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Faster startup with 24v

Discussion in 'Mods and Upgrades' started by Frank van Gilluwe, Sep 28, 2017.

  1. Frank van Gilluwe

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    While the C2 uses a 19V transformer, I think the R2 uses a 24v transformer. The main electronics board appears to be the same for the C2 and R2. The board is also rated for 24V. I bought a higher power 24v replacement transformer to see what difference it might make, and provide enough power for a possible future heated bed.

    The original C2 Transformer output: 19v @ 4.75 amps; measured idle power: 3W (i.e. C2 off)
    The new transformer: 24v @ 6.25 amps; measured idle power: 4W

    With the C2 off, and cooled for 30+ minutes, the startup time, from selecting a previously printed item to print, to starting to extrude dropped from 133 seconds to 54 seconds, a 79 second improvement. With 24V the extruder heats up faster, and the test print started as soon as the bed calibration completed.

    I'm not sure the 24V makes any difference for printing speed or any other aspects of C2's operation, but it does have plenty of power for future mods. The 24V brick is almost double the size of the Robo 19v brick if that matters to anyone.

    This is the unit I bought on Amazon - http://amzn.to/2xFsZ2F. This UL-listed unit has the correct sized DC plug. There are alternatives, but I prefer to get UL-listed transformers, as they tend to be safer and more reliable.

    [​IMG]

    On the 19v unit, I saw peak power of 50W, with 41W typical when printing (measured at the outlet). I forgot to check the new unit, but I don't expect much change.

    I assume the primary reason the R2 uses 24v is for the heated print bed and two extruders consume a lot more power. With 24V these will all heat up to temperature faster. The rest of the electronics uses 12v or 5v, regulated down from the input voltage, so the choice of 19v or 24v doesn't matter for the electronics.
     
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Only thing I would be careful of is the voltage to the heater core for the hotend.
    Jerry seemed convinced when I did the dual extruder mod that I needed a 19v (rather than 12v) heater core for the second Hexagon. I used a 24v heater for it and there is a slight, but noticeable lag in it heating compared to the stock one... Does this mean they used a 12v core and over rated it or that they used an actual 19v core? No clue, but in either case the 24v one does work fine.
     
  3. Frank van Gilluwe

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    I'm not sure - there are no markings on the extruder. I sort of assumed Robo would use the same extruders in the R2 as the C2, and therefore it's likely a 24v unit. Since the C2 is PLA only, there isn't much need to go above 210 degrees C, so 19v should be fine. In the R2, it supports other filaments like ABS that require a much higher extruder temps and may need the 24v to achieve those higher temps.
     
  4. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    They list them as different parts on their website and, like you, I could tell no difference, but @Jerry was pretty adamant that it needed a 19v heater ... bear in mind that their version of the Hexagon uses a rather custom thermistor as well (we have spent time trying to match that and had no real luck) it is a cartridge style like the generic one, but a differently sized cartridge.

    We found some really cheap things on AliExpress that technically would fit but it was a standard glass bead thermistor crimped into a small chunk of brass -- low-tek all the way :)
     
  5. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I suspected that the control board was 24v capable -- they only have the one set of boards for both printers.
    Using a 24v supply on the C2 is actually a really good project.
     
  6. WheresWaldo

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    I still can't find a source for 19V heater cores, I think your sample is too small at just 2 ceramic heater cores to tell if the difference isn't just manufacturer variance. My money is that they are both 24V in the C2 and R2. Much easier to source one single part in quantity than source two different parts. Since a heater core is a purely resistive load it really doesn't matter if they did it that way.

    Did you compare resistance on both cores?
     
  7. WheresWaldo

    WheresWaldo Volunteer ( ͠° ͟ʖ ͡°)
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    That is an interesting choice for power brick, the R2 has a four pin not a barrel connector like the one you showed.
     
  8. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    24v cores were (I bought 10) all in the neighborhood of 13.5-14.0 ohms
    12v ones were 9 ohms (I measured several out of my stock of many all were ball-park 4.0-5.0 and most were 4.0-4.3)
    the ?v one from Robo was 12 ohms

    edit: typo
     
  9. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I agree the sample size from Robo is insufficient to the task :)
    Calculations say the 12v ones should be 3.6 ohms... oh well. They were not reading that on my Fluke.
     
  10. WheresWaldo

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    That leads me to believe that it is a 24V, just to give you one more data point, the heater core on the hexagon I got with the R2, which is supposed to be a 24V cartridge, measures 22 Ω. I think it is just their supply chain and the consistency of using multiple Chinese suppliers. I would bet that the binning done in some of these factories is very generous.

    Note: According to Ohm's law (this is theoretical limit not real world when using parts of unknown tolerances), A 30 W 24 V cartridge should be 19.2 Ω and use 1.2 A. A 40 W 24 V cartridge should be 14.4 Ω and consume 1.67 A.

    With these devices, being as simple as they are, my guess it the conversation goes like this at the Chinese factory.

    A: We make 1M cartridges a month and sell 12 V and 24 V split evenly
    B: Okay we will make 1M
    A week later ...
    A: I got an big order for 1M 24 V
    B: Okay we will label them all 24 V​
     
    #10 WheresWaldo, Sep 29, 2017
    Last edited: Sep 29, 2017
  11. Frank van Gilluwe

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    Being a resistive element, if the C2 really is 19V, using 24V is only 25% increase. I doubt it makes any significant difference. The heat is regulated, so that if it now heats up 25% faster, it remains in the off state a higher percentage of time. Note that the voltage to heat percentage is not likely the same, but without a lot more testing, it's a good analogy.

    I've now run a couple of parts at 24V, and I can see no difference in the operation or part quality.

    Of course I'm also risking the extruder has an premature death, but I really don't think it will. Use at your own risk :) If mine does die, I'll likely replace it with an R2 extruder presuming it fits.
     
  12. mark tomlinson

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    The only real side effect (assuming the heater core was actually designed for 19v) is that at 24v it will draw slightly more current.
    Using a 12v heater core where a 24v one is expected would be roughly double the current and that might might a difference.
    19v vs. 24v? Not sure it would matter. That presumes there actually is a difference in the heater core and I am hesitant to jump on that bandwagon. It is far more likely that they are the same*.




    *although why then they insist on stocking them as different parts ... no clue.
     
  13. Frank van Gilluwe

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    Checked my C2 extruder - 13.4 ohms. At 19V this would be a 27W unit. At 24V, this would be a 43W unit. Neither fits into some nice standard, but there could be a lot of variance in manufacture as WheresWaldo points out.

    To measure the ohms, turn off the C2, remove the top plastic black cover from the extruder assembly (held on with magnets). Pull out the two-pin connector with two black wires. Measure at the two pins on the PCB.
     
  14. mark tomlinson

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    Even at roughly 40w that is not excessive.
     
  15. daniel871

    daniel871 Well-Known Member

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    To be fair, it isn't as though the rest of the electronics we're using are super high tech to begin with.
     
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  16. OutsourcedGuru

    OutsourcedGuru Active Member

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    12.9Ω measured in the new C2 extruder purchased from Robo 3D (fresh out of the bag)
    put the multimeter probes into the side of the connector rather than the tiny pin holes, set to lowest setting,
    hold for a full 60 seconds since it started at 13.2..., 13.1..., 13.0..., then settled on 12.9
     
  17. mark tomlinson

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    :)
     
  18. WheresWaldo

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    A lesson that needs repeating. If you don't have an agent on site at a Chinese factory. One paid by the customer not the factory itself, You really have no idea what you are getting. If a Chinese factory can save 1 penny per part in a million parts they will and not tell you. I bet all those 24V and 19V parts are all in one bin in that same Chinese factory and you need a 19v one, bag it and tag it as 19V and no one will be the wiser.

    This is not a knock on companies that use Chinese manufacturers because all companies are in the business to make money and they try very hard to drive down costs. Even companies here do risk analysis to see if changing a manufacturing process or supply chain will cost more than any lawsuits that might arise.
     
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  19. OutsourcedGuru

    OutsourcedGuru Active Member

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    Alright, I'm going to upgrade mine to a 24V brick as well. I'll need the extra power and don't want to burn out this one since it's so close to capacity now. It's possible that all the hotend wires are under-sized on the C2, as designed, ... and hence Allen's reservations on this. Mark measured 13.5-14 ohms on his 24V hotend so this doesn't feel significant enough to merit the worry.

    (I'm guessing some of those power calculation graphs will be off but who cares)
     
  20. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    I had concerns around that when I reworked the hotend to install the second extruder. I did not change the stock ones, but I went with a somewhat larger gauge on the ones I added.
     

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