The Smell of Molten Projects in the Morning
Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
Several of this year’s praying mantises set up shop in the decorative grasses bracketing the front door:
We found their egg masses, formally called ootheca, attached to the stems in mid-October:
They feel like rigid urethane foam and seem eminently protective:
We’ll cut around the masses when it’s time to clear out the dead grass next spring. I was tempted to bring one inside, but dealing with a gazillion tiny mantises in a few months would be daunting.
Extra Fine Pilot V5 pens have a 0.5 mm ball, in contrast to the 1.0 mm ball in the cheap pens I’ve been using, so they should produce much finer lines.
Which turns out to be the case:
That’s a stack of three “Homage” Tek CC bottom decks under a Genuine Tektronix Circuit Computer.
The black scale at the top of the picture (and the bottom of the stack) came from a 1 mm cheap pen in the collet holder, the two green scales come from a 0.5 mm Pilot V5RT cartridge in its new holder, and the Original is (most likely) laser-printed back when that was a New Thing.
As always, paper makes a big difference in the results. The brownish paper is 110 pound card stock with a relatively coarse surface finish. The white paper is ordinary 22 pound general-purpose laser / inkjet printer paper.
The 1.0 mm pen (top) doesn’t much care what it’s writing on, producing results on the low side of OK: some light sections, no blobs. Perfectly serviceable, but not pretty.
The Pilot V5RT really likes better paper, as it bleeds out on the card stock whenever the CNC 3018XL so much as pauses at the end of a stroke. Using white paper slows, but doesn’t completely stop, the bleeding, making the blobs survivable.
I’ve been using card stock to get stiffer, more durable, and more easily manipulated decks, but the improved line quality on the white paper says I should laminate the decks in plastic, just like the original Tektronix design.
No surprise there!
The Google Pixel 3a camera, unlike the camera in my older Google Pixel XL, takes spectacularly good images through a widefield 5X eyepiece on the stereo zoom microscope:
That’s hand-holding the phone against the eyepiece while manipulating it with the other hand. Definitely not the most stable arrangement, but the camera copes well with slight motions. I really need a gripping hand for the camera, to free up another for the microscope’s focus knob.
For the record:
Zooming in (because it’s a stereo zoom microscope and I can), the 1.0 mm ball seems surprisingly un-wetted by its ink:
The Pilot V5 ball seems more smoothly covered:
Those are at the same magnification & crop size, so they’re to the same scale.
This definitely calls for a customized phone-to-eyepiece holder!
It turns out my all-time favorite Pilot Precise V5 Extra Fine stick pen also comes in a clicky-top retractable version:
The cartridge is a nice 6 mm cylinder, eminently transformable into a plotter pen:
A few minutes with a caliper provides key measurements for a snout surrounding the business end:
The green letters & numbers give the nearest drill sizes. The “T” values along the bottom are the tailstock turns (at 1.5 mm/turn) required to poke the drills to the indicated depths, eyeballed when the body just enters the hole.
Having recently decomissioned the Thing-O-Matic and harvested its organs parts, I have a vast collection of 3/8 inch = 9.52 mm shafts and matching bronze bushings:
Bronze bushings have low stiction, at least when they’re co-axial, and are much shorter than linear ball bearings.
I chopped off a 70 mm length of shaft and faced the raw end:
The other end had a maker’s logo, but I don’t recognize it:
I really wanted an 8 mm bore around the snout, but it just didn’t work out. The ring around the 7.5 mm counterbore shows where the larger drill just … stopped:
A trial fit with the pen cartridge:
The top of the shaft gets a somewhat longer knurled ring for the 3 mm SHCS holding the cartridge in place:
The screw bears on a split collar turned and drilled from a Delrin rod:
The “split” came from a simple saw cut across one side and I milled a flat spot in the knurling to seat the screw. As usual, the knurled ring got epoxied to the shaft.
The snout started as a 3/8 inch aluminum rod, drilled as shown in the sketch, with a (scant) 7.5 mm section to fit the shaft. The carbide insert left a nicely rounded shoulder that required trimming to fit snugly into the shaft:
The compound can handle the shallow angle required to shape the snout:
A trial fit showed the snout was a bit too long for comfort:
Making something shorter doesn’t pose much of a challenge:
Another trial fit shows it’s spot on:
The critical part is having the snout support the plastic around the pen tip to prevent wobbulation.
Epoxy the whole thing together, add a suitable spring, tighten the screws & nuts for the reaction plate, and it’s all good. I write with about 50 g of force for these pens, so a light preload seemed in order:
If I’d weighed the full-up shaft + snout + collar + cartridge, I’d know if the Y intercept matches that weight. It seems a little lighter, but I’m not taking the thing apart to find out.
The first version of the 3D printed holder (shown above) is a straightforward modification of the LM12UU diamond drag bit holder, but, after building enough of these things, I realized the circular reaction plate should be triangular to get more clearance in front of the Z-axis stepper motor when installing & removing the holder:
It also has a recess for the serrated top of the bearing, to prevent the knurled collar from clicking annoyingly as the Z-axis rises at the end of each stroke.
Now, to see how well it draws!
The OpenSCAD source code as a GitHub Gist:
| // Diamond Scribe in linear bearings for CNC3018 | |
| // Ed Nisley KE4ZNU – 2019-08-9 | |
| Layout = "Build"; // [Build, Show, Base, Mount, Plate] | |
| /* [Hidden] */ | |
| ThreadThick = 0.25; // [0.20, 0.25] | |
| ThreadWidth = 0.40; // [0.40, 0.40] | |
| /* [Hidden] */ | |
| Protrusion = 0.1; // [0.01, 0.1] | |
| HoleWindage = 0.2; | |
| inch = 25.4; | |
| function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit); | |
| ID = 0; | |
| OD = 1; | |
| LENGTH = 2; | |
| //- Adjust hole diameter to make the size come out right | |
| module PolyCyl(Dia,Height,ForceSides=0) { // based on nophead's polyholes | |
| Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2); | |
| FixDia = Dia / cos(180/Sides); | |
| cylinder(r=(FixDia + HoleWindage)/2,h=Height,$fn=Sides); | |
| } | |
| //- Dimensions | |
| PenOD = 6.1; // pen refill shaft, max OD | |
| Bearing = [(3.0/8.0)*inch,16.0,10.6]; // linear bearing body, ID = shaft diameter | |
| BearingFlange = [Bearing[OD],17.2,1.0]; // flange around end of bearing | |
| Spring = [8.5,9.5,15.5]; // compression spring around shaft, LENGTH = uncompressed | |
| SpringRecess = 4*ThreadThick; | |
| WallThick = 4.0; // minimum thickness / width | |
| Screw = [3.0,6.75,25.0]; // holding it all together, OD = washer | |
| Insert = [3.0,4.2,7.9]; // brass insert | |
| //Insert = [3.0,5.0,8.0]; | |
| //Insert = [4.0,6.0,10.0]; | |
| Clamp = [43.2,44.0,34.0]; // tool clamp ring, OD = clearance around top | |
| LipHeight = IntegerMultiple(2.0,ThreadThick); // above clamp for retaining | |
| BottomExtension = 15.0; // below clamp to reach workpiece | |
| MountOAL = LipHeight + Clamp[LENGTH] + BottomExtension; // total mount length | |
| echo(str("Mount OAL: ",MountOAL)); | |
| Plate = [PenOD + 4*ThreadWidth,Clamp[ID] – 0*2*WallThick,WallThick]; // spring reaction plate | |
| echo(str("Screw length: ",Spring[LENGTH] + Plate[LENGTH] + Insert[LENGTH])); | |
| NumScrews = 3; | |
| ScrewBCD = Bearing[OD] + Insert[OD] + 2*WallThick; | |
| echo(str("Retainer max OD: ",ScrewBCD – Screw[OD])); | |
| NumSides = 9*4; // cylinder facets (multiple of 3 for lathe trimming) | |
| // Basic mount shape | |
| module CNC3018Base() { | |
| translate([0,0,MountOAL – LipHeight]) | |
| cylinder(d=Clamp[OD],h=LipHeight,$fn=NumSides); | |
| translate([0,0,MountOAL – LipHeight – Clamp[LENGTH] – Protrusion]) | |
| cylinder(d=Clamp[ID],h=(Clamp[LENGTH] + 2*Protrusion),$fn=NumSides); | |
| cylinder(d1=Bearing[OD] + 2*WallThick,d2=Clamp[ID],h=BottomExtension + Protrusion,$fn=NumSides); | |
| } | |
| // Mount with holes & c | |
| module Mount() { | |
| difference() { | |
| CNC3018Base(); | |
| translate([0,0,-Protrusion]) // bearing | |
| PolyCyl(Bearing[OD],2*MountOAL,NumSides); | |
| translate([0,0,-Protrusion]) // bearing flanges | |
| PolyCyl(BearingFlange[OD],BearingFlange[LENGTH] + Protrusion,NumSides); | |
| translate([0,0,MountOAL – 1.5*BearingFlange[LENGTH]]) // sink into surface | |
| PolyCyl(BearingFlange[OD],2*BearingFlange[LENGTH],NumSides); | |
| for (i=[0:NumScrews – 1]) // clamp screws | |
| rotate(i*360/NumScrews) | |
| translate([ScrewBCD/2,0,MountOAL – Clamp[LENGTH]]) | |
| rotate(180/8) | |
| PolyCyl(Insert[OD],Clamp[LENGTH] + Protrusion,8); | |
| } | |
| } | |
| module SpringPlate() { | |
| difference() { | |
| hull() | |
| for (i=[0:NumScrews – 1]) | |
| rotate(i*360/NumScrews) | |
| translate([ScrewBCD/2,0,0]) | |
| cylinder(d=Screw[OD] + 4*ThreadWidth,h=Plate[LENGTH],$fn=24); | |
| translate([0,0,-Protrusion]) | |
| PolyCyl(Plate[ID],2*MountOAL,NumSides); | |
| translate([0,0,Plate[LENGTH] – SpringRecess]) // spring retainer | |
| PolyCyl(Spring[OD] + 4*ThreadWidth,SpringRecess + Protrusion,NumSides); | |
| for (i=[0:NumScrews – 1]) // clamp screws | |
| rotate(i*360/NumScrews) | |
| translate([ScrewBCD/2,0,-Protrusion]) | |
| rotate(180/8) | |
| PolyCyl(Screw[ID],2*MountOAL,8); | |
| } | |
| } | |
| //—– | |
| // Build it | |
| if (Layout == "Base") | |
| CNC3018Base(); | |
| if (Layout == "Mount") | |
| Mount(); | |
| if (Layout == "Plate") | |
| SpringPlate(); | |
| if (Layout == "Show") { | |
| Mount(); | |
| translate([0,0,MountOAL + Plate[LENGTH] + Spring[LENGTH]]) | |
| rotate([180,0,0]) | |
| SpringPlate(); | |
| } | |
| if (Layout == "Build") { | |
| translate([0,-0.75*Clamp[OD],MountOAL]) | |
| rotate([180,0,0]) | |
| Mount(); | |
| translate([0,0.75*Plate[OD],0]) | |
| SpringPlate(); | |
| } |
As you might expect by now, I harvest various bits & pieces from the PCs falling off the trailing edge of my assortment. The bag of obsolete DRAM recently floated to the top of the heap:
Half a gig of ECC RAM from what might have been a fire-breathing Pentium Pro box:
The PCBs along the top apparently filled vacant memory slots.
Some 32 and 64 MB DRAM from a few IBM laptops I turned into picture frames:
DDR2 DRAM in assorted sizes & speeds:
PC133 DDR DRAM, with four sticks of 1 GB PC3 along the bottom:
If you look closely, you may see something you can use. No reasonable offer refused …
The JB Weld epoxy I slathered on our trusty hand-held cheese slicer a year ago continues to withstand daily washing and occasional trips through the dishwasher:
The bottom is in fine shape, too:
Compare it with XTC-3D epoxy, which admittedly isn’t rated for continuous water exposure, after a year:
JB Weld FTW!
Just to see how it worked, I engraved the Tek Circuit Computer scales on scrap CDs:
At first, I hadn’t correctly scaled the text paths, but the diffraction patterns caught my eye:
The illumination comes from two “daylight” T8 LED tubes in a shoplight fixture, running left-to-right, so it seems I held the camera rotated 1/4 turn in landscape mode. The pix look OK either way.
Bottom deck:
Middle deck:
Top deck, with the camera held portrait-style:
I’m a sucker for diffraction patterns …
The tiny engravings don’t photograph well, because they’re floating atop the transparent disc and the rainbow patterns from the data layer, but they still come out OK even when scaled to fit on a hard drive platter:
Looking good!
The Smell of Molten Projects in the Morning 