Heated build chamber for 2X

[joe90]

Has anyone thought of, or added extra heaters to their replicator 2X to enable better ABS printing of large models?

I am thinking about adding some form of heater and holding the build chamber at around 70C

Any thoughts?

Thanks

[Clinton Hoines]

You shouldn't need a HBC for the Rep2X. I have a Rep1XL and I have no problems with a full build tray to height print (250mm tall)
It just need the fully enclosed windows and top exactly like they did for the 2X.

[Ryan Carlyle]

It's crossed my mind, but I'm not sure if it's worth the trouble. If you do want to raise the build chamber temp, I would recommend using insulation and a long preheat stage rather than more heaters.

During a tall and longish print (4-8 hours) on a stock R2x, my HBP surface is at 90-95C, internal air temp ~45C, unused extruder 55C,  active extruder 230C, and the printed thing temp varies from 85C near the build plate to 60C near the top layers. Which means:

• Your cooling block probably runs around 10C hotter than chamber temp
• The stock chamber runs around 20C hotter than room temp, which is actually pretty hot given that the chamber is "breezeproofed" at best
• Thermal conduction from the HBP to the plastic is the same order of magnitude as thermal loss to air (~65C plastic is about halfway between 90C plate and 45C air).

Anyway, one extruder plus the HBP is a fair bit of wattage. So you could seal up and insulate the build chamber, and it would get pretty hot without needing additional heaters.

But there are a number of issues with hot build chambers:

• Your hot end will have a harder time shedding heat, because there will be less temperature difference between the cooling block and the ambient air. That means you may get more heat creep past the thermal barrier, which can cause air prints. 
• Any plastic parts in the build chamber (Z-arms, X carriage, X ends, and so forth) will suffer an increased rate of warping/sagging. So those go aluminum. With the stepper motors and cooling block running hotter, an aluminum extruder will probably also be prudent. 
• Freshly-extruded ABS will take longer to solidify. That will probably hurt bridges and overhangs. Maybe now you need a blower fan pushing 70C air on your prints so the filament solidifies as fast as it would at 45C chamber temp.
• Maybe you need more heat sinks, bigger fans, and so forth. I don't know what exactly you'd need, but every change makes the gantry heavier and thus increases sag.

All solvable? Probably. It's just a lot of potential trouble.

[Jay]

Everything Ryan and Clinton said...

And...all I keep thinking is if you get ambient way up then you start inducing heat into areas that aren't supposed to get a lot of heat...such as the upper filament area.

I think (Kurt I think you mentioned this) that more expensive printers like the Mojo, which has a heated chamber, actually have most of the printing mech outside the heated chamber (??). They don't use a heated build tray either...they print on disposable ABS trays (??)

Cheers

Jay

[Kurt @ Gmail]

Hey Jay - sorry again for late reply - I don't always check my Gmail...

The Mojo - it has this kind of cardboard accordion structure at the top
of build chamber - thru which the print heads peek down thru. That keeps
the heat inside the chamber - but, still allows print heads to move around.

And - yes, the Build trays are indeed ABS. I actually chopped up a bunch
of them and put into a HUGE Jar & made a Large amount of liquid Black
plastic!

-K-

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