Open-Source to the rescue!

To build anything in a RepRap, you need to have a 3-D design, save it as a STL or triangle mesh file, and load it into the RepRap host software (or skeinforge).

To create these designs, RepRappers use different programs - Either an adapted 3-d modelling programs, originally used for animation (like Blender and Art of Illusion), or freeware versions of CAD software (like CoCreate). These solutions work, and work well, but each program has seperate advantages. I've been looking out for a 'better fit' - a CAD-style program, that supports building meshes and solids.

Make magazine today furnished me with a link to FreeCAD.

It's pretty slick - either I'm quite lucky, or it works quite well. Within a few minutes I was able to load it up, get started, create a small cube model, export it to an STL file and import it successfully into the RepRap Host software (not always an easy thing!).

OK, lets give it a real test...

Let's load up some data from a complex file: a human head.
To really test it, I created a large sphere, stuck it on top, and did a 'union' (Join).
This is not nice: most complex geometries cause all sorts of bent and broken and backwards triangles. Lucky there is an analysis tool to point all this out:

From FreeCAD

Pressing some of the 'repair' buttons sorted all this out.

From FreeCAD

This exported easily to an STL file: and then loaded straight into the host software.

From FreeCAD

It started to slice and print to gcode : it got to 55 layers through before I got bored and turned it off.

FreeCAD is currently alpha software so far, but certainly one to watch!

One step forwards

G'day all.

I've been quiet recently - I had packed everything away into the garage as we were planning to move. Plans change, we're now not moving so I unpacked the RepRap and fired it up.

From ResistorHeater

First problem : blocked nozzle, due to a broken thermistor - overheated - and set the ABS solid.
Cleared down and drilled it out.

I replaced the thermistor with a spare 100k makerbot one - my last spare.

Interestingly enough, I soldered in a 100k thermistor from Maplins into a spare circuit, connected it up, and the temp read about 20C at room temp, and 34C while holding it - pretty good without any change in configuration. It might be a suitable replacement for the 'official' ones.

Replacement thermistor in, I warmed up the heater and 'let rip'

From ResistorHeater

It works! Extrusion is pretty slow (232mm/sec) and wide (nearly 1mm diameter through a 0.8mm nozzle) but it comes out reliably and pretty consistently. Temp was about 225C and power (screw thread/servo) at 180/255.

Now I have something working, I can refine the nozzle size ( I should be able to get some 0.6mm B&Q nozzles) and the original BfB 0.4mm nozzle, plus I have some small drills.

I now need to get my settings and speeds right in the host software - my current version is months old, maybe I should update. I've been thinking about upgrading to version 3 electronics, too, but with the excellent Mendel design out with a much smaller footprint, I quite fancy that. It might be time to build a Mendel using my Darwin....
:-)

Balls to the rescue

Since I disassembled my MyVu Solo glasses, I've been looking for some optics to enlarge the image to a useful size. The stripped displays are only a few mm square.

From MyVu

I thought about trying a jeweller's magnifying loupe (the thing they use to look at gemstones), but they looked a bit heavy.

What I really need is some kind of curved mirror. After looking up in wikipedia, I reckon I needed a short section of concave curved mirror with a focal length of only a few cm. OK, where the hell do you get one of those?
Well, if you extend a curved mirror, you end up with a sphere. So, a mirrored sphere - a few cm across? Well, your local christmas shop!

From HMD

To cut a small square section, take a diamond-coated file and gently score the lines you want to cut....

From HMD

Or just explode it in you hands, like I did.
Taking a couple of the larger sections, the internal surface is pretty much mirrored. Too far away, and there is no image:

From HMD

But, at just over half the radius away:

From HMD

An enlarged, reflected image is formed. Since the glasses originally had plane reflectors in, I think it probably won't even need reversing - now to mount them in a test pair of glasses.

NOTE : safety warnings apply - don't play about with razor-sharp wafer-thin slivers of glass near your eyes. Like I am. If I stick glass in my eye it's my own stupid fault. Don't try this at home.

Laser Scanner

Not strictly RepRap related, but I've been playing with the David Laserscanner software from www.david-laserscanner.com/.

It does seem pretty useful for generating source data. If it's good enough, you can scan an item, tidy up the data a bit, then print it put on your RepRap. The system then becomes a 3-d copier.

So, is it up to the task?

Initial setup:
You need a webcam, a laser line (either a laser level or a laser pointer), and the software.

I used an old webcam (640x480), and a red laser pointer (5mW) from ThinkGeek - but they're pretty readily available.

The software comes with a few different templates - basically a dot pattern you print out. You then attach the pattern to two sides of a 90 degree corner - like the inside of a box, or two card sheets at right-angles.

From laserscanner

You then point the webcam at the box, and 'paint' it with the laser line. The webcam can see the shadow of the line on the object and the background, and can work out the 3-d profile of the object.

To turn a laser pointer into a line, you need to bounce it off a curved surface (I made a line with a shiny metal knife handle), or shine through a glass cylinder. Wandering around Bath, I care across a shop selling christmas decorations - and they had a nice glass raindrop - shape:

From laserscanner

Shining the laser through the glass cylinder produces a nice line:

From laserscanner

I snapped off a short section of the glass and polymorphed it to the front of the laser. I've now got a simple laser line.
Initial playing with the software gives an idea of the result - I think it needs a bit of careful configuration to get the best scans out of it, but the potential is definitely there.

From laserscanner

Quick-release extruder

I pulled out my reprap at the weekend and fired it up. After levelling the bed, checking calibration, and fixing the z-flag that was loose, I started the extruder....

Nothing came out.

After some fiddling, I disassembled and reassembled the heater/nozzle - it was fill of brown/grey ABS, absolutely rock-solid, and had to be drilled out.

Since this is about the 50th time I have disassembled/reassembled my heater/nozzle assembly, I tried a modification to make it easier to change. My PEEK insulator is bolted to a penny washer with an m8 thread and two half-nuts.

From quickrelease

I cut a slot in the penny washer and I can now loosen a bolt and slide the extruder barrel/heater out to change it.

From quickrelease

This came in really handy, because as I restarted, warmed up to 225C, and fed the ABS through - it stuck fast. At least I could disassemble to find the problem.

The ABS appears to form a solid plug of the brown overheat mess as soon as it hits the heater, going solid and blocking the tube.

I think I've got a broken thermistor, or maybe the heat transfer is bad. It seems to warm up as expected, and reports the right temp (ish) staring about 16C and rising to 225C - fluctuating about 223-226C, but the ABS is definitely overheating.

I'll swop it out with another one and see if that helps.

MyVu Solo displays

Here's the photo of the bits remaining after breaking up the glasses:

From MyVu

The remaining useful pieces are two microdisplays with controller: one and one half-optics sets (I cracked one mirror).

From MyVu

I'd sliced the cable between the two PCBs during disassembly and found that they don't turn on if the second display is not connected, even with a bit of fiddling. Trying to strip the FFC (Flat Flexible Cable) to try and reattach it just didn't work - the connectors are about 0.2mm wide at that point and I just cut more and more off.

From MyVu

Farnell came to the rescue: A 20-way 0.5mm pitch FFC (A to A) for £1.54 did the job just as well. I plugged it in to both displays and they're both up and running.
Here's a mini southpark episode:

From MyVu

Now all I need are some glasses and some magnifying lenses....

Jiu-jitsu - 1930's style

The coolest kung-fu video I've seen for a long time!

http://www.youtube.com/watch?v=wmP1uKOVTr4

:-)