Extruder preheat time

Hello! I would like to know how long does it take your extruder to reach its temperature? Maybe I need more insulation, because it take my extruder about 1hr to reach its temps (230°C for ABS). Or is it normal?

Thanks!

My hot end (the standard "Geared Extruder Nozzle" with 6.8 ohm resistor, which draws about 1.8 Amps / 20 Watts at 12 V - see: [julianh72.blogspot.com] ) gets up to temperature in a minute or two. (I have never timed it, as it happens quite quickly.) I don't have any insulation, other than wrapping the whole assembly in a couple of layers of Kapton tape to keep the wires etc in place.

It sounds to me like you might need a lower resistance / higher wattage heating element.

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Follow my Mendel Prusa build here: [julianh72.blogspot.com]

I use the J head nozzles from Here they heat up very quickly 1-2 mins tops

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Experimenting in 3D in New Zealand

Finally, I can't get past 178°C. I use this block heater : [mixshop.com]. What I think can cause this problem is that my resistance is not ''fixed'' in with epoxy or fire cement, but is just inserted in with a layer of Kapton tape around it to make it fit properly...

You should use aluminum foil instead of kapton tape hold the resistor inside the block.

Also, what are you using for insulator? Perhaps it's drawing too much heat away.

My insulation is all amde with kapton tape. Thanks for the aluminium foil idea! I'll try it right away!

I use the exact same heater block from mixshop. What i did was put thermal compound between the 6.8 ohm resistor and the block itself. It takes roughly about 2-3 mins and its at 230C

I was referring to the thermal insulation between the nozzle (hot end) and the extruder (cold end).

ECSuyu Wrote:
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> I use the exact same heater block from mixshop.
> What i did was put thermal compound between the
> 6.8 ohm resistor and the block itself. It takes
> roughly about 2-3 mins and its at 230C


What kind of thermal compound are you using?

That's why I moved to the J head as it's one piece

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Experimenting in 3D in New Zealand

Hey! What about CPU thermal paste? Would that be a good idea or is it too liquid?

it all depends on which one you use some CPU thermal compound are liquidy while others are more paste like. Im using the arctic silver 5 it works well

Soooo I just wasted 12$ on a bucket of fire cement... My extruder can't get passed 209C. My power supply is 17A and should be sufficient, but I just can't reach the temperature. Is there a way to increase the current in the resistance? Like connecting it to both extruder power output instead of just one? Thanks for your help, I need it!

do you have a fan pointing at the hotend? mine which is exactly the same can push well above 250C. If I have a fan which isnt directed at the cold it the heater tops out at 230-235. with the air directed only at the cold end it again reaches anywhere I want it to.

make sure in the firmware you have the 100K thermistor selected, as well check to see if your 6.8ohm resistor has room to wiggle in the hole drilled for it. It should be snug but not super tight. If its not snug the heat wont transfer well onto the block so thermal paste or aluminum foil works to fill the void. That setup works well, what you could do is also put kapton tape around the block. I have 3-4 layers going around the block to help insulate it.

EDIT, just re-read your post and saw you used fire cement, was it only for holding the heater in place? Did you make sure the heater has good contact with the block before fixing it with the cement?

Edited 1 time(s). Last edit at 11/18/2011 07:43PM by ECSuyu.

Post a photo of your hot end so that others can help you figure it out. I suspect that you're losing heat through your thermal insulation between the hot end and the extruder.

I coated the resistor with the fire cement to make sure that it has a good contact with the heat block. I've tried before with aluminum foil, but didn't change a thing. And no, I don't have a fan. 100K thermistor is selected in the firmware.

I just tried to connect the resistor to both extruder power output, and it doesn't change a thing.

I'll try to cover it with several layer of Kapton tape.

Edited 1 time(s). Last edit at 11/18/2011 08:01PM by Atfer.

I would echo brnrds suggestion, try posting a photo of your extruder it'll give us a better idea of whats going on. Also make sure the thermistor is in contact with the heater block not just free floating in the hole as well. And just a question what is the ambient temperature? though it shouldnt matter.

I'll post a photo soon enough, but my block heater isn't even on the extruder, I make my test with it hanging on its wires. But maybe there is worth mentioning : The wire that is soldered on my resistor is a nichrome wire, monostranded (is that a word?) When I start the heat, the wire become really hot, and not because of the temperature of the resistor. Maybe one strand of wire isn't enough for the number of watt? I have some finishing to do with me extruder and then I'll assemble it and take a picture. Thanks!

It worked!!! I change from monostrand to multi stranded wire and it preheat to 230 in 2-3 min!

You should use copper wire with high temperature insulator like teflon, silicone or fiberglass, not nichrome wire, to connect to your resistor. By adding the extra resistance from the nichrome wire, you're lowering the current, hence not enough power to heat your nozzle.

Edited 1 time(s). Last edit at 11/19/2011 01:52AM by brnrd.

I encounter the same issue with my prebuild reprap... finally i've found the source of the issue... it was my temp sensor... the internal temp was a lot more than what the temps reading show. I've melt my PEEK insulator!!! lol each time I was waiting about an hour to reach 210C and the printer as difficulty to keep the temp to it during extrusion... and all my part has a small burn odor...

I dont know if this is your issue but my experience is too similare to your situation...

Regards,

Stonedge