Extruder Temp Drops upon starting Print

[wesd08]

I've been enjoying my Rostock Max v2 for several months now. Recently, I've noticed that when I start a print, the Extruder temp drops off completely.

Preheat works fine, and the hot end reaches a stable preheat temperature before printing. Any ideas about how to troubleshoot this issue? Would love to start printing again.

Thanks in advance!

[Tincho85]

Does the layer fan turns on when the print begins?

[JFettig]

What are your pid values?

[Eaglezsoar]

You may try to wrap your heating block with self fusing silicon tape to act as insulation for the block.

[JFettig]

silicone tape only bandaids the problem, when the electrical connections are good and PID is right, it shouldn't have any issues with getting to temp. Your I and D values should be less than 1, usually .1-.2

[Eaglezsoar]

silicone tape only bandaids the problem, when the electrical connections are good and PID is right, it shouldn't have any issues with getting to temp. Your I and D values should be less than 1, usually .1-.2

I suggested the tape in case a fan is blowing on or near the heat block.

[SirLinhart]

I was pushing 60 mm/s through a .7 nozzle at 100% fan and the temp dropped so low that it failed to extrude PLA (140ish). Didn't have too much of an issue with smaller nozzles (still had temp drops, but none extreme enough to cause a print to fail). Swapped to a 40 watt heater core, a screw in thermister (just because I could) and wrapped it up in silicone tape. Now it heats up much faster and holds temp with a few degrees. Not sure if this is actually needed, but I found it helped.

[Xenocrates]

It sounds like you didn't have enough thermal energy going into the system. The larger the nozzle and speed, the larger the amount of filament being extruded per second. If you're using a larger nozzle, the speed should lower somewhat. This lets the heater actually warm all the filament. Now that you increased the power available, you can print at that speed. To print at those speeds with that nozzle size, you likely did need the additional power and the reduced loss from the tape.

[rehabmax]

Temperature drops after printing starts are usually related to the layer fans blowing over the extruder nozzle. If you are using PLA the fan or fans come on. If the temperature is dropping too much and the filament is not melting properly i would adjust the percentage of the layer fan output. In Matter Control you can go to the PLA settings and navigate to the fan section. Usually it is set to 100% for the first few layers and then it drops to 60 %.

Another issue that i ran into was that I could not get the hot end nozzle to reach the target extruder temperature. For ABS at 228º C it would get to 225º C and not go any higher. Putting my finger in the peak fan to stop it (suggested by customer support) let the temperature rise to trigger the start. After doing this a few times I concluded I did not want to have to start my prints this way. i realized the all the Kapton tape I had wrapped around the hot end had pretty much all burned off. i removed the whole assembly and rewrapped the end with new Kapton. It acts to keep the heat in the hot end and also as a barrier from the peak fan. Now all is working well.

i suggest keeping a close check of the nozzle and make sure all the Kapton tape is in good shape. if not, remove the assembly and add more layers of Kapton.

[Eaglezsoar]

The Kapton tape is okay but I still recommend the self fusing silicone tape, it acts as a much better insulator.

[rehabmax]

I had a similar problem. I finally realized the Kapton tape I had placed around the nozzle pace had either burned off or mysteriously disappeared. By adding more tape it acts as an insulator and also blocks the blower fan from cooling the print head nozzle too much.

You can also adjust the layer fan output to reduce from 100% down to 60-70% if using cooling for ABS.

This could be the problem and it is easily remedied. I was getting frustrated seeing the temperature drop from 220ºC to 185ºC with ABS printing. Once i added more Kapton tape and adjusted the fan output everything began working well. Now I keep a close watch on the Kapton tape.

[Eaglezsoar]

I had a similar problem. I finally realized the Kapton tape I had placed around the nozzle pace had either burned off or mysteriously disappeared. By adding more tape it acts as an insulator and also blocks the blower fan from cooling the print head nozzle too much.

You can also adjust the layer fan output to reduce from 100% down to 60-70% if using cooling for ABS.

This could be the problem and it is easily remedied. I was getting frustrated seeing the temperature drop from 220ºC to 185ºC with ABS printing. Once i added more Kapton tape and adjusted the fan output everything began working well. Now I keep a close watch on the Kapton tape.

This self fusing silicon tape works really well for insulating the heat blocks also. It can be found here: http://www.amazon.com/RESCUE-Self-Fusin ... icone+tape" onclick="window.open(this.href);return false;

[U.S. Water Rockets]

One thought:
Part of the problem is that the PID is tuned with the extruder in a static configuration, and when you print, it is actively being cooled by the plastic that you are pushing out the nozzle, taking heat away. This can cause the nozzle to dip a little in temperature. If you're on the hairy edge of where the plastic flows well and doesn't flow well, the small change can cause cruddy prints. Bumping the temperature of the extruder a bit can help.

Another thought:
I've seen issues on an expensive printer where the prints would be fine but when they reached a detailed area with a lot of retracts, the quality would go down the tubes. Looking at the extruder temperature profile, I could see the area with the retracts was dropping quite a bit. I changed the retract to something much smaller (I think I went from 4mm to 1mm) cleared the problem right up. I can only speculate the large retracts were pulling heat out of the nozzle.

[stevewm]

I started to have this problem after a few months as well. Turned out to be one of the heating resistors going south.

Removed both resistors, installed a single 40 watt heater cartridge, and haven't looked back. The cartridge heats up considerably faster than the resistors ever did and maintains temperature much better. I also found switching from PID to dead-time heater control (http://www.repetier.com/dead-time-control/" onclick="window.open(this.href);return false;) to give much better stability. With PID it would take some time to stabilize on the target, and any disturbance would send it oscillating around the target again. With dead-time it recovers much faster and stays at the target temperature more consistently, in my opinion anyways.

[Johncoffee]

Is turning the extruder fan completely off here bad? e.g. does the PEEK isolator above the extruder gets damaged by doing this? I remember printing the fan shrouds in ABS also without the extruder cooling fan.

Or another question : how can I reduce the extruder fan speed, e.g. to from 100% down to 60%? I can change the layer cooling fan speed, but not the extruder fan speed..

Thanks for any reply!

*John*

[Xenocrates]

I don't believe it will damage the PEEK isolator, but it will allow more heat to creep upwards, which will increase drooling of the nozzle, and also likely increase the possibility of jams. I would prefer to wrap the barrel of the hotend in Kapton or silicone tape to decrease the effects of the air on it.

As far as changing the fan speed, you can alter the firmware written to the board to change it, or add a potentiometer, resistor, or other series load (Not parallel) to decrease the power delivered to the fan.

[Johncoffee]

I don't believe it will damage the PEEK isolator, but it will allow more heat to creep upwards, which will increase drooling of the nozzle, and also likely increase the possibility of jams. I would prefer to wrap the barrel of the hotend in Kapton or silicone tape to decrease the effects of the air on it.

As far as changing the fan speed, you can alter the firmware written to the board to change it, or add a potentiometer, resistor, or other series load (Not parallel) to decrease the power delivered to the fan.

Thanks for your comment Xenocrates. I didn't think about the jamming. Ok - I'll apply some more Kapton around it to get a better isolation.

[Xenocrates]

You're entirely welcome john. Let me know how it goes.