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

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!

dc42

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

@dc42
so connecting over USB will do?

A local area connection to your PC is best.

lynnmt

@dc42 You mean via a LAN (ethernet) port on the duet and on my laptop?

what are the risks of using the SBC here?

I kind of prefer to have the machine running separate from my main computer.

lynnmt

@soare0
I want the simplest possible solution that works reliably without too much burden on the user and costs the least amount in the long run.

The conditions of printing metals and ceramics are harsh by default. I am designing around expectation values for a temperature control system that needs to at least keep up with the speed of phase change in semisolid metals.

metals are dense, and excellent coolants. they also have extremely sensitive temperature specific viscosity behaviors. Their working windows are narrow, this necessitates very fast thermal cycling to enable rapid adjustments to changes in flow conditions at the deposition region. The hotend I built is designed to position an extremely wear resistant(about mohs 8.5), non-wetting(to most molten metals), high surface power density (1-10 watt/mm^2) heating element as the nozzle tip in the deposition zone. the faster we can measure and control temperature, the closer we can get to printing pure metals which have windows as thin as 1/10th of a degree C.

this heater is very fast on its own, and has more than sufficient power density to keep the material flowing,and heat the underlying/surrounding layers to bonding temperature while overcoming surface conduction losses.

Hence, fast control and sensing is really needed...

T3P3Tony

@lynnmt no issues with using SBC mode or networking to your machine. In the long run some users will want to use one or the other based on other needs. I think @oliof meant not using SBC mode for now just to make is simpler for troubleshooting.

Please upgrade to 3.5rc3, then we can work tos get the model of the heater tuned in, the thermocouple isolation sorted etc before going back to the SBC vs Standalone considerations.

The control for all this is done in RRF, your method of connection does not matter at this point.

Is your understanding that the 4Hz control loop is not fast enough for your use?

lynnmt

@T3P3Tony
I have not yet been able to test if the 4 hz loop is acceptable.
my suspicion is probably not.

but I will let you know as soon as I get some test data this evening/tommorrow.

lynnmt

@dc42
after upgrading the firmware from the SBC per these posts and docs:
https://forum.duet3d.com/topic/29125/update-1hcl-firmware-from-sbc/3
https://docs.duet3d.com/User_manual/Machine_configuration/SBC_setup

the model parameters seem to have taken.

Thanks for the guidance.
I will try an autotune with the new parameters and report back hopefully with some video footage of the test.

lynnmt

@T3P3Tony
I have upgraded to RRF 3.4.6. and the model parameters seem to have taken without issue.
Do i still need to go all the way to RRF 3.5rc3?
I have not yet run an autotune.
I am trying to understand a critical detail first:

does the PWM limit set in the M303 autotuning command override the PWM limit set in the model parameters?

also the M307 H1; command returns now :
M307 H1 ;
Heater 1: heating rate 1000.000, cooling rate 300.000, dead time 0.10, max PWM 0.15, mode PID, calibrated at 24.0V
Predicted max temperature rise 243°C
PID parameters: heating P1.8 I9.297 D0.1, steady P1.8 I11.300 D0.1

dc42

@lynnmt the M303 PWM limit controls the PWM that will be used for heater tuning. If you then use M500 to save the model parameters then I am fairly sure it will include that same PWM limit in those parameters. However, the PWM limit you use in M303 is not remembered in any other way. In theory the remaining model parameters resulting from tuning shouldn't depend on the PWM limit you used in M303 provided that the tuning completed successfully.

Tuning uses the same 4Hz sample rate as temperature control. That may be too slow for tuning to succeed if your heater has a very fast response time. Increasing the M303 Y parameter may help.

soare0

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

The conditions of printing metals and ceramics are harsh by default. I am designing around expectation values for a temperature control system that needs to at least keep up with the speed of phase change in semisolid metals.

Interesting device...
One possible solution would be to use a thermal buffer, but this would complicate things extremely much, I think.
Lets hope that 4Hz PID would be enough. Otherwise, you may try a higher speed solution, like the one I suggested above, if you are not willing to build one. 40Hz sampling is an order of magnitude faster than DUET boards...
Maybe you may also consider increasing your thermic capacity of your heater?