Heated chamber configuration

Th0mpy

Hey everyone! I'm working with a Stratasys and migrating to a Duet. One issue I'm having is getting the enclosure heater working properly.

The heater works, but, the thermocouple is on the return air so there's a significant delay between the heat coming on and the return air temperature starting to move in the right direction. The result is that we get an alarm.

For testing purposes, we strapped another thermocouple to the heating element itself and this does work, however little control over the air temperature in the chamber.

Now to my question... Is there a way to interlock the return air temperature and the heater core temperature to have two points of control? What I'm thinking is that we could have two set points, one for the heater core (let's say 100c) and the other for the chamber temp. The chamber temp would energize the heater to bring the chamber temp to the set point while the heater temp would limit the core itself.

Does that make sense and is that even possible?

infiniteloop

@th0mpy said in Heated chamber configuration:

Does that make sense and is that even possible?

Yes, of course. To give you an idea, here's an excerpt from my own config.g:

; Setting up the chamber heater:
M308 S3 P"duex.e2temp" Y"thermistor" A"Chamber PTCs" T100000 ; sensor 3: direct thermistor on heater #3 (PTC type)
M308 S4 P"duex.e3temp" Y"thermistor" A"Chamber Top" ; sensor 4: chamber top sensor controls heater
M950 H3 C"duex.e2heat" T4 ; heater 3 is chamber heater, uses temp.-sensor 4
M307 H3 A11 C900 D30 B1 ; define heater model parameters manually
M141 H3 S-273.15 R0 ; heater 3: initially 0 degrees, off

; Adjust chamber heater fault detection:
M570 H3 P300 T25 ; allowed deviation before heater fault: < 300 secs, ± 25 degrees

; Connecting fans to the chamber heater:
M950 F3 C"duex.fan3"
M950 F4 C"duex.fan4"
M106 P3 L0.2 X0.7 T40:180 H3 ; blowers #3 and #4 are thermostatically controlled by sensor #3
M106 P4 L0.2 X0.7 T40:180 H3

; Protect chamber heaters against overheating:
M143 H3 T3 A2 C0 S150 ; shut-down heaters temporarily if exceeding 150 degrees

As my heater maxes out at 300 W and the chamber top sensor is far away from the air stream, I had no chance to auto-tune the system. So you can't simply take my values.

Of course, you have to adapt this and many other details to your own setup …

Th0mpy

@infiniteloop Cool, thank you for that! Let me break that down a bit over the next couple days but I think it makes sense.

Th0mpy

@infiniteloop Oh, one question. What firmware version are you running?

infiniteloop

@th0mpy said in Heated chamber configuration:

What firmware version are you running?

This version needs RRF 3.3 or higher, but the initial config ran under RRF 2.5. Currently, I am at 3.4.0.