That's why the press plate is on the z-axis, and only lowers to the exact height that the surface is supposed to be.by jbayless - General
Hi everyone, Here's a suggestion for a possible method to improve strength and surface finish of prints. It may also have the added benefit of reducing warping by relieving thermal stresses. The idea is, during the print after one or multiple layers have been set down, to "iron" the top layer, basically using a second heated bed but flipped upside down and coated with a smooth non-stick surfaceby jbayless - General
Induction heating has advantages over resistive heating in terms of the power density that can be achieved. With resistive heating, a high resistance (5-10 ohms) is needed, otherwise the efficiency is low, as the resistance of the drive circuitry becomes comparable. Materials with resistance this high are either some ceramic, or from a coiled metal wire. In either case the temperature rating is uby jbayless - Plastic Extruder Working Group
Hello, Hydroxypropyl xylan, known as "HPX", is a bio-polymer produced from the sugar xylose. It is a biodegradable, film-forming thermoplastic. In its normal form it is water-soluble, although a version called "acetylated HPX" is similar but non-water soluble. So far I have not been able to find any commercial sources of HPX, although it is discussed heavily in the literature. If it ever becomeby jbayless - Polymer Working Group
RepRap is wide enough that, if you want to work on it, studying almost any area of science/engineering/computer science will let you contribute directly... For example, if you became a polymer chemist you could help develop support materials. If you study mechanical engineering you could design better Mendels. If you study computer science you can improve the RepRap software to improve print qby jbayless - General
Leadscrews are not slow, if you pick the right ones. Multi-threaded screws get higher speed than single-thread screws and can go as fast as belts. Leadscrews will let you achieve a higher-stiffness drive, but will typically have more friction and inertia than a belt. Whether or not precision will depend on how you design the system, and what leadscrew/nut you use...by jbayless - General
Yes, Sebastien, I fully agree. My aim with that statement was not to bring a hammer down on people who have to-date uploaded only STLs, but to make them aware that such files are good for printing but essentially useless for making changes to. I think it's possible that many people simply aren't aware of how much of a dead-end STL files are, since they often do upload them with a license that peby jbayless - General
An .stl is not a CAD file, precisely because it doesn't allow the design to be edited. Developers have not signed off on the designs. They encourage them to be altered and remade, and do not guarantee that the design is error-free. Doing so is exceptionally difficult when all you have to work with is an .stl file.by jbayless - General
Yes, I also agree that an STL file is not a CAD file. That's why I believe that a project which only releases their STL files should not qualify as open-source.by jbayless - General
Awesome. =) I hope it works! I hear that titanium can be difficult to machine. But by no means impossible...by jbayless - General
nophead Wrote: ------------------------------------------------------- > But as I said, this is no different than changing > the gear ratio to do the same. > > Actually there is. The force goes down by the > inverse square. The force is transmitted by the > teeth of the pinch wheel and the limiting factor > is when the teeth strip, so you will be able to > feed smaller fiby jbayless - General
This is a very important question, and I'm glad you asked. I see a lot of people touting the benefits of 1.75mm filament, but I'm not convinced. Maybe there is something superior about the chemical composition of 1.75mm filament, or maybe it's manufactured to better tolerances. But as to the other claims that have been made, I'm skeptical. I don't think that 1.75mm geometry filament results in lby jbayless - General
Moving on to the sensing circuit, I've run the simulation with a Maxwell bridge circuit for improving the temperature sensing sensitivity. (I have also written code to evaluate the Owen Bridge, analysis is forthcoming). The best sensitivity I can get from a Maxwell bridge is -0.25 mV/(V degreeC), which is quite high. As well, because the bridge removes the DC offset, this can be amplified by anby jbayless - General
How could rollers work if the cross-section is circular? The rollers would need a circular hole in them, but then as they rolled, the outside radius of the roller would move faster than the inside radius. This would stretch and deform the filament. I don't see it working well.by jbayless - General
For now, I would just purchase ferrite, if it proves necessary. In the future, if homebrew filament is an option, it would be interesting to experiment with adding iron powder into the mix.by jbayless - General
Yeah, on second thought, you're right.by jbayless - General
@aka47 My own opinion is that using no thermistor is simpler than using a thermistor, even if it makes the temperature sensing circuitry a bit more complex. From a point of view of constructing the extruder, a thermistor means an extra set of wires that can come loose, kapton-taping a little bead that can unseat itself... Anyway, they're both good methods. Thermistors are definitely better-testby jbayless - General
Thank you! =) Yeah, I hadn't thought about radio-frequency harmonics... at the least we'll have to filter the power so that harmonics are at a minimum. On another note, right now I'm actually thinking that the best approach would be driving the coil with three different frequencies. The first will be a small DC component, used to measure the resistance of the copper windings and compensate forby jbayless - General
Hi everyone, Just reviving a dead thread here. I've done a significant amount of modelling work on the induction heated nozzle (more still to come). Here's some graphs that I've generated to help with the design. To generate them, I solved Maxwell's equations on a cylindrical domain, assuming the induction ring and primary coil are of infinite length -- an approximation that can later be checkeby jbayless - General
The melting is done by the heater coil above, the electrodes at the botttom are just present to propel the aluminum. You're right that it does need to be proven though.by jbayless - General
The small metal balls idea is cool, although mechanically intricate. VDX - in the design I proposed, the power conducting up the extruder is not more than a few watts.by jbayless - General
There's two reasons I think a standard RepRap extruder design would have difficulty with aluminum. The first is heat conduction; Aluminum melts at 660 C, above the temperature rating of Kapton, and sustaining that temperature in a nozzle that conducts heat would take a lot of power. As well, there aren't many (any?) heating resistors that I know of which are rated to such high temperatures. Windiby jbayless - General
@Mike: Yes, that's what got me thinking about it, too. The design I proposed in the first post is nothing like an arc welder, as the material is heated in a chamber before being deposited, like MartinPrice mentioned. One reason to "reinvent the wheel" is because arc welding gives poor control over the shape of the deposited metal, while an FDM approach might give better control resulting in highby jbayless - General
Hi everyone, This probably sounds crazy, and it probably is crazy. But I couldn't help but wonder about the potential use of metal as a material for FDM. In particular, imagine thin wire of pure aluminum used as a feedstock, to print structures from aluminum. I'd like everyone to present as many reasons as they can think of as to why using metal with FDM is a bad idea and can't work. Maybe noneby jbayless - General
I'm not sure it's necessary to screw them on the "right" way - in fact, it might actually be better to screw them on backwards, so that the narrow circular face of the nut is against the inner ring of the bearing, rather than the hex face. But, yes, I don't think that any nut can really be relied on to sit flat on a screw. I can't think of any way to really guarantee flatness without using a latby jbayless - Reprappers
I highly recommend Ultimachine's PLA. It's very round, smooth, uniform, and consistent. I haven't seen their ABS.by jbayless - General
To perfectly constrain the leadscrew between two nuts, I'd recommend using nylock nuts (they won't loosen from vibration) and a belleville spring washer to supply a preload. With a belleville washer, the bearing doesn't need to be tightly clamped, but there also won't be any play.by jbayless - Reprappers
In many ways I agree with Jono. If you can afford a PP3D, and if your end goal is to print parts to use for robotics, and if the PP3D meets your requirements in terms of build volume, then it's probably the best choice. The time you save might be well worth it. On the other hand, if the PP3D falls short in any way of your requirements, then you won't be able to improve it very easily.by jbayless - General
nophead Wrote: ------------------------------------------------------- > There is also a massive difference in the bend > radius, i.e. how tight you can coil it. That is > because stiffness is the fourth power so the 3.5 > is ~ 2.6 times stiffer than 2.75mm. ... Which possibly suggests a very sensitive method for detecting small changes in filament diameter, much smaller than directby jbayless - General
Hi Shahab, I'm not sure I can recommend for or against any specific suppliers - I haven't purchased from very many, so I'm not sure how the quality varies from one to the next. I think that most of the stores selling parts are quite reputable. Also I'm in Canada, so I'm not sure what good parts suppliers are in Norway. My point was more generally that, if you are aiming for maximum precision,by jbayless - General