Temperature Control Issue with heated bed

JulienGantner_SW · March 20, 2018, 12:21pm

Context:

I’m building a Delta 3D Printer (a variation of the Kossel design) with a genuine Smoothieboard x5. Basic motion works and the hotend heats as expected. I am currently working with my heated bed. The heated bed is a custom design. It’s basically an aluminum disc (310mm Diameter, 10mm thick) that gets heated by a repurposed heating element from an soomthing iron (2kW 230V AC controlled by an solid state relay). The Thermistor is mounted inside the aluminum plate like the “old” E3D V6 hotned-Thermistors.

Problem:
I configured the software according to the guide in the Wiki. My temperature readings of the Thermistor seem to be plausible (my hand tells me they are at least in the correct ball park). Analog to the hotend i tried the PID autotunig procedure with the bed (M303 E1 S65). The temperature is rising but really slowly (from 22°C to 38°C in about 6 hours).
I do have the luxory to see when the heater is turned on (there is a indicator-light directly connected to the 230V AC side of the heating element). It flashes for a very short time and is off most of the time. I’ve connected the heater to various pins now to check if it relates to a special property of the pin (like pwm capabilities). I did try the Bang-Bang heater algorithm as well but it yielded the same results. I also tried to enter the Kp, Ki and Kd values directly and don’t use autotuning because i suspected that the thermal mass of the aluminum plate and the power of the heater may be to special for the autotuning to work. Nothing resolved the issue.

Any suggestions are welcome.

my configuration right now:

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# Smoothieboard configuration file, see link # NOTE Lines must not exceed 132 characters, and '#' characters mean what follows is ignored ## Robot module configurations : general handling of movement G-codes and slicing into moves Basic motion configuration default_feed_rate 4000 # Default speed (mm/minute) for G1/G2/G3 moves default_seek_rate 4000 # Default speed (mm/minute) for G0 moves mm_per_arc_segment 0.0 # Fixed length for line segments that divide arcs, 0 to disable #mm_per_line_segment 5 # Cut lines into segments this size mm_max_arc_error 0.01 # The maximum error for line segments that divide arcs 0 to disable # note it is invalid for both the above be 0 # if both are used, will use largest segment length based on radius delta_segments_per_second 100 # For deltas only, number of segments per second, set to 0 to disable # and use mm_per_line_segment Arm solution configuration : Cartesian robot. Translates mm positions into stepper positions See link alpha_steps_per_mm 160 # Steps per mm for alpha ( X ) stepper and tower beta_steps_per_mm 160 # Steps per mm for beta ( Y ) stepper and tower gamma_steps_per_mm 160 # Steps per mm for gamma ( Z ) stepper and tower Delta configuration See link arm_solution linear_delta # Selects the linear delta arm solution arm_length 340.0 # This is the length of an arm from hinge to hinge arm_radius 172.5 # This is the horizontal distance from hinge to hinge when the effector is centered Planner module configuration : Look-ahead and acceleration configuration See acceleration 3000 # Acceleration in mm/second/second. #z_acceleration 500 # Acceleration for Z only moves in mm/s^2, 0 uses acceleration which is the default. DO NOT SET ON A DELTA junction_deviation 0.05 # See #z_junction_deviation 0.0 # For Z only moves, -1 uses junction_deviation, zero disables junction_deviation on z moves DO NOT SET ON A DELTA Cartesian axis speed limits x_axis_max_speed 30000 # Maximum speed in mm/min y_axis_max_speed 30000 # Maximum speed in mm/min z_axis_max_speed 30000 # Maximum speed in mm/min Stepper module configuration Pins are defined as ports, and pin numbers, appending “!” to the number will invert a pin See alpha_step_pin 2.0 # Pin for alpha stepper step signal alpha_dir_pin 0.5! # Pin for alpha stepper direction, add ‘!’ to reverse direction alpha_en_pin 0.4 # Pin for alpha enable pin alpha_current 1.0 # X stepper motor current alpha_max_rate 30000.0 # Maximum rate in mm/min beta_step_pin 2.1 # Pin for beta stepper step signal beta_dir_pin 0.11! # Pin for beta stepper direction, add ‘!’ to reverse direction beta_en_pin 0.10 # Pin for beta enable beta_current 1.0 # Y stepper motor current beta_max_rate 30000.0 # Maxmimum rate in mm/min gamma_step_pin 2.2 # Pin for gamma stepper step signal gamma_dir_pin 0.20! # Pin for gamma stepper direction, add ‘!’ to reverse direction gamma_en_pin 0.19 # Pin for gamma enable gamma_current 1.0 # Z stepper motor current gamma_max_rate 30000.0 # Maximum rate in mm/min Extruder module configuration See extruder.hotend.enable true # Whether to activate the extruder module at all. All configuration is ignored if false extruder.hotend.steps_per_mm 140 # Steps per mm for extruder stepper extruder.hotend.default_feed_rate 600 # Default rate ( mm/minute ) for moves where only the extruder moves extruder.hotend.acceleration 500 # Acceleration for the stepper motor mm/sec� extruder.hotend.max_speed 50 # Maximum speed in mm/s extruder.hotend.step_pin 2.3 # Pin for extruder step signal extruder.hotend.dir_pin 0.22 # Pin for extruder dir signal ( add ‘!’ to reverse direction ) extruder.hotend.en_pin 0.21 # Pin for extruder enable signal Extruder offset extruder.hotend.x_offset 0 # X offset from origin in mm extruder.hotend.y_offset 0 # Y offset from origin in mm extruder.hotend.z_offset 0 # Z offset from origin in mm Firmware retract settings when using G10/G11, these are the defaults if not defined, must be defined for each extruder if not using the defaults extruder.hotend.retract_length 3 # Retract length in mm extruder.hotend.retract_feedrate 45 # Retract feedrate in mm/sec extruder.hotend.retract_recover_length 0 # Additional length for recover extruder.hotend.retract_recover_feedrate 8 # Recover feedrate in mm/sec (should be less than retract feedrate) extruder.hotend.retract_zlift_length 0 # Z-lift on retract in mm, 0 disables extruder.hotend.retract_zlift_feedrate 6000 # Z-lift feedrate in mm/min (Note mm/min NOT mm/sec) delta_current 1.5 # First extruder stepper motor current Second extruder module configuration extruder.hotend2.enable true # Whether to activate the extruder module at all. All configuration is ignored if false extruder.hotend2.steps_per_mm 140 # Steps per mm for extruder stepper extruder.hotend2.default_feed_rate 600 # Default rate ( mm/minute ) for moves where only the extruder moves extruder.hotend2.acceleration 500 # Acceleration for the stepper motor, as of 0.6, arbitrary ratio extruder.hotend2.max_speed 50 # mm/s extruder.hotend2.step_pin 2.8 # Pin for extruder step signal extruder.hotend2.dir_pin 2.13 # Pin for extruder dir signal ( add ‘!’ to reverse direction ) extruder.hotend2.en_pin 4.29 # Pin for extruder enable signal extruder.hotend2.x_offset 0 # x offset from origin in mm extruder.hotend2.y_offset 25.0 # y offset from origin in mm extruder.hotend2.z_offset 0 # z offset from origin in mm #epsilon_current 1.5 # Second extruder stepper motor current Laser module configuration See laser_module_enable false # Whether to activate the laser module at all laser_module_pwm_pin 2.5 # This pin will be PWMed to control the laser. # Only pins 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 1.18, 1.20, 1.21, 1.23, 1.24, 1.26, 3.25 and 3.26 # can be used since laser requires hardware PWM, see link Temperature control configuration See First hotend configuration temperature_control.hotend.enable true # Whether to activate this ( “hotend” ) module at all. temperature_control.hotend.thermistor_pin 0.23 # Pin for the thermistor to read temperature_control.hotend.heater_pin 1.23 # Pin that controls the heater, set to nc if a readonly thermistor is being defined temperature_control.hotend.thermistor Semitec # See #temperature_control.hotend.beta 4066 # Or set the beta value temperature_control.hotend.set_m_code 104 # M-code to set the temperature for this module temperature_control.hotend.set_and_wait_m_code 109 # M-code to set-and-wait for this module temperature_control.hotend.designator T # Designator letter for this module temperature_control.hotend.max_temp 300 # Set maximum temperature - Will prevent heating above 300 by default #temperature_control.hotend.min_temp 0 # Set minimum temperature - Will prevent heating below if set Safety control is enabled by default and can be overidden here, the values show the defaults See #temperature_control.hotend.runaway_heating_timeout 900 # How long it can take to heat up, max is 2040 seconds. #temperature_control.hotend.runaway_cooling_timeout 0 # How long it can take to cool down if temp is set lower, max is 2040 seconds #temperature_control.hotend.runaway_range 20 # How far from the set temperature it can wander, max setting is 63�C PID configuration See temperature_control.hotend.p_factor 99.9 # P ( proportional ) factor temperature_control.hotend.i_factor 9.080 # I ( integral ) factor temperature_control.hotend.d_factor 275 # D ( derivative ) factor heated bed temperature_control.bed.enable true # Whether to activate this ( “hotend” ) module at all. temperature_control.bed.thermistor_pin 0.24 # Pin for the thermistor to read temperature_control.bed.heater_pin 2.6! # Pin that controls the heater temperature_control.bed.thermistor Honeywell100K # See link temperature_control.bed.pwm_frequency 20 # PWM Frequency set to a low value for the ssr #temperature_control.bed.beta 3974 # Or set the beta value temperature_control.bed.set_m_code 140 # M-code to set the temperature for this module temperature_control.bed.set_and_wait_m_code 190 # M-code to set-and-wait for this module temperature_control.bed.designator B # Designator letter for this module Bang-bang ( simplified ) control See temperature_control.bed.bang_bang true # Set to true to use bang bang control rather than PID temperature_control.bed.hysteresis 2.0 # Set to the temperature in degrees C to use as hysteresis #temperature_control.bed.p_factor 14 # P ( proportional ) factor #temperature_control.bed.i_factor 0.09 # I ( integral ) factor #temperature_control.bed.d_factor 25 # D ( derivative ) factor Switch modules See Switch module for fan control switch.fan.enable true # Enable this module switch.fan.input_on_command M106 # Command that will turn this switch on switch.fan.input_off_command M107 # Command that will turn this switch off switch.fan.output_pin 2.6 # Pin this module controls switch.fan.output_type pwm # PWM output settable with S parameter in the input_on_comand #switch.fan.max_pwm 255 # Set max pwm for the pin default is 255 switch.hotend_fan.enable true # Enable this module switch.hotend_fan.input_on_command M42 # Command that will turn this switch on switch.hotend_fan.input_off_command M43 # Command that will turn this switch off switch.hotend_fan.output_pin 1.22 # Pin this module controls switch.hotend_fan.output_type digital # Digital means this is just an on or off pin Temperatureswitch See Automatically toggle a switch at a specified temperature. Different ones of these may be defined to monitor different temperatures and switch different swithxes Useful to turn on a fan or water pump to cool the hotend temperatureswitch.hotend.enable true # temperatureswitch.hotend.designator T # first character of the temperature control designator to use as the temperature sensor to monitor temperatureswitch.hotend.switch hotend_fan # select which switch to use, matches the name of the defined switch temperatureswitch.hotend.threshold_temp 45.0 # temperature to turn on (if rising) or off the switch temperatureswitch.hotend.heatup_poll 15 # poll heatup at 15 sec intervals temperatureswitch.hotend.cooldown_poll 60 # poll cooldown at 60 sec intervals Endstops See endstops_enable true # The endstop module is enabled by default and can be disabled here delta_homing true # Forces all three axis to home a the same time regardless of what is specified in G28 alpha_min_endstop nc # Pin to read min endstop, add a ! to invert if endstop is NO connected to ground alpha_max_endstop 1.25^ # Pin to read max endstop, uncomment this and comment the above if using max endstops alpha_homing_direction home_to_max # Or set to home_to_max and set alpha_max and uncomment the alpha_max_endstop alpha_max 0 # This gets loaded as the current position after homing when home_to_max is set beta_min_endstop nc # Pin to read min endstop, add a ! to invert if endstop is NO connected to ground beta_max_endstop 1.27^ # Pin to read max endstop, uncomment this and comment the above if using max endstops beta_homing_direction home_to_max # Or set to home_to_max and set alpha_max and uncomment the alpha_max_endstop beta_max 0 # This gets loaded as the current position after homing when home_to_max is set gamma_min_endstop nc # Pin to read min endstop, add a ! to invert if endstop is NO connected to ground gamma_max_endstop 1.29^ # Pin to read max endstop, uncomment this and comment the above if using max endstops gamma_homing_direction home_to_max # Or set to home_to_max and set alpha_max and uncomment the alpha_max_endstop gamma_max 249 # This gets loaded as the current position after homing when home_to_max is set alpha_max_travel 600 # Max travel in mm for alpha/X axis when homing beta_max_travel 600 # Max travel in mm for beta/Y axis when homing gamma_max_travel 600 # Max travel in mm for gamma/Z axis when homing Endstops home at their fast feedrate first, then once the endstop is found they home again at their slow feedrate for accuracy alpha_fast_homing_rate_mm_s 100 # Alpha tower fast homing feedrate in mm/second alpha_slow_homing_rate_mm_s 20 # Alpha tower slow homing feedrate in mm/second beta_fast_homing_rate_mm_s 100 # Beta tower fast homing feedrate in mm/second beta_slow_homing_rate_mm_s 20 # Beta tower slow homing feedrate in mm/second gamma_fast_homing_rate_mm_s 100 # Gamma tower fast homing feedrate in mm/second gamma_slow_homing_rate_mm_s 20 # Gamma tower slow homing feedrate in mm/second alpha_homing_retract_mm 5 # Distance to retract from the endstop after it is hit for alpha/X beta_homing_retract_mm 5 # Distance to retract from the endstop after it is hit for beta/Y gamma_homing_retract_mm 5 # Distance to retract from the endstop after it is hit for gamma/Z Endstop debouncing options #endstop_debounce_count 100 # Uncomment if you get noise on your endstops, default is 100 #endstop_debounce_ms 1 # Uncomment if you get noise on your endstops, default is 1 millisecond debounce Endstop trim options alpha_trim 0 # Software trim for alpha stepper endstop (in mm) beta_trim 0 # Software trim for beta stepper endstop (in mm) gamma_trim 0 # Software trim for gamma stepper endstop (in mm) End of endstop config Delete the above endstop section and uncomment next line and copy and edit Snippets/abc-endstop.config file to enable endstops for ABC axis #include abc-endstop.config Z-probe See zprobe.enable true # Set to true to enable a zprobe zprobe.probe_pin 1.28^ # Pin probe is attached to, if NC remove the ! zprobe.slow_feedrate 5 # Mm/sec probe feed rate #zprobe.debounce_count 100 # Set if noisy zprobe.fast_feedrate 120 # Move feedrate mm/sec zprobe.probe_height 2 # How much above bed to start probe #gamma_min_endstop nc # Normally 1.28. Change to nc to prevent conflict, Levelling strategy Example for the delta calibration strategy #leveling-strategy.delta-calibration.enable true # Enable basic delta calibration #leveling-strategy.delta-calibration.radius 100 # the probe radius Example for the delta grid leveling strategy #leveling-strategy.delta-grid.enable true # Enable grid leveling #leveling-strategy.delta-grid.radius 50 # Grid radius in millimeters #leveling-strategy.delta-grid.size 7 # Grid size, must be an odd number #leveling-strategy.delta-grid.do_home true # Whether to home before calibration #leveling-strategy.delta-grid.save true # Whether to automatically save the grid #leveling-strategy.delta-grid.initial_height 10 # Height at which to start probling Panel See Please find your panel on the wiki and copy/paste the right configuration here panel.enable false # Set to true to enable the panel code Example for reprap discount GLCD on glcd EXP1 is to left and EXP2 is to right, pin 1 is bottom left, pin 2 is top left etc. +5v is EXP1 pin 10, Gnd is EXP1 pin 9 #panel.lcd reprap_discount_glcd # #panel.spi_channel 0 # SPI channel to use ; GLCD EXP1 Pins 3,5 (MOSI, SCLK) #panel.spi_cs_pin 0.16 # SPI chip select ; GLCD EXP1 Pin 4 #panel.encoder_a_pin 3.25!^ # Encoder pin ; GLCD EXP2 Pin 3 #panel.encoder_b_pin 3.26!^ # Encoder pin ; GLCD EXP2 Pin 5 #panel.click_button_pin 1.30!^ # Click button ; GLCD EXP1 Pin 2 #panel.buzz_pin 1.31 # Pin for buzzer ; GLCD EXP1 Pin 1 #panel.back_button_pin 2.11!^ # Back button ; GLCD EXP2 Pin 8 panel.menu_offset 0 # Some panels will need 1 here panel.alpha_jog_feedrate 6000 # X jogging feedrate in mm/min panel.beta_jog_feedrate 6000 # Y jogging feedrate in mm/min panel.gamma_jog_feedrate 200 # Z jogging feedrate in mm/min panel.hotend_temperature 185 # Temp to set hotend when preheat is selected panel.bed_temperature 60 # Temp to set bed when preheat is selected Custom menus : Example of a custom menu entry, which will show up in the Custom entry. NOTE _ gets converted to space in the menu and commands, | is used to separate multiple commands custom_menu.power_on.enable true # custom_menu.power_on.name Power_on # custom_menu.power_on.command M80 # custom_menu.power_off.enable true # custom_menu.power_off.name Power_off # custom_menu.power_off.command M81 # Network settings See network.enable true # Enable the ethernet network services network.webserver.enable true # Enable the webserver network.telnet.enable true # Enable the telnet server network.ip_address auto # Use dhcp to get ip address Uncomment the 3 below to manually setup ip address #network.ip_address 192.168.3.222 # The IP address #network.ip_mask 255.255.255.0 # The ip mask #network.ip_gateway 192.168.3.1 # The gateway address #network.mac_override xx.xx.xx.xx.xx.xx # Override the mac address, only do this if you have a conflict System configuration Serial communications configuration ( baud rate defaults to 9600 if undefined ) For communication over the UART port, not the USB/Serial port uart0.baud_rate 11520 # Baud rate for the default hardware ( UART ) serial port second_usb_serial_enable false # This enables a second USB serial port #leds_disable true # Disable using leds after config loaded #play_led_disable true # Disable the play led Kill button maybe assigned to a different pin, set to the onboard pin by default See kill_button_enable true # Set to true to enable a kill button kill_button_pin 2.12 # Kill button pin. default is same as pause button 2.12 (2.11 is another good choice) #msd_disable false # Disable the MSD (USB SDCARD), see link #dfu_enable false # For linux developers, set to true to enable DFU Only needed on a smoothieboard See link

currentcontrol_module_enable true # Control stepper motor current via the configuration file

Sorry for the edit, but the forum software posted it “while it was not finished” due to a keyboard combination.

Imported from wikidot

Arthur_Wolf · March 21, 2018, 11:42am

Just don’t use PID for your bed. It’s useful for hotends, but for beds you don’t really need it and it can cause the sorts of problems you have. Just use the normal method without PID, or the bang-bang method ( probably better with a relay )

JulienGantner_SW · March 23, 2018, 4:58pm

Thanks for your reply. I’ll investigate it further.

I found the bang-bang method description in the docs but i’m a bit confused about the normal method. Can you point me to the documentation of that? As far as i understood the docs, the PID control seems to be active if i don’t configure it otherwise (aka bang-bang). Am i wrong with that?

I do really appreciate any hints on how to solve the issue.

JulienGantner_SW · April 1, 2018, 4:48pm

Just to update anyone who is interested. Changes settings didn’t lead to the expected results so i formatted the SD-Card and started over. With the exact same config the results do look promising now. I’m super happy with that. The thing that nags me is that i could not find the concrete problem that caused the effect. I suspect that it has something to do with the config overrides but i don`t see any way to prove or falsify this.