Sensitivity and hot end fan.



  • Here is my setup. Fairly standard. I'm using 12v for fans/heaters but it's a 24v system, there is a buck converter for the fan and another larger one for the heater,which is a 40w unit. Fan is a sunon maglev 30mm unit from Farnell. The thermistor wire is tucked under the fan shroud as it was very loose, it's not a permanent bodge.

    Probes fine with the nozzle cold.

    The issue I have is that the moment the hotend fan comes on (40 deg C) the nozzle contact sensor starts triggering, no problem unless I'm probing then it's false triggers on every probing dive. (I normally probe with the nozzle at 130deg C to squash any residual filament that I might have missed, and to reduce the effect of thermal expansion in the nozzle/heatbreak). I've tried a range of sensitivity settings.

    Any ideas or should I just probe cold? Anyone else have a similar issue?


  • administrators

    Either the fan or the fan wires are inducing a voltage in the strain gauge circuit. This is not normally a problem with the E3D fans, but perhaps your Sunon fan creates a larger varying magnetic field. Some suggestions:

    • Make sure that the wires between the fan and the connector are still twinned, especially along any part of them that runs close to the PCB. If they have become split, turn them into twisted pair (you will need to remove the connector to do this, or cut one of the wires and splice it afterwards).

    • You can print a spacer to put between the heatsink and the PCB, to lower the hot end and hence increase the distance between the fan and the PCB. But you are limited by the amount of thread on the top of the heatsink.

    • You can reduce the sensitivity as described in the wiki. Obviously this will increase the probing force required.

    • It's possible that ripple from your buck converter is part of the problem, although I don't think that's especially likely.

    • I assume you are running the hot end fan at full speed. If you are using PWM, don't (at least not while probing).

    HTH David



  • Myabe mechanical vibrations not electrical interference are a culprit? If I recall it right sunon maglev has a more RPM's than usual ones.



  • Thanks David I'll try those things I didn't think it was vibration doing it.

    Sounds very promising.

    Cheers Zov it's a fast fan but not ridiculously so. And it's pretty smooth and quiet.



  • Looking forward for your results as it is my way in near future.



  • Okay so twisting fan wires - no joy.
    Running fan at full power- no joy (I was anyway)
    Disconnecting the fan whilst running and moving it slightly further out from the effector (so I presume it is no longer under the strain gauge traces seems to return the z-probe value to 0, instead of flickering triggered. So now printing a quick and dirty e3d fan shroud with 10mm lateral extension, with space for a cable tie if its not very tight when installed.



  • Think I would have just done a 10mm extension piece rather than a full shroud



  • The one I was using was loose and a bit naff beforehand, on my previous setup I was using an integrated hotend fan and twin 30mm blowers but that won't fit on the smart effector. Plus its an excuse to design/print something with the machine now it has smart effector and nimble attached.



  • Copper foil around fan case at least between the fun and PCB? But it would be grounded somehow.

    Edit: maybe somehow it is possible to turn the fan off before it touches the bed and turn it on after?



  • Fixed. Moving the fan another 10mm out solved it, probing nicely now, hot end fan on or not.


    sorry about the lighting those LED's are really bright.

    Thanks for the help. Very pleased with it, its a great product at a very fair price.
    Now what else can be made from PCB's?

    https://www.thingiverse.com/thing:2490021



  • I bought an extra PCB effector, will see if I can mount a 200mW laser module to it, then I can re-use the 3 0.9degree steppers of my laser pcb exposer for a new delta build.

    I hope that the z-sensing will also work with the laser, this way it should be much easier to adjust height before lasering.



  • Should work if you can tap the surface your etching/cutting with the laser unit (or a small rod as a proxy for a nozzle if that doesn't appeal). So long as its attached in the centre of the PCB and will flex the strain gauge traces.



  • @DjDemonD:

    Fixed. Moving the fan another 10mm out solved it, probing nicely now, hot end fan on or not.

    https://s22.postimg.org/xxqo5r1qp/20170818_211915.jpg
    sorry about the lighting those LED's are really bright.

    Thanks for the help. Very pleased with it, its a great product at a very fair price.
    Now what else can be made from PCB's?

    https://www.thingiverse.com/thing:2490021

    Nice work. Do you mind sharing the dimensions you use on the interface of the e3d duct to mount onto the heat sink? I'm about to design the same type of shroud and wouldn't mind having the sizing/shape of the rounded "clamp" part that surrounds the heatsink correct the first time around.

    Thanks.



  • I take no credit for that part see my thingiverse listing the original item is listed as a source.



  • Right, I forgot that e3d released the original Injection molding cad file, so I'll use that. Thanks!


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