Well something has stopped me, lol, the filament tube goes into the hot end through one of those cap things that are a push to fit and then it never comes out. Grrr. I am now left with a short piece of filament stuck in there and there is no way to get the tube back out that I can see, so I will have to see if that comes as a spare part.
Anyway just before that happened I printed these two halves of a hatch for the Kodiak.
Very impressed with the quality and speed of printing, and soon as it is up and running again I will be back seeing what I can design and print.
RobG
PS - Its all your fault that I embarked on this little game.
I cleared a block by heating up a drill bit, twisting it into the blockage then left it to cool down for a few mins. Then clamp the nozzle in a vice and heat it up with a lighter and pulled the drill bit out (twisting it the same way as before) and the blockage came straight out.
I ran the hot end up to 250 degrees, but that didn't work, all it did was melt out the PLA that was in the metal part, and left the hardened part in the PTFE union. I used a pin drill to loosen the jam and eventually managed to pull the filament back out from the extruder end, but it snapped leaving the blockage in place. I didn't realise it wasn't meant to be like that at the the time, but when I removed the union the threaded part of the hot end had a loose 5mm length at the top, I now realise that somewhere along the line the thread has snapped, and this is most probably what caused the feed to jam up.
I assumed during the testing that the problems that I had with the tension on the feed gear were just down to me getting the tension right, but my guess is that the thread was broken all along and causing issues inside the hotend between heating up and cooling down, gradually building up a blockage.
Luckily the guy that designed the printer is on the same forum as me, so I have been chatting to him about the build and a couple of mods that he can make to the printer, I have raised the hotend problem with him, so I am hoping that he can send me a new one, or the parts to fix this one. I could bodge this one, but as the thread is now shorter it will change the height of the hotend, and that will mess up the offset, I would rather wait and get new parts.
It was just pot luck that I printed two perfect parts, then went to print a third and the feed jammed.
Waiting to hear whether he can get spares. I think I found the source of the problem. The filament runs through the extruder assembly inside a hollow threaded rod. Cooling fins screw down the rod, and then the push fit union screws onto the end. The ptfe tubing is a push fit into the union.
From pics I have seen on the web, there is a section of the threaded rod that has the thread milled off. This end goes into the hotend of the extruder, and the break in the thread acts as a heat break to reduce the heat travelling back up the rod.
On mine the unthreaded section was at the top, and had snapped off inside the cooling fins. My guess is that the heat was travelling back up the rod, and into the union at the top, it was softening the PLA before it got down the tube. After a couple of prints it got hot enough to melt the PLA, and then when it finished printing, it solidified inside the union. I cut the union off and there was a lump stuck in there that was a pig to get out.
So now I need a new union and a new threaded section, or a new extruder assembly. I will have to sit and wait...fortunately it means that I can spend more time designing a few bits and not be rushed into printing parts.
Spoke to the vendor on the forum, and found someone who is connected to the Australian company that makes these hotends. The vendor has offered me parts, or return and replace, and the Ozzie guy has told me where I can get spares down under if I need them.
I am going with return and replace as I don't really want the hassle of taking the thing completely apart and reassembling it. The tolerances are quite critical and affect the quality of the printed output, so a new one would be much better.
There was no parts list with the printer, the Open Source industry tends to work on the basis of web links to find what you need to know. The RepRap forum is the main source of info. The printer itself is made up from off the shelf products that can be purchased anywhere, and 3D parts that can be downloaded and printed if anyone needs them. It's why things that are open source are so cheap, it's an excellent way of doing things and stops large corporates from making a fortune out of something that should cost so little.
May as well add my latest escapades to this thread, it may be useful to anyone thinking of venturing down this path.
As mentioned previously, the hotend that I originally had jammed solid with filament, and after dismantling it I found that the hollow threaded rod that runs up the middle of it was snapped. After a bit of dialogue with the vendor, I received a new hotend yesterday. I was now completely familiar with the installation and set up so did all of that and ran a couple of test prints. Made a couple of adjustments in the settings, and it then decides that it isn't going to extrude any more filament.
I tried running the temperature up, disabling the fan etc, but it wasn't having any of it.
Getting a bit jarred off with this game, so stripped it down (its only 5 pieces).
Sure enough, the filament had softened right through the hotend and into the bowden cable and then set rock solid. My guess is that if filament jams of slows down, then the laws of conductivity come into play, and that instead of hot liquid filament flowing out of the nozzle and being constantly pushed through by the filament feed mechanism, the filament stays in the hotend, gets hot, the heat travels back up the filament and softens it. At this point the feed is pushing on soft filament and so compresses it rather than pushing it through to the nozzle, the second it cools, it goes solid, hence the jam.
Jammed filament is the bugbear of 3D printers, I think the secret even on a perfectly set up system is to run it at as low a temperature as possible, PLA is 185 degrees, so start at that and raise the temp gradually until it flows freely, but no more. The less heat that is in the hotend, the less can travel through the conductivity. Well it makes sense to me anyhow??
Luckily this time nothing was broken. So now I had to get the filament out. The nozzle was easy, just heated it up and waited till it cleared.
The rod and bowden cable was next. The Bowden cable socket was a write off as they are push fit and one use only. Not a problem as these are only a couple of pounds on Ebay (they are just standard air hose fittings), so ordered two for good measure.
I then placed the rod and the attached cooling fins onto a pyrex plate and left it on the cooker hob. After a while the filament melted out, and running some brass wire up and down inside eventually cleared it all out. Once it was clear and had cooled down I pulled out the internal ptfe liner and pushed some filament through to check that it was travelling freely, and then found that halfway down the liner was crimped somehow on the inside, the filament would travel halfway and then require considerable force to push it right through. There was the problem.
So, even though this is a brand new hotend, I have ordered up a metre of ptfe tube and the bowden cable push fits so that I can get this working as God intended, and have spare material to fix it if it goes belly up again.
The annoying thing is that when it is running the printer is spot on, and the problem with the extruder is down to nothing more than someone at the factory not putting things together properly...twice? The vendor is hard work to discuss things with as English isn't his first language, if the repair doesn't work I am going to try one of the cheap Chinese replacements, they can't be any worse than this one. lol.
Printing at 67%, .4 nozzle so that is set up in the printer config, and the filament came from a 3D printer store that sells quality kit. It's kept in a sealed bag with a moisture absorber. I use Slicr. It all prints perfectly when it is running, so I know that everything is set up as it should be, but the first extruder had a broken rod running through the cooling fins, and this one has some sort of obstruction halfway down the ptfe liner in the rod. I am hoping that when I replace that the filament will moce freely down to the melt chamber and everything will work in the way that it was designed to. I noticed that just before the jam, the stepper motor on the filament feed kept jerking backwards, which is a sign that the filament is producing back pressure on the line.
The Alu hotends are quality items, same as the E3D, so once it is working properly it should do the job well. At least I have learnt how to take one apart and put it back together again. The interesting thing is that although the E3D costs an arm and a leg, the Alu hotend is only around £20, so replacements are never going to be expensive.
Most printers print well at around 20-30mm/s. I print at 60mms and pushed it up to 120mms before I started having problems.
Sometimes you can get a bad roll of filament when the diameter of the filament varies greatly. Run a length of filament through some calipers to see if there's any fat spots.
Interesting... I got curious when I read your comments so went back and checked all of my print settings. I tweaked a couple but as I can't test them I will have to wait. I have found a thread on a forum that relates to the print speed on the software I am using, and apparently it is measured in mm/min rather than mm/sec. I haven't yet found any details on what the % setting should be in order to obtain a particular speed in mm/sec, but will continue my quest.
I went and measured the '1.75mm' filament. It is a minimum of 2.00mm, and also seems to be oval, so >2.00mm across the other section. I am sending an email to the supplier as their ad stated 1.75 +/- 0.1.
I can set the printer config to 2.00mm, but the filament isn't what was advertised, and I have a 1kg roll of the stuff! My brain tells me that if the print head is expecting 1.75mm filament at 'x' mm/sec, but is having 2.00mm shoved down the hotend, it is going to clog the thing up at a rate of around 10% per mm/sec.
Many thanks for prompting me to start checking everything, it just goes to show!
