diff --git a/src/libslic3r/CSGMesh/VoxelizeCSGMesh.hpp b/src/libslic3r/CSGMesh/VoxelizeCSGMesh.hpp
index c76187723..f64d17b9a 100644
--- a/src/libslic3r/CSGMesh/VoxelizeCSGMesh.hpp
+++ b/src/libslic3r/CSGMesh/VoxelizeCSGMesh.hpp
@@ -37,7 +37,11 @@ inline void perform_csg(CSGType op, VoxelGridPtr &dst, VoxelGridPtr &src)
 
     switch (op) {
     case CSGType::Union:
-        grid_union(*dst, *src);
+        if (is_grid_empty(*dst) && !is_grid_empty(*src))
+            dst = clone(*src);
+        else
+            grid_union(*dst, *src);
+
         break;
     case CSGType::Difference:
         grid_difference(*dst, *src);
diff --git a/src/libslic3r/OpenVDBUtils.cpp b/src/libslic3r/OpenVDBUtils.cpp
index 5d00fac0d..21409445f 100644
--- a/src/libslic3r/OpenVDBUtils.cpp
+++ b/src/libslic3r/OpenVDBUtils.cpp
@@ -300,4 +300,9 @@ void rescale_grid(VoxelGrid &grid, float scale)
 //    grid.grid.setTransform(tr);
 }
 
+bool is_grid_empty(const VoxelGrid &grid)
+{
+    return grid.grid.empty();
+}
+
 } // namespace Slic3r
diff --git a/src/libslic3r/OpenVDBUtils.hpp b/src/libslic3r/OpenVDBUtils.hpp
index cb857020f..d4996854c 100644
--- a/src/libslic3r/OpenVDBUtils.hpp
+++ b/src/libslic3r/OpenVDBUtils.hpp
@@ -77,6 +77,8 @@ void grid_union(VoxelGrid &grid, VoxelGrid &arg);
 void grid_difference(VoxelGrid &grid, VoxelGrid &arg);
 void grid_intersection(VoxelGrid &grid, VoxelGrid &arg);
 
+bool is_grid_empty(const VoxelGrid &grid);
+
 } // namespace Slic3r
 
 #endif // OPENVDBUTILS_HPP
diff --git a/src/libslic3r/SLA/Hollowing.cpp b/src/libslic3r/SLA/Hollowing.cpp
index 31289e7ba..634cde469 100644
--- a/src/libslic3r/SLA/Hollowing.cpp
+++ b/src/libslic3r/SLA/Hollowing.cpp
@@ -75,11 +75,12 @@ InteriorPtr generate_interior(const VoxelGrid       &vgrid,
                               const HollowingConfig &hc,
                               const JobController   &ctl)
 {
-    double offset   = hc.min_thickness;
-    double D        = hc.closing_distance;
-    float  in_range = 1.1f * float(offset + D);
-    auto   narrowb  = 3.f / get_voxel_scale(vgrid);
-    float  out_range = narrowb;
+    double voxsc    = get_voxel_scale(vgrid);
+    double offset   = hc.min_thickness;              // world units
+    double D        = hc.closing_distance;           // world units
+    float  in_range = 1.1f * float(offset + D);      // world units
+    float  out_range = 1.f / voxsc; // world units
+    auto   narrowb  = 1.f;  // voxel units (voxel count)
 
     if (ctl.stopcondition()) return {};
     else ctl.statuscb(0, L("Hollowing"));
@@ -91,12 +92,12 @@ InteriorPtr generate_interior(const VoxelGrid       &vgrid,
 
     double iso_surface = D;
     if (D > EPSILON) {
-        in_range = narrowb;
-        gridptr = redistance_grid(*gridptr, -(offset + D), narrowb, in_range);
+        gridptr = redistance_grid(*gridptr, -(offset + D), narrowb, narrowb);
 
-        gridptr = dilate_grid(*gridptr, std::ceil(iso_surface), 0.f);
+        gridptr = dilate_grid(*gridptr, 1.1 * std::ceil(iso_surface), 0.f);
 
         out_range = iso_surface;
+        in_range  = narrowb / voxsc;
     } else {
         iso_surface = -offset;
     }
diff --git a/src/libslic3r/SLA/Hollowing.hpp b/src/libslic3r/SLA/Hollowing.hpp
index c21bdff4e..b6c07aff5 100644
--- a/src/libslic3r/SLA/Hollowing.hpp
+++ b/src/libslic3r/SLA/Hollowing.hpp
@@ -91,15 +91,15 @@ inline InteriorPtr generate_interior(const indexed_triangle_set &mesh,
     auto statusfn = [&ctl](int){ return ctl.stopcondition && ctl.stopcondition(); };
     auto grid = mesh_to_grid(mesh, MeshToGridParams{}
                                               .voxel_scale(voxel_scale)
-                                              .exterior_bandwidth(1.f)
-                                              .interior_bandwidth(1.f)
+                                              .exterior_bandwidth(3.f)
+                                              .interior_bandwidth(3.f)
                                               .statusfn(statusfn));
 
     if (!grid || (ctl.stopcondition && ctl.stopcondition()))
         return {};
 
-    if (its_is_splittable(mesh))
-        grid = redistance_grid(*grid, 0.0f, 6.f / voxel_scale, 6.f / voxel_scale);
+//    if (its_is_splittable(mesh))
+    grid = redistance_grid(*grid, 0.0f, 3.f, 3.f);
 
     return grid ? generate_interior(*grid, hc, ctl) : InteriorPtr{};
 }
@@ -132,11 +132,12 @@ InteriorPtr generate_interior(const Range<It>       &csgparts,
                               const JobController   &ctl = {})
 {
     double mesh_vol = csgmesh_positive_maxvolume(csgparts);
+    double voxsc    = get_voxel_scale(mesh_vol, hc);
 
     auto params = csg::VoxelizeParams{}
-                      .voxel_scale(get_voxel_scale(mesh_vol, hc))
-                      .exterior_bandwidth(1.f)
-                      .interior_bandwidth(1.f)
+                      .voxel_scale(voxsc)
+                      .exterior_bandwidth(3.f)
+                      .interior_bandwidth(3.f)
                       .statusfn([&ctl](int){ return ctl.stopcondition && ctl.stopcondition(); });
 
     auto ptr = csg::voxelize_csgmesh(csgparts, params);
@@ -144,11 +145,10 @@ InteriorPtr generate_interior(const Range<It>       &csgparts,
     if (!ptr || (ctl.stopcondition && ctl.stopcondition()))
         return {};
 
-    if (csgparts.size() > 1 || its_is_splittable(*csg::get_mesh(*csgparts.begin())))
-        ptr = redistance_grid(*ptr,
-                              0.0f,
-                              6.f / params.voxel_scale(),
-                              6.f / params.voxel_scale());
+    // TODO: figure out issues without the redistance
+//    if (csgparts.size() > 1 || its_is_splittable(*csg::get_mesh(*csgparts.begin())))
+
+    ptr = redistance_grid(*ptr, 0.0f, 3.f, 3.f);
 
     return ptr ? generate_interior(*ptr, hc, ctl) : InteriorPtr{};
 }
diff --git a/src/libslic3r/SLAPrint.cpp b/src/libslic3r/SLAPrint.cpp
index 80857e34a..03c0df4ef 100644
--- a/src/libslic3r/SLAPrint.cpp
+++ b/src/libslic3r/SLAPrint.cpp
@@ -13,7 +13,7 @@
 #include <boost/filesystem/path.hpp>
 #include <boost/log/trivial.hpp>
 
-// #define SLAPRINT_DO_BENCHMARK
+ #define SLAPRINT_DO_BENCHMARK
 
 #ifdef SLAPRINT_DO_BENCHMARK
 #include <libnest2d/tools/benchmark.h>