how to setup a hotend for directly printing metal and ceramic.

T3P3Tony

@lynnmt thanks for the detailed explanation of your project, incredibly cool to have identified and built a hot end with those capabilities.

Did you see the documentation here:
https://docs.duet3d.com/en/User_manual/Connecting_hardware/Heaters_tuning#setting-the-model-parameters-manually

And try calculating the values manually as described?

lynnmt

The reply function has returned for me after switching computers....

apologies for the extended delay in this thread.

I have not yet tried manually calculating the values as described.
I have some questions about the limits on the range of the parameters.

are there any limits on the heating rate parameter, and the dead time parameters?
like maximum and minimum values respectively, that the duet will accept?

dc42

@lynnmt the temperature is sampled and the PID loop for controlling heater temperature runs at 4Hz.

The limits on the heater model parameters are currently:

heating_rate/basic_cooling_rate > 0.1
dead_time > 0.099
dead_time * basic_cooling_rate <= 50
1.0 <= cooling_rate_exponent <= 1.6

HTH David

lynnmt

@dc42 is there any way to make it work at faster frequencies? and or to increase the frequency of measurement at the thermocouple?

my heater can heat and cool at ~1000 C/second, and may need to do this fairly often..
this is almost 250C degree of change in a 4 hertz update cycle.

I need at least 5-7 degrees C of heating/cooling precision at the heater during operation to ensure the metal in the hotend does not freeze/melt.

lynnmt

@dc42
when I run M307 per the docs,
https://docs.duet3d.com/en/User_manual/Connecting_hardware/Heaters_tuning#setting-the-model-parameters-manually

M307 H1 R1000 K300 D0.25 S0.1 V24

I get the error "bad model parameters"
are these values outside the possible ranges specified?

the command also fails as
M307 H1 R1000 C4 D0.25 S0.1 V24

soare0

@lynnmt External CAN temperature controller? This way you have control from gcode, and higher performance of controller.

lynnmt

@soare0
do you have a link to such a thing?
These exist?

dc42

@lynnmt your original command:

M307 H1 R1000 K300 D0.25 S0.1 V24

fails because K * D > 50. So reduce K or D to make it <= 50. I suspect the dead time of your heater is well below 0.25 (minimum currently supported is 0.1).

Are you driving the heater from a main board or from an expansion board?

lynnmt

@dc42

Even when i reduce the value to 0.1 it still fails. with the same "bad model parameters"

I am driving the heater from the main board.
it only draws about 40-60 watts of power.

dc42

@lynnmt this works for me for heaters on both main boards and expansion boards, using firmware 3.5.0-rc.3+:

M307 H0 R1000 K300 D0.1 S0.1 V24

lynnmt

@dc42
I appear to be using reprap firmware for Duet 3 MB6HC 3.3.
DSF version 3.4.6

The command M307 H1 R1000 C4:2 D0.25 S0.2 V24.0
also fails with the same "bad model parameters " error.

soare0

@lynnmt Yes, they are, but interfacing would not be trivial.
I worked with some, some years ago, and being straight chinese, it was a pain to use their CAN bus protocoi (as it was rather suggested than described). If you say you are 5 year old technical, then you may not want to do such gymnastics.
I would suggest that maybe an Arduino, with CAN and a thermocouple adaptor, may do the trick.
Maybe working from a DUET CAN interface board, would be better than from a mainboard? I think this is what dc42 wants to suggest.
Anyway, if your requirements are so ... harsh, regular PIDs may not be your best option (usually they are not designed for such high speeds, but probably some custom controller, wich... may be done on Arduino too, or on any other board like this.
I needed to do such stuff a long time a go, basically some ramped ON-OFF controllers, for fast precision control, but this is something needing to be tuned ... in house.
Normal fast thermoregulators, means 5samples/second. Super fast ones, maybe 40/sec, like these:

https://www.tc.co.uk/temperature_control/HA401.html

But the fact you can sample with 1ks/s, means nothing. and I find rather difficult to believe that you need such a speed.

dc42

@lynnmt I suggest you upgrade to 3.5.0-rc.3 then. I know we widened the allowed model parameters at some stage.

oliof

@lynnmt you really should be updating to 3.4.6 at least (I also would suggest leaving out the SBC which has no benefit for your current use).

lynnmt

@oliof
I am using the SBC to avoid having to network interface with the Duet.
my internet is...unreliable at times.

lynnmt

@dc42

can I actually do this upgrade if i have a Duet 3 MB 6HC V1.01A ?

dc42

@lynnmt yes, firmware updates can be applied to all production versions of Duet boards.

dc42

@lynnmt said in how to setup a hotend for directly printing metal and ceramic.:

@oliof
I am using the SBC to avoid having to network interface with the Duet.
my internet is...unreliable at times.

Duets don't need an internet connection, just a local connection to your PC.

lynnmt

@dc42
so connecting over USB will do?

lynnmt

@dc42
Ok I will run this upgrade and get back to you.
Thanks for the help!