Reason #1 to Love OpenSCAD’s 2D Subsystem: Fillets

June 12th, 2019 by Keith Neufeld

I just designed and printed a battery holder and I’m shamelessly reusing this image from the blog post about it to illustrate fillets in 3D design:

3D-printed holder for Makeblock mBot robot LiPo battery

You might notice that the holder’s mounting bosses have nice roundy fillets that are standard in professional CAD packages and have been a wee bit difficult to achieve in OpenSCAD until fairly recently. The ability to design them now is one of two observations in the last week that have really driven my interest in OpenScad’s 2D subsystem. If you’re not interested in OpenSCAD, you’ll probably want to stop reading now. (Who am I kidding — I’m sure that the two of you still reading are interested in OpenSCAD.)

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3D-Printed Makeblock mBot LiPo Battery Holder

June 12th, 2019 by Keith Neufeld

I’ve assembled a couple of Makeblock mBot robots I picked up a few years back and intend to start programming soon. They come with a 4xAA battery holder, but I’m not a fan of single-use batteries and Makeblock’s LiPo is only $10 on Amazon [no affiliation and not an affiliate link, just a happy customer], so I ordered a couple.

The LiPo batteries came in clear plastic cases with tabs that looked like they should latch into the slots on the robot chassis, but the spacing was off. The robot kit came with hook-and-loop tape to fasten down the battery holder, but yuck. So I designed this holder, which is good enough to use after a single pass of dimensional refinement.

Makeblock mBot robot with 3D-printed LiPo battery holder

Many thanks to my student employee Kip for printing the battery holder on his Prusa I3 MK2s. The quality is outstanding.

I’ll upload the design to Thingiverse after a bit of code cleanup.

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Chewing ABS to Make New Filament

August 16th, 2018 by Keith Neufeld

Like many other 3D printer owners, I’ve long dreamed of processing post-consumer plastic into new filament for printing. I’ve now taken a couple of steps in that direction.

ABS plastic pelletized with sheet-metal nibbler tool

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Booting the MakerBot CupCake after Five Years Part 3: Heated Build Platform and First Print

July 9th, 2018 by Keith Neufeld

Friday evening I left off with the extruder working again. Saturday I focused on the heated build platform.

I’ve always had astoundingly good luck with kapton tape since nophead’s serendipitous discovery, probably because I (still) prefer to print in ABS. When the build platform is warm, my prints stick to it absolutely with no raft or mouse ears and once it has cooled, they release easily. That’s a pretty compelling combination.

kapton tape for MakerBot CupCake heated build platform

So my first step was replacing the scraped-up kapton that I gouged the last time the printer was on. I bought a 4″ roll way back when and I keep a strip of unsticky tucked under the end so I don’t have to peel it up with fingernails and get fingerprints on the stickum.

In the past I’ve always replaced the tape by sticking down the end and using a credit card to “squeegee” it onto the surface, and it can be tough to avoid getting bubbles. Yesterday I unrolled enough tape to cover the platform and when I had it stretched out, it was easy to align the front edge of the tape with the front edge of the platform, at which point I squeegeed it down with my thumb with no bubbles at all. Huh, well, I guess I’ll remember that.

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Booting the MakerBot CupCake after Five Years Part 2: Installing Software

July 7th, 2018 by Keith Neufeld

The next step in running the CupCake 3D printer is reinstalling the software and connecting to the machine.

ReplicatorG 0026 main screen

It went surprisingly well, with the only real snag being my misremembering the installation process, leaving me stuck in NotConnectedLand for a while.

What Software

A lot has happened in the world of hobbyist 3D printing since the last time I had the CupCake powered up and both new firmware and new driver software are available. I’m interested in upgrading both as I have time; but for a first boot, I want to change as few variables as possible. That means leaving the firmware that’s on the CupCake and matching a legacy version of ReplicatorG to what’s on it. And I had no idea what was on it.

Fortunately I have a blog and on that blog I write some things.

I went to my own blog’s MakerBot CupCake blog category and quickly found the January 2012 post on rebuilding the heater in which I had written:

… I upgraded ReplicatorG from 0024 to 0029r2, and let it upgrade my firmware from v2.4 (I think) to v3.0, and lo! lost communication between ReplicatorG and the CupCake…

This is apparently a known problem …

Anyway, downgrading ReplicatorG to 0026 restored my connectivity …

So there you have it: I need ReplicatorG version 0026 to connect to the 3.0 firmware currently on my CupCake.

Happily, the ReplicatorG web site is still online in spite of MakerBot’s acquisition by Stratasys (though I note there have been no code updates since the acquisition). The download page has dowload links for only the last version (0040) but also has links to the Google Code archive, which on p3 has that 0026 for the Mac that I’m looking for.

Running ReplicatorG

I downloaded ReplicatorG 0026 and tried running it from the disk image before actually installing it on my laptop. I got the standard security warning:

OS X security warning about ReplicatorG

and had to look up to right-click and Open rather than double-click and change security preferences. After much playing around yesterday, I see that OS X Sierra does not remember approval I’ve given to run software on a disk image but does remember approval I’ve given to run software once it’s installed.

Once I got past that, I got a Java version error:

ReplicatorG 0026 needs Java SE6

Shockingly, clicking More Info... in that dialog does something useful — it takes me to Apple’s JRE download page for that version. After regaining consciousness, I installed that software and ReplicatorG starts up like a champ.

Can’t Connect to the CupCake (Because I Installed ReplicatorG Wrong)

It doesn’t appear to see the CupCake, though,

ReplicatorG no machineNode found

giving the error:

Could not load machine 'null' no machineNode found
could not load machine 'null' please check Driver-> <Machine Name>

It does see my FTDI USB-serial cable under Machine / Serial Port. It does not have anything listed under Machine / Driver and it does not bring up anything when I select Machine / Machine Information…

I don’t find much online about this. A Thingiverse Sailfish firmware comment sounds as though I simply have the wrong machine type selected, but I can’t even select a machine type. The tail end of a ReplicatorG comment thread sounds as though it can’t see USB-serial ports on current OS X versions, but it does see it. A much older MakerBot forum post mentions success after reseating the FTDI cable; but I don’t even know whether that’s the same issue and reseating mine didn’t help.

Installing ReplicatorG Correctly

It seemed obviously wrong that I couldn’t bring up the Machine Information… dialog, and I hunched that something was wrong there. Researching about the machine type, I saw that the ReplicatorG machine configuration page mentions a machines.xml file, which I didn’t have. But that sparked a memory — the ReplicatorG disk image had a machines folder in it and … oh, yeah.

The ReplicatorG Mac installation page clearly says to create a ReplicatorG folder under Applications and drag the entire contents of the ReplicatorG disk image into it. Which I hadn’t. I’d just dragged the app because in spite of remembering and knowing better, I’d just dragged the app.

I deleted the app from Applications, created the folder, dragged the contents, started ReplicatorG by right-clicking and choosing Open, and boom. Connected to the CupCake.

First Extrusion

I went back to my same blog post and found the nozzle temperature that works well for my CupCake, then set that and ran the extruder:

ReplicatorG 0026 extruder control panel

I don’t have any of my CupCake’s calibration settings loaded in yet, in particular my thermistor coefficients, so this temperature is only an estimate; but it worked well enough.

MakerBot CupCake test extrusion

First squeeze! Software installed; connected to and controlling the machine.

A Brief Aside About the FTDI USB-Serial Driver

When first I ran the ReplicatorG software, I wondered whether I had the FTDI USB-Serial driver already loaded on my MacBook from working with Arduino or whether the driver was missing and was the cause of the problem. ReplicatorG did find a USB-Serial under the Serial Port list, but I still questioned.

A bit of research shows that the driver’s presence or absence can be seen by running System Information and looking under Software / Installations. I didn’t see it there and I found that it can also be checked by running pkgutil --pkgs | grep -i ftdi . Didn’t see it there either.

The FTDI driver version supplied with ReplicatorG was of course quite old and I didn’t know how well it’d work on a newer OS X release. I went to FTDI’s Virtual Com Port (VCP) driver page, downloaded and installed version 2.4.2, and found that it made no changes to what I was experiencing. I’m wondering whether the FTDI driver is by now supplied as part of OS X or whether it silently installed when I installed the Arduino software on this MacBook.

Booting the MakerBot CupCake after Five Years Part 1: Powering Up

July 6th, 2018 by Keith Neufeld

I devoted Wednesday, my Independence Day holiday, to getting my CupCake 3D printer running again.

MakerBot CupCake

Foreshadowing: It turned out as a pessimist might suspect rather than as an optimist might plan.

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Why I Haven’t Touched the MakerBot CupCake for Four and a Half Years

July 4th, 2018 by Keith Neufeld

After making the filament de-duster five years ago about which I posted recently, I was finally getting consistent, reliable, beautiful 3D prints for the first time ever. For a month.

Then I was trying to print a draft of a pocket holder for a tube of moustache wax and comb and when I came back, I found that something had gone wrong after about 40 minutes of printing. I forget the order in which these occurred, but through the original attempt and two retries it:

  • kept running the filament while printing so the model snagged and the X-Y build platform skipped steps and lost its place; then when the print finished, kept the extruder on forever, creating a thumb-sized fungal growth of plastic
  • kept moving the X-Y build platform but stopped extruding
  • kept moving the X-Y build platform but shut off the nozzle heater, chewing a divot through the filament

failed MakerBot CupCake 3D print

The second try, I ran another print of the same model; the third try, I made a tiny dimensional change to the model or Skeinforge settings in case the extruder controller was glitching on some particular G code; but that doesn’t seem to have been the case. I got different bad behaviors and it seemed as though the extruder controller stopped taking instructions and kept doing exactly what it was doing at that moment.

I don’t know whether it’s a firmware bug, a power supply problem, a wiring problem, an extruder board problem, or something I haven’t thought of yet. I have (recently) found reference to a few of the DC extruder motor windings shorting, reducing the coil resistance and increasing the load, to the point that the extruder controller FETs burn out. But these weren’t burned out — they worked again immediately (for another 40 minutes).

And then before I could muster the motivation to troubleshoot it, both my laptop SSD and my workstation motherboard crashed, leaving me no working computer with 3D-printing software installed and no working computer with my CupCake’s calibration settings on it. And then time passed; OSes were upgraded; ReplicatorG versions increased; the barrier to reentry increased substantially; and I simply have not touched it since early 2014.

This shall change.

AMPduino [from 2011 Draft]

June 22nd, 2018 by Keith Neufeld

Another unpublished post dredged out of the distant past — this one apparently complete.

Soon after I got my friend Cort hooked on the Arduino, he said he wished he could easily carry it to the office to play with over lunch, to the tire shop to work on while he waited, etc. I offered him three-ring binders and boxed cases, but that wasn’t quite what he was looking for.

AMPduino case

After some discussion, we settled on an empty plastic case from a videocassette. I visited our Media Resources department, had their video director help me scrounge up a suitably large case (Cort says “U-Matic 3/4″ helical scan”), and updated the labeling.

AMPduino case, inside

Cort cut out the spindle posts and then stickied down the Arduino, a couple of breadboards, and some other things useful for prototyping and now does all of his development with the AMPduino. Handy for the workbench, the kitchen table, and the tire shop.

Filament De-Dusting for the MakerBot CupCake [from 2013 Draft]

June 22nd, 2018 by Keith Neufeld

I’ve just found this post I had started drafting in December 2013 and hadn’t finished. The remarks about reliability and long periods of disuse are still pertinent — this was one month before the last time I attempted to use it — as is the dust solution.

In the four and a half years I’ve owned my MakerBot CupCake 3D printer, I’ve never had it working well enough to use for more than a week or two at a time. My real frustration has been a lack of understanding what has failed and how to fix it, so much so that it’s been almost two years since I most recently gave up and put it away. [Written in December 2013, and I haven't used it since January 2014.] I know there are newer, more reliable printers on the market; but it sure seems like it should be possible to get the CupCake to work reliably, if I’m willing to upgrade critical parts.

In the intervening time [meaning 2011 to 2013], my friend Joel has run some prints for me on his Thing-O-Matic. Recently while chatting over a print in progress and checking whether the filament was jammed (solution: his build platform’s aluminum heat spreader was bolted tightly around all the edges, expanding when hot, bulging up in the middle progressively over an afternoon of attempted printing, and blocking the nozzle which was enough to jam things up), he mentioned that his nozzle had jammed to the point that he couldn’t even push filament through by hand with pliers (yes, my problem exactly) and that he had solved it (oh???).


Joel had disassembled his extruder and lightly drilled most of the filament out of his clogged nozzle with an undersized bit, as I had in the past; then soaked out the rest of the plastic with acetone, as I had also. But when removing the clogged filament, Joel noticed it was quite dirty and made the mental connection with dust on the filament. When he reassembled, he added a toothbrush to wipe dust off the filament on its way in and has also made a point to keep his supply bagged and/or boxed. Since then (and until the expanding heat spreader), he’s had no further troubles with clogging.

This is not a new issue, but I had never heard anyone indicate it had so completely jammed their nozzles that their extruder wouldn’t extrude.

And it fixed my CupCake. Mostly. For a while.

Filament-wiping sponge holder, freshly printed

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New Tray for Fischertechnik Computing Box

June 18th, 2018 by Keith Neufeld

My weekend’s entertainment was making this wooden tray to hold the parts from an Apple ][ era engineering construction toy.

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