Posts Tagged Sewing
Seam Ripper Cover
Posted by Ed in Home Ec, Machine Shop, Software on 2019-04-05
The cover for Mary’s favorite seam ripper cracked long ago, has been repaired several times, and now needs a replacement:
The first pass (at the top) matched the interior and exterior shapes, but was entirely too rigid. Unlike the Clover seam ripper, the handle has too much taper for a thick-walled piece of plastic.
The flexy thinwall cover on the ripper comes from a model of the interior shape:
It’s not conspicuously tapered, but OpenSCAD’s perspective view makes the taper hard to see. The wedge on top helps the slicer bridge the opening; it’s not perfect, just close enough to work.
A similar model of the outer surface is one thread width wider on all sides, so subtracting the handle model from the interior produces a single-thread shell with a wedge-shaped interior invisible in this Slic3r preview:
The brim around the bottom improves platform griptivity. The rounded top (because pretty) precludes building it upside-down, but if you could tolerate a square-ish top, that’s the way to go.
Both models consist of hulls around eight strategically placed spheres, with the wedge on the top of the handle due to the intersection of the hull and a suitable cube. This view shows the situation without the hull:
The spheres overlap, with the top set barely distinguishable, to produce the proper taper. I measured the handle and cover’s wall thicknesses, then guesstimated the cover’s interior dimensions from its outer size.
The handle’s spheres have a radius matching its curvature. The cover’s spheres have a radius exactly one thread width larger, so the difference produces the one-thread-wide shell.
Came out pretty nicely, if I do say so myself: the cover seats fully with an easy push-on fit and stays firmly in place. Best of all, should it get lost (despite the retina-burn orange PETG plastic), I can make another with nearly zero effort.
The Basement Laboratory remains winter-cool, so I taped a paper shield over the platform as insulation from the fan cooling the PETG:
The shield goes on after the nozzle finishes the first layer. The masking tape adhesive turned into loathesome goo and required acetone to get it off the platform; fortunately, the borosilicate glass didn’t mind.
The OpenSCAD source code as a GitHub Gist:
Kenmore 158: Goobered Screws
Posted by Ed in Machine Shop on 2019-03-06
One of Mary’s quilting group arrived with a machine in dire need of cleaning and oiling. These screws hold the throat plate in place:
They’re standing in a pair of threaded brass inserts (found in the benchtop litter) to show off their tops.
The left screw came out easily, although a few licks with a fine file eased the slot corners.
The one on the right, however, was firmly jammed in place, with the crappy little Kenmore sewing machine screwdriver causing the goobering. I deployed my Brownell’s Gunsmith Screwdriver Bits, applied slightly less force than would ordinarily call for an overnight penetrating oil session, got the screw out, and cleaned it up:
A dot of oil on the threads should keep it happy for the foreseeable future.
Juki TL-2010Q Needle LEDs: Installed!
Posted by Ed in Electronics Workbench, Machine Shop on 2019-03-05
The combined illumination from the COB LED bar on the rear of the arm and the (renewed) COB LEDs over the needle does a pretty good job of lighting up the work area:
That’s a staged shot with a quilt square from the top of the pile. You’d (well, Mary’d) sew along the lines, not across a finished square.
The remaining deep shadows under the foot require an LED with an imaging lens on a gooseneck; precise piecing requires feeding fabric into the needle with alignment exactly where those shadows fall.
The light levels look harsh and shadowy on the bare base:
The shadow extending leftward from the needle comes from the arm’s shadow of the rear LED bar. The hotspot specular reflections of both LED arrays aren’t quite as glaring in real life, but a matte surface finish would be better.
The needle LEDs sit on the bottom of the heatsink inside the endcap:
The COB LED PCB has a weird pink tint, perhaps due to the silicone filter passing all the yellow and blue light downward, with red light reflected into the PCB.
After one iteration, I settled on a 20 Ω 1 W ballast resistor:
It drops 3.6 V to provide 180 mA of needle LED current and dissipates 640 mW, with the LEDs burning about 1.5 W to raise the heatsink just above room temperature. The extrusion on the rear arm is pleasantly warm and the resistors seem happy enough.
Looks good to us and it’s much much much better than the feeble Juki needle LED.
Juki TL-2010Q Needle LEDs: Simple Cable Clip
Posted by Ed in Electronics Workbench, Machine Shop on 2019-03-04
A straightforward cable clip:
It looks better than the previous hack bent from a snippet of PET clamshell:
Ream out the holes with suitable drills, clean out the slot using Tiny Bandsaw™, and it’s all good.
In retrospect, the slot isn’t worth the effort, because it doesn’t open wide enough to admit the cable and doesn’t provide any clamping force; a simple block with two holes would do as well. If the heatsink didn’t already have a 3 mm screw in play, I’d use an adhesive-backed clip from the early Kenmore LEDs.
The OpenSCAD source code isn’t much to look at:
//-----
// Cable clip
// Reoriented into build position, because we only need one
ClipWall = 3*ThreadWidth;
Clip = [15.0,10.0,CableOD + 2*ClipWall];
module CableClip(CableOD = 2.0) {
ClipSides = 4*3;
ClipRadius = Clip.y/2;
ScrewOD = 3.0;
ClipOC = Clip.x - ClipRadius - CableOD/2 - ClipWall;
translate([0,0,Clip.y/2])
rotate([90,0,90])
translate([0,0,0*Clip.z/2])
difference() {
union() {
rotate(180/ClipSides)
cylinder(d=Clip.y/cos(180/ClipSides),h=Clip.z,$fn=ClipSides,center=true);
translate([ClipRadius,0,0])
cube([Clip.x - ClipRadius,Clip.y,Clip.z],center=true);
}
translate([0,0,-(Clip.z/2 + Protrusion)])
rotate(180/8)
PolyCyl(ScrewOD,Clip.z + 2*Protrusion,8);
rotate([90,0,0])
translate([ClipOC,0,-Clip.y])
rotate(180/8)
PolyCyl(CableOD,2*Clip.y,8);
translate([ClipOC - Clip.x/2,0,0])
cube([Clip.x,2*Clip.y,2*ThreadWidth],center=true);
}
}
Juki TL-2010Q Needle LEDs: Trial Fit
Posted by Ed in Electronics Workbench, Machine Shop on 2019-02-28
Stripping the components from the back of a “5 W” COB LED gets it ready for action:
Jumpering the pads with nickel strips harvested from various NiMH and lithium cells restores the original contact pads to service:
A bit of bandsaw artistry produced a replacement for the OEM LED bracket:
The epxoy bonding the LED to the heatsink happens a few paragraphs ahead in this story, but the view justifies it. The 2 mm hole just to the right of the 3 mm SHCS aligns the heatsink to a pin in the machine’s frame, ensuring it doesn’t twist around under vibration.
The view from below (in a mirror on the machine’s bed) shows the COB LED just barely fits in the opening:
I screwed the bare heatsink into the Juki, applied double-stick tape to the COB LED, aligned LED with opening, and stuck it in place. Back in the shop, I traced around the LED to figure out what part of the heatsink needed removing, introduced it to Mr Disk Sander, and contoured it to match the LED.
Clean everything with denatured alcohol, put the heatsink on a glass plate, and clamp it to the height gauge:
Butter up the LED PCB with JB Kwik epoxy, having previously masked the contact pads (with masking tape!) to prevent oopsies:
Raise the height gauge, align LED & heatsink, lower height gauge to squish epoxy into an even layer, raise slightly to ensure the aluminum heatsink doesn’t short the nickel strips, and fast forward a few hours:
Peel off the masking tape and solder a cable in place:
The transparent doodad around the cable is a PET clamp snipped from a consumer electronics clamshell package, then punched and folded to suit. It didn’t work particularly well, so more rummaging will be required.
Foreshadowing: all this went swimmingly and looks pretty good (in a techie sort of way), but I’ve been running a nasty cold (stipulated: there being no pleasant colds). Building While Stupid is never a good idea, as the part of your brain in charge of telling you you’re about to do something catastrophically wrong is the first thing to go.
More to come …
Juki TL-2010Q LED
Posted by Ed in Electronics Workbench on 2019-02-24
For the record, Juki thinks this SMD LED provides enough light around the needle of Mary’s TL-2010Q sewing machine:
A detailed look at the active ingredient:
The 30 Ω resistor drops exactly 2.0 V, so the white LED runs at 67 mA.
We think it’s a glowworm, compared to the COB LED bar across the back of the arm:
I can do better than that, although not with juice from their 5 V power supply.
Sewing Machine Light Bar Current
Posted by Ed in Electronics Workbench on 2019-02-21
After more use and brightness tweaking, the COB light bars on the Juki TL-2010Q and Kenmore 158 now have 2.2 Ω ballast resistors setting the LED current to 370 mA and 300 mA, respectively:
Changing from 2.0 Ω to 2.2 Ω produces a noticeable decrease in light, so 10% steps around 2 Ω seem to be about the right increment. The COB LED strips claim 6 W at 12 V = 500 mA nominal, so they’re running well under the spec.
Given that cheap 1% metal film resistor assortments use E6 or E12 value steps, at best, we may need two resistors in parallel for the next adjustments.
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