I haven't been on here for a while for a large variety of reasons, but I'm currently working on 3 designs that could all be useful in decreasing non-printed materials and costs, depending on how well they work. The first and closest to being in need of physical testing is a linear bearing and rail system using recirculating ball bearings. I've sized it to use 6mm diameter balls, as they are theby Corwin - Kartik M. Gada Humanitarian Innovation Prize
This is a concept I came up with today as a possible way of reducing the number of the most difficult to source and expensive reprap vitamins in a future subspecies. It would unfortunately require a switch to a polar coordinate rather than a Cartesian robot, which has been discussed and discarded before. At any rate, the design works like this: 1)The build stage is set up as a very large gear, anby Corwin - Mechanics
Build speed is a bit of a stumbling block, yes. Build times for larger objects can reach into the 10s, 20s, and 30s of hours even on commercial Stratasys machines. 2 and 3 day builds have been done on commercial FDM machines - "rapid" prototyping can be something of a misnomer, it's really only rapid compared to the alternatives. The 8.92 days figure, though, is unrealistic for a real build. Besby Corwin - Mechanics
Your best bet is probably to simply buy an ATX powersupply.by Corwin - Controllers
Bipolar is fine, actually if you're using the standard reprap electronics you're stuck with it. I think he was talking about another driver he has?by Corwin - Controllers
Enleth - most fluids aren't compressible, but molten plastic actually is to a certain degree (http://en.wikipedia.org/wiki/Non-Newtonian_fluid). It isn't a huge deal at the usual scale of extrusion for a reprap, but if you're looking at pushing out from a large tank/pool of plastic, it can become more of an issue.by Corwin - General
If it works (i.e. no burned out steppers, no irreparable mechanical issues) then definitely. Even if not everything is functional, for 9.99 there's no way you're going to regret having bought it.by Corwin - Reprappers
Ahh, ok. So you've been talking about the same thing nophead, brought up, the mirrored parts in every other tripod. You're absolutely right - you get 3 of the same, and 3 mirrored of the same for every hex of buildspaces. That's EXACTLY what I'm trying to produce, though. The design goal here isn't to produce a lot of unique objects, it's to produce a lot of the same object quickly and efficienby Corwin - Delta Machines
I think I understand what you mean.. the thing is I don't agree that it changes the mathematical complexity. When you lower a stage, the print heads attached to it move away from it. For the center one, this means they all move towards the outside of the hexagon, towards the edge between the other two stages. For another stage, the movement is in a different direction - but it has the same magniby Corwin - Delta Machines
Another drawing, updated to emphasize parallel bars and expanded to show a configuration of 7 building tripods. Also, an "axis" designation, M1, M2, or M3 is appended to each column to show which ones are hooked together. Viktor, I still don't understand the problem. As I understand it, any point in the build space is described by 3 values, one for each column - call them M1, M2, and M3 for now.by Corwin - Delta Machines
I'm not sure I understand your objection this time.. The linkages were intended to be the same as in your tripod on , or possibly a little closer to that on the iFab if I went with tierod ends. The two parallel bars with universal joints system coming from one slider seems to work just fine for positioning. Since all I'm trying to do is make each tripod (each triangle of the hexagon) produce an iby Corwin - Delta Machines
Actually the way those lines run in should be ignored.. it was just a really quick way of showing that each center point has independent connectors to the column. Sorry for the confusion. My intention for the actual design is to use standard 1/4" tie rod ends (because I can get them at the local hardware store, and I would assume the same is true for most people in the U.S.) or possibly magnets,by Corwin - Delta Machines
That Cartesian parallel manipulator is very cool indeed.. Those linkages are definitely the sticking point, though. There's actually a way of doing something similar with a more traditional Cartesian layout using a lot of linear bearings to decouple the motion in the same way, it's just expensive XD. Correct me if I'm wrong, but the links are actually taking ALL the load in torsion as far as I cby Corwin - Delta Machines
Viktor, I'm not sure we're on the same page here. The arms don't "cooperate" or "reach" between triangles. Each triangle is a completely separate build area with it's own hinges and extruder (now that I think about it, getting that many extruders running could be quite a challenge in itself XD). Hopefully the image attached to this can help clear things up somewhat if I'm right about where we'reby Corwin - Delta Machines
Double-posting to put up a quick 3d model I made in Sketchup of a hexagonal stepper column. the center of the five 1/4" rods would be the threaded rod. The dimensions aren't right at the moment for any real products, but the other four would be smooth 1/4" with a sintered bronze bearing in the carriage for each. The stepper motor would be in a cavity under the bottom unit (for the moment, the oneby Corwin - Delta Machines
@Viktor: What is it about the traditional design that makes it difficult to cross over? I couldn't see anything in it when I was looking at the designs that seemed to inherently prevent it, but if I missed a major problem it wouldn't be the first time. If it's possible to even share 1 stage between 2 build platforms, in another configuration (ie just 2 triangles opposing each other), that still wby Corwin - Delta Machines
So some time ago, Viktor proposed the idea of a parallel kinematic tripod design in place of a cartesian frame. At the time it was interesting and showed a lot of promise, but never really went as far as a full one repstrap (as far as I know). Just the other day, a design made by Festo, the iFab, made its way onto the forums and net with a video showing the idea put into practice. This gave me aby Corwin - Delta Machines
Actually.. I just realized why I felt odd about that conversion. It's wrong. A 1/4-20 threaded rod is 20 threads per INCH. One revolution is therefore 1/20 of an inch of movement. If your initial diameter is 1/4", your initial radius is 1/8" of an inch. Your circumference is 2pi*r, so 0.785398163". 1/20 of an inch is .05" in decimals. So your reduction is from .7854" to .05", which gives a figureby Corwin - Mechanics
Is it just me, or do the 4 springs on the extruder mechanism look eerily similar to the Mk. 2 Extruder design?by Corwin - General
Ack! No, I did not notice the part with the 1/4-20 rod. (that'll teach me to speedread the forums XD). As far as torque/force is concerned, I think that it is like any other gear reduction. That makes it a 20:1 reducer. I'm not entirely certain what figure is used for initial radius though. If it's 1/4", you have an initial torque of 9.90517848. A 20:1 reduction would then give a force of 198.1by Corwin - Mechanics
Torque = Force * radius. (so it's actually kg*cm, not kg/cm). 1kg*cm = 0.867961662 lb*in, so the motor has 2.47629462 pound in of torque available. That means that if the "shaft" of the motor (ie including the drive gear) were 1 inch, if could supply 2.476 pounds of force. That would be enough force to build 250PSI on a piston with just under 1/10 sq. inch cross section. With an additional 10:1 gby Corwin - Mechanics
If you really want to get the thing moving quickly, one trick I came up with for making simple 2.5D milling codes is this - make a simple object in Art of Illusion that is about 1.2 times as thick as your layer height setting in the RepRap Host Software (the idea is to make it "print" just one layer). Load it in, position it, etc. Then have the host convert it to GCode. Open up the Gcode in notepby Corwin - RepRap Host
On an interesting note, I'm pretty sure that this kind of thing (focusing of high-wattage/high-heat bulb) is how the "Desktop Factory" works, based on what they've said about their "imaging subsystem" being one of their major issues.by Corwin - General
>>assuming 100% absorption Correct me if I'm wrong, but I'm thinking this is probably not a reasonable assumption. Aluminum isn't going to be absorbing light very effectively. You're right that convective cooling is most important at these temperatures though.by Corwin - Laser Cutter Working Group
I've been working on something similar, intended to be driven by a stepper. I believe I may have come up with a new thermal break (at any rate I haven't seen anyone else talk about having made anything like it, though I'm sure it's been suggested at one point) that you may want to consider - I have an airgap of about 2/3" (which could be made a lot less, I'm still experimenting) between my hotby Corwin - Mechanics
I believe you need to put in the COM3 without the /dev/. That's how it worked for my arduino, anyway.by Corwin - RepRap Host
As far as I know there are no pin-compatible 3 amp replacements for the hbridge in the reprap stepper driver, so I don't see any reason to try to modify it directly.. the logic chip could be used in a new design, but that's about it. 60 cm by 120 cm is pretty small but that's not particularly relevant - there's not much difference for the motor load between 60cm and 300cm, really. If you were doiby Corwin - Controllers
You're right that the reprap driver is bipolar, which yields more torque. However, the motors that you are looking at are rated at 3 amps per phase, while the reprap drivers are 2 amps. This won't prevent you from using the motors with the reprap driver, but it does mean somewhat less torque and somewhat lower maximum rpm (it definitely means less power, since electrically that's P=IV, but I'm guby Corwin - Controllers
Honestly, if you're planning to use the hobbycnc steppers you may as well use one of their cheap driver boards as well. They're unipolar, but they've worked well for my repstrap so far. (admittedly, it's only milling polystyrene insulation for the moment, but it's moving just fine on 12 or 24 volts). I bought their EZ Driver Kit, . It's actually cheaper than 3 axes of the Reprap board ($64 verby Corwin - Controllers
The Darwin already uses stepper driven timing belts. If you mean you want to eliminate the steppers in favor of DC motors using a mouse sensor for closed loop positioning, it's definitely possible - go ahead and give it a shot.by Corwin - Controllers