Ed Nisley's Blog: Shop notes, electronics, firmware, machinery, 3D printing, laser cuttery, and curiosities. Contents: 100% human thinking, 0% AI slop.
For reasons that aren’t relevant here, I had to reinforce some old basement stairs. Rather than drilling holes, sinking anchors, and installing screws, I just nailed painted 2×4 strips to the foundation using this Craftsman 1231.3817 Power Hammer, which is not available in a Sears / Kmart near you:
Sears Craftsman Power Hammer
It’s a handheld gun that drives two inches of hardened steel nail into solid concrete by firing what looks like an overstuffed 0.22 Short blank cartridge: load a nail, fit a cartridge, press the muzzle firmly against the target, and whack the butt end with a hammer.
Worked like a champ. Scary as you’d imagine.
If the nail stands proud of the surface, you can hit it again with a low(er) power load to drive it the rest of the way. Sometimes that sinks it below the surface, leaving a cylindrical pit. In the situations where I use this thing, nobody will ever notice.
It’s similar to the Remington Model 476 Powder Actuated Fastening Tool (manual), which you can get from Amazon and surely other vendors; fancier versions also exist. Equally surely, they’re illegal in some jurisdictions.
I have reason to use it every few decades, which is entirely enough for me…
Wear goggles, earplugs, gloves, and don’t get stupid.
Sticking an extruded plastic thread to the platform of a 3D printer requires absolutely accurate alignment and spacing, maybe ±0.05 mm across the entire platform. I’ll leave the topic of automatic alignment measurement & compensation for another day; here’s how to measure the actual platform alignment.
If the wall thickness (in the XY plane) doesn’t come out exactly right, fix that first by verifying the filament diameter setting, then adjusting the Extrusion Multiplier. If the extruder doesn’t produce the same wall thickness that the slicer calls for, you won’t get good results from anything else. In this case, they all have 0.40 mm thick walls, with 0.25 mm layers.
The first layer of all five boxes should be identical:
M2 V4 nozzle – thinwall box first layer
If the platform isn’t absolutely flat and properly aligned, those five first layers won’t be the same thickness. It’s surprisingly easy to spot differences under 0.05 mm, so pay attention to what’s happening.
When they’re done, pop them off and measure their actual height. I measure across adjacent sides, leaving the corners / stray hairs / snot out of the measurement, and figure the eyeballometric average of the values, which usually differ by less than ±0.03 mm. Write the height on the side to eliminate future angst:
Thinwall Box – platform height
The boxes should be 5.00 mm tall, so the leftmost box is short by -0.02 mm and the rightmost by -0.15 mm. The five boxes were 4.98, 4.95, 4.93, 4.92, and 4.85, with a mean of 4.93 mm. The variation across the 200×250 mm platform is 0.13 mm, which is pretty good.
Comparing the bottom layers of those boxes, the first layer of the 4.85 mm box is definitely squashed:
Thinwall Hollow Boxes – first layer bottom view – 4.98 4.85 mm
Once you know what to look for, it’s also obvious from the side (4.98 on the left, 4.85 on the right, bottom layers facing each other):
Thinwall boxes – 4.98 4.85 – bottom layers
Keep in mind that’s a difference of 0.13 mm = 130 µm, just over the ±0.05 mm I usually bandy about. The nominal layers are 0.25 mm = 250 µm.
A bit more magnification shows the nicely rounded first layer of the 4.98 mm box (rightmost thread of leftmost set):
Thinwall Box – 4.98 mm
And the squashed first layer of the 4.85 mm box (likewise):
Thinwall Box – 4.85 mm
Because the Z axis moves upward (on the M2, the platform moves downward) by exactly the layer thickness at the end of each layer, the first layer must absorb the entire difference between the desired thickness and the actual nozzle-to-platform distance. That squashed first layer is 0.10 mm thick, a bit less than half of the nominal 0.25 mm. The second layer of each box looks just like all the higher layers.
You can set the Z-axis offset for a very slight squish, with the maximum nozzle-to-platform distance at 0.25 mm and the minimum set by the other end of the total misalignment, because the plastic won’t adhere to the platform when the nozzle-to-platform distance exceeds the nozzle diameter.
Think of it this way: the plastic emerges from a 0.35 mm nozzle as a (slightly larger than) 0.35 mm cylinder that must squash to become a 0.25 mm high x 0.40 mm wide thread. Given the measurements above, setting the Z-axis home position to make the average box height equal to 5.00 mm would make the tallest box come out at 5.07 mm, which requires a 0.32 mm actual first layer that probably wouldn’t stick well at all.
When your printer can consistently produce five thinwall boxes with the proper wall thickness and height, then you can move on to more complex objects.
Although Mary’s name in the base of the Clover Mini Iron holder was readable in person, I wondered what filling the characters with epoxy would do. A bit of tinkering produced a name plate:
Text Block – solid model
Which is more readable in person, but magenta PETG renders it basically unreadable here:
Text Block – unfilled
The intent of this was not to produce a lovely name block, but to see what various epoxy fills and techniques produced. Think of this as the one you must build to throw away…
I tediously filled the first line with straight JB Weld epoxy, deliberately ruining the least functional of my 1 ml syringes to ease a strand of epoxy into each letter, then poking the goo into place with a pointed rod:
Text Block – plain epoxy fill
That was way tedious.
Having recently replaced the cartridge in our trusty HP Laserjet 1200, I had no qualms about step-drilling the “empty” cartridge to get the toner. For future reference, here’s where you drill into a 7115X cartridge:
HP 7115X Toner Cartridge – holes in waste and supply compartments
I probably used too much toner, but one heaping pile on that wooden stick didn’t seem like a lot at the time:
Text Block – toner black epoxy
This turned the epoxy rather thick and pasty; it didn’t ease into the letters very well at all. After the usual day, it cured into a slightly rubbery solid, quite unlike the usual rock-solid epoxy blob.
Some rummaging in the Basement Laboratory Warehouse Wing turned up two containers of aluminum powder from an Etch-a-Sketch; I mixed some into another batch of epoxy, to very little effect. With both blends, I just squished the epoxy into the letters and didn’t worry too much about slobbering any over the surface of the block.
To even off the top surface, I affixed the block to the Sherline’s tooling plate with tapeless sticky (basically double-sided tape without the tape):
Text Block – milling setup
Manually traversing the surface (3 k rpm, 24 inch/min) and stepping downward about 0.1 mm per pass gradually crisped up the letters. I expected the excess epoxy to vanish after going 0.1 mm or so into the top layer, but it actually required removing the entire 0.25 mm Hilbert-curve-filled surface layer to get rid of the epoxy that soaked into / through the tiny gaps. This is 0.4 mm down from the first pass, maybe 0.1 mm into the plastic:
Text Block – milled 0.4 mm
With the top layer gone, it looked rather gnarly, so I applied a sanding block that didn’t do much at all: smoother, still gnarly. Spreading maybe 0.3 ml of IPS 4 solvent adhesive over the sanded surface smoothed it a bit:
Text Block – sanded and leveled with IPS 4
Perhaps a topcoat of clear epoxy, along the lines of XTC-3D, would produce better results.
The small black dots in the top line are holes from bubbles in the epoxy. The missing section of the M started out as a bubble (just visible at 0.4 mm) and gradually enlarged as pieces tore out of the recess. There’s another bubble breaking the right stroke of the “y”.
The small dots in the “ley” are plastic spheres that carried the aluminum powder in the Etch-a-Sketch; they’re cross-sectioned and perfectly flat. The epoxy color is marginally lighter than the top line, but not enough to notice.
Backlit on a window, nearly all of the ugly fades away:
Text Block – backlit
It’s definitely not presentation quality, that’s for sure, and I won’t attempt to fill the Mini Iron holder…
The OpenSCAD source code, which can also produce the soldering iron holder:
// Clover MCI-900 Mini Iron holder
// Ed Nisley KE4ZNU - August 2015
Layout = "Text"; // Iron Holder Show Text
//- Extrusion parameters - must match reality!
ThreadThick = 0.25;
ThreadWidth = 0.40;
function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);
Protrusion = 0.1;
HoleWindage = 0.2;
inch = 25.4;
Tap10_32 = 0.159 * inch;
Clear10_32 = 0.190 * inch;
Head10_32 = 0.373 * inch;
Head10_32Thick = 0.110 * inch;
Nut10_32Dia = 0.433 * inch;
Nut10_32Thick = 0.130 * inch;
Washer10_32OD = 0.381 * inch;
Washer10_32ID = 0.204 * inch;
//------
// Dimensions
CornerRadius = 4.0;
CenterHeight = 25; // center at cord inlet on body
BodyLength = 110; // cord inlet to body curve at front flange
Incline = 10; // central angle slope
FrontOD = 29;
FrontBlock = [20,1.5*FrontOD + 2*CornerRadius,FrontOD/2 + CenterHeight + BodyLength*sin(Incline)];
CordOD = 10;
CordLen = 10;
RearOD = 22;
RearBlock = [15 + CordLen,1.5*RearOD + 2*CornerRadius,RearOD/2 + CenterHeight];
PlateWidth = 2*FrontBlock[1];
TextDepth = 4*ThreadThick;
ScrewOC = BodyLength - FrontBlock[0]/2;
ScrewDepth = CenterHeight - FrontOD/2 - 5;
echo(str("Screw OC: ",ScrewOC));
BuildSize = [200,250,200]; // largest possible thing
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,
$fn=Sides);
}
// Trim bottom from child object
module TrimBottom(BlockSize=BuildSize,Slice=CornerRadius) {
intersection() {
translate([0,0,BlockSize[2]/2])
cube(BlockSize,center=true);
translate([0,0,-Slice])
children();
}
}
// Build a rounded block-like thing
module RoundBlock(Size=[20,25,30],Radius=CornerRadius,Center=false) {
HS = Size/2 - [Radius,Radius,Radius];
translate([0,0,Center ? 0 : (HS[2] + Radius)])
hull() {
for (i=[-1,1], j=[-1,1], k=[-1,1]) {
translate([i*HS[0],j*HS[1],k*HS[2]])
sphere(r=Radius,$fn=4*4);
}
}
}
// Create a channel to hold something
// This will eventually be subtracted from a block
// The offsets are specialized for this application...
module Channel(Dia,Length) {
rotate([0,90,0])
linear_extrude(height=Length)
rotate(90)
hull() {
for (i=[-1,1])
translate([i*Dia,2*Dia])
circle(d=Dia/8);
circle(d=Dia,$fn=8*4);
}
}
// Iron-shaped series of channels to be removed from blocks
module IronCutout() {
union() {
translate([-2*CordLen,0,0])
Channel(CordOD,2*CordLen + Protrusion);
Channel(RearOD,RearBlock[0] + Protrusion);
translate([BodyLength - FrontBlock[0]/2 - FrontBlock[0],0,0])
Channel(FrontOD,2*FrontBlock[0]);
}
}
module TextBlock() {
translate([2,10,0])
linear_extrude(height=TextDepth + Protrusion,convexity=2) // rendering glitches for convexity > 1
// text("Mary",font="Ubuntu:style=Bold Italic",halign="center",valign="center");
text("Mary",font="Junicode:style=Bold Italic",halign="center",valign="center",size=20,spacing=1.05);
translate([2,-15,0])
linear_extrude(height=TextDepth + Protrusion,convexity=2)
text("Nisley",font="Junicode:style=Bold Italic",halign="center",valign="center",size=20,spacing=1.05);
}
//- Build it
if (Layout == "Iron")
IronCutout();
if (Layout == "Holder" || Layout == "Show")
difference() {
union() {
translate([(BodyLength + CordLen)/2 - CordLen,0,0])
TrimBottom()
RoundBlock(Size=[(CordLen + BodyLength),PlateWidth,CornerRadius]);
translate([(RearBlock[0]/2 - CordLen),0,0])
TrimBottom()
RoundBlock(Size=RearBlock);
translate([BodyLength - FrontBlock[0]/2,0,0]) {
TrimBottom()
RoundBlock(Size=FrontBlock);
}
}
translate([0,0,CenterHeight])
rotate([0,-Incline,0])
if (Layout == "Show")
# IronCutout();
else
IronCutout();
translate([0,0,-Protrusion])
PolyCyl(Tap10_32,ScrewDepth + Protrusion,6);
translate([ScrewOC,0,-Protrusion])
PolyCyl(Tap10_32,ScrewDepth + Protrusion,6);
translate([(RearBlock[0] - CordLen) + BodyLength/2 - FrontBlock[0],0,CornerRadius - TextDepth])
TextBlock();
}
if (Layout == "Text")
difference() {
translate([0,0,0])
TrimBottom(Slice=8*ThreadThick)
RoundBlock(Size=[80,65,8*ThreadThick],Radius=8*ThreadThick);
# translate([-2,2,8*ThreadThick - TextDepth])
TextBlock();
}
Well, it’s actually not “sensing”, but the demo code now sizes the graph to the paper size reported by the plotter, so you can plot on cheap and readily available A-size paper. The Vulcan Nerve Pinch that switches paper size on the fly is Enter+Size; I leave the DIP switches set for B-size sheets, because they’re more impressive and take longer to plot.
A collection of A-size plots:
Superformula Plots – A-size paper
The perspective foreshortening makes the sheets look square and the plots seem circular; they’re not.
The plots lie in rough time sequence from lower left to upper right, showing that I tweaked the n1 parameter to avoid the sort of tiny middle that gnawed a hole right through the center-bottom sheet. I also removed higher m parameter values, because more than 50-ish points doesn’t work well on smaller sheets.
I figured out how to use the Python ternary “operator” and tweaked the print formatting, but basically it’s a hack job through & through.
The Python source code, including the hacked Chiplotle routines that produce the SuperFormula:
from chiplotle import *
from math import *
from datetime import *
import random
def superformula_polar(a, b, m, n1, n2, n3, phi):
''' Computes the position of the point on a
superformula curve.
Superformula has first been proposed by Johan Gielis
and is a generalization of superellipse.
see: http://en.wikipedia.org/wiki/Superformula
Tweaked to return polar coordinates
'''
t1 = cos(m * phi / 4.0) / a
t1 = abs(t1)
t1 = pow(t1, n2)
t2 = sin(m * phi / 4.0) / b
t2 = abs(t2)
t2 = pow(t2, n3)
t3 = -1 / float(n1)
r = pow(t1 + t2, t3)
if abs(r) == 0:
return (0,0)
else:
# return (r * cos(phi), r * sin(phi))
return (r,phi)
def supershape(width, height, m, n1, n2, n3,
point_count=10*1000, percentage=1.0, a=1.0, b=1.0, travel=None):
'''Supershape, generated using the superformula first proposed
by Johan Gielis.
- `points_count` is the total number of points to compute.
- `travel` is the length of the outline drawn in radians.
3.1416 * 2 is a complete cycle.
'''
travel = travel or (10*2*pi)
## compute points...
phis = [i * travel / point_count
for i in range(1 + int(point_count * percentage))]
points = [superformula_polar(a, b, m, n1, n2, n3, x) for x in phis]
## scale and transpose...
path = [ ]
for r, a in points:
x = width * r * cos(a)
y = height * r * sin(a)
path.append(Coordinate(x, y))
return Path(path)
## RUN DEMO CODE
if __name__ == '__main__':
plt=instantiate_plotters()[0]
# plt.write('IN;')
if plt.margins.soft.width < 11000: # A=10365 B=16640
maxplotx = (plt.margins.soft.width / 2) - 100
maxploty = (plt.margins.soft.height / 2) - 150
legendx = maxplotx - 2600
legendy = -(maxploty - 650)
tscale = 0.45
numpens = 4
m_list = [n/10.0 for n in [11, 13, 17, 19, 23]]; # prime/10 = number of spikes
n1_list = [n/100.0 for n in range(55,75,1) + range(80,120,5) + range(120,200,10)] # ring-ness 0.1 to 2.0, higher is larger
else:
maxplotx = plt.margins.soft.width / 2
maxploty = plt.margins.soft.height / 2
legendx = maxplotx - 3000
legendy = -(maxploty - 700)
tscale = 0.45
numpens = 6
m_list = [n/10.0 for n in [11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59]]; # prime/10 = number of spikes
n1_list = [n/100.0 for n in range(15,75,1) + range(80,120,5) + range(120,200,10)] # ring-ness 0.1 to 2.0, higher is larger
print "Max: ({},{})".format(maxplotx,maxploty)
n2_list = [n/100.0 for n in range(10,50,1) + range(55,100,5) + range(110,200,10)] # spike-ness 0.1 to 2.0, lower is spiky
plt.write(chr(27) + '.H200:') # set hardware handshake block size
plt.set_origin_center()
plt.write(hpgl.SI(tscale*0.285,tscale*0.375)) # scale based on B size characters
plt.write(hpgl.VS(10)) # slow speed for those abrupt spikes
plt.select_pen(1) # standard loadout has pen 1 = black
plt.write(hpgl.PA([(legendx,legendy)]))
plt.write(hpgl.LB("Started " + str(datetime.today())))
m = random.choice(m_list)
pen = 1
for n1, n2 in zip(random.sample(n1_list,numpens),random.sample(n2_list,numpens)):
n3 = n2
print "{0} - m: {1:.1f}, n1: {2:.2f}, n2=n3: {3:.2f}".format(pen,m,n1,n2)
plt.select_pen(pen)
plt.write(hpgl.PA([(legendx, legendy - 100*pen)]))
plt.write(hpgl.LB("Pen {0}: m={1:.1f} n1={2:.2f} n2=n3={3:.2f}".format(pen,m,n1,n2)))
e = supershape(maxplotx, maxploty, m, n1, n2, n3)
plt.write(e)
pen = pen + 1 if (pen % numpens) else 1
plt.select_pen(1)
plt.write(hpgl.PA([(legendx, legendy - 100*(numpens + 1))]))
plt.write(hpgl.LB("Ended " + str(datetime.today())))
plt.select_pen(0)
Last month’s basement safe log showed the humidity (blue trace) relentlessly rising:
Basement Safe – 2015-08-09
Replacing that bag emptied the dried silica gel stash, so I piled six saturated bags in the oven for an overnight regeneration with the oven set to “Warm”, which the IR thermometer reported as 140 °F or so at the bag surface. They sat on cooling racks atop cookie sheets that pretty much filled two oven shelves, with good air flow across their tops and minimal flow between bags and cookie sheet.
The last time around, I spread the beads directly on the cookie sheets. That seemed like a lot of effort, so I wanted to see how the low-labor alternative worked.
The two upper-left bags in each group had a pair of bulldog clips holding them closed. The larger bags hold 500 g of “dry” silica gel and the center bag in the lower row was a smaller mesh bag:
Silica Gel drying – 2015-08-12
The big bags lost a bit under 130 g during 10 hours, call it 12 g/h, and felt slightly damp on their lower surface.
I cranked the oven to 230 °F, the lowest actual heat setting, for 210 °F on the bag surface. That got rid of the last 30 g in three hours; another hour brought them to pretty nearly their dry weight of 507 g (gross, with bag / staples / clips).
Drying being an exponential process, it looks like an overnight bake at “230 °F” will do the trick without melting the bags; the lower temperature doesn’t quite get the job done.
Thinwall open boxes – side detail – 4.98 4.85 measured
Alas, the shutter failed after that image, leaving me with pictures untaken and naught to take them with.
The least-awful alternative seems to be gimmicking up an adapter for a small USB camera from the usual eBay source:
Fashion USB video – case vs camera
The camera’s 640×480 VGA resolution is marginally Good Enough for the purpose, as I can zoom the microscope to completely fill all those pixels. The optics aren’t up to the standard set by the microscope, but we can cope with that for a while.
A bit of doodling & OpenSCAD tinkering produced a suitable adapter:
USB Camera Microscope Mount – solid model
To which Slic3r applied the usual finishing touches:
USB Camera Microscope Mount – Slic3r preview
A bit of silicone tape holds the sloppy focusing thread in place:
USB Camera Microscope Mount – cap with camera
Those are 2-56 screws that will hold the cap onto the tube. I drilled out the clearance holes in the cap and tapped the holes in the eyepiece adapter by hand, grabbing the bits with a pin vise.
Focus the lens at infinity, which in this case meant an old DDJ cover poster on the far wall of the Basement Laboratory, and then it’ll be just as happy with the image coming out of the eyepiece as a human eyeball would be.
I put a few snippets of black electrical tape atop the PCB locating tabs before screwing the tube in place. The tube ID is 1 mm smaller than the PCB OD, in order to hold the PCB perpendicular to the optical axis and clamp it firmly in place. Come to find out that the optical axis of the lens isn’t perfectly perpendicular to the PCB, but it’s close enough for my simple needs.
And then it fits just like you’d expect:
USB Camera Microscope Mount – on eyepiece
Actually, that’s the second version. The distance from the camera lens (equivalently: the PCB below the optical block, which I used as the datum plane) to the eyepiece is a critical dimension that determines whether the image fills the entrance pupil. I guesstimated the first version by hand-holding the camera and measuring with a caliper, tried it out, then iteratively whacked 2 mm off the tube until the image lit up properly:
USB Camera Microscope Mount – adjusting tube length
Minus 4 mm made it slightly too short, but then I could measure the correct position, tweak that dimension in the code, and get another adapter, just like the first one (plus a few other minor changes), except that it worked:
USB Camera Microscope Mount – first light
That’s a screen capture from VLC, which plays from /dev/video0 perfectly. Some manual exposure & color balance adjustment may be in order, but it’s pretty good for First Light.
It turns out that removing the eyepiece and holding the bare sensor over the opening also works fine. The real image from the objective fills much more area than the camera’s tiny sensor: the video image covers about one digit in that picture, but gimmicking up a bare-sensor adapter might be useful.
That can also come from a sensor failure, but it takes perfectly good movies. That’s the differential diagnosis for shutter failure, because movies don’t use the shutter.
The shutter still functions, in that peering into the lens shows the shutter closing as it takes a picture, so I suspect it’s gotten a bit sticky and slow over the years. None of the various shutter-priority speeds have any effect, which means that the shutter isn’t responding properly.
A quick read of the service manual shows the Field Replaceable Unit for this situation is the entire lens assembly. Back in the day, a new lens assembly came with its own calibration constants on a floppy disk that you’d install with Casio’s service program (the latest version ran with Windows 98!) using a special USB communication mode triggered by a Vulcan Nerve Pinch on the camera. At this late date, none of that stuff remains available.
While I could take the camera apart and crack the lens capsule open, I doubt that would make it better and, in this case, ending up with a crappy camera doesn’t count for much. Extracting the lens assembly requires dismantling the entire thing, which, frankly, doesn’t seem worth the effort…
That image is number 7915: so it’s taken a bit over two images per day for the last nine years. I can’t swear the counter has never been reset, but that seems about right.
The Smell of Molten Projects in the Morning 