What is my speed limit?



  • Hi guys,

    I am a month into the commissioning of my DIY CoreXy. I have been tweaking it to get the best results from my prints as I possibly can.
    See attached picture of a vase I printed today. (BTW, I hate that it displays it sideways. I am guessing I should have taken a landscape shot instead)

    This was printed at 50mm/s with PLA + filament.

    I have found that as I surpass 60mm/s things start going wrong. Blemishes, and broken lines resembling underextrusion.
    100mm/s is what I had hoped to achieve when I built this printer. But it seems as if the extruder and/or hotend can't keep up.
    I have upped my amperage on the steppers to 1.2 amps, (They are 2A motors) and put a better drive wheel with sharper teeth to push the filament so it doesn't slip anymore.
    And though that stopped the popping from the extruder struggling to push the filament, I am guessing that the hotend just can't take the speed now. The filament will bend and exit the side of the feeder if I drive it too hard.
    I have suspected my temperature readings on my hotend may be inaccurate, but if I up the temperature I start getting symptoms of overheated filament, so I just don't know.

    So my question is…
    How fast am I supposed to go with a Nema 17 and an E3D V6 Hotend? (Bowden)
    If the consensus is that 60mm/s is the normal max then I will just deal with it and happily print away.
    But if I am capable of reaching higher speeds, can anyone give me some suggestions to try?

    Thanks in advance


  • administrators

    Perhaps you need a Volcano hot end, so that you can me!t filament faster?



  • I thought about that, but I thought those were meant for even greater speeds than what I am trying to attain.

    Considering your response I am guessing that 60mm/s is my limit?
    It's not a heart breaker if it is because I am quite pleased with the results that I am getting at the lower speeds.
    But I was hoping that 100mm/s was attainable with what I have already.


  • administrators

    If that was printed with 60mm/sec perimeter speed, IMO that is a good speed for a standard hot end. Can you achieve 100mm/sec when doing infill?



  • Actually the infill is the handicap.
    My slicer is set for most of the printing to be done less than the set speed, other than the infill which is set to run at 100% of the requested speed. The infill is actually what is failing at higher speeds.
    I guess I could lower the infill value and that would bring the other variables up.
    But the nature of my question was that of any variable being asked to print at 100mm/s.
    Or in short, extruding plastic at that speed regardless of its job. I.e. perimeter, infill, support, etc.

    I have a volcano block. I might just see what a difference it would make.
    Though I would have to totally redesign the X carriage and Hotend mount.
    And I JUST did that yesterday to accommodate the DC42 Mini Ir Height Sensor.

    Btw…that thing works like a charm! 🙂



  • Another question…

    How big of an impact would a long PTFE tube make on the extrusion? I know ti would effect the start and ending of a line, but would it effect the entire line?
    I just discovered the Pressure Advance feature and enabled it in config.g to see what a difference it would make.
    But if it did not, I was thinking of mounting my extruder stepper in another way to accommodate a shorter tube.



  • Measure the resistance of your heater cartridge and calculate the real wattage. My last genuine e3d hotend kit, came with a claimed 30w heater which had a resistance of 6.2ohms, I run it at 12v thats 23W of heating power. I have another no-name cartridge which I am using instead which outputs 40w (3.6ohms). That is going to make a difference to how fast you can melt filament.

    The other consideration is keeping heat in the heater block, a silicone cover helps. Also thermal transfer to the nozzle from the block, can be improved by putting copper grease on the heater cartridge and nozzle threads (also helps immensely when getting the nozzle out again) but NOT on the heatbreak threads, as you want heat not to rise into the heatsink and away from the filament/block. E3D make a plated copper v6 heater block for around £20, I haven't tried it but it must be of some help.

    Are you getting high enough measured temperatures in the heater block, sometimes printing PLA at 190 (when the heater block is only actually at 180 deg C) is not going to enable faster printing. If you haven't got anything that can measure the actual temp, try setting the requested temperature to 30-35 deg C above the point at which you first start to see ooze flowing out when heating.

    I can print at 90-100mm/s with a genuine e3d v6 and an actual 40w heater.



  • Thank you Dj,

    I didn't even consider the wattage of the heat cartridge. I will check that tonight.

    I have a ton of the E3D "Block Socks", and I have experienced how well they work at keeping the heat in but I wish they would redesign them a little. After a couple of prints, mine start to sag a bit, and plastic accumulates between it and the block and when it comes time to change a nozzle, it's just a biggo mess!
    So with this new machine I have opted not to use them because I haven't noticed the temp fluctuating at all. It stays rock solid even when the fan kicks on. I will install one on the block and see if it helps.

    I have suspected the accuracy of my temp readings may be off but I am not 100% sure. It matches the room temp perfectly before I apply heat. I have an IR heat gun but I can't seem to get an accurate measurement. I think because the block is too small.

    So one can print at 100mm/s with these components. Thank you for that.
    I am going test the wattage, install the sock, and figure out how to get a reliable temp reading from the hotend so I can put any doubt to rest that it is not hot enough when printing.

    Thank you sir!



  • E3D has a new version of the sock, which looks better: http://e3d-online.com/E3D-v6/Spares/V6-Sock-Kit-3-Pack
    Ordered some of them to try. But yeah, had the same problem as you with the old version.


  • administrators

    If the temperature reading is rock solid even when printing at 100mm/sec, then a higher wattage heater cartridge won't help.



  • What dc42 said is correct. Also note the limitation on a hotend is not linear speed, but volumetric rate. 60mm/sec at 0.8mm wide 0.5mm high layers is harder for a hotend than 0.4mm wide 0.2mm high layers at 100mm/sec.



  • Thanks guys.

    I will just be happy with what I have. I always thought I could print faster on my old Prusa clone if I could just get the frame tighter. I always worried it was going to detonate if I pushed it above 60mm/s, so I thought that was the only limitation.
    I built the new machine that was more structurally sound with delusions of doubling my print speed, not knowing that I would've run into this same problem with the clone if I could've gotten it any faster.
    SO compared to what I have been used to, 60mm/s is quite an improvement.

    I have read about the Volcano hotend and I think it was meant for other things that what I would print.
    I like high resolution and fine finishes. And my V6 gives me that.

    So with this knowledge, I'll just concentrate on other things and see where I can squeeze a bit more quality out of it from here and there.

    As always, thank you all for the help.



  • Er, sorry but I couldn't resist the temptation to jump in here https://somei3deas.wordpress.com/2017/06/22/exploration-of-print-speeds-with-a-diamond-hot-end/ and https://somei3deas.wordpress.com/2017/06/25/duet-pressure-advance-experiments/

    @Scottbg1 are you using a print cooling fan? That can screw things up especially if air is being blown directly at the nozzle.



  • The e3d socks are one of two designs one which leaves most of the nozzle protruding, these work, the nozzle gets gunked up but the heater block stay shiny. And the type with just the nozzle tip poking out, these don't work, nice idea but filament find its way in between the nozzle and and the sock.

    Volcano can print slow and accurate or fast but not as quick with large nozzles as you might expect, you lose a little z height but gain IMO a better heat exchanger to heat your filament.

    Used with aero extruder and the z height issue is taken care of.



  • @deckingman

    That was one of the first things I did was play with my cooling fan. I have it down to 10%.
    Completely off and the print begins to fail.

    Those are interesting reads and coincidentally I just discovered pressure advance last night.
    I enabled it in config.g but didn't get a chance to test it because it was getting late. I plan to play around with it tonight. Thank you for the info!
    The second article definitely gave me insight on what to look for!

    @DjDemonD

    I meant to mention this to you in my last post, but I had modified the last sock I used by cutting the nozzle hole to a larger diameter and it seemed to work great. I hadn't tried it in this printer yet because I didn't think I needed it.
    I only used them on my old clone because of temperature fluctuation but it's rock solid without it on this printer.

    I want to visit the volcano since I have a block and nozzles in my parts bin. But I'll have to make a new carriage since I just modified it to carry the IR sensor I mentioned earlier. Adding the height of the volcano will make the sensor useless, the way I have it mounted.

    I really want to see what benefits pressure advance brings.

    Thank you all so much!



  • @Sabagmn:

    E3D has a new version of the sock, which looks better: http://e3d-online.com/E3D-v6/Spares/V6-Sock-Kit-3-Pack
    Ordered some of them to try. But yeah, had the same problem as you with the old version.

    I'm also stuck at 60mm/s (0.2LH with 0.4 nozzle, with bowden), beyond, my extruder is skipping. I can go faster but only at 0.1LH

    Socks help when you've got cooling fan for PLA, but no so much, after its the limit of the E3D heatblock. When you've got a rigid frame and an high speed printer, volcano will do the trick, seen it on my friend's printer. 0.4 nozzle are available too for volcano so you'll keep your resolution (currently waiting for mine). Large nozzle and large heat block will let you print quicker.



  • It's all about how fast you can melt filament in terms of mm^3/sec so a large nozzle with a greater area will actually reduce the maximum possible print speed.



  • Head speed is lower as you said, but you can max the melt rate of the volcano block and lay down more filament per unit time, with a large nozzle rather a 0.4mm. Plus big parts printed with big extrusion lines are stronger.



  • @Sabagmn

    You just upped my interest in the Volcano. I didn't look hard for other nozzles. I only saw what they offered in the kit that they sell. And I believe that .05 is the smallest they offer in that. If they offer a .04 I will order one right now.
    Please let me know how yours turns out.



  • @Scottbg1:

    @Sabagmn

    You just upped my interest in the Volcano. I didn't look hard for other nozzles. I only saw what they offered in the kit that they sell. And I believe that .05 is the smallest they offer in that. If they offer a .04 I will order one right now.
    Please let me know how yours turns out.

    I've asked E3D because their descriptions pages are always outdated. The starter pack comes with a 0.8 and the eruption pack comes with the all set from 0.6, the 0.4 is an optional nozzle out of any pack.


 

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