Cutting or engraving patterns on earrings should go more smoothly with a fixture:
Earring fixture – demo install
That’s a serving suggestion, using the Biohazard test pieces, which also helped align the top and bottom layers while gluing:
Earring fixture – clamping
That used all my little clamps: obviously I need more!
The bottom layer (red) is MDF for strength and the top layer (orange) is chipboard because that’s all it needs:
Earring fixture – LB layout
The little tab along the top ensures alignment using the jump ring cutout. The central hole will let me cut through the earring, should that be necessary.
The two strips over on the left get glued on the bottom, spaced to align along one of the aluminum knife blade rails, as with the craft stick fixture. With that lined up, any two of the four targets will serve to align the template with the fixture using LightBurn’s Print-and-Cut tool, as with the craft stick template.
That’s built directly from the original specs to get the spacing and symmetries correct. The freebies I could find all suffered from various degrees of bad design & layout.
Shrunken down to 25 mm OD, the tips become vanishingly small:
Biohazard earring – vinyl sample
It’s the same laser-safe polyurethane vinyl as the SD card reader, this time applied to 3 mm black acrylic. The “gold” ring is just parked in place, as this one wasn’t presentation-quality.
Contrary to the usual transfer-tape method of applying PSA vinyl, I stuck the sheet to the acrylic before cutting, then weeded it directly off the acrylic:
Biohazard earring – vinyl weeding
Kiss-cutting the vinyl with dot mode ate into the acrylic, but the soon-to-be-weeded areas protected the surroundings and the result came out looking pretty good. To me, anyhow.
Flushed with success, I tried some almost certainly not laser safe glow-in-the-dark tape:
Biohazard earring – GITD weeding fail
The mess in the upper left is the tape’s double-sided adhesive intended to hold the glowy layer in place forever. Of course it weeded poorly!
Seen in its natural environment, however, weeding may not be necessary:
Biohazard earring – GITD tape glow
Engraving the rebated rim leaves quite a bit of debris & scorch marks around the perimeter. A mask layer atop the GITD tape seems like a Good Idea™.
Our Young Engineer knits during rare moments of downtime and sketched an idea for stitch counters to mark progress between those moments. There being nothing like a new project to take one’s mind off all of one’s previous projects:
Stitch Counters – overview
These are more along the lines of feasibility / material tests than finished products, so you’ll see plenty of rough edges.
Prior to doing this, we agreed that 3 mm material was probably too thick, particularly given the small scale: the hexagons are 10 mm edge-to-edge with a 1.5 mm hole for the jump ring.
The jump rings are (mostly) 8 mm OD, which may or may not be the right diameter for all possible knitting needles.
The count sequence goes 10 20 10 40 50 10 with alternating colors:
Stitch Counters – red and blue
Those came from 3 mm red and blue transparent acrylic, looking entirely too much like candy. Cutting two identical layouts from two different materials, then swapping a few counters, gives me two related-but-different sets. This idea is also subject to revision.
I like the set of 3 mm acrylic mirror counters colored with Sharpie:
Stitch Counters – mirror
Alas, the unprotected mirror backing won’t survive long in the real world and Sharpie ink tends to stress-crack the acrylic. Bonding a thin colored sheet / gel filter to the back with an adhesive sheet in between would work, although I don’t look forward to the fiddly alignment. Bonus: sticky edges are a nonstarter in this application.
A setup error produced a set of unmarked counters that might still come in handy for something:
PXL_20230507_150124595 – Stitch Counters – blue blank
Trolase acrylic 1/16 inch = 1.5 mm sheets produce the most visible legends, in a relentlessly industrial sort of way:
Stitch Counters – Trolase
Those have a single thin layer atop a white or black base sheet, but three-layer 1.5 mm Trolase sheets with matching top and bottom colors (cladding on a white core) would look better.
If you can’t decide on a color, go clear:
Stitch Counters – clear
All of those appear on a background of some thin DIY plywood:
Stitch Counters – veneer plywood sheets
The bottom sheet is very pale veneer that came with a layer of genuine 3M 468 transfer tape with 200MP adhesive. I stuck three different veneers on three 100×50 mm rectangles of the stuff to make 1.5 mm thick “plywood”. The adhesive sheet provides lateral strength, not the wood fibers, so it’s not quite as easy to tear as the broken fragment would suggest.
The results look passable, although there’s room for improvement:
Stitch Counters – veneer plywood
After engraving & cutting, I slathered them with clear polyurethane finish and hung them up to dry:
Stitch Counters – wood finish curing
I like the effect, but using the pale veneer for the bottom layer made them look identical from that side. Worse, two of the three top layer veneers had nearly identical colors (one has more grain) after the finish cured.
More thought seems in order, but at least I’ve explored some of the solution space.
When the chain falls off the top of the chainring toward the motor, the part remaining engaged with the chainring will inevitably drag the rest into the gap between the motor and the chainring spider, whereupon it will jam firmly in place and be almost impossible to extract. Preventing this means filling the gap, which required several iterations:
Bafang motor gap filler – prototypes
The Bafang motor has a cover held in place by seven M3 flat-head screws, shown here below a test filler using pan head screws:
Bafang motor gap filler – installed
Contrary to what you might think, the five screws that obviously sit on five points of a hexagon do not in fact sit 60° apart. How you find this out is by making the obvious layout, including the two screws bracketing the pinion gear in the lower right, then applying windage:
Bafang motor housing gap filler – hole adjustments
That’s one of the paper templates seen above, with laser-cut holes 60° apart and ugly holes punched at the actual screw locations. Then you scan and overlay that image with the LightBurn layout and twiddle the hole locations to make the answer come out right:
Bafang motor housing gap filler – hole adjustments – LB overlay
With that in hand, I cut a 1 mm acrylic shape to measure the clearance between the motor + filler and the chainring spider, with pan-head screws replacing the original flat-head screws:
Bafang motor gap filler – top view
That’s a single piece of 2.5 mm acrylic I used after discovering a pair of the 1 mm acrylic shapes fit with space to spare: hooray for rapid prototyping.
A test chain drop suggested it might suffice:
Bafang motor gap filler – test
If I were so inclined, 3 mm acrylic with countersunk holes and slightly longer flat-head screws would probably work, but I’ll use this until it fails to prevent a chain snag.
The careful observer will have noted the stress crack extending radially inward from the upper-right screw, which I am carefully avoiding doing anything about, pending the aforementioned failure.
My OMTech 60 W laser cutter has a stepper motor Z axis drive that has worked flawlessly since it arrived. However, it recently developed a periodic klonk during autofocusing and manual jogging, loud enough to shake the platform and rattle the cabinet’s bottom plate.
A few minutes of poking around revealed the klonk happened on each turn of the Z axis leadscrews, which quickly led to finding the cause:
Craft Stick – swarf in belt drive
It’s a rectangular wood chip, perfectly sized to jam into the Z axis motor pulley driving the belt: a belt tooth lifts up on the chip as the pulley turns, then klonks as it slips off the other side. The motor pulley and all four leadscrew pinons have the same number of teeth, so they’re all at the same point in their rotation when the belt slams down onto the pulley.
Where might such a thing come from? Well, I recently finished a batch of plant markers and hadn’t yet cleaned out the “chip tray” which is also just the bottom plate of the cabinet:
Craft Stick – swarf
I briefly considered building a guard for the motor pulley, but the belt most likely carried it from elsewhere. The leadscrews have an ample coating of grease that was also smeared elsewhere on the cabinet, making the belt sticky enough to catch such things.
The chip tray is once again pretty clean and the platform behaves normally again.
Jog the laser to the upper-right target on the fixture, click the upper-right target in the template, and tell P-n-C that’s the First Target. Jog to the lower-left target, click the lower left target, and that’s the Second P-n-C Target:
Craft Stick Markers – fixture target detail
The colored circles indicate the targets on the template:
Craft Stick Markers – LB PnC layout
Select the Align No Scaling option, because the template and the fixture are exactly the same size.
Click-n-drag to select the entire template (because you should always use Cut Selected Graphics), then frame it Just To Be Sure. The red dot pointer (or whatever you use) should kiss the fixture’s perimeter all the way around.
Make sure the fill layer happens before the cut layer, then Release The Laser:
Craft Stick Markers – engraving
The cut layer trims around the engraved letters to leave them standing in the rectangle:
Craft Stick Markers – cutting
Some of the smaller bits won’t fall out as they’re cut, but a sharp thwack ejects them easily enough.
Producing a set of ten sticks takes maybe seven minutes:
Craft Stick Markers – fixture second fill
Because craft sticks aren’t intended for fine woodworking, don’t expect consistent engraving results:
Craft Stick Markers – wood engraving difference
Applying a finish would definitely improve their appearance, but most such chemicals don’t belong in an organic vegetable garden.
The Smell of Molten Projects in the Morning 
