What is an enclosed chamber good for?

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robosmith

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Oct 12, 2015, 1:23:46 PM10/12/15
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What materials require it?

What materials print better with an enclosed chamber and what is the benefit?

Do you pipe hot air in? Or just keep it in?

Thermostatically controlled? Is that standard on the Dreamer?

Petr "Fogl" Ptacek

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Oct 12, 2015, 1:31:35 PM10/12/15
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1) Anything that shrinks as it cools. More it shrinks, more it helps to have heated chamber (shrinkage: Nylon > Polycarbonate > ABS > PETG > PLA).
2) Nylon, Polycarbonate, ABS
3) Having controlled heater inside helps.There is a thread on that topic somewhere. Cheap $15 personal heater stuck inside suppose to help a lot.
4) From what I heard, standard behavior of the Dreamer is melting in high temperature. You really want to have all metal guts on your printer if you do heated chamber.

Ryan Carlyle

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Oct 12, 2015, 2:10:37 PM10/12/15
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Basic rule of thumb, the optimal chamber temp to reduce warping is about 20C lower than the glass point of the filament. (For typical amorphous polymer filaments, anyway. Crystalline polymers are an entirely different story.) Less cooling = less thermal contraction = less warping stress. Plus, this puts the material in its "creep" range so warping stress can very slowly "shake out" while the part is printing, but without letting the part actually sag under its own weight.
  • PLA: Tg = 55C, optimal chamber temp 25-35C
  • ABS: Tg = 105C, optimal chamber temp 75-85C
  • Most PETs and nylons: Tg ~=60-70C, optimal chamber temp ~35-45C
  • PC: Tg = 150C, optimal chamber temp ~110-120C
Of course, when you run a heated chamber, you need LOTS of airflow to get the part to cool solid fast enough for good detail. 

Anyway, enclosed printers 1) avoid drafts and air conditioner vents that cause excessive cooling and 2) passively trap in some heat so you get a poor-man's heated chamber without violating Stratasys patents. 

Petr "Fogl" Ptacek

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Oct 12, 2015, 2:32:42 PM10/12/15
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Hmm, Nylon has Tg just ~70C. From some reason I thought it was much higher. Learning every day ...

Ryan Carlyle

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Oct 12, 2015, 6:37:42 PM10/12/15
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Nylon's a bit of an odd duck, it's still quite solid and retains its shape at the glass point. Just flows/creeps very, very slowly so you can't use it for structural parts at elevated temps.

robosmith

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Oct 12, 2015, 9:55:28 PM10/12/15
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So if I want to print with PC, what do you think of ABS, Nylon or PETG printed internal parts (carriage & extruder drive). Looks like ABS might work with a chamber at ~100C.
 
Does a chamber get that hot w/o an external heater? 

Petr "Fogl" Ptacek

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Oct 12, 2015, 10:13:08 PM10/12/15
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IMHO anything made out thermoplastic closed withing confined space and holding heaters is just pure madness. That being said, using materials well above expected working temperatures is probably ok for hobby machine.
If you print just PLA and may be PETG with open enclosure and without additional heating, ABS parts in the printer are probably fine.
Printing ABS or PC parts with ABS in the heated chamber is asking for trouble. Good example is Dreamer, which is known to melt ABS carriage during long prints.
PC parts in the heated chamber are probably ok in our hobby conditions.
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