Below is a failed attempt to build a lid accessory that provides automatic Chamber Heating to reduce ABS/ASA warping, and that includes a beefy Recirculating VOC+PM Filter to cut down on hazardous fumes.
It uses standard components (heater, external thermostat, filters...) and mostly requires just woodworking skills. Although designed for a Bambu Lab P1S, the base can easily be adapted to other printers that also have a removable top lid: Creality, Qidi, Voron...
However, I consider this build a failure as it is unsafe due to electrical and fire hazards, and as the fan does not work reliably past ~55°C.
Bottom line & learnings: a standard PTC room heater is not designed to handle an ambient temperature much beyond 26°C (80°F). So, to hit a 60°C (140°F) chamber temp, I had to disable both its user and safety thermostats. Then its 12v fan kept shutting down after a few minutes at 55°C, so it was replaced with a 110v 85°C high temp fan. Also, the heater's plastic casing was never designed to safely operate at high temp. Finally, the tip-over switch had to be disabled. In other words, a ticking electrical & fire hazard 🠚 DO NOT attempt such unsafe modifications ⛔
Nonetheless, sharing this fail might still be helpful for some people out there with similar ideas, who do not realize the pitfalls yet ? Hopefully, someone can learn from this experience, or do much better / safer.
In the meantime, I am now designing a completely different version that can be 3D printed and that, hopefully, will be safe and reliable. More in a coming post.
But for now, happy printing to all !
Why ?
Heater: because printing long / tall ABS or ASA functional parts with solid walls without warping or lifting from the bed requires a chamber temp of ~50 to 60°C (along with proper chamber preheating and part cooldown profiles). All such prints initially failed, with excessive warping or lifted corners, until I experimented with a heat gun and got a high and stable chamber temp. Finally resulting in perfect parts, similar to the ones shown at the end below.
 |
| Large / tall ABS prints in a non-heated chamber... |
VOC & PM recirculating scrubber: because FDM printing emits toxic fumes and our nose is a very poor pollutants detector. Heck, Benzene, a known carcinogen emitted when 3D printing, even smells sweet. And even PLA emits toxic substances, contrary to popular belief. More here: 3D Printing Fumes are Toxic (sorry!)
Concept
The air is pulled from the inlet filter box, goes through the heater, and exits back into the chamber via the exhaust box.
The heater is controlled via an external thermostat whose probe was placed in the inlet.
The heater's fan was replaced by a 110v 85°C fan (specs on digikey), wired with its own 110v plug so as to stay on and keep circulating the air, independently of the heating element now controlled by the external thermostat. That allows for a filtration-only mode if heating is not needed, like when printing PLA. Or, when heating is desired, it ensures that the heater's casing is continuously cooled to avoid developing hot spots.
However, for safety reasons, this post does not describe the electrical modifications made to the heater. Not only is 110V lethal, but some mods would not pass safety standards, and the device was not designed to work at 60°C in the first place. Do not attempt to copy. Instead, possibly look into suitable high temp heaters out there.
Build
The wood elements were cut out of plywood, as shown in the pic above.
2 coats of epoxy were applied to reduce the amount of outgassing by the plywood as the air in the exhaust box probably reaches ~100°C. Plywood glue at such a temp outgasses badly, and smells horrible. Ask me how I know... 😅
That too was a fail though as the epoxy used (basic 1gal can from Home Depot) was more than a year old and quite past its best date. So it never fully cured and keeps emitting a nasty smell, resulting in a VOC filter accessory that is an obnoxious VOC emitter...
Inlet box:
HEPA filters installed, ready to hold the fabric bag that contains the 3lbs of activated carbon:
Exhaust box lined with 5mm foam aluminum foil for 3D printing heated beds, to limit heat losses and avoid cooking the plywood:
Bottom painted white to reflect light inside the chamber. Note the 8 M5 T-nuts that hold the inlet & exhaust boxes, and the 1/4" soft foam half-round weatherstrip around the perimeter that ensures a tight seal with the printer's top rim:
External thermostat's probe in place in one of the inlet holes. It is also visible in the pic above.
To ensure a tight seal between the heater and the inlet a basic white foam weatherstrip was used. For the exhaust though, since the hot exit air temp might reach ~140-180°C at the grill, a 1/2" wide 1/4" thick (12x6mm) high temp 204°C (400°F) silicone foam strip was used (orangey strip).
Top view of the whole shebang:
Results
Well, it did work for a while before the fan started acting up. The chamber reached 55°C at the start of the print in the following conditions:
- 750W(*) heater setting
- Preheated bed at 100°C for 15', fans OFF (P1S bed @ 110V draws about 250-300W)
- 16°C (60°F) room
Had to dial the external thermostat back 5°C though, as after 30' of printing the temp had reached 65°C.
The result was a perfect 5 hour ABS multipart print with no sign of warping or lifting. Which was impossible before, as the parts below are very warp & lift prone due to their length and an extremely thin leg running the whole length with a rim only 2mm large (circled):
However, I couldn't tell if it made a difference on VOC emission in the room as the Bambu Lab ABS filament is virtually odorless, and as the uncured epoxy smell was still strong (update: it has finally almost disappeared after 2 months).
Anyway, in the end, yay for a recirculating chamber heater ! Just have to come up with a completely different design now, that is safe and reliable. Piece of gateau...
(*) Note that the actual power was much less than 750W at 55°C. Indeed, since it is a PTC heater (positive thermal coefficient), its ceramic elements' resistance increases significantly with temperature. Resulting in a much lower power output. This is a big plus for safety, but can render a heater ineffective when trying to heat a space past human comfort levels.
Hence the need to still cover the printer with a heavy coat / blanket to reduce heat losses at high temp as, at that point, the PTC's power output is drastically lower. The following graph demonstrates that well. Extrapolate what's left at 55°C...
 |
| Power-vs-Temp of a 1500W room heater with active fan |
This is why many people who try the small flat 200W PTC heater from Amazon that fits inside the wall cavities of some printers get disappointing results. Those probably output no more than 100W at 50°C. That's not even close to what the heating bed itself can output. Heck I even tried a mini 500W PTC room heater from Amazon at 21°C and the air temp 1" away from the heater's grill was not even reaching 50°C. This is never going to raise a whole printer's volume to 50-60°C.
Digression: that's
also why I ripped out the PTC heater in my van. Worked well up to ~14°C (57°F) but
was pulling less than 60% power beyond that, despite high speed
airflow.
I wish that the small 300-500W NiChrome coil heaters from back then were still widely available. Those work far better past 25°C ambient. Am now playing with a 400W coil-based hair dryer, we'll see...
Comments
Post a Comment