A tale of two microscopes

I recently became the proud owner of a couple of discarded JEOL scanning electron microscopes. The big one (“Milly“) is a JSM-6320F from the early 1990s. The little one (“Meryl“) is a JSM-5600 from the early 2000s.

Milly the SEM.
This is Milly. She’s large and in charge.
This is Meryl. She may be small, but I wouldn't cross her.
This is Meryl. She may be small, but don’t let that fool you. She’s plenty of trouble.

They sat in storage for about five years, and the previous owner had a lot of trouble getting them running again. That trouble has now passed on to me, and I’m in the process of restoring them to their former glory.

Where to begin

Of the two, Milly is a lot more technically interesting. She uses an FEG emitter (requiring an ultra-high vacuum to operate). She has an SEI imager and an X-ray backscatter detector, and was once capable of producing extremely impressive images at about 1nm resolution.

On the downside, she’s a little complicated. Her vacuum system uses two roughing pumps (not supplied), two diffusion pumps, and three ion pumps. Getting the vacuum down below 10-9 Torr requires perfect seals and a finicky bake-out process. Her power requirements are a little fancy. And being late 1990s technology, her “computer” looks like something used on one of the Apollo missions.

Old console is old.
This console features not two, but three CRTs (counting the Polaroid film scanner tube).

In addition to these challenges, I’ve never actually used (let alone worked on) an SEM. While Milly might eventually take stunning images, I have a feeling that the road to getting there may be a long one.

Lucky for me, Milly has a little sister.

And then there’s Meryl

Meryl is a much simpler SEM. She uses a thermionic emitter (a simple tungsten filament) rather than an FEG. She doesn’t require UHV, so her seals are simply rubber gaskets. There is only one roughing pump (provided!) and a single diffusion pump. She only needs 100V AC, which is easily converted from standard 110 with a supplied variac. She only takes up about half the space of her big sister. Best of all, she even came with a few spare parts, which considering my inexperience, I fully expect to install.

Oscilloscope says... not enough vacuum.
Does the patient have a pulse? Pirani gauge says… not yet.

Watch this space for updates as the great microscope adventure unfolds.

Brass to Bits

Minnie’s name plate is finally finished! Let’s start with the finalé and work backwards :

minnie
The finished name plate. So purdy!

The black is high gloss automotive paint. I sprayed a nice thick layer over the entire piece, let it dry, then hit it with an orbital sander to remove the excess. A thin layer of clear-coat will hopefully keep it from tarnishing.

I had initially tried a more conservative shot of enamel, but it didn’t like the clear-coat. So one acetone wash later and it was back to the spray booth improvised from the remains of that old janky laser cutter.

Here’s the piece before sanding:

Before sanding, she's back in black.
She’s back in black!

The brass cut pretty cleanly on the cncbot. Before I ran the cut in brass, I did several tests in plywood, which cuts like butter. For best results with brass, the rule seems to be SLOW DOWN AND USE MORE LUBE.

Before plywood, I simulated the gcode with Cutviewer to make sure I didn’t have any obvious mistakes:

The gcode was generated in CamBam (not free, Windows only, but reasonably priced and very easy to go from simple DXFs to mill-friendly gcode). The UI is pretty basic, but it has some nice features like auto-computing cutout tabs and integration with Cutviewer.

cambam-minnie

The rest of the toolchain is better left un-blogged. It’s ugly.

The DIY 3D printing world is fairly well covered with good software at this stage. But the path from bits to atoms via milling machines seems to be strewn with the debris of good intentions, abandoned java blobs, questionable firmware, and people who think that running Debian 3.0 on a 486 with a parallel port is the pinnacle of desktop CNC.

Let’s just say GRBL and the Universal-G-Code-Sender eventually got us there in the end.