Posts Tagged Repairs

3D Printing: Native G-Code?

From a discussion on the Makergear 3D printer forums

From a new M2 user disillusioned by the learning curve:

Is there a 3D CAD software out there that natively creates .g or .gcode files It’s not just a 3D printing thing.

CAD (computer-aided design) software produces a solid model, which a CAM (computer-aided manufacturing) program then converts into the specific dialect(s) of G-Code required by whatever machine tool(s) will create the widget. You can create the solid model using many different CAD programs and convert it into G-Code with many different CAM programs, each with its own collection of features and warts.

3D printing calls the CAM program a “slicer”, but it’s a different name for the process of converting geometry into machine instructions.

Even in subtractive manufacturing using lathes and mills, you absolutely must understand how the G-Code interacts with the production hardware.

I unfortunately don’t want to learn all the nuances and parameters of the slic3r software

Then you must use a service like Shapeways: you create the model, send it to them, and get a neat widget a few days later. Their laser-sintered powder process provides much better built-in support than you’ll ever get from consumer-grade fused-filament printers, you can select from a wide variety of materials (including metals!), and, as long as you follow their straightforward design guidelines, you’ll never know how the magic happens.

If you intend to create more than a trivial number of widgets, though, the cost in both cycle time and money will begin gnawing at you. In round numbers, I’ve been designing and printing one widget a week for the last seven years, so adding a printer to my basement shop and learning how to use it has been a major win.




Heatsink Fuzz

This appeared while harvesting heatsinks and suchlike from a defunct Dell Optiplex:

Clogged CPU heatsink
Clogged CPU heatsink

The only way to get access to that end of the heatsink is to break the heatsink’s thermal bond to the CPU, which seems like a Bad Idea if you intend to continue using the thing:

Clogged CPU heatsink - fan
Clogged CPU heatsink – fan

I buy off-lease Optiplexes from Dell Financial Services (a.k.a. Dell Refurbished) and, although their interiors always look well-cleaned, Dell (or, nowadays, FedEx Reverse Logistics) may have decided against breaking the CPU’s thermal bond and just sent me an office’s dust collection.

Doesn’t look like my dust. That’s my story and I’m sticking with it.


3D Printing: Slow Hot End Temperature Oscillations

From a discussion on the Makergear 3D printer forums

A Makergear M2 user encountered a temperature control problem:

Problem: Temperature fluctuation on the hotend +/- 7 degrees C when set in the controls. A little more extreme when printing (~+/- 15).

Slow cycling like that indicates the hot end’s PID loop coefficients don’t match reality.

Preheat the extruder to maybe 200 °C, run a PID calibration (M303), store the results in EEPROM (M500), and that should do the trick.

PID coefficients depend on the hot end’s physical condition, so you should re-do the calibration whenever anything changes on the hot end. Even removing & reinstalling the same hardware will change the contact points between, say, the thermistor and its hole in the hot end.

A dab of good heatsink compound on the thermistor should stabilize its contact with the hot end, although that will change the reported temperature and PID coefficients. Probably doesn’t make any real difference, but I felt better:

M2 - Thermistor with heatsink compound
M2 – Thermistor with heatsink compound

Which prompted a question from a user who regularly swaps entire hot ends to change nozzle diameters:

run a pid cal when I set my starting height each time I switch?

Assuming you swap entire hot ends, including their thermistor & heater, then you can calibrate each one, write down its PID values, manually set ’em with M301 when you install it, then use M500 to store ’em in EEPROM.

Because you bend those fragile thermistor wires every time you swap hot ends, keep a couple thermistors on hand. You’ll need ’em.


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3D Printing: Peculiar Octopi Problem

From a discussion on the Makergear 3D printer forums

A Makergear M2 user had a strange problem:

Octopi claims the serial connection went down.

LED2 was blinking red, rapidly, and LED3 was shining with a steadfast red light.

LED2 shows the extruder heater PID loop is running and LED3 shows the extruder fan is on:

You just never noticed the blinkiness before … [grin]

Because the extruder heater is still running, the firmware hasn’t detected a (possibly bogus) thermal runaway or any other fatal problem. It’s just waiting for the next line of G-Code, but Octopi isn’t sending it.

Casually searching the GitHub issues, there’s a report of intermittent serial problems from last year:

Which points to the FAQ: … eption/228

Look at the Octopi Terminal log to see if the conversation just before the failure matches those descriptions.

Assuming you haven’t updated the printer firmware or anything on the Octopi, then something physical has gone wrong.

First and least obviously, the Pi’s MicroSD card has probably started to fail: they’re not particularly durable when used as a mass storage device and “the last couple of years” is more than you should expect. Download a fresh Octopi image, put it on a shiny-new, good-quality card (*), and see if the situation improves.

Then I’d suspect the Pi’s power supply, even though you’re using the “official rpi power supply”. All of those things contain the cheapest possible electrolytic capacitors, running right on the edge of madness, and produce bizarre errors when they begin to go bad. Get a good-quality wall wart (**), ideally with a UL rating, and see if the situation improves.

While you’re buying stuff, get a good-quality USB cable (***) to replace the one that (assuming you’re like me) you’ve been saving for the last decade Just In Case™. Use the shortest cable possible, because longer does not equal better.

After that, the problems get truly weird. Apply some tweakage and report back.

(*) This is harder to do than you might think. You may safely assume all cards available on eBay and all “Sold by X, Fulfilled by Amazon” cards will be counterfeit crap. I’ve been using Samsung EVO / EVO+ cards (direct from Samsung) with reasonable success: … sk-memory/ … ification/ … 22y+zq29p/

The card in question eventually failed, so having a backup card ready to go was a Good Idea™.

(**) Top-dollar may not bring top quality, but Canakit has a good rep and costs ten bucks through Prime.

(***) Amazon Basics cables seems well-regarded and work well for what I’ve needed.

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Kenmore 158: Goobered Screws

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:

Kenmore screws - goobered
Kenmore screws – goobered

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:

Kenmore screws - smoothed
Kenmore screws – smoothed

A dot of oil on the threads should keep it happy for the foreseeable future.



COB LED Autopsy

The intent was to wire the “5 W” COB LED to the 12 VDC supply grafted on the Juki TL-2010Q, through a suitable resistor around 18 Ω. Unfortunately, the next morning I managed to run 12 V directly to the LEDs, which produced an astonishingly bright flash of blue-white light and an opportunity for some post-mortem analysis.

A sharp tap with a chisel popped the COB LED PCB off its heatsink:

Destroyed COB LED - epoxy bond
Destroyed COB LED – epoxy bond

That’s a pretty nice thermal joint and ought to transfer as much heat as reaches the back surface. Mechanically, it yanked one of the nickel tabs right off the solder pads; obviously, I must now level up my soldering game.

Scraping the yellow silicone filter off the PCB reveals the minuscule LEDs:

Destroyed COB LED - excavated yellow silicone
Destroyed COB LED – excavated yellow silicone

You’ll recall they’re arranged in three series sets of six:

Circular 12V COB 18 LED panel - copper layout
Circular 12V COB 18 LED panel – copper layout

Some probing revealed five of six LEDs in one set was still functional:

Although a few other LEDs across the PCB survived, that’s not the way to bet when you run so much current through the poor things.

Ah, well, that’s why I always buy a few more parts than I really need …


Tour Easy: SRAM X.0 Rear Grip Shifter

With more snow on the schedule, Mary’s bike finally got a new rear shifter:

Tour Easy - SRAM X.0 grip shifter installed
Tour Easy – SRAM X.0 grip shifter installed

It’s an old-school SRAM X.0 grip shifter, evidently compatible with SRAM X.9 and X.7 derailleurs, and seems to work OK. The wavy ridges may be more prominent than necessary for our road riding, though.

In a miracle of rare device, the preinstalled cable turned out to be exactly long enough:

Tour Easy - SRAM X.0 cable length
Tour Easy – SRAM X.0 cable length

Twiddling the length for perfect shifting requires on-the-road testing and the chain wrap may need tweaking (I may not have gotten it right when I installed the derailleur), but at least the shifter stops at every detent along the way.

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