Posts Tagged M2

Octal Tube Base Clamp

One of the octal tubes in my collection has a broken spigot / key post that lets some light in through the bottom of the normally opaque Bakelite base:

Octal socket in CD - LED diffraction

Octal socket in CD – LED diffraction

Perhaps drilling out the base would let more light pass around the evacuation tip, but that requires a shell drill to clear the tip. Some doodling suggested a drill with 12 mm OD and 8 mm ID, which was close enough to one of the smaller homebrew drills in my collection that I decided to see how it worked:

Shell drill assortment

Shell drill assortment

You (well, I) can’t freehand such a hole, particularly with a glass tip in the middle, so I needed a way to clamp the tube in either the drill press or the Sherline. A pad for the clamp screw in a V-block seemed appropriate:

Vacuum Tube Lights - Octal base clamp - Slic3r preview

Vacuum Tube Lights – Octal base clamp – Slic3r preview

The screw hole sits at the 1/3 point to put more pressure near the pin end of the base. Maybe that matters.

The setup looks like this, with a small red laser dot near the front of the base:

Octal tube clamped on Sherline mill

Octal tube clamped on Sherline mill

The tube rests on a random scrap of plastic, with the hope that the drill won’t apply enough pressure to break the glass envelope.

In normal use, the V-block would be oriented the other way to let you cross-drill the cylinder. In this end-on orientation, drilling torque can rotate the tube; compliant padding for more traction may be in order.

The OpenSCAD source code as a GitHub Gist now includes a module that spits out the clamp:

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Vacuum Tube LEDs: Aligning the Plate Cap Leads

The original plate cap, even without fins, seemed entirely too large for the 21HB5A tube.  There’s not much wasted space inside and, after trimming the outside a bit, this is about as small as seems possible:

Vacuum Tube Lights - thin cap solid model - section

Vacuum Tube Lights – thin cap solid model – section

PETG doesn’t bridge well and, after cleaning out the wire hole, the remaining shell didn’t hold the brass tube very securely. Epoxying tubes into two caps at once, with a longer brass tube holding them in alignment, worked well:

Black PETG Plate Caps - brass tube alignment

Black PETG Plate Caps – brass tube alignment

The tube eliminates vertical tilt and you (well, I) can eyeballometrically align the caps and tubes in azimuth. The thin ring of JB Kwik epoxy around the brass tube isn’t visible, so it’s all good:

21HB5A - Black PETG base - flash

21HB5A – Black PETG base – flash

This project may eventually force me to try epoxy coating, high-build primer, and good paint…

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Hard Drive Platter Drilling Fixture

After drilling the platter for a Noval tube, I finally made a fixture to hold the platters firmly, but gently, in the proper position for drilling:

Hard drive platter - drilling fixture

Hard drive platter – drilling fixture

The platter sits more-or-less flush with the surface, where credit-card plastic pads work fine. Thinner platters may require compliant padding.

The solid model has locating pips at ±50 mm from the center and airspace below the platter for the drill bit:

Vacuum Tube Lights - hard drive fixture - solid model

Vacuum Tube Lights – hard drive fixture – solid model

The 1.16 inch hole spacing matches the Sherline’s tooling plate. The center hole seemed like a Good Idea, although it has no purpose right now.

The OpenSCAD source code is the same as before; just set Layout = PlatterFixture; and it’ll produce the right thing.

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Smithsonian’s Apollo 11 Command Module

An old friend asked for a copy of the Smithsonian’s Apollo 11 Command Module. I started with a tiny 1:80 version to check feasibility:

Apollo 11 CM - 1-80 scale

Apollo 11 CM – 1-80 scale

It’s obviously not printable in one piece without a ton of support, so I chopped off the heatsink and printed the parts separately in the obvious orientation:

Apollo 11 CM - 1-80 scale - split - Slic3r preview

Apollo 11 CM – 1-80 scale – split – Slic3r preview

And glued them back together:

Apollo 11 CM - clamping

Apollo 11 CM – clamping

That worked well enough, even without locating pins, to give me confidence that it’d come out all right.

There’s plenty of gimcrackery surrounding the upper airlock:

Apollo 11 CM - 1-40 scale - top - Slic3r preview

Apollo 11 CM – 1-40 scale – top – Slic3r preview

Most of which simply vanished at 1:80 scale:

Apollo 11 CM - 1-80 scale - top detail

Apollo 11 CM – 1-80 scale – top detail

I made another cut just below the top of the capsule and ran off a 1:40 scale version that came out somewhat better, but it was still ugly:

Apollo 11 CM - 1-40 scale - mortar detail

Apollo 11 CM – 1-40 scale – mortar detail

Much to my astonishment, the grab rail over the side hatch, between the two parachute motars, came out well every time.

The giant 1:20 scale version would require something over 24 hours of printing, so I went with 1:30 in three pieces:

Apollo 11 CM - 1-30 scale - sections

Apollo 11 CM – 1-30 scale – sections

The top had pretty good detail:

Apollo 11 CM - 1-30 scale - top section - 1

Apollo 11 CM – 1-30 scale – top section – 1

Another view:

Apollo 11 CM - 1-30 scale - top section - 2

Apollo 11 CM – 1-30 scale – top section – 2

Gluing the parts together made it ready for cleanup / finishing / painting:

Apollo 11 CM - 1-30 scale - assembled

Apollo 11 CM – 1-30 scale – assembled

Which he’s better at than I ever will be…

Natural PETG probably isn’t the right plastic for that kind of model, but it’s what I had on hand.

Enjoy!

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Miniblind Cord Caps

After smashing one of the cord pulls between the sash and the frame:

Miniblind cord caps - installed

Miniblind cord caps – installed

The glittery PETG looks surprisingly good in the sunlight that will eventually change it into dullness. The black flecks come from optical effects in the plastic, not the usual burned PETG snot.

The solid model is basically a hull around two “spheres”, truncated on top & bottom:

Miniblind cord cap - solid model

Miniblind cord cap – solid model

The interior has a taper to accommodate the knot, but they’re chunky little gadgets:

Miniblind cord cap - solid model - bottom

Miniblind cord cap – solid model – bottom

I thought the facets came out nicely, even if they’re mostly invisible in the picture.

Each pull should build separately to improve the surface finish, so I arranged five copies in sequence from front to back:

Miniblind cord cap - 5 sequential - Slic3r preview

Miniblind cord cap – 5 sequential – Slic3r preview

If you’re using an M2, the fans hanging off the front of the filament drive housing might come a bit too close for comfort, so rotate ’em upward and out of the way.

If you remove the interior features and flip ’em upside down, they’d work well in Spiral Vase mode. You’d have to manually drill the top hole, though, because a hole through the model produces two shells.

The OpenSCAD source code as a GitHub Gist:

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Kenmore Progressive Vacuum Tool Adapters: First Failure

I picked up a horsehair dust brush from eBay as a lightweight substitute for the Electrolux aluminum ball, discovered that an adapter I’d already made fit perfectly, did the happy dance, and printed one for the brush. That worked perfectly for half a year, whereupon:

Dust Brush Adapter - broken parts

Dust Brush Adapter – broken parts

It broke about where I expected, along the layer lines at the cross section where the snout joins the fitting. You can see the three perimeter shells I hoped would strengthen the part:

Dust Brush Adapter - layer separation

Dust Brush Adapter – layer separation

That has the usual 15% 3D Honeycomb infill, although there’s not a lot area for infill.

There’s obviously a stress concentration there and making the wall somewhat thicker (to get more plastic-to-plastic area) might suffice. I’m not convinced the layer bonding would be good enough, even with more wall area, to resist the stress; that’s pretty much a textbook example of how & where 3D printed parts fail.

That cross section should look like this:

Dust Brush Adapter - Snout infill - Slic3r preview

Dust Brush Adapter – Snout infill – Slic3r preview

Anyhow, I buttered the snout’s broken end with JB Kwik epoxy, aligned the parts, and clamped them overnight:

Dust Brush Adapter - clamping

Dust Brush Adapter – clamping

The source code now has a separate solid model for the dust brush featuring a slightly shorter snout; if when the epoxy fails, we’ll see how that changes the results. I could add ribs and suchlike along the outside, none of which seem worth the effort right now. Fairing the joint between those two straight sections would achieve the same end, with even more effort, because OpenSCAD.

The OpenSCAD source code as a GitHub Gist:

 

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FG085 Function Generator

The topic of function generators came up at Squidwrench a while ago (Sophi was tinkering with LCD shutters) and I finally picked up one of those JYE Tech FG085 DDS function generators to see how they work:

FG085 Fn Gen - in case

FG085 Fn Gen – in case

Short answer: adequate, if you’re not too fussy.

The board arrived with a bizarre solder defect. It seems a solder stalk yanked one terminal off a ceramic SMD caps:

FG085 - Solder stalk - C26

FG085 – Solder stalk – C26

The schematic and adjacent parts suggested the victim was a 10 uF cap, so I replaced it with one from my stash that worked fine.

However, after soldering enough of the switches to do something useful, the board wouldn’t power up. With a bit of poking around, I discovered the power jack had +15 V from the wall wart, but the center terminals on the DPDT power switch that should have been connected to the jack showed maybe 0.3 V. Jumpering around the failed via and a short trace on the bottom surface let the board power up correctly:

FG085 - Jumpered power trace

FG085 – Jumpered power trace

If you’re building one of these, solder one pin of each switch, push all the switch caps in place, shove the faceplate over all of them, tape it to the PCB, make sure all the switches are push-able, then solder the remainder of the switch pins. If you do them one by one, you’re certain to end up with a few mis-aligned switches that will either prevent the faceplate from sliding over them or wedge firmly against the side of their assigned hole. Just sayin’.

It lives in a case from Thingiverse:

FG085enclosure - 1268379

FG085enclosure – 1268379

I tweaked the dimensions slightly to fit the (slightly larger, possibly new, maybe tolerance-eased) front panel, but the bottom mounting screw hole spacing depends on the front panel size, not a specific set of dimensions, leading me to relocate those holes by abrasive adjustment. I didn’t bother with the lid (which doesn’t clear the BNC jack anyway) or the printed plastic feet (having a supply of silicone rubber feet).

The fancy vent gridwork along the sides printed surprisingly well, even in PETG. I’d have gone with larger slots, although I doubt the thing really needs vents in the first place.

The DDS sine wave output is rough, to say the least:

FG085 Fn Gen - 60 kHz sine

FG085 Fn Gen – 60 kHz sine

The spectrum shows oodles of harmonic content:

FG085 Fn Gen - 60 kHz sine - spectrum

FG085 Fn Gen – 60 kHz sine – spectrum

A closer look:

FG085 Fn Gen - 60 kHz sine - spectrum - detail

FG085 Fn Gen – 60 kHz sine – spectrum – detail

Stepping back a bit shows harmonics of (and around) the 2.5 MHz DDS sampling frequency:

FG085 Fn Gen - 60 kHz sine - spectrum - 10 MHz

FG085 Fn Gen – 60 kHz sine – spectrum – 10 MHz

For comparison, my old Fordham FG-801 analog function generator has nice smooth harmonics:

FG-801 Fn Gen - 60 kHz sine - spectrum

FG-801 Fn Gen – 60 kHz sine – spectrum

Closer in:

FG-801 Fn Gen - 60 kHz sine - spectrum - detail

FG-801 Fn Gen – 60 kHz sine – spectrum – detail

Of course, that crusty old analog dial doesn’t provide nearly the set-ability of a nice digital display.

 

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