Fingers crossed, and all. :lol: What did you change? BTW, please do share your experiences with NinjaFlex when you try it. So far I only tried FPE. I used SanjayM's settings (from this thread on RepRap Forum) and it worked well from print #1. But I'm interested in NinjaFlex for the colours available.
So i removed the glass and put kapton on the aluminium. Bed at 75 and first few layers at 240, then down to 230. Used 6mm brim and a decent coat of the hairspray. The brim curled a little, but only after a good 8mm worth of height. Not too bad, but I still suspect it would be even better with a bed at 85ish
Yeah. On the plus side, this one will be a good prototype cos I've noticed a few little things I need to change. But itll be good to double check the hot ends fitting
Ok, so I got 2 sets of power resistors today and some high-conductivity thermal compound. One set is 2.2R and one is 1.5R. Am I correct in thinking the lower resistance ones will give me more heat?
Yes. From Ohm's law, W = V² / R. The lower the resistance, the higher the power. However, from the same equations, current will also go higher. How are you wiring the resistors? (I'm assuming in series). Be careful not to go over the tolerances for your wires, connections and electronics.
right, so going by W= V^2 / R, W has to be less than what it's rated for, right? which means none of my new resistors are suitable. they're all 15W crap. edit: oh wait, it's the COMBINED resistance of all resistors in series, right? double edit: so I'm 0.8R away from it working. I'm going to measure the resistance of the wires I'm using to wire it all up, but failing that, I'm going to make up the difference with nicrhome resistance wire and use it as a secondary heating element. Le sigh.
Your current PSU is 12V, right? Somehow, I was under the impression you had gone with 24V but, reading back a few messages, I now think it is 12V. If the 1R5 resistors are wired in series, current through the circuit will be 12V / (4 x 1.5Ω) = 2A. Total power will be 12V x 2A = 24W but, across each resistor, it will be 1/4 of that (6W). That would leave enough safety margin for 15W resistors. If the PSU is 24V then it will not work as that will require resistors rated for 24W+.
Measure twice, cut once, right? Please excuse my top quality photoshop skills, but I just want to make sure I'm wiring this up right. Connection type 1: This is the way it was originally wired up, but I think i'm correct in thinking that's parallel. Connection type 2: Fairly sure this is the way i should be wiring it up? This is just to make sure I dont fry something. Bare in mind that I'm using 4 x 2.2R resistors, rated for 15W, so I'm not sure which of those two ways I need to wire these up.
With 2R2 resistors, if wired in parallel from 12V, they'll each let through a current of 5.45A (12V / 2.2) and dissipate over 65W (12 x 5.45). Not something you would like to try with 15W rated resistors and not even something your PSU could handle. Wiring all 4 in series would work (in the sense neither the resistors nor the PSU would run serious risks) but yielding a very modest addicional power over your current config (+16W against your current 122W). Better use the 1R5 ones (for +24W). BTW, what are your current resistors rated for? I can't make it out from the photo but they don't seem to be large enough to be THS50...
So here's the resistors on offer. Old: 4.7R Arcol HS15 series (rated for 15W, so I'm puzzled as to how they worked in the old config!?) New1: 2.2R (these http://radionics.rs-online.com/web/p/pa ... rs/7547708 - although oddly, the page says 8W, but the packaging says 15W.) New2: 1.5R (these http://radionics.rs-online.com/web/p/pa ... rs/6150325 ) So you reckon I should go with the 1.5R and wire them like diagram 2 above?
Wow! Running 15W resistors at over 30W is not for the faint hearted, is it? Of course, they are well heat sinked (a large slab of aluminium) but still, I would not feel very confortable in the long run. The heat sinking also explains the discrepancy between RS specification (8W stand alone) and the datasheet's (15W with proper dissipation). As for my suggestion, and for a more immediate solution, I would leave the current resistors as they are and add the 4 x 1R5 (wired in series) for a little bit extra heat. For a more permanent solution, I would replace all by 4 of these (or similar), wired in parallel. For better heat distribution, I could also go with 6 x 4.7R. Any more and a new PSU would be needed.
Hmmm, so what about the 4 x 2R2 in series for now? I'd get a little more heat, right? I only need another 5 or 10 degrees.
That's not very good. Should you wire the new ones as the 4R7 were, you'd be running them way past rated power and, more importantly, your PSU couldn't handle that much amperage (neither, I suspect, the wires). Wiring them all in series will not work at all. You'd be dropping total power from more than 120W to about 16W. At this point, you'd better go back to the old configuration and try to find some other way to get those elusive 5ºC back. Perhaps trying to isolate the underside of the aluminium plate (a few layers of kapton tape?) and placing a towel over the bed while it's warming?
Well crap. Ok so then I need to figure out a solution that's cheap and won't leave me waiting for ages. so what about a nichrome setup? Could I somehow mount it to the underside of the aluminium? Would I get enough heat? Or would I be better off with 4x the correct power resistors?
Ok, so I now have 0.375mm nichrome at 4R7 per metre. So I figure I probably have a few extra amps to spare to maybe go parallel on this in an effort to get a temperature range of 90-100. So any suggestions on how I should divide up lengths in terms of resistance? Like # lengths of # resistance in parallel for example?
