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February 16th, 2011

In order for the ABS plastic to stick well enough to the polyimide film build base it needs to be heated to at least 100°C [212°F]. I purchased an Omega CN7500 temperature controller to provide power to the flexible heaters. One of the really nice things about this controller is that it features auto-tuning PID control so you will get the best temperature control without having to manually set all of your PID constants.

Wiring to the PID Temperature Controller

The blue wires connect to the flexible heaters, four per connector. Then the orange-ish wire is a J type thermocouple connector. I used connectors instead of hard wiring everything to make it easy to remove the build plate if needed.

Testing the Heated Build Base

First tests were successful after the controller ran through a few heating cycles in order to calibrate the PID settings. For the tests I was concerned about the EMI that would be generated from the relays turning on and off in the controller, so I placed it behind a steel block. This EMI could potentially crash the machine micro controller while running code. I had run into this problem on my Fab@Home by placing the temperature controller too close to the micro controller. This time, I made sure to mount the temperature controller out of the way, and I have not had any problems.

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So, I just got home and checked my mailbox; Take a look at the cover of this weeks Economist:

"Print me a Stradivarius; The manufacturing technology that will change the world"

The cover reads: “Print me a Stradivarius; The manufacturing technology that will change the world” It features a 3D printed Stradivarius violin, made on an EOS system. Likely it was made of a laser sintered plastic, because the caption reads “(and it plays beautifully).” If it was made on one of EOS’s metal sintering systems, I don’t think it would play as well.

You can check out the two 3D printing articles that appear in the print version here online:

Leader

Briefing

Things sure do seem to be moving at an exponential rate in the 3D printing world these days… especially if such a world-class and well respected publication like The Economist is taking notice.

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February 14th, 2011

The Plastic Extrusion Tool takes in a feedstock of 3mm ABS plastic filament. The filament is compressed between a servo motor driven knurled pulley and an idler wheel. The filament is then forced down through a 0.50mm nozzle heated to 230°C [446°F].

Initial Plastic Extrusion Toolhead

The black parts that comprise the body of the extruder were made on a commercial 3D printer. In the above image, the extruder controller board [left] provides power to the nichrome wire heated extruder barrel and nozzle using PID control. The brass nozzle and heater barrel are covered with ceramic insulation for better temperature control. This heated portion is then itself insulated from the plastic tool housing via a PTFE tube, which was later changed to PEEK.

Backside of the Plastic Extrusion Tool

Six 1/4″-20 screws fasten into the tool head to secure it to the Z stage.

First Moutning the Plastic Extrusion Toolhead Mounted onto the Z Stage

Current Plastic Extrusion Toolhead

This is how the current Toolhead looks. The PTFE tube was replaced with a PEEK version, which is better suited to handle the loads of the melting plastic under temperature. Also, an aluminum plate was bolted to the black housing to provide more structural rigidity. A magnetic rotary encoder [right] provides closed loop feedback on the drive motor for more accurate extrusion, though getting this to work correctly with the extruder board firmware has proven difficult. Also the magnetic rotary encoder board is mounted to the drive motor via a custom part that was printed on this machine.

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