Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
For reasons not relevant here, I ended up making a field-expedient repair to a garden gate latch:
Improvised gate latch staple – installed
The hole in the post just to the left of the obviously improvised staple shows where the Original Staple had vanished, never to be seen again. It looks like the gate has shifted an inch or so to the right (or the post to the left), which would explain why the staple gradually worked loose.
The improvised staple is a length of coat hanger wire bent into a square U, with the ends snipped off at an acute angle:
Improvised gate latch staple – cut wire
Those points do look scary, don’t they?
Then I gently tapped it into place, driving maybe ¾ inch of wire in the wood, flattening the loop a little more than I wanted, but not enough to make me try again.
Not our gate, not Mary’s garden, but deer pose a threat to all veggies within, without regard to ownership.
I have *a lot* of coat hanger wire for repairs like this …
The test patterns will require power / speed tweakage to properly mark cardboard on other machines. The vector boxes are about 1.5 mm wide: these are small differences in small patterns.
The setup for both LightBurn 1.7 RC-13 and RDWorks 8.01.65:
The engraved patterns run at 500 mm/s & 20% power
The lines & letters run at 100 mm/s & 8% Min – 9% Max power
All on white cardboard, with image contrast blown out
Scanning offset = 0.2 mm = the usual setting for my machine
In LightBurn:
Scanning Offset 0.2 – LightBurn
In RDWorks:
Scanning Offset 0.2 – RDWorks
The slight shift to the left in the LightBurn results shows LB does not shift the uni-directional pattern to line up with the vector shape as RDWorks does, which is what started the forum thread.
Scanning offset = 1.0 mm to accentuate the difference, while shredding the bi-direction pattern as expected.
LightBurn’s uni-directional engraved pattern is still in the same slightly leftward-shifted position relative to the vectors, showing the offset value has not been applied:
Scanning Offset 1.0 – LightBurn
RDWorks definitely applies the offset in both modes:
Scanning Offset 1.0 – RDWorks
I do not know why RDWorks did not output the final “l” over there on the right, but it did so on some (not all) of the patterns while setting things up. The jank is strong with it.
So having LightBurn apply the same offset value for both uni- and bi-directional engravings would fix the (slight) offset in my machine. I think it will also fix the much larger misalignment in [the other] machine in that forum discussion.
The whole problem seems to arise from the response time of the HV power supply / laser tube: the position of the left & right edges of the scanned output line depend critically on the rising and falling edges of the current applied to the tube and its power output.
Being me, of course, makes me want a different offset value applied to the uni-directional case, just for fine tuning. Which would require a duplicate offset-per-speed table and that looks like a UX disaster comin’ on strong.
The general idea of a light box is (wait for it) a uniform background in a box full of bright light:
Light Box – overview
Obviously, this is a low-budget light box, but it makes perfect sense if you already have an essentially unlimited supply of moving boxes, 11×17 inch plotter paper, and a couple of photo / video lights lying around.
A two-layer cardboard ring glued to the top keeps the light from sliding off the box and stiffens the gaping hole letting the light shine through.
You’d normally use a fabric background to get rid of those ugly gaps around the edges and a larger box would be better, so this is along the lines of a proof-of-concept.
In this day and age, you’d normally use a phone camera:
Light Box – gears overview – DOF
The lens on my Pixel 6a has a fixed focal length (around 4.4 mm = 27 mm equivalent) and a fixed f/1.8 (-ish) aperture, producing a razor-thin depth of field at the rear of the front gears. Note the fuzzy gears in the background, all of three inches away, and the slightly fuzzy front edge of the front gears. The camera’s digital zoom doesn’t help matters in the least, despite the AI-powered interpolation.
Keeping things close together helps, although the far end of the wipe towers and the rear of the gears lose detail:
Light Box – gears stacked
Looking from above also helps a little, but a top viewing port would reduce the skewed perspective:
Light Box – gears detail – DOF
Shallow DOF keeps your attention on the foreground, which is why real photographers use it for portraits:
Light Box – gears standing – DOF
The camera, an ancient Sony DSC-H5 with a zoom lens going down to f/8, still does nice work through a 2× macro adapter lens:
Light Box – gear detail – top light
The DOF is still narrow, but at least the entire front gear is in focus.
Adding a front light picks out the knurling:
Light Box – gears detail – front light
The results definitely look better than before, but it’ll take a bit of getting used to traipsing to the Basement Laboratory for every photo …
The flat robot vacuum assigned to clean the floors around here would occasionally get stuck under the leg of my Husky workbench-as-desk and fail to complete its mission. Living in the future makes solving that problem a matter of minutes:
Husky workbench caster feet – installed
The upper rim captures the locked-in-place wheel in a 35×25 mm recess atop the middle 45×35 mm slab, with a 2.5 mm cork layer on the bottom. Laser-cut, of course, glued with ordinary yellow wood glue, and clamped for about half of a Squidwrench remote meeting.
Raising the desk by 5.5 mm gives the Flat One juuust enough clearance to scuttle under there:
The small bearings are 25 mm OD, with correspondingly small clearances between their moving parts, but they all spun easily after a bit of breaking in.
As with their larger cousins, the orange PETG bearing has the most axial play and worked just fine right off the platform. The gray PETG-CF bearing was jammed and required concerted effort to get the gears rolling, but now has essentially no axial play while turning easily. The snappy-looking orange and black bearing has very little play and feels the best of the three.
The single-material bearings take about 20 minutes to print, while the mixed material one requires 80 minutes due to the extruder purging and nozzle clearing. The larger mixed material bearing took more than three hours, but time doesn’t scale as the cube of the size because changing materials runs at a constant time:
Small Planetary Gear Bearings – PETG PETG-CF with wipe towers
The smaller mixed gear produced the smaller wipe tower on the right, but changing materials remains an expensive process. Of course, if you were doing this in production, you’d make a couple dozen of the little things in one job: the machine would spend most of its time squirting out planetary gear bearings with the same number of material changes building the same size wipe tower.
They’re slightly too small for my fingers and surely pose a choking hazard to children, but they’re definitely cute.
A small tweak to the venerable spoon drainer adds a configurable cutout adapting it to a slightly different dish drainer rack:
Measuring Spoon Drainer – solid model
Which lets it snuggle into the corner:
Measuring spoon drainer – installed
Both the old and new racks had coated steel loops stuck into rubberoid feet perfectly suited to collect water and eventually rust the loops. Given a new rack, I figured potting the feet in JB PlasticBonder urethane adhesive would help forestall the rust:
Rubbermaid dish drainer – foot potting
I wish it were white, rather than black, but the only other color choice is tan and I can’t wish nearly that hard.
So I loaded up the same STL in Prusaslicer and made three more:
Planetary Gear Bearing – M2 vs MK4
Both pictures show the same red bearing, done in PLA on the Makergear M2. The other bearings are PETG and PETG-CF on the Prusa MK4 + MMU3.
The blue bearing has about 5 mm of axial play, a bit more than the red.
The gray bearing is PETG-CF and has maybe 1 mm of axial play, which agrees with my original observation that an Extrusion Multiplier of 1.0 results in slightly overstuffed carbon fiber parts. It’s not much and, frankly, produces a better fit in this case, but it’s different than pure PETG. Which should come as no surprise, of course, given that it’s 15% carbon.
The gray-and-orange bearing looks spectacular in person and has about 3 mm of axial play, roughly the same as the red bearing, which you’d expect from overstuffed PETG-CF and pure PETG.
The single-color bearings print in about 1.5 hours and the two-color one weighed in over four hours. Multi-material objects are do-able, but you gotta want the results.
I told Prusaslicer to wipe the orange filament into the gray infill during color changes (per the Wipe Tower doc), but those two gray parts have so little infill as to make no difference:
Planetary Gear Bearing – PETG PETG-CF with wipe tower
The wipe tower in that posed photo has a nubbly texture because the filament just gets squirted without regard to anything other than maintaining the basic tower shape.
Seeing things appear on the platform never gets old!
The Smell of Molten Projects in the Morning 