Hello, I just bought a 3D printer kit, my 1st and the cheapest (200 US) I could find on Aliexpress. I know… I know… but that is the budget I had for yet another toy. I want to print various small mechanical parts in PLA with it. I really do not mind about printing speeds or fine details and really thought that even a cheap printer would work well enough for my current needs.
So I got this kit assembled just fine but for about 3 weeks I have not been able to extrude anything half decent with it. Technical support and communication with this Chinese vendor is torture and I have given up completely dealing with them. Mechanically, that kit proved to be a pleasant surprise as the XYZ movements are smoother than expected. My problem is with the hotend/extruder assembly only. The extruder assembly is a cheap MK8 type that just always gets partially or fully clogged. I am getting really good at disassembly, clearing clogs, reassembly only to find out that my problem just reappears. I can’t get more than a few seconds of what I guess is a normal extrusion volume before I get (again) partially clogged. I just can’t find ‘THE problem’ as everything looks ok to me. I read about bad PLA but can it really get that bad ??
Being a total noob at 3D printing I have a thousand questions but will start with just a few…
I found the hard way that you have to tighten the nozzle to the throat inside the heating block but wonder about that PTFE tube that often gets clogged solid requiring full disassembly. Currently the PTFE tube is not quite flush with the end of the throat. Should it be set in more inside the throat or to the contrary extend inside the nozzle itself !?
I have been digging YouTube and now this forum for info about Extruder/hotend. I see a lot of ‘This is how you unclog your extruder’ but this is not what I need. I am looking for a more in-depth tutorial for what causes clogs and jams and how to generally prevent them with various Extruder/hotend. Any suggestions ?
I am thinking of completely replacing that cheap MK8 and was looking at the well reviewed E3D V6 (or possibly a clone of it ?) with a direct extruder but can’t find an off-the shelf kit that I can simply swap in. Any suggestions ?
I just can’t wait to start printing, thanks in advance for any help !
There are a few basic reasons for clogs and jams: Either something is obstructing the nozzle hole, or your filament is becoming molten too high up in the hot end.
If you’ve come across the directions for a “cold pull”, that’s the solution for something obstructing the nozzle. That “something” can be many things from burnt filament bits caused by leaving the hot end hot with filament to bake in it to inclusions in the filament or metal burrs left over from quick cheap machining that have broken off in use.
If you’ve seen anyone describing “heat creep” that’s what’s behind your filament becoming molten too high up into the hot end. Normally, in all metal hot ends, this is avoided by having cooling fins and a fan on the part of the hot end that you don’t want to be hot. I’ve seen the cheap Chinese hot end your printer seems to have come with in pictures, but I don’t have any personal experience with it, so I’m not sure if it uses a fan to avoid heat creep or not.
PLA is especially susceptible to heat creep, because it softens at a relatively low temperature and becomes sticky when it has softened. That’s why your hot end has a PTFE tube in it, because softened PLA will like to stick to metal sufaces if they are at all warm and aren’t perfectly smooth.
You may be able to rescue the hot end you have, you could try aiming a fan at the metal bits above the heater block (but not at the heater block itself, that’s important) and see if that helps. If that doesn’t do it, you could do a few cold pulls to make absolutely sure the entire filament path is clean and clear. But those only might work.
The best fix would probably be to replace the hot end entirely. The E3D hot ends are all very good, and I’ve had great success with them, but make sure you buy one from a legitimate distributor and not a clone from ebay or aliexpress. As you’re already seeing shoddy machining in a hot end can leave it pretty well useless, and shoddy machining is the order of the day with Chinese clones especially hot ends, so it’s very much worth paying the extra cost to get the real thing.
@Stephen_Baird Thanks for the info. I do have a small 40mm fan continuously on trying to cool a solid metal block without any fins on it. Is is just tightened to the extruder motor.
It does not look like much of a heatsink but, in my experimenting, I have removed that fan completely to see the extrusion gears etc… and was very surprised to notice the block did not get warm much even after a few minutes of the hot end at 200°C without
My brother-in-law once said: “Education is never free”
Not sure if this is where your problem lies, but heat-creep is the Achilles’ heal of hot-ends. You need the tip hot enough to melt the plastic, but the barrel needs to stay cool enough to prevent the plastic from getting soft (and therefore fat) too soon. The heat from the tip creeps up the assembly and starts to prematurely melt the plastic. (On a related note: overheating steppers lose strength and can’t push as hard - make sure your extruder stepper is not too hot to touch).
Engineering designs that address the heat-creep include: heat breaks between the tip and barrel, cooling fins (and fans) on the barrel, PTFE lining of barrel to reduce friction when the filament (inevitably) swells, etc
Configuration parameters you have to play with: temperature setting (go as cool as possible), feed rate (start slow - faster speeds have tighter tolerances around the ‘right’ temperature), layer height (the finer the layer, the more back pressure - at least that’s what I’ve observed), filament diameter - if you’ve made an assumption or measured wrong, your slicer might be trying to push too much through too fast causing the jam (ie: is the slicer assuming 1.75mm, but you’re feeding 3mm filament?, or did you measure 1.8mm, but entered 1.6?).
@Nathan_Walkner yeah good price but for now it is a wasted $200
Slicer is set for 1,75mm. Thanks for the suggestion. Note that I have played with this a lot and even tried to push the filament in by hand without positive results. If I can’t push the filament by hand, I figured no small motors or slicer settings will help.
Can’t push filament by hand? that’s a problem. Make sure to clear obstructions, then “calibrate” your hot-end temperature senor: ensure active cooling on the barrel and start at 175C and increase in 5C increments until you can push by hand. Then try and print at that temperature. Might be that the sensor is wrong. PLA should print between 180 & 210 depending on lots of variables.
@Nathan_Walkner I use a resistor’s lead (measured to be exactly 0,4mm) to clear the nozzle many times. Also burned the nozzle with a torch a few times but still never more than a few seconds of decent extrusion after that !?
@Stephen_Baird when the extruder is fully assembled, there is in fact a small square heatsink with fins that gets squeezed between the fan’s body and the block where the throat screws in. It is actually quite cool to the touch even after the hotend is at 200°C for a long time.
@Nathan_Walkner , I did try to raise the temperature up to 240°C thinking that maybe I got ABS instead of PLA in my sample filament but that did not help actually got the plastic to smoke a bit at that temp but it did not help. I confirmed that I did have PLA but I wonder if I can get my hands on a calibrated heat sensing tool to monitor the hotend at various temp settings ?
It sounds like there might be something working its way into the nozzle. Try a slightly modified cold pull where you bring the nozzle up to temperature, then extrude by hand until it’s hard to do again, kill the heater, and keep periodically pressing down on the filament to keep whatever is in there near the nozzle. When the temperature drops enough to solidify the filament pull it back out, chop off everything that was in the hot end plus a couple inches, and do it again. Repeat it until it’s not hard to push through by hand anymore, or you’ve done it four or five times.
If it’s not working after that many tries it’s probably something else.
If you have access to nylon filament use that, it tends to work better, but it can be done with PLA as well.
I have an apparently identical model from a different ali- express vendor. i haven’t had any jams. I was having problems with the hob not being tight enough so I removed the heat-sink and that fan since they interfered with tightening it and didn’t serve any purpose.
I’ve made an adapter place to use the E3D style hotend but haven’t installed it yet.
@Nathan_Walkner Interesting… I did actually do something similar although I did not precisely measure the filament. I marked the filament on top with a marker at approx. 10mm, extruded 10mm and the mark moved down to the mark. What about that stepper driver !? What is it I can check there ?
@Eric_Davies Where did u get your printer ?
I tried hard to get some technical support from O&Fine but that is worst than getting my teeth pulled out !!!
My extruder does not have any mechanical tension adjustment. That screw on top is simply a centering screw preventing the spring inside from moving around. What about yours ?
@Nathan_Walkner I thought my control board did not have any adjustments but after that comment I double-checked and did locate the smallest metal trimpot for each of the stepper motors and now wonder about their setting. Where can I get a good instruction video on how to adjust them things !?
@Nathan_Walkner , Stephen Baird thanks for the great info. Also located some YouTube videos that cover that subject ! I will play around with this for a while and see if I make some progress with my extrusion problem.
