Hotend woes

I think my J-head is dead. My filament has been stripping even at low speeds and printing is extremely unreliable. I've been printing at some pretty high temperatures for a PEEK-barrel hotend and I only just got a fan.

I think there's a bit of some sort of junk stuck in there. I've tried clearing it with a bit of wire but it doesn't help, at least not for more than a few minutes. Is there a good way to totally clean a J-head and get it running like new?

I've heard nice things about the E3D hotend and while it's a bit out of my price range there seem to be some nice clones on eBay. I print in PLA only; how well do E3Ds work for PLA?

Are there any other tricks to try that might help me print faster with lower pressures? Is it possible to drill out the nozzle to make it bigger (it's 0.35mm at the moment) and allow easier flow?

Thanks!

What filament size are you using?

There are a few things you can do to revive your head. Fewer if you are printing with 3mm

The J-head has a brass nozzle/heat break and then for 1.75, a ptfe tube inside the peek.

The brass bit can be cleaned. First, if you've been printing ABS, soak it in acetone (easy to get, it's commonly used and cheap). For a day or two or until it is clear. I put them in a clear pot with a lid and shake it when ever I go past. The ABS will disolve eventually.

If you've been printing PLA, remove the brass part and use a chef's blowtorch to heat it up. The PLA will melt and dribble out. Keep the heat on and it will burn the stuff off. BE CAREFUL not to damage the brass part. That said, I've had one glowing red as an experiment and it worked fine after...

For the Peek, if it's damaged there's not much you can do. If you've been printing 1.75, it's possibly the ptfe that's damaged, and that can be removed and replaced.

The E3D hot ends are nice, I'd be a bit wary of fake ones if you're on a tight budget. If it turns out to be rubbish you'll have lost your cash. PLA is always a bit of a pain. I have had it stick in my E3D V6 a couple of times, but not seriously. I usually just put the heat up to 220 which unbinds it and let it extrude until the temperature is back down to my PLA temp.

Thanks for the advice!

I use 1.75mm filament. Is it okay to burn PLA? Would it leave soot which would cause clogs later?

How does one go about removing the brass part? Does it screw on?

It's fine to burn the pla, don't try it with abs though. Also, if you are a little careful it will just dribble out.
The brass part just screws in. There should be some sort of fixing nut at the end the filament goes in that comes out so can prod the page out.

Edited 1 time(s). Last edit at 09/30/2014 05:34PM by UkIan.

Nophead published this recently. How to clean a nozzle.
[hydraraptor.blogspot.co.uk]

Okay. Disassembled the hotend, cleaned the PEEK barrel with boiling water and an old dental tool. Took a heatgun and then blowtorch to the nozzle, burned out everything, leaving an ugly but probably not harmful surface. I then put it in a jar with some acetone, I'll take it out roughly 20 hours after I put it in. Let's see what happens.

Okay. Removed it from acetone and reassembled the hotend after scrubbing thoroughly with a toothbrush and toothpaste. Did a few "PLA pipecleaners" which pulled out a good amount of junk but didn't have much effect. It's running about like it was before.

100mm/min seems to work semi-reliably, but 300mm/min fails quickly. Is it reasonable to think I could get to speeds to match my delta's movement capabilities?

What temperature are you printing and what material? What speed are you doing the actual print at? 100mm/min = about 1.5mm/sec of filament which is quite slow, 300mm/min = 5mm/sec.

Pronterface is good in that you can tell it to extrude a length at a certain speed. So you could try extruding 30cm at 1mm a second and increase until you get binding. The temperature will be relevant here.


What electronics do you have? If it's ramps, it's worth checking the vref of the stepper driver. It might be the stepper isn't getting enough power. with the stepper driver potentiometer at the bottom, you measure the voltage between the bottom right pin and the potentiometer dial. A value of 0.7v is nice, but more or less can be required depending on the driver, motor and load.

I use Zen Toolworks natural PLA at 210-215C. I am pretty sure the stepper isn't skipping, would a mistuned driver cause this even without skipping?

It can sound like it's clogging if the power is too low, it pushes with more force if you increase the voltage, until you've adjusted it above its limit at which point it starts clicking and clacking and generally failing. If you can, try pushing on the filament from the top to give it a helping hand, this will just rule out the extruder, I'm not suggesting you sit there pushing for all your prints

The temperature is fine; quite high for PLA, but one thing at a time.

Have you replaced the PTFE tube inside the PEEK?

It might be good to get pronterface running, connect up and set it to extrude a long length at 1mm a second, and increase the speed slowly (the faster it goes, the more heat it draws out of the block AND the quick it needs to melt) until you find the point it starts to bind. Remember that you're not getting a 1 to 1 mapping. 1mm of filament will cover 20mm of print (or more or less, it's a thumb in the air guess and totally not accurate). I'd be surprised if you get fast speeds, but you really only need a few mm a second consistently.

Also, what speed are you printing, i.e. the speed the head moves? 30mm/s 60? 10? 100?

I have printed at a few speeds -- before all this started I could pull off 250mm/s, now I can sorta manage 50mm/s.

I'm quite sure the stepper isn't skipping. I've wached it closely as it fails, the stepper keeps turning fine. Pushing on the filament does help -- it is definitely a pressure issue.

I have not replaced the PTFE, since I don't have any extra of that size.

I'm probably going to buy a new hot end, most likely an E3D v5 clone off eBay with a wider nozzle. How does that sound?

I've just switched out my e3d hotend because it started sticking. I'm using a jHead now, which I got from a UK based person who makes them. I'm both delighted and horrified how much better my prints are using it. I don't think I'll leave JHead land again unless I start printing something that needs the heat resistance.

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epicepee
100mm/min seems to work semi-reliably, but 300mm/min fails quickly. Is it reasonable to think I could get to speeds to match my delta's movement capabilities?

It's not your J-head, or your extruder, it's your nozzle size.

Most heads, especially J-heads, are only designed for 100mm/s print speeds. The smaller the nozzle, the lower the speed.

Of the hobbs I've used, only one available hobb could consistently go over 250mm/s on a .35mm nozzle and 1.75mm filament and that is the Ultibots 1.75mm hobb. However, it is only available in 5mm I.D. The Ultibots hobb topped out at around 340mm/s on a good day, with good filament, but usually was good for about 300-320mm/s. Griffin 3d is going into production with an 8mm I.D., 1.75mm hobb capable of even higher speeds, but won't be ready until end of the month. If you want to go that fast, either get one of the hobbs mentioned, or a larger diameter nozzle, this will lower your back pressure and your extruder will begin working again.

Just so you know, all metal heads have more back pressure than non-all metal hot ends and therefore tend to print slower.
At around 350mm/s you will begin backflowing even the best .35mm head. That doesn't matter much anyhow since, your pneumatic fittings are typically only rated for 140psi (rated max), with a .35nozzle you exceed this by the time you reach 200mm/s. You will slowly destroy them and your bowden.

If you keep trying to go down this path with a .35 nozzle, things are not only going to become more difficult, but also a lot more expensive as parts start breaking. Right now, the only reason you aren't breaking parts is because your extruder is skipping before you do too much damage.


As for your slow speeds after all this, there is a few possible explanations.
Your hobb may be clogged, make sure it's clean.
Your bowden may be partly crushed and cut into. See if you can pull it out of the pneumatic fittings and check the condition. If you can't pull it out, it's damaged and has compromised the fitting as well. Leave it. Forcing it to come out will destroy the fitting. Usually the one at your extruder is the one that takes the most punishment.
You also probably increased the pressure on your idler in order to push filament harder and not slip. This tends to crush the filament, making it ovalized and this causes it to bind up in your bowden tube. This is especially problematic with ABS. Feed a bit of filament into your extruder, then pull it out and measure it to see if it's been ovalized (a little is normal). The solution is to back off the pressure.


As for cleaning...
Blow torch (outside, up wind) then a dip in rubbing alcohol does just fine. Beware, let it cool a bit before dunking, too hot and you will ignite the alcohol. Also the vapors are not good to inhale. No need for a bunch of acetone or 20 hour soaks. I do my nozzles this way in about 5 minutes.

I understand that this sort of speed is uncommon for a setup like mine. The weird part is that it worked great before -- I would regularly print at 200mm/s with 0.1mm layers, and while I'm not sure what filament speed that works out to, it's way faster than I can get now. Was I damaging my machine by doing that? Nothing seems to be damaged -- the only difference I notice is that either the extruder won't push as hard, or the hotend is harder to push filament through.

How exactly does temperature affect maximum print speed? Part of the reason I want an E3D is because with my J-head I always have to worry about melting the thing. With an E3D I could go as high as I want. I've noticed that higher temperatures reduce back pressure -- how far does this go? Would 230 be easier than 215? How about 240? Would that offset the higher pressure I'd get from an all-metal hotend?

Is the Ultibots gear really significantly better than the Mk8 (assuming you've used one)? It makes sense that the smaller-diameter curve would grip the filament more, but the Mk8 seems to be the most popular.

As for the low-speed failure: I've cleaned the gear, it helps but doesn't solve it. The tube seems fine -- there's not much resistance until the filament gets to the nozzle. The gear does make the filament ovular, but the only problem that causes as far as I can tell is that it sometimes folds and jams in the extruder.

Also: One other reason I decided to get an E3D is because the all-metal design would be harder to screw up by some cheap Chinese manufacturer, while fake J-heads often are missing the PTFE or have other sketchy modifications. Is there somewhere I can get a reasonably-priced (<$50), good-quality J-head?

And one more question. How much of a difference does nozzle size make? If I want to hit 250mm/s with 0.1mm layers, what size would I need?

Edited 2 time(s). Last edit at 10/04/2014 05:53PM by epicepee.

I got a couple of J-Heads from this guy. I'm using one now,it's actually replaced my E3D hot end which was having some issues and it is working perfectly with a 0.4mm nozzle.

Question: When you talk about wanting to hit 250mm/s, are you talking about printing at 250mm/s or extruding filament at that speed? I'm guessing it's the latter and you mean mm/min, or something else?

I mean moving the head at 250mm/s. The head can move with good precision at around 400mm/s before the vibration and acceleration starts to become a problem; I could probably crank it higher if I needed to.

It's a delta right? Did you go for a kit, or all home made?

Yeah, it's a modified Kossel Mini. I did not use a kit, though I did buy the Delrin roller carriages. If you've never built your own printer, do it. It was the most fun thing I have ever done.

I've just built my first, but not a delta, and I'm looking for something to do for a second one

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epicepee
I understand that this sort of speed....

I'll keep this short, and yes, this is short as there are just a lot of hurdles in front of you and what you really need is a lot of money and/or a book....
For a Kossel Mini, I'll just say it's VERY rare to hit the speeds mentioned.

Adding heat helps melt, especially at speeds. The more liquid it becomes, the less back pressure, however, there is a downside, the more fluid it is, the more it will backflow out the top of the head.

I only got an MK8 the other day for testing but I have yet to actually test it. However, based on the look of it, and past experience, the biggest benefit over an MK7 with 1.75mm filament will be with ABS. The MK7 was about 10% slower with ABS than with PLA, and was very fickle with adjustment. I suspect that will no longer be the case, but it will still be 25% slower than the Ultibots hobb.

As for why it working great before and not now, this goes back to ovalizing your filament. As you went up in speed, you tightened your extruder more and more. This ovalizes the filament increasing friction in the tube, but also damages the filament causing it to try and fold/curl. You tightened the pinch increasing friction, it slips so you tighten it more to overcome the friction, making it flatter, adding more friction so you tighten it more. See the cycle? Eventually the filament becomes damaged and soft enough that it finds an easier route, you also may be softening it with heat from your extruder. Cut off the used filament, loosen your extruder way up, and try a slow print slowly increasing tension. In other words, start fresh.

Head woes...
You bought a clone. Will the E3d be better, I don't know, every clone is different (some good, some bad), but you can't use your clone J-head experience as evidence that J-heads are bad. Especially when you are are exceeding the recommended speed by 300%. When you start increasing speeds and pressures, all bets are off. I've used several heads and I always come back to the real J-head. It just works.


Where you really stand.
You have two paths to go here, the "easy" 300mm/s by using a .4mm nozzle, or the hard path, which is using a .35mm nozzle. Common off the shelf parts, are NOT up to doing 300mm/s on a delta, especially on a .35mm nozzle. We did it, many times in fact, but you have no idea how many parts we broke or tested, how many hours of research and how many manufacturers we contacted to do it. In the end, we could have bought a pretty nice printer for what we spent just getting from 220mm/s up to 300mm/s.

I'll be honest, by the time you reliably hit your goal, a large portion of your Kossel will have to be replaced. Here is the short version...
Your electronics are struggling to keep up, 32bit is needed
This necessitates a power supply change, but you probably need more anyhow as the 5amp psu is actually under powered.
You can use a geared extruder with the Ultibots hobb, or drill it out for a geared stepper or get a Griffin Hobb. MK7 will NOT do it, 8 probably won't either.
You will need stronger pneumatics and matching bowden (have fun! with testing).
You need to stiffen the frame
You need to find a way to dampen the effects of all of this on your rod ends or they will develop a ton of slop fast...
A MUCH bigger cooling fan (and forget doing ABS at speed)

That's a good start.
If you use a .4mm nozzle, you can probably use the Mk7, and your current bowden setup. Most of the rest still applies.

My advice, if you really want .35mm, buy a Griffin Pro and swap the nozzle. It will save you a lot of headache.

Clarification on a few points:
I have a MK8, and I have no plans to buy a MK7. I might buy a Rapman drive gear, but it is likely I will stick with what I have.
I bought my J-head from Reifsnyder on Amazon, which I believe is the official supplier, for about $60. My information about fakes comes from elsewhere.
I can and have printed at 200mm/s with few issues. I know it will take effort, but I do believe my machine can hit 300 without very much modification. I've added some custom supports which make the frame much more rigid. I have big steppers on DRV8825 drivers; I have no doubt my direct-drive extruder could handle that speed with a MK8 or Rapman (assuming the filament doesn't strip).
I have reloaded the filament more times than I can count. I have tried four different spools. The issue is with the printer, not the filament (though if the printer is continuously making the filament ovular, that could be a problem; I'll have to hand-feed some after it fails at some point).

How much of a difference is 0.4mm from 0.35, both in terms of extrusion rate and print quality? How about 0.5mm? I don't need ultra-precise prints, I care more about reliability and no strings/blobs/etc. Would switching to 0.4mm simply solve my problems?

How would a real E3D v5 or v6 compare to a real J-head, in terms of flow rate and pressure? Keep in mind the E3D can get quite a bit hotter than the J-head.

And one last question: Is it normal for a drive gear to get worn down over time? If so, is there an easy way to tell how worn mine is?

Edited 1 time(s). Last edit at 10/05/2014 07:37PM by epicepee.

The difference in pressure from .35 to .4 is quite a lot.

Direct drive with zero gear reduction, more than likely not going to happen with the .35 mm nozzle, not without the motor needing a heck of a heatsink. I don't even like recommending .4 for direct drive at slower speeds, it lacks power when anything goes wrong at all. The power needed to go from 200mm/s-300mm/s increases very quickly on a .35 nozzle. Hitting a speed is one thing, doing it reliably is entirely another.

Again, all metals have more back pressure than real J-heads. How much, I can't say.

Hobbs should last a long time, some actually get better as they wear in.

Nozzle size has little effect on print quality. It allows finer points and smaller walls. Layer height dictates quality much more. Low layer heights cause nozzle pressures to skyrocket.

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epicepee
I think my J-head is dead. My filament has been stripping even at low speeds and printing is extremely unreliable. I've been printing at some pretty high temperatures for a PEEK-barrel hotend and I only just got a fan.

I think there's a bit of some sort of junk stuck in there. I've tried clearing it with a bit of wire but it doesn't help, at least not for more than a few minutes. Is there a good way to totally clean a J-head and get it running like new?

I've heard nice things about the E3D hotend and while it's a bit out of my price range there seem to be some nice clones on eBay. I print in PLA only; how well do E3Ds work for PLA?

Are there any other tricks to try that might help me print faster with lower pressures? Is it possible to drill out the nozzle to make it bigger (it's 0.35mm at the moment) and allow easier flow?

Thanks!

This hotend was designed specifically for PLA 1.75mm
It can be used in many ways including Bowden, Wades, E3D, 50mm plate holes, etc.
Check it out at URL

---

[regpye.com.au]
"Experience is the mother of all knowledge." --Leonardo da Vinci

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sheepdog43
Direct drive with zero gear reduction, more than likely not going to happen with the .35 mm nozzle, not without the motor needing a heck of a heatsink. I don't even like recommending .4 for direct drive at slower speeds, it lacks power when anything goes wrong at all. The power needed to go from 200mm/s-300mm/s increases very quickly on a .35 nozzle. Hitting a speed is one thing, doing it reliably is entirely another.

Does this mean you would recommend 0.5 for my setup? (I do have one heck of a heatsink.)

Absolutely.
Direct drive is great for .5mm nozzles, makes for a dead simple setup. I recommend the Ezstruder from SeeMeCNC, it's a fantastic extruder.

I think I'll stick with my extruder if I can; I don't have enough free cash to buy another if I don't have to.