What’s in a nozzle?

It’s never a good thing when customers are disappointed. So, imagine the disappointment when your brand new Jerrill.com nozzle arrives in the mail and this happens when you tighten it onto your Printrbot Ubis hot end.

busted-nozzle

At least one customers even had this happen after a few days of happy printing.

First and foremost, it is critical to get a new nozzle in the hands of the customers whose nozzle broke. After all, a nozzle just shouldn’t break like this. It’s a design flaw plain and simple. And as long as I’m selling these things, I’ll make it right. Don’t worry!

The next item on the agenda was to determine what went wrong. Time to cut open a few nozzles.

nozzle-cutaways-labeled

I compared a Printrbot 0.50 mm nozzle, a Makerbot 0.40 mm nozzle, and a Jerrill.com nozzle that failed QC.

It’s admittedly difficult to taper the dome of an acorn nut into a cone with a tiny flat, when you have no idea how much material is safe to remove and still have a structurally sound nozzle, and you couldn’t control it that well even if you did. Additionally, the spec for the acorn nut specifies a minimum tapped hole depth… not a maximum. Eventually, I hope that nozzle sales are so good that I can get some professionally machined nozzles, but it’s a little too early for that kind of tooling investment. So, this is what I have to work with.

My initial passes at a QC process have been to tighten a 1/4″-20 bolt into the nozzle using the #4 torque setting on my hand drill (whatever that means) which leaves the nozzle tightened on the bolt more than hand tight. Some nozzles bulge a little. A handful of others have broken like in the photo above. Both of these are tossed in the failed nozzle bin. If it passes those tests, it still has to survive repeated poking at the tip with a pin to make sure that there is enough material left on the flat for successful drilling and extrusion.

Even with the solid brass acorn nuts we’re using, there is not a lot of material left at the tip for strength. Printrbot seems to have the sturdiest design in their nozzle. Makerbot benefits from a male threaded nozzle where a threaded hot end can’t apply stress to the thinned brass in the tip of the nozzle.

This comparison, however, points to the bigger problem of ever smaller nozzle bores. It’s not slicer settings and filament types. It’s a limit on how deep the ever smaller drill bits can drill. For example, the 0.10 mm drill bits that I’m using (and admittedly breaking… a lot..) only have a drill depth of 0.50 mm! Unfortunately that doesn’t leave a lot of nozzle for strength, whether it be strength against a bolt in QC, a hot end, or just the pressure of extrusion at these diameters.

I’m interested in seeing some photos of other sacrificed and cutaway spare nozzles from other printers for design comparisons. At $10 to $20 each, it’s an investment that I’ll have to make over time. But it’ll be interesting to gather some industry best practices to inform future nozzle designs. In the meantime, happy printing!

9 Responses to “What’s in a nozzle?”

  1. Charles McGuinness April 4, 2013 at 5:57 am #

    You’re pushing the boundaries, so it’s to be expected. Don’t let it discourage you. Being transparent is great: it helps us customers with our expectations. We’re all on the ride of experimentation with you!

  2. Wing Wong December 6, 2013 at 8:11 pm #

    Jerrill, I found your post via our youtube video. Very very cool.

    Am wondering whether it is feasible to laminate/weld multiple metal sheets that have been drilled individually?

  3. Jerrill December 9, 2013 at 11:03 pm #

    Wing Wong, that sounds even more tedious than drilling a single tiny hole in a brass acorn nut. I imagine it could be done, but it’s not obvious to me that there’s an advantage there.

  4. Jonathan Haberman January 1, 2014 at 6:57 pm #

    Your service is great, I had a nozzle of yours that broke and you promptly replaced it. great service. The thiner tip of the makerbot extruder helps with the prints curling up I think because I find my printrbot tip touches the already printed plastic causing it to curl up. really like what your doing.

  5. Sam February 24, 2014 at 3:02 pm #

    Had you thought about wire EDM for the nozzle bore? It can get down to 0.1mm dia and will go through thicker material. Just a suggestion.

  6. Jerrill February 24, 2014 at 8:56 pm #

    Sam, thanks for pointing out EDM. I’ll check into it!

  7. Jerrill February 27, 2014 at 9:44 pm #

    Sam, the first vendor I asked about wire EDM couldn’t do holes below 0.5 mm. Do you know someone who has a 0.1 mm capability?

  8. Sam February 28, 2014 at 3:28 am #

    I’m in the UK, but tbh I have never needed something that small so not sure the people I’ve used can do smaller. A quick google search brought up these guys http://www.twincityedm.com/precision-wire-edm-services.html who say they go down to 0.04″. It’s probably quite a niche capability but it’s definitely possible.

  9. Jerrill March 1, 2014 at 3:51 pm #

    The most popular nozzle seems to be the 0.20 mm (0.0079″). It looks like the wire EDM can’t easily get down that small.

Leave a Reply