Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
AFAICT, the Makergear M2’s filament drive gear has been in the same place on the motor shaft since I set it up nearly five years ago:
Makergear M2 – original filament drive pulley position
The filament rides along the white trail close to the front of the gear. This worked fine with PETG, but TPU occasionally squeezed out through the small gap toward the front of the extruder, so I moved the gear a few millimeters forward:
Makergear M2 – improved filament drive pulley position
The track on the idler bearing shows the filament is neatly centered where it should be:
Makergear M2 – filament idler bearing position
I haven’t adjusted the spring pressure on the idler, but it’s probably too high for TPU. If it continues to work, I’ll continue to do nothing.
I wanted to align the magnetic base plate first, but it has a lot of magnets and steel tools just weren’t going to work:
MakerGear M2 BuildTak – FlexPlate magnets
So I put the BuildTak FlexPlate on top and deployed the taper gauge, with all the magnetic fields held safely inside the steel sheet below the surface:
MakerGear M2 BuildTak – taper gauge
The plate turned out to be mostly flat, with two high spots at the center front and back. A few strips / layers of Kapton tape raised the lowest spots along the sides and middle enough to get the whole surface Close Enough™:
MakerGear M2 BuildTak – FlexPlate shims
That’s really thick 4 mil = 0.1 mm tape, not puny 1 mil stuff. Two layers added enough height to very slightly warp the steel plate when held down by all those magnets.
The final result was flat within ±0.05 mm across the entire plate, with those two high spots reduced to +0.2 mm.
The high spots lie outside the skirt at the front & rear of the plate, where they should be easy to avoid with most models I can imagine building in TPU. Stipulated: I have a stunted imagination.
TPU boxes are bendy little things with 0.45 mm walls:
MakerGear M2 BuildTak – test square
After I got the plate flattened, even a single-thread wall of TPU sticks to BuildTak like it was glued there.
I had PrusaSlicer print them sequentially to avoid excessive back-and-forth, although combining 2 mm Retraction with Avoid crossing perimeters has eliminated much of the previous stringing:
Terracycle Chain Idler Tire – TPU stringing
I modified the startup G-Code to purge & wipe the nozzle at the right-front corner of the plate:
MakerGear M2 BuildTak – nozzle cleaning
If I’d done that at the start, the BuildTak surface wouldn’t have a small divot melted into the center front edge where the previous G-Code paused the nozzle at the edge of the glass plate while heating. Pausing a millimeter off the diagonal seems to isolate the hot nozzle from the plastic surface.
The revised startup G-Code, with the earlier clearing motions commented out:
;-- PrusaSlicer Start G-Code for M2 starts --
; Ed Nisley KE4NZU
; Makergear V4 hot end
; Origin at platform center, set by MANUAL_X_HOME_POS compiled constants
; Z-min switch at platform, must move nozzle to X=135 to clear
; 2025-08-29 tweak priming spot to avoid scorching BuildTak surface
G90 ; absolute coordinates
G21 ; millimeters
M83 ; relative extrusion distance
M104 S[first_layer_temperature] ; start extruder heating
M140 S[first_layer_bed_temperature] ; start bed heating
M17 ; enable steppers
G4 P500 ; ... wait for power up
G92 Z0 ; set Z to zero, wherever it might be now
G0 Z10 F1000 ; move platform downward to clear nozzle; may crash at bottom
G28 Y ; home Y to clear plate, offset from compiled constant
G28 X ; home X, offset from M206 X, offset from compiled constant
G0 X135 Y0 F15000 ; move off platform to right side, center Y
G28 Z ; home Z to platform switch, offset from M206 Z measured
G0 Z2.0 F1000 ; get air under switch
;G0 Y-126 F10000 ; set up for priming, zig around corner
;G0 X0 ; center X
;G0 Y-125.5 ; just over platform edge
G0 Y-121 F15000 ; set up for priming
G0 X96 ; diagonally beyond trimmed corner of BuildTak plate
G0 Z0 F500 ; exactly at platform
M190 S[first_layer_bed_temperature] ; wait for bed to finish heating
M109 S[first_layer_temperature] ; set extruder temperature and wait
G1 E25 F200 ; prime to get pressure, generate blob on edge
;G0 Y-123 F5000 ; shear off blob
;G0 X15 F15000 ; jerk away from blob, move over surface
;G4 P500 ; pause to attach
;G1 X45 F500 ; slowly smear snot to clear nozzle
G0 X94 Y-119 F5000 ; shear off blob
G0 X90 F15000 ; jerk away
G4 P500 ; pause
G1 X50 Y-124 F500 ; smear snot
G1 Z1.0 F2000 ; clear bed for travel
;-- PrusaSlicer Start G-Code ends --
The one on the left came from the M2’s glass plate (with a brim barely improving its adhesion) and the one on the right was on BuildTak after all the fussing; I just noticed I laid them out in opposite directions.
An edge view shows the fuzzy surface on the left:
Makergear M2 BuildTak – small holes – edge
The tiniest holes in both are undersized, but AFAICT you could ram a screw through that bendy sheet without much effort.
The BuildTak sheet works well enough that I have not tried the PEI-covered FlexPlate, which I’m sure will require similar shimming to get a level surface.
And, no, I am not going to install a surface probe on the M2’s hot end.
Based on someearlieritems, I’d been printing TPU at 220 °C, but 230 °C fuses the threads together:
Terracycle Chain Idler Tire – correct settings
The filament turned out to be 1.79 mm diameter, rather than the nominal 1.75 mm, and a few iterations showed a 0.95 Extrusion Multiplier worked much better.
Those were printed at 30 mm/s with 0.25 mm layer height.
I now have a good stock of spare tires, each slightly different than all the others:
Terracycle Chain Idler Tire – spares
The first two slightly delaminated printed tires will remain in service until they show signs of falling apart, because I’d rather ride the bike than fiddle with it.
The day after I set up the Wasp Blower, the carnage was terrible to behold:
Wasp Blower – carnage
Two weeks later, the blower is chopping up two or three wasps each day.
As far as I can tell, the blower killed essentially every wasp leaving the nest and most of the returning foragers:
Wasp Blower – shattered wasps
After two weeks, (nearly?) all of the eggs remaining in the nest have hatched, the larvae / pupae have starved for lack of incoming food, and I’ve put out ant bait traps to discourage scavengers.
The plan is to keep running the blower until a week goes by without any kills, then seal the crack under the door sill.
I have no idea how the queens (Yellowjacket wasp nests have multiple queens!) are doing in there, but they must be getting pretty hungry and, we hope, will not survive the winter.
This makes me feel awful, but not nearly bad enough to regret dealing with the critters.
I sprayed the white-ish fragments (on the left) with satin-finish clear rattlecan “paint” in the hopes it would keep epoxy out of the cracks between the glass cuboids and leave the highly reflective air gaps. While it did a reasonable job of sealing, it bonded poorly with the epoxy and produced a dull surface finish.
The unsprayed fragments (on the right) turned out better, although the one in the upper right has a thin air bubble / layer on top. The unsealed cracks between the cuboids show well against the reflective layers, so I think spraying the fragments isn’t worth the effort.
The printed base has a 1 mm tall rim to retain the epoxy:
Printed Coaster Layout – solid model
I mixed enough epoxy to fill half the volume of a disk with the same overall OD and depth (V = h × π × d²/4), which turned out to be barely enough produce a level surface at the rim. There didn’t seem that much epoxy left on the various measuring / mixing cups, but next time I’ll round upward.
Many of the bubbles emerged from below the metalized paper, as well as between the glass and paper, so next time:
Set up a level platform with a sacrificial cover
Omit the adhesive sheet under the metallized paper
Pour a little epoxy into the recesses
Squish the metallized paper into place
Pour more epoxy to cover the paper
Gently squish the glass fragments into place
Ease more epoxy around the fragments
Chivvy the bubbles away
Fill to the rim
The top isn’t exactly flat and has some dull areas, so at some point I want to make it flat with 220 grit sandpaper, work up to some 3000 grit paper I’ve been saving for a special occasion, then finish it off with Novus polish. Which seems like enough hassle to keep the coaster under my sippy cup for a while.
The Branson 200 ultrasonic cleaner in the bathroom has been with me for a long time. If I’m reading the IC date codes correctly, it’s one of the first things I bought after real paychecks began arriving back in 1974:
Branson 200 ultrasonic cleaner – IC date codes
The circuit board has that spacious old-time layout:
Branson 200 ultrasonic cleaner – PCB overview
Believe it or not, this isn’t why I took the thing apart:
Branson 200 ultrasonic cleaner – charred resistor
I’ve never seen a PCB with the component values printed on it, but they definitely came in handy!
That resistor measured 743 Ω: still good, even with an extra-crispy coating.
Assuming it was dissipating a bit more than its 2 W rating could handle, I replaced it with a 470 Ω + 330 Ω series combination of 2 W 1% metal film resistors:
Branson 200 ultrasonic cleaner – retrofit resistors – top
In parallel with a 15 kΩ resistor on the back of the PCB to bring them down to 759 Ω:
Well, almost perfectly. The original case holes were a snug fit around a 25/64 inch = 9.8 mm drill , so I hand-twisted X and Y drills (10.1 and 10.3 mm, respectively) to embiggen the holes for a loose fit around the new switches.
The two small plastic disks + paper shims hold the PCB just far enough away from the case to put the switch actuators flush with the case surface, with 12 mm M3 SHCS replacing the original 6 mm screws.
The cardboard test piece came from the usual scan of the original switch cover and, after a few iterations, we now have a stylin’ paper replacement:
The transparent cover with greenish edges is transfer tape intended for vinyl sheets, which will likely not survive very long at all. It’s outset 3 mm from the paper label, just barely enough to get any traction at all on the case.
While I was at it, I replaced the worn black rubber feet with fancy red stamp-pad rubber feet:
For the record, only two screws secure the top & bottom parts of the case. They’re on the power-cord end of the bottom, so those are the only two feet you must peel off to get inside.
All of which put the cleaner back in operation while I figure out what kind of tape will seal the power switches more permanently.
The Terracycle (now T-cycle, for reasons presumably involving the transfer of money) chain return idlers on our Tour Easy bikes developed hardening of their urethane tires:
Terracycle Idler tire – printed vs OEM
Urethane shouldn’t crack like that, but after more than fifteen years, stuff wears out.
The white ring is 95A TPU printed on the Makergear M2, which is definitely more flexy than the original tire, but has the redeeming feature of being both Good Enough and trivially easy to model:
include <BOSL2/std.scad>
NumSides = 4*3*2*4;
$fn=NumSides;
Thick = 3.5;
ID = 46.4;
OD = ID + 2*Thick;
Length = 11.2;
tube(Length,id=ID,od=OD,anchor=BOTTOM);
It printed with 5 mm brims on both the ID and OD, because TPU has the barest adhesion to the M2’s glass plate + hair glue. There’s a long-unopened box now on the bench with a BuildTak PEI surface (thank you: you know who you are!) that should improve the situation.
In any event, the tires fit well:
Terracycle Idler tire – installed
The layer-to-layer adhesion isn’t as good as I think it should be, so I’ll likely use those tires as testcases for tweaking the new build plate & settings.
The Smell of Molten Projects in the Morning 