Here are the first assembled parts!
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The box holds the LCD and UI electronics. The knob is also pressable, so it selects menu items, etc. The button is a "STOP!" emergency button.
The box an knob were downloaded from the fantastic website "Thingiverse"
http://www.thingiverse.comwhere you can find a gazillion 3D models for just about anything. These particular models are available in parametric OpenSCAD format. OpenSCAD is a sort of programming language for 3D solid geometry. Rather than playing with points in a 3D editor and moving those around to get the shapes I want, I just write a little OpenSCAD program to describe the shape. The program is then compiled into a shape/geometry file, which is then exported and printed.
For example (a simple one), to do the little blue insert on top of the knob, here's the actual OpenSCAD program...
- Code: Select all
cylinder(r=5,h=1);
Pretty straightforward, sure. But the nice thing is I have additive and differential geometrical capability. To take, for example, a square out of the middle of the cylinder, I could do this...
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difference() {
cylinder(r=5,h=1);
cube([3,3,3]);
}
A bit of overkill there, but I subtracted a 3mm cube from the middle of the cylinder. You can translate, scale, and rotate objects very easily, and you can parameterise things, so that by changing simple values at the start of your OpenSCAD program, you can change all sorts of things. The knob, for example, was downloaded from Thingiverse and I set some values to indicate the number of ridges, the height, the width of the skirting, the interior hole size and depth, the pointer size... and that was all I had to to do have a knob exactly the dimensions and shape that I needed. It's a lot of fun and VERY easy.
OK, so the blue box, as I said... that's the control panel. This will sit on the bench, front of the machine and attached to the frame. The LCD is a part of the "RAMPS 1.4" electronics package regularly used for 3D printer projects. These are stock standard and now very cheap. I am sourcing nearly all of my components from AliExpress
http://www.aliexpress.com which is a central place for buying from Chinese companies. They seem responsive and reliable so far. And very very cheap. The whole electronics shebang (RAMPS 1.4, Arduino, stepper motor drivers, LCD and assorted cabling) cost me just on US$30 including shipping.
The gadget in the front (the yellow thing) is a real Rube Goldberg contraption, and an absolute pleasure to put together and watch in operation. The yellow parts are printed in a material called ABS. This material has a higher temperature tolerance than the blue stuff, which is PLA. The long rod is in fact an allen key. Around the allen key are two springs from ballpoint pens. The brass thing holding the springs is from a euro-style terminal block. Up top, there is a safety pin which has been cut just so, and it's job is to push the allen key's bend onto a shelf when the whole thing is pushed upwards. When on the shelf, the safety pin/spring holds it there. Now here's how this thing works, and what it does. When the printer needs to perform Z-calibration (figuring out where the print bed is, and how flat it is), it 'deploys' this z-probe by moving the whole print head (the yelllow bit is a partially assemble print head; there's more to be attached) and swiping it along one of the drive belts in the machine, so that the top of the allen key catches and swings sidewards off the shelf holding it. The springs immediately pull it downwards, and the z-probe is deployed. Not added here yet is a microswitch which the allen key small end will engage when it drops down. The printer then proceeds to 'tap' the bottom of the z-probe around the print bed. When the z-probe touches the print bed, it pushes up the allen key a bit, which disengages the microswitch. Thus, the printer knows exactly the z-height of the print bed at each location. Finally, after a number of 'taps' around the printing area has extablished exactly the z-depth of the whole surface, the print head is pushed down, forcing the allen key right up past the safety pin/spring, which forces the top arm of the allen key sidewards back onto its little shelf once again. It's a real clever bit of homebrew engineering, and appears to work really well.
So, that's it for today. That print head has a lot of stuff to be added to it. There's the hot-head which does the actual printing, and the arms to attach to the carriages, which allow it to move around. But, this is a start... and it's a lot of fun so far. I'm waiting for quite a few parts from AliExpress, and as they come in I'll be building more.
For reference, the filament I'm using is 1.75mm diameter, and the resolution of the printer I'm using is 100 microns, with down to 50 microns claimed. Essentially, 20 steps/mm which is really quite accurate. Print speed is very very slow. Imagine building up an object with a cotton thread, going around and around laying the thread down to form your shape. It takes hours; the blue box you see in the picture took about 3 hours or so to print. It's fun to watch, though, and really quite clever.