Archives for the month of: April, 2011

This is a Darwin RepRap that was built by WJT from a kit from Bits from Bytes. It was started in May 2009, and first successfully printed on 27 November 2009. A heated bed was added in May 2010, built in the Czech Republic by Josef Prusa.

About This Build

  • Build: May 2009 – June 2009
  • Tuning: June 2009 – December 2009
  • First successful print: 27 November 2009
  • Tuning with heated bed: May 2010


  1. Image Gallery
  2. Useful Links
  3. Skeinforge Settings for Unheated Bed
  4. Skeinforge Settings for Heated Bed

Image Gallery

Go to the image gallery at Flickr.

Useful Links

Skeinforge Settings for Unheated Bed

  • Material: ABS from
  • Start with Rapman ABS default settings
  • No extruder fan for any prints
  • Smaller parts (less than 50mm on a side with raft)
    • Feed Rate 12 mm/s
    • Raft Temp 235 C
    • First Layer 230 C
    • Next Layers 240 C
    • Raft Margin 5 mm
    • Extrusion 270 (27 RPM)
  • Medium parts
    • Feed Rate 8 mm/s
    • Raft Temp 233 C
    • First Layer 228 C
    • Next Layers 238 C
    • Raft Margin 10 mm
    • Extrusion 250 (25 RPM)

Skeinforge Settings for Heated Bed

  • Test Raft
    • Started with 500 W power supply
    • Test raft breaks free when thermistor temp is 46 C (infrared temp around 62 C)
    • Test raft sticks when thermistor temp is 61-63 C (IR temp around 77-80 C)
    • Feed Rate 20.7 mm/s
    • Head Speed 4.0 mm/s
    • Raft Temp 235 C
    • Bed Target Temp 100 C
  • Raftless Object
    • Still having problems getting a raftless object to stick to the bed (with kapton tape on aluminum). Current ratio of flow rate to feed rate is 17.86
    • Bed Temp 100 C
    • Feed Rate 28.0 mm/s
    • Flow Rate (Extrusion) 500 (50 RPM)
    • Temp of Raft 238
    • Temp of First Layer 238
    • Temp of Shape 238 C
    • Raft Base Layers 0
    • Raft Interface Layers 0
    • Things to Try Next…
      • Replace Power Supply with 750 W unit
      • Update Skeinforge
      • Increase temp a little bit (240 C?)
      • Increase feed rate while keeping flow:feed ratio the same or raising it slightly
      • Up flow rate to feed rate ratio a bit
      • Install Raftless plug in?

The MakerBot Cupcake is a RepRap-derived 3D printer. I built machine number 00018 between 24 April 2009 and 18 February 2010.

About This Build

  • Machine number: 18
  • Build: 24 Apr 2009 – 15 Feb 2010
  • Tuning: 15 Feb 2010 – 18 Feb 2010
  • First Successful Print: 18 Feb 2010


  1. Image Gallery
  2. Useful Links
  3. Testing the Electronics
  4. Tuning
  5. Thermistor Settings
  6. Skeinforge Settings

Image Gallery

Go to the image gallery at Flickr.

Useful Links

Testing the Electronics

  • Opto-endstops
    • Checked all connections with dissecting microscope set at 0.7 x 10x
    • Re-soldered one loose joint
    • Used PB-503 proto-board to build a little test rig for both kinds of connection
    • All endstops seem to be working correctly
  • Stepper motor drivers
    • Checked all SMD and through-hole connections with dissecting microscope
    • Had to ground the sense line of the ATX power supply unit to get it to power on without a computer attached (following Masked Retriever’s hack)
    • Checked that green power LED comes on for all stepper motor drivers
  • Burning the bootloader
    • Used Arduino 0017 on Mac OS X with Sanguino 1.4-r1 support
    • USBTinyISP needs to have jumper across two pins near cables in order to provide +5V to Sanguino
    • Power LED on Sanguino doesn’t light up even though Arduino software claims that bootloader burns successfully
  • Firmware
    • Using RepRap Gen 3 Firmware 1.2
    • Don’t forget to copy reprap-r3g-firmware-1.x/libraries/* to arduino-00xx/hardware/libraries/ (otherwise you will get an error that it can’t find simplepacket.h)
  • Debugging
    • The power LED never lights up on the Sanguino
    • Unfortunately I am now getting the following error: “avrdude: stk500_recv(): programmer is not responding”
    • Tried connecting LED to Pin 13 and resetting. It doesn’t flash, which suggests something may be wrong with bootloader. When I power with the ATX power supply and hit the reset button, the Debug light flashes 4 times; the power light doesn’t come on at all.
    • Tried putting a low voltage through the SMD LEDs that indicate Power and Debug (on the LEDs, cathode is marked with green stripe). Both LEDs work.
    • Replaced motherboard.
    • Once motherboard replaced, extruder controller and stepper motor drivers work perfectly
    • Invert Y axis in ReplicatorG


  • First mini mug is eye-shaped when looking down at it from above. Loose belt on X axis.
  • ABS sticks to foamcore but object pops loose halfway through build. Made an acrylic plate to cover the build platform, covered one side with kapton tape and roughed the other with sandpaper.
  • Natural ABS extrudes smoothly at 220 degrees C
  • Difficult to get ABS to stick to the platform
  • Part way through a full day of tuning, realized that the idler wheel had slipped sideways off of the bearing and the filament was jammed beside it. Disassembled extruder and rebuilt idler wheel and bearing with Special T cyanoacrylate. Johnny Russell also suggested using a zip tie as a filament guide, shown in this photo. If the problem recurs, might try double-thick idler wheel or machining new one out of some other material.

Thermistor Settings

  • Assume I have older (1mm) thermistor – didn’t measure it before building extruder
  • Beta=4881, r0=93700, t0=24

Skeinforge Settings

  • Material: MakerBot Natural ABS
  • Start with Configuring Skeinforge page
  • N.B. These settings are pretty good, but could use a little more tuning; see the “Fundamental Settings” section of the Configuring Skeinforge page to get them perfect
  • Carve
    • Layer Height: 0.4
  • Raft
    • Temperature of Raft: 220
    • Temperature of Shape Next Layers: 220
    • Temperature of Shape First layer Outline: 220
    • Temperature of Shape First Layer Within: 220
    • Temperature change times: 0
    • Interface Layers: 0
    • Base Layer Thickness over Layer Thickness: 1.7
    • Raft Outset Radius Over Extrusion Width: 10
  • Speed
    • Flowrate Choice: PWM
    • Flowrate PWM Setting: 255
    • Feedrate: 25
  • Fill
    • Solid Surface Thickness: 3
    • Extra Shells On Sparse Layers: 2
    • Extra Shells on Base Layers: 3
    • Extra Shells On Alternating Solid Layers: 1
    • Infill Pattern: Grid Rectangular
  • Deactivated modules
    • Cool
    • Hop
    • Oozebane
    • Stretch
    • Unpause
    • Comb
    • Multiply
    • Polyfile
    • Wipe

Let me wrap up this series of posts by suggesting that the most important aspect of the method is to practice what is called kaizen in Japanese: make continuous small improvements.  Part of this is simply a willingness to keep tweaking something even while it is working.  The other part is an ability to measure the effects of the changes that you do make.  When I started looking at the word counts for my writing from day-to-day, I realized that the kind of music that I was listening to made a difference.  So I started systematically buying songs at iTunes and seeing what kind of impact they had.  When I found something that increased my productivity, I used the ‘Genius’ feature to find related songs and added them to my playlist.  (iTunes: “Want to tell your friends about this?  Connect with them on Ping.”  Me: “Are you crazy?  My friends would mock me until I cried.  I can barely admit to myself that I spent 99 cents on that song.”)  But if listening to terrible music allows me to write 14% more each day, I have one extra day each week to work on something else.

Programmers use the verb refactor to describe the process of taking apart something that is working, optimizing the pieces, and putting it back together.  For a while I used DevonThink to organize all of my notes, but I realized that the features that made it work so well for a focused research project also made it too cumbersome to handle the minutiae of day-to-day life.  So I’m now using OmniFocus (and Getting Things Done) to keep track of the things that I have to do, and using Evernote to collect random notes on everything that is not part of an existing research project or course that I’m teaching.  ProfHacker has a number of good posts about things that you can do with Evernote (1, 2, 3).  For me, the main advantages are that it is lightweight, cloud-based and accessible from almost every computing device I own.

So far we’ve discussed creating a backup system, a local archive of OCRed digital sources and a bibliographic database.  We’ve also covered a number of strategies for adding new material to our local repository automatically, including search, information trapping, and spidering.  Two programs lie at the core of the workflow, DevonThink Pro and Scrivener.  When I add a new source to my local repository, I create a bibliographic record for it, then I index it in DevonThink. Once it is indexed I can use the searching, clustering and concordance tools in DevonThink to explore my sources.  Since everything that is related to my project is indexed in DT, it is the one local place where I go to look for information.  Rather than explain all of the useful things that can be done with your sources in DT (and there are a lot) I will simply refer to the articles by Steven Johnson and Chad Black that convinced me to give DT a try:

A couple of notes about DT.  If you do decide to buy the software, buy the $10 e-book on how to use the software at the same time.  There are a lot of powerful features and this is the fastest way to learn them.  Unlike Johnson, I store everything related to my project in DT.  That is why I advise bursting large documents into smaller units for better searching and clustering.  As a historian, I also tend to write books that have more chronological structure than his do, so I use a sheet in DevonThink to create a chronology that can be sorted by date, name, event, and source.  It is not as flexible as a spreadsheet, but it does not have to be.

For writing, I am using Scrivener, which allows me to draft and rearrange small units of text easily.  I can copy a passage that I’ve just written from Scrivener into DT and use the magic hat to find anything in my sources that may be related to that paragraph (just as Johnson describes).  The super-secret monograph consists of seven chapters of five subsections each.  In Scrivener, I can see the status of each of those pieces at a glance: how much has been written, how much needs to be done, and how each relates to other subsections.  Rather than facing a yawning gulf at the bottom of a word processer screen, and potential writer’s block, I can see the book take shape as I work on it.  When the draft is finished in Scrivener, it is easily compiled to whatever form that the publisher wants.  I can’t say enough good things about Scrivener.  By itself I’m sure it has doubled my writing speed.

The key is working with small enough units of text.  When you cite a source, you are typically referring to a part of it: a quote, a paragraph, a passage, an argument.  Similarly, when you write a book, you can only work on a small part of it at one time.  Inappropriate tools force you to manipulate objects at the wrong scale, usually the whole document, however long.  Better tools, such as DT and Scrivener, allow you to focus on exactly the pieces you need for the task at hand.