Robustness of OpenRAMAN to transport

[Lincoln20XX]

Greetings from Canada!

I was speaking with a friend about OpenRAMAN as a possible technology to employ in a mobile testing service.

I'm aware that this system was not necessarily designed with this use case in mind.

I'm a mechanical engineer by education and trade, so I do have some fundamental knowledge of some of the parts that go into this type of system, but I don't have any way of assessing how it could be affected by regular transport or movement.

My baseline assumption is that any device that utilizes high-precision optics is not going to be happy with being moved around from place to place on a regular basis, but I don't know if this is something that could be accounted for in some relatively simple manner.

The build instructions make me think that it might not be that much of a problem so long as the system is not unreasonably abused, but I've had such assumptions bite me before, so I figured it would be best to ask those much more knowledgeable than I.

I'd be more than happy to do some reading and educate myself further if anyone would be willing to point me toward some specific resources on the topic.

Thanks!

[andy]

I can speak to this as I've shipped some builds

There's a few issues:

• The camera is held on by a single bracket so it "floats". It stays in place but I think it might slightly slide if the travel was rough
• The kinematic alignment tools stay in position pretty well and are stiff, but they don't lock in place.
• I remove the laser, otherwise that might slide a bit
• Only the spectrometer part has a cover, rest does not so dust could be an issue if you don't cover it well
• The liquid cuvette holders could lock in if you tap the side holes, I don't think the solid one would travel well attached. The DIY laser performance edition I am not sure.

Be sure to keep all the set screws and alignment screws tight. Be prepared to re-align/ re-calibrate after shipping. But otherwise it does travel if you package it well.

As for use in a mobile setting.. I doubt it would work under high vibration given the design. Slight vibration should be fine... Luc has mentioned before the vinyl absorbes some of it.

See my thread about my new raman probe, if that works I think it will be better in a mobile environment given the lenses are glued on but we'll have to see if it works at all..

[andy]

I want to emphasize one thing... the screws MUST be tight. If they are lose things will move even by a firm touch while using the system.

It would be worth someone figuring out a good torque wrench value. If you use the vinyl 3d printing you can strip the screws, so there's a range of things being very tight and not moving but not too tight. The set screws should be tightened less as they are smaller.

If this is helpful, I have been tightening things to just past quite firm, and I usually test to see how much effort it takes to mis-align something (by pushing the parts). When I first starting building, I would find that even though I thought the screws were tight enough, they would slide out of alignment as I was working without me noticing.

[Lincoln20XX]

Excellent, thanks so much!

I was planning on recommending that they pick up one of your systems if they actually turn out to be the correct tool for the job, so I very much appreciate the input.

[andy]

Yep, no problem.

If they were driving around with the system in the back of a truck, it should work assuming everything was screwed tight. They would just want to check alignment at each stop but that takes no more then a minute if you are quick.

Thanks for the question!

[Luc]

That's pretty much it. As mentioned, the weak point is (used to be) the camera bracket but I already redesigned it -- just not released yet.

With gentle driving and the spectrometer in a box with bubblewrap it shouldn't be an issue. For "production" grade stuff I would make a few changes:

• only CNC aluminum parts, no 3D printed plastic at the exception of the cuvette thing
• use ~3Nm torque settings for all M4 screws (metal/metal, not metal/glass)
• replace the kinematic mount by either locking version or stainless steel "heavy duty" versions
• replace the camera bracket by the new one
• apply dots of epoxy glue on all non-torqueable parts (laser, camera c-mount etc.)

After that it should even survive DHL transport

FYI, this is the new camera bracket:

wip-camera-bracket-v2.png (43.58 KiB) Viewed 10075 times

[Lincoln20XX]

Switching to CNC aluminum certainly sounds like a solid (heh) idea to me. That's getting closer to where I'm comfortable in my own experience, and I've got a few good CNC shops in my back pocket.

When balancing rotating equipment, I've found that HVAC fans, people walking by the installation, and other environmental factors can produce noticeable noise levels on moderately sensitive equipment. So it seems like it might be a not-terrible idea to plan for some kind of simple anti-vibration mounting/feet if one were to go to an aluminum base + assembly, even for static lab installations.

[Luc]

It's not going to be as-sensitive as an interferometer (which will react to people slamming doors etc.) but you might want to isolate it a bit in harsh environments.

You have plenty of choices for that, but I'll focus on sorbothane feets:

https://www.thorlabs.de/newgrouppage9.c ... up_id=6421

The holes of the baseplate have clearance for M4 so you'll need a M4 <-> M6 adapter or enlarge the holes of the baseplate