"Heated Chamber" idea for delta robot.

I was just looking over the Rostock Delta and is struck me that because the part is now stationary, there is a method that could be used to give a "heated chamber" effect, this could mean that we could finally print large parts in ABS.

The part could be printed in a walled bath and as the part is printed, hot fluid could be introduced around the part just below the print height. It has been suggested in other forums to try printing in oil, but this method keeps the printed surface just out of the fluid, so there would be no layer adhesion problems. There are a few problems I can see, but nothing that couldn't be easily overcome.

1) You need to accurately control the fluid height. This could be done with a float switch.
2) The 6 delta arms could hit the bath edge, but the arms could curve inwards a little to overcome this. Alternatively, you could use a slightly longer extruder insulator to help. This would also keep the extruder head further from the hot oil.
3) Danger of hot fluid. As the bath is stationary, this risk is reduced. You could use cooking oil and heat it to around 100 degrees c.
4) Keeping the fluid hot. You could put heaters in the side walls.

Comments welcome

Edited 1 time(s). Last edit at 10/26/2012 06:58PM by martinprice2004.

martinprice2004 Wrote:
-------------------------------------------------------
> I was just looking over the Rostock Delta and is
> struck me that because the part is now stationary,
> there is a method that could be used to give a
> "heated chamber" effect, this could mean that we
> could finally print large parts in ABS.
>
> The part could be printed in a walled bath and as
> the part is printed, hot fluid could be introduced
> around the part just below the print height. It
> has been suggested in other forums to try printing
> in oil, but this method keeps the printed surface
> just out of the fluid, so there would be no layer
> adhesion problems. There are a few problems I can
> see, but nothing that couldn't be easily
> overcome.
>
> 1) You need to accurately control the fluid
> height. This could be done with a float switch.
> 2) The 6 delta arms could hit the bath edge, but
> the arms could curve inwards a little to overcome
> this. Alternatively, you could use a slightly
> longer extruder insulator to help. This would also
> keep the extruder head further from the hot oil.
> 3) Danger of hot fluid. As the bath is stationary,
> this risk is reduced. You could use cooking oil
> and heat it to around 100 degrees c.
> 4) Keeping the fluid hot. You could put heaters in
> the side walls.
>
> Comments welcome

Why not just a encapsulated printer in hot air?
eddy

Or hot Argon?

Has this been tried before? I can imagine that this would reduce deformation
eddy
ps small resume: one is printing in a room where temperature is 10°C lower than the melting temperature of ABS. this is enough to solidify the plastic. After the printing is done, the piece is cooled down , it shrinks, but no deformation is happening as all is shrinking in the same way
ps could abs solidify if the delta t between the air ( or argon) and the abs is only 10°C? Should we need a fan to get rid of the heat?

Its the difference in temperature between certain areas of the part that cause the cracking. Industrial machines use heated chambers, so the part cools uniformly at the end of the print. For very large thick parts, you coudl still get cracking as the core would cool less quickly than the outer, but this is a known problem in metal casting and plastic moulding. You just design your parts with uniform sections.

I am not sure how hot you would need to go in order to stop cracking of very large parts. I imagine something around 100 deg C might be OK. Perhaps someone could chip in with the best temperature. The spec for plastic deformation of ABS is 98 dec C. This is why I suggested cooking oil as the flash temperature is way above this so it would be relatively safe and is cheap. It could drain back into a tank under the print bed when finished.

I don't really like the idea of hot gas as its expensive and would be stirred by the head moving over the part. You need the open top of the box so the print head can get in.

martinprice2004 Wrote:
-------------------------------------------------------
> I don't really like the idea of hot gas as its
> expensive and would be stirred by the head moving
> over the part. You need the open top of the box so
> the print head can get in.

Argon is not excessively expensive; it's commonly used in MIG and TIG welding. I suggested it because it is significantly denser than air (1.784 g/L vs 1.2922 at 0C. Argon still has a density of 1.304 g/L at 100C, so that's still denser than 0C air. There will still be some mixing, particularly when the head stirs the tank, but I doubt there would be a lot of leak.

Also, you do not need an open top with rostock. You just need an aperture for the filament and cabling to enter. Now, at 100C, that would not be good for the electronics inside the chamber, so it would take a bit of re-engineering in terms of the placement of the electronics.

I understand by your thinking that your method would be to envelope the whole machine. Unfortunately doing it this way would mean that all the robot arms and centre platform could not be reprapped as they would become unstable at 100 Deg C along with the part as they are made from the same material.

The reason I suggested a liquid is that the top of the machine could remain relatively cool compared to the part. You would get rising heat off the liquid, but this wouldn't be too much as the temperature gradient drops off quickly. The oil is not boiling as water is in a hot kettle for example.

Also if you were to seal the machine, you might as well use air...its cheaper still! Perhaps there is a way to shield the tool head with a sleeve or something to reduce the heat. I have seen industrial FDM machines with bellows to hold the heat in the chamber. These are usually cartesian machines though.

Would it be possible to mount a Rostock up side down and print not on the "floor", but on the "roof"?
It would only be necessary to seal the "upper" part of the Rostock (as hot air raises).
The main part of the arms could be in the colder lower part....

eddy
ps did anyone ever try to print up side down?

... Ed and Adrian showed upside-down printing some time ago, what didn't show any problems or flaws ...

---

Viktor
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The trick to heated chambers is to control the cooling of the part. If you've ever seen the insides of a commercial printer with a heated chamber they use wipers to isolate the hot and cold side of the chamber. All electronics and cabling are on the cold side. That being said a rostock type printer would be pretty easy to modify to fit that criteria with one exception, the hotend would need some type of active cooling to keep it and the filament tube cool. Lastly there can't be any printed plastic in the chamber but there is a solution if you mold the parts in high temp, stabilized epoxy/urethane. Smooth-on sells some under their task series and epoxy cast series but I've never used them but the epoxy one goes up to 177C which should give you enough headroom to be comfortable.