Tag: Improvements

Making the world a better place, one piece at a time

MPCNC: Modified Drag Knife Adapter

A trio of Cutter Cutting Plotter Blade Holders arrived:

Despite the name, they’re not well-suited for drag knife blades, because they’re collets gripping a 2 mm shaft. The blade doesn’t rotate unless the plotter / cutter rotates the entire holder, which is actually a thing.

I got ’em because the snout of a common ball-point pen refill measures about 2 mm:

Collet pen holder - detail — Collet pen holder – detail

The glob around the tip comes from plotting too fast for conditions; about 1500 mm/min works better for continuous lines and 250 mm/min improves text.

The stock MPCNC adapter has a single recess suited for Genuine Plotter Pens, but the knurled lock ring on these cheapies sticks out far enough to make them wobbly. This being an inconvenience up with which I need not put, a few lines of OpenSCAD tweak the stock STL:

MPCNC knife adapter mods - OpenSCAD model — MPCNC knife adapter mods – OpenSCAD model

The original STL is ivory, new cuts are cyan, and additions are reddish.

The two support beams are now 1.6 mm = four thread widths, for improved slicing with a 0.35 mm nozzle and a higher spring constant.

It’s by-and-large indistinguishable from the old adapter:

MPCNC - Pen Holder Detail — MPCNC – Pen Holder Detail

Which I was using upside-down, because the flange fit better.

The MPCNC works reasonably well as a pen plotter with a genuine ballpoint pen:

The OpenSCAD source code as a GitHub Gist:

	// Adding clearance for eBay collet pen holder

	MPCNC_OD = 12.0; // pen holder OD (matches STL curvature)
	MPCNC_Z = 8.9; // Z offset of pen axis

	Pen_OD = 11.5; // actual pen body OD

	ID = 0;
	OD = 1;
	LENGTH = 2;

	Flange = [11.5,15.7,2.2]; // actual pen body flange

	Locknut = [16.0,16.0,2.8]; // knurled locknut
	Locknut_Offset = 4.5; // flange center to locknut

	Wall = [41.0,4 * 0.4,9.0]; // thicker walls for more spring and better fill

	$fn = 32; // default cylinder sides

	difference() {
	translate([-(101.3 + MPCNC_OD/2),-111.9,0]) // put pen axis above Y axis, flange centered on X axis
	import("/mnt/bulkdata/Project Files/Mostly Printed CNC/Accessories/Tool Holders/MPCNC_525_Drag_Knife-1860310.STL",
	convexity=5);

	if (true) // improve holder-to-mount fit if needed
	translate([0,60/2,8.90])
	rotate([90,0,0])
	cylinder(d=MPCNC_OD,h=60);

	translate([0,0,MPCNC_Z]) // improve flange slot clearance
	rotate([90,0,0])
	cylinder(d=Flange[OD] + 1.0,h=Flange[LENGTH] + 0.5,center=true);

	translate([0,Locknut_Offset – 0.5,MPCNC_Z]) // add locknut clearance
	rotate([-90,0,0])
	cylinder(d=Locknut[OD] + 1.5,h=Locknut[LENGTH] + 1.5,center=false);
	}

	# translate([-(27.0 + Wall.x/2),0,0]) { // embiggen walls for higher spring constant
	translate([0,-24.4,0])
	cube(Wall);
	translate([0,20.6 – Wall.y,0])
	cube(Wall);
	}

view raw MPCNC Drag Knife Adapter – Collet Pen Mod.scad hosted with ❤ by GitHub

2018-10-08

Adulting 101

The library runs courses teaching useful skills:

Adulting 101 – Car Maintenance

The classes cover the basics of home finance, cooking, sewing, and suchlike.

I could have used a few Adulting courses, back in the day.

2018-10-06
Halogen Desk Lamp Conversion: Preliminaries

A discarded 20 W halogen desk lamp arrived in the Basement Laboratory for rebuilding:

Halogen Desk Lamp – head layout

An incandescent bulb doesn’t care about AC or DC, so a simple transformer also serves as a counterweight in the base:

Halogen Desk Lamp – 12 V 20 W transformer

I might replace it with some steel sheets, although I have no immediate need for a bare transformer.

A case adds 19¢ to each 10 W 300 mA LED driver:

Halogen Desk Lamp – 10 W LED driver innards

Nice strain relief on those line-voltage wires, eh?

A simple test setup with three 3 W COB LED panels:

Halogen Desk Lamp – 3x3W COB LED test

I clamped them to the aluminum sheet for heatsinking before I lit ’em up. The circles traced directly from the lamp’s hardware give some idea of the eventual layout.

I have more-intense LEDs, but spreading the light over a larger area should work better for the intended purpose. These are pleasant warm-white LEDs, too.

The fourth LED raised the forward voltage beyond the supply’s 42 V maximum, causing the supply to blink on and off.

Much to my surprise, the driver has plenty of 60 Hz ripple:

COB LED 3x3W – 10 W driver – 100 mA-div 10 V-div

The top trace averages 280 mA and the bottom trace 32 V, so the LEDs run at 9 W = 3 W apiece, as they should.

Now, for some metalworking …

2018-10-05
Burnett Blvd Signals: Five More Seconds!

My most recent description of not quite getting killed in front of the NYS DOT Region 8 office evidently did some good. Although I wasn’t informed directly, this happened:

The minimum green time was increased to 10 seconds.

Which is five more seconds more than before, allowing us to get nearly all the way through the intersection before crossing traffic on Rt 55 gets a green light.

As before, the numbers are video frames at 60 fps.

T=0.0 – Burnett signal goes green:

Burnett – New signal timing – 0101 – 2018-09-30

T=2.5 – The trailer ahead of us starts and we’re rolling:

Burnett – New signal timing – 0251 – 2018-09-30

T=8.0 – We reach the Burnett crosswalk. Note the car beside us isn’t making much headway, either:

Burnett – New signal timing – 0581 – 2018-09-30

T=11.93 – Burnett signal goes yellow overhead, so the green phase lasted 12 seconds:

Burnett – New signal timing – 0817 – 2018-09-30

T=16.16 – Rt 55 signal remains red, but will change within a second:

Burnett – New signal timing – 1071 – 2018-09-30

Seen from the rear view camera, the Rt 55 signal went green while we were still in the intersection:

Burnett – New signal timing – 16 s – crossing green – 2018-09-30

You’ll note the cars on Rt 55 behind us weren’t visible three seconds earlier, so, as far as they can tell, we’re running the red.

Fortunately, we’re almost where we need to be:

Burnett – New signal timing – 22 s – traffic – 2018-09-30

The timing still isn’t safe, but after three years, five more seconds counts for a lot!

2018-10-04
Magnifying Desk Lamp Pivot Clamp Repair

The clamp holding the magnifying lamp (with a fluorescent ring light!) over the Basement Laboratory Desk finally fractured:

Magnifying Lamp Pivot – broken parts

Gorilla Tape held the broken parts together well enough to determine how it used to work:

Magnifying Lamp Pivot – hole sizing

The two parts used to be 11.2 mm thick, but it fit on a random chunk of half-inch aluminium plate so perfectly as to constitute a Good Omen:

Magnifying Lamp Pivot – stock layout

I decided the saw kerf would make up the difference, because, sheesh, we’re talking pot metal here.

Lay out the center, use a transfer punch the same diameter as the lamp pivot to get the proper spacing, give it a whack:

Magnifying Lamp Pivot – hole marking

The alert reader will note I came that close to drilling the hole through the wrong side of the angle.

And, yes, extrapolating the vertical edge downward suggests the large hole-to-be will intersect the small hole-in-being. This is deliberate: the clamp screw through the smaller hole fits into a recess around the lamp pivot shaft to keep it from sliding to-and-fro. I had to convince myself, but it really did work out OK.

Pay some attention to clamping it at right angles to the spindle so the big hole goes through more-or-less in the right direction:

Magnifying Lamp Pivot – drill press alignment

The masking tape serves as a depth reminder:

Magnifying Lamp Pivot – drilling

Set it up in a machinist’s clamp, bandsaw in twain, file the kerf reasonably flat, clamp the halves together, then bandsaw the clearance slot:

Magnifying Lamp Pivot – clearance slot

The clearance kerf wasn’t nearly as on-center as I wanted, which doesn’t really matter, but I filed a bit more diligently on the shallow side while clearing up the slot:

Magnifying Lamp Pivot – clearance filing

Introducing the new parts to Mr Disk Sander roundified them enough to pass inspection. These angular bits obviously require a bit more attention to detail:

Magnifying Lamp Pivot – parts

The lamp originally had a fancy knob on the screw which never worked particularly well, so I replaced it with a nylon locking nut to maintain a reasonable amount of pressure:

Magnifying Lamp Pivot – installed

The far end of the screw has a square shaft fitting into a square hole in the lamp arm, making it easy to torque the nut enough to make the pivot grip the shaft properly; if I ever find my Belleville washer stash again, I’ll add one. I should cut the screw off, too, but that’s definitely in the nature of fine tuning.

A pleasant morning of Quality Shop Time!

The obligatory doodle with dimensions, some of which turned out to be completely incorrect:

Magnifying Lamp Pivot – dimension doodles

2018-10-03
Pi-Hole with DNS-over-HTTPS
With none other than Troy Hunt recommending Pi-Hole, I got a Round Tuit:
```
unzip 2018-06-27-raspbian-stretch-lite.zip -d /tmp
sudo dcfldd status=progress bs=1M of=/dev/sde if=/tmp/2018-06-27-raspbian-stretch-lite.img
```
Raspbian now arrives with ssh disabled, so the first boot requires a keyboard and display:

Pi-Hole first boot wiring

Then do some configuration required to get a fresh Raspberry Pi ready for remote access:
```
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install screen iotop
sudo raspi-config   # enable ssh
ssh-keygen -t rsa
cd ~/.ssh
cp -a /my/public/key authorized_keys
chmod go-rwx authorized_keys
cd
sudo nano /etc/ssh/sshd_config  # unusual port, no root login, etc
sudo service ssh restart
```
As the good folks at Pi-Hole say, “Piping to bash is controversial, as it prevents you from reading code that is about to run on your system.” I took a look, it’s beyond my comprehension, so just get it done:
```
curl -sSL https://install.pi-hole.net | bash
```
Configure Pi-Hole:
- Static IP: 192.168.1.2/24
- DNS using, say, Cloudflare’s 1.1.1.1
- DHCP turned off, which is the default
Configure the router’s DHCP to hand out the Pi-Hole’s IP, with, say, 9.9.9.9 as a backup.

Boot a few random PCs and whatnot to verify it works as expected, which it did the second time around, thus this particular post.

Install the Cloudflare Argo Tunnel dæmon, approximately according to suggestions:
```
mkdir Downloads
cd Downloads/
wget https://bin.equinox.io/c/VdrWdbjqyF/cloudflared-stable-linux-arm.tgz
tar zxvf cloudflared-stable-linux-arm.tgz
sudo mkdir /opt/cloudflare
sudo cp cloudflared /opt/cloudflare/
```
Start the daemon from within a screen session, also as suggested:
```
sudo /opt/cloudflare/cloudflared proxy-dns --port 54 --upstream https://1.1.1.1/.well-known/dns-query --upstream https://1.0.0.1/.well-known/dns-query
INFO[0000] Adding DNS upstream                           url="https://1.1.1.1/.well-known/dns-query"
INFO[0000] Adding DNS upstream                           url="https://1.0.0.1/.well-known/dns-query"
INFO[0000] Starting metrics server                       addr="127.0.0.1:37777"
INFO[0000] Starting DNS over HTTPS proxy server          addr="dns://localhost:54"
```
Contrary to the suggestions, you can configure Pi-Hole to use the DoH tunnel (or whatever it’s called) by tweaking its upstream DNS configuration:

Pi-Hole – Cloudflare DNS config

Then set up systemd to start the daemon automagically:
```
sudo nano /etc/systemd/system/dnsproxy.service
```
Because I put the daemon in /opt/cloudflare, that file differs slightly from the suggestion:
```
[Unit]
Description=CloudFlare DNS over HTTPS Proxy
Wants=network-online.target
After=network.target network-online.target

[Service]
ExecStart=/opt/cloudflare/cloudflared proxy-dns --port 54 --upstream https://1.1.1.1/.well-known/dns-query --upstream https://1.0.0.1/.well-$
Restart=on-abort
 
[Install]
WantedBy=multi-user.target
```
And then It Just Worked.

Controversies over the ethics of ad and tracker blocking will go nowhere here, as I’ve cleaned out enough Windows machines to have absolutely no sympathy with the unholy spawn of adtech (not just the company, which I didn’t know existed until just now, but, yeah, them too).
2018-10-02
Brush Clearing

Some recent brush-clearing along our usual bicycle routes:

This slideshow requires JavaScript.

The bushes with oval leaves are Blackthorn, of which Wikipedia says “The shrub, with its savage thorns, is traditionally used […] to make a cattle-proof hedge.” They’re commonly found along the untamed border of Rt 376, as well as the rail trail.

It’s more effective than expecting my tax dollars to wake up and get to work …

2018-09-30