Wednesday, May 21, 2014

Updated Machinekit Images

After receiving a BeagleBone RevC with 4GB on-board eMMC, I noticed the latest images have grown to the point they are essentially unusable on a 4GB device.

I have updated the Machinekit images to exclude the previously required documentation build dependencies, which saves over 1GB of space on the images!  There is still a lot more room to be recovered once ARM binary packages become available, but for now the space savings means you can comfortably run Machinekit on a 4GB uSD card or the built-in 4GB eMMC on a RevC 'Bone.

Thursday, May 15, 2014


The CRAMPS V2.1 circuit boards are fabricated and heading my way.  I am planning to sell the bare boards for a nominal cost (under $5), but I may get motivated and sell some DIY kits that include all the parts needed to assemble your board.  The kit would probably be around $50-60, which is pretty much my cost for the parts in low volume, and I'd only be able to make about 10-20 kits total (before I run out of circuit boards).

So a quick informal poll:  If you are interested in buying a bare PCB or a DIY kit for the new CRAMPS board, send me a direct email and if I get enough interest kits I'll try to put some together.  Sending me an email places you under no obligation to actually buy anything, nor does it guarantee you'll actually get a kit should I decide to make some.

I am also working on getting someone to build and sell assembled boards, but that is a process that will likely take another couple months.  The kits would probably be available in 2-4 weeks, depending on how long it takes the PCBs to arrive and if I find any problems with the first prototypes.

Saturday, May 10, 2014

Velocity Driven Extrusion

Bas de Bruijn has been working on controlling his 3D printer with Machinekit, and has implemented a unique way to control the extruder.  Rather than make the extruder a fourth axis as is done in most setups, Bas is modeling the extruder behavior and automatically controlling the extruder motor velocity based on the movement of the conventional XYZ axis.

The problem with using a traditional 4-axis coordinated move for extruding plastic is the extruder behavior is non-linear.  Typically not enough plastic is extruded at the start of the move while pressure builds in the extruder and too much is extruded at the end of the move.  This problem is made worse by any changes in velocity along the move, as may be required by the acceleration constraints of the machine.  The retract and precharge settings in most slicer programs help with this issue to some extent, but cannot truly match the extruder behavior.

By dynamically controlling the extruder velocity, Bas can start with a simple linear mapping of movement speed to extruder speed (how a standard 4-axis coordinated move would work), and enhance that by adding terms to compensate for changes in speed and acceleration.  Changing the model used to drive the encoder only requires changes to the HAL file for the machine, allowing complex control theories to be tested quickly and easily without writing code.  Based on the print results Bas is already achieving, it looks like this approach is already working pretty well, and there is still much room for improvement.

Keep watching Bas' blog for updates, and let me know if you are doing anything unique with Machinekit!

Friday, May 9, 2014

Machinekit BeagleBone Debian Images Released

After what has been far too long, I am please to announce a new official release of the Machinekit image for the BeagleBone.  The release of the RevC BeagleBone Black with it's 4GB eMMC and switch to Debian makes the BeagleBone an even better choice for machine control!

There are lots of significant changes with this release, so I recommend everyone using Machinekit updates when practical.  The biggest change is the switch from my "enhanced" version of Robert Nelson's minimal Debian build to generating images based on the official BeagleBone Debian.  That means all the BeagleBone specific features like node.js, USB networking, etc. should work just like they would on a factory BeagleBone.  Of course there are a LOT of changes included with this, like switching from xfce to lxde, changing from sysvinit to systemd, and many others.  On the plus side, the Machinekit images are now very similar to the shipping BeagleBone release, so it should be easier to find documentation and ask for help.

The other really big change is a switch from LinuxCNC to the Machinekit project.  Machinekit enables LinuxCNC's real-time core to operate on a wide variety of platforms, making it possible to run on the BeagleBone.  I had been hoping the required real-time changes would become part of mainline LinuxCNC (and they still might), but they have been passed over for the upcoming 2.6 release.

If you are lucky enough to have a BeagleBone RevC, there is an (untested) eMMC flasher image available as well.  If you would like a tested and verified working eMMC flasher image, feel free to FedEx me your RevC 'Bone!  Otherwise, you'll have to wait until one of the two I've ordered actually arrives for me to test.  ;-)

Thursday, May 8, 2014


I finally got around to finishing the updated version of the CRAMPS board.  This version focused on simplifying the design as much as possible, and I really like the end result.  It feels much closer to the original RAMPS for the Arduino Mega in spirit than the previous 1.0 version and the RAMPS-FD.

Changes in this version include:

  • No fine-pitch surface mount parts, so the board is much easier to hand assemble
  • No servo outputs
  • SPI expansion header changed to allow use as extra GPIO if needed
  • Expansion headers modified to support an additional 3-axis add-on board (the CRAMP3)
The design files remain on github, and the home page for the design is still the CRAMPS page on the RepRap wiki.  A BOM file including Mouser and Digi-Key part numbers is also available via Google docs.  The boards  have been ordered, and should arrive before the end of May.

While the design is fully open, not everyone wants to build their own boards from scratch.  I am working on getting someone to build and sell completed boards, so stay tuned for updates!

UPDATE: 2014.05.12 - The first batch of 20 boards has shipped, now the 0-30 day wait for a "registered air parcel" begins.