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I have a Rostock Max v2 with standard hot end and everything was printing fine from the start. First print or 2 failed simply due to bed adhesion, (Prints came loose half way through). After switching to ABS slurry to hold everything down I was getting good prints. I even managed to print at .15 layer height for about 6.5 hours on one part and I was getting pretty good results. Alas, this has come to an end.

While printing a few small items the print came out all patchy and I noticed that the filament had been shaved down by the EZ Struder drive gear. I assumed I had a blockage and proceeded to remove and clean the nozzle. Upon re assembly I was still not getting any filament out and the end of the filament just above the nozzle had backed up and swollen so it was now stiff in the feed tube. Nextly I removed the whole hotend and cleaned and reassembled everything and tried again, still nothing.

I increased my temps to 245 and initially the print was coming out ok but after about 30 minutes or so it went patchy and the extruder again had failed to push the filament through. So I disassembled the heating resistors and thermistor and they all checked out with the multimeter. I wrapped the resistors in foil, for a more snug fit and reassembled everything nicely, only putting sealant on the ends to hold the resistors in place. Feeling rather pleased and very hopefully I tried again and sadly nothing.

The Extruder motor will happily feed filament and it takes a fair amount of force to stall in via the manual feed wheel which makes me think it is working well. If I feed filament down to the nozzle manually it takes quite a lot of force to push anything out the nozzle, even when I set the nozzle temp to 245C via Repetier Host.

I had the need to order a new thermistor from SeeMeCNC so I ordered 2 as I live in Ireland and the delivery times suck and both the installed one and the spare test to the same resistance roughly, (112kOhms - Installed, 113kOhms - Spare), the two resistors were reading about the 6.8ohms individually, my multimeter is cheap but it somewhat reliable, and about 3.8 ohms in parallel. I ran the PID autotune after reassembly each time and the values I now have are,

Kp: 24.246
Ki: 1.670
Kd: 88.33

The hotend appears to be too cold to extrude properly even at 245C, I am unsure as to whether it is a problem with the displayed temp, power of resistors or maybe an error in the controller. I am thinking that swapping the thermistor would rule out that but I feel since it tests the same as the spare at room temp that this may not be the fix. I have changed very little in the way of settings other than playing with fill and layer heights a little, is there anyway to push the nozzle temp beyond 245 to see if I can improve the extrusion? Any idea's on what to try next would be appreciated.

It sounds like your hot end is not heating enough. Can you check its temp independently with a thermocouple on your multimeter? That would be my first check, and a critical piece of knowledge to extrude properly. Worth every penny, even if you have to buy a new meter with thermocouple. If not that. Then maybe it's a bad resistor? Next would be connection to the Rambo output. Hopefully it's not that If it is resistor related? I would switch to a heater cartridge. You can find threads on that in this forum. Hope this at least helps with ideas to trouble shoot.

I followed the thermistor calibration guide and I got the hotend heating to pretty much exactly 225c measured by the thermistor and from a multimeter with a thermocouple. Feeling happy I put everything back together and then still no extrusion. Everything from the extruder to just before the nozzle seems to be allowing the filament through with ease but as soon as I try to extrude it fails to push anything through the nozzle.

I have check all the internals of the hotend but obviously the nozzle being so small is difficult to verify. With the hotend heated to 225c pushing filament manually through the hotend it binds once it gets to the top of the nozzle and any extra force causes heat soak back up the filament but still not extrusion. I have checked the hotend at various points with the thermocouple and just below the PEEK section the hotend only measured 175 when the rest was 220-225, above the PEEK section was only about 40-50 at the hottest. All of this makes me think everything I have tested is working quite well. I am going to soak the nozzle overnight in MEK and hopefully with this totally freed up I may be able to get back to printing.

nee4d wrote:I followed the thermistor calibration guide and I got the hotend heating to pretty much exactly 225c measured by the thermistor and from a multimeter with a thermocouple. Feeling happy I put everything back together and then still no extrusion. Everything from the extruder to just before the nozzle seems to be allowing the filament through with ease but as soon as I try to extrude it fails to push anything through the nozzle.

I have check all the internals of the hotend but obviously the nozzle being so small is difficult to verify. With the hotend heated to 225c pushing filament manually through the hotend it binds once it gets to the top of the nozzle and any extra force causes heat soak back up the filament but still not extrusion. I have checked the hotend at various points with the thermocouple and just below the PEEK section the hotend only measured 175 when the rest was 220-225, above the PEEK section was only about 40-50 at the hottest. All of this makes me think everything I have tested is working quite well. I am going to soak the nozzle overnight in MEK and hopefully with this totally freed up I may be able to get back to printing.

could be your little ptfe liner got put into a strange position

Can you see through the hole in the nozzle? Maybe a metal filing or some debris is clogging the nozzle?

I have failed to completly empty the nozzle so I have ordered a replacement. The PTFE Liner inside he hotend seems to be sitting nicely and I don't think the assembly is overtight or too loose either. Seems as though the very tip, last 3mm of the nozzle is blocked or maybe too cold. Can I use a small blow torch or gas soldering iron to heat the nozzle without permanently damaging it? I would like to heat it up in a small vice and see if I can get a few strands of wire back up the nozzle to clear out the last bit.

I've been away for work recently and I haven't had much time to troubleshoot but I did get a few minutes to heat it up and try it and what I noticed was that with my thermocouple touching the aluminium section and the nozzle(at the same time) I was getting a temp of 225 or so but it dropped steadily as I moved further down the nozzle. It was nearly as low as 210 on the very end. This might be just down to the contact area between the thermocouple tip and the nozzle being much smaller but I guess if it is accurate then I have poor conduction of the heat down to the nozzle tip and the ABS is going solid before extrusion and all the heat is simply soaking into the filament upstream of the nozzle and causing the widening of the filament in the PTFE liner. Is this maybe part of my problem? Do I need to insulate better or change my heat/PID settings? I am still using the stock resistors and thermistor but I do have a 12v 40w heater on order as a precaution. If I understand correctly the resistors I have are reaching the desired temp as measured by the thermistor but my nozzle is not getting to this temp possibly so a different heater won't necessarily fix this?

As always everybody's help and advice is appreciated, I.m off for a while after this week so I am hoping to get everything dialled in and enjoy printing again.