Tuesday 19 June 2012

Jammed Fr!gg!n Nozzle! - #30DoC Days 15...18

An update! - life and frustration with things failing on me temporarily got in the way of 3D printing :), but I did managed to design and print a few more things over the last few days while my main printer was down -

Firstly I had 4 jammed Nozzles in the last 4 days ! That's something that has not happened to me for about 9 months now, really annoying, but at least I worked out what was causing it! - I was not amused... see below for an insight and some questions...

This all started because I wanted to print a few things in Translucent plastic, and the only stuff I had was some old (about 1 year) Chinese PLA from Esun, I had given almost all of it away and stopped using it about 9 months ago when I switched over to use Faberdashery, Orbi-tech/GRRF and Ultimachine PLA's.

It seemed to print well and I made a few things, then I did a test print of a new extruder and it jammed up Solid, ground the hobbed bolt and stripped the filament.
The first two failures, little did I know what was causing it - see below - 

I tested a few things and came to the conclusion my hot end had failed in some way so, I disassembled it and investigated.
An hour later I had cleaned everything and checked all the hot-end parts, and it all looked fine so I re-assembled it.

I switched over to some Black Makerbot PLA and finished my test print, It all worked fine.

Then the new Reprap challenge appeared (Impossible Spheres puzzle - proposed by Richgain) and I thought   I would try the translucent (Esun) Chinese filament again - I printed with Yellow, switched to red and back to yellow and then my nozzle Jammed again.

'Bad' Esun PLA - see details below.

With the nozzle hot and some manual pressure on the drive gear I inserted a 0.45mm drill bit into the nozzle, it immediately allowed PLA to extrude out, I twizzled the drill bit and removed it, the nozzle jammed again straight away. I removed the extruder and disassembled it cleaned out the hot-end and continued on printing.

I had another jam and another clean out, then it jammed again so I switched over to some White PLA and attempted to push out the block, it did not work, and after using the drill bit again and having the same results, flow when the drill was inserted and no flow after removal I concluded that something was inside the nozzle and I was pushing it up with my drill bit, it was flowing back down and blocking when the drill bit was removed.

It was only when I cleaned out the nozzle again with the help of the white PLA I noticed a dark spec in the blocked filament.

I thought it was part of my hobbed bolt's teeth to start with, but after looking at it closly I was starting to think it was a ball bearing...

I checked it under a microscope and - I was right! 

This ball bearing was removed from my hot-end after using some PLA manufactured by Esun PLA.

Since this had happened 4 times and wasted quite a lot of my weekend with cleaning out my hot-end I checked over the last 100m of this filament and I found another 3 ball bearings embedded inside the filament!
The question is how and why are there ball bearings in this filament?

I had ignored bubbled in the filament before this as it's a common fault of low-grade / low-cost filament, I just had not expected to have contaminants also embedded inside. Signs of the bubbles along the filament usually indicated a ball bearing close by.

I had four blocks this time and I found 3 more bearings in the remaining filament, god knows how many more  there could have been in the Black stuff I had struggled with in the past?

So if you have any filament with bubbles you can see, check if it also has any contamination in it.

If you were looking to block a 3D printer hot-end in the most effective way, using a ball bearing bigger than the nozzle size is the best way I can think of, so is this an accident or intentional?

I stopped using the Black Esun PLA last summer after it caused so many blockages and fine stringing with my 0.4mm nozzle, I now wonder if they were also ball bearings or other contaminates, 
Image from Last summer (2011) - the black Esun PLA also shattered on me last summer, I still don't know why.

The moral of the story, you get what you pay for, buy materials from a source where you know who makes it, and watch out what you put in your 3D printer. 3D printing is already hard enough without nozzle blockages to deal with.

I will take my revenge on the last 100m of this Esun PLA, it's going to make a nice piece of PLA scrap Art, not that this nasty PLA deserves any more of my attention... I won't be putting any of this in my 3D printers ever again.

Has anyone else had any experiences like this? am I very unlucky?

Translucent plastic can look really amazing, just watch out where you get it from and what's in it!.

I am still after some high quality translucent PLA, if anyone can suggest a good source.

The only other thing that comes out of this experience, is that if we could find a way to control a bearing in a nozzle you could almost completely stop any ooze in a dual extruder set-up, we were recently discussing how to overcome dual extruder dribble over on the forums, if someone can think of a valve, I can now vouch that a ball bearing makes a perfect blockage and a 0.45mm drill bit acting as the 'pin' releases it.

And now my printer is back up and running I managed a nice print for the RepRap Competition with my Faberdashery PLA -
Slic3r 0.8.3 - 0.3mm layer height, 60mm/sec print speed, 0.5mm nozzle (or so I hope after all the blocking and clearing incidents!).

I feel better now, having vented all that.

I have some Raspberry Pi, a new extruder prototype and some other interesting things waiting to print out, I'll catch up on my missed #30DoC days now.

Thanks for reading.




  1. Seems like you completely missed my 'worst filament ever' blogpost 2 years ago...

    Since then I design my hotends to be "self cleaning", ie you can cold plug the whole mess from the inside if the nozzle.

    My arcol.hu v4 has the best "self cleaning" ever.

    I know what frustration it causes. I was ther I did that.
    I also include in my buildlog to clean the nozzle before assembly, despite I clean all of it three times before shipping.

    In short I do everything I can to avoid or minimize frustration like this.


    ps: I now have a raspberry case campaign ongoing, you may be interested:

  2. The obvious solution would be using a ferromagnetic ball bearing with a non-ferromagnetic nozzle and using a magnet to pull the bearing out of the flow path, and removing the magnet to let it set itself back in the opening. I know the heat we're dealing with can demagnetize some materials, but neodymium might have a high enough currie temperature if you insulate it, and electromagnets might also be usable. The ball itself would not need to be magnetized as long as it can still be pulled strongly enough toward a magnet.

    1. I thought the same, but also worried that the physical flow of the plastic would overcome the magnet and just push the ball back down.

      I wondered if you had the ball at the end and had a horizontal groove in the nozzle end, you could use hardened length of metal (a pin?) across and pulled up into the groove with a electromagnet at either side, this would push up the bearing and allow flow around the ball and past the pin. you would end up with two sides of extrusion, but it may flow back together under compression onto the object. To seal drop the pin down and the pressure on the ball seals the end?

    2. This comment has been removed by the author.

    3. how about something like a caulking gun that they use in the fast food industry for ketchup, or for frosting and elsewhere i'm sure? it has the holding tube for the stuff and has a plate at the bottom, covering the nozzle, then when they squeeze the grip, it lifts the plate and squishes a portion out, then drops the plate again. the plate is lifted via a rod that runs out thru the center of the holding tube and is actuated entirely outside of the holding chamber.
      in this case the holding tube is the melting chamber, and instead of a plate, we use a small diameter rod, we'd have to modify the extruder body to get the filament to be pushed in at a slight angle to the side rather than straight down like it is now because the rod would be traveling thru that space to be actuated from outside the nozzle assembly itself by a small solenoid, or servo motor, mounted directly above the tip, basically right where the filament enters the nozzle in current designs.

  3. Hi,

    (seems like my post from the morning got lost somehow)

    I ran into this issue a few years back:
    "Worst smelling filament ever"

    Since then I design my hotends to be "self cleaning", ie. I can remove the whole inside mess as a "cold plug", so everything comes out, and clean.

    I think v4 mastered in this. The "self cleaning" feature is awesome.
    If you fear you got something inside, you just unscrew the nozzle at room
    temperature (or better at around 100-140C), and it comes out clear from the nozzle (or breaks the filament, but in that case you retry after a bit of extruding).

    I even clean each nozzle before shipping, three times. But I also advise in the assembly manual to clean the nozzle again:
    http://wiki.arcol.hu/arcol-hu-hot-end-v4-assembly and

    I refer specifically to this picture:


    ps: Btw, I also have an ongoing Raspberry Pi aluminum case,
    maybe you are interested:

    1. Hi Lazlo, thanks for the link to the post, it does look like you have had very similar problems with less than great filament.

      I must try out an arcol hot-end soon, it's a very nice looking design, I have always liked it.

      I missed out on your mini Hyena's, I'll order some of them as soon as you have them up on the webshop.

      And I did spot your Rpi case at the weekend, very nice, I'm adding mounting 'ears' to my design.



  4. Hi Rich,

    Very interesting find these ball bearings in the pla... I wonder what Eset would have to say about this. Ever tought of asking them? with some pictures as proof.

    Also if those balls are metalic it may be a good idea to start checking our filament with a metal detector or magnet. This may be more common than we think with chinese stuff. Or maybe it was simply a failling machine and they since repaired it.

    Now instead of wasting that transparent PLA why not just cut the parts with the bearing away? (if theres only 3 balls left it would be easy)

    1. Esun are not easy to communicate with, "There are Balls in your filament!" "Balls I tell you" ~ and to be honest I'm not all that interested in what they would say about it. I do feel for anyone else who is struggling with poor plastic, it really makes a big difference to the achievements possible and the enjoyment of 3D printing.

      3 balls are all I spotted with the naked eye, I'm sure there would really be more than that - I get the idea of cutting out the bad bits, but it's got past that stage with me, I want to see it melt and have the satisfaction of knowing I destroyed it. I gave so much of it away last year, I need to check if anyone else had problems with it.

      I will share the creation.

      And check out Lazlo's blog post in the comments above, he had some very odd stuff inside that ABS, I have no idea what it was, but it didn't look good from the photo.



  5. Balls, Inspector?! (Brings back memories of an especially cheesy 1980's New Zealand TV advert for cheese balls.)

    Anyway, what a bugger, and thanks for the heads-up. Not that I feel any need or intend buying from anyone other than the great Faberdashery.com

    BTW, Having a V3.0 Arcol, I can vouch for Laszlo's claim that his hotends are very easy to clean out, but the whole process still takes 45 mins to an hour each time.

    While I notice it, can we talk about a detail in your last image of this post 'assembled_1.jpg'. Just above the laterally oriented edge of - and actually in the LH piece of yellow material, there is a collection of voids. I began noticing similar features in my own prints were a precursor to a hotend blockage. The only method I've found to reduce such details appearing - and possibly also the blockages from happening - is to print at 40mm/s or less. I think the voids are possibly also related to the rate of acceleration in gcode produced by slic3r. I never noticed such details appearing in parts printed from sfact generated gcode.

    Any thoughts?

    Keep up the good sleuthing!

    1. Hi Hamish I'll try out an Arcol hot-end at some point, it will make a good compare to the J-heads I have been using for the last year.

      I have just been trying to work out the voids in some of my parts, I agree It could be the acceleration settings, I do have them set rather fast, it looks like the nozzle is being 'jerked' away too quickly as some sections are meeting up, leaving a small void. Or it could be a loose belt? That's the problem with changing things all the time and almost never doing the same print twice. I went through 3 slic3r releases and some firmware tweaks during that print session.



  6. I for one, has also seen balls(maybe, it was over pretty fast) crusading for my hotend. Fortunately, I managed to flank them of with my biggest sharpest kitchenknife. Even though it was long ago that dark and dreary evening, ack.

    More seriously though, this was one of the reasons that I made those pesky wikitables, that I have gladly stayed away from since. Because, the firmer we grab those suppliers by the balls (needless to say, not those they apparently deliver) with a separate page for each company.

    Here is the template: http://reprap.org/wiki/FilamentNewCompanyReviewTemplate

    1. Hi Daniel

      I did start doing a big filament review last year, but it was so boring and tricky to quantify I abandoned the blog post. When you find a filament that's nice and easy to work with you sort of stop fighting the not-so-good stuff. but it's always to get other people's opinions about printing plastic, so it would be great to have some more technical capabilities of the materials we use.
      I think reprappers are not a forgiving lot when it comes to poor quality, and rightly so, but it does make me wonder if some of these suppliers actually test what they produce in 3D printers. I doubt it, they have a whole world of 'testers' out there they just will not get any repeat business.

    2. Hi there. Sorry about the delay on this reply, but Hey Progress! :D
      Speaking of which, I have linked your repraper-review here: http://reprap.org/wiki/FilamentReviewsRepRaper

      Keep up the bloggin! :D

  7. I had no time to read all the post from the readers, but I have something to explain about materials regarding our experience.

    We started buying material with a contact in China called "CB Photoelectricity". They send us some filament, it didn't seem to be in bad conditions, we got 5kg rolls in Translucent Green (Exacly the same color that you reported problems) Translucent Blue and Translucent black. We bought both 1,75mm and 3mm filament.

    Translucent green 3mm worked properly and we had good results when printing. Also translucent blue 3mm was ok. We had problems with 1,75mm and the 3mm black material.

    They seem to had some particules insided (same shape that you have reported), they blocked our nozzles several times because we thought that the problem was in the nozzle not in the material. Personally I don't think that these "balls" were bearing balls because they were so little but I can not go back to examine another time them.

    The point is that you say that this green material you had in bad condicionts came from ESUN, and exactly the same color for me came from "CB Photoelectricity". This fits with my personal theory of where the PLA, and ABS Material were coming:

    For me, at the beggining, there was only ONE provider for all the chinese suppliers. I can say that because now we have ESUN material that is COMPLETLY different from this sample you show. ESUN material is now darker, well shaped and seems to work properly.

    I was also having a conversation via email with "CB Photoelectricity" that told me (in april) that they were about to have "new material" with their new machines... so I deduced that they were not selling their material and until that point they were a simple dealer.

    We started buying material to ESUN due to bad quality of the CB Photoelectricity's material so when trying ESUN material we were very carefull to get good results. At this moment we haven't reported any problem. No bad shape, no balls inside, no curly sections or any other problem. About 50 kits have been printed reporting 0 problems.

    I think that in the past this generic provider was not only providing 3D printing machines and was not meeting our needs. Seems that ESUN started their own machines and right now their materials are quite good.

    Regarding this quality issues we would like to send you a 1kg roll for you to try and to have a report. We have less experience than you in quality and detail issues and would be good for all to have a complete report that show us what is the real quality of a chinese provider in comparison with the other providers you tried in the past.


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