Hmmmm..... I wonder what happens if you mix dry plaster with rubbing alcohol and then put it into a syringe? Might set very quickly. /me goes off to try it. Wish him luck.by RussNelson - General
1) Seed sites .... well, Adrian is going to have to pick seeds regardless, by virtue of (very likely) having the first working Darwin. I'm sure that he will pick sites that he believes will make ten, not two, child repraps. 2) Unless repstraps are actually Darwins, I don't see how the lessons from one will transfer over to the other. 3) I'm impatient, too!! But I want to build something thatby RussNelson - General
Why are people trying to repstrap? Seems to me that once there's a design for a reprap, one person makes two, two make four, four make eight, etc. So it seems to me that work towards the goal of the reprap should go into solving the design problems -- and they require the use of something very close to Darwin. Not meaning to rain on anybody's parade.by RussNelson - General
I've thought about this some more (better to think before building, eh?) What I suggest is a "solid push" system, similar to the current extruder using a filament. The advantage that the filament has over the granules is that the filement is a constant diameter. You know that if you push a certain distance of filament into the melter, you get a certain amount of extrusion. Not so with granuleby RussNelson - Mechanics
Well, my suggestion is that all five gears should be the same diameter. That way, in effect, the stepper is driving the screw directly. With those sizes, there's no overlap, so all the gears can be in the same plane. Or, if you need to change the ratios, the center gear could be thicker, and then the screw gears could overlap, top left and bottom right below, and top right and bottom left abovby RussNelson - Mechanics
Hmmm..... Sparkfun has $15 1.8 degree steppers that appear appropriate from the specs.by RussNelson - Mechanics
Seems to me like the problem could be solved by having a metal tube containing capa, the bottom of which is above melting temperature, the top of which is above melting temperature, into which you force granules using a pair of opposing gears. The granules drop one by one from a hopper above. You could establish the temperature gradient along the tube by using cooling fins. You might want a gradby RussNelson - Mechanics
I'm wondering if it wouldn't be better to use five gears instead of a belt to drive the Z stage? If the Z stage screws are N units of distance apart, then the diameter of the gears would be N * sqrt(2) / 2 units of distance. The motor drives the gear in the middle, which drives the four screws of the Z stage. I'm suggesting this because the gears are RP-able whereas the belt isn't, and neitherby RussNelson - Mechanics
Conventional manufacturing of many identical components is cheaper. It will always be cheaper to make many of the same thing using a custom machine, even when we have robots to make everything. Just as people have comparative advantages (ME's are better at mechanical design; EE's at electronic; CS's at software), so do machines. Where the RepRap gets interestint is that it's a machine which maby RussNelson - General
Forrest Higgs Wrote: ------------------------------------------------------- > RussNelson Wrote: > -------------------------------------------------- > ----- > > The problem with mixing causes is that you > > restrict your volunteers to only those people who > > agree with every cause you espouse. > > Which is precisely what you've proposed doing. > I'm doneby RussNelson - General
Forrest, everyone will advise you not to mix causes. If you're a La Leche League Leader (more likely your wife, as mine was), they strictly tell you not to get involved in other causes because of your public face as an LLL leader. Richard Stallman has a separate page for his leftist advocacy (http://www.stallman.org/) which is completely separate from his Free Software Foundation advocacy. Theby RussNelson - General
Forrest Higgs Wrote: > I see that you have several objections to what you > perceive as the ideological stance of the > project. No, worse, I see an ideological stance which is independent of the goals of the project. > Adrian even talks about Marx and Engels there. Yes, he talks about them being mostly wrong. If even a poor person can afford a RepRap, how is there any truth to whby RussNelson - General
Seems to me that gear motors plus a shaft encoder could produce a much higher slew rate than stepping motors driving screws. The question that I have is whether a PIC or Arduino (Atmel or similar low-speed processor e.g. msp430) could keep up with the optical interruption rate necessary for high resolution? Has anybody tried that? The nice thing about stepping motors is that if you stay withinby RussNelson - General
Hmmmm.... spackle takes quite a while to dry. Plasterers will apply it, then go away for a day. Or is it possible to force it to set more quickly by applying heat? That seems like a good material: set it by applying heat, dissolve it by applying water.by RussNelson - General
Forrest Higgs Wrote: ------------------------------------------------------- > RussNelson Wrote: > -------------------------------------------------- > ----- > > I object to prominent poor economics. > > If I've read your posts correctly, you seem to > object to the use of the phrase, "wealth without > money". Your objection seems to come as a result > of havingby RussNelson - General
One question I haven't seen answered it "What is the support material made of?" and "How does it get removed?" Okay, that's two questions.by RussNelson - General
I think that conventional manufacturing of bulk parts will always be cheaper than any replication machine. After all, people are a replication machine, and yet we have resorted to conventional manufacturing.by RussNelson - General
Mike, my point is that wealth and money are separate concepts, yes, but are not divorcible. As a tagline, it's weak. Why put your worst foot forward? I'd rather see "Bringing capitalism to the people". It's much more accurate, and not offensive to anybody. If you're a Marxist, then you can think of it as workers owning their tools. If you're a capitalist, then you want capitalism everywhereby RussNelson - General
Forrest Higgs Wrote: ------------------------------------------------------- > Adrian's philosophy on Reprap is, imo, central to > the whole project. The philosophy -- making capitalism available to everyone -- is fine. I object to prominent poor economics. If the project supports one bad economic idea, what else has it gotten wrong? If the main concept "wealth without money" is wrong, tby RussNelson - General
Roach_S Wrote: > What about gearing the motors for that extra bit > of positional accuracy? Gears introduce slop. For a gear to work, it has to have enough play for the teeth to slip between each other. This introduces errors since you don't have control over the play. That's why you rarely see a stepper motor geared down -- steppers provide precision which gears take away.by RussNelson - General
Yes, any slowdown you're seeing is due to the dog days of August. Once it's possible to buy a complete set of parts, you'll see interest explode. Right now, you can buy all the electronics, motors, rods, and even extruder head (yay!), but the specialized plastic parts are the problem.by RussNelson - General
Does the poor economics on the front page bother anybody else? I don't want to distract anybody from repstrapping, but "Wealth Without Money"? Having balderdash that prominently figured is not encouraging. Okay, so the reason it's balderdash is that you're not likely to have wealth without money. Here's why. Not everybody does everything equally well. That's why we have machinists, mechanicby RussNelson - General