The Smell of Molten Projects in the Morning
Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Taking & making images.
Another page from my father’s Sophomore Biology Laboratory Notebook:
This time he got dinged five points for being late, so that’s not anything new with kids these days…
A detailed look at the frog (clicky for more dots):
They really don’t do labs like they used to…
Having established the OpenSCAD can produce a height map from an input array, a bit more doodling showed how to produce such an array from a grayscale image. I certainly didn’t originate all of this, but an hour or two of searching with the usual keywords produced snippets that, with a bit of programming-as-an-experimental-science tinkering, combine into a useful whole.
Not being much of an artist, I picked a suitable SVG image from the Open ClipArt Library:
That’s pretty, but we need a grayscale image. Some Inkscape fiddling eliminated all the nice gradients, changed the outline to a dark gray, made all the interior fills a lighter gray, and tweaked the features:
Admittedly, it looks rather dour without the big smile, but so it goes. This is still an SVG file, so you have vector-mode lines & areas.
A bit more work changed the grays to produce different heights, duplicated one of the spots for obvious asymmetry, and exported it as a gritty 160×169 pixel PNG image:
The low resolution corresponds to a 2 pixel/mm scale factor: 169 pixel = 84.5 mm tall. The cutter wrapped around this image will have a lip that adds about 12 mm, a 1 or 2 mm gap separates the press from the cutter, and there’s a skirt around the whole affair. My Thing-O-Matic build platform measures a scant 120 mm in the Y direction, which puts a real crimp on the proceedings.
That’s assuming the usual 1 unit = 1 mm conversion factor. If your toolchain regards units as inches, then you need a different scale factor.
Low resolution also speeds up the OpenSCAD processing; you can use as many pixel/mm as you wish, but remember that the extruded filament is maybe 0.5 mm wide, so anything beyond 4 pixel/mm might not matter, even if the motion control could benefit from the smoother sides. Features down near the resolution limit of the model may produce unusual effects for thin walls near the thread width, due to interpolation & suchlike (which is why I got rid of the smile). The processing time varies roughly with the number of pixels, so twice the resolution means four times more thumb-twiddling.
Caveats:
With a suitable PNG image file in hand, use ImageMagick to prepare the image:
-trim (depends on the four corners having background color)-type Grayscale (in case it’s a color image)-depth 8 (more won’t be helpful)-auto-level (to normalize the grayscale to the full range = full height)-flop (think about it)-flipThusly:
convert filename.png -trim -type Grayscale -depth 8 -auto-level -flop -negate -flip filename_prep.png
Which produces this image:
Combining -flop and -flip just rotates the image 180° around its center, but I can’t help but believe transposing the bits works out better & faster than actually rotating the array & interpolating the result back to a grid. On the other paw, if there isn’t a special case for (multiples of) right-angle rotation(s), there should be. [grin]
The prepared image is 149×159, because the -trim operation removed the surrounding whitespace. You can do that manually, of course, keeping in mind that the corners must be full white to identify the background.
Next: convert that image to a data array suitable for OpenSCAD’s surface() function…
During that ride for apples, we stopped for lunch in the middle of the Walkway where the scenery is a lot better and the traffic much more pleasant than elsewhere along our route:
For reasons that have nothing to do with engineering judgement, the west (right) end of the Mid-Hudson Bridge terminates at a cliff with the road in a monster cut turning abruptly to the right and ramping up to the toll plaza. It’s still a pretty span…
Back in December 2007 I printed four copies of a picture on various papers with the Canon S630 and hung them on a floor joist over my workbench, directly below a fluorescent shop light. Having just hung those screwdrivers where the pictures used to be, it’s time to see what’s happened.
The pictures, scanned on an HP C7670A (aka Scanjet 6300C) against the neutral gray of the ADF platen:
The papers, clockwise from lower left:
While the scanner isn’t renown for its color fidelity, the overall results look about right; the platen really is that shade of gray and the upper-right picture has a sickly green hue.
The faded edges along the right side of the left-hand image show where the adjacent sheet overlapped: the colors didn’t fade nearly as much. The small rectangles on the lower left corners of the right-hand images show where I put clothes pins to keep the sheets from curling.
All of the images have a blue overtone; the magenta dye fades out with exposure to UV from the fluorescent fixture.
As you’d expect, the glossy paper looks best, with very crisp detail. The inkjet paper is next, followed by the matte, and the plain paper in the upper right obviously doesn’t support the ink well at all.
Of course, after five years I no longer have any of those papers and am using entirely different ink…
To show that the scanner really does matter, here’s the same set of images from a Canon LiDE 30:
In both cases. that’s without any color correction / gamma compensation / whatever. I should fish out my scanner calibration targets and go through the whole color calibration dance again; with any luck, the Linux color management infrastructure will be less inadequate by now.
IIRC, we were doing public safety radio at an event at the Dutchess County Fairgrounds with the Mt Beacon Amateur Radio Club. This was before the Diamond antenna mounts disintegrated, too.
Memo to Self: If you love it, don’t expose it to UV.
This looks like a juvenile Cooper’s Hawk, perched high atop that tree. It seems the pair we spotted last year had a successful hatching!
We always wish “our” hawks, whatever and wherever they may be, good hunting…
This came from the first set of real pictures using the repaired Sony DSC-H5 zoomed to 12× with the 1.7× tele conversion lens, cropped down a bit: plenty of artifacts to choose from.
Having extracted the shutter button from the camera body, it’s easy to see why the plunger causes problems:
The plunger is basically a pin that eventually deforms the top of the switch membrane. Tee’s DSC-H1 had an exposed switch, although this picture shows that membrane was still in reasonably good condition:
My DSC-H5 has a thin black protective disk atop the switch, but the disk wasn’t particularly protective and developed a dimple that held the contacts closed even with the shutter button released (which is why I’m tearing the camera apart in the first place):
The C-clip around the plunger is now plastic, rather than metal, making it less likely to erode the thin plastic shaft. Pulling the clip off while holding the button down releases all the parts:
A few measurements from an intact shutter button, which may come in handy if you don’t have one:
Mount three-jaw chuck on the Sherline table, laser-align chuck to spindle, grab shutter button by its shaft in a Jacobs chuck, grab shutter button in three-jaw chuck, release from Jacobs chuck:
That’s not particularly precise, but it’s close enough for this purpose. I used manual jogging while testing the fit with a paper shim until all three jaws had the same clearance, then tightened the jaws.
I nicked the plunger at its base with a flush-cutting diagonal cutter, snapped off the plunger, and drilled a #56 hole through the button:
For reasons that made sense at the time, I repaired Tee’s DSC-H1 with a 1-72 brass screw. This time, I used an 0-80 (which I learned as ought-eighty, if you’re wondering about the indefinite article) screw and nut, because the screw head fit neatly into the bezel recess and I had a better idea of how to smooth out the threads.
This being plastic, I used the chuck to hold the tap in the proper alignment, then turned the tap through by finger pressure. This trial fit showed it worked:
Milling the nut down to a 2.8 mm cylinder required the usual manual CNC, with repeated iterations of this chunk of code in the MDI panel:
#<r>=[[2.8+3.11]/2] g1 x[-#<r>] f50 g0 z0 g2 i#<r> f100 g0 z4
The 2.8 in the first line is the current OD and the 3.11 is the measured diameter of the 1/8 inch end mill. I started from a 5.0 mm OD that just kissed the nut, then worked inward by 0.2 mm at a time for very shallow 0.1 mm cuts:
The alert reader will notice, as did I, that the head isn’t quite centered: the cut trimmed the left side and left the right untouched, with an offset far larger than the centering error. As nearly as I can tell, the heads of those screws aren’t exactly centered on their threaded shafts, but the final result fixed that… and the overall error is a few tenths of a millimeter = maybe 10 mils, tops, so it’s no big deal.
With all that in hand, I applied a very very thin layer of epoxy to fill the threads below the now-cylindrical nut and convert the screw into a rod:
My original intent was to use the screw head as-is atop the PET shield (per those instructions) on the switch membrane, but after reassembling enough of the camera to try that out, it didn’t work correctly: the half-pressed switch didn’t activate reliably before the full-pressed switch tripped.
The PET shield I used came from the side of a 1 liter soda bottle and turned out to be 0.27 mm thick:
I think the PET shield would work with the original plunger shape concentrating the force in the middle of the shield, but the nice flat screw head spreads the force out over a wider area. As a result, the force required to close the half-pressed switch contacts was roughly the same as that required to close the full-pressed contacts; remember the nub on the bottom of the black plastic tray concentrates the force in the middle of the full-pressed switch membrane.
So I removed the PET shield, added a dot of epoxy to fill the screw slot and compensate for the missing shield thickness, then filed a flat to make a nice pad:
Reassembling the camera once more showed it worked exactly the way it should. In fact, the button seems more stable than the OEM version, probably because the slightly enlarged plunger shaft fits better in the bezel. Too bad about those scuffs on that nice shiny button dome, though:
Tossing the leftover parts seems entirely appropriate…
The half-pressed shutter switch position on my Sony DSC-H5 recently stopped working, which seems to be one of two common failures. The other, a broken switch shaft, happened to Tee’s camera, as described there, and I figured I should preemptively fix that while I was inside my camera.
This being a common failure, several folks have described how to dismantle the camera; I followed that guide’s English version.
The DSC-H5 differs slightly from that description. After I got the thing apart, it became obvious that there’s no need to remove the LCD panel, the main control board, and most of the ribbon cables if you have a Philips #0 or #00 screwdriver with a very thin shaft. There’s no way to describe this operation, so take it apart his way, then you’ll see what I mean: the guts can come out as one big lump.
In any event, all the camera controls eventually emerge from the body:
Looking back into the camera body reveals the bottom of the shutter button, captured by a static discharge contact and the gray plastic frame of the Focus / Break button caps:
Removing the pushbutton frame and pushing the left button bezel latch with a small flat-blade screwdriver extracts the shutter button; it falls out of the inverted body. This is one of the few intact DSC-H[1-9] shutter buttons you’ll ever see:
Those rectangular protrusions lock into the slots in the black plastic cap that appears almost silver in this front view that shows the dimple in the switch membrane:
You must remove the cap to release the flex PCB with the shutter switches. Two heat-staked pins retain the cap; a scalpel neatly slices off the melted plastic:
Nota bene: the DSC-H1 button bezel I repaired earlier does not have features that lock into the cap over the switch assembly, which means you can remove and replace it without disassembling the camera. You cannot remove or install the DSC-H5 button without taking the camera apart. I suppose this counts as a continuous product improvement, but …
The shutter switch has two parts:
The bottom of the half-press tray has a small nub that activates the full-press switch, so the force required to activate the half-press switch must be considerably less than the force that activates the full-press switch. This turns out to be a critical part of the repair…
A closeup of the half-press switch with the protective cover sheet (the “damn confetti” of the disassembly instruction) and the dimple that held the contacts together with the button released:
A closeup of the switch through a snippet of PET plastic shows the switch membrane itself is in fine shape:
However, the new plastic shield did not work out well, for reasons having to do with the new button plunger. That’s the next step: rebuild the plunger…
The Smell of Molten Projects in the Morning 