48V capable 1LC
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@o_lampe its definitely not something i would ever advise to do or do myself. definitely a fire risk
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We are using stepper motor far above their rated voltage, but suddenly there is a fire risk by using a simple resistor above the rated voltage?
C'mon...it's almost the same: wires with a certain resistance. No voodoo. -
@o_lampe a 24v heater on 48v would run at 4 times its designed power. its exactly the same issue as running 12v heater cartridges at 24v. its a serious fire risk, always has been, always will be
https://reprap.org/forum/read.php?416,732002
https://forum.duet3d.com/post/44928 -
@o_lampe Stepper motors are designed expecting them to be used with voltages over the "rated" value (as they are almost always used that way), they are pretty much always controlled by a sophisticated driver that is intended just for that purpose that will control the current supplied to them and which will more often than not fail safe (even if a mosfet fails "on" there are two of them controlling each coil so the other will shut the supply off) . If they do not fail safe I don't think I've ever seen a case where a failed stepper setup generates enough heat to set something on fire (I suspect the windings will fail before that point, they are much thinner than those used in a typical heater) and any fire is likely to be contained within the shell of the motor.
Simple resistive heaters on the other hand are designed to get hot, they have thicker windings and tend to use much simpler control circuits some of which have a nasty habit of failing such that the circuit is active. If you double the voltage to a heater you will be increasing the power by a factor of 4. Also just to be clear even if you use PWM to "reduce" the power of the heater you will still be supplying 48V to it, not 24V it will almost certainly not have been designed with that voltage in mind.
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these "nooo 24V is the standard no progress must be made!" and "there aren't any 48V heater cartridges anyways" arguments are pointless since
A) having one voltage for all boards and being able to use just one power supply for the DC side is without a doubt the best engineering solution
B) there are 48V heater cartridges just because printing shops don't sell them (chicken and egg problem) doesn't mean progress can't be madeSo all in all anyone from Duet cares to chime in and point any real engineering reason why this board couldn't run at 48V?
I had a quick glance at the schematics and the 12V side (TS30041-M000QFNR) can run only at 40V (42V) max. So I guess that's the reason? I can't seem to find any 1:1 replacement chip that would support 48V so a complete redesign of the 12V side would be required?
(I've searched a bit more and the TS30041 is the same chip previously used on the Duet3D. So I would bet this was solved already.) -
@Anon1337 One could look for a dual-heater hotend and use two 24V cartridges in series.
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@o_lampe Yeah that's a possibility too (maybe even a superior from engineering standpoint I know there were some hotends that used dual cartridges for more even heating of the nozzle).
But people should know that before starting this thread I did message a few sellers on a famous Chinese B2B marketplace and some do sell 48V versions and the rest was like "we can customise whatever you like". So the whole "heating cartridges are only 24V" is a moot point.
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@Anon1337 I'd be checking the voltage rating on any electrolytic caps on the board, many of them are only 50V and the 100uF one for the TMC driver is only 36V. Uprating them will almost certainly make them larger which may cause problems with the board layout.
But most importantly the TMC2209 (and TMC2226) are only rated for 29V and the TMC2240 is only rated for 36V, so I think you would need to go to a TMC5160 or TMC 2160 for 48V, both need external MOSFETS (and even then I think some of the 48V "rated" TMC5160 stepper boards that are available from BTT and the like have had a few problems), I'm not sure if there is enough space on a toolboard for those and the associated cooling that may be needed.
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@Anon1337 as has already been pointed out, one significant hurdle is the space and cost of a TMC 2160/5160 driver & associated fets/ caps etc to run the stepper motor at 48V. The other issues is that we need other voltages on board to run buffers and the processor (5v, 3.3V) so we need a 48V-12V or 48V-5V buck which once again uses larger components and increased board size, even if you use 48V fans and heaters to keep the current requirements below 48V low.
The key question IMO is why is 48V going to be an advantage - other than not having to have multiple power supplies in a machine. The main reason people want higher voltages for stepper motors is to allow for higher speeds before the back EMF becomes a limiting factor. In general extruders are not running fast enough for this to be an issue.
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@T3P3Tony true, the board being 24V max is what keeps the size down (and the board is pretty big already)
one solution might be a double sided PCB and perhaps moving away from the "sticks to a stepper" design (which is weird anyway since most of the nice new extruders use pancake steppers anyways...)
