By turns: tinker, engineer, husband, author, amateur raconteur, recumbent cyclist, father, ham radio geek. So many projects, so little time!
I set up an orthotic shoe insert on the MPCNC and unleashed the Z-Axis height probe on it:
In principle, the grid keeps the object aligned with the machine axes and the blocks put the upper surface more-or-less parallel with the platform. The XY origin, at the G28 location I’ve been using for tool changes, is on the midline of the sole, with Z touched off by probing the platform beside the sole.
The only interesting part of the orthotic is the rigid white plastic plate, which extends about 20 mm into a pocket in the black foam, so the probe area excludes the bendy part.
I’m abusing the bCNC Auto-level probe routine to get the height map, because it produces a tidy file of XYZ coordinates with three header lines describing the overall probe area:
-50 140 39 -50 50 21 -2 35 500 -50 -50 0.11 -45 -50 0.06 -40 -50 0.005
The first two lines give the X and Y coordinate ranges and number of samples. The third line is the Z axis range and probe speed (?). After that, it’s just probed XYZ coordinates, all the way down.
Meshlab can import ASC files consisting of XYZ coordinates, with the ability to skip a specific number of header lines:
If you don’t skip those three lines, then you get three additional points, far off in XYZ space, that will confuse the next step.
Checking the Grid Triangulation box (the default) produces a nicely lofted sheet:
It is, however, a single-sided sheet, not a manifold 3D object. After a few days of screwing around, I’m unable to find any (automatic, reliable, non-manual) way to solidify the thing in Meshlab, so just save it as a PLY file in ASCII format:
Import it into Meshmixer, Ctrl-A to select the whole thing, click (Select →) Edit → Extrude, pick Y-Axis and Flat EndType, then extrude a convenient base in the negative direction:
For whatever reason, some 3D programs show machine-tool coordinates with Z pointing upward and others aim the Z axis at your face. Both must have made sense at the time, because Meshmixer defaults to swapping the Y and Z coordinates on import / export.
The Density slider controls the number of generated faces in the extruded section, so tune for best results.
I have no idea what Harden does.
Accept the result and you have a solid object suitable for further modeling.
The Poughkeepsie Library makes a 3DSystems Sense scanner (V1) available to patrons and, after a bit of to-and-fro, I managed to get a not-awful scan of Mary’s right leg:
This was accomplished under field conditions in a cramped room hosting a Spanish-language “introduction to computers” class. We propped her leg across the edge of a table with her sock as a cushion.
The depth image resolution seems to be 1 mm and the software attempts to stitch multiple views from different angles into a consistent 3D model. The scanner requires a steady hand and a steady model to successfully glue new data onto the existing model; what seem small misalignments derail the matching.
The software has several presets, of which “Head” produces the best results. I have no idea what the algorithm thinks of her foot; maybe it’s been trained on some truly ugly faces.
Exporting the solid model as either STL or PLY allows import into (Windows-only) Meshmixer, wherein I sawed off the pieces we won’t need:
If only I had a foot fetish …
The 3DSystems software requires a fairly specific Windows 8 (or 10, which is so not happening) + Intel hardware configuration, which recently arrived as a $250 off-lease Dell Latitude 7250 laptop. It works fine through VNC, so I can use it from the Comfy Desk.
However, using a 3D scanner in your own home isn’t actually private:
3D Systems may also automatically collect and report back to 3D Systems information about the Software and Licensee’s usage along with limited information about the Device, 3D Printer, and/or other third-party applications. If 3D Systems implements automated data collection practices then Licensee may opt out of providing such data if Licensee has a license that authorizes Commercial Use.
Oh, and then you must activate the software before using it. The library IT folks tell me I can install & activate the scanner on my system without derailing their setup. I have my doubts, but we’ll see how it goes.
Posted in Photography & Images on 2019-10-15
Fortunately, Brown Marmorated Stink Bugs haven’t been as catastrophic as predicted when they arrived a few years ago, perhaps because native critters have learned to deal with them:
Looks like a week’s worth of spider chow!
For reasons not relevant here, we recently decontaminated a second lift chair, this one in bariatric size (so it doesn’t suffer from fuzz-shaving struts) with a six-switch control pod:
The green LED-lit buttons were so bright I took it apart to see what could be done; the picture shows the considerably dimmed result.
Start by prying outward on the tab at the USB charging port:
Done right, you can then release the latches along the sides:
It’s impossible to photograph the PCB with the LEDs active, but here’s what it looks like without power:
The eight (!) SMD LEDs align with light pipes around the switch openings:
The black dots come from Sharpie ink daubed in the shallow recesses intended to nestle around the LEDs. Note that the four switch caps have unique keying, so you can’t put them back incorrectly without some effort.
While we’re inside, here’s a closer look at the cable entry point, just in case I must replace the industrial-strength coily cord:
Unfortunately, it has a five-conductor cable, so a cheap phone coily cord (remember when phones had coily cords?) won’t suffice.
The PCB sports a pair of PICs, one of which seems to handle the buttons. I betcha the cable dates back to the days of hard-wired power switches, with the PIC now handling the intricate logic of deciding which motors to actuate for each function, then controlling MOSFETs as fake switch contacts.
The other PIC snuggles against the USB interface, which the manual describes as a charging-only port. It might also serve as a programming interface for the main PIC; admittedly the notion of a firmware upgrade for a lift chair seems far-fetched.
Reassembly is in reverse order with a resounding snap at the conclusion. It works fine and you (well, I) can now look at the control pod without sunglasses.
Posted in Administrivia on 2019-10-10
Several home projects of steadily increasing priority will interfere with writing up Basement Laboratory projects through early November:
- No barnacles on her foot
- No sea creature eating her leg
I’ll be posting infrequently during the next few weeks.
All remains right with our world …
I picked up a pair of Raspberry Pi V1 cameras, both of which arrived unstuck to their breakout board:
Requiring the customer to peel off the white layer and stick the camera to the PCB helps keep costs low. They’re $4 if you’re willing to wait two months or $7 from a “USA Seller”.
Apparently, “porcelain chip fix” epoxy survives about a year in a bathroom sink:
It came loose from the drain rim while I was cleaning the sink; I wasn’t doing anything particularly vigorous.
The stain in the lower right goes all the way around the epoxy:
For what should be obvious reasons, I was loathe to scuff up the sink surface to give the epoxy a better grip, so it couldn’t make a watertight seal all the way around.
A closer look at the stain:
I’m reasonably sure that’s iron bacteria colony, rather than actual rust, as there’s no iron to be found anywhere nearby.
For lack of anything smarter, I’ll apply another dose of the same epoxy, although this time I won’t be expecting a long-term fix.