Posts Tagged M2

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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BOB Yak Fender Fracture: Fixed

We agreed that repairing the failed flag ferrule made the trailer much quieter, but it still seemed far more rattly than we remembered. It just had to be the fender, somehow, and eventually this appeared:

BOB Yak Fender Mount - fractures

BOB Yak Fender Mount – fractures

The obviously missing piece of the fender fell out in my hand; the similar chunk just beyond the wire arch fell out after I took the pictures. Yes, the wire has indented the fender.

The arch supports the aluminum fender, with a pair of (flat) steel plates clamping the wire to the fender:

BOB Yak Fender Mount - screw plates and pads

BOB Yak Fender Mount – screw plates and pads

The cardboard scraps show I fixed a rattle in the distant past.

Being aluminum, the fender can’t have a replacement piece brazed in place and, given the compound curves, I wasn’t up for the requisite fancy sheet metal work.

Instead, a bit of math produces a pair of shapes:

BOB Yak Fender Mount - solid model

BOB Yak Fender Mount – solid model

In this case, we know the curve radii, so the chord equation gives the depth of the curve across the (known) width & length of the plates; the maximum of those values sets the additional thickness required for the plates. The curves turn out to be rather steep, given the usual layer thickness and plate sizes, which gives them a weird angular look that absolutely doesn’t matter when pressed firmly against the fender:

BOB Yak Fender Mount - Slic3r preview

BOB Yak Fender Mount – Slic3r preview

The computations required to fit Hilbert Curve surface infill into those small exposed areas took basically forever; given that nobody will ever see them, I used the traditional linear infill pattern. A 15% 3D Honeycomb interior infill turned them into rigid parts.

The notch in the outer plate (top left, seen notch-side-down) accommodates the support wire:

BOB Yak Fender Mount - outer

BOB Yak Fender Mount – outer

The upper surface would look better with chamfered edges, but that’s in the nature of fine tuning. That part must print with its top surface downward: an unsupported (shallow) chamfer would produce horrible surface finish and life is too short for fussing with support. Given the surrounding rust & dings, worrying about aesthetics seems bootless.

The original screws weren’t quite long enough to reach through the plastic plates, so I dipped into my shiny-new assortment of stainless steel socket head cap screws. Although the (uncut) M5x16 screws seem to protrude dangerously far from the inner plate, there’s another inch of air between those screws and the tire tread:

BOB Yak Fender Mount - inner

BOB Yak Fender Mount – inner

Given the increase in bearing area, that part of the fender shouldn’t fracture for another decade or two.

I loves me my M2 3D printer …

The OpenSCAD source code as a GitHub Gist:

The original dimension measurement and design doodle:

BOB Yak Fender Mount - doodles

BOB Yak Fender Mount – doodles

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Dishwasher Rack Protectors in PETG

Our standard dishwasher loadout changed a while back, so I ran off more protectors to fill the bottom rack. The crystalline look of natural PETG is probably wasted in there, even though it puts the old, rather yellowed, PLA protectors to shame:

Dishwasher Rack Protectors - old PLA new PETG

Dishwasher Rack Protectors – old PLA new PETG

Dollops of silicone sealant hold them in place: the bigger the blob, the better the job.

We don’t activate the drying heater, so the plastic doesn’t get exposed to absurdly high temperatures. As nearly as I can tell, those PLA protectors remain in fine physical condition, even though they’re turning an odd color.

The support structures peeled out easily with a fingernail pull:

Dishwasher Rack Protectors - 0.20 mm PETG bridging - detail

Dishwasher Rack Protectors – 0.20 mm PETG bridging – detail

PETG doesn’t bridge well, as shown by the gaps between the support ridges. Those 0.20 mm layers seemed skimpy for lightly supported PETG, so I ran another set at 0.25 mm:

Dishwasher Rack Protectors - 0.25 mm PETG bridging - detail

Dishwasher Rack Protectors – 0.25 mm PETG bridging – detail

Not quite enough improvement for a Happy Dance, although fine for the application.

We look forward to seeing what grows in those little crevices…

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Inspiron Mini 10 as a 3D Printer Controller

It turns out that the dual-core Intel Atom Inside an old Dell Mini 10 isn’t up to the demands of rendering modern web design; disk I/O speed has nothing to do with the CPU’s (lack of) ability to chew through multiple layers of cruft adorning what used to be straightforward static HTML.

So, equipped with Linux Mint / XFCE, it’s now found a new purpose in life:

SnowWhite back in action

SnowWhite back in action

In truth, an Atom isn’t quite up to the demands of modern 3D printing, either, at least in terms of processing a huge G-Code file into a layer-by-layer path preview. Fortunately, Pronterface doesn’t generate the preview until you ask for it: arranging the UI to put the preview on a separate tab eliminates that problem.

The Mini 10 can dribble G-Code into the printer just fine and looks much cuter than the hulking laptop in the background.

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Ersatz 5.5 mm Nut Driver

A tiny 1/4 inch hex driver handle appeared from the far reaches of a drawer, sporting a handle better suited for tweaking the 3 mm adjusting nuts on the bottom of the M2’s platform than applying actual torque to real fasteners. Rather than breaking a set of nut drivers, I made a simple brass shim to soak up the difference between the handle’s 6.5 mm ID hex and the 5.5 mm OD of the nuts:

Hex driver shim - installed

Hex driver shim – installed

That’s 15 mil = 0.40 mm shimstock to leave enough clearance for my crude forming technique.

Which technique consisted of making a “mandrel” by lining up a trio of Nyloc nuts on a screw, snipping off a suitable shimstock rectangle, and squashing it into shape with parallel-jaw pliers:

Hex driver shim - forming

Hex driver shim – forming

As you’d expect, the shimstock hex came out larger & uglier than the mandrel:

Hex driver shim - formed

Hex driver shim – formed

But that doesn’t matter after it’s tucked inside the driver; it works perfectly.

Took less time to do than to write up …

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