Ah, I didn't know that skipped readings was a major problem with incremental encoders. I suppose it might be, if the encoder is spinning very fast. People keep bringing up the optical mouse idea, but I'm pretty sure it doesn't work well. To my knowledge, the reason that optical mice work so well for computers is that the human controlling them is constantly measuring and correcting the cursor poby jbayless - General
Is there an advantage to using computer vision over having an encoder wheel on the pulleys?by jbayless - General
Hey Mike, Glad that you started a topic about this. What about just two nozzles that blow cold air from opposite directions, so that there's not much force put on the hot filament?by jbayless - General
I think an encoder strip for the axes would be very nice to have. For boosting print speed, I've been thinking along similar lines. The best method I can think of is a dual-extruder setup, with one nozzle for infill and one for detail work. That's much simpler than a transforming nozzle. The infill nozzle could just be made from a pinched tube of stainless steel. With the tip pressed around anby jbayless - General
My cheap plastic Staples ruler might not be too trustworthy, but those are probably good guesses. I can't find my nice precision ruler anywhere. Yeah, they haven't determined a price yet, so I'm also curious.by jbayless - General
Speaking of commercial suppliers, today I biked down to CanSci glass in Richmond. They very generously offered to make me some free extruder samples to test out. The quality is really fantastic: It looks like they've used a similar technique to Mike's; first creating a taper and then using a diamond file or something to grind down the tip to the desired diameter.by jbayless - General
What kind of glass are you using? I think it's very important to use borosilicate glass, like pyrex. Regular plate glass can't handle thermal stresses.by jbayless - General
Mike - I haven't yet, because all my glass stuff is at home and all my reprap stuff is at the university. I'll bring them in next week. I'm glad that the borosilicate will be able to bear the temperature gradient. It was something that I wasn't sure of, even though I know that it's made to support steep gradients. Nichrome should work fine too, and it'd be a bit more compact. It's just a bit aby jbayless - General
Oh... yes... let's see. I would be expecting a fairly linear temperature gradient along the tube. Assuming that the hot end is at 260C and the base is at 40 C, then the temperature should drop by 4.4 degrees C per millimeter. 5 mm up the tube the temperature will be 240 C, which is still hot. My main concern about a heat sink would be that it would draw a lot of power from the heater. But maybeby jbayless - General
Yes. I haven't specified it yet, but for now I'm planning to mount these to an aluminum chassis, so that and the metal compression fitting should act as an effective heatsink (I hope). For a plastic chassis, you probably would need to have a heatsink on the tube near the top.by jbayless - General
Apologies again for being slow with the progress updates. I can confirm that the 6mm glass tubes work very well with 6mm compression fittings, as well as 1/4" compression fittings. The connection is extremely rigid. PTFE Bowden cables also appear to work well with compression fittings, allowing neat things like this: Once I make a heater for the nozzle (likely based on Nophead's design as I hby jbayless - General
Pity that I only saw this not-so-old post because it got spammed. But darn, Mike, that's quite clever.by jbayless - General
Casainho, we can't compare apples to oranges. Even Makerbot's deluxe kit comes unassembled, and that's at $950 without the Mk5 extruder, heated bed, or relays. The Mk5 extruder -- almost a necessity, given how failure-prone the previous one was -- is a further $185.00. The heated bed is another $50.00. So that adds up to $1185. And you still then have to build it yourself and tune the software toby jbayless - General
I'm rather surprised you would write this Casainho - and I wonder if you mean it, or are just writing it to provoke a strong defence of Mendel. The print quality I've seen on most RepRaps tends to be as good or better than the CupCake CNC, and the print area is certainly larger. Their technology is always an option even for RepRap users - their circuitry is running my Darwin, for example, and Iby jbayless - General
I'd also like to report that the 6mm glass tube fits great with 6mm compression fittings. I'll soon try it with 1/4". That would allow room for some kapton tape windings to boost the diameter, which also might keep the glass from cracking (although I haven't had any problems with this so far). I think that, since the pressure in the compression fitting is applied very evenly, the glass is quiteby jbayless - General
Fascinating! Although I'm sure Nophead is right that the roughness won't be there when actually printing, I wonder what's causing it. It might just have to do with the way the filament is extruded, or the smoothness of the orifice. But could it be that brass is, so to speak, ABS-philic and glass is ABS-phobic? (As in hydrophilic and hydrophobic; I don't know the actual word for ABS). If that werby jbayless - General
Interesting. I'm surprised that the glass heat conduction is a problem, but I suppose it makes sense for high flow rates of plastic. You're using 8mm tube, right? 6mm might be better in this area.by jbayless - General
Ha... I'm honoured But currently the 3D printing page is a bit of a mess. All the printers in the comparison table are Stratasys, or RepRap derivatives. Plus, it's not clear to me what the distinction is between 3D printing and .by jbayless - General
Hey Mike, Sorry that I haven't had a chance to report yet; I'm at a very busy period right before school starts. That video looks very promising - is that PLA? That's one of the first tests that I was planning to perform. Jacobby jbayless - General
Yeah! That's exactly what I'm thinking. I agree that a safety factor is needed -- but on the temperature side, rather than on the power side. Because you're right, the plastic will be cooler than the glass, which will be cooler than the resistor. To my knowledge, for a given line of resistors all made from the same material, an increase in power rating refers to an increase in heat sinking capaby jbayless - General
Similar product, different brand: The above products suffer from being rather long (50mm), which means the heater would run nearly the whole length of a typical nozzle. Needless to say, that defeats much of the purpose of using glass nozzles. These ones below have a lower power rating, but are more compact (16 mm). I believe that the power ratings are not very relevant, because they assume aby jbayless - General
Here is a very plausible replacement for nichrome heating element. This would likely be more suitable for a glass tube nozzle than the Makerbot Mk5-style power resistors that many people are using. Stackpole Electronics tubular power resistor SWT/EWT series. Handles temperatures up to 350C (silicone coating), 500C (enamel coating). 25-watt EWT resistor has an inner diameter of about 8 mm. Migby jbayless - General
Thanks I always enjoy heat transfer problems. I get to apply what I learned in school! ^^ But yeah, that aside, I suppose it's a matter of what's available. Aluminum does have its advantages... it's lighter, for sure, so you can get a nice lightweight build platform from it, which is probably an important consideration for Mendel where the platform moves back and forth. And glass can be hard toby jbayless - General
QuoteThorp Aluminum is a much better conductor and will do a better job at getting heat into the plastic. I don't think so. Consider a five-millimeter thick build plate, and a thirty-millimeter thick plastic object printed on top. Assume the bed's heating element is thermally well-bonded to the build plate. Aluminum has a thermal conductivity of 250 W/mC. ABS has a thermal conductivity of 0.3by jbayless - General
I don't think buoyancy is a critical factor for support material. Gravity is not a strong force when dealing with these thin filaments; adhesion is the primary concern. Experiments have shown that Mendel can print upside-down, for example. A hot oil bath is unlikely to work as an effective support material, even if the oil is very dense, because the plastic won't adhere to it. My original recomby jbayless - General
Just to let everyone know, the glass nozzles I ordered from Mike arrived today. =) They look great! I'll post more about this later because right now I'm in the middle of a major poster competition and am very busy.by jbayless - General
A couple weeks ago I hit a pothole at a high speed while riding my bicycle. Fortunately I was fine, but several non-critical pieces of my bicycle suffered damage. The ABS plastic enclosure for the gear change mechanism on the front handlebar shattered, exposing the oiled internal components to the elements. The holders that attach my safety lights also broke, so after I picked up the pieces scattby jbayless - General
I myself am very excited for multimaterial support for the RepRap Mendel. I think this plays to the strengths of the technology, and is really essential in achieving a better overall design than Mendel which, despite refinements, is probably about as good as a single-material replicating printer can get. Multi-material technology is something I'm keen to develop on the mechanical side. Support mby jbayless - Huxley
If your polycarbonate sheets are flat enough, I expect they would be a viable alternative to plywood. Acrylic will in most cases not be suitable, because it is very brittle. With some redesign of the parts, polycarbonate could probably make a superior machine than TechZone's; polycarbonate can be bent at room temperature and processed like sheet metal, which means you could make stiffer and morby jbayless - General Mendel Topics
That's ok. I like to think that I'm somehow partly responsible for all the good ideas being generated, even if they are off-topic. ;-) Slowing the extrusion with no active cooling might have a similar effect, although there's probably only so much that a filament can cool when the hot extruder is sitting right on top of it. And it would certainly increase the printing time of an object. For flaby jbayless - General