Extruder heating issues - is it just me?

Don_Sadlier · 2016-05-25T22:34:32.000Z

I have a CTC Giant. Cura is used to do the printing. I’m having an issue in that when the print starts it will do the heat up. As soon as it is to temperature the bed will lower (= nozzle raises) then the extruder begins moving into position to start the print. The problem is that the extruder temperature will immediately drop about 50 degrees then start climbing back up. Unfortunately that temperature is too low to melt the filament (I’ve been using PLA) so it begins with only going through the motions of printing until the temperature climbs back up. It may be about 3 layers in to the print before the trmperature is high enough to melt the filament.

I thought it may be a faulty extruder heater so it was tested. It is at 9.1 ohms with 18 volts which makes it about 36 watts. That seems close. The voltage was measured during operation to verify that it was getting the 18 volts.

It was also noticed via the LED on the control board that as soon as the temperature drops the board is giving it full power. Unfortunately before getting to the proper temperature it will begin modulating and never reach the setpoint. It looks like a PID setting is wrong but no idea of where it should be.

Is this problem unique to me or does everyone else experience it?

zx81 · 2016-05-26T11:38:16.000Z

You could try setting the bed temperature waiting till it heats up then heat the hotend. When they reach temperature start printing, you will want to remove the bed heat up gcode from your startup procedure… It’s the power supply big enough for the bed and hotend ?

Don_Sadlier · 2016-05-26T15:10:59.000Z

The power supply is handling the loads. It drops only about .1 volts from no load to heating the bed and extruder.

I’ll try heating the bed first.

Don_Sadlier · 2016-05-27T17:22:51.000Z

I found the problem. The manufacturer had grounded one lead of the thermocouple and, additionally, the electrical connection for it was loose. The temperature is now proper.

zx81 · 2016-05-27T18:02:07.000Z

glad you got it fixed!

Don_Sadlier · 2016-05-31T21:04:48.000Z

The measured temperature of the extruder ended up being about 40 degrees lower than what the machine was reading. I remembered the manufacturer of the thermocouple chip warning about stray offsets each time another junction is made, such as if the thermocouple wire connects to a terminal block. CTC had crimped horseshoe connectors on the thermocouple wire so those were cut off, the wire stripped, and a more direct connection made to the control board. That brought the thermocouple to a 20 degree difference. I suppose that if I remove the terminal block on the board and do a direct solder connection then the value will improve but I think I can work with this.