MakerBot Industries

Hollow Calibration Cube by Starno

Yesterday, I had a conversation with MakerBot Operator Rift and MakerBot Mechanical Engineer Nick Starno in the BotCave about the Skeinforge tool “Jitter.” Rift had come to visit for a consultation about Skeinforge calibrations and Starno’s excellent Print-O-Matic SF Assistant¹.

Rift had printed a couple of Tornadoes in his Thing-O-Matic using ABS and wanted to see if Jitter was the right tool to avoid seam that can appear on the sides of thin-walled geometries. (Jitter was designed to adjust where the z-height increments when completing a layer.) Starno and Rift considered the pane within Skeinforge for Jitter and found the option “Jitter over Perimeter Width (ratio).” How exactly does this tool function? Lacking sufficient details within Skeinforge, they jumped into experimentation, trying a range of values so that they could test results.

There have been a number of attempts to create wikis for various versions of Skeinforge, but most of these web resources are in such disarray that those who consult them leave more frustrated than informed. But there is a secret, hidden in plain sight — the best reference for most of the tools within Skeinforge are included as prose comments within the python scripts for the tools themselves. Even as ReplicatorG integrates assistants to help save users from Skeinforge gauntlet, taking a look at these comments can be helpful reading to get a sense of how these tools function and what are their interdependencies.

To read these comments, look inside your ReplicatorG folder for the “skein-engines” folder. Nested deep within the folder for the version of Skeinforge you want to learn about are the “craft_plugins” folders that contains the python scripts themselves.

Grab yourself a plaintext application² and investigate those python scripts one at a time, with a special emphasis on Carve, Fill, and Speed. While in places the scripts (in active development) diverge a bit from the comments, these comments remain your best shot for reading full explanations for what each tool was created for and how to use it.

Take a look at this excerpt from the Jitter page, that was able to help Starno and Rift investigate this tool:

“Jitter Over Perimeter Width===Default is two. Defines the amount the loop ends will be jittered over the perimeter width.  A high value means the loops will start all over the place and a low value means loops will start at roughly the same place on each layer.”

Now that is a huge improvement over the amount of information available in the Skeinforge Jitter tool pane!

1. which is now being integrated into the beta for ReplicatorG 25 [↩]
2. I recommend notepad++ for Windows and TextWrangler for Mac OS X [↩]

Thingiverse citizen nrp uploaded a Python script that enables a Kinect to track a hand in the air and feed the corresponding Gcode to a 3D printer – a process he calls “gestural 3D printing.”  From the video above you can see how the monitor provides visual feedback for the user while his RepRap in the background mimics the user’s movement.

Gestural 3D Printing by nrp

Really, the best description is the video:youtube.com/watch?v=BRJY927raTo Also on my website:eclecti.cc/computervision/gestural-printing-jumping-the-shark-on-kinect-hacks We’ve seen a seemingly endless array of amazing Kinect hacks over the last few months, from superhero generators to obstacle avoiding quadcopters. However, it was only a matter of time before someone came up with a hack so inane and irrelevant that it would bring shame to the entire hobby. That time is now, and that someone is me. I bring to you, gestural 3D printing! Using the Kinect to track your hand, you can draw one layer at a time, with the printer following your every move. Pushing forward extrudes plastic, while pulling your hand back will start a new layer. Who needs difficult and confusing CAD software when you can just directly draw the object you want to print?

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