Print will not start because of temperature fluxuations

While the print head temp reaches 230 c then varies sinusoidaly plus minus 4 degrees around 230 . Print will not start because (guessing) because it never reaches a steady 230c. Not sure if this how to address this ..

I don't know what printer nor firmware nor control board you are using but I do know a little about the gcode.

With my system, the print head temp is set and controlled by 'M104 S200' which tells it to heat to 200C, or 'M109 S200' which tells it to heat to 200 and hold until that temp is reached before it continues. Similarly M140 and M190 are used to control the bed temps. The firmware I use (Repetier) knows the meaning of those commands and acts accordingly.

From your description it seems as if the firmware does not resume processing once the set temperature has been reached. Thus my suggestion is to look at the firmware or the control board for this issue.

You'll need to perform a PID tune to keep the temperature stable.

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The Marlin firmware installed in your printer contains default PID values for the hotend and bed. The M303 can be used to determine specific values for your printer. You would use these values by inserting M301 and/or M304 commands into the start gcode for your printer. New values can be saved with an M500.

More information at G-code - RepRap including this link, PID Tuning - RepRap.