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.

Category: Machine Shop

Mechanical widgetry

  • IRQ Troubles on Razor

    The Dell Dimension 4560, a.k.a. razor, that controls my Sherline CNC mill woke up without network support. That’s a showstopper, because all the G-Code files live on the server across the basement.

    All my boxes have a network function dipstick test: the desktop background is an image on that same file server. When the NFS share wakes up dead, then the screen shows the default Ubuntu background: brown = down! (At least in Ubuntu 8.04 LTS, which is what EMC2 is built on right now.)

    Checklist…

    • NFS share isn’t mounted
    • … and can’t be mounted
    • ifconfig shows eth0 up & active
    • can’t ping the server
    • can’t ping razor from the server
    • Link lights on network switch nailed to floor joist overhead are green
    • Link light on NIC on back panel
    • Activity lights on switch & NIC blink occasionally (??)
    • Swapping ports on the switch = no change
    • Laptop works fine plugged into switch = switch OK

    So whatever is busted, is busted in the 4560. Drat!

    (Should have checked cable between switch and NIC. Sometimes you get a data failure without affecting the link & activity lights. Weird, but stuff happens.)

    Looking in dmesg shows that a bogus IRQ 11 occurred during startup:

    [   44.439932] irq 11: nobody cared (try booting with the  irqpoll" option)
... time passes ...
... bad IRQ log dump gibberish ...
[   44.440440] Disabling IRQ #11

    Fairly obviously, after that point nothing about the NIC or anything else on IRQ 11 will work: the hardware setup may be OK, you can write to it and read from it, but no actual data gets through.

    A reboot didn’t cure the problem. Reboots in Linux rarely solve a problem; you’ve got to actually find the root cause and fix it, rather than shake the dice to see if a better combination comes up.

    Anyhow.

    Restarted to get into Dell’s attenuated BIOS configuration routine, changed the NIC to IRQ 3 (just because it was first on the list), saved, restarted, and everything works. The bogus interrupt is gone, the NIC is running, NFS shares are OK.

    It absolutely beats me. But at least this is written down so the next time it happens, I’ll remember what I did.

    Oh, yeah. The Sherline CNC mill uses stepping motors and uses cutters, so it’s a Steppin’ Razor, of course, and is therefore named razor. I suppose I could have called it molly, but that’d be a stretch.

  • Cutting Thin Rings: Homebrew Punches

    The Totally Featureless Clock is back for a refit: its preferred location turned out to have essentially no RF at all, so I must move the antenna out of the clock case on the end of a cable.

    Drat!

    I put the ferrite bar inside a length of PVC pipe, turned down to make it less ugly, with white plastic end plugs. Rather than fiddle around with complex mountings, I cushioned the fragile bar in closed-cell foam, which meant I needed some way to cut a bunch of foam rings.

    Some rummaging produced a thinwall brass tube with about the same ID as the PVC pipe. A brief trip to the lathe put a reasonably sharp edge on one end.

    Sharpening the brass tube
    Sharpening the brass tube

    That edge is more keen than it looks; while it’s not razor-sharp, it’s plenty good enough. I didn’t use it as a punch, just grabbed it in a rag to cushion my palm and rotated it through the foam against a plywood scrap.

    That produced a bunch of foam cookies.

    Foam cutouts
    Foam cutouts

    The bar diameter was close enough to a standard hole punch that I didn’t have to make one. Centering by eye and rotating by hand turned the cookies into donuts.

    Punched holes
    Punched holes

    And then they fit just fine…

    Cushioned ferrite bar antenna
    Cushioned ferrite bar antenna

    I made more donuts to swaddle the bar from end to end inside the PVC tube. I slipped the antenna in from the left, then pushed the donuts over the bar with Yet Another Brass Tube. The end result is an antenna compression-packed in foam, which ought to keep it in good condition through at least a minor oops.

    Finished antenna housing
    Finished antenna housing

    The screws pass through the end plugs to hold them against the pressure from the foam cookies at the bar ends. The holes are slightly counterbored on the top to blend the screw heads into the curve of the tube. There’s a 3/8-inch flat along the bottom that will eventually settle against the underside of a shelf.

  • Useful, Albeit Incorrect, Sherline Wrench Sizes

    My Sherline mill has inch sized fittings, but a couple of metric wrenches from the junk box reduced the workbench clutter …

    Double open 10 + 11 mm:

    • 10 mm = 10-32 nuts for step clamps (really 3/8 inch)
    • 11 mm = small drawbar bolt (really 7/16 inch)

    Combination 13 mm:

    • 13 mm = large drawbar bolt (really 1/2 inch)

    Now, I know full well that applying metric wrenches to inch fittings is a terrible idea, but y’know what? At the torque levels appropriate to Sherline fittings, they work just fine.

    One of these days, I’ll be at a garage sale offering some double wrenches in the correct inch sizes …

  • Epson R380 Printer: External Waste Ink Tank

    Side cover latch and external tank hose
    Side cover latch and external tank hose

    Having reset the waste ink counter on my Epson R380 printer, I finally got around to installing the external waste ink tank that will prevent the printer from drooling all over its innards.

    Fortunately, rerouting the waste ink hose out of the printer doesn’t require the complete teardown mandated to remove the waste ink tank itself: you can do it by removing the cover, drilling a hole, moving the hose, and abandoning the tank in place.

    The recommended way to remove the right-side side cover (as you face the printer) involves jamming a steel ruler into the “vent” (it’s actually a decorative feature) and shoving a latch out of the way. I trimmed a bit of stainless steel strip, shoved it in, and it worked fine. The cover latch is the complex central feature in the vertical gap between the case and the cover. The hose is routed out through a new hole down in the lower right corner.

    With the cover off, it turns out that the “tank” is actually a “tray” (which is what it’s called in the maintenance manual) filled with absorbent fuzz. There’s no lid, so it appears they’re counting on evaporation to keep the total volume under control and surface tension on the fuzz to keep the ink from leaking when you tip the printer. I suspect if the printer spent a lot of time on its ear, though, things would get messy.

    Internal tank and OEM hose
    Internal tank and OEM hose

    Removing the hose from the barbed fitting goes easier with a small screwdriver pushing it along; you (well, I) can’t just pull the hose off. It’s a very flexible silicone rubber (?) hose with an internal liner: very nice stuff.

    The hose seems to drain only the head-cleaning station, not the long waste ink tank / tray across the width of the printer that catches overspray from borderless printing. That counter is at 5% of its rated maximum, so I’ll let it slide.

    The ink, being adsorbed in the fuzz, won’t leak back out of the tray, so there’s no need to plug the barbed fitting.

    Hole in case and rerouted hose
    Hole in case and rerouted hose

    I used the 1/4-inch tip of a fat step drill to poke a hole at the very bottom of the plastic case, behind the pillar holding the white printer mechanism. The far end of the hose connects to a pump somewhere back in the bowels of the printer and that hole position freed up the longest amount of hose.

    Much to my surprise, the tube wasn’t full of ink and didn’t bloosh blackness all over everything. Perhaps the hose drains back to the pump between head cleanings?

    Then it’s just a matter of buttoning up the case, joining the hoses with the supplied barbed fitting, sticking the external tank’s hook-and-loop strip to the printer, and trimming the hose to fit. It Would Be Nice If the new tank hose were the same flexy silicone stuff as the OEM hose, but it looks to be ordinary Tygon-ish tubing and is a bit stiffer than I’d like.

    External waste ink tank in place
    External waste ink tank in place

    No ink has reached the new hose yet, but I’m sure the next few head cleaning cycles will push out some oodge.

    The tank vendor suggests “recycling” the waste ink by diluting it with black ink, but I’ll just discard it. Bulk ink isn’t all that expensive, compared to OEM ink cartridges, and I’d rather not borrow trouble.

  • Cleaning Up a Pipe Center

    I need this pipe center maybe twice a year and have hitherto managed to work around some nasty gouges and runout that came with it. But I finally cleaned it up by the simple expedient of dialing the compound to match the average angle (it was badly out of true) and skimming off enough to clear the surface.

    The trick was realizing that the teeny little shoulder between the taper and the cone was concentric with both. I grabbed it tight (yeah, in a three-jaw chuck), took sissy cuts, and hit the end result with a file to smooth things out.

    The remaining gouges are just fine by me.

    Cleaned-up Pipe Center
    Cleaned-up Pipe Center

    It had been center-drilled in the small end, but the opening had taken a real beating at some point. Neither the live nor the dead center sat correctly and I couldn’t figure out how to hold the thing to re-drill the end.

  • Shrinking Heat-shrink Tubing to a Specific Diameter

    Shrinking tubing on a mandrel
    Shrinking tubing on a mandrel

    I needed some black plastic tubes with several different IDs, which usually calls for some tedious machining. Then I realized I could just shrink some heat-shrink tubing around mandrels.

    Drill rod worked fine, as did a socket wrench. The only catch was avoiding the engraved lettering, which tends to lock the tubing firmly in place.

    In a pinch, I suppose you could turn a rod to the right OD and make a mandrel. That would likely be faster than machining a tube from solid stock, at least for me.

    Chuck the mandrel in the lathe, lean a box cutter against the tubing, turn it by hand, and cut to the right length with nice flat ends. Pry it off by sliding a fine needle between the tubing and the mandrel.

    You knew that already, right?

  • Constraining a Sewer Snake

    Constrained sewer snake
    Constrained sewer snake

    Had the occasion to run the flexy snake through a kitchen drain that turned out to be not as plugged up as I expected, which is always good news. Replaced the cleanout plug, hosed off the snake, coiled it up, and applied the usual three nylon cable ties to keep the snake together.

    It took me years to figure out that last step. None of the old-school tricks work for me; I can’t tie knots in string / twine / rope while simultaneously holding those coils together and the snake resists any attempt to weave the loose ends into the bundle.

    Mercifully, I don’t use the snake all that often and I don’t feel at all bad about tossing three cable ties each time.

    You figured that out long ago, right?