Mary, having had considerable trouble with cutworms in her gardens, routinely deploys cardboard collars around new plants:
Cutworm Collars – assembled
It seems cutworms trundle around until they find an edible plant, chew through the stem and topple the plant, then trundle off without taking another bite. A small cardboard barrier prevents them from sensing the plant: apparently, motivation to climb a short wall hasn’t yet evolved.
Up to this point, Mary applied scissors to tissue boxes, but I proposed an alternative with an adjustable fit to any plant:
Laser Cutting Cutworm Collars
A splayed cardboard box rarely lays flat, a condition enforced by a few MDF stops used as clamps.
Come to find out no two tissue boxes have identical dimensions, even boxes from the same brand / retailer, so lay out duplicates of the collar template to match your stockpile.
When you (well, I) get fussy about angular alignment on the laser cutter’s honeycomb platform, an adjustable stop or two may come in handy:
Laser Honeycomb – Adjustable Pins
That’s a serving suggestion based on a true story, because I really wasn’t all that fussy about precise engraving alignment on those signs.
A more typical situation on a smaller scale:
Laser Honeycomb – Adjustable Pins – engraving
The scrap of MDF with three holes provides angular alignment for the little two-color acrylic test coupon, so you can tuck successive squares into the corner, hammer them with slightly different patterns, then compare the results.
The stops are an off-center hole (the ±3 text gives the offset) in an MDF disk with an acetal post:
Laser Honeycomb – Adjustable Pins – detail
The 3 mm SHCS provides a convenient way to turn the post and disk, so the threading isn’t critical. Sufficiently snug threading will let you turn the screw counterclockwise without loosening it, but that surely depends on how tightly the 8 mm section fits into the honeycomb. The larger top section is 9mm, cleaned up from the rod’s nominal 3/8 inch OD, for a jam fit into the 8.8 mm + 0.1 mm kerf hole.
It turns out that under rare conditions, triggered by fumbling a front derailleur shift, the upper chain section (out of the picture on the top) can whip vertically enough to jam between the Terracycle Idler’s mounting bolt and its longer chain retaining pin:
Tour Easy – Terracycle idler
Whereupon the chain falls off the chainring, jams firmly between the spider and the crank, and brings the proceedings to a halt.
Having finally figured out the cause, I made a simple bushing to fit around the mounting bolt, reduce the gap, and (I hope) eliminate the problem:
Tour Easy – Terracycle idler bushing
Given its rarity, I will need a few more years to verify the solution.
Might get around to cleaning the chain one of these days, too …
A tweak to the air assist plumbing of my OMTech 60 W laser produces much the same result as Russ Sadler’s Super Ultimate Air Assist, with somewhat less plumbing and cheaper Amazon parts:
OMTech Laser – air assist – plumbing
The overall doodle shows the electrical wiring and pneumatic plumbing:
Dual-path air assist diagram
The electronics bay now has two solid state relays:
OMTech Laser – air assist SSRs
The front SSR turns on the air pump when the controller activates the STATUS or AUX AIR outputs; the diode between the (-) terminals acts as wired-OR.
The rear SSR turns on the solenoid valve whenever the AUX AIR output is active. The diode turns on the other SSR to start the pump.
When the laser cutter is idle, both the STATUS and AUX AIR outputs are inactive, so the pump doesn’t run and the solenoid is closed.
The controller has a front-panel AUX AIR button that turns on its eponymous output, which turns on both the solenoid and the pump. I have turned it on to verify the circuitry works, but don’t do any manual cutting. I never was very good with an Etch-a-Sketch and the laser’s UI is much worse.
The solenoid valve must be a “direct acting solenoid valve“, as the air pump produces about 3 psi and cannot activate a “self piloted” solenoid valve. When the valve is open, the pump can push about 12 l/min through the plumbing to the nozzle:
The flow control valve is a manually adjusted needle valve to restrict the engraving air flow to maybe 2 l/min, just enough to keep the smoke / fumes out of the nozzle and away from the lens, when the solenoid valve is closed.
I set the controller to delay for 1 s after activating the air pump to let it get up to speed. There’s an audible (even to my deflicted ears) rattle from the flowmeter when the air assist solenoid opens.
The paltry 12 l/min seems to promote clean cuts and 2 l/min doesn’t push much smoke into the surface around the engraved area.
I cut new shades from vintage clear acrylic sheet, with more aluminized mylar attached to the lower surface: you can barely see the COB LED strip through the reflecting surface.
Depending on how you arrange all the hardware hanging on the nozzle, the shades can collide with something at the home position in the far right corner:
A bit of tinkering suggested I needed a way to repeatably position stock sheets on the honeycomb, so I conjured stops that would be slightly taller than the magnetic spikes:
Improved MDF Honeycomb Spikes – first pass
Three of those form a corner into which you can tuck victims of the same general size:
Improved MDF Honeycomb Spikes – stock alignment
Those pointy MDF spikes should start with slightly rounded tops, because that’s what they’ll look like after a few uses:
Improved MDF Honeycomb Spikes – alignment stops
I also made a low-profile stop for victims lying directly on the honeycomb for engraving:
Please Close The Gate – engraved
The SVG images include a nested version to tile across random MDF leftovers.
The 12 mm neodymium magnet is slightly larger than a single honeycomb cell, so it wants to center itself atop a cell. The stainless steel button head screw sits in the magnet’s countersunk hole and protrudes just enough to make sure the spike doesn’t slide sideways unless you want it to:
Magnetic Honeycomb Spikes – parts detail
A cloud of combustible gas doesn’t pose a threat under there:
Magnetic Honeycomb Spikes – MDF
The thin red beam comes from the targeting laser on the back of the nozzle.
Storage is easy: just smush a handful of the things against the side of the laser cabinet:
Magnetic Honeycomb Spikes – storage
Buy all the parts in lots of 100 to have supplies for other adventures!
The Smell of Molten Projects in the Morning 
