Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
The knuckle joint on the Dirt Devil stick vacuum failed, so it followed us home instead of leaping into the trash:
Dirt Devil – broken swivel joint
Although the fitting seems to be made of ABS, it’s now missing major chunks of plastic in the high-stress areas, so rebuilding it seems not worth the effort.
Because we don’t have any carpets and this one will never leave the basement, I extracted the carpet beater brush and its motor, only to find Yet Another Example of poor assembly practices:
Dirt Devil – stray strands
It’s a 12 V (-ish, I didn’t measure whatever comes out of the vacuum head) DC motor and those errant strands aren’t quite long enough to meet in the middle. The yellow rectangle is a thermal fuse that would be shorted out if the strands were a bit longer.
The broken joint lets the head swivel from side to side, but the elevation joint is still good. If I don’t expect too much, the thing might still suffice for extracting dust from under the benches:
Dirt Devil – taped joint
Worst case, I can swap in a classic floor brush using one of the adapters I made a while ago:
Dirt Devil adapters – assembled
That was easy, if only because I skipped the hard part …
It’s more properly called a “chain guide” and is basically a shifter cage minus the mechanism:
Chain Catcher – side view
Because the Tour Easy frame has a 25 mm tube where the guide’s clamp expects a minimum 31.8 mm tube, a 3D printed adapter fills the gap:
Chain Catcher adapter ring – solid model
The hole is off-center because it seemed like a good idea, although it’s not strictly necessary. The flange helps align the pieces while tightening the clamp screw.
The guide cage clears the chain on all sides while up on the work stand, but there’s nothing like getting out on the road to find out why something doesn’t work as you expect.
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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.
Putting the entire fixture layout onto a tool layer produces a template to align the text on the sticks:
Craft Stick Plant Markers – fixture layout
The rectangles mark where you put cut layer rectangles around the text in each stick. The sticks are 18 mm wide, so a 10 mm cutout leaves what should be enough wood along the edges. The rectangle length is a serving suggestion, as you must adjust the cut rectangle to fit the text.
Group everything except the four targets into a single object so you won’t inadvertently move only a part of it. The targets must remain separate to work with the Print-and-Cut alignment. With that set up, Lock the position of the entire layout to prevent you from moving any part of it.
Starting with a blank tag in the template:
Craft Stick Markers – LB template – base
Draw a rectangle in a cut layer to match the template, which is easy if you have Object Snap set up properly:
Craft Stick Markers – LB template – rectangle
Add your text in a chunky font like Fira Sans Condensed Heavy, set to 15 mm tall with 5 mm horizontal spacing:
Craft Stick Markers – LB template – lowercase text
LightBurn aggressively snaps a new text cursor to the nearest pre-existing text, so you may be forced to click far away from where you want to place the text, type the text, then move the finished string. LightBurn will also snap the text to the display grid as you drag it around, so hold the Ctrl key down to disable snapping while you eyeball the proper alignment with the rectangle. Leave about 2 mm between the left edge of the rectangle and the first letter to make an easily visible space.
Although you can use lowercase letters, uppercase letters have the compelling advantage of being attached both top and bottom, so retype the text if you forgot about the Caps Lock key:
The 15 mm font height I’m using seems to be the overall maximum from the top of the tallest letter to the bottom of the lowest descender, not the height of any specific capital letter, all of which extend beyond the cut rectangle by about half a millimeter. That’s crucial to make this thing work, so tune the font and its height appropriately.
Select the text string when you have it properly aligned:
Craft Stick Markers – LB template – text selected
Hit Ctrl-D to duplicate the text, tap the ↑ (Up) arrow key to move the copy out of the way, and set it to the fill layer.
Now the magic happens.
Select the rectangle, Shift-select the text, and Boolean Subtract (Alt minus) the text from the rectangle:
Craft Stick Markers – LB template – subtracted text
Realize that you have screwed up by not shortening the right side of the rectangle to leave about 2 mm of open space. Bang on Ctrl-Z to undo the last step, shorten the rectangle, Shift-select the text again, then subtract the text from the rectangle:
Craft Stick Markers – LB template – properly subtracted text
Select the filled copy and whack the ↓ (Down) arrow key to move it back over the cut layer:
Craft Stick Markers – LB template – overlaid text
Now the filled layer will toast the characters to a nice brown and the cut layer will remove the background rectangle.
After finishing the text dance for all the markers, the template should look something like this:
Craft Stick Markers – LB PnC layout
The cheerful circles come from LightBurn’s Print-and-Cut Wizard aligning the template with the fixture holding the craft sticks on the laser platform, about which more tomorrow.
The Smell of Molten Projects in the Morning 
