Problem is that the kinematic model in scarakins.c is for a scara with 3 angular joints and a linear joint and also two angular joints that move the table. You could easily remove those last two (ie j4/a and j5/b) from the kinematic as they are just looped through. J3/c however is part of the calculation so to remove that you will need to have a closer look at the forward and inverse kinematic model.
Code:
/* joint[0], joint[1] and joint[3] are in degrees and joint[2] is in length units */
static
int scaraKinematicsForward(const double * joint,
EmcPose * world,
const KINEMATICS_FORWARD_FLAGS * fflags,
KINEMATICS_INVERSE_FLAGS * iflags)
{
double a0, a1, a3;
double x, y, z, c;
/* convert joint angles to radians for sin() and cos() */
a0 = joint[0] * ( PM_PI / 180 );
a1 = joint[1] * ( PM_PI / 180 );
a3 = joint[3] * ( PM_PI / 180 );
/* convert angles into world coords */
a1 = a1 + a0;
a3 = a3 + a1;
x = D2*cos(a0) + D4*cos(a1) + D6*cos(a3);
y = D2*sin(a0) + D4*sin(a1) + D6*sin(a3);
z = D1 + D3 - joint[2] - D5;
c = a3;
*iflags = 0;
if (joint[1] < 90)
*iflags = 1;
world->tran.x = x;
world->tran.y = y;
world->tran.z = z;
world->c = c * 180 / PM_PI;
world->a = joint[4];
world->b = joint[5];
return (0);
} //scaraKinematicsForward()
static int scaraKinematicsInverse(const EmcPose * world,
double * joint,
const KINEMATICS_INVERSE_FLAGS * iflags,
KINEMATICS_FORWARD_FLAGS * fflags)
{
double a3;
double q0, q1;
double xt, yt, rsq, cc;
double x, y, z, c;
x = world->tran.x;
y = world->tran.y;
z = world->tran.z;
c = world->c;
/* convert degrees to radians */
a3 = c * ( PM_PI / 180 );
/* center of end effector (correct for D6) */
xt = x - D6*cos(a3);
yt = y - D6*sin(a3);
/* horizontal distance (squared) from end effector centerline
to main column centerline */
rsq = xt*xt + yt*yt;
/* joint 1 angle needed to make arm length match sqrt(rsq) */
cc = (rsq - D2*D2 - D4*D4) / (2*D2*D4);
if(cc < -1) cc = -1;
if(cc > 1) cc = 1;
q1 = acos(cc);
if (*iflags)
q1 = -q1;
/* angle to end effector */
q0 = atan2(yt, xt);
/* end effector coords in inner arm coord system */
xt = D2 + D4*cos(q1);
yt = D4*sin(q1);
/* inner arm angle */
q0 = q0 - atan2(yt, xt);
/* q0 and q1 are still in radians. convert them to degrees */
q0 = q0 * (180 / PM_PI);
q1 = q1 * (180 / PM_PI);
joint[0] = q0;
joint[1] = q1;
joint[2] = D1 + D3 - D5 - z;
joint[3] = c - ( q0 + q1);
joint[4] = world->a;
joint[5] = world->b;
*fflags = 0;
return (0);
} // scaraKinematicsInverse()
