Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Although the OMTech laser controls the laser power supply with a key-lock switch, there’s little visible difference between the OFF and ON positions. Having occasionally mistaken it in both directions, this seemed like a useful addition:
Laser Power Lock Indicator – installed
The strip of black duct tape below the lock muffles the rattle of the triangle hatch key against the metal cabinet.
Two snippets of foam tape hold the knob to the lock cylinder, making an admittedly tenuous connection, but the knob fits around the outside of the switch housing with minimal clearance and doesn’t shouldn’t suffer any torque or pulling, so it might work.
The solid model looks about like you’d expect:
Laser Power Lock Indicator – solid model
Unfortunately, it has no good orientation for printing, so I let PrusaSlicer generate support material inside the knob:
Laser Power Lock Indicator – Support structures
Suffice it to say: removing all that plastic did not go well.
I eventually grabbed the knob in the lathe and bored the interior out to its more-or-less proper dimensions, figuring nobody would ever notice the carnage, and it worked reasonably well. In the unlikely event I need another pointer, I’ll add a support spider to hold up the interior with minimal contact and less plastic.
Yeah, the laser really needs a stack light showing its condition and safety status …
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However, all that upward-directed light goes directly into my glare-sensitive eyeballs, so I added shades above the strips:
COB LED Shade – installed
They’re cut from corrugated cardboard because I have an essentially infinite supply and I’m still working out speeds and intensities. Eventually they’ll become something like black acrylic.
The brackets emerged from the vasty digital deep through the miracle of 3D printing:
COB LED Shade Brackets – slice preview
They’re stuck to the laser cabinet and the cardboard with double-sided duct tape. If you’re careful, they will line up along one edge of the tape, roll over neatly to stick their other face, then a single razor knife cut can separate each pair of neighbors.
The underside sports an aluminized mylar strip to redirect the wasted light in a more useful direction:
COB LED Shade – aluminized Mylar reflector
The tapeless sticky shipped with the laser holds the reflector in place, while its 20 mm width sets the 21 mm shade dimension. Although you want a reasonably smooth layer, it need not be mirror-flat.
Now it’s really bright in there:
COB LED Shade – overview
While I had my head under the hood, I stuck a fourth strip of COB LEDs on the lip along the rear edge of the opening; it’s bright enough to cast the shadow just forward of the laser head despite the OEM under-gantry LED strip. Because the rear strip is aimed downward, it didn’t need a shade.
The perforated cardboard sheet on the left is a spike plate: more about that later.
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What used to be a “light box” had become a “light pad” powered through a USB Micro-B connector on the side. Unfortunately, the pad’s 5 mm thickness allows for very little mechanical reinforcement around the USB jack, while providing infinite opportunity to apply bending force. Over the course of the last half-dozen years (during which the price has dropped dramatically, despite recent events), the slightest motion flickered the LEDs.
So I squished the jack’s metal shell back into shape, found a short right-angle USB cable, and conjured a reinforcing fixture from the vasty digital deep:
LitUp LED Light Pad
The plate fits under the light pad, where a strip of super-sticky duct tape holds it in place:
LitUp Light Pad USB jack reinforcement – bottom
The USB plug fits between the two blocks with hot-melt glue holding it in place and filling the gap between the plug and the pad.
I’d like to say it’s more elegant than the cable redirection for my tablet, but anything involving black electrical tape and hot-melt glue just isn’t in the running for elegant:
LitUp Light Pad USB jack reinforcement – top
On the other paw, that socket ought to last pretty nearly forever, which counts for a whole lot more around here.
The retina-burn orange tape patches on the connector eliminate all the fumbling inherent to an asymmetric connector with invisible surface features. The USB wall wart on the other end of the cable sports similar markings.
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Shortly after acquiring the Greatest ShopVac, I zip-tied half a foot of cardboard tube to the handle to corral the nozzle and keep the ungainly hose from sprawling across the floor. While disembowling the Ottlite into a mini-lathe light, the plastic trim joining the baseplate to the vertical tube cried out to become a nozzle caddy:
ShopVac Nozzle Caddy – front view
It was exactly the right size and shape (by my admittedly slack standards) to hold the nozzle, plus being destined for the trash, so all it needed was a pair of clamp brackets conjured from the vasty digital deep:
ShopVac Nozzle Caddy – solid model
The bosses fit into a tapered slot along what was the rear side, with a pair of 4 mm holes at each end for screws into threaded brass inserts epoxied into the brackets:
ShopVac Nozzle Caddy – clamps mounted
They obviously descend from the many clamp mounts I’ve made for everything from garden hoses to bike running lights. A pair of 4 mm SHCS squish the clamp around the handle, with a strip of electrical tape improving plastic-to-metal griptivity:
ShopVac Nozzle Caddy – side view
The clearance just barely allows a nylock nut atop a washer and you’ll want to trim those 40 mm screws to an exact fit, but it came out pretty well.
The original dimension doodle with some modeling ideas that didn’t survive more thinking:
ShopVac Nozzle Caddy – Dimension Doodle 1
A more detailed doodle with brass inserts instead of the nylock nuts and an aluminum spreader plate that was obviously not necessary:
ShopVac Nozzle Caddy – Dimension Doodle 2
In retrospect, the inserts would make more sense.
The angle doodles convinced me not to bother modeling either the slot’s taper along its length or its mold draft.
Kinda looks like it grew there and makes one wonder why they don’t include a caddy as a standard option.
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A few months of inactivity left the CNC-3018XL table parked in its homed position where the gentle-but-inexorable pressure of the switch lever displaced the foam holding the plastic actuator tab on the X-axis bearing enough that it would no longer operate reliably:
3018 CNC – Y axis endstop
Putting foam tape in a highly leveraged position produces the same poor results as in finance.
The fix requires reorienting the switch so a solid block on the bearing can push directly on the actuator lever:
CNC-3018 X Home Switch – bottom view
The block must curve around the bearing to give the tape enough surface area for a good grip:
CNC-3018 X Home Switch – oblique view
The solid model for the new X-axis mount looks about like you’d expect:
CNC-3018 X Home Switch Mount – solid model
I increased the home switch pulloff to 2 mm, although it’s not clear that will make any difference in the current orientation.
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The top pair of screw heads aren’t quite flush with the cover, so the knobs have 1 mm extensions:
Micromark Bandsaw – cover screw knobs – upper
The bottom pair sit inside 4 mm recesses, so those knobs get matching extensions:
Micromark Bandsaw – cover screw knobs – lower
Attacking an anonymous 5 mm hex wrench with a Dremel cutoff wheel produced a quartet of 12 mm shafts and reduced drawer clutter by one unit.
In retrospect, I should have dismantled the cover, grabbed the screws in a vise with their shafts vertical, and epoxied all the knobs with perfect alignment. Next time, maybe.
A lithium battery management system can (and should!) disable the battery output to prevent damage from overcurrent or undervoltage, after which it must be reset. The inadvertent charge port short may have damaged the BMS PCB, but did not shut down the battery’s motor output, which means the BMS will not should not require resetting. However, because all this will happen remotely, it pays to be prepared.
For this battery, the positive terminal is on the right, as shown by the molded legend and verified by measurement.
A doodle with various dimensions, most of which are pretty close:
Bafang battery – connector dimension doodle
Further doodling produced a BMS reset adapter keyed to fit the battery connector in only one way:
Bafang battery – adapter doodle
Which turned into the rectangular lump at the top of the tool kit, along with the various shell drills and suchlike discussed earlier:
Bafang battery tools
Looking into the solid model from the battery connector shows the notches and projections that prevent it from making incorrect contact:
Battery Reset Adapter – show front
The pin dimensions on the right, along with a mysterious doodle that must have meant something at the time :
Bafang battery – adapter pin doodle
The pins emerged from 3/16 inch brass rod, with pockets for the soldered wires:
Bafang battery – reset tool – pins
The wires go into a coaxial breakout connector that’s hot-melt glued into the recess. The coaxial connectors are rated for 12 V and intended for CCTV cameras, LED strings, and suchlike, but I think they’re good for momentary use at 48 V with minimal current.
I printed the block with the battery connector end on top for the best dimensional accuracy and the other end of the pin holes held in place by a single layer of filament bridging the rectangular opening:
Bafang battery – reset tool – hole support layer
I made a hollow punch to cut the bridge filaments:
Bafang battery – reset tool – pin hole punch
The holes extend along the rectangular cutout for the coaxial connector, so pressing the punch against the notch lines it up neatly with the hole:
Bafang battery – reset tool – hole punching
Whereupon a sharp rap with a hammer clears the hole:
Bafang battery – reset tool – hole cleared
A dollop of urethane adhesive followed the pins into their holes to lock them in place. I plugged the block and pins into the battery to align the pins as the adhesive cured, with the wire ends carefully taped apart.
After curing: unplug the adapter, screw wires into coaxial connector, slobber hot melt glue into the recess, squish into place, align, dribble more glue into all the gaps and over the screw terminals, then declare victory.
It may never be needed, but that’s fine with me.
[Update: A few more doodles with better dimensions and fewer malfeatures appeared from the back of the bench.]
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The Smell of Molten Projects in the Morning 
