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!

Update: Nothing has happened

Since my last post over a year ago (gasp!), nothing much has happened on my RepStrap. I got stuck at trying to mount the Z-axis threaded rod in such a way that it wouldn't just fall down, and then suddenly I got hired by Google and moved to München. Since I haven't had the opportunity to get all my stuff down, no further development has happened.

However, München does (now) have a maker group, FabLab München, of which I am planning to become a member once the last moving woes are over.

Motor testing (with several digressions)

I'm starting to collect motors and getting more ideas for what to do with them. Most of them I have no idea what the characteristics are, so I'll have to experiment with them. This page and this page gives some useful information on how to test unknown motors. Testing methods include turning the motors at known RPMs and measuring current/voltage and running the motors at known voltage and current while measuring RPMs. To measure RPMs, I would have to build a tachometer. There's an Arduino-based test at Instructables. Preferably one that gives a nice output, e.g. with 7-segment LCDs. I just happen to have a bunch of those lying around, so why not test them all?

This is how my projects typically progress, or rather digress.

On with the testing. A cute way of testing can be found on Instructables, using only components that I already have (yay electronics conspiracy!)...
Or so I thought. Turns out my big mess of resistors did not in fact contain the required one. Now, at least my resistors are sorted so I don't spend an hour every time I start a project finding out that I don't have the resistor (except I haven't labelled them all yet for lack of good label).

Actually, I didn't have the resistors. Instead, I just took a larger resistor onto my breadboard, gave 5 V through it, and tried all combinations until a light went on. From then on, it was easy enough to map out the segments. All but one worked nicely.

Problem now is that it would require 7 pins per display to run it, or a driver (e.g. 4511) to decode and latch them. I don't have enough pins to drive more than one, and I have no 4511. So I can't use that for a display. Instead, I'll just read output on the Arduino, adding a potientometer if needs be.

Fiddling around a bit, I now have a little board with a 220 ohm resistor going to a high-power LED that points at the light detector. There's a 1K ohm resistor on the other side of the reading wire. The analog reading with full light is 800ish, with light blocked it is 550ish. Enough difference that I can use it! That's enough for tonight, it's time to go to bed.

It moves!

Just got the pieces fitted together for the Z stage for the first time. It moves! It lives! Surprisingly, the stepper motor driver worked right off the bat, unlike the two previous ones, both of which needed some fiddling. Probably the better soldering iron is to blame.

One bolt is about a millimeter too long, I figure I can dremel it down. Bigger problem is that one of the two inner pieces that hold the rail on is so short it can flip to the wrong side, plus the nail is loose. It will have to be redone, and I'm not sure I have a proper piece of acrylics for it. Also am missing two tube flanges. Once that is done, I am ready to mount the first tool!

My tool mounting is with some tie-down strap I got for DKK 20. I have 2x4 long holes they go through (nicely unsharpened with dremel and sandpaper) and they can be used narrowly or widely as befits the tool. It looks primitive, but I think it's good for flexibility and pretty damn solid.

Progress in the 3rd dimension!

I have declared March to be "get the RepStrap running in 3D" month. With some help from Buro Detours, I have assembled the third stepper motor driver, and subsequently cut and drilled the pieces for the Z stage. It helps a lot to have a good hacksaw and a drill press, this one has gone a lot faster than the first two.

One difference between the Z stage and X/Y stages is that there is a plate under the rails that anything sticking too far down will hit. I had to change the spring-loaded wheel holders a bit to be as flat as possible, including cutting the bolts down to minimum size.

I should have a flange today or tomorrow so as to mount the whole thing together. The next interesting part is what to put on in order to hold a head, and how to avoid the whole movable part falling out when there is weight on it.

My first drawing is complete

In an act of utter self-glorification, I made the first thing to be written by the 2D repstrap be the first letter of my name (also, it was only orthogonal lines). After some as just unexplained problems with the Y stage refusing to start, and a slightly wobbly fastening of the Sharpie, it indeed made a letter L (in Blocky Outline 83 point or so). I have now successfully programmed and output something with my RepStrap! Woohoo!

The next thing should be a fractal. Just because.