sounds like the MK5 hot end will have a seamless pathway all the way to the melter... even if there's still a PTFE insulator - which I'm not sure I get yet... WHY use PTFE - WOOD is cheap-and hard-dimensionally stable - and unless I'm mistaken, won't burn at the temps we're working at.
Though, please, someone correct me if I'm wrong here.
So there's the PTFE tubing that guides the filament all the way down to the hot end from the supply and filament driver - cool, but hey - what about reel changing? do we have to un-thread the entire length? hmmm... sounds not so great. do they hope we'll spend $100 each for a spindle + another $100 for each filament driver + another $50 for a controller for each color? or are we expected to push 2 feet of filament through the tubing each time we want to change colors.
if you aren't familiar with the mk5 concept - or the bowden extruder, it's basically pushing the filament driver away from the nozzle - which is cool in some ways. It makes the nozzle end very light-weight, and smaller by a lot. however it's a long travel from the driver to the hot end. so there's compression of the filament (although I dont' think that's a huge problem) but material changes is more problematic.
I'm thinking it'd be better to have the filament driver as close to the hot end as possible - and just insulate it better... again - I SAY use wood, not PTFE. It's serving me well, and I've NEVER had even a hit of burning wood smell... so ***DISCLAIMER*** I personally have never noticed any risk of fire hazzard from the wood, and it doesn't expand or fail like the PTFE - BUT!!! I also have no possibility of leaking plastic into the wood threads or anything - there are no seams in my set-up. I have a thin (1/32" wall) PTFE tubing that runs the length of my wood insulator and down into my 5/16" - 18tpi hollow tubing that has a 3/16" bore - which fits this 3/16" OD, 1/8" ID PTFE tube like a glove... in fact I had to shave the tubing down on the outside with a perpendicular exacto blade (like how you'd scrap the top of your nail to check the sharpness of a freshly sharpened knife)
anyway - .... I really need to post a drawing of my hot end. picture = 1000 words, and somehow my 1000 words is only worth 3 pictures of around 25% clarity.
can't wait to see the final mock-ups of the MBI Heater Barrel... Although I think there are still issues to solve, and I think they are not 100% goal oriented on ideal for end user, but they are trying to run a business... so it has to be cost effective (for them) to sell this.... so some of their decisions make more sense when you look at it from a business point of view - and I can in NO WAY fault them for that. Doesn't mean that I think it's pointless to design my own hot end either. :)
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I used wood as an insulator retainer for my RepStrap, and I got smoke everytime I fired the heater up.
ReplyDeleteWere you using the standard 6mm OD heater barrel? What kind of wood?
ReplyDeleteI wonder if it's because I've got the large diameter barrel? (5/16 OD) distributing the heat over more surface area... i.e. more metal surface area in contact with more wood surface area = less energy transfer per in^2, or mm^2 :). I think that "wood" make sense :D.
Again, not only do I not get any smoke, even at 240° C, but unscrewing the heater barrel shows no scorching of the wood at all.
Another note, I am not simply replacing the PTFE insulator with wood, that wouldn't work, because the ABS would STILL ooze around the barrel and into the threads... I think.
It's not hardwood, but inexpensive whittling (pine, I think, definitely not bass wood). I threaded it 1.5" inside, and have a 5" long heater barrel. The heater barrel is insulated all the way up to the wood. and the pathway the abs takes is inside PTFE tubing, so no seam for the ABS to ooze out between.
Thanks for your comment. It does help in considering why mine is working and why others may have given up on wood.