Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
These cute little toys serve as 3D printer torture tests:
Surprise Eggs
Obviously, each egg can hold only one of those toys, but I had to run them off in both retina-burn orange PETG and black PETG-CF for comparison.
These Surprise Egg models came from Thingiverse, but they’re also available on Printables. You’ll find many more, of course, at a variety of scales, with these on the small end.
The white eggs print with no difficulty at all, as does most of the equipment contained within:
Surprise Eggs – contents – orange PETG
Most moving parts require careful back-and-forth movement to break them free, but they’re surprisingly functional. The PETG-CF, printed with an Extrusion Multiplier = 0.8, looks better, although the moving parts were more firmly stuck together.
Not all of the equipment came out perfectly:
Surprise Eggs – contents on platform
Even without any special preparation, the MK4 didn’t have much trouble. If you were doing those for real, you could add stickum to the sheet or switch to a sheet with absurdly high PETG griptivity.
So as to not bury the lede, I remounted the front handlebar unit of Mary’s Handi-Quilter HQ Sixteen long-arm sewing machine so she can see the control panel with its small LCD:
HQ Sixteen – remounted handlebars in use
The new and old white LEDs produce distinctly different colors and intensities on the practice quilt fabric.
The original HQ Sixteen design bolted squarely atop the arm:
HQ Sixteen – original front handlebar mount
The control surface is, admittedly, angled slightly forward, but Mary was unable to see the lower few lines of the LCD without standing on tiptoe.
Begin with a crude tracing of the mating surfaces:
Front handlebar base tracings
Import the image into Inkscape and lay some shapes on it:
Front handlebar base layout – Inkscape
Import the SVG into LightBurn and cut templates to verify the hole positions:
HQ Sixteen – handlebar bolt templates
Obviously that took more than one try.
Rationalize the outlines, clean things up, and organize the shapes into useful named layers:
Front handlebar base layout – Inkscape layers
Save as an Inkscape SVG, import into OpenSCAD, and extrude the layers defining all those shapes into a solid model:
Handlebar Base Mount – solid model
That’s the most recent iteration; earlier ones appear in various pix.
I had intended to use either square nuts or heat-set inserts, but it turned out to be easier to just slam BOSL2 threaded nuts into the front plate and be done with it:
Handlebar Base Mount – solid model – hex nuts
The trick is to sink the nuts around a hole sized slightly larger than the screw’s nominal diameter, letting the threads fill empty space.
The handlebar base is mounted symmetrically along the machine arm centerline aligned with the two screws on the right. The rear block is offset to the left to clear the machine cover on the right, so the hull() wrapped around the two looks weird.
The front plate stands proud of the rest by dint of incorporating only a small slice of its back face into the hull() filling the gaps between the two. It’s not particularly stylin’, but it’s pretty close.
Finding the correct angle for the front plate required a couple of iterations, but they all built successfully:
HQ Sixteen – handlebar mount – on platform
Putting the threaded holes vertical created nicely formed threads that accepted the screws without hassle.
The block screws firmly to the arm and the handlebar unit screws to the block:
HQ Sixteen – remounted handlebars – side
The display now faces front:
HQ Sixteen – remounted handlebars – front
I eventually replaced those black oxide screws with shiny stainless ones, just for pretty.
The nine LEDs under the display now do a great job of lighting up the front of the machine’s arm, rather than the fabric at the needle, but fixing that will be a whole ‘nother project.
The handlebar grips with their control buttons now tilt at a somewhat inconvenient angle, which is also a whole ‘nother project.
Early reports from the user community are overwhelmingly positive.
The OpenSCAD source code and the SVG layout as a GitHub Gist:
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Loading the STL into PrusaSlicer, adding a text label to remind me which way it printed, then slicing with my PETG-CF profile shows the “Actual Speed”, which seems to take acceleration into consideration:
PrusaSlicer preview – actual speed
The colors in the legend don’t quite match the colors on the model, but the greenish layers with the jolts trundle along in the mid-20 mm/s range and the blue-ish straight-through layers at 30-ish mm/s.
Eryone PETG-CF has a somewhat fuzzy appearance that seems not characteristic of other brands, so I’ll try something else when these spools run out:
MK4 Resonance Test Box – overview
The right side of the box (as oriented on the platform) got all the layer retractions and came out festooned with PETG hairs:
MK4 Resonance Test Box – right side
You can check my labels by tracking the small retraction zit sticking up from the top layer; I got it wrong the first time. Open the images in a new tab to see more pixels.
The front:
MK4 Resonance Test Box – front side
The left:
MK4 Resonance Test Box – left side
And the rear:
MK4 Resonance Test Box – rear side
You can barely see the shadow of the “Rear” text on the surface, even though the wall is two threads thick and the text is indented by 0.2 mm, about half the thread width.
As far as I can tell, the MK4 Input Shaper compensation does a great job of suppressing resonance or wobble in all directions.
The Prusa belt tension guide pretty much explains that subject, with their Belt Tuner making up for my utter tone deafness. FWIW, if the Belt Tuner produces inconsistent results differing by an octave, either up or down from the correct value, the belt is way too loose: give the axis belt tension screw a turn or two to drag the results into the right time zone, then fine-tune from there.
While it is possible to reach both tensioning screws without too much trouble, they’re definitely not convenient.
The accelerometer fits on the hot end:
Prusa MK4 Accelerometer – on hot end
Then under the steel sheet, where it’s clamped by the platform magnets:
Prusa MK4 Accelerometer – on platform
The MK4 firmware measures the resonant frequencies while prompting you to put the accelerometer in the proper locations, then computes the best shaper values.
For reference, the stock OEM values:
X = MZV 50 Hz
Y = MZV 40 Hz
Just after I got the accelerometer and without doing anything to prep the MK4, these results popped out:
X = MZV 56 Hz
Y = MZV 42 Hz
Now, with bling and properly tensioned belts:
X = MZV 59 Hz
Y = MZV 45 Hz
The most recent values were also the most stable, once again pointing out the value of careful assembly and maintenance.
With that in mind, though, I built the laser ramp focus fixture shortly after doing the first recalibration and it has no visible ripples on any of its walls:
Ramp Test Fixture – corner detail
That’s a square corner perpendicular to the sloped top surface at the default 45 mm/s. It’s not as difficult a test as some you’ll see, but it suffices for my simple needs. The MK4 definitely behaves better around corners than the Makergear M2.
The small upward duct on the right side directs the exhaust air away from the platform. This is apparently critical for very high-temperature plastics like ABS and PC, but I did have one print fail due to excessively cold breezes on the platform.
There’s also an angled heater cable connector cover, with a matching cover on the electronics box routing the cable rearward to dress it away from the hulking extruder cable:
A pair of plant stands from a friend’s collection ended up in Mary’s care and cried out for feet to keep their welded steel wire legs from scratching the floor:
Wire plant stand feet – indoor stand
Admittedly, it’s not the prettiest stand you can imagine, but the sentimental value outweighs all other considerations.
The feet are shrink-wrapped around the legs with enough curviness to look good:
Wire plant stand feet – show side view
With a drain hole in the bottom to prevent water from rusting the wires any more than they already are:
Wire plant stand feet – show bottom view
I briefly considered a flat bottom at the proper angle to sit on the floor, but came to my senses; it would never sit at the proper angle.
The end results snapped into place:
Wire plant stand feet – indoor detail
Of course the other stand, at first glance identical to the one above, has a different wire size and slightly different geometry, which I only discovered after printing another trio of feet. Changing the appropriate constants in the OpenSCAD program and waiting an hour produced a better outcome:
Wire plant stand feet – outdoor stand
Living in the future is good, all things considered.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
With only days to spare, I decorated the doorbell button:
Doorbell button skulls – installed
Yeah, I jammed Sharpies in the eye sockets, but they look exactly the way they should. The middle skull is in the middle of the actuator in the hope that’s where it’ll get pushed.
The Smell of Molten Projects in the Morning 
