Problems config SCARA ARM marlin

Hello!
I'm working on a project Robotic SCARA arm and I encountered difficulties with calibration. I use firmeware Marlin and I control it with Pronterface. I use ARDUINO MEGA, RAMPS 1.4 and driver DRV8825.
In this Drive you have the code and a picture with the dimensions:
[drive.google.com]

I modified the following lines of code:
#define Linkage_1 248
#define Linkage_2 180
#define SCARA_offset_x 210 // mm
#define SCARA_offset_y -110
#define SCARA_offset_z 0
#define SCARA_RAD2DEG 57.2957795
#define X_MAX_POS 420
#define X_MIN_POS 0
#define Y_MAX_POS 260
#define Y_MIN_POS 0
#define Z_MAX_POS MANUAL_Z_HOME_POS
#define Z_MIN_POS 0
#define MANUAL_X_HOME_POS 630
#define MANUAL_Y_HOME_POS -190
#define MANUAL_Z_HOME_POS 100
#define HOMING_FEEDRATE {2060, 2060, 20*60, 0}
#define DEFAULT_AXIS_STEPS_PER_UNIT {71.11,17.77,1600,2}
#define DEFAULT_MAX_FEEDRATE {200, 200, 30, 25}
#define DEFAULT_MAX_ACCELERATION {1000,1000,1000,1000}

He moves chaotically, it has no linear motion. Can someone help me with this problem?
I don't know where is the start position for the X and Y axis
I follow this project [reprap.org]
Sorry for my english, I use google translate