How do you choose whether to use a PEEK or PTFE barrier? Well, I asked the benefits of using PEEK over PTFE thermal insulating barriers in an extruder assembly and Nate True gave a fantastic summary:
PEEK is more rigid and won’t bow out and leak everywhere with ABS. It would be better for PLA except that PLA likes to stick to everything. So PTFE (being not sticky) is preferable for PLA. ABS is very slippery by comparison so PEEK is more than adequate for it.
…BBQ
I’m still rockin’ my black ABS coil, so I’ll probably have to add a PEEK barrier to my MakerBot wish list.1
ttp://cre.ations.net/blog
The bit about BBQ is a joke about the over-use of acronyms. [↩]
I’ve been fiddling with settings on my MakerBot for the last week or so trying to improve print quality. Skeinforge setting this, Skeinforge setting that. Up, down, left, right, set it to pi, increase the print temperature, decrease the raft radius, adjust the feedrate speed. Unfortunately, all I managed to do was decrease print quality. Over the last two days I noticed the filament was coming out fairly slowly and today I noticed I kept stripping the filament.
Plastic that had oozed onto the nut below the barrier
Plastic still stuck inside the barrel itself
A plastic plug inside the PTFE barrier and a slight bulge to the barrier
Plastic on the threads is not a huge deal, but not trial either – it mostly peeled off in spirals. Plastic on the nut is not a big deal – I pulled that off with some needle nose pliers. Plastic inside the barrel can be drilled out using my drill bit and rubber band trick.1
Plastic inside the PTFE barrier… well, now, that’s a different animal. I’ve succeeded once in rescuing my PTFE barrier from PLA oozing down the threads, but in that case there wasn’t a plastic plug inside the PTFE. The problem with a plastic plug inside the barrel is that I can’t really drill it out. If I try to drill it out from the top, I’ll probably still leave a bit of plastic where the barrier meets the barrel. If I try to drill from up from the bottom, I stand a good chance of ruining the part where the PTFE meets the barrel – creating a small gap where plastic can get stuck.
Thus, I think I will drill out the barrel and slap in a new PTFE barrier. Since I have this old (ruined?) one lying around, I have sliced off about a 2mm wafer to use as a washer on my next heater assembly. Using a small hacksaw blade did the trick – even if it left me with a relatively uneven slice.
I was concerned that after having PLA ooze through the threads that I would be forced to use my backup PTFE barrier. However, I’ve been pleasantly surprised to discover that I can print just fine with my reassembled unclogged extruder. I’ve been able to print several things without so much as a hiccup.
So be delicate with your PTFE even after plastic has oozed into the threads – you may just be able to use it if you can clear out the plastic from the threads.
Well, not really playing. But, I suppose not really “working” either. Here’s how my experiments in unclogging a clogged extruder barrel went:
You can see where there is some minor plastic residue left over from the PLA in PTFE insulator which oozed into the threads. I had used a precision screw driver to follow along the threads and chip out plastic.
PTFE insulator, mostly clean
Here’s the clogged barrel. I had chipped out plastic from the threads using the same precision screwdriver. You can see some of the scar marks from my brilliant idea to use a wrench on the smooth part of the barrel at one point. (FYI, that was sarcasm – don’t use a wrench on the barrel. It was, in fact, a bad idea). I was totally unable to remove the nozzle from the barrel.
Extruder barrel, clogged
This was my idea for the setup so that the flame/heat would not discolor everything. You can see where the nozzle has gotten a thin layer of black ABS fused to it. Again, you can also see the marks on the nozzle where I tried to use a wrench. And, again, not a good idea. All I managed to do was just scar it up.
Extruder barrel with nut partway on
This is similar to the setup I settled on for trying to unclog the barrel. I’m going to cut the suspense and let you know – this doesn’t work and you shouldn’t try it. This setup did not work for two very important reasons you can learn from. First, it was too low to the ground and the blow torch kept going out when I tilted it to get to the heater barrel. Second, it relied on kitchen tiles – which is a terrible terrible idea.
Kitchen tiles - good intentions, bad idea
Here’s the next part of the setup: blow torch, flint, wrench for picking up hot things, and fire extinguisher. Off camera right is a garden hose. Again, this setup relies on kitchen tiles – which will actually shatter when this kind of heat is applied. So don’t do it. Oh, and it turned out I did have a blow torch – but it was empty. :)
Setup - empty propane tank, bad kitchen tiles
This is a better setup – with a brand new propane tank – but still a terrible idea with kitchen tiles.
Setup - FULL propane tank, bad kitchen tiles
This was a good setup. Friend nearby with a garden hose and fire extinguisher, no nut on the barrel so it sits in the washer and is easier for me to heat the entire barrel, suspended in air by a metal hook, held down by a big rock, high enough that I didn’t have to tilt the blow torch. Here you can see the scorched and shattered kitchen tile in the pile on the right.
GOOD setup with extruder barrel suspended in air by metal
Since I was in charge of the blow torch and my friend had the fire safety equipment I really only pictures of stuff as it was in a relatively cool state. This means I did not get a picture of the barrel as I was heating it – I had gotten it glowing red hot which was pretty nifty. I also missed out on getting a picture of flame spewing from the nozzle as the ABS inside ignited. It was like a mini flame thrower tossing out a thick black smoke.
I was expecting some of the ABS to leak out of the bottom – but the barrel was essentially clean. I could see all the way through the nozzle with no problem.
I’ve managed to clear out the PTFE insulator pretty well. I pulled the entire heater out of the extruder, turned up the heat a little, held the barrel lightly in plyers, and unscrewed the PTFE without a problem, and then turned the heat off. I then used a precision flathead screwdriver to follow the threads, popping/chipping the plastic out as I followed I went. However, I don’t know to what extent the threads are still intact. Since the PLA oozed into the threads, I have to think they’re messed up to some extent.
As for the barrel, I used a drill bit with the unsharp end wrapped in a rubber band. I rotated the bit using the rubber band as a grip to drill out the plastic. It actually worked really well for clearing out the barrel right to where I can see the barrel entering the nozzle. The inside is reasonably clean, but I still can’t put a filament into it freely.
I also had to take a precision screwdriver and follow along the threads on the barrel to chip out plastic. This went reasonably quickly. Once I was done the nut was able to screw on and off freely.
Now I’m left with a slightly discolored PTFE and a mostly clean barrel. I’ve got a spare PTFE insulator, but I’m hoping this one is salvageable. It still has threads and the barrel will screw in nicely.
Rick and Spacexula have suggested I use a torch to heat up the nozzle and let the plastic burn/fall out. But, this is a trick for another day with proper safety equipment.
Oh, and before I forget, Spacexula suggested keeping a ruined PTFE barrier to slice into insulating washers. I’m hoping I might be able to re-use the PTFE insulator, but this is certainly my backup plan.
