Thread: Ok, so whats wrong?
The Following User Says Thank You to Clive S For This Useful Post:
Ok, I warmed the head slowly towards melt point and pulled most of the filament out, it was indeed jammed solid by swelling in the head support bolt, it took considerable force to remove it.
The head is now clear but the jet is solid, could not even probe it when hot with 0.3mm hard steel wire, totally blocked. As it's likely buggered I am going to drill it through with a 0.3mm drill and try that. It could possibly be a bit of swarf in it?
I can see how the heat spread up the support bolt and melted the filament before it reached the hot-end, but what I cant see is how this head could ever work the way it is built. I have seen the same unit on eBay listed as PLA/ABS suitable but they are all 0.4mm, that seems to be the only difference?
Will need to find a way of thermally isolating the support tube I guess or at least a way of bleeding more heat off of it???
Is there a fan on the hot end?
Many designs actively cool the feed tube so that there is a rapid temperature transition between it and the hot end, this stops filament that is warm enough to easily deform but not hot enough to flow expanding under feed pressure and blocking the feed tube.
See http://reprap.org/wiki/RepRapPro_Men...t_end_assembly for an example of an actively cooled hot end.
Yes it has a fan, this is the head...
The hot end has a short gap between it and the support/cold end about 10mm, the cold end is about 15x10x45mm and supports the fan which blows into the feed cavity. This end does not get hot really, very easy to touch even after some time.
The major difference I can see is that it has no PTFE liner at all??
I got it working for part of one print and made this.
Ok, its not too pretty, the bottom 4 or 5 layers are missing as i was fiddling about trying to get the plastic flowing, once working it went ok, but 10 seconds after the print finished it was blocked again, turned it off and gave up as there is no point trying if it wont feed reliably.
I have asked the seller for a refund on the grounds that it does not work.
Seriously thinking about buying an RS-Ormerod printer kit now.
That's not bad for a first attempt!
My only experience with hot ends is the RepRapPro mendel one which has been good (no jams) but that's a bowden cable type (you're better with direct drive if possible).
Seems a shame to give in when so close but the Ormerod does look like a nice machine.
Thanks, I did just get it going again, release pressure, force material by hand very hard and flush through, tighten feed pressure and start print, again the first layers failed, then worked ok then it failed near the end.
Again, blocked solid.
This time i fitted a large thin washer between the hot and cold ends to dissipate heat from the stud tube, all that gets hot now is the last 5mm of tube before it enters the hot end and it still jams.
The only thing i haven't got is a PTFE liner, maybe that's all that's needed??
Just guessing of course.
It is annoying, but there again it is eBay junk once more, but I really dont want to start throwing more cash at this if the Ormerod is any good.
Do you have room for the PTFE - mine is just under 4mm diameter.
The Ormerod looks good but it depends how stiff the construction is - I couldn't find any proper reviews of it and the RepRapPro website is offline.
Hmm the stud looks a bit wimpy to fit a sleeve.
I've been looking at the ormerod for a few weeks now, the few vids showing it on YouTube seem to be pretty good, self replicating, the metal parts seem pretty standard stuff too. Had a chat with our son today and have agreed to go halves on one, should be here tomorrow.
Apart from the troubles with my trial setup, the base machine is destined to be a plasma cutter next week and once you start cutting steel, it gets messy very quickly, not good for 3d stuff. I was just mucking about with the the 3d while waiting the couple of weeks I had to for the plasma cutter to arrive :)
My extruder is a printed plastic unit, which feeds the filament through a PTFE spacer to the hot end. PTFE isn't the greatest material out as it does tend to deform slightly when hot and under pressure and I've had to drill out my spacer once or twice to stop jamming - it may be PTFE but if the 'ole up the middle ain't big enough, the filament won't get through no how! Out of interest, have you checked how consistent the diameter of your filament is? I understand that not all PLA is the same - some can vary somewhat in diameter.
Yes, I measured the PLA today while testing, it's supposed to be 1.75 but measures up at an average 1.69 over four points.
any chance of a picture of your head ?
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