Pressured air cooling controlled with servo and ball valve
-
As an alternative to my Ball Valve+RC Servo design, I have ordered a PWM capable proportional control valve. The advantage of the Proportional valve is that it is basically plug & play and has less moving parts. But just like the servo, it has a specific PWM range from 300-400 Hz for 0-100% flow. So my Problem remains the same...
@dc42 would it be possible to add an R value to the M106/M950 command to control the PWM frequencies that are achieved at zero PWM and at maximum RPM similar to the R value in M453?
Cheers
Max -
The data sheet at https://www.burkert.com/en/Media/plm/DTS/DS/DS2863-Standard-EU-EN.pdf doesn't seem to match your decription.
That just refers to PWM and the figure on page 8 shows a pretty linear repsonse from about 0.1 to about 0.9 input - probably more linear than any fan, so I don't believe you do have the problem you think you do - surely you just use this as a 24V fan, with a 400Hz PWM? You could put 0.1 low limit on it so it opens immediately you have any non-zero demand.
I do note that I don't understand the X axis scale on that graph, because it's a 24V 420mA coil. Also I'm assuming that response to PWM will be similar to the response to whatever that scale is indicating.
Where are you seeing something that suggets you need to vary PWM frequency? M950 already lets you specify teh frequnecy and then the standard fan control will vary duty.
-
Thank you for your feedback. I think you are partly correct.
I have tried setting different PWM frequencies in the M915 command. The valve behavior does not change much. Although on higher frequencies (Q>4000) the valve stopped whining, so I am going to stick to those.
This is my recent Fan/Valve config:
M950 F1 C"1.out1" Q-1 M106 P1 S0 H-1I have good control over the airflow with a fan speed from 78% (valve closed) to roughly 90% (valve fully open).
Cheers
Max -
@MaxGyver said in Pressured air cooling controlled with servo and ball valve:
78% (valve closed) to roughly 90% (valve fully open).
Look at the M106 L and X parameters to set the min and max range to match your usable range. That should scale the S parameter to make S0 to S255 within your usable range.
-
I have already tried this. The L and X factor of M106 will not scale the range but rather set the minimum and maximum fan speed.
With this configuration the valve will stay in the same slightly open position at a fans peed of 5-80%. So I still only have real control over the flow from 80-90% fan speed.
M106 P1 S0 H-1 L200 X255Cheers
Max -
@MaxGyver My mistake.
-
@MaxGyver said in Pressured air cooling controlled with servo and ball valve:
Although on higher frequencies (Q>4000) the valve stopped whining, so I am going to stick to those.
This will for sure change the valve response characteristics. Perhaps this is why the valv response is not as stated in spec.
400Hz is the way to go.
-
@BoA The valve response characteristics do not change with the PWM-Setting. I have the same response with 300, 400 or higher Hz. Only with high Hz the valve is noiseless.
Cheers
Max -
@MaxGyver how is this valve working out for you? I'm looking at a similar setup but using a compressed air source instead of an aquarium pump.
Have you put a flowmeter after your solenoid to determine how much air you are delivering and able to control the airflow?
-
Hey @lael,
yes the setup is working well,
I am using this pump by the way.
It has more than enough airflow, good pressure and is not too noisy.
I am switching the 230V power for the pump with a relay.The valve is also working good so far. Although I have not figured out how to map it correctly to get a range of 0-100% airflow like mentioned in my previous posts.
Right now I am printing with PLA where I have it fully open all the time anyway.I have tested the airflow with a flow meter. At the hotend I have an airflow of around 20-25l/min. This reduction is mostly due to the 4 mm internal diameter of my tubing. But so far the airflow is sufficient.
-Max
-
@MaxGyver Good to hear! That is quite a lot more airflow than Berd Air will supply. What is the max and min airflows you can control it to?
So for the wiring configuration you have a relay in line on the PWM fan output that triggers the Relay for 240V to the pump? That way when the fan would be on the pump turns on?
-
In terms of part cooling at the hotend - this guy: https://twitter.com/brendonbuilds/status/1313914876922912768/photo/1 has an interesting setup. Looks like a resin printed part, but a 6mm aluminium tube should be able to be bent into the same design.
-
@lael I can control the flow from 0% to 100%. The problem is that this range corresponds to the area of 80-100% fan speed on the duet. My workaround is to set the minimum fanspeed in my slicer to just over 80%.
Since I am also cooling my hotend with the air pump, I have set up the relay to trigger when the hotend reaches a certain temperature.
-
I can see how that would create some frustrations with slicing. Do you have any photos of your hotend cooling setup - that sounds neat!
-
@MaxGyver I wonder if the control restriction you are seeing is related to the lack of air pressure running through the valve. If you take a look at a similar, but different valve here: https://docs.rs-online.com/02fd/A700000006738966.pdf (SMC, amperage controlled, not PWM), you can see that the operating pressure has a direct correlation to the operating range of the valve, and that with too low an air pressure, the total flow (lpm) will be reduced.
It also seems that a larger bore is more effective with a lower pressure. (What bore size is the model you got?) I would guess, without doing the math in the burkett data sheet, that their valves would have similar / identical properties.
So for the SMC model at a bore size of 4mm and pressure of 0.04Mpa / ~5psi you would expect to see the total range of flow starting at 230mA and wide open at 320mA/330mA, and with a flow of 0-30Lpm. I wonder if that behaviour is why you are seeing the PWM control in such a narrow band?
-
I wonder if you were to hook it up to a compressor supply at a higher pressure, then run a pressure regulator after the differential valve whether that would give a greater range of adjustment. Then you could use a flowmeter similar to: https://www.aliexpress.com/item/32905397665.html (assuming they also work consistently at such a low pressure...) to measure and control the flow that is released to part cooling.
-
@lael The SMC Proportional valve will not work on the Duet since it is not possible to control the amperage properly. According to the data sheet the buerkert valve can be controlled applying a PWM frequency of 300-400 Hz. My guess is that this corresponds to 80-100% fanspeed. In this area I can control the flow very precisely so pressure is not the issue.
Cheers Max
-
Hey, I am sorry to reheat this topic.
I have been using magnetic proportional valves for some time with limited success.
They are hard to control with the duet right now. Furthermore, they tend to heat up during longer use which makes them even harder to control. Since they are also very expensive I switched back to RC-servos and ball valves.Can a demon.g be used to translate the M106 Fan speed into a Servo position?
In my case I need 0%-100% fan speed to equal 0°-90° Servo position. (Or stepper position as an alternative? )@lael What solution are you using right now?
-Max
-
@maxgyver said in Pressured air cooling controlled with servo and ball valve:
Can a demon.g be used to translate the M106 Fan speed into a Servo position?
In my case I need 0%-100% fan speed to equal 0°-90° Servo position. (Or stepper position as an alternative? )It would be nice if we could write a macro called 'M106' and put all the math required there. When gcode contains a M106 command, the macro is called instead of the fan definition in config.g
I'm currently in a similar position, where I want to change retract/unretract behaviour and use a servo or solenoid for Z-hop. -
@o_lampe said in Pressured air cooling controlled with servo and ball valve:
It would be nice if we could write a macro called 'M106' and put all the math required there. When gcode contains a M106 command, the macro is called instead of the fan definition in config.g
I've suggested that before. while it's currently possible to add a macro to create a new gcode, it's a bit harder to do for an existing gcode function that the firmware expects to behave a certain way.
In this specific case it's been requested to allow M106 to function with things other than fans and it's on the wishlist for now.
