Max hot end heater current



  • I couldn't find it in the documentation but maybe I'm not looking in the right place. Can someone tell me what the limit is for the hot end heater current (Duet and Duex5 if different). The reason I ask is that the Diamond 5 colour needs an 80W heater (seems excessive to me but I guess Peter Bogely has a reason for it). I'm using 24V so I make that 3.33 Amps but anyone using 12V would need 6.67 Amps. Can the Duet handle that? Thanks



  • I've heard 5A as the extruder limit, though it would be good to check with David or Tony.

    80w is just silly imo, I can't see any practical need for that.



  • The RepRap.me site lists two heaters for the 5 color. A 24V/80W and a 12V/60W.

    Don't know if that is correct.

    Given the 5 heat sinks/filaments that are sucking heat away from the nozzle I can see why a higher power heater might be needed

    The 12V heater that came with my 5 color is a 50W unit based on measuring the resistance. I need to hook it up and measure the current to see how it functions under normal operating conditions.

    I've been so focused on finding a good mount I totally overlooked the heater limits of the DuetWifI.

    Good thing I haven't reached the point where I can mount the Diamond.

    Frederick


  • administrators

    That's a good question! We haven't done any tests on maximum extruder heater current. I think the terminal block is good to a least 10A on the Duet WiFi/Ethernet and the mosfet can easily hand!e that (it's the same one we use for the bed heater). So the limit is likely to be PCB trace heating. We use 2oz copper top and bottom, so I suspect that 6.7A would not be a problem.



  • @elmoret:

    I've heard 5A as the extruder limit, though it would be good to check with David or Tony.

    80w is just silly imo, I can't see any practical need for that.

    Yes, I'm hoping that David or Tony will confirm. As someone else has just pointed out, the 12v version ships with a (claimed) 60W heater. Maybe that's because it will fit within the 5 Amp limit? I can only assume from that, that 60w is barely adequate but 80w is better? It seems excessive to me too but RepRap.me are quite insistent on their web site that it's needed.

    It'd probably work better though if the nozzle was a bit bigger to allow the 80W heater to actually fit. As it stands, the hole is 16mm deep and can't go any deeper without breaking through into the filament path, but the heater is 20mm long so there is 4mm of it sticking out of the top. 🙂



  • @dc42:

    That's a good question! We haven't done any tests on maximum extruder heater current. I think the terminal block is good to a least 10A on the Duet WiFi/Ethernet and the mosfet can easily hand!e that (it's the same one we use for the bed heater). So the limit is likely to be PCB trace heating. We use 2oz copper top and bottom, so I suspect that 6.7A would not be a problem.

    Ah, thanks David. You answered as I was typing. So in case you missed it, it seems that the 12v version ships with a 60W heater which would be 5 amps. I guess I'll be safe running the 80W at 24 volt (3.3Amps).



  • @fcwilt:

    The RepRap.me site lists two heaters for the 5 color. A 24V/80W and a 12V/60W.

    Don't know if that is correct.

    Given the 5 heat sinks/filaments that are sucking heat away from the nozzle I can see why a higher power heater might be needed

    The 12V heater that came with my 5 color is a 50W unit based on measuring the resistance. I need to hook it up and measure the current to see how it functions under normal operating conditions.

    I've been so focused on finding a good mount I totally overlooked the heater limits of the DuetWifI.

    Good thing I haven't reached the point where I can mount the Diamond.

    Frederick

    Frederick,

    Out of interest how long is the supplied heater cartridge? My 80W 24V version is 20mm but the hole is only 16mm deep.

    Ref the mount, yes that's a problem that I keep badgering them about. There are currently no stl or cad files (unless you've managed to find any). They'll supply a "Universal mount" but that's only any good if you want to hang the thing off the side of a carriage. I want to fit mine between two parallel rails.

    Ian



  • @deckingman:

    Frederick,

    Out of interest how long is the supplied heater cartridge? My 80W 24V version is 20mm but the hole is only 16mm deep.

    Ref the mount, yes that's a problem that I keep badgering them about. There are currently no stl or cad files (unless you've managed to find any). They'll supply a "Universal mount" but that's only any good if you want to hang the thing off the side of a carriage. I want to fit mine between two parallel rails.

    Ian

    I checked all of my heater cartridges including generic Chinese units, genuine E3D units, and the Diamond 3 and 5 color units - all are 20mm in length - appears to be a "standard".

    Frederick



  • @dc42:

    That's a good question! We haven't done any tests on maximum extruder heater current. I think the terminal block is good to a least 10A on the Duet WiFi/Ethernet and the mosfet can easily hand!e that (it's the same one we use for the bed heater). So the limit is likely to be PCB trace heating. We use 2oz copper top and bottom, so I suspect that 6.7A would not be a problem.

    Thanks for the info.

    Given the versatility of the newer Duet boards at some point it might be a good idea to determine and publish the official operating limits of the board - in your spare time of course (like you have any spare time <grin>).

    Frederick</grin>



  • @fcwilt:

    Given the 5 heat sinks/filaments that are sucking heat away from the nozzle I can see why a higher power heater might be needed.

    Frederick

    I wonder if this is the reason, the heatsinks are certainly pulling some heat away but that's not their purpose. It would seem worthwhile for this type of hotend to have some sort of insulator between the heater block and the heatsinks.

    If 5 colour diamond users are worried their duet is going to be pushed to supply 80w to the heater cartridge an external mosfet board for £5 is an easy alternative.

    Given Ian's testing with pushing three filaments simultaneously through the 3 colour diamond and being able to achieve way higher extrusion volume than volcano, an 80w heater might have its merits.


  • administrators

    I can confirm that the terminal blocks are rated to 10A. Make sure the wire you fit is also good for the current you are using and you have a good connection via a crimp ferrule in the terminal block.

    The traces are similar to the Heated bed in width and length, however they are not duplicated on both sides (due to space constraints) so 9A would be a good limit without further testing (18A for the heated bed, divided by 2).

    Cheers

    Tony



  • @DjDemonD:

    I wonder if this is the reason, the heatsinks are certainly pulling some heat away but that's not their purpose. It would seem worthwhile for this type of hotend to have some sort of insulator between the heater block and the heatsinks.

    Unlike, say, a E3D setup, the heatsinks on the Diamond 3 and 5 have no "heat break" in the connection from the heatsink to the heater block.

    Perhaps this leads to more heat being pulled away.

    They do include a circle of some material that seems to be intended to block heat transfer to the heatsink but it won't have any effect on heat conducted through the connection to the heatsink.

    Frederick



  • @T3P3Tony:

    I can confirm that the terminal blocks are rated to 10A. Make sure the wire you fit is also good for the current you are using and you have a good connection via a crimp ferrule in the terminal block.

    The traces are similar to the Heated bed in width and length, however they are not duplicated on both sides (due to space constraints) so 9A would be a good limit without further testing (18A for the heated bed, divided by 2).

    Cheers

    Tony

    Thanks Tony - that's good info. It looks like with the 24v the current will be 3.33 Amps because the heater is 80W but with the 12v version the current will be 5 Amps because the heater is (only) 60W. A quick search shows that 12v 80W cartridges are available from China (so take that with a pinch of salt) but if someone does source and fit one they'll be drawing 6,67 Amps but that should still be safe.

    Ian



  • @DjDemonD:

    ….....................
    Given Ian's testing with pushing three filaments simultaneously through the 3 colour diamond and being able to achieve way higher extrusion volume than volcano, an 80w heater might have its merits.

    Yeh. Now if I can print the in order of 150mm/sec with a single filament and 250mm/sec using 3filaments, it'll certainly be interesting to see what 5 will do 🙂

    I might yet start printing kitchen units and maybe a new bathroom suite….......



  • Just a hypothetical thought but I guess if one really wanted to push the limits, one could assign two heater channels to a hot end, then split the cartridge wire across two sets of terminals?



  • No, because there is no way of guaranteeing the current split.


  • administrators

    @deckingman:

    Just a hypothetical thought but I guess if one really wanted to push the limits, one could assign two heater channels to a hot end, then split the cartridge wire across two sets of terminals?

    Yeah at Tim says might not be even. If you needed to do that it would be better to have a hotend with two heater cartridge inputs and use two.



  • Ah OK. As I said, it was hypothetical - I think if I ever needed more than 216 Watts (9Amps at 24v) I'd use a blow torch in any case 🙂



  • By way of an update, I've now got the 5 colour diamond installed (but not loaded any filament yet). So I ran auto tune on this silly 80 Watt heater and got the message that the predicted temperature could reach 670 deg C. The result was gain 645.7, time constant 190.4 dead time 6.4. That's all with PWM set to 1.0. The high flow fan (20cfm) was running the whole time and blowing lots of air over the 5 heat sinks.

    This all strikes me as being far too excessive and I'm inclined to bung a standard 40Watt heater in (or run PWM at 0.5 but that seems pointless) despite what RepRap.me say. What do guys think?

    I'll email Peter Bogely and see if I can get a reason why he thinks the heater needs to be 80Watt.



  • Just another quick update on this. I never did get a reply from RepRap.me as to why they think an 80 Watt heater is necessary on the Diamond 5 colour. After I tuned the 80 Watt heater I found the temperature was overshooting quite a lot so I re-tuned it with a PWM of 0.6 which gave more sensible results and was more controllable. I've just changed the nozzle so while I had the hot end stripped down, I fitted a standard 40 Watt cartridge. I've just tuned it and can't see any substantial difference between the results I got with a 3 colour Diamond with 40 Watt heater and this 5 colour, also with a 40 Watt heater. So, I'm going to ignore RepRap.me's advice and run with this.

    One thing I do differently to the "official" assembly instructions is use PTFE tape on the heat sink threads. It's for sealing purposes but maybe it helps insulate the heat sinks from the brass nozzle so they don't conduct as much heat away? Dunno….


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