nophead Wrote: ------------------------------------------------------- > I think we have to aim for BGA and QFN because > that is the way the market is rapidly going. And the only reason to pursue this in the context of reprap is planning for the future. I do disagree, though, unless we're building something outside the realm of microcontrollers, QFP has a lot of life left in it.by Annirak - Controllers
Does anyone know how much axial force a skate bearing can withstand?by Annirak - Mechanics
I am not sure that pick/place is absolutely necessary unless we're doing large runs. I think that it's more important to get paste printing in place. I'm not sure whether oven or heat wand is the way to go for soldering.by Annirak - General
degroof Wrote: ------------------------------------------------------- > A couple of random thoughts: > > 1. The auger designs I've seen have had the auger > extend into the heated zone. Since the auger tends > to conduct heat, the thermal break is compromised. > What would happen if the auger stopped on the cool > side of the thermal break? Would it still be able > to puby Annirak - Mechanics
Well, I have the sensor wired up. Reading it was really straight forward. I will post code in the next few days for anyone who wants it. I definitely think that this should be our next-get thermocouple sensor. It's far cheaper than a AD595, it's easy to use, and it's scalable. We can use as many of them as we have slave-select I/O pins. Brendanby Annirak - Controllers
Thanks for the link, Forrest. Do you know whether this is a global polymer property or whether it is specific to the class of materials that they ran the test with?by Annirak - Mechanics
Nophead, I think that static heads or z-axis heads have a lot to recommend them. If for no other reason than that they make head-exchange really simple: you just move the table under the next head. There are two problems, though. The footprint of a static-head rapid prototyper is a fair bit bigger than the reprap. There is a limit to how many g's you can give the table before finer designs stby Annirak - Mechanics
Does plastic degrade with repeated meltings? How do conductive polymers respond to being melted repeatedly? I don't know the answers to these questions, but I think they're important to consider. Right now, I just need to extrude granules so that I can test conductive polymers in real applications. Once I have done those tests, I'll look at retooling for filament production.by Annirak - Mechanics
bobt Wrote: ------------------------------------------------------- > It appears that Zach may have fixed the problem of > the extruder on the machine and what is needed is > a way to create the 3mm material that that machine > can use. If a 3mm filament extruder is truly what is needed, then a continuous feed auger design is the way to go. I think it would require two augers to worby Annirak - Mechanics
I don't think the mobile hopper is necessary. I think that putting the hopper over the inlet would work, but there's a little bit of a challenge in it. It's not terribly complex, but there needs to be a mechanism to keep the granules from coming back out the inlet when we decouple from the hopper and when we start applying pressure with the piston. It might be as simple as a T fitting, but Iby Annirak - Mechanics
I think it's relevant to point out that we only see a plain piston working here. While it does work, it requires manual intervention to refill the piston. I know that there are likely easy workarounds to this, but I still think it is relevant to note the difference between a working manual intervention piston and a working automated piston. Brendanby Annirak - Mechanics
Bob, You seem like an expert on the piston method. Can you provide a diagram of how such a system would work? Thanks, Brendanby Annirak - Mechanics
I thought I covered that option. I guess I didn't make it very clear. That was the point where I referenced the concrete pump. The problem with this approach is that it requires a minimum of two motors and more likely three. The issue is that the piston needs a valve to prevent plastic from falling in behind it and it also needs a stirrer in the hopper to prevent a blockage in the feed. Theby Annirak - Mechanics
As I work on my auger granule extruder, I keep thinking about what other methods there are for making a granule extruder work. I've been thinking about it a lot, and I've come to the conclusion that all of the granule extrusion methods are actually just pumps. In that vein, I've been thinking about what other pumps would work well for moving granules. If we could guarantee a pellet size, ratheby Annirak - Mechanics
Forrest, I got upset because I couldn't see why you were pushing old technology which is gradually disappearing instead of trying to ramp up support for new technology. The "there's no point, no one's going to use this for building more repraps" argument got me distracted from the important point that DIP is going away. Foolishly, perhaps, I explained my motivations rather than the benefits toby Annirak - Controllers
I haven't properly introduced myself around here. I'm an electronics designer. As such, I'm a pretty young guy, only having done design for 5 years. Never the less, I have my finger on the pulse, as it were, of the electronics industry. The only reason that parts are still produced in DIP by many manufacturers is that there are legacy customers making large volume orders. When they start losby Annirak - Controllers
jbb Wrote: ------------------------------------------------------- > Forest raises a good point: pick and place is hard > and how many people will need it? As a community > effort one could find an accomplice to hand solder > the few SMT parts that sneak in. I can solder most SMT parts. I get stuck on BGA and anything with a powerpad. I realise that hand-pasting and a heat gun coulby Annirak - Controllers
Forrest Higgs Wrote: ------------------------------------------------------- > With all due respect, let me disagree with several > points in your presentation. > > > As most of you are well aware, SMD is where the > majority of new > > technology goes for a variety of awfully good > reasons. > > SMD was invented to facilitate smaller printed > circuit boardby Annirak - Controllers
Unfortunately, they were ebay specials. They came without datasheets. All I know is that they're rated to 16V, 320W, 60C delta.by Annirak - Mechanics
I've been batting around ideas relating to SMD. As most of you are well aware, SMD is where the majority of new technology goes for a variety of awfully good reasons. This does leave hobbyists in the dark, unfortunately, as soldering 0.5mm pitch pins is not particularly easy, especially with home etched or milled boards that have no solder mask. This brings up the topic of how to place and solby Annirak - Controllers
Peltier's don't have to be expensive. I got a pair of 320W peltiers for $40. Ebay helps.by Annirak - Mechanics
Well, it shouldn't be overly complex (once we have changeable toolheads) to build a paste printer and a pick&place reprap. With those in place, and a makeshift SMD oven, SMD should be no barrier to us. Brendanby Annirak - Mechanics
But RepRap doesn't use SMT...by Annirak - Mechanics
I'd definitely keep the cartesian bot intact. I'm not sure how good the electronics are, but if they're already interfaced, I'd not be inclined to go reinventing the wheel. Brendanby Annirak - Mechanics
nophead Wrote: ------------------------------------------------------- > Perhaps a brass nozzle and melt zone, a short > section of stainless pipe leadin to block of > aluminium with a big heatsink attached. > > You need to keep the SS section short because > there is always a problem point where the plastic > has softened but not melted. It just expands to > plug the tubby Annirak - Mechanics
degroof Wrote: ------------------------------------------------------- > Wasn't there an experiment like this done a while > ago? I have a vague recollection of there being a > problem due to a metal auger conducting heat back > toward the granules, causing clogging. degroof Wrote: ------------------------------------------------------- > Wasn't there an experiment like this doneby Annirak - Mechanics
Wade Wrote: ------------------------------------------------------- > Annirak, do you have a source for these 300% > efficient Peltier devices? With something like > that, who needs a RepRap? Thermodynamics be > damned! > Well, that's how heat pumps work. Efficiency numbers are virtually *always* over 100%. To get a peltier device to run as high as I've stated, you need to poby Annirak - Mechanics
I looked up the relevant thermal conductivities. Copper is 380W/mK, stainless is anywhere between 12W/mK and 45W/mK. Glass is 1.1 W/mK. I stand by my original assertion that I should use glass pipe as a thermal break. I still need to find a way to limit how much heat the auger conducts.by Annirak - Mechanics
Sadly stainless steel isn't widely available in MIP fittings. The design ethic behind this granule extruder is parts you can get anywhere. Peltier devices can be run at 300% efficiency. It all depends on how big the temperature differential is, so keeping the hot side cool is really important. A water jacket is another option, but it has some significant drawbacks.by Annirak - Mechanics
Graham, Did you notice that the LPC23xx and LPC24xx have hardware SD card ports? They implement the complete SD spec. They may not be ARM Cortex, but there's nothing wrong with ARM7-TDMI. The LPC23xx is limited to 6 PWM, but the LPC2468 has 12 PWM. Brendanby Annirak - Controllers