Pushing my heated chamber temperatures to the limit
I built a heated chamber for my UMO+ because I wanted to print ABS just perfect (and all the other materials better as well). Some research in the internet figured out that a chamber temperature at 90°C is fine for ABS (in general the HDT for any material). So my goal was to build a heated chamber that reaches temperatures of 90°C.
My UMO+ is equipped with a water cooled hot (cold) end, the stepper motors and electronics (of course a Duet ) are mounted outside and all plastic parts in the chamber are printed with Extrudr's GreenTec PRO which has a HDT of 160°C. So a pretty good starting point for building a heated chamber.
My enclosure is out of polycarbonate and everything is really good sealed. There are basically no holes anymore.
The chamber is heated with a 500W 230V PTC heater plus the heated bed.
I have installed 3 temperature sensors to monitor the temperature at different places inside. One sensor is at the bottom, one at the top and the third sensor is mounted under the bed which is responsible for the temperature control (bang-bang mode) of the 500W heater. The sensor under the bed is right in the lane of the chamber heater so it can measure the air temperature which comes out of the heater. And some measurement figured out that the maximum air temperature doesn't get higher than 106°C. So the 500W heater blows 106°C hot air inside the chamber. So the maximum chamber temperature theoretically can get as high as 106°C but it doesn't (of course not) - 74°C was the maximum (measured at the upper sensor; the lower sensor got me 69°C - bed temperature was at 130°C). So thats 16°C away from 90°C.
What can be done to reach 90°C? Some points I thought about:
- Exhaust fan
The 500W heater constantly blows air in, so the same amount of air has to get out somewhere. The enclosure isn't 100% air tight. Probably 99% or 98% - there are really small holes/gaps somewhere. If it would be 100% air tight the 500W heater wouldn't be able to blow air in. So I think a bit of leaking is fine and because of those holes/gaps I don't need an exhaust fan.
- Better insulation
This could be done with insulation material which I can put inside the PC-plates. But I think that only would bring me 1-5°C higher temperatures. And it's not pretty.
- Air circulation
I really would like to do this but I couldn't find any small fans that can withstand 90°C. But that would help a lot to get an evenly temperature inside chamber. Right now the bottom temperature is 69°C, under the bed it has 106°C and at the top it's 74°C hot. Does anyone knows small high temperature resistant fans?
I had to dismount my print cooling fans and switch to a berd-air pump because of the high temperatures.
- Mount the heater inside
This probably would be better but there is no space inside (only at the top) and I would need high temperature resistant fans.
- A second 500W heater
That's probably the best solution (together with an air circulation) to reach 90°C. I would mount it right above the first heater.
Any other ideas? Has anyone experience with building a heated chamber? Or some solutions to make the air circulating inside the chamber?
- Exhaust fan
I think you need to double-glaze it.
One sheet of PIR (polyisocyanurate) foam, a razor knife, some duct tape, and about 15 minutes could have you cooking PC and ABS prints like they're PLA.
I'm not sure of the need to go all the way to 90C, but if that's the target, foam insulation will help you get there. I'm not too sure about that kind of heat and a plywood enclosure, either. Plywood warps, and when you heat one side and not the other, I'd bet it'll warp very quickly.
My Gates belts are spec'd for operation to 85C. Common no-name Chinese belts don't come with any specs. Bearings and lubricants may not like that sort of temperature. It looks like you have some LEDs in there too. They definitely won't like a 90C ambient temperature.
We have a couple Stratasys printers from the 90s at the makerspace. They operate the enclosure at 70C for printing ABS and it works fine. I run my own printer a 45-50C and don't have any issues printing ABS.
Interesting to hear that a better insulation would be that much more effective. I think I will try these PIR sheets.
The new stratasys printers have a 90°C heated chamber and here is an article why it needs to be that high:
Of course 70°C will bring me an enormous increase in print quality, too but 90°C is said to be the optimum. Especially for large prints.
I know my UMO+ is still not the best printer to build an enclosure for it but I just want to try it. Thanks for pointing out the operation temperature for LEDs. As I read in the internet they only will shine less bright but they won't get damaged. Is that correct? Then I can live with that.
My Gates PowerGrip GT3 are rated at 100°C working temperature; that should be fine.
We will see how the plywood, bearings and lubricants handle the temperature...
For air circulation I thought about to install such fans:
Interesting link! I can see a lot of unevenness with low angle lighting in my prints and would not have attributed it to the chamber temperature. I see it with PLA, too. I've been thinking it's more a function of the part geometry and behavior of molten plastic as the unevenness disappears if you print a cone or other curved surface. Hmmmm.
I have a printer that is closed with clear PC panels on 3 sides and 1" PIR foam on 3 sides and the 450W bed heater is enough to bring the enclosure temperature up to 45C without additional insulation, when the ambient temperature is at least 20C. When it's lower, I tape a piece of the foam on one of the sides, right over the PC, and that allows it to reach 45C.
My larger printer uses 8 mm thick dual layer PC panels- the stuff that's commonly used for greenhouse walls- fit into the 8 mm slots in the frame which provide good thermal insulation and plenty of light transmission, but not very good visibility inside the machine. The front panels are clear PC sheet and I use a 500W heater inside the enclosure to get the temperature up for ABS printing. The bed has a 750W heater. It easily gets to 50C, but I haven't tried going higher as 50C seems to be adequate, and the extruder is inside the box, so I don't want the motor to overheat.
That fan looks like an impeller from a convection oven. Will you be putting the motor outside the box?
Sounds good with the insulation.
Yeah these propellers are designed to mount the motor outside.
I am also thinking of buying many mini DC motors with a long shaft and moderate speed, mount them just like the oven propeller (motor outside, fanblade inside) and stick self printed fanblades on them (like 50 mm ones). Two fans in every edge to get a good air circulation.
But first I will try the insulation.
This is what I'm using, but 45-50C is much easier to deal with. I'm probably at the thermal operating limit of the fan, but it's an industrial unit, not a PC cooler or hobby part.
Since this photo was taken I've added a heat shield for the Z axis motor. I'm going to add a cylinder of wire mesh to cover the heater and electrical connections to keep fingers and print debris away from the heater bar and electrical contacts.
@christoph13524 I read recently that it's easier to construct a 150-90-50 °C solution than a 150-50, i. e. to encapsulate an inner chamber by a middle layer, then outer.
There are some people who print PEEK, maybe you get hints from them also. They use a chamber of 80 °C (and higher, 200 °C).
Noctua fans can withstand temperatures up to 70°C according to the email support.
And all other common fans can be used up to those temperatures I think so. Depends on the plastic it consists of. As I see, your fan has an aluminum frame, so don't carry about your 50°C hot chamber.
I can basically put my enclosed UMO+ in another big enclosure but that is not what I want. That's way to complex.
I will see how the PIR sheets work. Maybe they will do the job.
Interesting to hear that a better insulation would be that much more effective
All is about insulation! You can't reach target temp because loss are too high regarding the input power. Reducing loss, and you don't need such high power.
If you have a infinite insulation, then, once heated up, you don't need anymore power to keep it hot ;o) Same as supra-conductive wires: no more Joule loss.
If you want a real stable temperature u need to have more isolation.
Make a hot airflow like a oven inside the inner chamber (heated one). Make that chamber isolated with some high temp material or use basic rockwool.
Next let cool air flow on the outer chamber to leave the outside of your printer cool so you can touch it.
We build a machine with 1m x 1m buildvolume and 200 degree chamber this way. Little bit more complex but for 90 degrees it's almost the same. If you need more help please contact me.
So I bought some insulation material and have installed it.
I didn't got the recommended PIR-sheets but some other 11 mm thick foam with quite good thermal insulation values which is permanently temperature resistant to 200 °C. This stuff was really expensive: 100 € for 2 m² foam.
I have isolated the top cover completely and the side panels. I really don't want to isolate the front panel because then I can't see anything
But the foam works really well. Now it got me a maximum temperature of 82 °C and the PC-panels are much cooler. That's 8 °C more than without foam.
But the thing is I only reached that temperature with a heated bed at 130 °C which is too hot for ABS. With a headed bed at 100 °C I only got a temperature of 77 °C. And it took 1 hour to reach that - so quite long.
Things I am going to do now:
Putting that magic foam everywhere I can. So also on the wooden panels and some other places. That will probably finally give me 90 °C with a heated bed at 130 °C. But with a bed at 100 °C it still won't.
Installing a second chamber heated above the first one. This will definitely give me my desired temperature and will drastically decrease the heat up time as well.
But I am still thinking about my first question in the main post: The thing with an exhaust fan and airtight chamber.
On the one hand the foam got me higher temperatures so an airtight chamber is like the requirement for a good insulation. On the other hand a real oven is blowing out hot air, too. It has to be like that because if not, you aren't able to blow hot air into the oven because of the air pressure.
As I said my chamber isn't perfectly airtight at the moment. There are really small gaps somewhere. And I can feel the hot air is getting out there. So is this good or bad?
The gaps are mainly at the side panels. Should I close them and install an exhaust fan at the very top? Then there is an air circulation from the chamber heater(s) at the bottom to the exhaust fan at the top.
Or is it probably more effective to just close the gaps without installing an exhaust fan?
Have you installed an exhaust fan @dvmourik ?
PS: Why do my uploaded pictures have some funky purple strips at the bottom? Is this a bug?
On the other hand a real oven is blowing out hot air, too.
I don't know about your oven... but for all the regular "kitchen ovens" I've ever seen the "hot air blowing out" is NOT from the oven cavity. It is from the layer that SURROUNDS the oven cavity, to keep the "outer" sheet metal cool enough for the whole oven assembly to be mounted in a wooden cabinet.
The oven cavity itself, is semi-air-tight. Not super sealed... but no fans or intentional leaks either.
I would try
- putting thin aluminium at the walls, so air warms up the aluminium, not the wood *)
- restrict air circulation, so temparature exchange is low (like in a boiler, where you leyer temparature zones). So less fans
- warm from the bottom, because heat climbs up
In my understanding you will not need to heat the heat bed any more then or only at the beginning to equate it with the higher air temperature.
*) I remember there is foil for human protection against undercooling. This could help reflect the heat.
@danal Thanks for pointing that out - makes sense. Then I will close the bigger gaps but won't install an exhaust fan.
@JoergS5 Aren't aluminium sheets more against thermal radiation and not isolation?
I thought about a better air circulation in the chamber to get a more even temperature. But first you need high temperature resistant fans and second I don't really need it anyway. My bottom temperature sensor gives me about 7 °C lower temperatures than the upper one. And that's ok for me. So there aren't any fans inside except the berd-air pump (is of course installed outside).
I have just ordered a second 500 W heater. In combination with the foam all concerns should be cleared.
Can't wait to see if this actually improves your prints.
- You will want LOTS of airflow with ABS in a 90C chamber. Basically ABS in a 90C environment acts much like PLA in a 30C environment — low warp but needs some help cooling solid. Stratasys printers use giant fans to mix the chamber air and blast the print at nozzle height with hot chamber air. This is pretty much optimal. (Don’t pipe in cold air, blow 90C air.)
- If you use a radial blower type fan, you can install the fan OUTSIDE your heater chamber, to pull hot air from a hole in the side of the insulation and then duct it back above the build plate. Yeah, the fan will have 90C air inside it, but the outside will be cool, so a 70C rated fan should work. (I think.)
- Or you can just buy better fans. Here’s an 85C blower for $26. https://www.digikey.com/product-detail/en/BFB0712HHD77/603-2092-ND
50db?! Dear Lord.
I thought about an berd air cooling system. Sucking in the hot air from the chamber and blowing it out to cool the part. But I am not sure if the berd air pump is able to withstand 90C hot air. Although the pump is mounted outside. Depends on the plastic the pump is made from. Anyone knows that? The manufacturer couldn’t answer me how hot the sucked in air can be.
berd air pump
You can 3d print your own like
and take the filament you want, which is ok for your temparature.