UV 3D printers

+Roland Mieslinger pointed me at this: Resin-based photographic 3D printers.

DLP 3D printer: http://b9creator.com/
Resin: http://spotamaterials.com
DIY versions: https://www.google.de/search?q=diy+dlp
Sedgwick: $500 + projector http://sedgwick3d.com/

Resin costs about $100/kg, as compared to about $20/kg for filament.

Something to note for the future. Getting rid of the X-Y movement would indeed be nice.

We have extrusion! I repeat, we have extrusion!

Spent several hours at FabLab setting up and testing my extruder head. (during Open FabLab, so I got to explain it over and over again, in German). And I got it to work, temperature sensing, stepper motor and all. Even though I had to make the temperature sensing by hooking up a resistor and a capacitor by wires. It works, dammit!

Here's a video overview of the setup (sorry about the noise, it was Open FabLab at the same time):

Ran it three times (until I ran out of filament) running the motor when lower than 30, and stopping the heating when it got down to 20. This made some rather random structures - I found I could make wavy things by moving the structure by hand.

And heeere, ladies and gentlemen, are the amazing first three extrusions from The Monster (or the head of it, at least):

The first two were just left alone, but for the third one I started to move it around to get it from clumping up at the nozzle. I found that by moving it about a centimeter at a time, I could make little waves of plastic. Maybe it'll be the next art form?

Notes to self

Stepper motor wiring (http://reprap.org/wiki/StepperMotor#Shortcut_for_finding_the_proper_wiring_sequence)

With stepper pin 9, dir pin 8:
Attempt 1: Left to right: Green, black, blue, red. Stepper motor moves erratically

Attempt 2: Left to right: Green, black, red, blue. Stepper motor moves erratically

Attempt 3: Left to right: Green, red, black, blue. Stepper motor does not move.

Swapping dir and step pins, reattaching GND.

Attempt 4: Left to right: Green, black, red, blue. Stepper motor moves forwards.

As expected, had to add washers under the extruder to make space for the wheel. I might want to laser out a hole later instead, as the washers make the setup less stable.

Couldn't see which way the filament was going. Put on a bit of masking tape, turns out stepping negative was dragging it in.

Reversing them all:
Right to left (when looking at the edge of the board): Green, black, red, blue.

Hooking up the heater as well (yellow is signal, black is ground), but the PWM does not seem to react at all. After standing still for a while, the extruder stepper starts to move on its own! Probably overheating, need big-ass heatsink.

Placed a fan right over the transistor, helps enough that it can move when it needs to.

Needed to get a temperature reading. Using the schematics of http://reprap.org/wiki/Temperature_Sensor_2_0, I hacked together the resistor (4.7k)  and capacitor (10uF) with cables. It didn't explode, and I got a temperature rating going from ~900 when cool down to 14 at the warmest. 14 seems to be hot enough that the plastic starts to burn, according to my nose.

For next time

• Build a small board to hold the temperature metering stuff. 
• Order the right connectors for the stepper motor driver and wire them properly. 
• Make wires for the temperature metering. 
• Decide on a distribution of the available pins (I think I'm running out of digital outs, but could hack an analog out, I suppose). 
• Need a ground bar, as there are 5 things that need ground. 
• Get a biiig cooler fin for the last stepper motor.

Extruder heating

I got the missing pieces for a PWM driver from Balzer Elektronik and Holzinger (for the power connector), and soldered it all up. Two of the three PWM outputs don't work, but since I only need one, I don't really care. I don't know why it's made with three outputs -- maybe just because they can. I got it hooked up to the extruder and powered it up... and it heats! Trying to measure the temperature with the Arduino failed, it looks like I need a separate resistor in serial and measuring in the middle (the thermistor is 100K but goes down to about 1k or less when it's warm). I guesstimate that the extra resistor should be about the minimum value that the thermistor gets to, since that's where I'll need the most precision.


The photo shows the heater part with the PWM connectors (red and black) attached to the heater wires, and two multimeter cables (red and green) connected to the two thermistor outputs behind the plastic. Orientation seems immaterial for both connections. My biggest random problem here has been poor connections to the Arduino. I need to find a better connector than where I solder a multi-threaded wire to a little metal pin and put heat-shrink over it.

Roadblock overcome

The Monster has been resting for several months due to the (really rather trivial) problem mentioned in the previous post. I didn't want to start over with the new electronics, and had a frustrating time getting the things for the 2.3 board. Eventually, I got some old drivers (v 1.1!) from a fellow Googler (thanks, Tim!). Next Monday, I try running it!

A brief update on my RepStrap (now affectionally nick-named 'The Monster')

After getting all three axes to work, I decided making an extruder from ground-up would be an exercise in frustration and likely get me to never finish. So I purchased a Wade's Extruder - and realized I still needed a stepper motor driver for it.

While I have some stepper motor driver boards, they are of version 2.3, which are surface-mount and not something I've ever tried before.  I've been scared off a little by that, and by figuring out which exact components to get - the lists from the original description are gone (this is why you don't just link to some random other place, but copy it in). So it's slow going at the moment, but then, it's a nice summer right now.

I should also make some proper tags for the opto-endstops with better fastening. The cardboard ones I made got all broken by me fiddling around with other stuff. Not good enough.

It moves - in 3D

 I now have movement in all three directions at the same time, after some futzing with the Z axis.  Here is proof:

The noise in the background is the lasercutter.  You can faintly hear the motor noise if you know what to listen for.

TODO:
Find, test, fix and mount opto endstops.
Talk to Dieter about right screw for extruder.
Or go to RepRapSource.de/RepRap-Fab.org and buy a full extruder for ~€75 (without motor).
Mount extruder and go! :)

A new life in a new land

When last we heard from our intrepid robot, all three stages were almost built. Only the right way to keep the Z-stage from falling was missing, but a move had interrupted further building. Since then, another move has occurred, but things are now calmed down enough that I have been able to join FabLab München, the local maker group.

They have taken me and my robot in and kindly lent me the bits and pieces I hadn't brought over yet. The drivers have been re-tested and now all work.  The threaded rods have been oiled (this helped the X-stage quite a bit), and a solution for the dropping Z-stage has been found: Place a ball bearing on a block underneath, so it is supported without getting extra resistance. This has been implemented (with several layers of cardboard:), and the last few kinks of the Z-stage are being worked out, mainly bolts that are too long.

I have decided to not go the purist way and rather have the extruder head printed on one of the other machines (if they work by then). Especially since there's hardly any designs for non-printed extruder heads out there. Maybe, once all the other problems are worked out, and I know a little more, I will go back and make it pure. Maybe.

In the meanwhile, it has so happened that I have inherited a broken MakerBot. Some of the electronics smoked, and we're not sure which. Since the owner has moved on to other robots, he's happy to let me try to fix it and get it running. Sweet!