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
The V4 hot end reduced the clearance under the X-axis gantry to the point where a bight of wire from the white LED panels drooped onto the platform during homing. A bit of snipping, drilling, and filing produced a clip from the same steel strap that’s holding the Z-axis switch cable against the gantry:
That was easy…
Mounting the Z-axis platform switch on the X gantry to sense the actual platform position worked perfectly with the original MakerGear V3 hot end, at least after I relocated the switch a bit further from the balance point. It does require moving the nozzle off the platform before homing the Z axis, for the obvious reason:
The smaller MakerGear V4 hot end uses a completely different mount that puts the nozzle higher than the switch lever:
The clearances were close enough to rule out plastic, so I bandsawed some 33 mil (1/32 inch) brass shim stock and drilled holes in the appropriate spots:
After discovering the blindingly obvious fact that you can’t heat brass sheets clamped to a steel vise enough to melt silver solder, I padded the brass with cardboard insulation and tried again:
The cardboard charred and burned and stank up the shop, but held everything in alignment long enough:
A bit of file & sandpaper work shined it up just fine, then I slotted the lower mounting holes enough to accommodate 2-56 nuts between the gantry and the bracket:
Yeah, I could tap 2-56 holes into the brass sheet, but let’s be reasonable: two turns does not a secure fitting make.
Here’s why a plastic bracket wouldn’t work:
That’s with the V4 hot end aligned per instructions, although I may rotate it 1/4 turn clockwise at some point. Note that there’s no filament going in the top, as I did all this before firing that devil up for the first time.
The switch lever had enough free travel that the platform would hit the bottom of the X axis linear slide screws before activating the switch, but lowering the switch would put the lever below the nozzle. I added a 15 mil brass shim to the lever and it’s all good:
Admittedly, the lever rests a bit less than 1.000 mm above the nozzle, but we’ll see how much trouble that causes.
The switch trips 2.0 mm above the nozzle, so the new startup G-Code looks like this:
;-- Slic3r Start G-Code for M2 starts -- ; Ed Nisley KE4NZU - 2015-03-01 ; Makergear V4 hot end ; Z-min switch at platform, must move nozzle to X=135 to clear M140 S[first_layer_bed_temperature] ; start bed heating G90 ; absolute coordinates G21 ; millimeters M83 ; relative extrusion distance G92 Z0 ; set Z to zero, wherever it might be now G1 Z10 F1000 ; move platform downward to clear nozzle; may crash at bottom G28 Y0 ; home Y to clear plate, origin in middle G92 Y-127 G28 X0 ; home X, origin in middle G92 X-100 G1 X130 Y0 F30000 ; move off platform to right side, center Y G28 Z0 ; home Z to platform switch, with measured offset G92 Z-2.00 G0 Z2.0 ; get air under switch G0 Y-127 F10000 ; set up for priming, zig around corner G0 X0 ; center X G0 Y-125.0 ; just over platform edge G0 Z0 F500 ; exactly at platform M109 S[first_layer_temperature] ; set extruder temperature and wait M190 S[first_layer_bed_temperature] ; wait for bed to finish heating G1 E20 F300 ; prime to get pressure, generate blob on edge G0 Y-123 ; shear off blob G1 X15 F20000 ; jerk away from blob, move over surface G4 P500 ; pause to attach G1 X45 F500 ; slowly smear snot to clear nozzle G1 Z1.0 F2000 ; clear bed for travel ;-- Slic3r Start G-Code ends --
The prime-and-wipe section accommodates gooey PETG, although that will require more attention.
A Netgear GS308 gigabit switch replaced an older 100 Mb/s switch below the living room window across from my desk:
Of course, the mounting slots in the new switch didn’t match those in the old switch. A scrap of plastic sheet serves as a space transformer:
The odd-looking knife plows a furrow in the plastic, after which you capture the sheet between two flat surfaces and snap it along the scribe. Faster / easier / more accurate / less exciting than bandsawing, cleans up with quick swipes from an edge deburring tool, not much can go wrong.
The top holes are 3/16 inch for the existing mounting screws. The center holes are tapped 6-32 with nuts to hold them in place.
A block of closed-cell foam behind the sheet holds it vertical so I can just barely see the activity LEDs at each port from my desk.
Yes, I scrubbed the sheet before mounting it…
Memo to Self: put the screw holes slightly higher, so they’re properly centered after sliding the case into position. Otherwise, you must cut another slice off the top of the sheet before mounting it.
One of the bolts from the replacement muffler on the MTD snowblower worked its way out of the engine block and vanished along the driveway, perhaps to be found when the snow vanishes in a few months. The muffler’s still in place, but the engine exhaust comes straight out of the port into that compartment and, because I’m running the engine a bit rich to make up for oxygenated gasoline, a beautiful blue flame jets about two inches from the bolt hole.
Being that sort of guy, I installed one of the original bolts that I’d tossed into the bin with its relatives and continued the mission.
For future reference:
The bolt has, of course, delightfully custom specs: 5/16-18 x 4-3/16.
My bolt stash tops out at 4 inches, so that not-quite-1/4 inch extra length means you gotta buy an OEM bolt.
They’re $1.20 from Jack’s Small Engines, with five bucks of shipping, or you can find a kit with two bolts and the lock bracket for $12 on Amazon.
No pix, because it’s 14 °F outside and barely more than that in the garage.
Our Larval Engineer expressed a need for some monitors, so I dispatched a pair of IBM L191p panels from the heap. Despite reusing a gargantuan box from the Dell U2713HM monitor, I had to disassemble the struts from their swiveling base to fit everything inside.
The intact base has no obvious affordance to remove the covers:
After taking the bottom apart, I discovered that you just poke a screwdriver under each cover and it slides upward and off:
Duh & similar remarks.
The two covers are not interchangeable:
Removing two pairs of screws from each strut releases them from the base:
The projecting horns on the outboard side of those struts are exactly as delicate as you think.
I put a piece of thick cardboard sheathed in closed-cell foam between the LCD screens that separated their bezels (minus cutouts for the buttons), then taped them together face-to-face. Add foam peanuts, drop in the monitors, nestle struts beside monitors, add rigid foam blocks all around and between, put flat bases atop monitors with a foam slab protecting those strut brackets, over-stuff the box with more peanuts, forcibly tape the thing closed, and it survived the trip in good order.
A pair of 1280×1024 monitors isn’t worth insuring these days, though.
The Dell 2005FPW monitor that I’d been using in portrait mode suffered the common failure of rebooting itself, which suggested failing capacitors. Despite my reservations, I dropped eleven bucks on a repair kit containing exactly the right caps (from sunny California via eBay), hauled the carcass to a couple of Squidwrench sessions, replaced the offending caps, and it’s all good again.
No pix of the recapping, but a few notes that may prove useful next time.
The standard advice from the usual Internet Sages recommends prying the bezel apart along the nearly invisible outside joint. I did that, then found the user manuals and the Fine Repair Manual and discovered that you jam your fingernails under the inside of the bezel against the LCD screen, pry upward, rotate / bend the bezel around its outer edge, and it Just Pops Off. I doubt it’s that easy, but …
You should start from the top of the bezel, because the PCB behind the buttons & LEDs along the bottom doesn’t have a whole lot of slack in its cable. This shows the PCB and disconnected cable:
Just pull the small brown latch away from the cable and the cable will slide out. That would be significantly easier if the socket were on the backside of the PCB, but you must pop the PCB out of its own latches before you get access to the socket latch. Rotate the bezel carefully around the PCB and maybe it’ll survive.
The pushbutton that releases the stand’s not-quite-a-VESA-mount bracket remains in place when you remove the rear cover, held in place by a wedge:
It is, however, the only thing sticking that far out of the back surface and, if you leave it alone, it will eventually release itself from captivity, whereupon its spring will fire it across the room. You have been warned.
Reassembly is in reverse order, although I didn’t snap the button-and-LED PCB firmly into place. Fixing that will require dismounting the bezel again, which I’m so not doing for a 1 mm gap along the bottom edge.
For reasons which are, trust me on this, not relevant here, we now have a third Kenmore 158 sewing machine: a freebie that sat under a roof leak in an unused room some years ago and wasn’t cleaned before being stored. Even though not much water got inside the covers, the bobbin winder shaft froze solid.
Two black screws hold it to the cover and provide a slight adjustment of the tire-to-handwheel distance:
Prior to this adventure, I soaked the shaft in penetrating oil for a week or two, but to no avail.
I didn’t take any before-the-repair photos, but it looked like this afterward, with the new tire installed…
From the top right (looking over the handwheel):
Notice the small rectangular hole just below the larger section of the shaft in the protruding part of the pot metal housing. That’s supposed to be an oil hole, but it’s also a fine water inlet.
From the top left:
The two obvious screws remove the obvious parts, but beware the compression spring:
And the torsion spring:
Some experimentation with a strap wrench rotated the wheel on the (still firmly frozen) shaft, which suggested the joint was a press fit without a setscrew, splines, or adhesive.
Grabbing the shaft lightly in a machinist’s vise, resting it atop the bench vise, and giving it a few shots with a drift punch drove it downward through the housing:
More gentle beating produced this heartrending scene:
Water just isn’t any good at all for unlubricated steel in a pot-metal bushing…
Anyhow, the shaft & housing cleaned up well, although they look a tad grody, and everything went back together in the reverse order.
I added a drop of light oil through the lube port, chucked the shaft in the drill press, spun it for a minute at low speed to wear off a slight binding, and it’s all good again.
The Smell of Molten Projects in the Morning 