Brand new V2 Hot End clogged with Ninjaflex Cheetah flexible filament

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Nerraw
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Brand new V2 Hot End clogged with Ninjaflex Cheetah flexible filament

Postby Nerraw » Thu Jul 20, 2017 4:44 am

Hi all,

I just installed the V2 hot end on the printer to try printing with Ninjaflex Cheetah flexible filament. It was building the raft of my first non-test print when it stopped extruding. I let it go for a little bit, hoping it would resume extruding and just leave a defect, but it did not.

I unloaded the material in hopes to re-load, but then when I tried to re-load I couldn't get it going again. I took off the clear plate/filament guide and tried a few more things. I pushed down with the metal cleaning rod, but it didn't force anything out. I got some guitar string to feed through the nozzle and it got jammed. I was able to force it through from the bottom but it wouldn't actually unclog the nozzle and next time trying to push it through it would just get jammed again. I was never able to push the guitar string through from the top though.

I suspected that the string was hitting the filament but it should have felt gummy if that were the case. It felt more like it was hitting metal. Is there something a ridge in the hot end where the filament feeds in that would prevent the guitar string from feeding through? If I push the string down and measure how far it goes down, it seems to get stuck near the throat.

So I'm unable to push the filament even far enough for it to start melting. My next step will be to remove the nozzle (already tried but had a hard time of it -- read a few things to help me try again). Then I guess hopefully clean out the nozzle or the throat, or at least see where it's plugged.

But I'm kind of confused why the filament won't even start melting and yet the guitar string fed in from the top seems to hit a metal barrier (I could be wrong on the feeling of 3 inches of guitar string hitting metal I suppose). Any ideas or insights?

Thanks,
Warren

Jetguy
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Re: Brand new V2 Hot End clogged with Ninjaflex Cheetah flexible filament

Postby Jetguy » Thu Jul 20, 2017 11:18 am

Please look at this crude diagram I made a while back. There are gaps in the feedpath and this is likely where you have filament that is causing your issues. There is a gap between where the internal PFTE guide tubes (the white parts) and the metal entrance to the cold section of the hotend in the throat tubes. The entrance to the throat tubes is tapered or cone shaped and while that works great for typical hard filaments, this cone and worse the gap gives flexible filament a place to buckle and snake around rather than pushing.

My fix was I drilled out one of my white PTFE guides (originals from Kickstarter where a different plastic than new ones) and inserted a 2mmID, 4mm OD PTFE tube down the enlarged bore and made it longer than the original white guide so that the tubing butted up against the entrance to the V2 (or V1) hotend.

extruder cross section.jpg


Here is a modified PTFE Guide with the inserted longer 2mm ID 4mm OD tube extending out the base.
DSC04670.JPG

DSC04669.JPG


Then this picture shows why the hotend leaves the gap. The thickness of the lower plate that bolts to the central cross that the hotends (V1 or V1) slides up into is thicker than the actual mounting point on the hotends. This is what allows you to adjust the nozzles up or down slightly to match for dual nozzles. But at the same time, that adjustable gap is not zero and there is always some gap which can be problematic for flexible filaments giving them a place to buckle under pressure.
Again, details of this picture. The stock white PTFE guide tube ONLY extends to the bottom of the central cross metal block that has the bearings. The lower plate that actually screws up to that with 4 long screws from the top of the central crossing block is thicker (what is shown in the picture with a V2 hotend pushed up against the base still leaves a gap).
DSC04671.JPG


This last picture just shows the entrance of the V2 hotend is conical and larger than 2mm. This too slightly gives flexible filament a place to compress and buckle rather than pushing filament further to the actual melt zone and nozzle.
DSC04672.JPG

Jetguy
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Re: Brand new V2 Hot End clogged with Ninjaflex Cheetah flexible filament

Postby Jetguy » Thu Jul 20, 2017 11:34 am

Here are 2 more pictures to better show you what is going on and my personal mod.
This first one shows you exactly where distance wise the white quide sits in relation to the metal block and again note the parting line of where the upper central cross block with the bearings VS the lower hotend mounting plate mates. This is why the guide must be extended in some way to actually mate all the way to the entrance of the V2 hotend.
DSC04675.JPG


This second picture shows how that guide tube bridges the gap between the stock white guide and the actual hotend entrance.
DSC04673.JPG


The other logic of why I went to this effort to drill out a white guide and insert a single piece longer tube inside VS other potential fixes or mods.
The idea is that even the tiniest gap or every time you interface 2 different sections of guide, there is a potential ridge or friction point for filament to slide past. By using PTFE tube in one continuous piece, I make the smoothest friction free guide path I possibly can without gaps or joints before the hotend.

You could design or make a spacer with a guide tube that just went above the hotends before inserting them. It just needs to center a 2mm ID hole. However, a printed guide, the layers themselves inside the hole make friction especially against rubbery flexible filament.

You could cut and insert a small short PTFE guide tube inside a printed part like the above all printed spacer, however, that again means a transition from the exit of the white guide to your now added PTFE, and then another transition to the hotend entrance.

I'm saying, there is more than one way to handle this, I just think my way gave the absolute smoothest and friction free path without major mods to anything but the replaceable white guide. Spare guides are sold in the store in case you mess one up making this mod or want a spare stock one (also, ignore Raise 3D link names as when they set up the store, to make product pages they copy some pages to make a new page for a part resulting in a page name or link that is kind of mismatched to the actual part) https://www.raise3d.com/collections/acc ... zle-throat

Jetguy
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Re: Brand new V2 Hot End clogged with Ninjaflex Cheetah flexible filament

Postby Jetguy » Thu Jul 20, 2017 1:49 pm

Also, I realize now that when I did the Bondtech BMG testing specific to showing pressure for Ninjaflex (not the newer Cheetah), I was NOT using a modified tube at the time so again note the pressure difference.
That series of posts starts here and continues to the next page viewtopic.php?f=4&t=1709&hilit=bmg&start=120#p16378

Again, I'm realizing that while testing was what I feel an accurate representative sample of what you or anyone with Raise 3D printer would see "out of the box", I only just now realized I know that all that testing was done without this extended PTFE tube installed as a specific mod in the past I had used with ninjaflex.
I guess this warrants another round of testing of difference with and without this tube mod.

Also, I should post the details of how to change this tube out. Basically, just remove the hotend using the side setscrew under the fan and the front facing M4 screw on the central cross block and from the top, press down on the white tube and they come right out the bottom. They are a tapered fit so some force might be required. Inserting is opposite, again, just push in from the bottom up, then insert the hotend. You should not even need to remove the heater and thermocouple, the hotend can move out of the way enough to let this slide in or out.

Jetguy
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Re: Brand new V2 Hot End clogged with Ninjaflex Cheetah flexible filament

Postby Jetguy » Thu Jul 20, 2017 2:31 pm

Hmm, I didn't realize this until I pressed out a stock white guide tube and compared it to my modified version, it appears newer versions may partially address the previous gap as found in my Kickstarter N2 tube?
DSC04688.JPG

Honestly I don't 100% know the answer here as this is a unique to your printer specific detail.

Just a tip either way, how you went about checking for this "clog" is prone to other failures.
By that, I mean never, ever, remove a nozzle unless you are absolutely 100% sure the nozzle is clogged.
Because the seal of the nozzle to the throat tube is so critical, because this is the exact step people break throat tubes left and right, because a leak here is a total disaster later, because people constantly strip setscrews and other mistakes...

The first step should have been simply loosen the hotend and let it hang down and pass the wire through the upper white guide and examine the entrance of the hotend. Again, because the entrance is cone shaped, a huge number of jams is where melted filament is pulled up on an unload (failure to follow the #1 rule of always load or feed filament BEFORE pulling it out to reduce the melted tip to the bare minimum) results in a bit that cools but will not push back down into the cone. You cannot easily get to it to pull it out from the top when the extruder is assembled and you cannot push it down through because the cold end cone entrance will never melt it (it's the cold end).
DSC04689.JPG

Again, the FIRST step is try the rod as supplied with the printer.
The second step is the wire up through the nozzle.
The third step is loosen the hotend, examine the entrance cone to the hotend.

I cannot stress enough, many, many jams are right here at the cone entrance to the hotend.
DSC04690.JPG

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Brandon
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Re: Brand new V2 Hot End clogged with Ninjaflex Cheetah flexible filament

Postby Brandon » Thu Jul 20, 2017 2:33 pm

Are you using a brass .4 nozzle or the hardened .6 or .8 mm nozzle?

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walshlg
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Re: Brand new V2 Hot End clogged with Ninjaflex Cheetah flexible filament

Postby walshlg » Thu Jul 20, 2017 2:55 pm

fwiw, I found that the brass 400um nozzles worked but the steel coated ones would not work with ninja.

Jetguy- this would be a great place to use that super-slick ptfe tubing!

Jetguy
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Re: Brand new V2 Hot End clogged with Ninjaflex Cheetah flexible filament

Postby Jetguy » Thu Jul 20, 2017 3:30 pm

FWIW, I printed with V2H nozzles, not brass stock ones using Ninjaflex, but that also was the new BMG feeder too.
I absolutely know that has been said several times here that brass stock nozzles work better for Ninjaflex, but again, my personal experience did not tell me that V2H would not work. I have printed with the stock feeder system and both brass and V2H nozzles (way back when the V2H was being developed) and couldn't definitively say that somehow brass was superior or the only way to print Ninjaflex.
Just timeline wise, V2 hotend was produced, then V2H nozzles, then later came Bondtech upgrades. Absolutely, I know I printed with Ninjaflex, a stock feeder and various V2H nozzles before they were even released.

Agreed, I just bought like 8 meters of that super slick PTFE tubing for various projects. https://www.captubes.com/index.html#products

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walshlg
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Re: Brand new V2 Hot End clogged with Ninjaflex Cheetah flexible filament

Postby walshlg » Thu Jul 20, 2017 3:56 pm

Jetguy - IF I make these lined guide tubes, should I switch them out when I go back to regular filaments?

Jetguy
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Re: Brand new V2 Hot End clogged with Ninjaflex Cheetah flexible filament

Postby Jetguy » Thu Jul 20, 2017 4:02 pm

No need to switch back. It's just IF you print flexible filaments, there may or may not be a gap and it's exceedingly difficult to detect and measure that. It's just how the assembly stacks up. So again, if you are printing flexible filaments and have jams, this is one possible fix.
If you do make the fix, this is universal for all filaments. It's not required for rigid filaments because they tend not to buckle, but again for flexible filaments, if there is a gap between the exit of the white guide tube and the entrance of the hotend, this is one place Flexible filaments can buckle and jam and fool the user into thinking the hotend is a problem when it never actually was the hotend.

Jetguy
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Re: Brand new V2 Hot End clogged with Ninjaflex Cheetah flexible filament

Postby Jetguy » Thu Jul 20, 2017 4:36 pm

Just a recap test, using my mod white tube, ensuring that there was no possible gap, using a Bondtech feeder and genuine Ninjaflex (not the newer Cheetah) I got 0.55kg max force as tested by my rig. Also, looking back at how I tested earlier, I don't think I had the gap even when testing previously without a modified tube. The reason was that without a heatsink on the V1 throat tube used, I always ensured I pressed it up when installing for the test and thus unlike a real hotend, my testing eliminated that gap so retesting is not required although the idea of the super slick tubing version and seeing if there is a difference is not a bad idea.

This is why Flex filaments just can be a real pain in the neck to print. They simply do not have the grip and the same force at the nozzle as rigid filaments. In some cases, it's nearly a 10:1 reduction in force compared to rigid filaments per my testing.
Attachments
DSC04692.JPG

Nerraw
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Re: Brand new V2 Hot End clogged with Ninjaflex Cheetah flexible filament

Postby Nerraw » Thu Jul 20, 2017 11:23 pm

Wow thanks for all your responses Jetguy.

I'll respond to Brandon first as that's a simple question: I am using the brass 0.4mm nozzle, but I just ordered a 0.6mm steel one from the store.

So, I managed to get the nozzle off last night. There was no clog in the nozzle, however there was a clog in the throat. I managed to push a guitar string through it, but couldn't get it out with that, but it did make a hold in the material. Then I used the cleaning tool to push the bit out. There was about 5 mm of seemingly un-melted filament stuck in there. When I came back to try printing again today, I went through everything with the cleaning tool, but I seemed to be unable to load filament, it was stuck in a different place. It appears I scratched up the PTFE tube. Good thing I had ordered another one. So I replaced the PTFE tube and made another attempt.

Currently printing a 3dBenchy and all is looking very good! I switched it so the max speed is 25 mm/s. It makes sense, if you give it time to melt then there will be less pressure buildup pushing back on the motor. Seems like there could definitely be a better design, ie the closer the motor to the hot end the better. Regardless, it's looking pretty good on this run. I'll report back when it's done.

Also now that I have a scratched up PTFE tube I might just try your hack, Jetguy. However, the new tube I ordered seemed to have a pretty flush fit. I pushed it up into place with the hot end so there should be as little gap there as possible, but I see what you mean about filling up the conical insert in the hot end.

Warren

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walshlg
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Re: Brand new V2 Hot End clogged with Ninjaflex Cheetah flexible filament

Postby walshlg » Fri Jul 21, 2017 4:32 pm

If you had an isolation tube clog then you can sometimes get it pushed out but with a layer of plastic still sticking to the sides- to check and to clear this, take off the nozzle, heat it up, I use 250C and let sit for an hour. Then push the 1mm rod through repeatedly -> in the top and out the bottom only. Any melted filament will be stuck to the ends, cool the rod between each pass.

Nerraw
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Re: Brand new V2 Hot End clogged with Ninjaflex Cheetah flexible filament

Postby Nerraw » Fri Jul 21, 2017 7:44 pm

When you heat it up to 250C, do you do it in the printer or in an oven? I tried warming it in the printer, but I was worried it would transfer too much heat to the cool end so I left it hanging from the heater/thermometer wires... melted some of the fan shroud... oops.

Was thinking an oven would be a good way to melt it out... but also a drill press. One of these things I have in my kitchen, the other I don't. Hopefully it doesn't clog up for a while. My last test print at <25 mm/s seemed to work much better, just not forcing it in faster than it can melt I guess, is the best option!


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