Tuesday, June 26, 2012

Pondering the Nozzle Orifice Drill Bits

From time to time I see people mention that the J-Head nozzle extrudes slightly under what is expected.  This may be because I have been drilling out the nozzle orifice with a similar concept to what is done with machine tools.  A quality lathe will be built with the tailstock that is about 0.001" high.  This way, as it wears, it will eventually line up perfectly before wearing to a point under the center line.  Taking this concept to the hot-end, the J-Head nozzle orifice is drilled out slightly smaller than the specification in order to provide room for wear. 

A 0.50mm nozzle is therefore drilled out with a 0.4572mm drill bit.

This concept has been creating issues.  For example, in Slic3r, the nozzle diameter needs to be set to a lower size in order to generate the proper gcode.

At this point, I am considering abandoning strategy of providing room for wear, and using exact size drill bits.  While there will be less room for wear, this should result in a hot-end that is easier to use.



  1. I'm no expert but we are talking melted plastic vs brass here. I'm sure there is some but it doesn't sound to me like there will be much wear involved. Something else will probably fail in the hotend before the nozzle hole.

    1. Unless you're using translucent plastic, there are fillers in the plastic. Titanium dioxide, sometimes silica, etc.

  2. It seems like a slic3r engine problem.
    I have same thing whith mine nozzel drilled by 0.5mm bit. in reality that was 0,6 nozzel. but the only way to make it work as it shoud, was setting it as 0.5 in slic3r.

  3. It's always nice to know the exact nozzle hole size but once it's been calibrated and the settings are dialled into your slicer of choice, then you are set to go. What's more of a problem is if either the slicer changes the way it does things or the nozzle changes the next time you buy one. As long as it's identified as being different (model number revision) then we can compare, if things just keep on changing and we don't know what versions we have then it starts to get tricky to compare with other people using apparently the same nozzle.

    I think that same point goes for the nozzle nipple or no-nipple versions, make the part number different so when people talk about what version they are running it's clear and comparable.

  4. Nipple no nipple? Seems to work fine as it is so you can allways leave things as they are but maybe advertise the real nozzle size this way we know what we are dealing with if we need to troubleshoot our prints.

  5. Thanks for the quick replies.

    The original thought, regarding wear, was that the use of a metal implement could enlarge the orifice. By having it slightly undersized, it was ensured that it would last longer.

    With the only exception of special requests, the nipple is completely gone as of the Mk V series of nozzles.

    I can publish the exact drill bit sizes used for each size orifice and will do so in the near future.

    Please keep the comments coming.

  6. I think this is a case where people expect the orifice to be whatever they are told it is, any variance from that is not acceptable (and may be false advertising). Getting a 0.35nozzle and having it be/having to print as 0.3 makes it harder to configure/use since there is less margin-of-error; people go with 0.5 because it is easier to start with and doesn't make a big diff in print quality, they don't want something that prints at 0.4-0.45. This is all made worse when the drill sizes are not disclosed.

    1. False advertising? My whole point of providing an orifice, as I have described, was to provide a product that would, over time, last longer. False advertising implies an intent to deceive. If I intended to be deceptive about this, why would I post that I am doing this?

      While now quite buried, I have been doing this for quite some time. (http://forums.reprap.org/read.php?94,51078,51078#msg-51078)

      As far as not being acceptable, please consider that everything has a tolerance. If, for example, I machine a shaft down to 0.500 inches, and it measures 0.5009 inches, am I being deceptive? Where is the line drawn?

      Also, in a previous blog post (http://jheadnozzle.blogspot.com/2012/05/nozzle-orifice-diameters.html), I measured other manufacturers hot-end orifices. If they were off, were they being deceptive?

      I clearly understand that it is harder to configure if there is too much variation. That is a big reason why I posted this question in the first place.

      Right now, as there are already a lot of Mk V style hot-ends, in the wild already, I am thinking that the best resolution is to simply post the actual drill bit sizes used so that people can be made aware of what must be done to properly utilize them. When the next version is released, then I'll switch to using the metric sizes and abandon the concept of providing room for wear.

  7. Most nozzles are probably oversized, drilling with a 0.5mm drill will not produce a 0.5mm hole, it will be slightly larger, I know the one I have hear I can easily fit a 0.5mm drill bit in it, which to me implies it's likely closer to 0.6mm, I don't have a set of precision measures for anything that small.
    Slic3r only uses the nozzle size to clamp the w/h it isn't used as part of the actual volume calculation, however changing it can cause slic3r to pick a different volume calculation, which might be what people are seeing. Could also be the clamping of w/h making the calculation more correct for JHeads.

  8. Maybe the hole increases it's size to .5 at 200º Celsius because of dilatation... who knows ..

    1. Hello,

      I think it has a lot more to do with how the drill bit cuts. I have always measured the orifice sizes when cold. However, it would be interesting to measure one when hot and see how much it varies.



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