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Posts Tagged M2

Kenmore Progressive Vacuum Tool Adapters: Third Failure

The adapter for an old Electrolux crevice tool (not the dust brush) snapped at the usual stress concentration after about three years:

Crevice tool adapter - broken vs PVC pipe

Crevice tool adapter – broken vs PVC pipe

The lower adapter is the new version, made from a length of 1 inch PVC pipe (that’s the ID, kinda-sorta) epoxied into a revised Kenmore adapter fitting.

The original OpenSCAD model provided the taper dimensions:

Electrolux Crevice Tool Adapter - PVC taper doodles

Electrolux Crevice Tool Adapter – PVC taper doodles

The taper isn’t quite as critical as it seems, because the crevice tool is an ancient molded plastic part, but a smidge over half a degree seemed like a good target.

Start by boring out the pipe ID until it’s Big Enough (or, equally, the walls aren’t Scary Thin) at 28 mm:

Crevice tool adapter - boring PVC

Crevice tool adapter – boring PVC

Alas, the mini-lathe’s craptastic compound has 2° graduations:

Minilathe compound angle scale

Minilathe compound angle scale

So I set the angle using a somewhat less craptastic protractor and angle gauge:

Crevice tool adapter - compound angle

Crevice tool adapter – compound angle

The little wedge of daylight near the gauge pivot is the difference between the normal perpendicular-to-the-spindle axis setting and half-a-degree-ish.

Turning PVC produces remarkably tenacious swarf:

Crevice tool adapter - PVC swarf

Crevice tool adapter – PVC swarf

The gash along the top comes from a utility knife; just pulling the swarf off didn’t work well at all.

The column of figures down the right side of the doodles shows successive approximations to the target angle, mostly achieved by percussive adjustment, eventually converging to about the right taper with the proper dimensions.

Cutting off the finished product with the (newly angled) cutoff bit:

Crevice tool adapter - cutoff

Crevice tool adapter – cutoff

And then It Just Worked™.

The OpenSCAD source code for all the adapters as a GitHub Gist:

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MPCNC: Drag Knife Holder

My attempt to use a HP 7475A plotter as a vinyl cutter failed due to its 19 g pen load limit:

HP 7475A knife stabilizer - big nut weight

HP 7475A knife stabilizer – big nut weight

The MPCNC, however, can apply plenty of downforce, so I tinkered up a quick-and-dirty adapter to put the drag knife “pen” body into the MPCNC’s standard DW660 router holder:

MPCNC - DW660 adapter drag knife holder - fixed position

MPCNC – DW660 adapter drag knife holder – fixed position

That’s using the DW660 adapter upside-down to get the business end of the knife closer to the platform. The solid model descends from the linear-bearing Sakura pen holder by ruthless pruning.

It didn’t work well at all, because you really need a spring for some vertical compliance and control over the downforce pressure.

Back to the Comfy Chair:

Drag Knife Holder - DW660 Mount - solid model

Drag Knife Holder – DW660 Mount – solid model

A trio of the lightest springs from a 200 piece assortment (in the front left compartment) pushes the upper plate downward against the drag knife’s flange:

MPCNC - DW660 adapter drag knife holder - spring loaded

MPCNC – DW660 adapter drag knife holder – spring loaded

There’s a bit more going on than may be obvious at first glance.

The screws slide in brass tubing press-fit into the upper plate, because otherwise their threads hang up on the usual 3D printed layers inside the (drilled-out) holes. Smaller free-floating brass tubing snippets inside the springs keep them away from the screw threads; the gap between the top of the tubing and the screw head limits the vertical compliance to 3 mm. The screws thread into brass inserts epoxied into the bottom disk, with a dab of low-strength Loctite for stay-put adjustment.

I bored the orange PETG disk to a nice slip fit around the knife body:

DW660 drag knife holder - boring body

DW660 drag knife holder – boring body

The upper plate also required fitting:

DW660 drag knife holder - boring plate

DW660 drag knife holder – boring plate

A few iterations produced reasonably smooth motion over a few millimeters, but it’s definitely not a low-friction / low-stiction drag knife holder. It ought to be good for some proof-of-concept vinyl cutting, though.

The OpenSCAD source code as a GitHub Gist:

 

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Fireball Island Figures

A cousin asked if my 3D printer could replace some figures gone missing from their old Fireball Island game board, a classic apparently coming out in a new & improved version.

Fortunately, solid models exist on Thingiverse:

Fireball Island figure - Thingiverse 536867

Fireball Island figure – Thingiverse 536867

Unfortunately, the left arm requires support, which Slic3r supplies with great exuberance:

Fireball Island figure - Slic3r support

Fireball Island figure – Slic3r support

The vast tower on the figure’s right side (our left) seemed completely unnecessary, not to mention I have no enthusiasm for the peril inherent in chopping away so much plastic, so I replaced it with a simple in-model pillar:

Figure Support Mods

Figure Support Mods

The pillar leans from an adhesion-enhancing lily pad and ends one layer below the left hand, with all dimensions and angles chosen on the fly to make the answer come out right.

Works like a champ:

Fireball Island Figures - orange - on platform

Fireball Island Figures – orange – on platform

The dark band down the middle comes from the Pixel’s shutter.

They emerged with some PETG hair, the removal of which I left as an end-user experience.

I mailed a small box containing figures printed in my (limited!) palette of four colors, some spares Just In Case™, and a few QC rejects showing the necessity of lily pads.

Game on!

The OpenSCAD source code as a GitHub Gist:

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Tour Easy Daytime Running Light: First Fracture

A wind gust pushed Mary’s bike over with the daytime running light on the downward side:

Fairing Flashlight Mount - Fracture

Fairing Flashlight Mount – Fracture

Frankly, it’s better to have a cheap and easily replaceable plastic widget break, instead of something expensive and hard to find.

Because we live in the future, a replacement part was just a few hours away:

M2 - Nozzle Z Offset Recal - DRL Clamp

M2 – Nozzle Z Offset Recal – DRL Clamp

Well, a few hours after installing a replacement thermistor and recalibrating the M2, but nested repairs happen every now and again.

To the road!

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Makergear M2: Nozzle Z Offset Recalibration

After a few days of downtime, an Official Makergear Thermistor arrived and is now installed amid a dab of heatsink compound:

M2 - Thermistor with heatsink compound

M2 – Thermistor with heatsink compound

With the hot end set a bit higher than usual, position the platform at Z=0, lower the nozzle to be flat on the platform, tighten the lock screw, then run off a set of large calibration squares:

M2 - Nozzle Z Offset Recal - first test

M2 – Nozzle Z Offset Recal – first test

The scrambled square in the front left says the Z=0 nozzle position came out just a bit too far above the platform and, indeed, the measurements (upper left numbers) say it’s off by 0.15-ish mm:

M2 Nozzle and Platform Re-Cal Measurements

M2 Nozzle and Platform Re-Cal Measurements

Probably a little PETG stuck to the nozzle; I hate adjusting things when they’re burning hot.

The walls are also thin by a smidge, but the first order of business is to reset the Z offset with M206 Z=-2.15. With that in hand, the second set of squares came out at 3.00 to 3.08 mm (lower left numbers), which I defined to be Close Enough.

The 0.08 mm variation across the platform isn’t enough to worry about.

The first skirt threads were too thick and not solidly bonded together, but the second skirt came out normally, with a thickness from 0.21 through 0.30, which is also Good Enough.

The three-thread walls were still 1.15 mm, rather than 1.20 mm, so the EM should go from 0.95 to 0.95*1.20/1.15 = 1.05.

Next, a set of single-thread thinwall boxes to verify the Z offset and recheck the Extrusion Multiplier:

M2 - Nozzle Z Offset Recal - thinwall test

M2 – Nozzle Z Offset Recal – thinwall test

They’re dead on 3.00 mm tall, varying by not enough to worry about.

Their single-thread walls are 0.38 mm, not the intended 0.40, which suggests the EM should become 0.95*0.40/0.35 = 1.00.

It turns out the filament diameter at this part of the roll is scant of 1.75 mm, maybe 1.73 mm, so I decided to not fiddle with the EM.

The first production part came out fine:

M2 - Nozzle Z Offset Recal - DRL Clamp

M2 – Nozzle Z Offset Recal – DRL Clamp

The flange around the bottom of the arch support grid (in the middle) is intentional; it’s not an overstuffed first layer. The clamp sections rise from the platform just like they grew there.

So the M2 is back in operation and I have a spare thermistor on the shelf!

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M2 DIY Thermistor Rebuild: Autopsy

Not much to my surprise, my hack-job thermistor rebuild went bad:

M2 - thermistor - assembly 2

M2 – thermistor – assembly 2

Having nothing to lose, I heated the brass tube over a butane flame to wreck the epoxy, which blew out with a satisfactory bang and filled the Basement Laboratory with The Big Stink.

Much to my surprise, the active ingredient still worked:

M2 DIY thermistor corpse

M2 DIY thermistor corpse

The multimeter reported absolutely no intermittent dropouts for as long as I was willing to watch the trace while doing other things:

DIY Thermistor Autopsy - Resistance Trend

DIY Thermistor Autopsy – Resistance Trend

So it must be my crappy soldering technique.

A brace of real M2 thermistors will arrive shortly …

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Rubber Soaker Hose Repair

A soaker hose leaped under a descending garden fork and accumulated a nasty gash:

Soaker Hose Splice - gashed

Soaker Hose Splice – gashed

Mary deployed a spare and continued the mission, while I pondered how to fix such an odd shape.

For lack of anything smarter, I decided to put a form-fitting clamp around the hose, with silicone caulk buttered around the gash to (ideally) slow down any leakage:

Soaker Hose Splice - Solid Model - Assembled

Soaker Hose Splice – Solid Model – Assembled

As usual, some doodling got the solid model started:

Soaker Hose Splice - Dimension doodle 1

Soaker Hose Splice – Dimension doodle 1

A hose formed from chopped rubber doesn’t really have consistent dimensions, so I set up the model to spit out small test pieces:

Soaker Hose Splice - Test Fit - Slic3r

Soaker Hose Splice – Test Fit – Slic3r

Lots and lots of test pieces:

Soaker Hose Splice - test pieces

Soaker Hose Splice – test pieces

Each iteration produced a better fit, although the dimensions never really converged:

Soaker Hose Splice - Dimension doodle 2

Soaker Hose Splice – Dimension doodle 2

The overall model looks about like you’d expect:

Soaker Hose Splice - Complete - Slic3r

Soaker Hose Splice – Complete – Slic3r

The clamp must hold its shape around a hose carrying 100 psi (for real!) water, so I put 100 mil aluminum backing plates on either side. Were you doing this for real, you’d shape the plates with a CNC mill, but I just bandsawed them to about the right size and transfer-punched the hole positions:

Soaker Hose Splice - plate transfer punch

Soaker Hose Splice – plate transfer punch

Some drill press action with a slightly oversize drill compensated for any misalignment and Mr Disk Sander rounded the corners to match the plastic block:

Soaker Hose Splice - plate corner rounding

Soaker Hose Splice – plate corner rounding

A handful of stainless steel 8-32 screws holds the whole mess together:

Soaker Hose Splice - installed

Soaker Hose Splice – installed

These hoses spend their lives at rest under a layer of mulch, so I’m ignoring the entire problem of stress relief at those sharp block edges. We’ll see how this plays out in real life, probably next year.

I haven’t tested it under pressure, but it sure looks capable!

The OpenSCAD source code as a GitHub Gist:

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