Posts Tagged Repairs

M2 Platform Leveling

This doesn’t happen very often, but, after a few road trips and some jostling around, the M2’s platform was definitely out of alignment: the first layer came out generally too thin, with the X-Y+ quadrant very much too thin.

I tried a quick and dirty adjustment that didn’t produce meaningful results, then broke out the Starrett Taper Gauge and did it right.

The relocated platform height switch is about 4.5 mm higher than the nozzle, so:

  • Jog the nozzle off the platform to the right
  • Home the Z axis
  • Define that position as Z=-6: G92 Z-6
  • Move to Z=0: G0 Z0
  • Jog around measuring the height of the nozzle above the platform
  • Adjust screws to reduce variation
  • Change Z offset in startup G-Code
  • Run off a few test patterns to get the platform heated
  • Measure actual thickness
  • Change Z offset to get the right answer
  • Done!

This progression of cold measurements, read top-to-bottom, left column first, shows the observed nozzle height above the platform around the edges and at the center:

M2 Platform Leveling Progression - 2014-06-30

M2 Platform Leveling Progression – 2014-06-30

The final measurements seem to indicate the glass plate is 0.2 mm convex in the center, but I wouldn’t trust the measurements to that level of accuracy. It’s probably bowed upward, but it’s certainly close enough.

The cold measurements suggest that the Z offset should be -4.80 mm, but the measurements on the hot platform with actual extrusion threads showed that -4.50 mm produced the correct thicknesses.

It’s not clear automating the movements would produce better or faster results than just manually jogging the nozzle around the platform, particularly since it happens only every few months.

This would be easier with the Z offset stored in the EEPROM and some modified startup G-Code to retrieve it.

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You Know It’s Time to Change the Bike Tire When …

…. the armor layer under the tread starts peeking through:

Eroded Schwalbe Marathon tire

Eroded Schwalbe Marathon tire

Actually, it started peeking through early this year, but why rush things?

I swapped in a Michelin Pilot City 700x32C tire with their Protek Max armor and reflective sidewalls; we’ll see how well all that works.

No tire liner inside, so I’m depending on the armor and the fact that it’s a rather chunky tire.


Tweaked Crossword Scanning

In what’s surely a change intended to better meet the needs of their customers, the newspaper changed the crossword layout just a little teeny bit, so my previous script needed a tweak:

echo Scanning...
scanimage --mode Gray --opt_emulategray=yes --resolution 300 -l 5 -t 0 -x 105 -y 195 --format=pnm > /tmp/scan.pnm
echo Converting...
convert /tmp/scan.pnm -level 45%,60% -resize 2400x3150 +repage -unsharp 0 /tmp/trim.png
convert -density 300 -size 2550x3300 canvas:white /tmp/trim.png -gravity center -composite /tmp/page.pdf
echo Printing...
lp -n 2 /tmp/page.pdf
echo Done!

It now spits out two large-print copies, to better meet their actual needs, at least for two of their customers.



Kenmore 158: Foot Pedal Foot Bushings

As you’d expect, the soft feet on the bottom of the Kenmore Model 158 sewing machine’s foot pedal control turn into hard buttons after a few decades. The OEM feet have mushroom tops that push through holes in the case and latch in place; of course, none of the rubber feet in my collection match the hole diameter or case thickness.

No problem! Design a bushing that fits the case hole and passes a 4-40 screw:

Speed Control Foot Bushing

Speed Control Foot Bushing

Then print up a handful, add screws to fit the rubber feet, and top off with nuts:

Kenmore 158 - pedal foot bushing - detail

Kenmore 158 – pedal foot bushing – detail

Installed, with the screws cropped to a suitable length, they look about like you’d expect:

Kenmore 158 - pedal foot bushing - interior

Kenmore 158 – pedal foot bushing – interior

Turns out that the springs supporting the foot pedal rest in those pockets, so the bushing reduces the spring travel by a few millimeters. The springs aren’t completely compressed with the pedal fully depressed, so it’s all good.

The OpenSCAD source code:

// Kenmore Model 158 Sewing Machine Foot Control Bushings
// Ed Nisley - KE4ZNU - June 2014

//- Extrusion parameters must match reality!
//  Print with 2 shells and 3 solid layers

ThreadThick = 0.20;
ThreadWidth = 0.40;

HoleWindage = 0.2;			// extra clearance

Protrusion = 0.1;			// make holes end cleanly

function IntegerMultiple(Size,Unit) = Unit * ceil(Size / Unit);

// Dimensions

Stem = [2.5,5.7];			// through the case hole
Cap = [3.0,10.0];			// inside the case

LEN = 0;
DIA = 1;

OAL = Stem[LEN] + Cap[LEN];

ScrewDia = 2.8;				// 4-40 generous clearance

// Useful routines

module PolyCyl(Dia,Height,ForceSides=0) {			// based on nophead's polyholes

  Sides = (ForceSides != 0) ? ForceSides : (ceil(Dia) + 2);

  FixDia = Dia / cos(180/Sides);

  cylinder(r=(FixDia + HoleWindage)/2,

module ShowPegGrid(Space = 10.0,Size = 1.0) {

  RangeX = floor(100 / Space);
  RangeY = floor(125 / Space);

	for (x=[-RangeX:RangeX])
	  for (y=[-RangeY:RangeY])


// Build it!


difference() {
	union() {
		PolyCyl(ScrewDia,OAL + 2*Protrusion,6);


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Samsung Vacuum Cleaner Floor Brush: Wheel Retainers

We still haven’t exhausted the never-sufficiently-to-be-damned Samsung Quiet Jet vacuum’s bag supply, so when a wheel fell off the floor brush again, I had to come up with a better fix than a twist of wire. Obviously, those delicate little retaining latches need more persuasion.

Capture the wheel in the Sherline’s 4-jaw chuck on the rotary table and drill four holes just below the end of the latches:

Samsung wheel - drilling

Samsung wheel – drilling

The wheel is 20 mm thick. The holes lie 9 mm back from the open end of the wheel or 11 mm from the closed end at the chuck face. Drill maybe 6 mm down; I did it by eye, jogging slowly downward until the tip of the drill touched the latch.

Tap the holes and install four 8-32 setscrews:

Samsung wheel - setscrews installed

Samsung wheel – setscrews installed

I don’t have a bottoming tap, but an ordinary plug tap was Good Enough; the incomplete threads should hold the setscrews in place.

Reinstall the wheel, tighten the setscrews, and wrap festive silicone tape around the whole affair:

Samsung floor brush - wheel installed

Samsung floor brush – wheel installed

I heroically resisted the temptation to pry the other wheel off for a preemptive repair …




Power Screen Trommel

This monster appeared near Mary’s Vassar Farms plot:

Power Screen Trommel - right

Power Screen Trommel – right

I had to look up trommel, too.

Apparently suffering a breakdown, it spent the next two weeks idle with all its covers open. The can of WD-40 makes a nice touch, but the condition of the central lubrication panel suggested the last grease went through those Zerk fittings quite a while ago:

Power Screen Trommel - lube panel

Power Screen Trommel – lube panel

The manufacturer’s information label, tucked in a protected position, remains pristine:

Power Screen Trommel - mfg plate

Power Screen Trommel – mfg plate

Scrawled notes near the control panel noted that someone installed new oil and fuel filters in late 2004, with 4103 hours on the running time meter:

Power Screen Trommel - controls

Power Screen Trommel – controls

Then, one day, it vanished, perhaps back into the mysterious universe from whence it came …


Stirrup Hoe: New-to-It Handle

Mary (not the spammer) uses a stirrup hoe for most of what little weeding she does, so it spends much of its life outdoors in the Vassar Farms plot. The bottom of the handle disintegrated and she brought the business end home for repair:

Stirrup hoe - replacement handle

Stirrup hoe – replacement handle

That was easy: a suitable handle lay on the top of the rods-and-tubes rack; I’d harvested it from a defunct rake a while back. Although the wood is weathered, we think of it as well-seasoned. The errant hole marks came from a first pass, before I realized there was no point in having the handle extend beyond the outward-bending part of the brackets.

The bolts and locking nuts are original!

Ya gotta have stuff…

(And not a trace of 3D printing anywhere to be seen. Imagine that!)