diff --git a/lib/Slic3r/Layer.pm b/lib/Slic3r/Layer.pm
index 80b712a642..d22188ab5d 100644
--- a/lib/Slic3r/Layer.pm
+++ b/lib/Slic3r/Layer.pm
@@ -12,7 +12,7 @@ has 'slicing_errors'    => (is => 'rw');
 has 'slice_z'           => (is => 'lazy');
 has 'print_z'           => (is => 'lazy');
 has 'height'            => (is => 'lazy');
-has 'flow'              => (is => 'ro', default => sub { $Slic3r::flow });
+has 'flow'              => (is => 'lazy');
 
 # collection of expolygons generated by slicing the original geometry;
 # also known as 'islands' (all regions are merged here)
@@ -51,6 +51,8 @@ sub _build_height {
     return $self->id == 0 ? $Slic3r::Config->get_value('first_layer_height') : $Slic3r::Config->layer_height;
 }
 
+sub _build_flow { $Slic3r::flow }
+
 # layer height of interface paths in unscaled coordinates
 sub support_material_interface_height {
     my $self = shift;
diff --git a/lib/Slic3r/Print.pm b/lib/Slic3r/Print.pm
index fcbfd580b9..fe9f164b7d 100644
--- a/lib/Slic3r/Print.pm
+++ b/lib/Slic3r/Print.pm
@@ -554,7 +554,7 @@ sub make_skirt {
     $skirt_height = $self->layer_count if $skirt_height > $self->layer_count;
     my @points = ();
     foreach my $obj_idx (0 .. $#{$self->objects}) {
-        my @layers = map $self->objects->[$obj_idx]->layer($_), 0..($skirt_height-1);
+        my @layers = map $self->objects->[$obj_idx]->layers->[$_], 0..($skirt_height-1);
         my @layer_points = (
             (map @$_, map @$_, map @{$_->slices}, @layers),
             (map @$_, map @{$_->thin_walls}, map @{$_->regions}, @layers),
diff --git a/lib/Slic3r/Print/Object.pm b/lib/Slic3r/Print/Object.pm
index 78c637aacc..86cebb675d 100644
--- a/lib/Slic3r/Print/Object.pm
+++ b/lib/Slic3r/Print/Object.pm
@@ -2,7 +2,7 @@ package Slic3r::Print::Object;
 use Moo;
 
 use Slic3r::ExtrusionPath ':roles';
-use Slic3r::Geometry qw(scale unscale deg2rad scaled_epsilon);
+use Slic3r::Geometry qw(Z scale unscale deg2rad scaled_epsilon);
 use Slic3r::Geometry::Clipper qw(diff_ex intersection_ex union_ex);
 use Slic3r::Surface ':types';
 
@@ -13,21 +13,36 @@ has 'size'              => (is => 'rw', required => 1);
 has 'copies'            => (is => 'rw', default => sub {[ [0,0] ]});
 has 'layers'            => (is => 'rw', default => sub { [] });
 
+sub BUILD {
+    my $self = shift;
+ 	 
+    # make layers
+    while (!@{$self->layers} || $self->layers->[-1]->slice_z < $self->size->[Z]) {
+        push @{$self->layers}, Slic3r::Layer->new(
+            object  => $self,
+            id      => $#{$self->layers} + 1,
+        );
+    }
+}
+
 sub layer_count {
     my $self = shift;
     return scalar @{ $self->layers };
 }
 
-sub layer {
+sub get_layer_range {
     my $self = shift;
-    my ($layer_id) = @_;
+    my ($min_z, $max_z) = @_;
     
-    # extend our print by creating all necessary layers
-    for (my $i = $self->layer_count; $i <= $layer_id; $i++) {
-        push @{ $self->layers }, Slic3r::Layer->new(id => $i, object => $self);
+    my ($min_layer, $max_layer) = (0, undef);
+ 	for my $layer (@{$self->layers}) {
+        $min_layer = $layer->id if $layer->slice_z <= $min_z;
+        if ($layer->slice_z >= $max_z) {
+            $max_layer = $layer->id;
+            last;
+        }
     }
-    
-    return $self->layers->[$layer_id];
+    return ($min_layer, $max_layer);
 }
 
 sub slice {
@@ -41,7 +56,7 @@ sub slice {
         my $apply_lines = sub {
             my $lines = shift;
             foreach my $layer_id (keys %$lines) {
-                my $layerm = $self->layer($layer_id)->region($region_id);
+                my $layerm = $self->layers->[$layer_id]->region($region_id);
                 push @{$layerm->lines}, @{$lines->{$layer_id}};
             }
         };
@@ -441,7 +456,7 @@ sub combine_infill {
             # we do this from the greater depth to the smaller
             for (my $d = $Slic3r::Config->infill_every_layers - 1; $d >= 1; $d--) {
                 next if ($i - $d) <= 0; # do not combine infill for bottom layer
-                my $lower_layerm = $self->layer($i - 1)->regions->[$region_id];
+                my $lower_layerm = $self->layers->[$i - 1]->regions->[$region_id];
                 
                 # select surfaces of the lower layer having the depth we're looking for
                 my @lower_surfaces = grep $_->depth_layers == $d && $_->surface_type == S_TYPE_INTERNAL,
diff --git a/lib/Slic3r/TriangleMesh.pm b/lib/Slic3r/TriangleMesh.pm
index 599445967a..d830ba54c9 100644
--- a/lib/Slic3r/TriangleMesh.pm
+++ b/lib/Slic3r/TriangleMesh.pm
@@ -415,14 +415,12 @@ sub slice_facet {
     }
     
     # calculate the layer extents
-    my $min_layer = int((unscale($min_z) - ($Slic3r::Config->get_value('first_layer_height') + $Slic3r::Config->layer_height / 2)) / $Slic3r::Config->layer_height) - 2;
-    $min_layer = 0 if $min_layer < 0;
-    my $max_layer = int((unscale($max_z) - ($Slic3r::Config->get_value('first_layer_height') + $Slic3r::Config->layer_height / 2)) / $Slic3r::Config->layer_height) + 2;
+    my ($min_layer, $max_layer) = $print_object->get_layer_range($min_z, $max_z);
     Slic3r::debugf "layers: min = %s, max = %s\n", $min_layer, $max_layer;
     
     my $lines = {};  # layer_id => [ lines ]
     for (my $layer_id = $min_layer; $layer_id <= $max_layer; $layer_id++) {
-        my $layer = $print_object->layer($layer_id);
+        my $layer = $print_object->layers->[$layer_id];
         $lines->{$layer_id} ||= [];
         push @{ $lines->{$layer_id} }, $self->intersect_facet($facet_id, $layer->slice_z);
     }