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Wow, .1mm is pretty fine resolution and will take a long time to print! Most of my work is .2mm with a .4mm nozzle.

mhackney wrote:Wow, .1mm is pretty fine resolution and will take a long time to print! Most of my work is .2mm with a .4mm nozzle.

Yea, its time consuming. But im working on something for a special project that needs the resolution.

Nope, Jammed again!!! S O B M F P O S A L C S M F

Ok I will tear it down now and measure in the morning LOL

The heat break is clear, the jam appears to be in the nozzle itself...Seeing thru mhackneys eyes right now....cant wait to measure

I have a .4mm drill bit that I was thinking about adding a small plastic disk so that the disk was approximately .5mm from the end. The disk could be adhered to the bit with super glue.
After drilling the Nozzle I could use the above bit and disk as a measuring device if I left the drilling bit in place and place the .4mm bit with disk in the front of the nozzle to act as a measuring device.

Michael, or anyone, please comment on your opinion of the above. In my mind it should work but I wanted to get other opinions, my old mind doesn't work as well as it once did.

Ok here is the measurements. Drill bit 70.80 MM long, put the nozzle on it and measured 71.45 MM.
Felt like there was something in the bottom of the bore snagging the drill bit so I spun it with my fingers intil it smoothed out, the remeasured 70.95 MM
Something seems off here, but im going to try re printing....

Eaglezsoar wrote:I have a .4mm drill bit that I was thinking about adding a small plastic disk so that the disk was approximately .5mm from the end. The disk could be adhered to the bit with super glue.
After drilling the Nozzle I could use the above bit and disk as a measuring device if I left the drilling bit in place and place the .4mm bit with disk in the front of the nozzle to act as a measuring device.

Michael, or anyone, please comment on your opinion of the above. In my mind it should work but I wanted to get other opinions, my old mind doesn't work as well as it once did.

The issue with something like this is accuracy, 0.5mm just isn't very big, your much better off removing a tiny amount of material and remeasuring.
I did mine on a lathe and even there I did it in 3 or 4 passes, remove small amount, measure, repeat, because your talking about removing a fraction of the width of the drill your using.

Thanks, Polygonhell. What you are saying makes sense.
After taking a caliper and actually seeing that .5mm is barely over the width of a human hair, I realized that my idea was poorly
thought out. Measuring distances that small is probably best done with Michael's method of heating the PLA, inserting it in the nozzle
and freeze it to get a more accurate measurement. Even with that measurement .5mm is very small.

Does anyone here have a reprapdiscount Hexagon hot end? If so, could you measure the nozzle bore length to add to my collection? There are reports that it has troubles with certain PLAs that the E3D does too and the J-Head does not. Given how "similar" the Hexagon is to the E3D hot end, they may have fallen into the same trap and have a bore that is too long.

No matter how all of this pans out, I am very happy with my Kraken and E3D hot ends now with .5mm long nozzle bores. I've had ZERO failures printing literally 2 dozen different PLAs (different companies, different colors) at high speed with great looking parts. This is one of those situations where I really want to share my joy and jubilation with everyone that is having problems with PLA and the E3D. It may very well be an isolated issue, we don't really have much data on how many of these have been sold, but I do know that I've received over 30 emails and PMs from several forums from all sorts of printer owners telling me they measured their nozzles and they were all over 1mm, that they were having so many problems that they've given up on PLA with the E3D and that they made the mod to the nozzle and now are very pleased with it's PLA performance. In any event, I've learned a lot about measuring and testing hot ends!

cheers,
Michael

The one thing that I have learned is that .5mm is very small!

I know someone who has that hotend, ill see if he can measure it for you.
Since I drilled mine it hasnt clogged, I think there was a nib of brass in the bottom of the bore that was causing the issue. I have run 4 prints now all at .1 mm
and 2.5 hours long with no more issues...

Excellent David. Thank you.

.5mm is pretty small!

The is interesting....

I had several forum members here and on the E3D forums ask me if I would modify their nozzles. They were plagued by PLA jamming problems and wanted to see if this would work. I wanted to collect some more data on nozzles so I agreed to do a few of these.

Well, today I received 2 nozzles from 2 different people. One nozzle measured 1.01mm bore and the other was 1.12mm. Both users had given up using these nozzles for PLA. So, first I mounted them in my Kraken and then attempted to print a part I know causes jamming problems. Sure enough, both nozzles, even though they had "1mm" bores jammed. I modified the nozzles, shortening the bore to .5mm and now they both are printing beautifully.

That's actually fairly interesting, I'd have thought that ~1mm would probably be fine.
But your experiment seems to show it's at least a significant contributor to the issue, I wonder if there is some other issue with the machining of the inside of the nozzle, or whether it really is just the increased back pressure exacerbating the natural propensity of PLA to jam.

Interesting and I wondered about that too, perhaps the drill is smoothing a bur or chamfering the inlet to the bore or something along those lines. If I had another one to try out, I would remove very little material and retest to check this theory.

On my nozzle I would have to say there was a nib in the bottom of the bore. I felt the drill bit snag on it. It only took a couple twists back and forth to clean it up.
If they drill the 2mm bore, then flip the nozzle to drill the .4 mm hole it could well be raising a burr where the .4 mm bit enters the 2mm bore.

That's a great observation. I've noticed a snag too when I use the drill in my fingers. In fact, I twist the drill in reverse once and that eliminates the snag.

Just to be a bit off the wall, water flowing thru a pipe sort of thing....pressure would be increased before the restriction and not after it....

mhackney wrote:That's a great observation. I've noticed a snag too when I use the drill in my fingers. In fact, I twist the drill in reverse once and that eliminates the snag.

That's what I did exactly!! And got small brass chips out off the bit. Didn't really drill it out at all, just smoothed it.

An interesting observation. It would be interesting to try some known "plugger" nozzles and simply do the debut step and then test.

Do you still have that piece of filament you used to make a test plug of the bore?? Maybe it will tell us a story...

I'll have to look and see if I still have some. You are right though, it might show the defect.

One more off the wall thing, if thier using a 2mm gun drill the tip on them is usually very flat and when we re drill them were adding a cone to the bottom of the bore that might be helping direct the filament into the tip, possibly reducing back pressure???
Could the printer itself be used to measure drag? Possibly by backing down the pots until the motor stalls and recording the settings to see what improves the design??
Someone needs to slap me, I'm obsessing about this now...LOL. can't resist a challeng!!

I sent mhackney my .4 nozzle to get modified. I did not trust myself to adjust it such a small amount. Also I wanted to have it adjusted in the same fashion to help reproduce the results. I had measured the plug to be just over 1mm.

DavidF wrote:Do you still have that piece of filament you used to make a test plug of the bore?? Maybe it will tell us a story...

I found two of my plugs that i measured and used a usb microscope to look for any signs of a bur and could not find anything that stood out. The white pla has enough of a gloss that the light makes it had to get a good picture.

I found 2 of mine also and no signs of a bur.

But, the angle of the cone leading up to the orifice bore is very flat on the stock nozzle and I'm using a 118° 2mm drill. That could also explain the initial "snag" and would result in a more gradual flow up to the orifice. It might be a combination of these as well.