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Posts Tagged CNC

YAGV Hackage

I’ve been using YAGV (Yet Another G-Code Viewer) as a quick command-line Guilloché visualizer, even though it’s really intended for 3D printing previews:

YAGV previewer.png
YAGV previewer.png

Oddly (for a command-line program), it (seems to) lack any obvious keyboard shortcut to bail out; none of my usual finger macros work.

A quick hack to the main /usr/share/yagv/yagv file makes Ctrl-Q bail out, thusly:

diff yagv /usr/share/yagv/yagv 
18a19
> import sys
364a366,367
> 		if symbol==pyglet.window.key.Q and modifiers & pyglet.window.key.MOD_CTRL:
> 			sys.exit()

I tacked the code onto an existing issue, but yagv may be a defunct project. Tweaking the source works for me.

The Ubuntu 18.04 LTS repo has what claims to be version 0.4, but the yagv GitHub repository (also claiming to be 0.4) includes code ignoring G-Code comments. Best to build the files from source (which, being Python, they already are), then add my Ctrl-Q hack, because my GCMC Guilloché generator adds plenty of comments.

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Engraving Guilloché Patterns

Flushed with success from engraving a hard drive platter for the 21HB5A tube, I bandsawed an acrylic square from a scrap sheet and unleashed the diamond drag bit on it:

Guilloche 540237875 - engraved at -0.50mm
Guilloche 540237875 – engraved at -0.50mm

That’s side-lit against a dark blue background. The long scratch and assorted dirt come from its protracted stay in the scrap pile.

If you look closely, you’ll see a few slightly wider loops, which came from a false start at Z=-0.1 mm.

Engraving at -0.5 mm looked pretty good:

Guilloche 540237875 - engraved at -0.50mm - detail
Guilloche 540237875 – engraved at -0.50mm – detail

Despite an angular resolution of 2°, the curves came out entirely smooth enough. The gritty scratchiness resulted in a pile of chaff covering the engraved area; perhaps some oil or lube or whatever would help.

Rescaling the pattern to fit a CD platter worked fine, too:

Guilloche 540237875 - CD engraving
Guilloche 540237875 – CD engraving

Polycarbonate seems to deform slightly, rather than scratch, leaving the final product with no chaff at all:

In this case, the doubled lines come from the reflection off the aluminized lower surface holding all the data.

That CD should be unreadable by now …

[Update: Welcome, Adafruit! More on Guilloché pattern generation and engraving them with the MPCNC. ]

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Debossed Printed Legends

[Update: It seems I interchanged “em” and “de” throughout this post.  ]

Up to this point, I’ve been labeling printed parts with emdebossed legends that look OK on the solid model:

Astable Multivibrator Battery Holder

Astable Multivibrator Battery Holder

Alas, the recessed letters become lost in their perimeter threads:

3D Printed Legend - Embossed

3D Printed Legend – Embossed

Raising the legend above the surface (“deembossing”) works reasonably well, but raised letters would interfere with sliding the battery into the holder and tend to get lost amid the surface infill pattern.

The blindingly obvious solution, after far too long, raises the letters above a frame embossed into the surface:

Astable Multivibrator Battery Holder - Legend Debossed

Astable Multivibrator Battery Holder – Legend Debossed

Which looks OK in the real world, too:

3D Printed Legend - Debossed

3D Printed Legend – Debossed

The frame is one thread deep and the legend is one thread tall, putting the letters flush with the surrounding surface and allowing the battery to slide smoothly.

The legend on the bottom surface shows even more improvement:

NP-BX1 battery holder - Raised vs Recessed Legend

NP-BX1 battery holder – Raised vs Recessed Legend

An OpenSCAD program can’t get the size of a rendered text string, so the fixed-size frame must surround the largest possible text, which isn’t much of a problem for my simple needs.

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Astable Multivibrator: NP-BX1 Base

Adapting the NP-BX1 battery holder to use SMT pogo pins worked well:

NP-BX1 Holder - SMT pogo pins

NP-BX1 Holder – SMT pogo pins

The next step is to add sockets for those 14 AWG wires:

NP-BX1 Battery Holder - Wire Posts - solid model

NP-BX1 Battery Holder – Wire Posts – solid model

Start by reaming / hand-drilling all the holes to their nominal size and cleaning out the pogo pin pocket.

Solder wires to the pogo pins and thread them through the holder and lid:

Astable - NP-BX1 holder - pogo pin soldering

Astable – NP-BX1 holder – pogo pin soldering

That’s nice, floppy silicone-insulated 24 AWG wire, which may be a bit too thick for this purpose.

The pogo pins will, ideally, seat with the end of the body flush at the holder wall. Make it so:

Astable - NP-BX1 holder - pogo pin protrusion

Astable – NP-BX1 holder – pogo pin protrusion

Dress the wires neatly into their pocket:

Astable - NP-BX1 holder - pogo pin wiring

Astable – NP-BX1 holder – pogo pin wiring

Butter the bottom of the lid with epoxy, clamp in place, set it up for curing, then fill the recess:

Astable - NP-BX1 base - curing

Astable – NP-BX1 base – curing

While it’s curing, make a soldering fixture for the 14 AWG wires:

Astable - drilling strut soldering fixture

Astable – drilling strut soldering fixture

The holes are on 5 mm centers, in the expectation other battery holders will need different spacing.

Solder it up and stick the wires into the base:

Astable - NP-BX1 base - detail

Astable – NP-BX1 base – detail

Jam a battery in and It Just Works™:

Astable - NP-BX1 3.8V - 20ma-div - cap V

Astable – NP-BX1 3.8V – 20ma-div – cap V

The traces:

  • Green = supply current at 20 mA/div
  • Yellow = LED driver transistor base voltage
  • Purple = other transistor collector voltage
  • White = base – collector voltage = capacitor voltage

The measurement setup was a bit of a hairball:

Astable - NP-BX1 base - current probe

Astable – NP-BX1 base – current probe

For completeness, here’s the schematic-and-layout diagram behind the circuitry:

Astable - NP-BX1 base - schematic

Astable – NP-BX1 base – schematic

I love it when a plan comes together!

The OpenSCAD source code as a GitHub Gist:

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Vacuum Tube LEDs: 21HB5A on a Guilloche Platter

With the Joggy Thing running in LinuxCNC 2.7, touching XY off on the fixture was trivially easy:

LinuxCNC - Sherline Mill - Logitech Gamepad

LinuxCNC – Sherline Mill – Logitech Gamepad

The pips are 100 mm apart at (-50,-50) and (+50,50). Astonishingly, the laser aligner batteries are in fine shape.

I should have protected the platter before drilling all those holes:

Guilloche platter - drilling

Guilloche platter – drilling

All’s well that ends well:

21HB5A - Guilloche platter

21HB5A – Guilloche platter

It looks even better in the dark, although you’d never know it from this picture:

21HB5A - Guilloche platter - dark

21HB5A – Guilloche platter – dark

I wish I could engrave those patterns on already-drilled platters, but dragging a diamond point into a hole can’t possibly end well. I could deploy the Tiny Sandblaster with a vinyl mask, if I had enough artistic eptitude to lay out a good-looking mask.

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LinuxCNC 2.7 vs. Logitech Joggy Thing

The old Atom running LinuxCNC for the Sherline finally stopped booting, so I popped the Optiplex 760 off the stack and did a live-USB trial run. The latency / jitter worked out around 25 µs, slightly worse than before, but still Good Enough, and the StepConf utility coerced the motors into working OK.

What didn’t work was the old Eagle-to-HAL code defining the Logitch Gamepad as a Joggy Thing to allow smooth joystick jog control. Well, stuff changes over the course of eight years, but, in this case, the fix turned out to be a one-liner: the probe_parport module isn’t needed nowadays.

With that out of the way, it runs fine:

LinuxCNC - Sherline Mill - Logitech Gamepad

LinuxCNC – Sherline Mill – Logitech Gamepad

The INI and HAL files defining the Sherline configuration as a GitHub Gist:

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MPCNC: Jogging Keypad for bCNC

The bCNC G-Code sender sends jogging commands to GRBL from an ordinary numeric keypad:

MPCNC - Jogging keypad

MPCNC – Jogging keypad

Unlike the keypads on my streaming radio players, this one requires no configuration at all, because bCNC regards it as just another keyboard input. The catch: you must select any screen element other than a text entry field to have bCNC recognize the keystrokes as “not text”.

You would get the same results from the numeric keys on the right side of a full-size / 104-key plank. I’m using a small “tenkeyless” keyboard, which means I can put the keypad wherever it’s easiest to reach while tweaking the MPCNC.

The ÷10 and ×10 keys along the top row alter the step size by factors of ten, which is pretty much what you need: jog to within a big step of the target, drop to the next lower decade, jog a few more times, maybe drop another decade, jog once, and you’re as close as you need to be with an MPCNC. The -1 and +1 keys aren’t as useful, at least to me: changing from 5 mm to 4 mm or 6 mm doesn’t make much difference.

Jogging to align the spindle (well, a pen or drag knife) with a target using the video camera works really well:

bCNC - Video align

bCNC – Video align

GRBL and bCNC don’t do smooth jogging and the discrete steps aren’t as nifty as the Joggy Thing with LinuxCNC, but it gets the job done.

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