Hotend Temp off by several degrees

[Bongoboy23]

Quick question.
(Rostock MAX V2)

I noticed that my hotend only gets to the set temperature for the very first part of a print (~1-3min), then is steadily several degrees below the set temperature for the rest of the print. Currently to get it to 215, have to set temperature to 220. If I set it to 215, its at around 210. Bed is set to 60C.

Is this because:
PID settings off
Heating elements not quite strong enough
Power supply cant quite manage both hotend and bed together
RAMBO board cant quite manage both hotend and bed together

If it helps I did have at one point have a strip of LEDs attached to the 12V supply from the board and noticed as the bed+hotend was on they would start flickering, like the power supply couldn't maintain a steady 12V with everything on. (disconnected atm)

I have a 600W power supply I could use, but just want to see if anyone else has encountered this issue also.

[bubbasnow]

what speeds are you printing out? if you slow it down a bit does it keep temp better?

[Bongoboy23]

Only printing at about 40mm/s. Considering the last print I had could print at 100mm/s with only 1C variance (According to the thermistor of course), I would really hope that 40mm/s isn't pull that much heat.

(I did order an extra hotend and 12V 40W heaters,5mm O.D., mostly cause I want to see how it does.)

[geneb]

Does your first layer temperature match your following layer temps? (this is a Slic3r setting)

g.

[JohnStack]

Can you look at how your leads are screwed into the board? Both the power and the hot end circuits.

What seems like EONS ago, my power leads were loosening up. I ended up using some thread lock.

(and yes, don't hang anything off of circuits that have to do with heat...)

[Bongoboy23]

Yes my first layer temp matches my following layers. (Had a Replicator 1, used Slic3r for that too)

Yes the leads are screwed into the connector tightly, I just assembled it not a week ago and I double checked now.

Also the LEDs were attached directly to the 12V in from the power supply, so it shouldnt matter that the circuit is for heat, if the power supply is powerful enough to maintain a constant 12V and the wires are big enough/short enough to hand the current without a significant voltage drop.

I did notice that the rating for the Viotek supply is 22A on the 12V line, which comes to only ~260W total. I have a CX600M power supply, and the 12V line on that appears to be rated to 46A, which comes to ~550W. I also have a 360W pure 12V supply I could try out to see if it has any affect.

[Bongoboy23]

A new power supply did not solve the problem, but it did stop the lights from flickering. Really kind of clueless as to why it cant stay at the set temperature. If you turn the bed off, it jumps up to the right temp, but at the same time, its perfectly capable of reaching the set temperature while powering the bed when it first begins warming up (I.E. full power to hotend and bed).

[Bongoboy23]

I replaced the hotend with the E3D hotend, and it is now capable of maintaining the set temperature. This is no doubt due to the 40W heating element. I can see in Repetier-host that the average on time dropped from around 85-95% to ~40%.

[Eaglezsoar]

I replaced the hotend with the E3D hotend, and it is now capable of maintaining the set temperature. This is no doubt due to the 40W heating element. I can see in Repetier-host that the average on time dropped from around 85-95% to ~40%.

It looks like your previous problem is solved and that is what is important. Happy Printing!

[Barefoothurst]

ok my printer has done the same thing from day one. while printing in the lower temps (190-200) it was 5 deg off with the filament cooling fan on. I could adjust the profile to adjust for this. Now that i am trying to print Nylon at 235c my hot end can reach that temp but after i start printing its running 8-10 deg low. If the layer cooling fan comes on the hot end is 20 deg low! making it virtually impossible to print nylon. I have rebuilt my hot end to make sure the Thermistor was properly installed, i also made sure that the heating resisters were coated with ultra copper rtv and properly installed. I have run the PID calibration 5 times for a larger sample then I averaged the results. I was trying to dial the PID in to compensate for this. I have only had the pinter for 1 month and I don't want to spend another $100 to replace the hot end with an ED3 or something more powerful. Am i doing something wrong? I wired it exactly as described in the manual.
Thanks
Jason

[Eaglezsoar]

ok my printer has done the same thing from day one. while printing in the lower temps (190-200) it was 5 deg off with the filament cooling fan on. I could adjust the profile to adjust for this. Now that i am trying to print Nylon at 235c my hot end can reach that temp but after i start printing its running 8-10 deg low. If the layer cooling fan comes on the hot end is 20 deg low! making it virtually impossible to print nylon. I have rebuilt my hot end to make sure the Thermistor was properly installed, i also made sure that the heating resisters were coated with ultra copper rtv and properly installed. I have run the PID calibration 5 times for a larger sample then I averaged the results. I was trying to dial the PID in to compensate for this. I have only had the pinter for 1 month and I don't want to spend another $100 to replace the hot end with an ED3 or something more powerful. Am i doing something wrong? I wired it exactly as described in the manual.
Thanks
Jason

I would try replacing the two resistors with one 40 watt cartridge heater.

[Barefoothurst]

does this seem to be the correct one?
Type: Cartridge Heater
Voltage: 12V
Power: 40W
Material: Stainless steel
Core: Ceramic
Diameter: approx. 6mm
Length: approx. 20mm
Lead Wire Length: approx. 100cm

[Eaglezsoar]

does this seem to be the correct one?
Type: Cartridge Heater
Voltage: 12V
Power: 40W
Material: Stainless steel
Core: Ceramic
Diameter: approx. 6mm
Length: approx. 20mm
Lead Wire Length: approx. 100cm

Yes, that will work.

[Barefoothurst]

Other than re-calibrating the PID, will i have to make any adjustments in the Firmware for the new heater? Or just wire it in?
Thanks for all the help by the way!

[Eaglezsoar]

Other than re-calibrating the PID, will i have to make any adjustments in the Firmware for the new heater? Or just wire it in?
Thanks for all the help by the way!

Just wire it in then recalibrate the Pid. That's all that's required. The fit may be a little tight if that is the case slowly enlarge the hole in the hotend with a drill bit just slightly larger.
If the fit is to loose then wrap it with a small amount of aluminum foil. Do not use any of the RTV, no matter what you have read on here, RTV is a heat insulator and does not conduct heat.

[Barefoothurst]

hmmm, thanks. Well then me coating the heating resistors in RTV is not helping the situation..

[Eaglezsoar]

hmmm, thanks. Well then me coating the heating resistors in rtf is not helping the situation..

Not in my opinion, but some think the RTV is heat conductive. They should look more closely at the specs.

[geneb]

If the layer cooling fan is dropping your hot end temperature by 20 degrees, then it's blowing on the hot end and not the part. Can you post a pic of the layer cooling fan you're using?

g.

[Barefoothurst]

Ok here is another symptom of the problem. When I run the PID calibration the hot end reaches full temp quickly and holds it well. I zeroed out my PID, ran the recalibration, and tried to print at 220. The hot end temp rises toward the set point then at 210 degrees you see the PID start cutting power to the hot end. The temp never reaches 220 so the print never starts. I have a setting wrong somewhere . My max temp is 240 so I don't think it's that. The Gcode was sliced by slic3er so I don't think its that. I am missing something. I think the problem lies with the PID.
As requested, here is the photo of my layer cooling fan.

[geneb]

"Zeroed out my PID" make no sense to me at all. Do you mean you populate the PID values in the EEPROM with the averages you obtain from the auto-pid output?

g.

[Barefoothurst]

Well to clarify, when I first set up the PID last month I calibrated it totally wrong. And the values I I put were way off. Since then I have re calibrated but I was concerned that the original values I entered may have skewed the results so I enter zero in the EPROM and then ran the recalibration. Honestly I'm grasping at straws right now because I don't know what the issue could be. I'm to the point that I may wipe the firmware and start from scratch. I don't know..

[geneb]

First off, don't set any of the PID values to zero - it won't work with a damn if you do. Second, do you follow the manual and put the averages of the P, I, and D values into the EEPROM after the auto tune is done?

g.

[Barefoothurst]

Yes I did. Exactly as in the manual.

[Barefoothurst]

My current PID settings are as follows:
Kp 14.89
Ki 1.06
Kd 50.63

Does this sound close to what other people are getting after calibration?

[Barefoothurst]

after careful observation of the temps and how much power was being applied to the hot end i have decided that i have a bad resistor. One was slightly cracked after i pulled it out and re-sealed it. I will install a 40w heater next week and that should resolve the problem.