Hi Viktor, Sounds like my pressure-sensitive three-way valve. The pressure would hold the ball to one side, and it would be that much harder to pull the ball away to the other side when you want to switch. Of course, the pressure in the liquid could easily be much higher than the force created by your magnets. Maybe the computer would be smart enough to stop pumping just long enough to switch thby Samuel - Mechanics
Hi Viktor, I was thinking of using a one-way valve so that it could passively allow the pump to work, instead of having a computer apply power to both the pump solenoid and the valve solenoid at the same time. It seemed like a good way to make a simple pump, since it would only require one coil, a spring, and a simple one way valve. Maybe your two-way valve would work better, but I don't see hoby Samuel - General
Hi Viktor, The other problem with that design is that it requires constant power to hold the ball in either position, at least as far as I can tell. It seems that the pressure of the flow may be able to hold the ball in the "open" position, but unless I'm mistaken it won't stay "closed" without constant power. I suppose it depends on the application which is better, pressure independency, or thby Samuel - Mechanics
Hi Viktor, Hmm.. I see your point. Maybe a pump could be made by using a piston to pump through a small one-way valve such as the ball and cage valve I mentioned earlier, or a flap valve. The solenoid would oscillate back and forth using a spring to pull in one direction and electricity to pull in the other. When it pushes out, the valve would allow the liquid through. When it pull back, becauseby Samuel - General
Viktor, Sounds almost like an old fashioned synthetic heart valve, called the Ball and Cage. It's a one way valve. When the fluid tries flowing in one direction, it forces the ball away from the hole, where it is caught by the cage, allowing the liquid to flow through. In the other direction, the fluid forces the ball against the hole, preventing the fluid from passing. You could instead make aby Samuel - Mechanics
Viktor, How hard do you think it would be to take one of your syringes and make it into a solenoid, so that the more current you apply the greater the pressure, and the more contracted the muscle? Would it work? Or is there a better way, such as just using a motor to pump liquid instead. I should think that getting the reprap to only require simply wound solenoids would be better, and more repraby Samuel - General
Great job. It seems to work pretty well. And I think I understand your idea for a pressure insensitive valve. Basically, the valve piston, i.e. nail, needs to move perpendicularly to the air pressure direction. Then you only have to worry about friction. Also, for gravity independence, I'm not sure exactly how to lock it either way, but you could use a spring to hold it closed most of the time.by Samuel - Mechanics
Say, zzorn, On your blog, you mentioned trying tape in a grid pattern, and the fact that it needs to be braided, with not contact between strands. I think this is because the point of the wire is to provide a material that doesn't care what the diameter of the tube is, but still can't stretch, and thus forces the muscle to contract lengthwise. If left to its own devices, the rubber would just exby Samuel - General
Hi Viktor, When you say "soft-pressing" about your ferro-fluid peristaltic pump does that mean low pressure, or "soft," but possibly high pressure? i.e. not "harsh," so that the blood cells get to flow out of the way before being crushed? Also, Why can't you design a tripod that can be stiff? It seems to me that triangles are considered more stiff than squares, but that may only be ture if theby Samuel - Mechanics
Fascinating story. It seems that we're posting asynchronously. Let us know how it goes with trying to get those tools and pieces. What do you think are the main advantages and disadvantages of a tripod system, compared to one of the standard cartesian systems? You seem to like them, and it sort of makes sense, but I'm not familiar with them enough to know exactly why. Thanks, -Samuelby Samuel - Mechanics
Viktor, I think I understand how the pump in the second image works, i.e. the ferro-fluid forms the screw for pushing your liquid. Does the ferro-fluid try and form-fit itself against the outer wall as it moves? Does it reduce friction? About the first image though, I'm not exactly sure what I'm seeing. On the bottom and right it looks like you're using ferro-fluid to apply pressure to the hoseby Samuel - Mechanics
Viktor, what tools are necessary to make those micro-fabbers? Some of them seem pretty advanced. You said you were working for a small company. Is that where you do the design and construction of these micro-fabbers, or do you do that as a hobby? Either way, they are very cool, and I wish I could make them myself. Unfortunately, I'm almost too cheap for reprap, hence my desire for muscles insteby Samuel - Mechanics
Is it possible to extrude LDPE (recycle number 04)? Its just that I end up seeing it a lot in plastic bags, and it would be nice to be able to extrude that too. Wikipedia claims that it has the same melting point as HDPE (120by Samuel - Mechanics
How hard do you think it would be to get a reprap to make good, air or water tight tubes? If it could do that, I could easily see a reprap that is structurally based on jointed plastic tubes and hydraulic or pneumatic muscles. All you'd have to do is design a reprap that is structurally based on tubes that could all fit inside its working area. Actually, using tubes sounds like a generally good iby Samuel - Mechanics
So how would you implement that fractal following head in mechanics? I understand how to do it with a mathematical function (sort of) but that is just a compression method, i.e. one number as input becomes 3 numbers (cartesian coordinates) as output. Is the goal to reduce the number of motors? (inputs) If so, it sort of makes sense, but it's very complicated, and there are other was doing that.by Samuel - Mechanics
Thanks for the information on the scale of your machine. It always amazes me how small your devices are. Whom do you work for again? Sounds like a neat place, from what you've been able to design there. I've known for a long time that it takes as many axis as you want degrees of freedom, having experimented with various coordinate systems in a 3d game I've been working on. But it continues toby Samuel - Mechanics
How hard do y'all think it would be to use the artificial muscles of whatever variety to power a reprap? I should think that with enough feedback loops for determining current position, a pneumatic muscle capable of contraction to 25% would be quite capable of contracting slowly enough to get the precision required. Maybe I don't know what I'm talking about, but with Viktor's linear column style,by Samuel - General
Cool idea. It looks pretty scalable, at least in the Z direction. The only issue is that you don't get much horizontal motion. It probably has nearly enough range to make it's own structural beams though, and that's better than the Darwin in that regard. It's also nice because all of the axes are in the same direction, simple, and redundant parts-wise. Easier to reprap that way, I think. Isn't iby Samuel - Mechanics
I'm in Cary, NC, but haven't built anything of note yet. I've mostly just been asking pesky questions, and coming up with useless fantasy ideas.by Samuel - Reprappers
Laser still sounds awesome. The first time I ran into RP was on the history channel - modern marvels, a few years back, with a STL system. It looked like a laser flashing on a vat of liquid, and thirty seconds later a smooth, clear plastic model of a space shuttle ready for wind tunnel tests popped out. Of course, it was probably time lapse, but I will never forget that film clip. Unless I eventuby Samuel - Mechanics
I haven't read the design docs for a while, so I may just be asking the obvious, but is there any particular reason to use the back shaft? How hard would it be to modify it for front shaft only? Most cheap steppers are single shaft, so that's my reason for asking. Obviously if someone found the holy grail stepper with 2 shafts, 400 steps, tons of torque, and only $10, the question would be poinby Samuel - Mechanics
RepStrap stands for a device designed to bootstrap the construction of a reprap. It is generally cheaper to build, but not as reliable, and made out of whatever parts are available. Since there are no official reprap parts available, this is the most common kind of reprap. Can't wait to see what you come up with though, as almost all repstraps contribute new experience and ideas. Maybe we shoulby Samuel - General
There has been a bit of interest lately in different ways to do repstrap Cartesian systems, so I thought I'd open a general discussion of the various pros and cons of the different forms. Given 3 coordinates: x, y, z; x and y being horizontal, and z being vertical, I can imagine three different systems: 1) The reprap method. The head moves in x and y, the table in z. This has the advantage of tby Samuel - Mechanics
I don't know much about extruder design, but I should think that you would want another gear or bearing on the other side of the filament, instead of just a pvc or polymorph wall. It would cut down on friction, though I suppose that since the real choke point is at the nozzle, it may not matter much. -Samuelby Samuel - Mechanics
That might work, but you may have a problem if something gets stuck in the tube. Also, supposedly there has been some effort to get shorter tubes, because they cause less friction, and are thus easier on the extrusion motor. I don't know whether the possible advantages of cutting down die swell would be more valuable or not than the other ramifications of that change. You'll have to get a responsby Samuel - Mechanics
Looks great. Nice job using Lego. Hopefully it can successfully print the reprap parts you need. I can't wait to see more pictures. -Samuelby Samuel - General
Actually, seeing as this is an open forum, I'm very surprised at how few posts have poor English or flame-war content. It is rather hard to find such places these days. I'm not saying that it's alright to have such things on the reprap forums, its just that I think everyone has been remarkably sportsmanlike so far. Keep up the good work. And let's not invoke Godwin's law just yet, shall we? -Saby Samuel - General
How hard would it be to make a head that can extrude various forms of clay and cement? I think such a head would be rather useful, either for making aluminum-casting molds directly, or as cheap filler material. You could then theoretically use any material that comes out as a thick paste, such as your polyfilla or regular backyard clay, as a support material. You might even be able to extrude solby Samuel - General
Sounds like an interesting business venture, drvanthorp. Maybe you're on to something.by Samuel - General
It seems to me that the slowest part of each layer is the filling in of the part known to be solid. I remember reading on the blog about an idea where the model was honeycombed into cubes or pyramids internally, so that it would take less fill per layer, and thus less time. Are there any other possible ways to either reduce the amount of infill, or change the way its done? I was wondering if mby Samuel - Mechanics