Thursday, January 31, 2008


Checking out the stepper

I was able to establish the stepping sequence for the 15 degree, bipolar stepper with a 1.5 v battery. It is...

+ -
Black Brown
White Yellow
Brown Black
Yellow White

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Stepper motor arrives

I didn't expect the stepper motor till tomorrow. It arrived, however, with the noon post.

Turns out that they went from the old style system which was a geared stepper to the new style which is lead and cadmium free but which also is gearless. They are pretty sure that it has the same torque reading, but the can measurements are pretty much the same, so I'd take leave to suspect that that's not so.

I pulled out the digital multimeter and measured the phase resistance and got 27.3 Ω which is just about what it said in the catalog. It will be interesting to see what sort of torque and speed that this thing delivers. Stay tuned.

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Getting my ducks in a row

I finally made it down to Potter's Electronics and got everything I needed for making up Zach's stepper controller board except for the 2K trim pot and the 2 watt, 0.5 Ω resistor that, I think, is probably not needed in any case. I also picked up an entry level Weller soldering workstation to replace my dead and gone Radio Shack soldering iron and a set of American-made side cutters and needle-nosed pliers instead of the Swiss-made Radio Shack junk that I had.

I've noticed that Radio Shack equipment lasts about 6-18 months under regular use. That's great for the sometime hobbyist but a waste of time for the average committed Reprapper.

(Read the whole story)

Tuesday, January 29, 2008


Wielding or wrecking the soldering iron

I took a break this evening from programming a new variables selector routine and decided to put some components onto one of Zach's stepper boards. My old Radio Shack soldering iron is pretty much used up, but I cleaned the nasty old tip and fired it up.

I decided to do the Schottky diodes first and immediately ran into trouble. The ones that I have in stock are 1N5819's. They're rated at 1 amp and 40 volts and are ultra fast. When I got a look at Zach's board, however, I noticed that the board markings specified gargantuan UF5404's, which costs about the same but is rated at 3 amps and 400 volts. I guess that Zach is expecting some heavy duty back EMF off of those NEMA 23's that Darwin uses. Oddly, though, when I looked at the board's Master Bill of Materials the Schottky diodes specified there were SB360's, a Fairchild product also rated at 3 amps. I expect the BOM got written up after the board was designed and reflects a more readily available component or something of the sort. It's a little confusing at first glance, though.

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Getting on with steppers

I've been sorting through my parts inventory to see if I have everything that I need to make Zach's stepper board. Now that the L297's have arrived, I pretty much do. About the only thing that is outstanding is the little trim pot and the connectors. I'm going out to Potter's Electronics and Radio Shack this morning to see if I can score one of those. Otherwise it's back to Mouser.

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Saturday, January 26, 2008


Saturday morning ironies

As you know, I began to slow down on development work on Reprap last September and then stopped altogether in November. This was not a matter of lack of desire, but more one of having had my day job get the better of me. Since September the hours required by my day job begun to run 12-14 daily and for the past month or two began to hit sixteen with a requirement of waking up 2-3 times during the night to feed yet more data into my dual CPU Xeon workstation for analysis.

Recently, I started hitting some deadlines. I've made them and got a few days breathing space afterwards before something else came up. There was one just before Christmas that gave me a chance to think back over what I'd done with Tommelise. The major departure that Tommelise takes from the mainline Reprap effort lies in its use of shaft encoded DC motors. I've learned a lot about these systems, much of it frustrating.

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Tuesday, January 22, 2008


So Close!!!

Coming to the lab tonight, I decided to work on my McWire machine and get as much work as possible done on it. There were a few things that were not quite finished on it, so I set out to fix them. Here's what I did:

* Mounted extruder on Z axis. I mounted it wrong the first time (too high!) The second time, I mounted it on the bottom of the Z axis, but then the head of the extruder would hit the build platform at 0. I fixed this by lengthening the vertical pipe. Now I just adjust the build platform higher or lower depending on what I need. I also lengthened the pipe that extends the print head over the working area. Yay!

* I attempted to mount some vertical bearing arms - the ones that are supposed to keep the Z stage up against the rails. Mine werent long enough, so I resorted to what I've been doing for a while which is to keep the Z stage up against the rails with a strong rubber band. Works great!

* Got all the limit flags working. Now the machine homes every time. Pretty important, but it was also fairly easy. I'm happy with how things are working now.

* Routed all wires. Everything is nice and tidy now (well, almost.) All that is left is wiring up the extruder to the Arduino and getting the token ring network wired up. should be pretty easy.

I'm so excited... I think I'm literally one more afternoon in the lab away from printing! This will be awesome! Pics and video on first successful print!

Wednesday, January 16, 2008


LOM-fabbing with a CNC-repstrap

Hi all,

... i'll post some images of my first LOM-fabbing (LOM=Laminated-Object-Modelling/Manufacturing) with a CNC-repstrap and a minidrill.

As you can see, with this method it's no problem to make overhangs or complex geometries out from single prefabbed sheets:

Here is the reactivated CNC-system:

Outputting a single sheet - the software:

Outputting a single sheet - milling:

I'm waiting to by a 'serious' millhead, then i'll make some 'real' parts needed for going further with my tripod-repstrap and the dispenser-heads.

One of the next goals is a software or conversion for automated slicing the LOM-sheets from a STL-file, so it would be much easier to process ...

Here you can find the complete image-sequence in ZIP-archives ...


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Thursday, January 10, 2008



Thought it was time to put my cartesian contraption to the test. Downloaded the STL files from sourceforge and started plotting (not extruding) the corner bracket.

Instead of the extruder, I placed a holder on the carriage for a pen (see image left) and this way it should be possible to plot the lines and see how that goes.

I noticed a few things: first of all, sometimes the carriage moves back to it's home position, for no clear reason. In a way a good thing: this was the exact same point every time, so it is actually pretty accurate (see also the image below where the 4 lines cross)

The second thing I noticed is that my settings are not scaling correctly (the bracket is 44 mm, the plot measures 48) but that should be fairly simple to fix in the Host software settings. I also found that my carriages goes a bit up and down (in the Z direction, which is why the plier is placed on it, to keep the pen down on the paper) and this is due to some slack in the carriage and XY assembly, which could be harder to fix.

The end result, a "plot" of the corner bracket, is shown on the right.

All in all, I am a pretty excited! Next step is to get the extruder up and running again, and try some real printing.


Saturday, January 05, 2008


IKEA Modding

In my quest for simplicity I decided to build a RepStrap frame with only this hardware:
  • 8mm threaded rod (12x)
  • M8 nuts + washers (48x)
  • a log of wood
  • IKEA Observatör 70x70 cross-brace (5x) (1 £ / 1.90€ each)
I only used very few simple tools like screwdriver, drill, hacksaw and fierce determination ;-)

I went to the hardware store and bought _all_ the rods they had and some nuts & washers.

Once started, it all seemed fairly easy, except from the clumsy handling with the 100 cm rods that I was afraid to cut too early.
When the frame started to take the shape of a cube there was a frightening amount of wobble.

Then I finally used my swedish "secret weapon" because I was hoping it would make the wobble do away completely - and it did.

That beast is rigid as hell!

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