My hot end suddenly stops heating and decouples

Hi there.
i have this issue very rare..
prints suddenly 3/4 way (layer 186 for example) stop printing. the error message is.
11:44:41.918 : OpenGL version:3.1.0 - Build
11:44:41.918 : OpenGL extensions:GL_EXT_blend_minmax GL_EXT_blend_subtract GL_EXT_blend_color GL_EXT_abgr GL_EXT_texture3D GL_EXT_clip_volume_hint GL_EXT_compiled_vertex_array GL_SGIS_texture_edge_clamp GL_SGIS_generate_mipmap GL_EXT_draw_range_elements GL_SGIS_texture_lod GL_EXT_rescale_normal GL_EXT_packed_pixels GL_EXT_texture_edge_clamp GL_EXT_separate_specular_color GL_ARB_multitexture GL_EXT_texture_env_combine GL_EXT_bgra GL_EXT_blend_func_separate GL_EXT_secondary_color GL_EXT_fog_coord GL_EXT_texture_env_add GL_ARB_texture_cube_map GL_ARB_transpose_matrix GL_ARB_texture_env_add GL_IBM_texture_mirrored_repeat GL_EXT_multi_draw_arrays GL_NV_blend_square GL_ARB_texture_compression GL_3DFX_texture_compression_FXT1 GL_EXT_texture_filter_anisotropic GL_ARB_texture_border_clamp GL_ARB_point_parameters GL_ARB_texture_env_combine GL_ARB_texture_env_dot3 GL_ARB_texture_env_crossbar GL_EXT_texture_compression_s3tc GL_ARB_shadow GL_ARB_window_pos GL_EXT_shadow_funcs GL_EXT_stencil_wrap GL_ARB_vertex_program GL_EXT_texture_rectangle GL_ARB_fragment_program GL_EXT_stencil_two_side GL_ATI_separate_stencil GL_ARB_vertex_buffer_object GL_EXT_texture_lod_bias GL_ARB_occlusion_query GL_ARB_fragment_shader GL_ARB_shader_objects GL_ARB_shading_language_100 GL_ARB_texture_non_power_of_two GL_ARB_vertex_shader GL_NV_texgen_reflection GL_ARB_point_sprite GL_ARB_fragment_program_shadow GL_EXT_blend_equation_separate GL_ARB_depth_texture GL_ARB_texture_rectangle GL_ARB_draw_buffers GL_ARB_color_buffer_float GL_ARB_half_float_pixel GL_ARB_texture_float GL_ARB_pixel_buffer_object GL_EXT_framebuffer_object GL_ARB_draw_instanced GL_ARB_half_float_vertex GL_EXT_draw_buffers2 GL_WIN_swap_hint GL_EXT_texture_sRGB GL_ARB_multisample GL_EXT_packed_float GL_EXT_texture_shared_exponent GL_ARB_texture_rg GL_ARB_texture_compression_rgtc GL_NV_conditional_render GL_EXT_texture_swizzle GL_ARB_sync GL_ARB_framebuffer_sRGB GL_EXT_packed_depth_stencil GL_ARB_depth_buffer_float GL_EXT_transform_feedback GL_EXT_framebuffer_blit GL_EXT_framebuffer_multisample GL_ARB_framebuffer_object GL_EXT_texture_array GL_EXT_texture_integer GL_ARB_map_buffer_range GL_EXT_texture_snorm GL_INTEL_performance_queries GL_ARB_copy_buffer GL_ARB_sampler_objects GL_NV_primitive_restart GL_ARB_seamless_cube_map GL_ARB_uniform_buffer_object GL_ARB_depth_clamp GL_ARB_vertex_array_bgra GL_ARB_draw_elements_base_vertex GL_ARB_fragment_coord_conventions GL_EXT_gpu_program_parameters GL_ARB_compatibility GL_ARB_vertex_array_object 
11:44:41.918 : OpenGL renderer:Intel(R) HD Graphics Family
11:44:41.918 : Using fast VBOs for rendering is possible
11:44:48.657 : Printer reset detected - initalizing
11:44:48.673 : start
11:44:48.673 : Info:Autoleveling enabled
11:44:48.673 : Transformation matrix: 0.999991 0.000000 -0.004240 0.000007 0.999999 0.001718 0.004240 -0.001719 0.999989
11:44:54.273 : zDistortionCorrection:1
11:44:54.289 : Free RAM:976
11:44:54.289 : Autoretract:0
11:44:54.289 : X:0.00 Y:0.00 Z:0.000 E:0.0000
11:44:54.289 : SelectExtruder:0
11:44:54.305 : Printed filament:222.05m Printing time:2 days 21 hours 25 min
11:44:54.305 : PrinterMode:FFF
11:44:54.398 : X:0.00 Y:0.00 Z:0.000 E:0.0000
11:44:54.398 : DebugLevel:6
11:44:54.414 : SelectExtruder:0
11:44:54.414 : Begin file list
11:44:54.414 : End file list
11:44:54.414 : Info:Autoleveling disabled
11:44:54.960 : SelectExtruder:0
11:44:54.960 : X:0.00 Y:0.00 Z:480.200 E:0.0000
11:44:54.975 : Info:Autoleveling enabled
11:44:54.975 : DebugLevel:6
11:44:55.303 : SelectExtruder:0
12:01:00.788 : DebugLevel:14
12:01:00.794 : Error:One heater seems decoupled from thermistor - disabling all for safety!
12:01:00.797 : Error:Temp. raised to slow. Rise = -39.55 after 36042 ms
12:01:00.797 : Disabling all heaters due to detected sensor defect.
12:01:00.797 : DebugLevel:14

the termistor reads temp perfectly even after decouple i can see temp drop as normal..
after reset even if i leave just hot end on at 230 degrees without a job it stays perfect then suddenly heating cartridge goes off and decouples..

any ideas??

thanks gas!


  • What heat manager are you using? Looks like bang-bang which is the worst for an extruder. Better switch to PID and use M303 to calibrate the PID values (see repetier.ino file for params).

    What I see is at the end temp. drops and heater goes on full power. Despite being on it does not go up that time as it did the other times, so after some time you get decoupled since it cooled down with heaters off and then disabled also power. So it looks like a hardware defect that happens after a while. Might be heater cartridge not heating any more or mosfet not turning on power after some time. Try with a multimeter to see if outputs have power when you see the dropdown starts . Once the decoupled message comes heaters will be off of course so also no power. So timing is required to see which part is defect.
  • I also suffer from extruder decoupling and I have done pid autotune and duly entered all the figures.  I used Repetier firmware as it was recommended to me as simpler to configure,  I have only recently converted my printer to RAMPS 1.4 and as far as I know there are no problems with with anything else.  I am trying to achieve 240 degrees but tit would appear that 235 is as far as it will go. and the tep. display continues to fall even when the heater led is on.
  • If you do not get enough power to reach 240°C it will fail decoupled. Make sure pid drive max is 255 so it can use full power. If that is not enough and you see in host/server it is powering 100% then your extruder can not get that hot.
  • thanks, found rare cartridge fail....
    changed to PID control and new cratridge is all going super well , thanks
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