ebam
1
Have had a few prints recently with PLA that look like underextrusion and the only way to get a decent print is to wack up the extruder temperature to 240c!! ABS prints absolutely fine, no issues at 240c. Photo of pink PLA blocks - left is 240c, right is 230c. Grey PLA blocks range from 215c to 240c left to right. Could it be the filament? The grey and pink are both PLA as sniff tested and their full adherence to glass and glue would also confirm this. Have used both these spools of PLA before with success at 220c but now both refuse to work at this temperature. I recently had a blocked nozzle and wondered if I had damaged something however I have had good ABS prints since then. Any ideas what the issue could be? Confused.
Sounds like a clog. You want to try a method called the “cold pull”. This link explains:
If that doesn’t fix it then let me know.
-Jesse
Check out this site, I think you will see some familiar pictures.
https://www.simplify3d.com/support/print-quality-troubleshooting/
How long have you had this printer/how many prints.
This looks like a failed PTFE tube to me.
I agree on temp, seems way to hot for regular PLA. I can get good prints between 180-210 for Makergeeks PLA. 190 is a good temp with a 60 bed. On their Crystal PLA I have tested up to 230 and it prints nice but also does good at 190 on my machines.
Yeah i also would say this looks like a clogged extruder that may lead to partially underextrusion… printing PLA on 240° seems a lot to hot to me and leads to parts like you’ve shown us on your pictures. The layers can’t cool down enough and solidify before the next one will be applied. I’m printing PLA usually at 195° to 205° but of course this depends on your printer/hotend.
Simplify3D has a great guide with troubleshooting for the most common 3d-printing issues, it’s totally worth a read even if you don’t have issues at the moment with your printer. 
http://www.simplify3d.com/support/print-quality-troubleshooting/
(edit: haha, seems like @wirlybird had the same idea like me 
ebam
7
Ok so, it was recently cleaned out and prints ABS perfectly fine at regular ABS temperatures. I have printed the block in green ABS very nicely before and after the grey and pink PLA blocks. As for lower temperatures working better I understand the theory however the better quality has been on the higher temperature settings??!! ABS prints fine so I cannot see how it could be a blockage otherwise I would experience the same thing with the ABS??!!
ebam
8
Not quite sure I get how to do that on the CTC.
ebam
9
Pink PLA at 190c, 200c. Grey PLA 240c, Green ABS 240c
ebam
10
It’s done 213hrs and have had it about 6/7 weeks
Perry_1
11
Pull your nozzle off and pull your PTFE tube out. I think you will see it is deformed.
If you have done a bit of printing at 240, it will eventually degrade. PTFE starts to break down at 230.
Just take a look.
ebam
12
Can anyone explain why ABS is printing fine and PLA is not? If it is a deformed PTFE tube then why does ABS get through and the PLA not? In the case of “pull your nozzle off” is there a way that this can be done without removing the printhead from the bars, taking off the fans and heatsink, removing the thermocouple from the heatblock so it doesn’t get broken to just get the nozzle off on a CTC??
Perry_1
13
Heat your extruder.
While holding the extruder still, perhaps with a pair of pliers and a towel, use a small wrench to take the nozzle off.
Then, with a pair of needlenose pliers, you should be able to pull the ptfe tube.
If it is black or twisted, it needs replaced.
Look at the pictures toward the end of this page Talk Manufacturing | Hubs
I am not saying for sure this is it, but take a look.
ABS liquifies better than PLA, and stays liquid longer, as such, can make it through the tube, but PLA cannot.
Likewise, the ABS may be liquifying up the tube more than the pla, or less than the pla…
