Building From An SD Card

As of ReplicatorG 0007 and Gen3 Firmware v1.3, the Cupcake CNC supports running a build from an SD card. Builds like this have many advantages— you can run other tasks on your host PC during a build without worrying about buffer underruns, or even unplug your Cupcake CNC from your host PC completely during a build!

Using an SD card with ReplicatorG 0007 and Firmware v1.3

If you've installed the v1.3 firmware, ReplicatorG 0007, and have an SD card, you're pretty much ready to go! Just follow the steps below.

Format the SD card

At present, the RepRap motherboard requires that you format your SD card with a FAT16 filesystem. No other filesystem will be recognized at present! To format an SD card:


use the "gparted" utility. A graphical interface for gparted is available in Ubuntu under menu:System → Administration → Disk Utility. (TODO: elaborate on this)

Windows (For Windows XP, FAT16 is the default format)

right-click on the SD card and select "Format…"

Mac OS X 10.5 Leopard

from this article. Make sure your disk is named MAKERBOT or substitute your choice of name in the command. Run the Terminal application and type the command

diskutil partitionDisk /Volumes/MAKERBOT 1 MBRFormat "MS-DOS FAT16" "MAKERBOT" 1G

Mac OS X 10.6 Snow Leopard

First run:

diskutil list

this lets you identify the disk number for your SD card. I get a bunch of stuff, then I find this:
  #:                       TYPE NAME                    SIZE       IDENTIFIER
  0:      FDisk_partition_scheme                        *1.0 GB     disk2
  1:       Microsoft Basic Data MAKERBOT                1.0 GB     disk2s1

So in the next command I use "disk2" as one of the parameters. Update as needed for whichever is your MakerBot SD Card disk number above. When I run this:
diskutil partitionDisk disk2 MBRFormat "MS-DOS FAT16" MAKERBOT 1G

I get this result printed to the Terminal window:
Started partitioning on disk2
$<3>Unmounting disk
$<3>Creating partition map
$<3>Waiting for disks to reappear
$<3>Formatting disk2s1 as MS-DOS (FAT16) with name MAKERBOT
$<3>Finished partitioning on disk2
  #:                       TYPE NAME                    SIZE       IDENTIFIER
  0:     FDisk_partition_scheme                        *1.0 GB     disk2
  1:                 DOS_FAT_16 MAKERBOT                1.0 GB     disk2s1

NOTE: the "MBRFormat" parameter is CRITICAL. you need FDisk_partition_scheme, NOT GUID_partition_scheme for MakerBot Mobo to read the disk filesystem correctly.

NOTE: you may need to use "MBR" instead of "MBRFormat".

Get the build on to the SD card

There are now two ways to put a build on an SD card! If you have an SD card adapter or SD card slot on your host computer, you can use "build-to-file"; otherwise, you can upload through ReplicatorG over the serial connection. The build-to-file technique is much, much faster than the ReplicatorG upload, so if you have an adapter or card slot, it's highly recommended.

Use build-to-file to put the build data directly on the SD card

Build-to-file is available in ReplicatorG 0010 and later.

  • Insert the SD card in your adapter or card slot. Make sure the "Lock" switch on the SD card is off!
  • Open a .gcode file in ReplicatorG.
  • Click the "Build to file" button.
  • You will be prompted for a filename to save the build data as. Navigate to the top-level directory of your SD card and save the file there. The filename should be a short 8.3 filename (the first part should be 8 or fewer characters long) and have the extension ".s3g". Otherwise replicatorg will show the file yet when you click on it the program will say it is not found. 8.3 File naming convention explained here.
  • Unmount your card and put it in your printer— you're ready to go!

Upload the build to the SD card through ReplicatorG

  • Insert the SD card in the slot in the motherboard until you hear a click. Make sure the "Lock" switch on the SD card is off!
  • Open a .gcode file in ReplicatorG.
  • Click the "Upload to SD card" button.

Any built-in pauses that would normally appear during your build will bring up dialogs now, so just click "ok" on messages like "wait for extrusion".

Please note that because we're uploading over a slow serial connection and the write mode we're using is fairly slow, it can take a long time to upload a build— a two-hour build can take as much as twenty minutes to upload!

Run the build from the SD card

Once the build has been uploaded, click on the "build from SD card" button. The nozzle will raise, pause and wait for the plastruder to reach temp, extrude some material and then immediately start to print. The extruded material will need to be quickly wiped away before the build begins. Once a build has been uploaded, it can be built from the card as many times as you like.

Stopping a build from the SD card

If the PC is still attached, you can hit the STOP button on the ReplicatorG application to stop the build. If the PC is not attached, hit the reset button on the Motherboard.


  • There are no interactive holds during SD card builds— they'll run as if the holds were not present.
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