[Solved] Smoothie takes a corner too fast

kbranch_SW · February 28, 2017, 11:01pm

I ran into a problem today where my printer skips a few steps in the Y axis because the bed tries to stop too quickly while going around a 90 degree corner. I tried severely reducing both acceleration and junction deviation (to 100 and .001, respectively), to no real effect. I’ve also tried formatting the SD card and starting with a fresh config file.

I upgraded my firmware recently (from some November 2016 build to edge-9399ed7 from February 7th), but I also switched to a much heavier bed at the same time. It’s possible that it’s been doing this for a long time, and it just wasn’t enough to skip steps with the lighter bed.

Am I doing something wrong, or is this a bug in Smoothie?

I’m running a Frankenstein cartesian 3D printer from a Smoothieboard using the most recent version of Smoothieware (edge-9399ed7 from February 7th).

Here’s my config file:

+ show block

– hide block

# Smoothieboard configuration file, see # 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 Arm solution configuration : Cartesian robot. Translates mm positions into stepper positions See alpha_steps_per_mm 160 # Steps per mm for alpha ( X ) stepper beta_steps_per_mm 160 # Steps per mm for beta ( Y ) stepper gamma_steps_per_mm 1600 # Steps per mm for gamma ( Z ) stepper Planner module configuration : Look-ahead and acceleration configuration See acceleration 800 # Acceleration in mm/second/second. z_acceleration 100 # Acceleration for Z only moves in mm/s^2, 0 uses acceleration which is the default. DO NOT SET ON A DELTA junction_deviation 0.001 # 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 12000 # Maximum speed in mm/min y_axis_max_speed 12000 # Maximum speed in mm/min z_axis_max_speed 300 # 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 1.5 # 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 0.7 # Z stepper motor current gamma_max_rate 300.0 # 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 183 # 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/sec² extruder.hotend.max_speed 60 # 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 #laser_module_ttl_pin 1.30 # This pin turns on when the laser turns on, and off when the laser turns off. #laser_module_maximum_power 1.0 # This is the maximum duty cycle that will be applied to the laser #laser_module_minimum_power 0.0 # This is a value just below the minimum duty cycle that keeps the laser # active without actually burning. #laser_module_default_power 0.8 # This is the default laser power that will be used for cuts if a power has not been specified. The value is a scale between # the maximum and minimum power levels specified above #laser_module_pwm_period 20 # This sets the pwm frequency as the period in microseconds 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 295 # Set maximum temperature - Will prevent heating above 300 by default temperature_control.hotend.min_temp 5 # 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 140 # 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 25 # How far from the set temperature it can wander, max setting is 63°C PID configuration See temperature_control.hotend.p_factor 15 # P ( proportional ) factor temperature_control.hotend.i_factor 0.75 # I ( integral ) factor temperature_control.hotend.d_factor 64 # D ( derivative ) factor #temperature_control.hotend.max_pwm 64 # Max pwm, 64 is a good value if driving a 12v resistor with 24v. Second hotend configuration #temperature_control.hotend2.enable true # Whether to activate this ( “hotend” ) module at all. #temperature_control.hotend2.thermistor_pin 0.25 # Pin for the thermistor to read #temperature_control.hotend2.heater_pin 1.23 # Pin that controls the heater #temperature_control.hotend2.thermistor EPCOS100K # See ##temperature_control.hotend2.beta 4066 # or set the beta value #temperature_control.hotend2.set_m_code 104 # M-code to set the temperature for this module #temperature_control.hotend2.set_and_wait_m_code 109 # M-code to set-and-wait for this module #temperature_control.hotend2.designator T1 # Designator letter for this module #temperature_control.hotend2.p_factor 13.7 # P ( proportional ) factor #temperature_control.hotend2.i_factor 0.097 # I ( integral ) factor #temperature_control.hotend2.d_factor 24 # D ( derivative ) factor #temperature_control.hotend2.max_pwm 64 # Max pwm, 64 is a good value if driving a 12v resistor with 24v. 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 2.5 # Pin that controls the heater #temperature_control.bed.thermistor Honeywell100K # See temperature_control.bed.beta 4092 # Or set the beta value temperature_control.bed.max_temp 125 # Set maximum temperature temperature_control.bed.min_temp 5 # Set minimum temperature - Will prevent heating below if set 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 false # 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 104.5 # permanently set the PID values after an auto pid temperature_control.bed.i_factor 3.393 # temperature_control.bed.d_factor 805 # temperature_control.bedsafety.enable true # temperature_control.bedsafety.thermistor_pin 0.25 # temperature_control.bedsafety.heater_pin nc # temperature_control.bedsafety.thermistor EPCOS100K # see temperature_control.bedsafety.designator F temperatureswitch.bed_low.enable false # temperatureswitch.bed_low.switch psu # select which switch to use, matches the name of the defined switch temperatureswitch.bed_low.designator F # first character of the temperature control designator to use as the temperature sensor to monitor temperatureswitch.bed_low.threshold_temp 50 # temperature to trigger at when falling temperatureswitch.bed_low.inverted false # turn the switch off when we trigger (by default switches on when rising and off when falling) temperatureswitch.bed_high.enable false temperatureswitch.bed_high.switch psu temperatureswitch.bed_high.designator F temperatureswitch.bed_high.threshold_temp 60 temperatureswitch.bed_low.inverted true 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 2.4 # Pin this module controls switch.fan.output_type pwm # PWM output settable with S parameter in the input_on_comand switch.fan.max_pwm 127 # Set max pwm for the pin default is 255 switch.misc.enable true # Enable this module switch.misc.input_on_command M42 # Command that will turn this switch on switch.misc.input_off_command M43 # Command that will turn this switch off switch.misc.output_pin 2.6! # Pin this module controls switch.misc.output_type digital # Digital means this is just an on or off pin switch.psu.enable true # turn the SSR on/off switch.psu.input_on_command M80 # switch.psu.input_off_command M81 # switch.psu.output_pin 1.30 # switch.psu.output_type digital # on/off only switch.psu.fail_safe_set_to 0 # so the SSR turns off on a system crash 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 misc # select which switch to use, matches the name of the defined switch #temperatureswitch.hotend.threshold_temp 60.0 # 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 #corexy_homing false # Set to true if homing on a hbot or corexy alpha_min_endstop 1.24^! # 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_min # Or set to home_to_max and set alpha_max and uncomment the alpha_max_endstop alpha_min 0 # This gets loaded as the current position after homing when home_to_min is set alpha_max 245 # This gets loaded as the current position after homing when home_to_max is set beta_min_endstop 1.26^! # 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_min # Or set to home_to_max and set alpha_max and uncomment the alpha_max_endstop beta_min 0 # This gets loaded as the current position after homing when home_to_min is set beta_max 254 # This gets loaded as the current position after homing when home_to_max is set gamma_min_endstop 1.28^! # 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_min # Or set to home_to_max and set alpha_max and uncomment the alpha_max_endstop gamma_min 0 # This gets loaded as the current position after homing when home_to_min is set gamma_max 250 # This gets loaded as the current position after homing when home_to_max is set alpha_max_travel 275 # Max travel in mm for alpha/X axis when homing beta_max_travel 275 # Max travel in mm for beta/Y axis when homing gamma_max_travel 275 # Max travel in mm for gamma/Z axis when homing Optional enable limit switches, actions will stop if any enabled limit switch is triggered #alpha_limit_enable false # Set to true to enable X min and max limit switches #beta_limit_enable false # Set to true to enable Y min and max limit switches #gamma_limit_enable false # Set to true to enable Z min and max limit switches 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 50 # Alpha/X fast homing feedrate in mm/second alpha_slow_homing_rate_mm_s 25 # Alpha/X slow homing feedrate in mm/second beta_fast_homing_rate_mm_s 50 # Beta/Y fast homing feedrate in mm/second beta_slow_homing_rate_mm_s 25 # Beta/Y slow homing feedrate in mm/second gamma_fast_homing_rate_mm_s 4 # Gamma/Z fast homing feedrate in mm/second gamma_slow_homing_rate_mm_s 2 # Gamma/Z 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 1 # Distance to retract from the endstop after it is hit for gamma/Z Optional enable limit switches, actions will stop if any enabled limit switch is triggered (all are set for delta) alpha_limit_enable false # Set to true to enable X min and max limit switches beta_limit_enable false # Set to true to enable Y min and max limit switches gamma_limit_enable false # Set to true to enable Z min and max limit switches Optional order in which axis will home, default is they all home at the same time, If this is set it will force each axis to home one at a time in the specified order #homing_order XYZ # X axis followed by Y then Z last #move_to_origin_after_home false # Move XY to 0,0 after homing #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 #home_z_first true # Uncomment and set to true to home the Z first, otherwise Z homes after XY 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 false # 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 100 # Move feedrate mm/sec zprobe.probe_height 5 # How much above bed to start probe #gamma_min_endstop nc # Normally 1.28. Change to nc to prevent conflict, Levelling strategy Example for 3-point levelling strategy, see wiki documentation for other strategies #leveling-strategy.three-point-leveling.enable true # a leveling strategy that probes three points to define a plane and keeps the Z parallel to that plane #leveling-strategy.three-point-leveling.point1 100.0,0.0 # the first probe point (x,y) optional may be defined with M557 #leveling-strategy.three-point-leveling.point2 200.0,200.0 # the second probe point (x,y) #leveling-strategy.three-point-leveling.point3 0.0,200.0 # the third probe point (x,y) #leveling-strategy.three-point-leveling.home_first true # home the XY axis before probing #leveling-strategy.three-point-leveling.tolerance 0.03 # the probe tolerance in mm, anything less that this will be ignored, default is 0.03mm #leveling-strategy.three-point-leveling.probe_offsets 0,0,0 # the probe offsets from nozzle, must be x,y,z, default is no offset #leveling-strategy.three-point-leveling.save_plane false # set to true to allow the bed plane to be saved with M500 default is false 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.plan9.enable true # network.ip_address auto # Use dhcp to get ip address network.hostname kbranch-smoothie # 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 115200 # Baud rate for the default hardware ( UART ) serial port second_usb_serial_enable true # 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 false # 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 #dfu_enable false # For linux developers, set to true to enable DFU Only needed on a smoothieboard See

currentcontrol_module_enable true # Control stepper motor current via the configuration file

And the smallest g-code file I’ve managed to reproduce the issue with (remove one of the corner segments and it works fine):

+ show block

– hide block

G28 Z0
G1 Z5 F5000
G28 X0 Y0
G1 X115.634 Y173.374 F7800.000
G1 X115.618 Y199.983 F7800.000
G1 X115.591 Y200.069 F7800.000
G1 X115.561 Y200.127 F7800.000
G1 X115.482 Y200.228 F7800.000
G1 X115.400 Y200.293 F7800.000
G1 X115.319 Y200.335 F7800.000
G1 X115.257 Y200.355 F7800.000
G1 X115.134 Y200.370 F7800.000
G1 X115.052 Y200.374 F7800.000
G1 X43.204 Y200.374 F7800.000

I also have a video demonstrating the issue, although I can’t post the link. It’s on YouTube, watch?v=L99QEnSb8MU (the thunk at the end is where it loses steps).

Imported from wikidot

Arthur_Wolf · March 1, 2017, 5:18am

Are you using external drivers ? If so what model ?

kbranch_SW · March 1, 2017, 8:15am

Nope, I’m using the integrated drivers. It might not be apparent in the video, but the thunk is pretty violent. The whole printer shudders, I’m kind of impressed the stepper has that much torque.

kbranch_SW · March 2, 2017, 11:00pm

Any objections if I open this as an issue on GitHub?

Merlin201314_SW · March 3, 2017, 4:06am

How heavy is your new bed?
Having a look at your Beta axis current, i think 1.5 amp for a heavy bed is too low value, i would suggest you to go for a 2 amp(max allowed on smoothie) and see if the problem is solved, then check for the motor temperature, but for a short time you won’t have any problem……
Cheers

kbranch_SW · March 3, 2017, 8:32pm

The bed is pretty beefy, it’s a ~280x280x10mm sheet of aluminum plus the heater and bearings and such. I’d guess it’s 6 pounds or so.

I would guess that I can solve the skipped steps by getting a bigger stepper or upping the current, but the skipped steps are more a symptom of the root problem. The stepper apparently has enough torque that I don’t want to routinely make it flex its muscles, if only for the longevity of my printer. The thunking sound is from the whole printer shaking, not the stepper skipping its steps.

Maybe my expectations are off, but I would have thought that I could tweak junction deviation and acceleration to accommodate an axis of almost any mass that my motors can get moving - Smoothie can be used for CNC mills, after all.

Arthur_Wolf · March 6, 2017, 10:50am

Well, did you try reducing acceleration and junction deviation by a lot ? That should work, it does for everybody else …

kbranch_SW · March 6, 2017, 6:49pm

I did, I took acceleration down to 100 and junction deviation down to 0.001, as noted in the original post (originally 900 and 0.015, I think). Acceleration is visibly slow, yet the thunk is every bit as loud (the bed has a bit of time to get up to full speed, or close to it).

I can remove an arbitrary single line from the rounded corner section of the g-code and get a smooth corner with no thunk, which is part of what makes me think I’ve stumbled across a bug. It’s almost like this specific set of g-code confuses it into thinking it’s not really taking a corner as fast as it thinks it is.

Arthur_Wolf · March 7, 2017, 5:14am

If you tried just one change/didn’t lower it that much, why are you surprised you didn’t find the right value ?
Junction deviation values of 0.0001 or 0.00001 are fairly common for machines with heavy axes like yours, you need to try lowering values ( accel too ) even further.

kbranch_SW · March 7, 2017, 8:31pm

Sorry, I apparently misunderstood the useful range of junction deviation. The documentation mentioned that some CNC mills needed to go as low as 0.001 - between that and the fact that I was reducing it by a factor of 15, I figured I was good.

Anyway, I’ve done some more testing. I tried setting acceleration to a glacially slow 10, but that seemed to make it completely freeze up at the corner (literally, it stopped dead for over a minute before finishing). Here’s a video of the same behavior with acceleration set to 50 for the sake of video length: youtu.be slash fWTfJYaP8Sc

With acceleration set to 75 to avoid the above (still far slower than the machine can handle), I tried junction deviation values of 0.0001, 0.00001 and 0.000001. All three new values behaved exactly the same as 0.001, at least as far as I can tell. The thunk is reduced because the extremely low acceleration prevents it from getting up to any appreciable speed, but it does not decelerate in anticipation of the corner and it’s still a pretty abrupt stop.

The only thing I have been able to do to avoid the thunk is to comment out either line 5 or 6 in the g-code, reducing the number of segments in the corner. This gives me motion exactly like I would expect, even with my original values of 900 and 0.015.

kbranch_SW · March 16, 2017, 6:52pm

Anything else I should try, or does this seem like a bug at this point?

rubencpaulo_SW · March 30, 2017, 12:55pm

I’m having the same problem. Did you find the solution for that??

Arthur_Wolf · March 30, 2017, 1:05pm

I think users with this problem should try the 64bit branch : https://github.com/Smoothieware/Smoothieware/tree/stepticker/use-64bit-fixed-point/FirmwareBin

Speedy64i_SW · April 3, 2017, 4:10pm

I just created a pull request on GitHub titled “Junction deviation tweak #1153” that I think will fix kbranch’s issue. I’ve been running it for the past few months on my 3d printer and milling table with no issues. I noticed this problem when certain gcode files (usually derived from complex images would make the head whip around at ridiculous speeds. I determined it only happened when you had a bunch of very small line segments after a relatively long straight line. Looking at the code, It appeared the junction deviation calculations were being skipped at any line segment under 18.2 degrees. a single 18 degree change may not be an issue, but many of them in quick succession can cause a 180 degree change in a very small timeframe with no deceleration. After applying this fix, all the high speed machine shaking edges went away from my test gcode and everything worked as intended.

kbranch_SW · April 16, 2017, 11:25pm

Sorry, I hadn’t checked this thread for updates in a while. Looks like that pull request #1153 has been merged now, so I just tried the latest firmware binary - it works great, thank you! I get nice deceleration, just like I’d expect.