Sunday, February 28, 2010


Slice and Dice 0.1

Last month, Adrian incorporated some ideas for using pixel maps that I'd used years ago with Tommelise 1.0 into what I understand is his most current version of the Reprap host software. At the time I was happy that my approach had proved to be of use to him.  I was, however, happily using Skeinforge with my Rapman printer at that time and didn't think too much about it.

Enrique's Skeinforge is a brilliant piece of software for non-mainstream Reprap printers like my Rapman.  As is my wont, however, I tend to test the envelope with just about any piece of hardware or software that I undertake to use.  The problem with testing the envelope is that too often you push right through it.  That happened to me when I started trying to print light, open structures like this.

Enrique invariably handles error notifications within a day or two.  I frankly don't know how he manages.  It must require superhuman capabilities for one person to manage that for so many users.  What I was trying to do, however, wasn't eliciting what could be termed an error as such.  The individual slices for what I wanted to print were quite small.  As a practical matter, what that means is that is that the layers tend to overheat from the extruder tip being over them too long on average.  Let that go on long enough and you wind up with a print that looks like a melted candle.  

Skeinforge has a "cooling option".  What it does is time how long you are spending printing a layer and if it falls below your set point it orbits the extruder tip around the print till it has a chance to cool off.  Thanks to the tendency of extruder tips to dribble ever so slightly, if you use this option your print becomes wrapped in what looks like plastic cotton candy.  It is a bear to clean parts wrapped up like this.  The other way that I developed when printing small pinion gears was simply to print 6-8 of the same thing at once, something that Skeinforge lets you do very easily.  While that is very handy if you need a lot of a thing, if you're just trying to develop a part you take 6-8 times longer to print your part and find the errors in the design.  With ABS costing $10/lb using Skeinforge's multiply option is not a very practical as a cooling method.

I finally came to the conclusion that Skeinforge, as it presently is written, wasn't going to take me where I wanted to go.  I had ordered a copy of the new Netfabb programme to do the same thing, then learned that their product rollout was going to be at least a month late {1 March}.

With several weeks of time on my hands, I decided to dust off my old Slice and Dice software and see if I could knock it into shape to do what I wanted.  Three weeks later, it's running.

Let me tell you from the beginning that Slice and Dice 0.1 is most definitely NOT an alternative to Skeinforge, Netfabb or the Reprap Host software.  If you are thinking that, forget it.  Now I'm not trying to keep anything proprietary.  If you want the source, I will give it to you under a BSD-type license which lets you do pretty much anything you want with it.  Indeed, I've handed out several copies already to a few reprappers who wanted a look at this or that bit of the code.

Before you decide you want it anyway, however, here are some facts about it that you should be aware of.
I've put Slice and Dice 0.1 together for one specific reason.  That is to let me try out off-the-wall 3D printing ideas that often times will go beyond the capabilities of ordinary software.  Most importantly, its a piece of software that I've written and can easily dive into myself and fiddle with to make it do new things without having to report problems to and make requests from others.  I figure it will save me a lot of development time by shortening the development cycle.  It for sure will keep me from making a pest of myself making requests for changes in their code to Adrian and Enrique.  That should be good for everybody's nerves.

This posting is also posted at my own blog, Diary of a Technocratic Anarchist.  If you are interested in following the progression of blog entries leading up to this posting they can be found in the February entries to my blog.  That's pretty much what I've been doing during the last month.

Saturday, February 27, 2010


Drilling the extruder barrel

Having had a lot of fun with the Afghan Lathe - which is still fantastic for machining extruder nozzles out of dome nuts - I've found that using a drill press the wrong way round is a lot easier for central 3mm bores in the extruder. Apologies for the cross-post, but people seem to have found it very useful elsewhere:

I'll still be working on the brass tube extruder, but I'm going to get a few Mendels working first, with technology I know is reliable.

Vik :v)

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Thursday, February 25, 2010


The Balls Return

Well, guess what? Supplies of suitable belt in New Zealand have completely failed to materialise. This comes as no great surprise to me, but must typify the situation in developing parts of the world. So, I am going to do a beaded belt (aka ball-chain or bath-chain) version of Mendel, using no fancy belts at all. The only problem is that the X & Y gears need to be very small to have enough resolution.

Well, the improved stepper drivers we're using have a slightly higher resolution than the old ones - not as high as the 16 micro-steps or more claimed by the chip specs, but useful. Also my printing skills have improved. This means that it may be possible to match a slightly larger chain with a slightly larger printed drive gear and better 0.1mm accuracy.

If that fails, it's time to break out the frickin' big "laser" ...

To the workshop!

Vik :v)

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Monday, February 22, 2010


Broadening RepRap Participation

As most of you know, RepRap's software and hardware files are currently hosted on Sourceforge using Subversion. This works fine from a technology perspective, but is not ideal from the point of view of those members of our wider community who want to contribute. In particular, it is difficult to branch the repository in a way that allows core developers only to have write-access to the 'official' stuff, but allows anyone to create branches that can subsequently easily be re-merged.

So, after considering lots of alternatives such as Git, we are thinking (and only thinking at the moment) of moving to Launchpad using Bazaar. This would allow anyone to create branches, to post patches, and so on in a way that could be merged with the official read-only trunk.

There are three equal parts of a RepRap: mechanics, electronics and software. It is particularly important that any system we choose should be as easy to use as possible for electronics and mechanics contributors. This is not to say we value software any the less - on the contrary. It's just that software people will cope well with whatever we choose. So bear that point in mind if you have views.

Speaking of views, before we do anything in this direction, we want yours. Do hit the comment link:

Tuesday, February 16, 2010


RepRapping at the Maker Faire, Newcastle - March 13-14, 2010

RepRap will be attending the 2010 Maker Fair in NEWCASTLE, UK

For more details:
Forum Announcement
Maker Faire Announcement

Also, I am pleased to remind you UK RepRappers out there that we have a United Kingdom RepRap User Group.

For everyone else in the world, please check the list of all RepRap User Groups. (These are good places to get or Mendel parts.) See also our Forum for Selling Mendel Parts.

Lastly, if you're planning on building a RepRap, or want to help other people build them, and you don't have a RUG nearby, you are welcome and highly encouraged to Start One! (Please note: World_Domination is not part of official or unofficial policy.)

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Wednesday, February 10, 2010


Full Colour RepRap?

This is an idea that Erik, Batist and I had at FOSDEM.

Both Erik and Ed have now got Ed's Bowden extruder idea working, and Vik has now got a really simple, really slim extruder heater design.

So it ought to be possible to arrange three of Vik's brass tubes in a cluster at 120o to each other with a single heater and thermistor, and to splay out the top ends slightly to interface with three Bowden tubes. If the bottom ends came together in a small manifold block with a single nozzle, and you were to put red, yellow, and blue filament down the three tubes, it should be possible to get the three steppers to mix any proportions to give you any colour you want, I think.

The trick, of course, will be to have the fine nozzle as short as possible, and the mixing happening at the last moment in it.

The flow is very viscous, and so Reynold's number is very low. This means laminar rather than turbulent flow, and therefore maybe streaking rather than mixing. But if the head were to twist back and forth, that might fix that problem.

Wednesday, February 03, 2010


Mini Me

Just before he left to Starve in the New Zealand Wilderness Ed did a new RepRap design because he "had to get it out of his head". It was a mini version of Mendel. You can see it on the left in the picture above - a still from
Josef Davies-Coates' short documentary on the Bath RepRap Lab. The machine uses M6 threaded rods and M3 nuts and bolts (as opposed to the M8/M4 used on Mendel) and NEMA 14 steppers. The reprapped parts are about 30% of the volume of those for Mendel, which is to say it could reproduce three times faster.

This is a completely unsupported design for the moment (we haven't got the time...) but we have put the STEP file for it in the RepRap repository at

because it's so neat, and some of you might like to play with it...

Here's a close up rendered by M.BrittCrane:


On reflection, I think that putting the material spool underneath is not a good idea: it tends to jam. Better to have it on a separate reel above (which would make the machine even smaller).


Tuesday, February 02, 2010


Multiple object saving and loading

I have done an implementation of .rfo files (see in the Java host code. These allow you to load up a set of STLs, then save the whole lot as an .rfo file for re-loading later.

It's a bit experimental, and I need to fix it so that you can load-rfo, edit, then re-save. But if you want to play it's in the repository at

Monday, February 01, 2010


Brass Tube Extruder Update

Managed to blow the 4.7 Ohm filament at around 200C. By this time the wires were red hot, and a weak spot blew under the Kapton dammit. No matter, I have a New and Improved 6 Ohm version, all-ceramic insulation with double-twisted nichrome on the inputs to ensure a lower temperature on the input lines. I think it is those local hotspots that cause the Kapton to decompose. But hopefully I've just eliminated the Kapton - for the barrel insulation anyway; I might still use it to attach the thermocouple to the barrel for the moment.

Vik :v)

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