I'm printing that hot because of splitting and peeling. Any cooler and I can't get an inch off the bed without the part destroying itself. Some parts have lost their head halfway through (which can be a little traumatic for young children watching their favourite cartoon hero get printed, no more toys till I get it right more)... I googled a lot and the sugested fix helped a lot. Print hotter and faster. Makes sense too when you think about the bondage, thermal transfer and cooling rates etc.
I am still looking into improvements here re: enclosure, heat lamps etc. Still need to dummy load my ATX so looking at 5v constant current solutions...
It may also be bad filament, it was nearly half the price of the cheapest ebay filament, so I got 8 kg... May as well work out how to use it.
It wont come out consistently at 240. 250 is the min temp it will extrude smoothly at. 260+ for printing. Thats heat block temp. I have no idea what the actual temp in the melt chamber is, but likely a lot lower. The thermistor is out buy quite a margin, nearly 10%. so programmed temp is around 240-250. 250 via thermistor 250-285 via k probe. Depending on where and how you measure.
No enclosure as such, but efforts have been made to minimise drafts. Room temp is 20-30c most of the time. Got down to 18 in a storm last night. Had some poor layer adhesion on a print that was set to 270 as a result. No warping of splitting, but a few bits broke coming off the bed.
I don't think its actually extruding that hot. Thermal transfer into the filiment seems fairly slow. I'd guess its under 0.2 w/m2k for abs? It passes heat even slower than epoxy... plus I have measured huge variations around the extruder. ~ +/- 15c
Its a cheap Chinese hotend. I'm printing fairly fast. 80-100 perimeter, 50%outer perimeter. 120 infil, 50 solid infil 70-80 bridges.
I can go slower and do need to drop temps if I do, but it prints badly due to inconsistent extrusion and warps and splits. High speed and high temps seem to be the go. The speeds I have have been found from the last 2 weeks of full time calibration printing following various online guides.
If I run over 285c the nozzle boils the surface on slow top infill (less than 30mm/s) and it gets blocked a lot if it stops extruding. So 260-280 seems to be the range Under 260 is terrible. Heat tower is on my too print list.
ie I know this is not recomended temp, but trial and error (lots of error) led me here...
3mm filament
0.4 labelled nozzle extrudes into air at exactly 0.5 at 270c.
Z pitch is claimed m6, 1mm per rev, measured 1.0565. Although that was with missed steps so need to re-check it I think.
I might still have a 3m length, should check it over that length turning by hand.... Will be no worse than the last Tesla Coil I hand wound...
The bed is probably up the wrong way.
I was confused as to how it was supposed to work when it arrived...
Seemed to make sense to put the hot bit where the heat needs to be... I only recently found out about the aluminum, which solves the mystery of the changing hole spacing with thermal expansion... I knew fibreglass PCB didn't normally grow that much!
Not a big fan of PCB heatbeds. Been looking out for a good ceramic tile for ages...
It has 2 layers of kapton on it. Because I am worried the traces will get ripped off by the abs juice, or that I will slice it in half with my Nakiri knife scraper (basicly a large straight razor for peeling veggies [
s-media-cache-ak0.pinimg.com] I can shave well with my one, its very sharp, I cut tomato by hand at 0.5) which I need to overcome the ABS juice that I need to use to overcome the warping.... Its a whole chain of stuff waiting to go wrong lol.
I'm good at laying the tape with no bubbles so its hard to see. I'll try it with board the other way next time I need to change tape.
I also have a 5v supplementary heater which I documented for peer review in the developers section of this forum [
forums.reprap.org] So I get some nice warm air drifting up and the bed never cools below 40c if the ATX is on. Its a great mod for those with ATX!
I have a fan. I think I need to change it. It blows way too hard. Enough to stop the hotend getting over 150 at 100%. No idea what CFM it is. Probably out of a Plasma TV. I have a funny setup there. Pics will explain better...
So the fan mostly stops the hotend getting too hot and blocking above the heatblock/nozzle. The bit of soda can air flow divider is a version0.1 design. I have a v1 planned. It will use the Coanda effect to get air to the leeward side of the print as well as the blower side. as well as better insulating the hotblock. I'm only diverting a tiny bit of air below the nozzle. If I wet the back of my hand I can just feel it 5-10mm below the nozzle. A dry hand can barely detect airflow at 1mm below nozzle. More than 10mm below the nozzle and there is airflow, but its warm air from the bed.
Obviously this is tunable at the deflector and the fan pivot. (that fan mount was printed with a hand made 1mm nozzle and overstepping z, not bad if I do say so myself) So I can print with no air on the print surface. Its helps with the bridges though.
Normal fan speeds are from 15% to 30%pwm. Over 30% for long cools the hotend and a kill command is issued. I have been bridging at 40% with no issues.
Bed normally runs at 130. Its thermistor is better. 130=130... I was running lower but the heat helped with the peeling etc. I just have to let it cool below 110 to get parts off or they can warp a bit. The big fan is helpful there. I have a Cool bed button in pronterface....
And I've done it again. A quick reply turned into a small novel... Hope I got all the relevant info in.