Add linear bearing, remove warnings, tweak y rail offset.

lib/Belt_Generator.scad

 
 // Set maximum_diameter to the shorter of your x or y axis.
 // It is used to limit length of straights and diameter of loops and spirals.
-maximum_diameter = 200;	
+maximum_diameter = 800;	
 
 // Tooth profile default values chosen from belts offered in catalog pages at http://sdp-si.com
 // Tooth profile defaults are ordered: tooth_profile, tooth_pitch, back_thickness, belt_width

lib/Pulley_T-MXL-XL-HTD-GT2_N-tooth.scad

 
 retainer = 1;		// Belt retainer above teeth, 0 = No, 1 = Yes
 retainer_ht = 1.5;	// height of retainer flange over pulley, standard = 1.5
-idler = 1;			// Belt retainer below teeth, 0 = No, 1 = Yes
+idler = 0;			// Belt retainer below teeth, 0 = No, 1 = Yes
 idler_ht = 1.5;		// height of idler flange over pulley, standard = 1.5
 
 pulley_t_ht = 7.3;	// length of toothed part of pulley, standard = 12
 pulley_b_ht = 7;		// pulley base height, standard = 8. Set to same as idler_ht if you want an idler but no pulley.
 pulley_b_dia = 16;	// pulley base diameter, standard = 20
-no_of_nuts = 2;		// number of captive nuts required, standard = 1
+no_of_nuts = 0;		// number of captive nuts required, standard = 1
 nut_angle = 90;		// angle between nuts, standard = 90
 nut_shaft_distance = 1.2;	// distance between inner face of nut and shaft, can be negative.
 
 				
 		//captive nut and grub screw holes
 	
-		if ( pulley_b_ht < m3_nut_flats ) { echo ("CAN'T DRAW CAPTIVE NUTS, HEIGHT LESS THAN NUT DIAMETER!!!"); } else {
-		if ( (pulley_b_dia - motor_shaft)/2 < m3_nut_depth + 3 ) { echo ("CAN'T DRAW CAPTIVE NUTS, DIAMETER TOO SMALL FOR NUT DEPTH!!!"); } else {
+		if ( pulley_b_ht < m3_nut_flats && no_of_nuts > 0) { echo ("CAN'T DRAW CAPTIVE NUTS, HEIGHT LESS THAN NUT DIAMETER!!!"); } else {
+		if ( (pulley_b_dia - motor_shaft)/2 < m3_nut_depth + 3 && no_of_nuts > 0) { echo ("CAN'T DRAW CAPTIVE NUTS, DIAMETER TOO SMALL FOR NUT DEPTH!!!"); } else if (no_of_nuts > 0) {
 	
 			for(j=[1:no_of_nuts]) rotate([0,0,j*nut_angle])
 			translate([0,0,nut_elevation])rotate([90,0,0])

lib/linear_bearing.scad

+
+// #######################################################
+// ################### Linear Bearings ###################
+// #######################################################
+
+lm8uu_outer = 15;
+lm8uu_inner = 8;
+lm8uu_height = 24;
+
+module lm8uu() {
+    $fn = 15;
+    difference() {
+        cylinder(d = lm8uu_outer, h = lm8uu_height);
+        translate([0, 0, -1])
+            cylinder(d = lm8uu_inner, h = lm8uu_height + 2);
+    }
+}
+
+//lm8uu();

lib/rail_mount.scad

 rail_mount_height = 11;
 
 rail_dia = 8;
-rail_y_off_1 = 5;
+rail_y_off_1 = 10;
 
 cutout_width = 0.5;
 
             translate([0, 0, rail_mount_height + rail_mount_wall -2.5])
                 cylinder(d = 6.1, h = 3.8);
         }
+        
+        translate([-10, -10, -22])
+            cube([30, 30, 30]);
+        
+        translate([-10, -10, 2 * slot - 8])
+            cube([30, 30, 30]);
     }
 }
 

xyRepRap.scad

 // display heatbed centered in print volume
 bed_draw_height = (outer_height - heatbed_height) / 2;
 
+echo(print_x=heatbed_width, print_y=heatbed_length);
+echo(frame_x=outer_width, frame_y=outer_length, frame_z=outer_height);
+
 // #######################################################
 // ###################### Libraries ######################
 // #######################################################
 include <lib/Pulley_T-MXL-XL-HTD-GT2_N-tooth.scad>
 include <lib/bearing_idler.scad>
 include <lib/rail_mount.scad>
+include <lib/linear_bearing.scad>
 
 module gt2_belt(length) {
     difference() {
         rotate([-90, 0, 0])
         cylinder(d = rail_dia, h = outer_length - (2 * slot) - nema17_size - rail_mount_dist);
     
+    // some lm8uu bearings on red side
+    color("yellow")
+    for (i = [0 : 30 : 60]) {
+        translate([rail_dia / 2 + rail_y_off_1, 60 + i, -30])
+            rotate([-90, 0, 0])
+            lm8uu();
+    }
+    
     // rail mounts for blue side
     color("green")
     translate([0, 2 * rail_mount_dist, -2 * slot])
     translate([outer_width - (2 * slot) - rail_dia / 2 - rail_y_off_1, 18, -30])
         rotate([-90, 0, 0])
         cylinder(d = rail_dia, h = outer_length - (2 * slot) - nema17_size - rail_mount_dist);
+    
+    // some lm8uu bearings on red side
+    color("yellow")
+    for (i = [0 : 30 : 60]) {
+        translate([outer_width - (2 * slot) - rail_dia / 2 - rail_y_off_1, 60 + i, -30])
+            rotate([-90, 0, 0])
+            lm8uu();
+    }
+    
+    // rail mounts for red side
+    color("green")
+    translate([outer_width - (2 * slot), 2 * rail_mount_dist + rail_mount_len, -2 * slot])
+        rotate([0, 0, 180])
+        rail_mount(slot);
+    color("green")
+    translate([outer_width - (2 * slot), outer_length - (2 * slot) - nema17_size - rail_mount_dist + 5 + rail_mount_len, -2 * slot])
+        rotate([0, 0, 180])
+        rail_mount(slot);
 }
 
 x_rail_dist = 50;