In Marlin it looks like this:
*/
#define DEFAULT_MAX_ACCELERATION { 500, 500, 3, 5000 } <- max beschleunigung per achse
/**
* 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 <- standart beschleunigung
#define DEFAULT_RETRACT_ACCELERATION 1500 // E acceleration for retracts
#define DEFAULT_TRAVEL_ACCELERATION 2000 // X, Y, Z acceleration for travel (non printing) moves <- beschleunigung für nicht druck wege
/**
* Default Jerk (mm/s) <- Jerk ist der maximale Geschwindigkeitsunterschied, der ohne Beschleunigung ausgeführt werden kann.
*
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 4.0
#define DEFAULT_YJERK 4.0
#define DEFAULT_ZJERK 0.2
#define DEFAULT_EJERK 5.0
To switch use the M-Commands, but the values are depending from your printers model - you must try it out.
The commands you can include to the beginning of the start scipt.
For more informations have a look to RepRap-Forum.org >>> M-Codes, G-Codes >>>
http://reprap.org/wiki/G-code
Regards
horst.w
GER