The Unprinter Blog

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Finale

by matt6280

We are done the project. It may need more work, but the group has been told to never let perfect get in the way of done/functional. Here is a links for the YouTube video, more images and the wiki respectively. It has been a great experience.

https://github.com/bwkeller/unprinter/wiki/Sustainability-3A03-Report:-Recycling-Filament-Pneumatically

http://youtu.be/bI9zWh7cWMo

 

Latest Prototype: Process and Results!

by kghounsell

This week, we got very exciting results: a thin stream of melted plastic!

After rinsing out the oil typically found in the pipe we chose to use, we began heating our vessel (the pipe and its lid), which had already been fitted with a small hole for the filament. Because our chamber is quite small (for easier testing), we repurposed the heating element of the hot plate to wrap around the vessel to allow for greater contact (as shown in the attached image). The heating element was quite malleable and we were able to coil it by wrapping it around a rod.

Our repurposed heating element and heating chamber

Our repurposed heating element and heating chamber

Then, we began to heat the plastic. Because we did not yet have the vacuum, which we plan to later use to avoid air bubbles, we simply situated the  plastic in the repurposed hot plate element. The heating process was slow as the coils in the hot plate left considerable space between the heating element and the heating chamber. We hope to tighten the coils around the chamber for next week, to make a more efficient system. Once the chamber was sufficiently hot (around 200 degrees celsius), we connected it to the air compressor and let it run. Unlike our previous, non-pressurized experiments, in which the the plastic was as thick as glue, here the plastic flowed out of the chamber as a liquid! We are looking forward to next week, when we’ll hopefully have the benefits of the vacuum and more efficient heating, and we can begin extruding plastic!

Update

by matt6280

Quick Fact From Research: PLA is specially made to degrade effectively in municipal compost facilities. This allows it to work well for 3D as it will not biodegrade below 60 degrees Celsius. Current quality control is looking at ensuring that we lowball the diameter of our filament. This will ensure that it can get to and then through the extruder easily. A current idea for quality testing is to have the filament run through a specifically shaped hole before use. A key part of this project is ensuring that it can be made with easily acquired parts and equipment. Here is a picture of ourImage latest melting test.

Documentation Update: Insights on Melting Plastic

by kghounsell

This Monday, we put our first prototype to the test using some scrap PLA plastic. To get started, we set up the hotplate (connected to the Variac to better control the temperature). Once the pot had heated to about 183 degrees celsius, we added two thin pieces of plastic – one dyed and the other un-dyed. When the temperature had reached about 200 degrees, both plastics had melted. The coloured plastic was very viscous, and kept the shapes that it was manipulated into. The clear plastic on the other hand was somewhat less viscous, with a consistency like honey. At 245 degrees, the plastics had still not liquefied, and at 295 the coloured (white) plastic was singed at the edges, but still did not flow, suggesting that we will need to change our approach.

IMG_2083         IMG_2086

In order to produce more fluid plastic that can be reshaped into filament, we have created a new design. We hope to be able to remove the air bubbles by melting the plastic in vacuum, and forcing it through the extruder head by refilling the chamber with oxygen and increasing the pressure. Our modified design will require a hose tube to connect the vacuum (which we already have at Think Haus) and a metal pipe and lid. These materials will be brought to our next meeting so we can experiment some more!

Check out a sketch of our latest design below:

IMG_2090

by phille2

Scrap PLA

A bin of PLA plastic that we’ll use as test stock.

by saeeds7

temperature sensing circuit

by saeeds7

Temperature measurements using arduino and pictures of circuit

Temperature in Degrees Celscius

by saeeds7

Finally managed to find some code online from Ben Miller which uses Steinhart-Hart equation to convert from resistance to temperature:

link for website for code: http://mac.tutsplus.com/tutorials/electronics/how-to-read-temperatures-with-arduino/

#include <math.h>         //loads the more advanced math functions
void setup() {            //This function gets called when the Arduino starts
Serial.begin(9600);   //This code sets up the Serial port at 115200 baud rate
}
double Thermister(int RawADC) {  //Function to perform the fancy math of the Steinhart-Hart equation
double Temp;
Temp = log(((10240000/RawADC) – 10000));
Temp = 1 / (0.001129148 + (0.000234125 + (0.0000000876741 * Temp * Temp ))* Temp );
Temp = Temp – 273.15;              // Convert Kelvin to Celsius
return Temp;
}
void loop() {             //This function loops while the arduino is powered
int val;                //Create an integer variable
double temp;            //Variable to hold a temperature value
val=analogRead(0);      //Read the analog port 0 and store the value in val
temp=Thermister(val);   //Runs the fancy math on the raw analog value
Serial.println(temp);   //Print the value to the serial port
delay(1000);            //Wait one second before we do it again
}

Resistance Sensing

by saeeds7

I just got of to a start with working on some thermistors. Managed to find some code for it and a working circuit diagram. Serial Printing on the computer was used as opposed to and LCD to save  cost. All that was required was to use a thermistor, arduino and two 4.7 kilo-ohm resistors.

 

The code is provided by the adafruit system below which measures resistance proportional to temperature:

 

// the value of the ‘other’ resistor
#define SERIESRESISTOR 10000    
 
// What pin to connect the sensor to
#define THERMISTORPIN A0
 
void setup(void) {
  Serial.begin(9600);
}
 
void loop(void) {
  float reading;
 
  reading = analogRead(THERMISTORPIN);
 
  Serial.print(“Analog reading “);
  Serial.println(reading);
 
  // convert the value to resistance
  reading = (1023 / reading)  – 1;
  reading = SERIESRESISTOR / reading;
  Serial.print(“Thermistor resistance “);
  Serial.println(reading);
 
  delay(1000);
}

Project Set-Up

by kghounsell

This week, we worked on our setup for the 3D unprinter. Using a drill, we created a hole a couple centimeters in length in a pot, and removed the handle. Then, we used epoxy to glue a brass end plug into the hole in the pot. The brass metal piece will ultimately be used to define the size of the filament, so we’re planning to drill a hole about 1.83 mm wide into it.

After the epoxy was mixed and applied to the pot and metal piece, we tested our hot plate to see how hot it could get. We stopped measuring the temperature after about 290 degrees Celsius, and it seemed still be rising. This should be more than hot enough to melt PLA and even ABS!

After the epoxy has had eight hours to dry (in a warm area), we’ll be testing it with water to make sure it doesn’t leak, and hopefully we will be trying with plastic next week!

IMG_2074 IMG_2078