Erik's Blog: Discussing IT, personal fabrication and a new and better world

"If I can build a RepRap Darwin, I can build almost any machine."

-- Me

Because of the experience I got from it, and because of the fabrication possibilities it creates. This was one reason for me to start this project. There are many more, but I wish to share results, not philosophy (at least not now). Ten days ago I had completed the build of the machine. This was proof-of-concept 'working', but the prints were of mediocre quality (nothing was configured or calibrated yet). Now I'm able to print functional parts for more machines! (And I even had other things to do!)

First functional printed part!

Printed the optoswitch bracket as end-stop for the Z-axis.

The part required some cutting and a drill to make the holes (for the screw) that should have been there. Right now, where my RepRap attempts to print a hole (nothing should be there) it prints more than anywhere else: a complete fill with plastic. This is because the outline is really thick and because of the curvature takes longer to process than a straight line. I thought that AngleSpeedFactor might need to be lower, but this didn't change it much (yet).

I'm printing in HDPE, and through the time lapses I made you can clearly see the material shrink causing the warping. If this happens a lot, the object will detach, even with my sandpaper-hairspray combination to adjust the stickiness. Also in this video, you'll see that the X opto flag is perhaps too thin to print? It doesn't attempt to print a layer that is too thin? Any ideas? The part was not designed to be printed on its side, which it could be (as a work-around).

I like my own time lapse video's of the RepRap 3D printer build but that's documentation. This guy makes a real art of it (well, actually he reversed some video's, ahh well) and uses it in a very slick way:

That's too bad. I thought I was almost done.

With the 100nF capacitor it worked better. Now I still have the problem that it more or less stops heating in cycles when the power setting is very high.

Perhaps I'm printing with a bit of a difficult material (HDPE). I need pretty high temperatures, otherwise either the PTFE rod is pushed out of the clamp or the motor hardly rotates or the screw doesn't grab the fillament well enough to push it through.

Update: This happened twice now, now I've fixed it with steel wire that I've twisted to tighten it around the fillament/screw holder and a newly installed hose-clamp.

When I use the nozzle wipe function in the 0.8.3 host software I got a weird appendix to my objects:
[attachment 755 Appendix.jpg]

Weird appendices when I have the nozzle wipe on...

This (see photo on the right) happens after returning from the nozzle wipe, just before the first outline. When it starts with the outline, it starts at a slightly off position at first. For different layers, the time to restore takes a different time (not with the objects in this photo, but I've seen it). At first I thought it was a communications error, because of the previous, but when I changed the NozzleWipeStroke to 0 (it was 15) the odd behaviour was gone. This was also key to my first nearly-water-tight mini-mug. I had a quick toast because the contents were leaking out very slowly, but it was very good. Here I am, proud of this result!

First sip, a nice Bacardi shot.

The 3D printed mini mug.stl!

Here's the time lapse of how I made it:

One more thing: I extrude on plain MDF and use hair spray and sandpaper the adjust the stickyness. This works really well! The hair spray reduces stickyness (and so do previous prints) but sanding down a bit will increase the stickyness. As you'll see in the print is that it lets go at the last few layers, the print is good enough to toast on

I like new computer interfaces. It's amazing that the Wii is allowing many people to make their own creative hacks that are actually quite powerful.

Wii finger tracking

3D tracking

I can imagine that this principle one day would also allow you to make/design physical objects just by waving your hands. At least it allows for nice augmented reality and human interfaces for CAD.

There's also the Wii nunchuck interface to arduino:

More progress, more videos!

I had a lot of time on my hands this week, so I almost finished my RepRap! Here are some time lapse videos.

Gaining height: part 1 (40 minutes of work)

This video shows the first steps to adding a Z direction (up) on the
X-Y frame. On one of the axes is the motor that rotates a threaded rod
that is synchronized with three more threaded rods. A MDF base plate
lies on 4 nuts that rest on this threaded rod. This is the Z axis.

Gaining height: part 2 + 3 (15 + 45 minutes)

The moulded parts that I got from bits from bytes had a lot of holes that were note completely through. They had to be drilled through. I didn't drill the holes exactly vertical. Looking back, this was the cause of a lot of problems and alignment issues later on. It really illustrates the power of additive fabrication ("fabbing"): you do not need to drill holes if they're nicely designed in. When you start drilling your own holes, it becomes obvious how imprecise human hands are compared to fabbing.

Attaching the Base diagonals

These diagonals greatly strengthen the structure. The can also be used to attach parts to and guide wiring. I put some nuts on the base diagonals so I could glue them to the ATX (computer standard) PSU (power supply). This makes the entire RepRap 3D printer a compact machine of 0.5x0.5x0.7 (width x depth x height) meters.



I used simple M5 bolts instead of grub/set screws since I had a lot of them and it actually looks nice to have lots of bits in either black or metalic

Building the extruder

Here I'm building the extruder. It seemed that the motor coupling (from the GM3 motor to the flexible drive) was to thick. The motor didn't fit on top of it. That was mostly because the flex drive ended up a little higher because of how I soldered it to the screw that screws in the plastic fillament. I tried making it a bit shorter with a knife, but that would take too long I realized soon, so I added some rings between the motor and where it is normally attached to distance it a bit.

Attaching the screws to the extruder:

Current state of afairs

The only problem left is that I sometimes get communications errors and that the extruder doesn't heat up (you can still touch it). The thermistor gives a value of 67' Celsius (which seems about right). Holding the soldering iron against the extruder head heats it up and it indeed registers a higher temperature as it should. So it's not the 10K thermistor / Analog2digital measurement problem (yet?)