Calibrating acceleration and jerk

Hey all,

Recently during a discussion helping someone with settings (here: [forums.reprap.org]), Sublime brought up that Marlin's default acceleration is probably too high for Mendel-type printers (which happens to be what my printer uses, to relative success). This got me wondering, is there some sort of calibration process recommended for fine-tuning acceleration and jerk?

I could do a brute-force test, printing a cube or some other calibration object at various acceleration and jerk settings and just see what looked best, but I was wondering if there's a good way to systematically tune these values, e.g., turn up acceleration if you see this, turn down acceleration if you see that. It seems that direction changes would be most sensitive to these settings, but I haven't been able to think of a clear way this would manifest, besides skipped steps if accel/jerk is too high.

Thanks!

Okay, since there hasn't been an answer, I think I'll just try out a variety of settings and see what comes out.

Here's my plan: print out a plate of precision blocks from here: [www.thingiverse.com] using sfact's tower plugin. Then, in between each part I can add a few gcode lines setting the acceleration and jerk to different values.

Any recommendations as to what sort of values to use for a Prusa i2 using Marlin? I'll post over in the firmware folder to find out more about DEFAULT_ACCELERATION vs. DEFAULT_MAX_ACCELERATION, since its not immediately clear what the differences are.

Too much acceleration will cause the frame to wobble and the axis to overshoot on sharp corners. In extreme it will cause missed steps, especially on rapid changes of direction in narrow infill.

Too little may cause inaccurate flow rate as the extruder lags.

---

[www.hydraraptor.blogspot.com]

I will be interested in what you find best, I have been using 3000 accel for x and y for about 4 months now, print quality is mainly good, but I get more shaking than I would like, just turned mine down to 2000 with slicer 098 and seems to be shaking a lot less and print quality is no worse. I will probably try even lower for small parts.

Bringing this up from the depths, has anyone created a procedure for properly setting jerk and acceleration? I have just been doing it by feel so far. What are the benifits of finding the optimal amount for these settings?

---

WWW.ZATOPA.COM - Your Place for high quality 3D Printing Filament and accessories

Hello TopherMan,

Personally I think a lot of these initial firmware acceleration values in most firmware packages were meant to impress, display and showcase the speed capabilities of the machine/printer itself, and not necessarily turning the machine in to a workable 3d printer that produces reliable quality prints.
Print FAST (and with high firmware acceleration & jerk values) throw the print in the garbage when done, Print SLOWER (and with lower acceleration & jerk values), and you stand a chance a achieving a successful high quality print.

The below values work for my machine setup, which the chassis is designed to be both rigid and lightweight
and is constructed out of 6061-T6 Aluminum Plate, I designed my chassis and selected appropriate build materials
to counter any chassis flex during printing, acceleration, jerk and reciprocating forces.

For spindly designed machines using M8 thread stock with printed plastic chassis connectors, wooden chassis box,
and printed plastic chassis/box, that do not have the rigidity of a competent design and build materials, you may need to further
reduce your Acceleration & Jerk Variables.

//=========================================================
//===========Acceleration & Jerk Variables=================
//=========================================================
//Marlin_v1.0.0 RC2 on Gen 6

// Feedrates & ACCELERATION
#define DEFAULT_MAX_FEEDRATE {500, 500, 5, 45} // (mm/sec)

// #define DEFAULT_MAX_ACCELERATION {9000,9000,100,10000}
// 032813_seems to accelerate to rapidly causing the stepper motor/or belt to skip a create a offset error ruinng the print. Reduce values.
#define DEFAULT_MAX_ACCELERATION {3500,3500,100,2000} // X, Y, Z, E maximum start speed for accelerated moves.

// #define DEFAULT_ACCELERATION 3000 // X, Y, Z and E max acceleration in mm/s^2 for printing moves
#define DEFAULT_ACCELERATION 2000 // X, Y, Z and E max acceleration in mm/s^2 for printing moves.
#define DEFAULT_RETRACT_ACCELERATION 2000 // X, Y, Z and E max acceleration in mm/s^2 for retracts.

//
// #define DEFAULT_XYJERK 20.0 // (mm/sec)
// 040213_XY_changed to 15.0, to reduce vibration in small detail/thin walled prints, reduce any corner print quality issues and layer offset issues.
// 060113_XY_changed to 10.0, to reduce jerk in small detail/thin walled prints and reduce any layer offset shifting. FIXED offset layer issue !!!
#define DEFAULT_XYJERK 10.0 // (mm/sec)
#define DEFAULT_ZJERK 0.4 // (mm/sec)
#define DEFAULT_EJERK 5.0 // (mm/sec)
//===========================================================================

Your mileage may vary with the above settings, but it least it gives you an idea what others have been successful using.

Hope my experience helps you... enjoy Happy Printing !

<sub>Shawn
__________________________________________________________________________________________________________________

25+ Years Experience as a Manufacturing Engineer and New Product Developer
Three Years Experience... Printing 6-8 hours a day, 5 days a week, complex and close tolerance functional engineering prototypes.
Printing PLA @0.1mm Layer Height with +- 0.05mm tolerance for all dimensional shapes (except slightly undersized hole I.D.s).
No printing of... toys, trinkets, low quality prints, or other useless printed objects.</sub>

Top man, I think you may have just answered all my questions in one post. i have been having similar problems as the original poster.

si

Quote
ShawnT98027
Hello TopherMan,

Personally I think a lot of these initial firmware acceleration values in most firmware packages were meant to impress, display and showcase the speed capabilities of the machine/printer itself, and not necessarily turning the machine in to a workable 3d printer that produces reliable quality prints.
Print FAST (and with high firmware acceleration & jerk values) throw the print in the garbage when done, Print SLOWER (and with lower acceleration & jerk values), and you stand a chance a achieving a successful high quality print.

The below values work for my machine setup, which the chassis is designed to be both rigid and lightweight
and is constructed out of 6061-T6 Aluminum Plate, I designed my chassis and selected appropriate build materials
to counter any chassis flex during printing, acceleration, jerk and reciprocating forces.

For spindly designed machines using M8 thread stock with printed plastic chassis connectors, wooden chassis box,
and printed plastic chassis/box, that do not have the rigidity of a competent design and build materials, you may need to further
reduce your Acceleration & Jerk Variables.

//=========================================================
//===========Acceleration & Jerk Variables=================
//=========================================================
//Marlin_v1.0.0 RC2 on Gen 6

// Feedrates & ACCELERATION
#define DEFAULT_MAX_FEEDRATE {500, 500, 5, 45} // (mm/sec)

// #define DEFAULT_MAX_ACCELERATION {9000,9000,100,10000}
// 032813_seems to accelerate to rapidly causing the stepper motor/or belt to skip a create a offset error ruinng the print. Reduce values.
#define DEFAULT_MAX_ACCELERATION {3500,3500,100,2000} // X, Y, Z, E maximum start speed for accelerated moves.

// #define DEFAULT_ACCELERATION 3000 // X, Y, Z and E max acceleration in mm/s^2 for printing moves
#define DEFAULT_ACCELERATION 2000 // X, Y, Z and E max acceleration in mm/s^2 for printing moves.
#define DEFAULT_RETRACT_ACCELERATION 2000 // X, Y, Z and E max acceleration in mm/s^2 for retracts.

//
// #define DEFAULT_XYJERK 20.0 // (mm/sec)
// 040213_XY_changed to 15.0, to reduce vibration in small detail/thin walled prints, reduce any corner print quality issues and layer offset issues.
// 060113_XY_changed to 10.0, to reduce jerk in small detail/thin walled prints and reduce any layer offset shifting. FIXED offset layer issue !!!
#define DEFAULT_XYJERK 10.0 // (mm/sec)
#define DEFAULT_ZJERK 0.4 // (mm/sec)
#define DEFAULT_EJERK 5.0 // (mm/sec)
//===========================================================================

Your mileage may vary with the above settings, but it least it gives you an idea what others have been successful using.

Hope my experience helps you... enjoy Happy Printing !

<sub>Shawn
__________________________________________________________________________________________________________________

25+ Years Experience as a Manufacturing Engineer and New Product Developer
Three Years Experience... Printing 6-8 hours a day, 5 days a week, complex and close tolerance functional engineering prototypes.
Printing PLA @0.1mm Layer Height with +- 0.05mm tolerance for all dimensional shapes (except slightly undersized hole I.D.s).
No printing of... toys, trinkets, low quality prints, or other useless printed objects.</sub>