Retrointerfacing

- connecting past and future -

Archive for February, 2010

nylon extruder #2

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nylon1 nylon2 nylon3

After the promising results with the first nylon extruder, we (woutzweers and I) made a new nozzle following reprap extruder size (so a 3.5 mm feed hole and a 0.5 mm extrusion hole). The extruder head consist of a small piece of brass with two holes placed at 45degree angle. The soldering iron has been mounted in the clamp of a milling machine, everything in the following movie is hand-operated.

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February 13th, 2010 at 7:45 pm

Posted in fablab,fabrication

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Getting a HP7585B plotter to work

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r0013747 I recently got an abandoned HP7585B plotter. Probably over 30 years old. However, perhaps fast and accurate enough to do some serious fabrication? Why not add a cutter wheel and cut foil, or fabric?

Anyway, first hurdle to take is to get the think working. Searching for drivers on internet resulted in two options: 1: winline (http://winline.com) or 2: autocad/autodesk built in..

I tried to connect it using a normal serial 1:1 cable. No result. Self test of the plotter worked. Searching HP’s sites, some old re-converted pages came up showing a different cable mark-up. Why didn’t anyone just used one type of serial cable in those days? Oh wel.. HP gave a pinout on their site Unfortunately, the conversion to modern web-site instead of 15years-ago-ascii in courier had crippled the ascii cable pinout.. Browsing on a different site showed why the pipes were included (this is how it looked: (unfortunately the spaces get crippled)

hpcable

Now after this connection has been made, the printer can be controlled using HPGL. On the HP site the following string is used to test the plotter connection:

IN;SP1;PA0,0;PD1000,1000;SP0;PG;

which will draw a diagonal line from 0,0 to 1000,1000. After making a connection using hyperterm (9600bd, 8 bits, 1 stopbit, no parity, hardware handshaking) and copying this string the machine worked! Next up: hpgl control from processing.

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February 12th, 2010 at 10:44 pm

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Nylon Extruder from soldering station

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Of course, the machine described in the previous post was never meant to have a sole purpose of pizza printing (which it admittedly does badly) but to become a repstrap machine so I can build a sweet Mendel. Next step after a cartesian robot is the plastic extruder. Although other people have tried to use a soldering iron (with limited success) we chose that approach nevertheless. Since isolated heating wire appears to be hard to come by (except for the makerbot store) and we had a spare soldering station lying around. Our first tests seem promising:

nokia2281 sany0016 nokia2306

Critical issues are the steep thermal decline you need from the guiding tube to the heated nozzle. As soon as you drop pressure in putting the nylon through, the plastic pops out on top of the heated nozzle. Next up are a guiding tube from peak (or perhaps some ceramic material) and the steppermotor drive for automatic feeding.

BTW.. the reason we use nylon, is that you can buy it in a normal DIY hardware store. It is normally used for pulling wires trough tubes or unblocking drainage. ABS wire is still pretty expensive everywhere, especially for this kind of testing you’re not going to buy 3 kg…

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February 9th, 2010 at 5:35 pm

Pizza Plotter

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Bringing personal fabrication to your kitchen: the pizza Plotter. During one of the last lectures I gave for Creative Technology about reprap‘s and personal fabrication one of the pizza hungry students (Symplexity) pointed out the necessary connection between pizza and production. Thus the idea for a Pizza Printer was born.

The previous posts on the Repstrap describe a 3D carthesian robot made from dot Matrix printer parts (using ONLY parts from three StarLC10 printers). Instead of the Z-axis the nozzle of a pressure plant mister was put on the head. The tank has been filled with tomato sauce. See the results on youtube below:

OK. admittedly, the accuracy needs some work. This has more to do with pressure / extrusion control than with the 2D robot. (which is basically an ordinary ottantotto controlled plotter now). The original StarLC10 power supply has been used, along with part of the casing. A standard RC servo has been added to the plant mister nozzle, allowing for on-off control for move- and draw commands. The ottantotto controls three stepper motors directly (using four wires per motor). The original stepper driver chips (STA401A) have been salvaged and re-used. For all the motors a single STA401 has been used. The control signals of both parallel motors have been bridged.

r0013730 r0013736 r0013731 r0013717 r0013733 r0013729

A drawing is made using a very simple processing sketch, based on the ‘file-save’ examples.

/**
* sketchtool, based on the 'filesave' example.
* move mouse. Every time you click, a datapoint will be saved
*/
int[] x = new int[0];
int[] y = new int[0];
void setup()
{
size(512, 512);
frameRate(30);
}
void draw()
{
background(204);
stroke(0);
noFill();
beginShape();
for (int i = 0; i < x.length; i++) {
vertex(x[i], y[i]);
}
endShape();
// Show the next segment to be added
if (x.length >= 1) {
stroke(255);
line(mouseX, mouseY, x[x.length-1], y[x.length-1]);
}
}
void mousePressed() { // Click to add a line segment
x = append(x, mouseX);
y = append(y, mouseY);
}
void keyPressed() { // Press a key to save the data
String[] lines = new String[x.length];
for (int i = 0; i < x.length; i++) {
lines[i] = x[i]*4 + "t" + y[i]*4;
}
saveStrings("positions.txt", lines);
exit(); // Stop the program
}

Tomato Sauce and Pressure Vats are a match made in white-wall hell. At least until I fully understood the merits of hose-clamps. Luckily, if you are quick enough, the stains wash off well.
r0013726

The printing program is equally simple (but will follow in a next post) The Ottantotto software has been made using winavr (since it involves timer interrupts, and I really love the AVRlib libraries from procryon)

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February 3rd, 2010 at 3:09 am

Posted in DIY,Robotics

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