New CoreXY Printer: Any sense to run at 32V ?
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@o_lampe thanks, very good idea for the fans, at 75% duty cycle it will work.
About the fans, they will need a 12V PSU? or the Duet can give the 12V.Any suggestion of PSUs at 30V or 32V 10A to 15A, just to support 5 filament heaters (the heatbed will use a MOSFET directly to 110-220V)
Best
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@spirit-robotics said in New CoreXY Printer: Any sense to run at 32V ?:
About the fans, they will need a 12V PSU? or the Duet can give the 12V.
The Duet3 controllers have an 12V/800mA onboard supply. If that's not enough, you can use a resistor in series and run a 24V fan from 32V PSU.
Regarding the 32V PSU: I don't know any PSU with that voltage except adjustable, but expensive laboratory-PSUs.
Maybe other Duet3 users can chime in here?For my 35V test setup, I used a 24V + 12V meanwell supply in series, both have a small adjustable Vout range, but maybe not enough to reach 32V.
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If you want to run it super fast (assuming you can get the extruder/hot-end to keep up), try servomotors. I use iHSV42-40-07-24 motors in my corexy sand table and with 20 tooth drive pulleys they can run up to 20k acceleration and 2000 mm/sec (that's where it hits the 3k rpm back-emf limit of the motor). Acceleration is limited by the power supplies (I use a 150W supply on one motor and a 200W supply on the other), I think. The motors have a built-in 5A current limit which puts them right about at 120W (at 24V), so a 150W supply should be sufficient for one motor.
A couple people here have used these motors in their printers. I have only tested directly substituting the servos for the steppers (1:1 drive) and found the print quality unacceptable. The built-in 1000 line hall effect encoders don't provide the same resolution that 1000 line optical encoders would, so you might have to use some drive reduction to get good print quality. The other people who have used them in printers use 3:1 reduction and the photos of prints that I have seen look flawless. Even with 3:1 reduction, speed and acceleration will be far beyond what you can achieve with steppers.
The motors are 78W units, compared to steppers that are typically <12W. With 3:1 drive reduction, unless there's a severe problem with the mechanism, it will absolutely never ever skip a step. It never skips even at 1:1.
The motors use step/dir/enable signals that you can easily get from a Duet2 expansion board. As far as the Duet board is concerned, they are stepper motors. You have to set the timing parameters for the step/dir/enable signals in the config.sys file like this:
M569 P5 S1 R1 T4.0:5.0:6.0:11.0
You might find these blog posts to be interesting reading:
https://drmrehorst.blogspot.com/2020/04/the-spice-must-flow-gets-servo-motors.html
https://drmrehorst.blogspot.com/2020/11/heres-what-happened-when-i-swapped.html
https://drmrehorst.blogspot.com/2020/04/ihsv-servomotor-information.html -
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@mrehorstdmd Thanks a lot. I will check these options these days.
But, why Duet give the options to work up to 32V if there are not any PSU available? far better will be give the option to run at 36V
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@mrehorstdmd Just another question.... if you only need the signal from the duet, so you really dont need the drivers in the PCB. That's is correct?
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@spirit-robotics That is correct. You'll still use the drivers on the board for the extruder and Z axis, but the others will be available for things like additional extruders or additional axes, or as spares in case one of the other drivers fails.
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@mrehorstdmd thanks a lot. It will be a great experiment, I will try in a larger unit
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@spirit-robotics
Make sure, your Z-axis can keep up with the travel speed of the Servo-gantry. Otherwise Z motion could slow down everything while mesh-leveling is active. -
@spirit-robotics said in New CoreXY Printer: Any sense to run at 32V ?:
But, why Duet give the options to work up to 32V if there are not any PSU available?
Some semiconductor / IC may be rated for less than 36V.
A lot of PSUs have a voltage trim pot to calibrate the output voltage; a 30V should adjust up to 32, or a 36V may adjust down.
Example - a Meanwell SE-600 "36V" PSU will adjust from 32 to 40V.
https://www.meanwell.com/productPdf.aspx?i=469A lot of 24V ones with adjustment will go up to 28V, which gives a bit of gain over just 24V.
You need to check the data sheet for the exact PSU model before you buy it, to see if it has output adjustment.
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@rjenkinsgb great info, I checked the data and these look great SE-600-36
