Hi Shahab, As with all DIY projects, the precision depends partly on how well you assemble and calibrate the machine, and on the quality of the parts used (flatness of print bed, etc). It will depend on how well your parts are lined up, how your stepper motors are driven, on the software you're using, the quality of your extruder, etc. But assuming that you take an equal amount of care with allby jbayless - General
What's a "four-nib cluster"? Jacobby jbayless - Plastic Extruder Working Group
So I think murrayd's goal is not to obtain a patent for his idea, but to prevent other people from obtaining a patent for his idea. Is that substantially easier? I'm not particularly keen on grabbing patents for my inventions, but I'd really hate someone else to patent my own inventions, and make me ask permission to use them. That's a nightmare scenario for me. What's a good way of protectingby jbayless - General
Buback Wrote: ------------------------------------------------------- > I've been thinking about glass recently; > specifically, why does it always feel cold when it > has such a low thermal conductivity? > > I know that that isn't really a scientific > question, but it got me wondering anyway. I found > some info at the corning museum of glass website > regarding the theby jbayless - General
rocket_scientist Wrote: ------------------------------------------------------- > Or maybe just activated charcoal from a fish > tank filter to soak the dangerous gases. I really like this idea.by jbayless - General
The plastics that Stratasys can print via FDM are: ABS ABSi (higher impact strength variety) ABS-M30 (higher strength and toughness variety) ABS-M30i (high strength medical and food-grade) Polycarbonate PC-ISO (polycarbonate variety) PC/ABS ULTEM (Polyetherimide similar to PEEK) PPSF (Polyphenylsulphone) I don't know if any of these are vacuum-rated. Perhaps ULTEM?by jbayless - General
I think we would not be able to sense it directly with an A to D. First we'd probably want to use a balanced wheatstone bridge, and then an instrumentation amplifier+high pass filter to boost the signal. I'm not sure about using a third winding, because that winding would also have a resistance change with temperature, and unlike the primary coil where we can use DC current to compensate, thereby jbayless - General
Yes... a mild steel ring ought to change resistance by 0.13% per degree C, and have a higher resistivity in general. It also has the advantage of a not needing as high frequencies, due to its magnetic permeability. But I would be concerned about corrosion. Over a 5 degree C range, that results in a restance change by 0.63%. These calculations are assuming that the cylinder wall thickness is higby jbayless - General
An update: At 260 C, a secondary made of copper or aluminum will increase in resistance by 0.1% per degree C. The electronics would need to be sensitive to this level of change in resistivity. (0.1% = 1 mV on a 1V signal)by jbayless - General
Well, I'm hoping to avoid heating the glass directly, in order to achieve a sharper hot-cold transition zone...by jbayless - General
Not only is there the skin effect, there's also the fact that you can just pump a ton of current through the copper until it heats up. Having a small number of turns on the primary winding will induce a small voltage in the secondary, and for a low-resistance secondary, that should result in an extremely high current. I'm stil working through the math. I hope to soon have a closed-form expressioby jbayless - General
rocket_scientist Wrote: ------------------------------------------------------- > Fantastic progress Jacob! I have been wondering > how to snip the fiberglass strands at the end of a > fiberglass, or combined fiberglass in plastic > extruder. How are you doing the cutting here? I > see a solenoid, but it is not down at the tip. It > looks like you would have to cut the wire a liby jbayless - Wire and Thread Embedded Extrusion
Good point NopHead. We can perhaps measure the temperature-changing resistance of the primary coil by running a DC current through it on top of the AC. Then we can isolate just the changing resistance of the secondary.by jbayless - General
Bienvenue, lucf! Voici la groupe d'utilisateurs RepRap en Montreal . Here's my attempt at a translation... Apologies if there's any mistakes! It's been a while since high school. Quotelucf Hello everyone, I've just come to join the forum and I would like to find this information if it's possible! 1.0 Is there anyone near Trois-Rivières (situated between Quebec City and Montreal) who owns orby jbayless - General
I like to keep myself as far away from lead as possible... Aluminum would be quite interesting though. Here's another neat thing: The induction heater can probably be designed as a kind of induction motor, too, so that the force it exerts on the melting metal wire will propel it out of the nozzle. That might help defeat the problem of surface tension that plagues metal extrusion.by jbayless - General
If the temperature sensor is small and thin enough, and the frequency is low enough, it might be magnetically transparent. But there's still the problem of getting leads out from inside the nozzle, unless you're measuring on the surface, in which case there's a large resistance between the heater and the sensor, which is bad. Although induction heating in a glass nozzle would be a very elegant wby jbayless - General
Hey Mike, I double-checked and got the same numbers as you do. I used this as the absorption spectrum data of borosilicate glass: And calculated the peak radiation wavelength using Wein's Law. For a heater element at 260 C, the peak wavelength is 5.4 micrometres. So yeah, seems like you're spot on. In that case, IR sensing might not be the best possible solution, although still probably a goby jbayless - General
Yes... that would probably be tough. I hope that a 1 MHz coil running several amps will not emit too much electromagnetic radiation and interfere with the other electronics.by jbayless - General
Hey Mike, That's right, we can't use a thermocouple or a thermistor - although the reason I was thinking of was that having a heat source inside the insulating glass and a sensor outside the glass would be very bad, because there'd be long delays between the input and sensor output. I see two ways to resolve this: Use a metal with a high temperature coefficient as the heating element, and measuby jbayless - General
By the way, Fluxtrol offers some good training videos introducing the principles of induction heating. I contacted them about having a thin-walled stainless steel ring inside a glass tube. Here's my message: Quotejbayless Dear Fluxtrol, I am a senior engineering student at the university of British Columbia, and leading a student design team to develop an improved 3D printer. I'd like to useby jbayless - General
Check your endstops? If the optical endstops are always triggering, then it will think it's homed as soon as it finishes the first layer, and proceed to move to some incorrect place to print the second.by jbayless - General
Sure, I'd be happy to give you advice if you'd like to continue the Spoolhead project.by jbayless - General
Not really groundbreaking for RepRap, but I found this article and thought I'd share.by jbayless - Administration, Announcements, Policy
I'm one of those people tinkering with glass nozzles, but I don't think there's any problem with what was being used before. The state-of-the-art nozzles right now are brass or stainless steel with teflon lining, and these work great - they can also do what you're talking about (that's more of a software than a hardware challenge). I'm experimenting with glass because I see it having some potentiby jbayless - General
As well, the UP print has wobbly towers too (although less so). The wobbling problem, as Nophead says, is because the prints are too hot. Those peak layers are small so they're finished very quickly, before they can go down. I'm pretty sure the newer firmware waits for the layers to cool before it continues.by jbayless - General
I think the UP! 3DP is nearly capable of that level of print quality. Most RepRaps haven't gotten there yet, but might well soon. Molding will probably be better, though I do like the idea of being able to print figurines at home to replace missing or broken ones.by jbayless - General
For heaters, I'm currently looking into flexible films, egby jbayless - General
Hm... What about a rotary encoder? With three detectors, the problem of skipped steps can be avoided, can't it? For example, with an encoder like this, you can always tell when the fine resolution detector has missed a step. The encoder will need to skip two or three steps before it can get confused, right?by jbayless - General
I think if you cool it quickly enough, it should work... It's something I'll be testing along with the glass nozzles this or next month. We'll see. =)by jbayless - General