a more powerful heater?

Discussion in 'Calibration, Help, and Troubleshooting' started by R Design, Apr 1, 2016.

  1. R Design

    R Design Well-Known Member

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    I'm extruding at 1mm width * 0.6mm height * 50mm/s = 30mm3/s

    That's well under the supposed 40mm3/s max for the Volcano.

    The 40W heater just can't keep up.

    I've calibrated PID (at 44% parts fan and 245C) and then beefed up the P and I numbers some more.

    I cut the parts fan altogether.

    When extruding at 20mm/s print speed no probs. At 50mm/s no good.

    Checking the HE0 LED on the Rumba it's clear the 40W heater is working flat out. But nozzle dips from 245C to 239/240C. And was not pleased to find a Thermal Runaway (230C) after 5hrs 50 and just 10 layers before the end. Basically it can cope if there's some travel motion going on, but the moment you get a number of layers of constant extrusion, that's it. ;(

    Can we fit a more powerful heater? Don't see anything in the e3d store?
     
  2. Henry feldman

    Henry feldman Well-Known Member

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    Have you tried the Kapton tape/film block on the outside of the heater block like other threads have suggested?
     
  3. Kick2box

    Kick2box Well-Known Member

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    Where did you take this 40mm³/s from? I've seen people claiming they do 35mm³/s with the volcano, but with PLA.
    As far as I know, the bigbox is coming with 30W cartridges, but I did not verify.
    Edit: I did measure it, mine has 30W.
     
    #3 Kick2box, Apr 1, 2016
    Last edited: Apr 1, 2016
  4. Alex9779

    Alex9779 Moderator
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    Its true, the BigBox is equipped with 30W heaters. You do not find these in the E3D store. Only 25W and 40W.
    Maybe go for the 40W, I asked the support (Greg) which to go for when I order the parts for completing the Volcanos for the switching thing and he told me that the 40W are just fine... 24V that is what we need...
     
  5. R Design

    R Design Well-Known Member

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    Really, we don't have the 40W but some kind of custom 30W?!!!

    As luck would have it I have a 40W sitting right here that I ordered from e3d last week as a spare (after reflections in this forum that bending the wires to switch between v6 and Volcano would soon damage them) so I can swap that right in.

    It would be nice if those bullet connectors I ordered from Aliexpress would arrive first, but that could be a MONTH...

    ;)

    btw. is there a schematic somewhere for the Rumba? I tried to see what the Mosfets were and max. switching power for the bed / hotend etc. ?

    @Alex9779 the 40mm3 figure comes from @elmoret who is a guru to me.... ;) He also suggested 15mm3/s with the v6. No specification of material or temperature and I'm not sure to what extent that comes into it. Given the finite length of the melt zone I would guess that it's the thermal conductivity of the filament that counts (assuming nozzle set to temperature appropriate for given material).
     
    #5 R Design, Apr 1, 2016
    Last edited: Apr 1, 2016
  6. Kick2box

    Kick2box Well-Known Member

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  7. elmoret

    elmoret Administrator

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    The BigBox ships with 30w heaters by default, just like all of E3D's products. This is because 40w heaters can reach dangerously high temperatures in the event of a control failure. With that said, 30 watts is plenty even to max out a Volcano. I used a little less than 20 watts to max out a Volcano at 260C (as noted by viewing the average power graph in Repetier-Host). A 40w heater is only needed in cases where temperatures over 300C are required.

    The heat needed to melt filament is actually only a portion of the heat lost: around 10 watts for a Volcano. The specific heat of ABS is around 1.7J/g-K, and the density is 1g/cm^3. At 220C and 30mm^3/s, thats:

    1.7*200*.03=10J/s ( a Joule/second is a watt)

    Then about 5 watts is lost through the heatbreak, I ran these calcs a while ago.

    Most of the heat is lost to ambient, through the heater block. You say you're running the fan, likely you're blowing on the heater block. A more powerful heater is no more the right solution to this than lighting a fire in your house is a solution for it being cold with the windows open.

    Best bet is to move the fan so it isn't blowing on the block, or insulate the heater block. As for my 45mm^3/sec number: That was a best case scenario. It actually depends more on melt flow rate of the polymer than heater power available.
     
  8. R Design

    R Design Well-Known Member

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    @elmoret I like the calculation.

    More specific data:

    - I'm using XT (pale grey!) at 245C;

    - the parts fan is OFF;

    - the extruder fan is clipped to the heat sink above and ON;

    - ambient temperature is 14C;

    Could it be my modest ambient temperature that is preventing the 30W heater from coping (HE0 LED is on continuously)?

    No idea how to calculate the heat lost directly through the heater block to the air: imagine that radiation loss is minimal (it's shiny amongst other things) and CONVECTION is really tricky, how does one estimate that? Or perhaps we turn the whole thing on it head and say, "if the temperature is drifting down slightly with 10W going to filament and 5W to heatsink (perhaps more with my ambient), then heat lost through heater block to air = 30W - 10 - 5 = 15W"?
     
  9. elmoret

    elmoret Administrator

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    I'm not sure what the melt flow rate of XT is, nor the specific heat capacity. With that said, the HE0 LED isn't the best indicator. IIRC the PWM frequency is something like 8hz, you may not be able to tell the difference between say 90% and 100%. Better to look at real data. For example:

    http://3.bp.blogspot.com/-ad4mca1ZrHU/UkyQAiYep4I/AAAAAAAAIYs/6kFp7JeQ8bI/s1600/Hotend+graph2.JPG

    What resistance is your heater? Mine is 20.5 ohms. Allowing for a 1v drop:

    23^2/20.5 = 25.8 watts. There's a fair bit of variance in the heater cartridges, so its worth checking your heater's resistance.

    Personally I'd insulate the heater block before I moved to a higher power heater, but either option works. Another option is to bump up the power supply output by a volt or so. I believe there's an adjustment screw on the supply itself. 1 extra volt would get you about 10% extra watts.
     
  10. R Design

    R Design Well-Known Member

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    @elmoret here's some data.

    Scope readings in attached PDF (sorry too painful to upload multiple JPG).

    It looks to me as though the Volcano requires a lot of energy to just maintain temperature with NO parts fan running. And that only increases with temperature such that at 245C it's working pretty hard before you even start to extrude.

    ps my resistance is about 21.5ohms.

    pps highly recommend this http://lab-nation.com
     

    Attached Files:

  11. Dr Jeep

    Dr Jeep Well-Known Member

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    I think the cable clamps will be ok as long as you don't get local heating through badly made connections, probably the first thing to give out (particularly on a dual) would be the poly fuse which is rated at 5A (though even with two 40w heaters you still have just about enough headroom for the steppers there)

    The weakness somebody has already demonstrated and as can be seen on the layout image http://reprap.org/mediawiki/images/3/39/RRD-RUMBA_PCBLAYER.PNG, is the track feeding -V up to the FET for the heated bed. That is in no way capable of the 11A the fuse on the other side of the supply is rated at.
     
  12. elmoret

    elmoret Administrator

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    With a 21.5 ohm heater, you're down to around 24 watts rather than the specced 30. At 245C you're using 70% duty cycle, so around 7.5 watts remaining with which to melt the polymer. We know from above that ~10 watts are needed.

    Suitable options are:
    1.) Insulate the heater block (preferred)
    2.) Ask BigBox for a replacement 30w heater
    3.) Use the 40w heater you have on hand
     
  13. R Design

    R Design Well-Known Member

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    Any suggestions as to how to insulate?

    Richrap has wrapped Kapton tape around his hotend. But then he never changes his nozzle!

    https://plus.google.com/photos/1007...795&ssid=b64a6b66-6dd6-477d-96fd-6af24953b79e

    I've read about people using Silicone tape. But that maxes out at 260C (a bit close to regular usage).

    Here http://bukobot.com/hot-end-thermal-management I found a reasonable-looking approach in some detail, but they neglect to mention what thermal "fabric" they are using together with kapton tape?

    Isn't insulation a pain if you change nozzles every day and need to get a spanner around the heater block? Not only getting it off - but then I guess any tape loses its stickiness?
     
    #13 R Design, Apr 3, 2016
    Last edited: Apr 3, 2016
  14. Kick2box

    Kick2box Well-Known Member

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  15. mike01hu

    mike01hu Well-Known Member

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    It looks like glass fabric tape like this.
     
  16. elmoret

    elmoret Administrator

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    You can wrap a heater block in Kapton and still swap the nozzles, just use a firm and steady grip with the pliers. A cross wrench makes it easier as well.
     
  17. R Design

    R Design Well-Known Member

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    Thanks everyone.

    The German silicone block is suitably impressive. Difficulties sourcing the right silicone + the tiny gap from volcano to fan nozzle put an end to that for now. Will forge ahead down the Kapton tape path (must get some) and note the utility of a proper wrench (would certainly buy from given website if I were in the USA!).

    Also conclude that Volcano-Bigbox is not an out-of-the-box-plug-and-play solution. But it's worth it. I really want to see what can be done when the parts fan can be turned on properly!
     
  18. Kick2box

    Kick2box Well-Known Member

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  19. R Design

    R Design Well-Known Member

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    Thanks @Kick2box you have made a great case for that.

    I'll get the silicone and give it a go, though I'm going to have to find a better way to get it delivered because for an €18.90 product they want also €18.90 for european delivery!
     
  20. Sarah Nicholson

    Sarah Nicholson Well-Known Member

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    Try this place: http://www.mbfg.co.uk/

    They sell in small quantities as well which might work out more cost-effective.

    Although you may want to keep an eye out on what E3D is up to with the BB 1.1, because in the pic they posted on kickstarter and their twitter teaser pic, the heater blocks on the V6s look a bit odd... almost as if they're covered with something. I wonder if they have been thinking along similar lines.
     

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