Monday, June 28, 2010


New Release

I've just done a new RepRap release at Sourceforge. This will probably be superseded quite quickly (we are in the process of standardising the M Codes used to drive the machine, which won't take long).

The host software now runs an awful lot faster when it is slicing RFO files and STL files. This is because I removed something that, in my ignorance, I had thought would make it run faster, but which experimentation has now shown had the opposite effect: I had put a finalize() function in all the geometry classes. That seemed reasonable - give the garbage collector a bit of a hand to tidy things up. But what it actually does is to subvert the garbage collector and to put unreferenced memory into a queue for later removal; a queue that rarely - if ever - seems to get acted upon. If someone can explain why this is a good idea, I'd love to hear it.

Meanwhile, all the finalize() functions are gone, and the host software now runs pretty zippily... (It uses a lot less memory, too.)

The algorithm it uses to find outlines of slices has also been changed to Marching Squares, which seems both more reliable and faster.

The new software now also supports heated beds.


Monday, June 21, 2010


Vectorization of pixel defined print roads

In which your narrator describes the end, hopefully, of a search for a reasonable way of converting pixel-defined print roads calculated by Slice and Dice.

Do you want to read more?

Sunday, June 20, 2010


Yet another extruder nozzle...

The shortcomings of the standard RepRap extruder have been moaned about (with some justification) on the forums and elsewhere. The PTFE barrel is in tension with the full force of the driven filament. It expands when hot, altering the Z=0 point, and it has the brass extruder nozzle screwed into it; this can tend to come undone, plus the working pressure tends to force the extruded polymer down the thread making and enlarging a gap between the brass and the PTFE.

I have just designed a new one that attempts to combine the benefits of the original design, the very robust Bits from Bytes design, and a number of Nophead's ideas.

There is still a brass barrel and a PTFE insulator. But the PTFE screws inside the brass, so the internal pressure tends to seal the join, rather than opening it up. In addition, all the force is taken by a plate and two pieces of M4 threaded rod, rather than the PTFE. This means that the device keeps its Z=0 point. Not counting M4 nuts, it has six parts (there's a PEEK top-hat separator between the plate and the brass - you can see that in the top picture, but not in the exploded view).

Final advantages are that it's much easier to take apart and to put back together, and you don't have to wait for glue to set before using it.

All details will be here on the wiki soon.

Wednesday, June 16, 2010


Reprap Aggregation Pipe - V2 update

Hi All,
I just wanted to let you all know that the Reprap "Blog of Blogs" has just been upgraded to use the new Yahoo "V2" pipes technology! (today)

For those that live under a rock ( or are new) this is the URL for the meta-blog of around 100 reprap blogs:

..and this is a brief from Yahoo on the new technology, which went into BETA about a week ago.

Happy Blogging!


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Thursday, June 10, 2010


Inkjet RepRap

A while ago Amberish Jaipuria did some preliminary RepRap experiments with inkjets - details are here. And before he left, Ed was always saying, "I think inkjet is the way to go."

It would certainly be nice to be able to lay down waxes, resins, conducting ink and all the rest in a RepRap with the fineness and precision that inkjet could give. We would probably want to use Epson inkjets, which use piezoelectric mechanical pulses to eject the ink drops. All the other systems boil the ink by resistive heating in a tiny chamber to eject it. The piezoelectric systems will obviously be more tolerant of funny polymers and the like, which might not take kindly to being boiled.

Recently I have been looking at continuous ink systems. These replace the normal (and horribly expensive) inkjet cartridges with a tank-fed system that holds 100 ml or more. And they're cheap - the four above cost me £13 in total including postage from these people. You get the tanks, the feed tubes and the hacked recycled cartridges for that. I say hacked, because the cartridges are chipped to report emptiness to the printer - this is how the manufacturers try to prevent you doing re-fills. These report "full" all the time, I think.

Now, with an Epson, the piezoelectric heads are not in the cartridge (it's just an ink reservoir). They are built into the printer. There's a good article about all this by Tim Hunkin here. (Note especially the bit about Epson heads clogging if you leave them unused or let airlocks get in.)

So to the $64,000 question: I have done a good bit of searching for the electronic incantations that need to be sent to the piezoelectric heads taken out of an old Epson printer, and I have drawn a blank. What's needed is the Epson equivalent of this excellent HP Inkjet book by Matt Gililland. I could prod about in the printer with a scope, of course, but it would be nice to have something authoritative.

Does anyone know what pulse-timing patterns and voltages Epson piezoelectric heads need?


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