Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
The Chimney Swallows block from page 128 of Beyer’s book:
Chimney Swallows – Beyer 128
The tool (blue & orange) and top cut (red) layers:
Chimney Swallows – LB layout
The long radial blue tool lines simplified selecting them when mirroring / duplicating the cut polygons around their symmetries. The orange tool circles aligned various midpoints / vertices / features during construction.
The inward curve along the outer edge started as a triangle with a node at about the middle of the curve. Deleting that node left the remaining two sides overlapped, but dragging one of them to match the curve worked OK. There’s probably a better way.
That curve defines the outer edges of the shapes along it, so I drew polygons from the corner intersections and dragged the outer edge to match the curve at high zoom.
The shape remains selected after dragging the side, which meant I could immediately apply a 1 mm inset to create the cut lines.
To my surprise, the swallow bodies are straight-sided polygons!
After taking advantage of all the symmetries, knock out the shapes defining each layer:
It looks more like flowers than fireworks to me, but there’s no accounting for taste.
Deploy enough 2 mm circles to catch the flower’s radial symmetry:
Pyrotechnics – LB layout
During the process of building the layout, a big circle positioned the cups at the base of the flowers, another delineated the joint between the cups and the petals, and more little circles caught the intersection of those circles with the petals. All that was for visualization and positioning, as you only draw one flower shape, then duplicate it around the pattern.
Although the cups and petals are surely circular arcs, it’s easier to draw a closed line triangle around the intersections, then pull the midpoint of a line into an arc (Bezier curve!) matching the pattern Closely Enough™ at high zoom. Because the arcs end at the intersection points based on circular arrays of points, they’ll all match up when they’re duplicated around the pattern; in fact, you need only one side of one petal, mirror it around the midline, and away you go.
Then the magic happens:
Pyrotechnics – LB tool insets
Which is easier to see without the original shapes:
Pyrotechnics – LB insets
Pick one of the closed shapes, apply the Offset tool to shrink it by 1 mm, duplicate as needed, and you get the outlines of the regions to cut with 2 mm between them. Plunk those shapes on a cutting layer, add the outer frame with locating holes for the fixture, and it’s ready to cut the top layer from black paper:
Pyrotechnics – LB cuts
Knock out the cuts for each sheet of paper in the stack:
Pyrotechnics – LB paper cuts
Then Fire The Laser™:
Layered Paper – Pyrotechnics – Beyer 132
That was a nearly random selection of colors, but it’s hard to go wrong.
This seemed like an appropriate use for the stack (well, several stacks) of colored paper I’ve accumulated over the years.
The illustration in the book is apparently a photograph of a quilt block Beyer put together, so I had to reverse-engineer the Platonic Ideal Block from the image:
Mariners Compass – minimal shapes – LB layout
Fortunately, after a bit of fiddling around, I could take advantage of the radial symmetry to duplicate most of the fundamental shapes, so producing the layout really wasn’t all that difficult:
Mariners Compass – LB layout
The blue tooling lines (upper left) run along the centers of what would be seams in a fabric block, with 2 mm circles defining the endpoints for ease in snapping the lines.
This being the first block I attempted, I did it all wrong. LightBurn can form the convex hull over a group of shapes, so I just selected pairs of circles, created the hull, and iterated for the minimal shapes required to generate the whole design. That produces the basic layout, but what you really want is the collection of shapes between those hulls that define the actual cutouts, which appears in the lower left image.
Don’t do it that way, as explained tomorrow with a different block.
With all the shapes in hand, you duplicate them for all the paper layers you need, removing the shapes corresponding to the color of each sheet. Sheets lower in the stack have fewer cutouts, with the pattern in the lower right being second from the bottom.
The four holes in the corners fit over rivnuts in a fixture aligning the sheets in a tidy stack:
Layered Paper – alignment fixture
Yes, that’s a blooper sheet.
All in all, it’s easier than I expected to get nice results.
Fiskars cutting mats must lie flat on the table to be of any use, but they’re remarkably sensitive to warping due to localized temperature variations; a hot cup of tea can wreak a remarkable amount of damage. Suggestions from the InterWebs generally involve a clothes iron, temperature tweaks, overnight cooling, and unpredictable results.
Given that the mats are large polypropylene sheets, I figured applying moderate heat to the entire mat while it’s compressed between two flat plates would work better:
Fiskars cutting mat – solar flattening
That’s one of Mary’s 36×24 mats atop an MDF sheet (with pictures of wood laminated to both sides), under a 7/32 inch = 5.6 mm sheet of non-tempered glass, with a maple shelf supporting the last two inches of the unwarped edge, all sitting on the driveway in full sun.
The first attempt started too late in the afternoon for good heating and, after a few hours, had only slightly reduced the warp. Laying it out the next morning got the mat up to about 110 °F = 43 °C around noon and the warp was completely gone by evening.
I don’t trust the IR thermometer’s temperature measurements on glass, but the surrounding MDF and driveway were plenty hot.
The next sunny day flattened the warp out of 24×18 inch mat on my desk, so success wasn’t a fluke.
We noticed that the larger mat is now uniformly smaller by about 3/16 inch along the 36 inch width and 1/4 inch over the 24 inch height. It was a tag sale find with unknown provenance and, due to the warp, Mary had been using her other large mat for layout, so we don’t know if this one arrived a little short or if my technique both flattened and shrank it.
The smaller mat seems unaffected by its similar treatment, so your mileage may vary.
In any event, a flat mat is much more useful than a warped mat, so we’ll call the operation a success.
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.
Long ago, I gave Mary a box of 100 empty bobbins for her Kenmore 158 sewing machine, with the intent she would never again have to unwind a bobbin to put new thread on it. This worked so well I did the same thing for her Juki, with the result she needed somewhere to store all those filled bobbins.
Her work table has a shallow drawer, so we tried this out:
Watching all those little rectangles fall out just never gets old:
Bobbin Storage Case – cutting detail
I ran off a test tray in ordinary chipboard that works just as well, but lacks the pleasant appearance and feel of the TroCraft. Clear 1.5 mm acrylic would probably work, at the cost of requring a much neater glue job where the dividers meet the walls.
The spacing is a bit tight to pluck a bobbin from its slot between two others, but now she has enough space to arrange them as needed, with empty spaces around the most-used colors. I offered to carpet the drawer with bobbin trays, but she suggested waiting until these fill up.
The Smell of Molten Projects in the Morning 