Calibration

Everything is wired up, I have a new powersupply, and I even remembered to give power to the heater (had forgotten that when building the shield). So now - calibrate!

First thing is the temperature sensor, arguably the most important part to calibrate. I just get a value from 0 to 1024, the meaning of which is mainly determined by the 1K resistor I put across the thermistor.

At first, the PWM is giving trouble, not heating. But measuring the stepper motor driver heatsinks is interesting: X is pretty cool (34º), Y is really hot (95º), Z is pretty hot (70º), and EX is medium (90º)

Turns out I had misread the wiring markings on the heater. Now it heats, but slowly when I pause the heating to do measurements. I should rather go for a number of specific readings and hold each of those for a while with a little hysteresis.

But first, I need to get the thermistor properly connected. The little wires next to the extruder are hard to get on a connector, so I soldered some larger wire on, and now at least it seems solid.

Looked a bit more at the little thermistor print board, and realized I only had the GND and 5V connections, where I should have GND, 5V and a measurement. Fixed that (with a fixed-mount measurement wire), and now I get reasonable temperature numbers.

Raised the Z stage to see if I could get better temperature measurements.

According to the hand-held thermometer, I have the following measurements:

55º at 680
64º at 800
75º at 890
90º at 900


At 900, the remaining plastic started flowing out - I don't think that happens at 90º.

When cooling down:

68º at 825

69º at 760

Putting it all together

Didn't get to run The Monster last night, but fixed a few more things with the Arduino "shield", added connectors for the optional wires, mounted the extruder holder, moved the extruder stepper motor driver to where it wouldn't hit the ball bearings, added connectors to the wires to the shield, replaced the Cat5 wire to the extruder stepper motor driver with a flat cable wired up similar to the others, but some more organised connectors on the temperature sensor mini-board, and put everything in place, arranging the wires so they shouldn't get in the way of anything. This weekend I will try to get it running, so I can have it ready to show off (read "use as a warning tale") at #MakeMunich.

Arduino "shield"

After getting the extruder stepper motor driver and temperature sensor set up, I found myself with a bird's nest of wires. Four 10-wire strips that split off, crossing and re-crossing, plus several more for the sensor, plus power and other bits and pieces. The wires plugged into to the Arduino were apt to fall out, even with a proper connector on them, and I didn't know if there were shorts in random places (at least nothing smokes). So I decided to make a little "shield" for the Arduino, putting proper plugs onto the 10-wire strips (except I managed to again order the wrong size from Eibtron, their pages are really confusing). This is how it turned out (people who care about the æstethics of electronics might want to avert their eyes):

4-stepper-motor-driver shield mounted on Arduino.

Rear side of shield, with the fixed connections done in wire. From left to right to top-right: Z, Y, X stages and Extruder. Ground goes around the left and along the bottom.

Two ends were deliberately left loose, so I can later plug them in where I want them, if it turns out I need to have min/max for the X/Y stages or be able to enable/disable more of the motors. I have hardwired (literally) enable/disable and min opto endstop for the Z stage, since it will be idle most of the time and need be able to position itself right over the plate.

The pins for the Arduino are now:

0. RX - used to program the Arduino.
1. TX - used to program the Arduino.
2. ExStep - Extruder Direction
3. ExDir - Extruder Step
4. XStep - X stage Step
5. XDir - X stage Direction
6. YStep - Y stage Step
7. YDir - Y stage Direction
8. ZStep - Z stage Step
9. ZDir - Z stage Direction
10. ZOff - Z stage Enable (off on high)
11. Heat - Heater on
12. ZMin - Z stage minimum opto endstop
13. GND

Finally got the right crimp header for the four control wires for the extruder stepper motor driver, and soldered them on. Happy to see that the crimp pins were properly Murphyized[1]. My notes on this blog came in handy here, as I didn't have to re-test what the ordering of the wires should be.

Also trimmed a bit of the extruder-holding plate (which is a pain, as that requires unmounting the extruder, which is fiddly to remount) so as to avoid yet another collision with the edge of the Z stage. *sigh*

Decided to desolder the connector to the v. 1.1 stepper motor driver I got from +Tim Hatch - I would rather have all four driver connectors be of the same kind.

It's fun to sit here and hack on my little project while three Ultimakers are running full tilt in the background. I realize my Monster will never be as speedy or probably even as stable, but it's mine.

For next time (tomorrow?): Bring new power supply of my own, buy crimp-on headers locally if possible, and bring/buy some 10-wire strip. Then I can redo the old driver and mount it all together!

[1] See http://en.wikipedia.org/wiki/Murphy's_law#Association_with_Murphy

Choppin' off bits

Went to FabLab today to make some further progress while it wasn't as full. I got the slice and notch off the Z axis plate I had planned, and set up a plate for the Z opto endstop. I also cut a new set of cardboard support pieces for holding up the Z rod, now specifically laser-cut to allow other pieces of the Z plate to go down far enough. This allows the extruder head to go all the way down to the printing surface, though there seemed to be some issues with the plate under the extruder hitting the bottom of the Z axis frame. I will have to check if that's just a misalignment of the Z opto endstop or if it's actually keeping the extruder head too high. If the latter, I will need to take that out and give it a slice.

After the various adjustments, including a few more spaces and better springs, the Z stage now works at about the same speed going up and down, which is nice. Unfortunately, my power supply is dead, so I should bring in some of the other ones I have at home.

No cool video today, sorry.

Notes from putting it all together

Wired up everything. Made a ground-rail with six plugs, just enough. Several things still use temporary cables. Had to chop off one of the Z stage opto pins to have room for the extruder stepper. Made the little board for the temperature measuring. Tested all four motors running at the same time, using the stepper library (which doesn't actually have opto endstop inputs). Tried lowering the Z stage to be in proper extrusion height, but found the back of the extruder mount hit the Z stage frame as well as the Z stage threaded rod support. Cut back the support (it's cardboard) and marked where to remove some aluminium from the frame.

Next time: Bring Dremel and dremel out two notches for the extruder mount.

Noticed that the Z stage goes much slower up than down. I should give it some oil and make sure the skate bearing at the bottom is as centered as possible. If that doesn't help, I may have a serious weight problem.

The wiring is still somewhat of a mess, and I had to remove the extruder stepper motor driver from where I had mounted it on the side of the extruder mount, as it was going to hit the bearings for the Z stage plate. Now it's just hanging loose on the back.

The opto endstops are in a somewhat sorry state. The Z bottom stop is not there, and the top one doesn't seem to work, plus it has nothing that moves into it. I should probably find a way to mount the lower one, since knowing when we're at the plate is more important.

When running the Z stage up and down, I noticed the power would go out after about 30 seconds. When I was doing the all-motors test, that didn't happen. So most likely one of the idle stepper motor drivers gets overheated. I may have to look into enable/disable toggling, at least for the Z stage when extruding (since then the X, Y and extruder stepper motors will be running much more than the Z). I could possibly remove the X and/or Y opto endstop, they don't have that much to do when I just start a print somewhere on the middle.

I might want to hook up something I can use to move X and Y manually.

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.