3D Printing At Discovery Charter School – Part 13

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By David Lewis

And now for something different…

This weekend as The Herd worked on getting the Rapman back on line (a problem with a torn cable) Vernon brought out a project that he had been working on over the last week – A Lego Robotics powered 3D printer.

Vernon’s project uses elements from his Lego NXT kit to begin controlling the extruder head (more on that in a moment) in two active dimensions (X &Y) with plans to add in the Z axis. As soon as he can come up with a way to accurately control either the platform (ala Rapman or the print head like the MakerBot) he will build it in to the system. Either way, the Herd was blown away by the concept and the ingenuity that went into realizing and building the bot from Lego parts.

The core construction is all Lego.

All the drives, pulleys and related items are stock Lego components and the control sequence is a set of linear commands via the Lego code about how much linear distance to move the carriage. The system does not (yet) handle Cartesian points or G-Code.

The Extruder

A key element of any of these printers is the extruder head which is not an over the counter part. For the Rapman you can build your own or purchase a pre-built head. We have been using the pre-built heads, but Vernon didn’t have access to those so he bought an inexpensive hot-melt glue gun and mounted it into the device.

As anyone who has used a glue gun knows, you have to keep squeezing the trigger to keep the flow of glue moving. Vernon’s printer uses an elliptical assembly driven by one of the NXT motors (the orange wheel) to pull the trigger repeatedly and make the glue flow. Early tests with the system have resulted in the fully automated deposition of interesting blobs of glue on the print bed.

No lack of creativity here and The Herd thinks they can overcome some of the design challenges as they further explore using the Lego system to build their own printer. This is a great example of the Herd using what they have learned in just a few months as a basis for their own creative directions.

In the meantime, we got the Rapman 3.1 back on line and calibrated. A boring, but KEY learning from our experience with the torn cable is: “When changing from one feedstock to another, keep the print head HOT in order to avoid pulling too hard on anything”. We had tried to change form PLA to ABS with a cold print head and the amount of effort required to get the print media out caused some damage.

Next week, we install the lashless gears!

Part 14 >>