Posts Tagged M2
A new spool of retina-burn orange PETG snagged when the takeup guide let the filament fall off the inboard side and the extruder tightened the loops around the spool holder. I carefully unwound the loops without removing the spool to ensure I didn’t introduce a crossover, scraped the bird’s next off the platform, and restarted the print.
After undoing the second snag, I added a crude spool sidewall:
It’s decidedly unlovely, but I was in a hurry to get a PCB holder printed and ready for use. Worked perfectly!
I’ve rarely had a problem with any other spools and I don’t know what’s new-and-different with this one.
One of the cold shoe mounts I made for the photo lamps cracked:
It’s done in PETG with my more-or-less standard two perimeter threads and 15% 3D honeycomb infill, which is Good Enough™ for most of my parts. In this case, there’s obviously not nearly enough plastic in there!
Redoing it with three perimeters and 50% infill should improve the situation, even though it looks identical on the outside:
I didn’t replace the other mount. If it breaks, it’ll get the same 50% infill as this one. If this one breaks, I’ll try 75%.
An easy fix!
Although the bCNC GUI has conspicuous Run / Hold buttons, it’s easier to poke a physical switch when you really really need a pause in the action or have finished a (manual) tool change. Rather than the separate button box I built for the frameless MPCNC, I designed a chunky switch holder for the CNC 3018XL’s gantry plate:
The original 15 mm screws were just slightly too short, so those are 20 mm stainless SHCS with washers.
The switches come from a long-ago surplus deal and have internal green and red LEDs. Their transparent cap shows what might be white plastic underneath:
I think you could pry the cap off and tuck a printed legend inside, but appropriate coloration should suffice:
Making yellow from red and green LEDs always seems like magic; in these buttons, red + green produces a creamy white. Separately, the light looks like what you get from red & green LEDs.
The solid model shows off the recesses around the LED caps, making their tops flush with the surface to prevent inadvertent pokery:
The smaller square holes through the block may require a bit of filing, particularly in the slightly rounded corners common to 3D printing, to get a firm press fit on the switch body. The model now has slightly larger holes which may require a dab of epoxy.
A multi-pack of RepRap-style printer wiring produced the cable, intended for a stepper motor and complete with a 4-pin Dupont socket housing installed on one end. I chopped the housing down to three pins, tucked the fourth wire into a single-pin housing, and plugged them into the CAMtool V3.3 board:
The CAMtool schematic matches the default GRBL pinout, which comes as no surprise:
The color code, such as it is:
- Black = common
- Red = +5 V
- Green = Run / Start (to match the LED)
- Blue = Hold (because it’s the only color left)
The cable goes into 4 mm spiral wrap for protection & neatness, with the end hot-melt glued into the block:
The model now includes the wiring channel between the two switches, which is so obviously necessary I can’t imagine why I didn’t include it. The recess on the top edge clears the leadscrew sticking slightly out of the gantry plate.
The LEDs require ballast resistors: 120 Ω for red and 100 Ω for green, producing about 15 mA in each LED. Those are 1/8 W film resistors; I briefly considered SMD resistors, but came to my senses just in time.
A layer of black duct tape finishes the bottom sufficiently for my simple needs.
A doodle giving relevant dimensions and layouts:
I originally planned to mount the switches on the other gantry plate and sketched them accordingly, but (fortunately) realized the stepper motor was in the way before actually printing anything.
The OpenSCAD source code as a GitHub Gist:
It seems bCNC doesn’t update its “Restart Spindle” message after a tool change when you poke the green button (instead of the GUI button), but that’s definitely in the nature of fine tuning.
The solid model looks about like you’d expect:
The “camera” actually has the outside dimensions of a Spigen case, rather than the bare phone, because dropping a bare phone is never a good idea.
The base plate pretty much fills the M2’s platform:
I originally arranged the four corners around the plate to print everything in one go, but an estimated six hours of print time suggested doing the corners separately would maximize local happiness. Which it did, whew, even if the plate ran for a bit over 4-1/2 hours.
The snout is a loose fit around the 5× widefield microscope eyepiece, with the difference made up in a wrap of black tape; it’s much easier to adjust the fit upward than to bore out the snout. An overwrap of tape secures the snout to the eyepiece, which I’ve dedicated to the cause; the scope normally rocks 10× widefield glass.
The tapered hole exposes the phone’s fingerprint reader to simplify unlocking, should it shut down while I’m fiddling with something else.
The microscope doesn’t fully illuminate the camera’s entrance pupil at minimum zoom, with 4.5× filling the screen and (mostly) eliminating the vignette. The corner blocks have oversize holes to allow aligning the camera lens axis over the microscope optical axis. The solid model incorporates Lessons Learned from the version you see here, because you (well, I) can’t measure the camera axis with respect to the outside dimensions accurately enough:
Although it’s less unsteady than it looks, microscopy requires a gentle touch at the best of times. The adapter doesn’t add much wobble to the outcome:
The field is about 14×19 mm with the camera at 4.5× and the microscope at minimum zoom:
You can see a little darkening on the upper and lower right corners, so the phone’s still minutely leftward.
The field is about 1.5×2 mm at full throttle:
The OpenSCAD source code as a GitHub Gist:
A reproduction circular slide rule from the mid-1960s may not be the cutting edge of consumer demand, but the pen version of a Tektronix Circuit Computer came out pretty well:
A Bash script compiles the GCMC code with eight different parameter combinations to produce pairs of G-Code files to draw (“engrave” being aspirational) and cut (“mill”, likewise) the three decks and the cursor.
Better paper definitely produces better results, so I must rummage through the Big Box o’ Paper to see what lies within. Laminating the decks improves their durability and matches the original Tek surface finish.
Setting the XY origin to dead center on each deck requires carefully calibrating the USB video camera, with the end result accurate to maybe ±0.1 mm around the entire perimeter. Both machines move equal linear distances along both axes, which was definitely comforting.
Having made half a dozen cursors from various bits of acrylic, none of which look particularly good, demonstrates my engraving hand is too weak for a complete slide rule:
With logarithmic scales in hand, however, adapting the GCMC source code to produce general-purpose circular slide rules with only two decks and smaller diameters may be the way to improve my engraving-fu, as a full-scale Tektronix Circuit Computer would chew up three square-foot plastic sheets.
A general-purpose slide rule would need multi-color (well, at least bi-color) labels and digits for red “inverse” scales to remind you (well, me) they read backwards. Some slipsticks use left-slanting italics, left-pointing markers (“<2”), or other weirdness, but they’re all different.
An early small-scale version engraved on ABS came out OK, modulo poor ink fill:
Engraving the decks on hard drive platters doesn’t count:
All in all, it’s been an interesting exercise and, as you may have guessed, will become a Digital Machinist column.
The GCMC and Bash source code as a GitHub Gist:
Our Young Engineer’s Tour Easy followed us home, due to a non-survivable cycling commute and inadequate apartment storage space. What with its Zzipper fairing being off and having easy access to the strut, I conjured & installed another set of fairing mounting blocks:
Should you be in need of a Tour Easy recumbent in good shape, well, have I got a deal for you. I’ll even conjure a Daytime Running Light mount, if that’s what it takes …
Along the same lines as the MPCNC pen holder, I now have one for the 3018:
The body happened to be slightly longer than two LM12UU linear bearings stacked end-to-end, which I didn’t realize must be a constraint until I was pressing them into place:
In the unlikely event I need another one, the code will sprout a
max() function in the appropriate spot.
Drilling the aluminum rod for the knurled ring produced a really nice chip:
Yeah, a good drill will produce two chips, but I’ll take what I can get.
There’s not much left of the original holder after turning it down to 8 mm so it fits inside the 12 mm rod:
Confronted by so much shiny aluminum, I realized I didn’t need an 8 mm hole through the rod, so I cut off the collet shaft and drilled out the back end to clear the flanges on the ink tubes:
I figured things would eventually go badly if I trimmed enough ink-filled crimps:
The OpenSCAD source code as a GitHub Gist: