Posts: 1
Joined: Sat Nov 23, 2019 8:37 pm

Accel/jerk settings not changing

Sat Nov 23, 2019 8:46 pm

I'm not even sure where to begin to figure how it's happening or if i'm even understanding it right, but here it is.
Recently updated my f/w to the latest marlin since I was installing a bltouch sensor(haven't updated since I built it years ago), so I had to redo my whole f/w config. The problem i've been having constantly now is that it gets to a point in prints where it is just so jerky with quick movements in things like infill that the y axis skips and throws it all off. Printing around 30-40mm/s so not anything special. I figured my biggest problem would be to change the acceleration and jerk values in the f/w, but the problem I have is that when I connect in S3D it just tells me a complete set of different values that are much higher than what i'm specifying. Also noticed in the prints that i makes no difference if I change those values which leads me to believe it's the program even more, but I just don't get what's doing it.
Firmware entry:

Code: Select all

#define DEFAULT_AXIS_STEPS_PER_UNIT   { 80, 80, 3840, 760.909 }

 * Default Max Feed Rate (mm/s)
 * Override with M203
 *                                      X, Y, Z, E0 [, E1[, E2[, E3[, E4]]]]
#define DEFAULT_MAX_FEEDRATE          { 250, 250, 2, 25 }

 * Default Max Acceleration (change/s) change = mm/s
 * (Maximum start speed for accelerated moves)
 * Override with M201
 *                                      X, Y, Z, E0 [, E1[, E2[, E3[, E4]]]]
#define DEFAULT_MAX_ACCELERATION      { 1000, 1000, 50, 1000 }

 * Default Acceleration (change/s) change = mm/s
 * Override with M204
 *   M204 P    Acceleration
 *   M204 R    Retract Acceleration
 *   M204 T    Travel Acceleration
#define DEFAULT_ACCELERATION          1000   // X, Y, Z and E acceleration for printing moves
#define DEFAULT_RETRACT_ACCELERATION  3000   // E acceleration for retracts
#define DEFAULT_TRAVEL_ACCELERATION   1000    // X, Y, Z acceleration for travel (non printing) moves

 * Default Jerk (mm/s)
 * Override with M205 X Y Z E
 * "Jerk" specifies the minimum speed change that requires acceleration.
 * When changing speed and direction, if the difference is less than the
 * value set here, it may happen instantaneously.
#define DEFAULT_XJERK                 10.0
#define DEFAULT_YJERK                 10.0
#define DEFAULT_ZJERK                  0.4
#define DEFAULT_EJERK                  5.0

 * S-Curve Acceleration
 * This option eliminates vibration during printing by fitting a Bézier
 * curve to move acceleration, producing much smoother direction changes.
 * See https://github.com/synthetos/TinyG/wiki/Jerk-Controlled-Motion-Explained
Printout from comm tab:

Code: Select all

Attempting connection at \\.\COM4...
READ: start
  Connected to machine!
READ: echo:Marlin 1.1.9
Marlin 1.1.9
Last Updated: 2018-08-01 | Author: (none, default config)
Compiled: Nov 23 2019
Free Memory: 4841  PlannerBufferBytes: 1488
V56 stored settings retrieved (656 bytes; crc 13622)
G21    ; (mm)
Filament settings: Disabled
M200 D1.75
M200 D0
Steps per unit:
M92 X80.00 Y80.00 Z3840.00 E760.91
Maximum feedrates (units/s):
M203 X250.00 Y250.00 Z2.00 E25.00
Maximum Acceleration (units/s2):
M201 X3000 Y3000 Z100 E10000
Acceleration (units/s2): P<print_accel> R<retract_accel> T<travel_accel>
M204 P3000.00 R3000.00 T3000.00
Advanced: Q<min_segment_time_us> S<min_feedrate> T<min_travel_feedrate> J<junc_dev>
M205 Q20000 S0.00 T0.00 J0.02
Home offset:
M206 X0.00 Y0.00 Z0.00
Auto Bed Leveling:
M420 S0 Z0.00
PID settings:
M301 P24.50 I1.87 D80.27
M304 P538.11 I54.29 D1333.52
Z-Probe Offset (mm):
M851 Z-1.05
Active Extruder: 0

Posts: 166
Joined: Mon Mar 02, 2015 1:23 pm

Re: Accel/jerk settings not changing

Mon Nov 25, 2019 12:46 pm

Adjusting the Accel Jerk on two Prussa machines I built saved them from shaking to death.

It’s been a few years since I messed with ‘Jerk’ and Marlin code... So, will be brief....Perhaps this may help:

Attached screenshots show my comments on old printout of the settings reported from Simplify3d by issuing M501 and/or M503 in Simplify’s command field.

Summary of what you’ll read:
1. Was able to change the “Vxy-Jerk” via the LCD on the printer, not by changing it in Code.
2. After changing them via LCD, I issued M500 (from Simplify) to Save the changes to the eeprom. I also Saved them via the LCD panel, just to be sure.
3. Then, Issued M501 and/or M503 to verify they stayed changed.
They did (in actual eeprom but, not in code). Eeprom takes priority over code. So, Happy Camper :D

Good luck!
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