This last week has been pretty visual and photogenic. Considering I normally work with things that are either not visible to the human eye or things so bright they’d fry my camera, this was a nice change. So this post is a visual record of what I’ve spent my time doing.

This week I’ve been doing two things. Fixing my 3D printer and trying to calibrate a moveable slit for my laser. What happened to you 3D printer you ask, well this happened.


One of my prints went wrong and the net result was that I managed to totally fill the entire print head with green plastic. Which I’m sure you can guess, isn’t supposed to happen.

But it’s okay because after seeking some help on a forum I managed to partially solve the issue with the use of a heat gun.


Sadly however, you might notice that the coolant fan is now a different shape. I managed to melt it and have now had to send off for a replacement….doh!

But while that was going on I was also trying to calibrate our laser slit. Our laser slit is a mechanical system we built which can move two metal plates apart very precisely so we can create beams of light with a precisely controlled thicknesses.

Slit photo

From time to time this very accurate slit becomes a lot less accurate and needs re-calibrating. The only way to do this is to remove the slit and put it under a high precision microscope.

Luckily for me we have just such a microscope. A few years ago the department purchased a super flashy Olympus microscope which can measure things to the nearest 0.1µm (very small), it’s super easy to use and produces nice internet friendly photos!

Sadly my stupid slit didn’t fit under that microscope and I had to use the ancient Vickers one which has some fun features like; a thick layers of dust on every lens.

The company that made this microscope hasn't existed since 1999

The company that made this microscope hasn’t existed since 1999

Unlike the fancy microscope the Vickers system doesn’t have a camera or any automatic measurement systems. I had to do the whole thing using some maths and by counting little marks on the eye piece. Unfortunately the best picture I could get this was this. You can just make out the edge of the slit and the crosshairs I had to use to guess/make up the measurements with.

TIL that you can't take a phone camera photo down a microscope

TIL that you can’t take a phone camera photo down a microscope

But lucky for you I am a master artists [citation not found] and I went old school and drew some of the this I could see down the microscope.

This is either a great drawing of what I saw in the microscope or a horrifying drawing of a whale

This is either a great drawing of what I saw in the microscope or a horrifying drawing of a whale

The drawing above is when the slit was allegedly ‘closed’ and as you can tell it wasn’t exactly the razor sharp edge it was meant to be. Further investigation showed that apparently our little laser may have been burning a hole in the metal slit over time. I don’t have a picture but the back of the slit (the bit facing the laser) looked like it had been in some kind of futuristic war.

I did also have a go measuring the slit using our even – older stand off microscope which we conservatively estimate pre-dates me by about 10 years. Sadly after spending 15mins working out how to read the vernier scale we found it wasn’t accurate enough (tbh it wasn’t even close).


But despite these minor historic setbacks I re-built, calibrated the slit and remounted it in the laser path. To then prove that we had properly calibrated the slit I used it (and the laser) to burn some bits of glass fibre optic. I did this because burning things is fun and because I can then check the slit width by measuring the amount of the fibre burnt by the laser.

Thankfully a short bit of fibre optic does fit under the very cool fancy Olympus microscope so the photo I got of that is much better.

Hair vs fibre

What you can see above is the fibre burnt at three different slit widths. I also managed to include a human hair in shot for scale. I think the most important thing to note in this photo is that I have very healthy hair.

And finally just to round off a fun week in the lab a nice person gave me a free pizza 😀



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1 Comment

James P · 4 June 2014 at 11:54

I love the different and carefully adjusted levels of care & precision used on the different equipment.
– Delicate, expensive, plastic coolant fan = Google = Heat Gun by hand
– ‘Big slabs of metal’ slit = microscopic analysis to determine best course of action

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