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.
Mechanical widgetry
A variation on the CD fixture produces a 3.5 inch hard drive platter fixture:
Which needed just a touch of milling for a snug fit around the platter:
Tape it down on the 3018’s platform, set XY=0 at the center, and It Just Works™:
The rather faint line shows engraving at -1.0 mm = 70 g downforce isn’t quite enough. Another test with the same pattern at -3.0 mm = 140 g came out better:
It’s in the same OpenSCAD file as the CD fixture, in the unlikely event you need one.
The 4 inch column on the rear patio holds a bracket, probably intended for a welcoming sign or some such, which keeps the suet feeder mostly out of reach. It desperately wanted a coat of black paint to match the railing, so I stripped the old paint and applied Evapo-Rust:
The dark areas are iron oxide being converted to loose iron sulfide, which is what Evapo-Rust does for a living.
One could, of course, simply buy new eye screws & nuts, but we’re deep into historical preservation around here.
An hour of soaking and a few minutes of wire-wheeling got everything down to bare metal, ready for some rattle-can primer and black paint action:
It’s a version of what Eks calls a “used car finish”: high shine over deep pits.
Discussion of why one should not paint threaded parts will be unavailing; in this case, paint serves as permanent threadlock. I re-spritzed the eyescrews & nuts after getting everything aligned, so as to produce a lovely two-coat over-all finish.
The birds won’t care one way or the other and, as long as the paint lasts, neither will we.
A slight modification to the MPCNC LM12UU collet pen holder turns it into a long-reach Z-Axis Height Probe:
A flange on the top plate holds a Makerbot-style endstop switch:
The brass probe rod sports a 3/32 inch ball epoxied on its tip, although for my simple needs I could probably use the bare rod:
I clamped the rod to extend a bit beyond the plate, where it can soak up most of the switch release travel, leaving just enough to reset the clickiness after each probe:
The probe responds only to Z motion, not tip deflection in XY, so it’s not particularly good for soft objects with sloped sides, like the insole shown above. It works fine for rigid objects and should suffice to figure the modeling workflow.
The bCNC Auto-Level probe routine scans a grid over a rectangular region:
Which Meshlab turns into a solid model:
That’s the bottom of the insole probed on a 5 mm grid, which takes something over an hour to accomplish.
The OpenSCAD code as a GitHub Gist:
| // Collet pen cartridge holder using LM12UU linear bearing | |
| // Ed Nisley KE4ZNU – 2019-04-26 | |
| // 2019-06 Adapted from LM12UU drag knife holder | |
| // 2019-09 Probe switch mount plate | |
| Layout = "Build"; // [Build, Show, Puck, Mount, Plate, SwitchPlate] | |
| /* [Hidden] */ | |
| // Extrusion parameters | |
| ThreadThick = 0.25; // [0.20, 0.25] | |
| ThreadWidth = 0.40; // [0.40] | |
| // Constants | |
| 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,$fn=Sides); | |
| } | |
| //- Dimensions | |
| // Basic shape of DW660 snout fitting into the holder | |
| // Lip goes upward to lock into MPCNC mount | |
| Snout = [44.6,50.0,9.6]; // LENGTH = ID height | |
| Lip = 4.0; // height of lip at end of snout | |
| // Holder & suchlike | |
| PenShaft = 3.5; // hole to pass pen cartridge | |
| WallThick = 4.0; // minimum thickness / width | |
| Screw = [4.0,8.5,25.0]; // thread ID, washer OD, length | |
| Insert = [4.0,6.0,10.0]; // brass insert | |
| Bearing = [12.0,21.0,30.0]; // linear bearing body | |
| Plate = [PenShaft,Snout[OD] – WallThick,WallThick]; // spring reaction plate | |
| echo(str("Plate: ",Plate)); | |
| SpringSeat = [0.56,7.5,2*ThreadThick]; // wire = ID, coil = OD, seat depth = length | |
| PuckOAL = max(Bearing[LENGTH],(Snout[LENGTH] + Lip)); // total height of DW660 fitting | |
| echo(str("PuckOAL: ",PuckOAL)); | |
| Key = [Snout[ID],25.7,(Snout[LENGTH] + Lip)]; // rectangular key | |
| NumScrews = 3; | |
| //ScrewBCD = 2.0*(Bearing[OD]/2 + Insert[OD]/2 + WallThick); | |
| ScrewBCD = (Snout[ID] + Bearing[OD])/2; | |
| echo(str("Screw BCD: ",ScrewBCD)); | |
| NumSides = 9*4; // cylinder facets (multiple of 3 for lathe trimming) | |
| // MBI Endstop switch PCB | |
| PCB = [40.0,1.6,16.5]; // endstop PCB, switch downward, facing parts | |
| Touchpoint = [-4.8,4.8,4.5]; // contact point from PCB edges, solder side | |
| TapeThick = 1.0; // foam mounting tape | |
| SwitchMount = [PCB.x,WallThick,PCB.z + Touchpoint.z + Plate.z]; | |
| module DW660Puck() { | |
| translate([0,0,PuckOAL]) | |
| rotate([180,0,0]) { | |
| cylinder(d=Snout[OD],h=Lip/2,$fn=NumSides); | |
| translate([0,0,Lip/2]) | |
| cylinder(d1=Snout[OD],d2=Snout[ID],h=Lip/2,$fn=NumSides); | |
| cylinder(d=Snout[ID],h=(Snout[LENGTH] + Lip),$fn=NumSides); | |
| translate([0,0,(Snout[LENGTH] + Lip) – Protrusion]) | |
| cylinder(d1=Snout[ID],d2=2*WallThick + Bearing[OD],h=PuckOAL – (Snout[LENGTH] + Lip),$fn=NumSides); | |
| intersection() { | |
| translate([0,0,0*Lip + Key.z/2]) | |
| cube(Key,center=true); | |
| cylinder(d=Snout[OD],h=Lip + Key.z,$fn=NumSides); | |
| } | |
| } | |
| } | |
| module MountBase() { | |
| difference() { | |
| DW660Puck(); | |
| translate([0,0,-Protrusion]) // bearing | |
| PolyCyl(Bearing[OD],2*PuckOAL,NumSides); | |
| for (i=[0:NumScrews – 1]) // clamp screws | |
| rotate(i*360/NumScrews) | |
| translate([ScrewBCD/2,0,-Protrusion]) | |
| rotate(180/8) | |
| PolyCyl(Insert[OD],2*PuckOAL,8); | |
| } | |
| } | |
| module SpringPlate() { | |
| difference() { | |
| cylinder(d=Plate[OD],h=Plate[LENGTH],$fn=NumSides); | |
| translate([0,0,-Protrusion]) // pen cartridge hole | |
| PolyCyl(PenShaft,2*Plate[LENGTH],NumSides); | |
| translate([0,0,Plate.z – SpringSeat[LENGTH]]) // spring retaining recess | |
| PolyCyl(SpringSeat[OD],SpringSeat[LENGTH] + 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*PuckOAL,8); | |
| } | |
| } | |
| module SwitchPlate() { | |
| translate([0,0,Plate.z]) | |
| rotate([180,0,0]) | |
| SpringPlate(); | |
| rotate(45) | |
| translate([Touchpoint.x,Touchpoint.y + TapeThick,0]) | |
| cube(SwitchMount,center=false); | |
| } | |
| //—– | |
| // Build it | |
| if (Layout == "Puck") | |
| DW660Puck(); | |
| if (Layout == "Plate") | |
| SpringPlate(); | |
| if (Layout == "SwitchPlate") | |
| SwitchPlate(); | |
| if (Layout == "Mount") | |
| MountBase(); | |
| if (Layout == "Show") { | |
| MountBase(); | |
| translate([0,0,1.6*PuckOAL]) | |
| rotate([180,0,0]) | |
| SpringPlate(); | |
| } | |
| if (Layout == "Build") { | |
| translate([0,Snout[OD]/2,PuckOAL]) | |
| rotate([180,0,0]) | |
| MountBase(); | |
| translate([0,-Snout[OD]/2,0]) | |
| SpringPlate(); | |
| } |
Back in the early 90s, I bought a Branson Ultrasonic Cleaner for small parts. It turned out to be ideal for eyeglasses, migrated to the bathroom, and has been used at least daily ever since. After nigh onto three decades, this happened:
We tend to push the ON button and let it turn off by itself after a little over four minutes (exactly 255 seconds!), so the gray plastic sheet over the ON switch failed first. You can barely see the outline of the transparent film previously covering both switches, which probably helped waterproof the switches.
The gray plastic disk sits atop the switch actuator, so I punched a slightly larger polypropylene disk (from my stash of clamshell packages), stuck it to the disk with double-sided tape, lined it up over the hole, and covered the mess with Kapton tape:
This is in the nature of an expedient fix, as I’m not sure the polypro disk is flexible enough. The next iteration will cover the entire gray area and I’ll see about a transparent tape covering.
Maybe in another decade?
Taping the CD fixture to the CNC 3018-Pro’s raised platform solves the repeatability problem by putting the CD at a fixed location relative to the machine’s Home coordinates. The next step puts the XY=0 coordinate origin at the exact center of the platter, so the pattern comes out exactly centered on the disc:
The fixture has a central boss:
The blue boss centers the CD’s hub hole, the red plateau supports the disc, and the white background lies 5 mm below the CD’s upper surface:
Yup, red and blue Sharpies FTW.
The bCNC probe camera image includes two faint cyan rings centered on the crosshair:
Set the diameter to 15 mm (or a bit less), center the outer ring on the hub hole = the border between blue & red, set XY=0, and it’s within maybe ±0.1 mm of the true center.
Done!
I’m sure I’ll do this again some time …
Focus the camera at whatever distance needed to clear the longest tooling you’ll use or, at least, some convenient distance from the platform. You must touch off Z=0 at the surface before using bCNC’s probe camera alignment, because it will move the camera to the preset focus distance.
Align the camera’s optical axis perpendicular to the table by making it stare into a mirror flat on the platform, then tweaking the camera angles until the crosshair centers on the reflected lens image. This isn’t dead centered, but it’s pretty close:
The camera will be focused on the mirror, not the reflection, as you can tell by the in-focus crud on the mirror. Whenever you focus the lens, you’ll probably move the optical axis, so do the best you can with the fuzzy image.
You can adjust small misalignments with the Haircross (seems backwards to me) Offset values.
A cheap camera’s lens barrel may not be aligned with its optical axis, giving the lens a jaunty tilt when it’s correctly set up:
With the camera focus set correctly, calibrate the camera Offset from the tool (a.k.a. Spindle) axis:
Calibrate the Crosshair ring diameter thusly:
For example, calibrating the diameter to 10 mm against a shop scale:
At 10 mm above the CD, setting the camera’s resolution to 11.5 pixel/mm:
Makes the outer circle exactly 15.0 mm in diameter to match the CD hub ring ID:
I doubt anybody can find the pixel/mm value from first principles, so you must work backwards from an object’s actual size.
The smaller and more rigid CNC 3018-Pro should be able to engrave text faster than the larger and rather springy MPCNC, which could engrave text at about 50 mm/min. This test pattern pushes both cutting depth and engraving speed to absurd values:
Compile the GCMC source to generate G-Code, lash a CD / DVD to the platform (masking tape works fine), touch off the XY coordinates in the center, touch off Z=0 on the surface, then see what happens:
The “engraving depth” translates directly into the force applied to the diamond point, because the spring converts displacement into force. Knowing the Z depth, you can calculate or guesstimate the force.
Early results from the 3018 suggest it can engrave good-looking text about 20 times faster than the MPCNC:
You must trade off speed with accuracy on your very own machine, as your mileage will certainly differ!
The GCMC source code as a GitHub Gist:
| // Engraving test piece | |
| // Ed Nisley KE4ZNU – 2019-09 | |
| //—– | |
| // Command line parameters | |
| // -D OuterDia=number | |
| if (!isdefined("OuterDia")) { | |
| OuterDia = 120mm – 2mm; // CD = 120, 3.5 inch drive = 95 | |
| } | |
| OuterRad = OuterDia / 2.0; | |
| comment("Outer Diameter: ",OuterDia); | |
| comment(" Radius: ",OuterRad); | |
| //—– | |
| // Library routines | |
| include("tracepath.inc.gcmc"); | |
| include("engrave.inc.gcmc"); | |
| //—– | |
| // Bend text around an arc | |
| function ArcText(TextPath,Center,Radius,BaseAngle,Align) { | |
| PathLength = TextPath[-1].x; | |
| Circumf = 2*pi()*Radius; | |
| TextAngle = to_deg(360 * PathLength / Circumf); | |
| AlignAngle = BaseAngle + (Align == "Left" ? 0 : | |
| Align == "Center" ? -TextAngle / 2 : | |
| Align == "Right" ? -TextAngle : | |
| 0); | |
| ArcPath = {}; | |
| foreach(TextPath; pt) { | |
| if (!isundef(pt.x) && !isundef(pt.y) && isundef(pt.z)) { // XY motion, no Z | |
| r = Radius – pt.y; | |
| a = 360deg * (pt.x / Circumf) + AlignAngle; | |
| ArcPath += {[r*cos(a) + Center.x, r*sin(a) + Center.y,-]}; | |
| } | |
| elif (isundef(pt.x) && isundef(pt.y) && !isundef(pt.z)) { // no XY, Z up/down | |
| ArcPath += {pt}; | |
| } | |
| else { | |
| error("Point is not pure XY or pure Z: " + to_string(pt)); | |
| } | |
| } | |
| return ArcPath; | |
| } | |
| //—– | |
| // Set up for drawing | |
| SafeZ = 10.0mm; // above clamps and screws | |
| TravelZ = 1.0mm; // above workpiece | |
| PlotZ = -0.5mm; // tune for best results | |
| TextSpeed = 1000mm; // intricate detail | |
| DrawSpeed = 2000mm; // smooth curves | |
| TextFont = FONT_HSANS_1_RS; | |
| TextSize = [2.0mm,2.0mm]; | |
| TextLeading = 2*TextSize.y; // line spacing | |
| DiskCenter = [0mm,0mm]; // middle of the platter | |
| InnerDia = 40mm; | |
| InnerRad = InnerDia / 2.0; | |
| comment("Inner Diameter: ",InnerDia); | |
| comment(" Radius: ",InnerRad); | |
| NumRings = ceil((OuterRad – (InnerRad + TextLeading))/TextLeading); // number of rings to draw | |
| comment("Numer of rings: ",NumRings); | |
| if (1) { | |
| comment("Text Size begins"); | |
| feedrate(TextSpeed); | |
| ts = "Text size: " + to_string(TextSize); | |
| tp = scale(typeset(ts,TextFont),TextSize); | |
| tpa = ArcText(tp,DiskCenter,OuterRad,90deg,"Left"); | |
| engrave(tpa,TravelZ,PlotZ); | |
| } | |
| if (1) { | |
| comment("Depth variations begin"); | |
| TextRadius = OuterRad; | |
| pz = 0.0mm; | |
| repeat(NumRings ; i) { | |
| comment(" depth: " + to_string(pz)); | |
| feedrate(TextSpeed); | |
| ts = "Depth: " + to_string(pz) + " at " + to_string(TextSpeed) + "/min"; | |
| tp = scale(typeset(ts,TextFont),TextSize); | |
| tpa = ArcText(tp,DiskCenter,TextRadius,-5deg,"Right"); | |
| engrave(tpa,TravelZ,pz); | |
| feedrate(DrawSpeed); | |
| goto([0,-TextRadius,-]); | |
| move([-,-,pz]); | |
| arc_ccw([-TextRadius,0,-],-TextRadius); | |
| goto([-,-,TravelZ]); | |
| feedrate(TextSpeed); | |
| tp = scale(typeset("Rad: " + to_string(TextRadius),TextFont),TextSize); | |
| tpa = ArcText(tp,DiskCenter,TextRadius,180deg,"Right"); | |
| engrave(tpa,TravelZ,PlotZ); | |
| TextRadius -= TextLeading; | |
| pz -= 0.10mm; | |
| } | |
| } | |
| if (1) { | |
| comment("Feedrate variations begin"); | |
| TextRadius = OuterRad; | |
| ps = 250mm; | |
| repeat(NumRings ; i) { | |
| comment(" speed: " + to_string(ps) + "/min"); | |
| feedrate(ps); | |
| ts = "Speed: " + to_string(ps) + "/min at " + to_string(PlotZ); | |
| tp = scale(typeset(ts,TextFont),TextSize); | |
| tpa = ArcText(tp,DiskCenter,TextRadius,5deg,"Left"); | |
| engrave(tpa,TravelZ,PlotZ); | |
| TextRadius -= TextLeading; | |
| ps += 250mm; | |
| } | |
| } | |
| if (1) { | |
| comment("Off-center text arcs begin"); | |
| feedrate(TextSpeed); | |
| tc = [-40mm/sqrt(2),-40mm/sqrt(2)]; // center point | |
| r = 3mm; | |
| s = [0.5mm,0.5mm]; | |
| ts = "Radius: " + to_string(r) + " Size: " + to_string(s); | |
| tp = scale(typeset(ts,TextFont),s); | |
| tpa = ArcText(tp,tc,r,0deg,"Center"); | |
| engrave(tpa,TravelZ,PlotZ); | |
| r = 5mm; | |
| s = [1.0mm,1.0mm]; | |
| ts = "Radius: " + to_string(r) + " Size: " + to_string(s); | |
| tp = scale(typeset(ts,TextFont),s); | |
| tpa = ArcText(tp,tc,r,0deg,"Center"); | |
| engrave(tpa,TravelZ,PlotZ); | |
| r = 8mm; | |
| s = [1.5mm,1.5mm]; | |
| ts = "Radius: " + to_string(r) + " Size: " + to_string(s); | |
| tp = scale(typeset(ts,TextFont),s); | |
| tpa = ArcText(tp,tc,r,0deg,"Center"); | |
| engrave(tpa,TravelZ,PlotZ); | |
| r = 15mm; | |
| s = [3.0mm,3.0mm]; | |
| ts = "Radius: " + to_string(r) + " Size: " + to_string(s); | |
| tp = scale(typeset(ts,FONT_HSCRIPT_2),s); | |
| tpa = ArcText(tp,tc,r,0deg,"Center"); | |
| engrave(tpa,TravelZ,PlotZ); | |
| } | |
| if (1) { | |
| comment("Attribution begins"); | |
| feedrate(TextSpeed); | |
| tp = scale(typeset("Ed Nisley – KE4ZNU – softsolder.com",TextFont),TextSize); | |
| tpa = ArcText(tp,DiskCenter,15mm,0deg,"Center"); | |
| engrave(tpa,TravelZ,PlotZ); | |
| tp = scale(typeset("Engraving Test Disc",TextFont),TextSize); | |
| tpa = ArcText(tp,DiskCenter,15mm,180deg,"Center"); | |
| engrave(tpa,TravelZ,PlotZ); | |
| } | |
| goto([-,-,SafeZ]); | |
| goto([0mm,0mm,-]); | |
| comment("Done!"); |
| #!/bin/bash | |
| # Engraving test pattern generator | |
| # Ed Nisley KE4ZNU – 2019-08 | |
| Diameter='OuterDia=116mm' | |
| Flags='-P 3 –pedantic' | |
| # Set these to match your file layout | |
| LibPath='/opt/gcmc/library' | |
| Prolog='/mnt/bulkdata/Project Files/CNC 3018-Pro Router/Patterns/gcmc/prolog.gcmc' | |
| Epilog='/mnt/bulkdata/Project Files/CNC 3018-Pro Router/Patterns/gcmc/epilog.gcmc' | |
| Script='/mnt/bulkdata/Project Files/CNC 3018-Pro Router/Patterns/Engraving Test.gcmc' | |
| ts=$(date +%Y%m%d-%H%M%S) | |
| fn='TestPattern_'${ts}'.ngc' | |
| echo Output: $fn | |
| rm -f $fn | |
| echo "(File: "$fn")" > $fn | |
| /opt/gcmc/src/gcmc -D $Diameter $Flags \ | |
| –include "$LibPath" –prologue "$Prolog" –epilogue "$Epilog" \ | |
| "$Script" >> $fn | |
The Smell of Molten Projects in the Morning 