does the stop have? PLA or PETG in black might become too warm just from the absorbed visible light. In this case a layer of aluminium foil would solve the problem.

EVILsteve
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Re: Melting 3D printed patch stops

#10 Post by EVILsteve » Mon Jan 24, 2022 2:49 am

Thanks for the suggestions on this issue I did find some solutions and became aware of some of the limitations to the alphaphot line during the process. Here are my findings.

The condenser was not missing any parts, seems there are different types of illumator lenses for the specific models of alphaphot. Mine is the YS2-T the one in the ebay link above was for the YS2-H probably a better version than mine. Mine very much focuses the light beam straight into the condenser creating the localized hot spot right around the diaphragm area. Any diffuser material seemed to make a notable difference with my version such as a piece of tracing paper, wax paper even a sheet of clear plastic i roughed up on both sides with some sandpaper reduced the heat considerably.

Blue filter completely stopped the heat issue. Printing in any colour beside black stopped the melting but darker shades got pretty hot grey worked fairly well. Aluminum foil, paper or white paint fixed the issues but aliminum foil tended to tear from the petg after a few uses. nothing glues well to petg, PLA would have probably worked better with the foil.

Nothing is in alignment on this scope causing the heat to focus on the side of the darkfield stops, aligning everything helped but didnt fix the melting issue. The light source was off center from the objectives and the condenser is doing some major compensating to make it work. This is pretty noticeable at higher magnification where closing the iris shades across the image like I'm sliding in an oblique filter. There are no adjustments I can make with any component on the light source. The upper portion of the stand has some wiggle room when its loosened from the base but without kohler illumation alignment is a bit more complicated. after many many 3D prints of stops with varying diameter holes i could fit on the lightsource lens to mimic a closed field diaphram helped center the objective to the light source while the condenser was removed.

This whole thing sent me down the LED conversion rabbit hole which also completely fixed the heat issue. Ultimately I just think this is not the scope for me and an upgrade is probably in my best interests. This was targeted to a student market or someone that doesn't like to tinker and build that someone is not me.

My alphaphot and patchstop holder, some heat deformed patch stops
https://i.imgur.com/8GW1jVV.jpg
https://i.imgur.com/xaDG2ax.jpg
https://i.imgur.com/NMGyxkA.jpg
https://i.imgur.com/zarI3jY.jpg

MY led conversion. "machined" on the tablesaw -still a work in progress.
https://i.imgur.com/nTHNDYk.jpg
https://i.imgur.com/eTR93xl.jpg
https://i.imgur.com/4wKxmj3.jpg

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josmann
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Re: Melting 3D printed patch stops

#11 Post by josmann » Sat Jan 29, 2022 1:40 am

EVILsteve wrote:
Mon Jan 24, 2022 2:49 am
MY led conversion. "machined" on the tablesaw -still a work in progress.
Very modest - that looks fantastic compared to what I usually do!

Would you mind sharing details for the power supply and driver board?

Glad you got this all sorted out!
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