The back wall of the printer is a metal one-piece and there is no special top piece that carries the chamber fans.

Oops, you are right, of course. I got misled by the folded metal and the cable cover -- and apparently my memory sucks, I only built the kit a three weeks ago...

So re-using the two fan ports as air inlet and outlet respectively is probably the only realistic way to go.

Posted by: @jurgen-7

Posted by: @brian-12

I think I'll replace the upper acrylic rear panel with a 3d printed one where I can recirculate the air back into the printer.

There is no acrylic panel in the rear, it's all sheet metal. But the upper section (which carries the chamber fans) is indeed a separate piece, attached by a few plastic rivets.

Maybe you could even use the original part, using one of the two fan grilles for pulling air out, the other for pushing it back in? If you also want to print PLA and PETG occasionally, you could make the filter backpack removable just like Prusa's design. (With "keyhole" slots that go over four screw heads on the back plate.)

I'm wondering whether you still need a little bit of airflow pulled out of the chamber via the filter and blown into the room. If you set up your airflow for pure recirculation, I would expect some unfiltered air to escape via the various slits in the enclosure. Enforcing a slight flow where air is pulled in via these slits may be required to reduce VOC smell. 

That's good to know.  I was assuming it had panels like the sides.  Your idea is interesting.  I'll have to wait and see when the machine arrives.  

I think your right that some VOC's might leak out, but in my experience it's very minimal.  I don't smell anything even when printing ASA.  I also have an ERV in my printing room so there is always plenty of fresh air. 

Hopefully it'll arrive soon.  I was batch 1, but this filtration system has been holding the order up.  Had I originally known that Prusa would have designed it this way I probably would have just used the Filtration system from the original enclosure and modified it. 

I think I'll replace the upper acrylic rear panel with a 3d printed one where I can recirculate the air back into the printer.

There is no acrylic panel in the rear, it's all sheet metal. But the upper section (which carries the chamber fans) is indeed a separate piece, attached by a few plastic rivets.

Maybe you could even use the original part, using one of the two fan grilles for pulling air out, the other for pushing it back in? If you also want to print PLA and PETG occasionally, you could make the filter backpack removable just like Prusa's design. (With "keyhole" slots that go over four screw heads on the back plate.)

I'm wondering whether you still need a little bit of airflow pulled out of the chamber via the filter and blown into the room. If you set up your airflow for pure recirculation, I would expect some unfiltered air to escape via the various slits in the enclosure. Enforcing a slight flow where air is pulled in via these slits may be required to reduce VOC smell. 

It's a long video, but to sum it up this printer has a door that opens up when printing PLA or PETG similar to the manual door on the Core One.  This was causing his prints to warp.  He overrides the door to keep it closed and the prints turned out perfect.  

Based on this I just plan on redesigning a circulating system when the printer arrives and I can measure the panels.  I think I'll replace the upper acrylic rear panel with a 3d printed one where I can recirculate the air back into the printer.

https://youtu.be/sYN-dwEzZQ8?si=L7Hp5J942DxP456M

Posted by: @kachidoki.

 Regarding the filtration, I am doubtful that the chamber could stay hot with an extraction, even minimal. High temps are barely reached with the chamber fans totally off. But who knows?

Agreed, that's why I want to recirculate the air vs. expelling it.

Posted by: @antimix

I am printing on my MK4S in a temporary box I built using an IKEA Lack, an Ikea seat, some cardboards and plastic bags, some scotch to connect to a tube that expels the air outside the window through a hole.

In one month of usage, I had zero problems, either printing PLA and PETG. I measured the highest temperature inside the box as 35° C. This never created any clogging issues since it is still too low. The air is really few bars under normal pressure (I see the lining envelopes just curling) since it is controlled by a a big suction PWM Fan. I realised that the fan is really oversized, and I must keep the PWM level to 1 of 10 not more.

So this is not a heath chamber, since the suction introduces cold air from any leakage of the build (it is not air tight) but considering that there is no heating module other than the bed  (when it prints PETG is 80°),  the motherboard and the power supply (I did not remove anything), having around 40° it is not bad.

In few days I will complete the build of the final box, and I will install the printer in it, removing all the temporary parts.

For me this setup is ok to be used with the MK4S.

Now to the CORE One:  ideally, if I would put the same suction tube on the CORE One, I should have the same results. Opening the Core One top lid, will increase the entrance of cold air.

- But what happen when printing ASA or ABS on CORE One with such configuration ?

I think nothing. I looked at the PRUSA Air filter and the quantity of air that is extracted by the filter may be really minimal, so I could just put my tube over it, so that the air (that should be more or less already filtered) will be expelled from the window. No fumes at all.

- What about the Hot Chamber capability of the core One ?
It seems to be very poor. I have seen videos where after half an hour of heating, the internal ideal temperature is still not reached, and the printer shutdown in time out! 😮  I don't think they advertise the Core One as a Heath Chamber printer.

Let's see when I will receive the kit.

Regards

Im also quite worried about the Core Ones heating capabilites, since the printer need to start from 8 degC half of the year when my garage workshop is cold. and its alot of steel mass that needs to heat up, my mk3s+lack heats up fast and works well with all type of materials, but its a small volume and not much metal in there. Im already planning for a chamber heater to help it work out, we´ll see after a week or so when my printer is built how much thats needed. I havent had any feedback from people having it in colder temps.

The air is really few bars under normal pressure

You mean millibars I guess. The atmospheric absolute "normal pressure" is around 1 bar.😉

- What about the Hot Chamber capability of the core One ?
It seems to be very poor. I have seen videos where after half an hour of heating, the internal ideal temperature is still not reached, and the printer shutdown in time out! 😮  I don't think they advertise the Core One as a Heath Chamber printer.

The CORE One is a passive heated chamber. I reach 57°C with 19°C ambient temp during a PC or PC-ABS print. This happen with the heatbed pushed to its max temp. One thing important to know is that the heatbed must be at the top of the chamber to reach this temperature. When printing, the temperature will progressively goes down while the bed moves down.

If you simply preheat the machine without taking care of the bed position, you will never reach this temperature. But if you let your sliced file do its job, the printer will home and wait to reach the minimal temperature defined for the materiel (let say 40°C) and then start to print. While printing, the temperature increase up to its maximum, until the bed move too far down and then the temperature start to decrease.

This is far from ideal, this is slow, but the good thing is that this allow the CORE One to print ABS with an average power of 150W only.

 Regarding the filtration, I am doubtful that the chamber could stay hot with an extraction, even minimal. High temps are barely reached with the chamber fans totally off. But who knows?

In one month of usage, I had zero problems, either printing PLA and PETG. I measured the highest temperature inside the box as 35° C. This never created any clogging issues since it is still too low. The air is really few bars under normal pressure (I see the lining envelopes just curling) since it is controlled by a a big suction PWM Fan. I realised that the fan is really oversized, and I must keep the PWM level to 1 of 10 not more.

So this is not a heath chamber, since the suction introduces cold air from any leakage of the build (it is not air tight) but considering that there is no heating module other than the bed  (when it prints PETG is 80°),  the motherboard and the power supply (I did not remove anything), having around 40° it is not bad.

In few days I will complete the build of the final box, and I will install the printer in it, removing all the temporary parts.

For me this setup is ok to be used with the MK4S.

Now to the CORE One:  ideally, if I would put the same suction tube on the CORE One, I should have the same results. Opening the Core One top lid, will increase the entrance of cold air.

- But what happen when printing ASA or ABS on CORE One with such configuration ?

I think nothing. I looked at the PRUSA Air filter and the quantity of air that is extracted by the filter may be really minimal, so I could just put my tube over it, so that the air (that should be more or less already filtered) will be expelled from the window. No fumes at all.

- What about the Hot Chamber capability of the core One ?
It seems to be very poor. I have seen videos where after half an hour of heating, the internal ideal temperature is still not reached, and the printer shutdown in time out! 😮  I don't think they advertise the Core One as a Heath Chamber printer.

Let's see when I will receive the kit.

Regards

Posted by: @antimix

Hi,

I ordered it at the beginning, and I suppose this is the cause of the kit shipping delay.

I understood from the PRUSA Enclosure, that the Air filtration take the air from inside, push it in the HEPA & Carbon Filer, and expels it again into the printer.
So the concept is clean the air inside the box.

However since the box is not air tight, there is good opportunity that the fumes can exit from the box and go in the room when they are not yet filtered. This may not be noticeable with PLA or PETG, but surely with ABS.

This is the reason why I will apply the different method, where the printer is at constant air depression, and nothing could exit except than from the vacuum tube.

So I will probably not install it, and I will connect the air gaps grids directly to an air tube that goes outside through a hole in the window, exactly as I have done on my new built Custom Ikea Lack for MK4. I will wait to receive the CORE One kit, and mount the printer, and then I will design the part.

I discovered to be sentisive also to PLA and PETG fumes, so I had no other chances, since I print in the room where I live and I have no other spaces.

Regards

Recirculating air inside the chamber actually works quite well.  I've been running all of my printers this way for 2 years now and there is no smell outside the enclosure even when printing ASA.  I actually prefer this method because anything else involves bringing in outside cold air, which defeats the purpose of having the enclosure. 

I don't think recirculating leaks any more air than it would if there is no fan. This is because your not actually creating a positive pressure inside the enclosure by only circulating the air.  If you were drawing air from outside and blowing it inside the enclosure then yes , it would cause the particles to be pushed out.  However that's not the case here. 

Like @jurgen mentioned the core one looks to work differently blowing air from inside to outside the enclosure.  I'm skeptical on this and at the moment are planning to redesign it to blow the air back into the enclosure via one of the top or side panels.