Saturday, August 28, 2010
Making a lid for a potentiometer mounting box
In which your narrator shows you a few tricks of the trade with thin-walled prints.
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Wednesday, August 25, 2010
Designing with a Reprap machine in the loop
In which your narrator celebrates a return to craftsmanship made possible with the addition of a Reprap printer into the design process.
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Tuesday, August 24, 2010
Darwin makes a Child Mendel Video
I've learned so much from the RepRap journey and I've been looking for a way to give back to the community for all that it has given me. I felt the best way to give back was to start videoing my progress from a Darwin RepStrap to a Mendel. Four months after I started filming I can finally share. I hope this video can be a tool for increasing the size of the community, and ultimately increase our momentum. We really are on the ground floor of a world changing technology!
selective laser sintering part 8: reciprocating laser cutter
On Saturday afternoons, like any good grad student, I visit my parents place to do my laundry. While it's spinning around, my dad and I usually get up to some neat projects, and this is what we worked on this week.
I've had an idea for a while that one might be able to build an inexpensive laser cutter using a 1 Watt IR laser diode, as opposed to the larger 20-100 Watt CO2 tubes traditionally in something like an Epilog laser cutter, using a bit of a trick. Traditionally laser cutters have a lot of power, and (to my knowledge) are generally fixed focus, meaning that the focal point -- the hottest portion of the cutting beam -- stays at a fixed depth relative to the material that you're cutting.
Because commercial laser cutters have so much raw power, it doesn't so much matter that they're slightly out of focus at the top and bottom of the material -- even diverged, the beam still has enough power to cut. This gave me the idea that if one could dynamically adjust the focus of the beam, starting at the top of the material and moving it progressively deeper for a given x/y point along the cut path, one might be able to steadily "bore" through the depth of the material by having the most powerful part of the beam moving through the depth of the material. The advantage to this would be that one would be able to potentially use a much less powerful laser diode, and it would be much less expensive than a traditional laser cutter -- but the cuts would take much longer to create. Given that even inexpensive laser cutters are traditionally out of reach of most hobbiests or folks in the reprap community, this seemed like a potentially handy enabling technology. Working on the Open SLS 3D printer project, I also had the idea that since you have the laser there anyway for creating 3D SLS prints, you might be able to use the exact same device without the powder chamber create 2D laser cut objects -- essentially having a hybrid printer capable of 3D prints, 2D cuts, and 2.5D laser cut 3D objects (and any combination thereof). That seemed like an extremely fruitful thing to pursue, so away we went.
The test rig is beautifully simple. Borrowing from an idea my friend Trevyn at the local hackerspace had about using CD/DVD drive head mechanisms as very small CNC axes, my dad and I took apart a bunch of old drives from our junk pile and found the three nicest axes of the bunch. We stripped them down, attached two together perpendicularly to create a 2 axis table, and attached a third axis orthogonal to the table as the Z (depth) axis. Overall, the travel on each axis is very short -- on the order of about 1.5 inches (3-4cm) each, but this is more than enough for experimentation. The entire 3-axis device is very small, and fits in the footprint of a DVD drive -- infact, many of the structural components from the drives were used in the construction of the structural parts of the mini CNC system.
The laser from the SLS project was attached to the vertical axis, and the steppers (which seem to be 5V) were attached to the dsPIC and stepper controller I built for the SLS powder test rig. I wrote some simple code to move the table in a square pattern around 1cm on a side, and reciprocate the laser up and down at each point on the square-shaped path.
I loaded some flat black plastic into the device (I only had the back of a CD case -- about 1mm thick, and I'm not sure what the material is), and gave it a shot. To my surprise, it worked! The process was a little slow (it was probably cutting at around one inch per minute), but it worked -- all without any adjustments or calibration, on the first try.
I need to find some thicker material to test, as well as different material. I'd like to try black acrylic sheets, as well as black ABS sheets, if I can find them. For fun I taped a few sheets of the CD-case together, and it seemed to cut through most of two of them, but I have a feeling that the speed and depth will have to be adjusted for each material type and thickness. Pragmatically, I think my "reciprocating laser cutter" technique will have some limitations, and perform better when the focal length of the laser is large, producing a narrow, sharp focus, and reducing the amount of material around the perimeter of the hole that the beam has to melt to get to the "sweet" spot of the new focus, although this effect may be somewhat mediated at least in part by moving more slowly and in smaller steps down through the material. Through experimentation, I would be happy if I could successfully cut through 3mm material, and very happy with 4.5mm material -- thicknesses that start to become structurally useful in terms of creating 2.5D objects (like my entirely laser-cut linear axis ).
As a side effect of the boring process, one appears to be able to control the depth of the material that's taken off -- such that you will likely be able to mill to a specific depth in addition to cutting or etching, by simply adjusting the depth that the reciprocation process stops at.
Thanks for reading! :)
[part 1] [part 2] [part 3] [part 4] [part 5] [part 6] [part 6 video] [part 7] [part 8] [cogsci.mcmaster.ca/~peter]
Make a minimalist Atmega 644p/1284p Based Micro-Controller
This project was inspired by the Arduino and the Sanguino but was primarily for use as a RepRap Controller and general purpose Amforth development board.
Wednesday, August 18, 2010
Right now the code's definitely not at it's prettiest but it'll slice pretty much any* .stl file, and the MeshMRI will give you a good idea as to why things are going screwy if you're not able to slice a file.
*as long as it's binary and not ASCII
Friday, August 13, 2010
RepRap @ FAB6 International Conference, Amsterdam
Next week, the Sixth International FabLab conference will be held. The theme is "Industrial (R)evolution":
This year’s theme is Industrial [r]Evolution through which we will explore the implications and consequences of personal digital fabrication for art, business, industry, culture and education. We are poised on the threshold of a new era, like that of the Industrial Revolution, emerging from access to low- cost, high-precision fabrication tools and powerful Internet-based communication capabilities which are changing the ways we think about and approach innovation, invention, intellectual property, creative processes, computation, manufacturing and distribution, business models, and social and cultural networks. In a world where anyone can access the tools to make or create almost anything, the possibilities are limitless. This is the Industrial [r]Evolution, a socioeconomic and technical [r]evolution from mechanical means of production to digital means of production and communication.
Obviously RepRap will be represented there. By Adrian (per video conference), Rhys and myself. Adrian will talk about the legal implications of affordable, widespread 3D printing capabilities, Rhys will talk about multi-material printing and other recent and future developments and my part will be about the enormous adoption rate and other interesting statistics derived from the RepRap Survey. This will include previously unreleased information, but I will publish it around the time of the talk. Given your enormous collective effort, you guys deserve to be among the first to get this data!
I must say that I'm also looking forward to the other talks in our Thursday session:
Ron Weiss (video): BioFAB
Adam Arkin (video): Programmed Assembly of Cellular Networks
Josepn Jackson (video): DIY Biology
Larry Sass: Instant Fab Lab
Vicente Guallart: FabLab House
Matthias Kohler: Digital Materiality
Dale Dougherty (video): Makers
Hod Lipson: Rapid Assemblers
Jonathan Ward: Additive Assembly of Functional Digital Materials
Bre Pettis (video): The Robot that Sharing Built
The full schedule can be found here. I will try to blogs about the other talks.
Saturday, August 07, 2010
It's certainly no SkeinForge killer at this phase, but I like to think that, written in Processing (which is crossplatform and basically Java), and starting from a pretty aggressively Object-oriented stance, it'll be much easier to maintain, branch, and improve upon than SkeinForge and perhaps in the end, even better.
As it stands there are two cases where I think it already beats SkeinForge:
* Meshes which are very large (SuperSkein is fairly fast even at 500k+ triangles)
* Meshes which are flagrantly non-manifold (such as just about any character design with an armature)
It can't do multiple shells yet, but some of the math groundwork is already put in. If anyone wants dev permissions just message me on GitHub and I'll add you.
Wednesday, August 04, 2010
Google's staged introduction of Google Wave killed it. It's useless as a communication tool unless you can involve the entire group of people you want to communicate with. But because (as usual) they were stingy with their invites, it wasn't possible to create a wave among your entire handbell choir, or boyscout troop, or 4-H club, or whatever. So nobody used it, and as the invites became more free, nobody was using Wave because Wave seemed useless.
Nothing wrong with Wave; everything wrong with people's perception of it.
Wave also needed to be integrated with other Google products, so that as your waves got updated, everything you visited in the Google universe should have had a link to Wave.
Monday, August 02, 2010
No more melting extruders: Removing PTFE from the hot end
Just a quick and very sleepy post before bed.
I have a confession. My extruder works far less often than it's in a melty state of not-workingness. And this makes me sad. And causes me to spend unneccessarily on PTFE barriers, which invariably melt due to being in contact with a 240°C heater barrel, causing the extruder to irreparably jam. This is just silly, and I decided that I needed a new hot-end extruder design if I was going to go more than a few weeks without a catastrophic extruder failure.
At first I had a look at the new design for the MK5 extruder, but it still uses PTFE (though I'm told not as a structural component), and it looks to contain far more custom machined parts and thus will likely be far more expensive. Being a graduate student, I decided to think cheap, and see what I could do with the parts I had. Recently, an all-steel hot end was put up on Thingiverse ( http://www.thingiverse.com/thing:3452 ) that looked very promising, but I didn't have much luck trying to drill a very accurate 3.2mm hole down the middle of an M6 steel bolt.
In the end, after some tinkering and chatting with my Dad, we settled on an all-metal hot end based on the parts that we had available. We used the existing MK4 hot end parts, and similar to lampmaker's all-steel hot end, we 1) reduced the nozzle to half height to reduce the length of the hot zone, and 2) added a thermal break in the brass heater barrel. We constructed some heat sink plates out of aluminum, and tapped these plates to M6 to encourage a good thermal contact between the barrel and the fins. A couple of small fans were also added, as in lampmaker's all-steel hot end design, to cool the fins.
Because the force of the fans was so great, and because this is new extruder was to be used on the simple and inexpensive acrylic makerbot-clone with a heated build table and chamber, we added in a small baffle to prevent the fans from cooling the print itself, and instead direct the air flow upwards.
We completed the design Saturday night, and so far after about 5 hours of printing, the hot end has performed virtually flawlessly. Because this design uses parts that people with already-clogged MK4 extruders will likely have on hand (except for the aluminum), and because you could conceivably make this with very simple tools, this design might be a great solution to either fix your currently broken hot end, or to experiment with an inexpensive, alternative hot-end design that you should be able to increase the temperature on to encourage a pretty good flow.
(click to enlarge)
happy tinkering! :) i hope this helps!
Anyone Got a Good Slice Organizer?
The code is (more or less) cleanly written but I've got a bug I'm having trouble tracking down, and I know for a fact Forrest Higgs has a slicer that solves this, but as far as I can tell he hasn't posted his code.
Basically, my sorting algorithm is orphaning edges, resulting in ugly jaggs around the perimeter near the end of each layer as the sorter picks up those last edges. Anyone have a better algorithm than the one I'm using?