diff --git a/src/admesh/connect.cpp b/src/admesh/connect.cpp
index 03b13343d..9553e7c4d 100644
--- a/src/admesh/connect.cpp
+++ b/src/admesh/connect.cpp
@@ -396,9 +396,6 @@ static void match_neighbors_nearby(stl_file *stl, const HashEdge &edge_a, const
 // floats of the first edge matches all six floats of the second edge.
 void stl_check_facets_exact(stl_file *stl)
 {
-	if (stl->error)
-		return;
-
   	stl->stats.connected_edges         = 0;
   	stl->stats.connected_facets_1_edge = 0;
   	stl->stats.connected_facets_2_edge = 0;
@@ -444,9 +441,6 @@ void stl_check_facets_exact(stl_file *stl)
 
 void stl_check_facets_nearby(stl_file *stl, float tolerance)
 {
-	if (stl->error)
-		return;
-
   	if (  (stl->stats.connected_facets_1_edge == stl->stats.number_of_facets)
        && (stl->stats.connected_facets_2_edge == stl->stats.number_of_facets)
        && (stl->stats.connected_facets_3_edge == stl->stats.number_of_facets)) {
@@ -476,9 +470,6 @@ void stl_remove_unconnected_facets(stl_file *stl)
 	// A couple of things need to be done here.  One is to remove any completely unconnected facets (0 edges connected) since these are
 	// useless and could be completely wrong.   The second thing that needs to be done is to remove any degenerate facets that were created during
 	// stl_check_facets_nearby().
-	if (stl->error)
-		return;
-
 	auto remove_facet = [stl](int facet_number)
 	{
 		++ stl->stats.facets_removed;
@@ -526,7 +517,6 @@ void stl_remove_unconnected_facets(stl_file *stl)
 	{
 		// Update statistics on face connectivity.
 		auto stl_update_connects_remove_1 = [stl](int facet_num) {
-			assert(! stl->error);
 			//FIXME when decreasing 3_edge, should I increase 2_edge etc?
 			switch ((stl->neighbors_start[facet_num].neighbor[0] == -1) + (stl->neighbors_start[facet_num].neighbor[1] == -1) + (stl->neighbors_start[facet_num].neighbor[2] == -1)) {
 			case 0: // Facet has 3 neighbors
@@ -636,9 +626,6 @@ void stl_remove_unconnected_facets(stl_file *stl)
 
 void stl_fill_holes(stl_file *stl)
 {
-	if (stl->error)
-		return;
-
 	// Insert all unconnected edges into hash list.
 	HashTableEdges hash_table(stl->stats.number_of_facets);
 	for (uint32_t i = 0; i < stl->stats.number_of_facets; ++ i) {
@@ -720,8 +707,6 @@ void stl_fill_holes(stl_file *stl)
 
 void stl_add_facet(stl_file *stl, const stl_facet *new_facet)
 {
-	if (stl->error)
-		return;
 	assert(stl->facet_start.size() == stl->stats.number_of_facets);
 	assert(stl->neighbors_start.size() == stl->stats.number_of_facets);
 	stl->facet_start.emplace_back(*new_facet);
diff --git a/src/admesh/normals.cpp b/src/admesh/normals.cpp
index e11f1a3c1..f20d9e68e 100644
--- a/src/admesh/normals.cpp
+++ b/src/admesh/normals.cpp
@@ -29,61 +29,43 @@
 
 static int stl_check_normal_vector(stl_file *stl, int facet_num, int normal_fix_flag);
 
-static void
-stl_reverse_facet(stl_file *stl, int facet_num) {
-  stl_vertex tmp_vertex;
-  /*  int tmp_neighbor;*/
-  int neighbor[3];
-  int vnot[3];
+static void reverse_facet(stl_file *stl, int facet_num)
+{
+	stl->stats.facets_reversed += 1;
 
-  stl->stats.facets_reversed += 1;
+	int neighbor[3] = { stl->neighbors_start[facet_num].neighbor[0], stl->neighbors_start[facet_num].neighbor[1], stl->neighbors_start[facet_num].neighbor[2] };
+	int vnot[3] = { stl->neighbors_start[facet_num].which_vertex_not[0], stl->neighbors_start[facet_num].which_vertex_not[1], stl->neighbors_start[facet_num].which_vertex_not[2] };
 
-  neighbor[0] = stl->neighbors_start[facet_num].neighbor[0];
-  neighbor[1] = stl->neighbors_start[facet_num].neighbor[1];
-  neighbor[2] = stl->neighbors_start[facet_num].neighbor[2];
-  vnot[0] = stl->neighbors_start[facet_num].which_vertex_not[0];
-  vnot[1] = stl->neighbors_start[facet_num].which_vertex_not[1];
-  vnot[2] = stl->neighbors_start[facet_num].which_vertex_not[2];
+	// reverse the facet
+	stl_vertex tmp_vertex = stl->facet_start[facet_num].vertex[0];
+	stl->facet_start[facet_num].vertex[0] =
+	stl->facet_start[facet_num].vertex[1];
+	stl->facet_start[facet_num].vertex[1] = tmp_vertex;
 
-  /* reverse the facet */
-  tmp_vertex = stl->facet_start[facet_num].vertex[0];
-  stl->facet_start[facet_num].vertex[0] =
-    stl->facet_start[facet_num].vertex[1];
-  stl->facet_start[facet_num].vertex[1] = tmp_vertex;
+	// fix the vnots of the neighboring facets
+	if (neighbor[0] != -1)
+		stl->neighbors_start[neighbor[0]].which_vertex_not[(vnot[0] + 1) % 3] = (stl->neighbors_start[neighbor[0]].which_vertex_not[(vnot[0] + 1) % 3] + 3) % 6;
+	if (neighbor[1] != -1)
+		stl->neighbors_start[neighbor[1]].which_vertex_not[(vnot[1] + 1) % 3] = (stl->neighbors_start[neighbor[1]].which_vertex_not[(vnot[1] + 1) % 3] + 4) % 6;
+	if (neighbor[2] != -1)
+		stl->neighbors_start[neighbor[2]].which_vertex_not[(vnot[2] + 1) % 3] = (stl->neighbors_start[neighbor[2]].which_vertex_not[(vnot[2] + 1) % 3] + 2) % 6;
 
-  /* fix the vnots of the neighboring facets */
-  if(neighbor[0] != -1)
-    stl->neighbors_start[neighbor[0]].which_vertex_not[(vnot[0] + 1) % 3] =
-      (stl->neighbors_start[neighbor[0]].
-       which_vertex_not[(vnot[0] + 1) % 3] + 3) % 6;
-  if(neighbor[1] != -1)
-    stl->neighbors_start[neighbor[1]].which_vertex_not[(vnot[1] + 1) % 3] =
-      (stl->neighbors_start[neighbor[1]].
-       which_vertex_not[(vnot[1] + 1) % 3] + 4) % 6;
-  if(neighbor[2] != -1)
-    stl->neighbors_start[neighbor[2]].which_vertex_not[(vnot[2] + 1) % 3] =
-      (stl->neighbors_start[neighbor[2]].
-       which_vertex_not[(vnot[2] + 1) % 3] + 2) % 6;
+	// swap the neighbors of the facet that is being reversed
+	stl->neighbors_start[facet_num].neighbor[1] = neighbor[2];
+	stl->neighbors_start[facet_num].neighbor[2] = neighbor[1];
 
-  /* swap the neighbors of the facet that is being reversed */
-  stl->neighbors_start[facet_num].neighbor[1] = neighbor[2];
-  stl->neighbors_start[facet_num].neighbor[2] = neighbor[1];
+	// swap the vnots of the facet that is being reversed 
+	stl->neighbors_start[facet_num].which_vertex_not[1] = vnot[2];
+	stl->neighbors_start[facet_num].which_vertex_not[2] = vnot[1];
 
-  /* swap the vnots of the facet that is being reversed */
-  stl->neighbors_start[facet_num].which_vertex_not[1] = vnot[2];
-  stl->neighbors_start[facet_num].which_vertex_not[2] = vnot[1];
-
-  /* reverse the values of the vnots of the facet that is being reversed */
-  stl->neighbors_start[facet_num].which_vertex_not[0] =
-    (stl->neighbors_start[facet_num].which_vertex_not[0] + 3) % 6;
-  stl->neighbors_start[facet_num].which_vertex_not[1] =
-    (stl->neighbors_start[facet_num].which_vertex_not[1] + 3) % 6;
-  stl->neighbors_start[facet_num].which_vertex_not[2] =
-    (stl->neighbors_start[facet_num].which_vertex_not[2] + 3) % 6;
+	// reverse the values of the vnots of the facet that is being reversed
+	stl->neighbors_start[facet_num].which_vertex_not[0] = (stl->neighbors_start[facet_num].which_vertex_not[0] + 3) % 6;
+	stl->neighbors_start[facet_num].which_vertex_not[1] = (stl->neighbors_start[facet_num].which_vertex_not[1] + 3) % 6;
+	stl->neighbors_start[facet_num].which_vertex_not[2] = (stl->neighbors_start[facet_num].which_vertex_not[2] + 3) % 6;
 }
 
-void
-stl_fix_normal_directions(stl_file *stl) {
+void stl_fix_normal_directions(stl_file *stl)
+{
   /*  int edge_num;*/
   /*  int vnot;*/
   int checked = 0;
@@ -104,8 +86,6 @@ stl_fix_normal_directions(stl_file *stl) {
   int id;
   int force_exit = 0;
 
-  if (stl->error) return;
-
   // this may happen for malformed models, see: https://github.com/prusa3d/PrusaSlicer/issues/2209
   if (stl->stats.number_of_facets == 0) return;
 
@@ -125,7 +105,7 @@ stl_fix_normal_directions(stl_file *stl) {
      Arbitrarily starts at face 0.  If this one is wrong, we're screwed.  Thankfully, the chances
      of it being wrong randomly are low if most of the triangles are right: */
   if (stl_check_normal_vector(stl, 0, 0) == 2) {
-      stl_reverse_facet(stl, 0);
+      reverse_facet(stl, 0);
       reversed_ids[reversed_count++] = 0;
   }
 
@@ -144,12 +124,12 @@ stl_fix_normal_directions(stl_file *stl) {
             if (norm_sw[stl->neighbors_start[facet_num].neighbor[j]] == 1) {
                 /* trying to modify a facet already marked as fixed, revert all changes made until now and exit (fixes: #716, #574, #413, #269, #262, #259, #230, #228, #206) */
                 for (id = reversed_count - 1; id >= 0; --id) {
-                    stl_reverse_facet(stl, reversed_ids[id]);
+                    reverse_facet(stl, reversed_ids[id]);
                 }
                 force_exit = 1;
                 break;
             } else {
-                stl_reverse_facet(stl, stl->neighbors_start[facet_num].neighbor[j]);
+                reverse_facet(stl, stl->neighbors_start[facet_num].neighbor[j]);
                 reversed_ids[reversed_count++] = stl->neighbors_start[facet_num].neighbor[j];
             }
         }
@@ -193,7 +173,7 @@ stl_fix_normal_directions(stl_file *stl) {
             /* This is the first facet of the next part. */
             facet_num = i;
             if(stl_check_normal_vector(stl, i, 0) == 2) {
-                stl_reverse_facet(stl, i);
+                reverse_facet(stl, i);
                 reversed_ids[reversed_count++] = i;
             }
 
@@ -209,7 +189,8 @@ stl_fix_normal_directions(stl_file *stl) {
   delete tail;
 }
 
-static int stl_check_normal_vector(stl_file *stl, int facet_num, int normal_fix_flag) {
+static int stl_check_normal_vector(stl_file *stl, int facet_num, int normal_fix_flag)
+{
   /* Returns 0 if the normal is within tolerance */
   /* Returns 1 if the normal is not within tolerance, but direction is OK */
   /* Returns 2 if the normal is not within tolerance and backwards */
@@ -260,26 +241,19 @@ static int stl_check_normal_vector(stl_file *stl, int facet_num, int normal_fix_
   return 4;
 }
 
-void stl_fix_normal_values(stl_file *stl) {
-  int i;
-
-  if (stl->error) return;
-
-  for(i = 0; i < stl->stats.number_of_facets; i++) {
-    stl_check_normal_vector(stl, i, 1);
-  }
+void stl_fix_normal_values(stl_file *stl)
+{
+	for (uint32_t i = 0; i < stl->stats.number_of_facets; ++ i)
+    	stl_check_normal_vector(stl, i, 1);
 }
 
 void stl_reverse_all_facets(stl_file *stl)
 {
-  if (stl->error)
-  	return;
-
-  stl_normal normal;
-  for(int i = 0; i < stl->stats.number_of_facets; i++) {
-    stl_reverse_facet(stl, i);
-    stl_calculate_normal(normal, &stl->facet_start[i]);
-    stl_normalize_vector(normal);
-    stl->facet_start[i].normal = normal;
-  }
+	stl_normal normal;
+  	for (uint32_t i = 0; i < stl->stats.number_of_facets; ++ i) {
+    	reverse_facet(stl, i);
+    	stl_calculate_normal(normal, &stl->facet_start[i]);
+    	stl_normalize_vector(normal);
+    	stl->facet_start[i].normal = normal;
+  	}
 }
diff --git a/src/admesh/shared.cpp b/src/admesh/shared.cpp
index bc264ee96..a757d8816 100644
--- a/src/admesh/shared.cpp
+++ b/src/admesh/shared.cpp
@@ -38,15 +38,10 @@ void stl_invalidate_shared_vertices(stl_file *stl)
 
 void stl_generate_shared_vertices(stl_file *stl)
 {
-	if (stl->error)
-		return;
-
-	/* make sure this function is idempotent and does not leak memory */
-	stl_invalidate_shared_vertices(stl);
-
 	// 3 indices to vertex per face
 	stl->v_indices.assign(stl->stats.number_of_facets, v_indices_struct());
 	// Shared vertices (3D coordinates)
+	stl->v_shared.clear();
 	stl->v_shared.reserve(stl->stats.number_of_facets / 2);
 	stl->stats.shared_vertices = 0;
 
@@ -139,11 +134,8 @@ void stl_generate_shared_vertices(stl_file *stl)
 	}
 }
 
-void stl_write_off(stl_file *stl, const char *file)
+bool stl_write_off(stl_file *stl, const char *file)
 {
-	if (stl->error)
-		return;
-
 	/* Open the file */
 	FILE *fp = boost::nowide::fopen(file, "w");
 	if (fp == nullptr) {
@@ -151,8 +143,7 @@ void stl_write_off(stl_file *stl, const char *file)
 		sprintf(error_msg, "stl_write_ascii: Couldn't open %s for writing", file);
 		perror(error_msg);
 		free(error_msg);
-		stl->error = 1;
-		return;
+		return false;
 	}
 
 	fprintf(fp, "OFF\n");
@@ -162,13 +153,11 @@ void stl_write_off(stl_file *stl, const char *file)
 	for (uint32_t i = 0; i < stl->stats.number_of_facets; ++ i)
 		fprintf(fp, "\t3 %d %d %d\n", stl->v_indices[i].vertex[0], stl->v_indices[i].vertex[1], stl->v_indices[i].vertex[2]);
 	fclose(fp);
+	return true;
 }
 
-void stl_write_vrml(stl_file *stl, const char *file)
+bool stl_write_vrml(stl_file *stl, const char *file)
 {
-  	if (stl->error) 
-  		return;
-
 	/* Open the file */
   	FILE *fp = boost::nowide::fopen(file, "w");
 	if (fp == nullptr) {
@@ -176,8 +165,7 @@ void stl_write_vrml(stl_file *stl, const char *file)
 		sprintf(error_msg, "stl_write_ascii: Couldn't open %s for writing", file);
 		perror(error_msg);
 		free(error_msg);
-		stl->error = 1;
-		return;
+		return false;
 	}
 
 	fprintf(fp, "#VRML V1.0 ascii\n\n");
@@ -210,12 +198,11 @@ void stl_write_vrml(stl_file *stl, const char *file)
 	fprintf(fp, "\t}\n");
 	fprintf(fp, "}\n");
 	fclose(fp);
+	return true;
 }
 
-void stl_write_obj (stl_file *stl, const char *file)
+bool stl_write_obj(stl_file *stl, const char *file)
 {
-	if (stl->error)
-		return;
 
   	FILE *fp = boost::nowide::fopen(file, "w");
   	if (fp == nullptr) {
@@ -223,8 +210,7 @@ void stl_write_obj (stl_file *stl, const char *file)
     	sprintf(error_msg, "stl_write_ascii: Couldn't open %s for writing", file);
     	perror(error_msg);
     	free(error_msg);
-    	stl->error = 1;
-    	return;
+    	return false;
   	}
 
 	for (int i = 0; i < stl->stats.shared_vertices; ++ i)
@@ -232,4 +218,5 @@ void stl_write_obj (stl_file *stl, const char *file)
   	for (uint32_t i = 0; i < stl->stats.number_of_facets; ++ i)
     	fprintf(fp, "f %d %d %d\n", stl->v_indices[i].vertex[0]+1, stl->v_indices[i].vertex[1]+1, stl->v_indices[i].vertex[2]+1);
   	fclose(fp);
+  	return true;
 }
diff --git a/src/admesh/stl.h b/src/admesh/stl.h
index bd49ad59f..51153ede7 100644
--- a/src/admesh/stl.h
+++ b/src/admesh/stl.h
@@ -127,15 +127,9 @@ struct stl_stats {
 	int           normals_fixed;
 	int           number_of_parts;
 	int           shared_vertices;
-
-	// hash table statistics
-	int           malloced;
-	int           freed;
-	int           collisions;
 };
 
 struct stl_file {
-	FILE          			   	   *fp;
 	std::vector<stl_facet>     		facet_start;
 	std::vector<stl_neighbors> 		neighbors_start;
 	// Indexed face set
@@ -143,17 +137,15 @@ struct stl_file {
 	std::vector<stl_vertex>       	v_shared;
 	// Statistics
 	stl_stats     					stats;
-	char          					error;
 };
 
-extern void stl_open(stl_file *stl, const char *file);
-extern void stl_close(stl_file *stl);
+extern bool stl_open(stl_file *stl, const char *file);
 extern void stl_stats_out(stl_file *stl, FILE *file, char *input_file);
-extern void stl_print_neighbors(stl_file *stl, char *file);
+extern bool stl_print_neighbors(stl_file *stl, char *file);
 extern void stl_put_little_int(FILE *fp, int value_in);
 extern void stl_put_little_float(FILE *fp, float value_in);
-extern void stl_write_ascii(stl_file *stl, const char *file, const char *label);
-extern void stl_write_binary(stl_file *stl, const char *file, const char *label);
+extern bool stl_write_ascii(stl_file *stl, const char *file, const char *label);
+extern bool stl_write_binary(stl_file *stl, const char *file, const char *label);
 extern void stl_write_binary_block(stl_file *stl, FILE *fp);
 extern void stl_check_facets_exact(stl_file *stl);
 extern void stl_check_facets_nearby(stl_file *stl, float tolerance);
@@ -161,7 +153,7 @@ extern void stl_remove_unconnected_facets(stl_file *stl);
 extern void stl_write_vertex(stl_file *stl, int facet, int vertex);
 extern void stl_write_facet(stl_file *stl, char *label, int facet);
 extern void stl_write_neighbor(stl_file *stl, int facet);
-extern void stl_write_quad_object(stl_file *stl, char *file);
+extern bool stl_write_quad_object(stl_file *stl, char *file);
 extern void stl_verify_neighbors(stl_file *stl);
 extern void stl_fill_holes(stl_file *stl);
 extern void stl_fix_normal_directions(stl_file *stl);
@@ -183,34 +175,28 @@ extern void stl_get_size(stl_file *stl);
 template<typename T>
 extern void stl_transform(stl_file *stl, T *trafo3x4)
 {
-  if (stl->error)
-    return;
+	for (uint32_t i_face = 0; i_face < stl->stats.number_of_facets; ++ i_face) {
+		stl_facet &face = stl->facet_start[i_face];
+		for (int i_vertex = 0; i_vertex < 3; ++ i_vertex) {
+			stl_vertex &v_dst = face.vertex[i_vertex];
+			stl_vertex  v_src = v_dst;
+			v_dst(0) = T(trafo3x4[0] * v_src(0) + trafo3x4[1] * v_src(1) + trafo3x4[2]  * v_src(2) + trafo3x4[3]);
+			v_dst(1) = T(trafo3x4[4] * v_src(0) + trafo3x4[5] * v_src(1) + trafo3x4[6]  * v_src(2) + trafo3x4[7]);
+			v_dst(2) = T(trafo3x4[8] * v_src(0) + trafo3x4[9] * v_src(1) + trafo3x4[10] * v_src(2) + trafo3x4[11]);
+		}
+		stl_vertex &v_dst = face.normal;
+		stl_vertex  v_src = v_dst;
+		v_dst(0) = T(trafo3x4[0] * v_src(0) + trafo3x4[1] * v_src(1) + trafo3x4[2]  * v_src(2));
+		v_dst(1) = T(trafo3x4[4] * v_src(0) + trafo3x4[5] * v_src(1) + trafo3x4[6]  * v_src(2));
+		v_dst(2) = T(trafo3x4[8] * v_src(0) + trafo3x4[9] * v_src(1) + trafo3x4[10] * v_src(2));
+	}
 
-  for (uint32_t i_face = 0; i_face < stl->stats.number_of_facets; ++ i_face) {
-    stl_facet &face = stl->facet_start[i_face];
-    for (int i_vertex = 0; i_vertex < 3; ++ i_vertex) {
-      stl_vertex &v_dst = face.vertex[i_vertex];
-      stl_vertex  v_src = v_dst;
-      v_dst(0) = T(trafo3x4[0] * v_src(0) + trafo3x4[1] * v_src(1) + trafo3x4[2]  * v_src(2) + trafo3x4[3]);
-      v_dst(1) = T(trafo3x4[4] * v_src(0) + trafo3x4[5] * v_src(1) + trafo3x4[6]  * v_src(2) + trafo3x4[7]);
-      v_dst(2) = T(trafo3x4[8] * v_src(0) + trafo3x4[9] * v_src(1) + trafo3x4[10] * v_src(2) + trafo3x4[11]);
-    }
-    stl_vertex &v_dst = face.normal;
-    stl_vertex  v_src = v_dst;
-    v_dst(0) = T(trafo3x4[0] * v_src(0) + trafo3x4[1] * v_src(1) + trafo3x4[2]  * v_src(2));
-    v_dst(1) = T(trafo3x4[4] * v_src(0) + trafo3x4[5] * v_src(1) + trafo3x4[6]  * v_src(2));
-    v_dst(2) = T(trafo3x4[8] * v_src(0) + trafo3x4[9] * v_src(1) + trafo3x4[10] * v_src(2));
-  }
-
-  stl_get_size(stl);
+	stl_get_size(stl);
 }
 
 template<typename T>
 inline void stl_transform(stl_file *stl, const Eigen::Transform<T, 3, Eigen::Affine, Eigen::DontAlign>& t)
 {
-	if (stl->error)
-		return;
-
 	const Eigen::Matrix<double, 3, 3, Eigen::DontAlign> r = t.matrix().template block<3, 3>(0, 0);
 	for (size_t i = 0; i < stl->stats.number_of_facets; ++i) {
 		stl_facet &f = stl->facet_start[i];
@@ -225,9 +211,6 @@ inline void stl_transform(stl_file *stl, const Eigen::Transform<T, 3, Eigen::Aff
 template<typename T>
 inline void stl_transform(stl_file *stl, const Eigen::Matrix<T, 3, 3, Eigen::DontAlign>& m)
 {
-	if (stl->error)
-		return;
-
 	for (size_t i = 0; i < stl->stats.number_of_facets; ++i) {
 		stl_facet &f = stl->facet_start[i];
 		for (size_t j = 0; j < 3; ++j)
@@ -238,13 +221,12 @@ inline void stl_transform(stl_file *stl, const Eigen::Matrix<T, 3, 3, Eigen::Don
 	stl_get_size(stl);
 }
 
-extern void stl_open_merge(stl_file *stl, char *file);
 extern void stl_invalidate_shared_vertices(stl_file *stl);
 extern void stl_generate_shared_vertices(stl_file *stl);
-extern void stl_write_obj(stl_file *stl, const char *file);
-extern void stl_write_off(stl_file *stl, const char *file);
-extern void stl_write_dxf(stl_file *stl, const char *file, char *label);
-extern void stl_write_vrml(stl_file *stl, const char *file);
+extern bool stl_write_obj(stl_file *stl, const char *file);
+extern bool stl_write_off(stl_file *stl, const char *file);
+extern bool stl_write_dxf(stl_file *stl, const char *file, char *label);
+extern bool stl_write_vrml(stl_file *stl, const char *file);
 inline void stl_calculate_normal(stl_normal &normal, stl_facet *facet) {
   normal = (facet->vertex[1] - facet->vertex[0]).cross(facet->vertex[2] - facet->vertex[0]);
 }
@@ -263,17 +245,13 @@ extern void stl_calculate_volume(stl_file *stl);
 
 extern void stl_repair(stl_file *stl, int fixall_flag, int exact_flag, int tolerance_flag, float tolerance, int increment_flag, float increment, int nearby_flag, int iterations, int remove_unconnected_flag, int fill_holes_flag, int normal_directions_flag, int normal_values_flag, int reverse_all_flag, int verbose_flag);
 
-extern void stl_initialize(stl_file *stl);
-extern void stl_count_facets(stl_file *stl, const char *file);
+extern void stl_reset(stl_file *stl);
 extern void stl_allocate(stl_file *stl);
 extern void stl_read(stl_file *stl, int first_facet, bool first);
 extern void stl_facet_stats(stl_file *stl, stl_facet facet, bool &first);
 extern void stl_reallocate(stl_file *stl);
 extern void stl_add_facet(stl_file *stl, const stl_facet *new_facet);
 
-extern void stl_clear_error(stl_file *stl);
-extern int stl_get_error(stl_file *stl);
-extern void stl_exit_on_error(stl_file *stl);
 // Validate the mesh, assert on error.
 extern bool stl_validate(stl_file *stl);
 
diff --git a/src/admesh/stl_io.cpp b/src/admesh/stl_io.cpp
index 1e2e1479e..8f809d379 100644
--- a/src/admesh/stl_io.cpp
+++ b/src/admesh/stl_io.cpp
@@ -33,10 +33,8 @@
 #define SEEK_END 2
 #endif
 
-void
-stl_stats_out(stl_file *stl, FILE *file, char *input_file) {
-  if (stl->error) return;
-
+void stl_stats_out(stl_file *stl, FILE *file, char *input_file)
+{
   /* this is here for Slic3r, without our config.h
      it won't use this part of the code anyway */
 #ifndef VERSION
@@ -107,12 +105,10 @@ Backwards edges       : %5d\n", stl->stats.backwards_edges);
 Normals fixed         : %5d\n", stl->stats.normals_fixed);
 }
 
-void
-stl_write_ascii(stl_file *stl, const char *file, const char *label) {
+bool stl_write_ascii(stl_file *stl, const char *file, const char *label)
+{
   char      *error_msg;
 
-  if (stl->error) return;
-
   /* Open the file */
   FILE *fp = boost::nowide::fopen(file, "w");
   if(fp == NULL) {
@@ -122,8 +118,7 @@ stl_write_ascii(stl_file *stl, const char *file, const char *label) {
             file);
     perror(error_msg);
     free(error_msg);
-    stl->error = 1;
-    return;
+    return false;
   }
 
   fprintf(fp, "solid  %s\n", label);
@@ -149,15 +144,14 @@ stl_write_ascii(stl_file *stl, const char *file, const char *label) {
   fprintf(fp, "endsolid  %s\n", label);
 
   fclose(fp);
+  return true;
 }
 
-void
-stl_print_neighbors(stl_file *stl, char *file) {
+bool stl_print_neighbors(stl_file *stl, char *file)
+{
   FILE *fp;
   char *error_msg;
 
-  if (stl->error) return;
-
   /* Open the file */
   fp = boost::nowide::fopen(file, "w");
   if(fp == NULL) {
@@ -167,8 +161,7 @@ stl_print_neighbors(stl_file *stl, char *file) {
             file);
     perror(error_msg);
     free(error_msg);
-    stl->error = 1;
-    return;
+    return false;
   }
 
   for (uint32_t i = 0; i < stl->stats.number_of_facets; i++) {
@@ -182,6 +175,7 @@ stl_print_neighbors(stl_file *stl, char *file) {
             (int)stl->neighbors_start[i].which_vertex_not[2]);
   }
   fclose(fp);
+  return true;
 }
 
 #ifndef BOOST_LITTLE_ENDIAN
@@ -195,13 +189,11 @@ void stl_internal_reverse_quads(char *buf, size_t cnt)
 }
 #endif
 
-void
-stl_write_binary(stl_file *stl, const char *file, const char *label) {
+bool stl_write_binary(stl_file *stl, const char *file, const char *label)
+{
   FILE      *fp;
   char      *error_msg;
 
-  if (stl->error) return;
-
   /* Open the file */
   fp = boost::nowide::fopen(file, "wb");
   if(fp == NULL) {
@@ -211,8 +203,7 @@ stl_write_binary(stl_file *stl, const char *file, const char *label) {
             file);
     perror(error_msg);
     free(error_msg);
-    stl->error = 1;
-    return;
+    return false;
   }
 
   fprintf(fp, "%s", label);
@@ -237,40 +228,38 @@ stl_write_binary(stl_file *stl, const char *file, const char *label) {
   }
 #endif /* BOOST_LITTLE_ENDIAN */
   fclose(fp);
+  return true;
 }
 
-void
-stl_write_vertex(stl_file *stl, int facet, int vertex) {
-  if (stl->error) return;
-  printf("  vertex %d/%d % .8E % .8E % .8E\n", vertex, facet,
+void stl_write_vertex(stl_file *stl, int facet, int vertex)
+{
+  	printf("  vertex %d/%d % .8E % .8E % .8E\n", vertex, facet,
          stl->facet_start[facet].vertex[vertex](0),
          stl->facet_start[facet].vertex[vertex](1),
          stl->facet_start[facet].vertex[vertex](2));
 }
 
-void
-stl_write_facet(stl_file *stl, char *label, int facet) {
-  if (stl->error) return;
-  printf("facet (%d)/ %s\n", facet, label);
-  stl_write_vertex(stl, facet, 0);
-  stl_write_vertex(stl, facet, 1);
-  stl_write_vertex(stl, facet, 2);
+void stl_write_facet(stl_file *stl, char *label, int facet)
+{
+	printf("facet (%d)/ %s\n", facet, label);
+	stl_write_vertex(stl, facet, 0);
+	stl_write_vertex(stl, facet, 1);
+	stl_write_vertex(stl, facet, 2);
 }
 
-void
-stl_write_neighbor(stl_file *stl, int facet) {
-  if (stl->error) return;
-  printf("Neighbors %d: %d, %d, %d ;  %d, %d, %d\n", facet,
-         stl->neighbors_start[facet].neighbor[0],
-         stl->neighbors_start[facet].neighbor[1],
-         stl->neighbors_start[facet].neighbor[2],
-         stl->neighbors_start[facet].which_vertex_not[0],
-         stl->neighbors_start[facet].which_vertex_not[1],
-         stl->neighbors_start[facet].which_vertex_not[2]);
+void stl_write_neighbor(stl_file *stl, int facet)
+{
+	printf("Neighbors %d: %d, %d, %d ;  %d, %d, %d\n", facet,
+		stl->neighbors_start[facet].neighbor[0],
+		stl->neighbors_start[facet].neighbor[1],
+		stl->neighbors_start[facet].neighbor[2],
+		stl->neighbors_start[facet].which_vertex_not[0],
+		stl->neighbors_start[facet].which_vertex_not[1],
+		stl->neighbors_start[facet].which_vertex_not[2]);
 }
 
-void
-stl_write_quad_object(stl_file *stl, char *file) {
+bool stl_write_quad_object(stl_file *stl, char *file)
+{
   FILE      *fp;
   char      *error_msg;
   stl_vertex connect_color = stl_vertex::Zero();
@@ -279,8 +268,6 @@ stl_write_quad_object(stl_file *stl, char *file) {
   stl_vertex uncon_3_color = stl_vertex::Zero();
   stl_vertex color;
 
-  if (stl->error) return;
-
   /* Open the file */
   fp = boost::nowide::fopen(file, "w");
   if(fp == NULL) {
@@ -290,8 +277,7 @@ stl_write_quad_object(stl_file *stl, char *file) {
             file);
     perror(error_msg);
     free(error_msg);
-    stl->error = 1;
-    return;
+    return false;
   }
 
   fprintf(fp, "CQUAD\n");
@@ -326,15 +312,14 @@ stl_write_quad_object(stl_file *stl, char *file) {
             stl->facet_start[i].vertex[2](2), color(0), color(1), color(2));
   }
   fclose(fp);
+  return true;
 }
 
-void stl_write_dxf(stl_file *stl, const char *file, char *label) 
+bool stl_write_dxf(stl_file *stl, const char *file, char *label) 
 {
   FILE      *fp;
   char      *error_msg;
 
-  if (stl->error) return;
-
   /* Open the file */
   fp = boost::nowide::fopen(file, "w");
   if(fp == NULL) {
@@ -344,8 +329,7 @@ void stl_write_dxf(stl_file *stl, const char *file, char *label)
             file);
     perror(error_msg);
     free(error_msg);
-    stl->error = 1;
-    return;
+    return false;
   }
 
   fprintf(fp, "999\n%s\n", label);
@@ -375,22 +359,5 @@ void stl_write_dxf(stl_file *stl, const char *file, char *label)
   fprintf(fp, "0\nENDSEC\n0\nEOF\n");
 
   fclose(fp);
-}
-
-void
-stl_clear_error(stl_file *stl) {
-  stl->error = 0;
-}
-
-void
-stl_exit_on_error(stl_file *stl) {
-  if (!stl->error) return;
-  stl->error = 0;
-  stl_close(stl);
-  exit(1);
-}
-
-int
-stl_get_error(stl_file *stl) {
-  return stl->error;
+  return true;
 }
diff --git a/src/admesh/stlinit.cpp b/src/admesh/stlinit.cpp
index b7ba21b77..088842d51 100644
--- a/src/admesh/stlinit.cpp
+++ b/src/admesh/stlinit.cpp
@@ -35,42 +35,8 @@
 #error "SEEK_SET not defined"
 #endif
 
-void stl_open(stl_file *stl, const char *file)
+static FILE* stl_open_count_facets(stl_file *stl, const char *file) 
 {
-	stl_initialize(stl);
-	stl_count_facets(stl, file);
-	stl_allocate(stl);
-	stl_read(stl, 0, true);
-	if (stl->fp != nullptr) {
-	  	fclose(stl->fp);
-	  	stl->fp = nullptr;
-	}
-}
-
-void stl_initialize(stl_file *stl)
-{
-	stl->fp = nullptr;
-	stl->error = 0;
-	stl->facet_start.clear();
-	stl->neighbors_start.clear();
-	stl->v_indices.clear();
-	stl->v_shared.clear();
-  	memset(&stl->stats, 0, sizeof(stl_stats));
-  	stl->stats.volume = -1.0;
-}
-
-void stl_close(stl_file *stl)
-{
-	assert(stl->fp == nullptr);
-	stl_initialize(stl);
-}
-
-#ifndef BOOST_LITTLE_ENDIAN
-extern void stl_internal_reverse_quads(char *buf, size_t cnt);
-#endif /* BOOST_LITTLE_ENDIAN */
-
-void
-stl_count_facets(stl_file *stl, const char *file) {
   long           file_size;
   uint32_t       header_num_facets;
   uint32_t       num_facets;
@@ -80,30 +46,27 @@ stl_count_facets(stl_file *stl, const char *file) {
   int            num_lines = 1;
   char           *error_msg;
 
-  if (stl->error) return;
-
   /* Open the file in binary mode first */
-  stl->fp = boost::nowide::fopen(file, "rb");
-  if(stl->fp == NULL) {
+  FILE *fp = boost::nowide::fopen(file, "rb");
+  if (fp == nullptr) {
     error_msg = (char*)
                 malloc(81 + strlen(file)); /* Allow 80 chars+file size for message */
     sprintf(error_msg, "stl_initialize: Couldn't open %s for reading",
             file);
     perror(error_msg);
     free(error_msg);
-    stl->error = 1;
-    return;
+    return nullptr;
   }
   /* Find size of file */
-  fseek(stl->fp, 0, SEEK_END);
-  file_size = ftell(stl->fp);
+  fseek(fp, 0, SEEK_END);
+  file_size = ftell(fp);
 
   /* Check for binary or ASCII file */
-  fseek(stl->fp, HEADER_SIZE, SEEK_SET);
-  if (!fread(chtest, sizeof(chtest), 1, stl->fp)) {
+  fseek(fp, HEADER_SIZE, SEEK_SET);
+  if (!fread(chtest, sizeof(chtest), 1, fp)) {
     perror("The input is an empty file");
-    stl->error = 1;
-    return;
+    fclose(fp);
+    return nullptr;
   }
   stl->stats.type = ascii;
   for(s = 0; s < sizeof(chtest); s++) {
@@ -112,7 +75,7 @@ stl_count_facets(stl_file *stl, const char *file) {
       break;
     }
   }
-  rewind(stl->fp);
+  rewind(fp);
 
   /* Get the header and the number of facets in the .STL file */
   /* If the .STL file is binary, then do the following */
@@ -121,18 +84,18 @@ stl_count_facets(stl_file *stl, const char *file) {
     if(((file_size - HEADER_SIZE) % SIZEOF_STL_FACET != 0)
         || (file_size < STL_MIN_FILE_SIZE)) {
       fprintf(stderr, "The file %s has the wrong size.\n", file);
-      stl->error = 1;
-      return;
+      fclose(fp);
+      return nullptr;
     }
     num_facets = (file_size - HEADER_SIZE) / SIZEOF_STL_FACET;
 
     /* Read the header */
-    if (fread(stl->stats.header, LABEL_SIZE, 1, stl->fp) > 79) {
+    if (fread(stl->stats.header, LABEL_SIZE, 1, fp) > 79) {
       stl->stats.header[80] = '\0';
     }
 
     /* Read the int following the header.  This should contain # of facets */
-    bool header_num_faces_read = fread(&header_num_facets, sizeof(uint32_t), 1, stl->fp) != 0;
+    bool header_num_faces_read = fread(&header_num_facets, sizeof(uint32_t), 1, fp) != 0;
 #ifndef BOOST_LITTLE_ENDIAN
     // Convert from little endian to big endian.
     stl_internal_reverse_quads((char*)&header_num_facets, 4);
@@ -147,23 +110,23 @@ stl_count_facets(stl_file *stl, const char *file) {
     /* Reopen the file in text mode (for getting correct newlines on Windows) */
     // fix to silence a warning about unused return value.
     // obviously if it fails we have problems....
-    stl->fp = boost::nowide::freopen(file, "r", stl->fp);
+    fp = boost::nowide::freopen(file, "r", fp);
 
     // do another null check to be safe
-    if(stl->fp == NULL) {
+    if(fp == nullptr) {
       error_msg = (char*)
         malloc(81 + strlen(file)); /* Allow 80 chars+file size for message */
       sprintf(error_msg, "stl_initialize: Couldn't open %s for reading",
           file);
       perror(error_msg);
       free(error_msg);
-      stl->error = 1;
-      return;
+      fclose(fp);
+      return nullptr;
     }
     
     /* Find the number of facets */
     char linebuf[100];
-    while (fgets(linebuf, 100, stl->fp) != NULL) {
+    while (fgets(linebuf, 100, fp) != nullptr) {
         /* don't count short lines */
         if (strlen(linebuf) <= 4) continue;
         
@@ -173,11 +136,11 @@ stl_count_facets(stl_file *stl, const char *file) {
         ++num_lines;
     }
     
-    rewind(stl->fp);
+    rewind(fp);
     
     /* Get the header */
     for(i = 0;
-        (i < 80) && (stl->stats.header[i] = getc(stl->fp)) != '\n'; i++);
+        (i < 80) && (stl->stats.header[i] = getc(fp)) != '\n'; i++);
     stl->stats.header[i] = '\0'; /* Lose the '\n' */
     stl->stats.header[80] = '\0';
 
@@ -185,84 +148,20 @@ stl_count_facets(stl_file *stl, const char *file) {
   }
   stl->stats.number_of_facets += num_facets;
   stl->stats.original_num_facets = stl->stats.number_of_facets;
+  return fp;
 }
 
-void stl_allocate(stl_file *stl) 
-{
-	if (stl->error) 
-		return;
-  	//  Allocate memory for the entire .STL file.
-  	stl->facet_start.assign(stl->stats.number_of_facets, stl_facet());
-  	// Allocate memory for the neighbors list.
-  	stl->neighbors_start.assign(stl->stats.number_of_facets, stl_neighbors());
-}
-
-void
-stl_open_merge(stl_file *stl, char *file_to_merge) {
-  int num_facets_so_far;
-  stl_type origStlType;
-  FILE *origFp;
-  stl_file stl_to_merge;
-
-  if (stl->error) return;
-
-  /* Record how many facets we have so far from the first file.  We will start putting
-     facets in the next position.  Since we're 0-indexed, it'l be the same position. */
-  num_facets_so_far = stl->stats.number_of_facets;
-
-  /* Record the file type we started with: */
-  origStlType=stl->stats.type;
-  /* Record the file pointer too: */
-  origFp=stl->fp;
-
-  /* Initialize the sturucture with zero stats, header info and sizes: */
-  stl_initialize(&stl_to_merge);
-  stl_count_facets(&stl_to_merge, file_to_merge);
-
-  /* Copy what we need to into stl so that we can read the file_to_merge directly into it
-     using stl_read:  Save the rest of the valuable info: */
-  stl->stats.type=stl_to_merge.stats.type;
-  stl->fp=stl_to_merge.fp;
-
-  /* Add the number of facets we already have in stl with what we we found in stl_to_merge but
-     haven't read yet. */
-  stl->stats.number_of_facets=num_facets_so_far+stl_to_merge.stats.number_of_facets;
-
-  /* Allocate enough room for stl->stats.number_of_facets facets and neighbors: */
-  stl_reallocate(stl);
-
-  /* Read the file to merge directly into stl, adding it to what we have already.
-     Start at num_facets_so_far, the index to the first unused facet.  Also say
-     that this isn't our first time so we should augment stats like min and max
-     instead of erasing them. */
-  stl_read(stl, num_facets_so_far, false);
-
-  /* Restore the stl information we overwrote (for stl_read) so that it still accurately
-     reflects the subject part: */
-  stl->stats.type=origStlType;
-  stl->fp=origFp;
-}
-
-void stl_reallocate(stl_file *stl) 
-{
-  	if (stl->error) 
-  		return;
-	stl->facet_start.resize(stl->stats.number_of_facets);
-	stl->neighbors_start.resize(stl->stats.number_of_facets);
-}
-
-/* Reads the contents of the file pointed to by stl->fp into the stl structure,
+/* Reads the contents of the file pointed to by fp into the stl structure,
    starting at facet first_facet.  The second argument says if it's our first
    time running this for the stl and therefore we should reset our max and min stats. */
-void stl_read(stl_file *stl, int first_facet, bool first) {
+static bool stl_read(stl_file *stl, FILE *fp, int first_facet, bool first)
+{
   stl_facet facet;
 
-  if (stl->error) return;
-
   if(stl->stats.type == binary) {
-    fseek(stl->fp, HEADER_SIZE, SEEK_SET);
+    fseek(fp, HEADER_SIZE, SEEK_SET);
   } else {
-    rewind(stl->fp);
+    rewind(fp);
   }
 
   char normal_buf[3][32];
@@ -271,10 +170,8 @@ void stl_read(stl_file *stl, int first_facet, bool first) {
       /* Read a single facet from a binary .STL file */
     {
       /* we assume little-endian architecture! */
-      if (fread(&facet, 1, SIZEOF_STL_FACET, stl->fp) != SIZEOF_STL_FACET) {
-        stl->error = 1;
-        return;
-      }
+      if (fread(&facet, 1, SIZEOF_STL_FACET, fp) != SIZEOF_STL_FACET)
+      	return false;
 #ifndef BOOST_LITTLE_ENDIAN
       // Convert the loaded little endian data to big endian.
       stl_internal_reverse_quads((char*)&facet, 48);
@@ -284,27 +181,26 @@ void stl_read(stl_file *stl, int first_facet, bool first) {
     {
       // skip solid/endsolid
       // (in this order, otherwise it won't work when they are paired in the middle of a file)
-      fscanf(stl->fp, "endsolid%*[^\n]\n");
-      fscanf(stl->fp, "solid%*[^\n]\n");  // name might contain spaces so %*s doesn't work and it also can be empty (just "solid")
+      fscanf(fp, "endsolid%*[^\n]\n");
+      fscanf(fp, "solid%*[^\n]\n");  // name might contain spaces so %*s doesn't work and it also can be empty (just "solid")
       // Leading space in the fscanf format skips all leading white spaces including numerous new lines and tabs.
-      int res_normal     = fscanf(stl->fp, " facet normal %31s %31s %31s", normal_buf[0], normal_buf[1], normal_buf[2]);
+      int res_normal     = fscanf(fp, " facet normal %31s %31s %31s", normal_buf[0], normal_buf[1], normal_buf[2]);
       assert(res_normal == 3);
-      int res_outer_loop = fscanf(stl->fp, " outer loop");
+      int res_outer_loop = fscanf(fp, " outer loop");
       assert(res_outer_loop == 0);
-      int res_vertex1    = fscanf(stl->fp, " vertex %f %f %f", &facet.vertex[0](0), &facet.vertex[0](1), &facet.vertex[0](2));
+      int res_vertex1    = fscanf(fp, " vertex %f %f %f", &facet.vertex[0](0), &facet.vertex[0](1), &facet.vertex[0](2));
       assert(res_vertex1 == 3);
-      int res_vertex2    = fscanf(stl->fp, " vertex %f %f %f", &facet.vertex[1](0), &facet.vertex[1](1), &facet.vertex[1](2));
+      int res_vertex2    = fscanf(fp, " vertex %f %f %f", &facet.vertex[1](0), &facet.vertex[1](1), &facet.vertex[1](2));
       assert(res_vertex2 == 3);
-      int res_vertex3    = fscanf(stl->fp, " vertex %f %f %f", &facet.vertex[2](0), &facet.vertex[2](1), &facet.vertex[2](2));
+      int res_vertex3    = fscanf(fp, " vertex %f %f %f", &facet.vertex[2](0), &facet.vertex[2](1), &facet.vertex[2](2));
       assert(res_vertex3 == 3);
-      int res_endloop    = fscanf(stl->fp, " endloop");
+      int res_endloop    = fscanf(fp, " endloop");
       assert(res_endloop == 0);
       // There is a leading and trailing white space around endfacet to eat up all leading and trailing white spaces including numerous tabs and new lines.
-      int res_endfacet   = fscanf(stl->fp, " endfacet ");
+      int res_endfacet   = fscanf(fp, " endfacet ");
       if (res_normal != 3 || res_outer_loop != 0 || res_vertex1 != 3 || res_vertex2 != 3 || res_vertex3 != 3 || res_endloop != 0 || res_endfacet != 0) {
         perror("Something is syntactically very wrong with this ASCII STL!");
-        stl->error = 1;
-        return;
+        return false;
       }
 
       // The facet normal has been parsed as a single string as to workaround for not a numbers in the normal definition.
@@ -338,13 +234,51 @@ void stl_read(stl_file *stl, int first_facet, bool first) {
   }
   stl->stats.size = stl->stats.max - stl->stats.min;
   stl->stats.bounding_diameter = stl->stats.size.norm();
+  return true;
+}
+
+bool stl_open(stl_file *stl, const char *file)
+{
+	stl_reset(stl);
+	FILE *fp = stl_open_count_facets(stl, file);
+	if (fp == nullptr)
+		return false;
+	stl_allocate(stl);
+	bool result = stl_read(stl, fp, 0, true);
+  	fclose(fp);
+  	return result;
+}
+
+void stl_reset(stl_file *stl)
+{
+	stl->facet_start.clear();
+	stl->neighbors_start.clear();
+	stl->v_indices.clear();
+	stl->v_shared.clear();
+  	memset(&stl->stats, 0, sizeof(stl_stats));
+  	stl->stats.volume = -1.0;
+}
+
+#ifndef BOOST_LITTLE_ENDIAN
+extern void stl_internal_reverse_quads(char *buf, size_t cnt);
+#endif /* BOOST_LITTLE_ENDIAN */
+
+void stl_allocate(stl_file *stl) 
+{
+  	//  Allocate memory for the entire .STL file.
+  	stl->facet_start.assign(stl->stats.number_of_facets, stl_facet());
+  	// Allocate memory for the neighbors list.
+  	stl->neighbors_start.assign(stl->stats.number_of_facets, stl_neighbors());
+}
+
+void stl_reallocate(stl_file *stl) 
+{
+	stl->facet_start.resize(stl->stats.number_of_facets);
+	stl->neighbors_start.resize(stl->stats.number_of_facets);
 }
 
 void stl_facet_stats(stl_file *stl, stl_facet facet, bool &first)
 {
-  if (stl->error)
-  	return;
-
   // While we are going through all of the facets, let's find the
   // maximum and minimum values for x, y, and z
 
diff --git a/src/admesh/util.cpp b/src/admesh/util.cpp
index 91293d048..db05cbc09 100644
--- a/src/admesh/util.cpp
+++ b/src/admesh/util.cpp
@@ -34,9 +34,6 @@ static float get_volume(stl_file *stl);
 
 void stl_verify_neighbors(stl_file *stl)
 {
-	if (stl->error)
-		return;
-
 	stl->stats.backwards_edges = 0;
 
 	for (uint32_t i = 0; i < stl->stats.number_of_facets; ++ i) {
@@ -69,9 +66,6 @@ void stl_verify_neighbors(stl_file *stl)
 
 void stl_translate(stl_file *stl, float x, float y, float z)
 {
-  if (stl->error)
-  	return;
-
   stl_vertex new_min(x, y, z);
   stl_vertex shift = new_min - stl->stats.min;
   for (int i = 0; i < stl->stats.number_of_facets; ++ i)
@@ -85,9 +79,6 @@ void stl_translate(stl_file *stl, float x, float y, float z)
 /* Translates the stl by x,y,z, relatively from wherever it is currently */
 void stl_translate_relative(stl_file *stl, float x, float y, float z)
 {
-  if (stl->error)
-  	return;
-
   stl_vertex shift(x, y, z);
   for (int i = 0; i < stl->stats.number_of_facets; ++ i)
     for (int j = 0; j < 3; ++ j)
@@ -99,9 +90,6 @@ void stl_translate_relative(stl_file *stl, float x, float y, float z)
 
 void stl_scale_versor(stl_file *stl, const stl_vertex &versor)
 {
-  if (stl->error)
-  	return;
-
   // Scale extents.
   auto s = versor.array();
   stl->stats.min.array() *= s;
@@ -120,9 +108,6 @@ void stl_scale_versor(stl_file *stl, const stl_vertex &versor)
 
 static void calculate_normals(stl_file *stl) 
 {
-  if (stl->error)
-  	return;
-
   stl_normal normal;
   for(uint32_t i = 0; i < stl->stats.number_of_facets; i++) {
     stl_calculate_normal(normal, &stl->facet_start[i]);
@@ -139,8 +124,6 @@ stl_rotate_x(stl_file *stl, float angle) {
   double c = cos(radian_angle);
   double s = sin(radian_angle);
 
-  if (stl->error) return;
-
   for(i = 0; i < stl->stats.number_of_facets; i++) {
     for(j = 0; j < 3; j++) {
       stl_rotate(&stl->facet_start[i].vertex[j](1),
@@ -159,8 +142,6 @@ stl_rotate_y(stl_file *stl, float angle) {
   double c = cos(radian_angle);
   double s = sin(radian_angle);
 
-  if (stl->error) return;
-
   for(i = 0; i < stl->stats.number_of_facets; i++) {
     for(j = 0; j < 3; j++) {
       stl_rotate(&stl->facet_start[i].vertex[j](2),
@@ -179,8 +160,6 @@ stl_rotate_z(stl_file *stl, float angle) {
   double c = cos(radian_angle);
   double s = sin(radian_angle);
 
-  if (stl->error) return;
-
   for(i = 0; i < stl->stats.number_of_facets; i++) {
     for(j = 0; j < 3; j++) {
       stl_rotate(&stl->facet_start[i].vertex[j](0),
@@ -203,7 +182,7 @@ stl_rotate(float *x, float *y, const double c, const double s) {
 
 void stl_get_size(stl_file *stl)
 {
-  if (stl->error || stl->stats.number_of_facets == 0)
+  if (stl->stats.number_of_facets == 0)
   	return;
   stl->stats.min = stl->facet_start[0].vertex[0];
   stl->stats.max = stl->stats.min;
@@ -220,9 +199,6 @@ void stl_get_size(stl_file *stl)
 
 void stl_mirror_xy(stl_file *stl)
 {
-  if (stl->error) 
-  	return;
-
   for(int i = 0; i < stl->stats.number_of_facets; i++) {
     for(int j = 0; j < 3; j++) {
       stl->facet_start[i].vertex[j](2) *= -1.0;
@@ -239,8 +215,6 @@ void stl_mirror_xy(stl_file *stl)
 
 void stl_mirror_yz(stl_file *stl)
 {
-  if (stl->error) return;
-
   for (int i = 0; i < stl->stats.number_of_facets; i++) {
     for (int j = 0; j < 3; j++) {
       stl->facet_start[i].vertex[j](0) *= -1.0;
@@ -257,9 +231,6 @@ void stl_mirror_yz(stl_file *stl)
 
 void stl_mirror_xz(stl_file *stl)
 {
-	if (stl->error)
-		return;
-
 	for (uint32_t i = 0; i < stl->stats.number_of_facets; ++ i)
 		for (int j = 0; j < 3; ++ j)
 			stl->facet_start[i].vertex[j](1) *= -1.0;
@@ -274,9 +245,6 @@ void stl_mirror_xz(stl_file *stl)
 
 static float get_volume(stl_file *stl)
 {
-  if (stl->error)
-  	return 0;
-
   // Choose a point, any point as the reference.
   stl_vertex p0 = stl->facet_start[0].vertex[0];
   float volume = 0.f;
@@ -291,7 +259,6 @@ static float get_volume(stl_file *stl)
 
 void stl_calculate_volume(stl_file *stl)
 {
-  if (stl->error) return;
   stl->stats.volume = get_volume(stl);
   if(stl->stats.volume < 0.0) {
     stl_reverse_all_facets(stl);
@@ -346,8 +313,6 @@ void stl_repair(stl_file *stl,
   int i;
   int last_edges_fixed = 0;
 
-  if (stl->error) return;
-
   if(exact_flag || fixall_flag || nearby_flag || remove_unconnected_flag
       || fill_holes_flag || normal_directions_flag) {
     if (verbose_flag)
@@ -453,8 +418,6 @@ All facets connected.  No further nearby check necessary.\n");
 // Check validity of the mesh, assert on error.
 bool stl_validate(stl_file *stl)
 {
-	assert(! stl->error);
-	assert(stl->fp == nullptr);
 	assert(! stl->facet_start.empty());
 	assert(stl->facet_start.size() == stl->stats.number_of_facets);
 	assert(stl->neighbors_start.size() == stl->stats.number_of_facets);
diff --git a/src/libslic3r/Format/PRUS.cpp b/src/libslic3r/Format/PRUS.cpp
index d983b1098..03ea71a83 100644
--- a/src/libslic3r/Format/PRUS.cpp
+++ b/src/libslic3r/Format/PRUS.cpp
@@ -161,7 +161,6 @@ static void extract_model_from_archive(
         else {
             // Header has been extracted. Now read the faces.
             stl_file &stl = mesh.stl;
-            stl.error = 0;
             stl.stats.type = inmemory;
             stl.stats.number_of_facets = header.nTriangles;
             stl.stats.original_num_facets = header.nTriangles;
diff --git a/src/libslic3r/Format/STL.cpp b/src/libslic3r/Format/STL.cpp
index b00623d1d..932906fe0 100644
--- a/src/libslic3r/Format/STL.cpp
+++ b/src/libslic3r/Format/STL.cpp
@@ -17,8 +17,7 @@ namespace Slic3r {
 bool load_stl(const char *path, Model *model, const char *object_name_in)
 {
     TriangleMesh mesh;
-    mesh.ReadSTLFile(path);
-    if (mesh.stl.error) {
+    if (! mesh.ReadSTLFile(path)) {
 //    die "Failed to open $file\n" if !-e $path;
         return false;
     }
diff --git a/src/libslic3r/TriangleMesh.cpp b/src/libslic3r/TriangleMesh.cpp
index ad12047d2..27163eb57 100644
--- a/src/libslic3r/TriangleMesh.cpp
+++ b/src/libslic3r/TriangleMesh.cpp
@@ -45,7 +45,7 @@ namespace Slic3r {
 TriangleMesh::TriangleMesh(const Pointf3s &points, const std::vector<Vec3crd>& facets)
     : repaired(false)
 {
-    stl_initialize(&this->stl);
+    stl_reset(&this->stl);
     stl_file &stl = this->stl;
     stl.stats.type = inmemory;
 
@@ -74,7 +74,7 @@ TriangleMesh::TriangleMesh(const Pointf3s &points, const std::vector<Vec3crd>& f
 
 TriangleMesh& TriangleMesh::operator=(const TriangleMesh &other)
 {
-    stl_close(&this->stl);
+    stl_reset(&this->stl);
     this->stl = other.stl;
 	this->repaired = other.repaired;
     return *this;
@@ -426,7 +426,6 @@ TriangleMeshPtrs TriangleMesh::split() const
         mesh->stl.stats.type = inmemory;
         mesh->stl.stats.number_of_facets = (uint32_t)facets.size();
         mesh->stl.stats.original_num_facets = mesh->stl.stats.number_of_facets;
-        stl_clear_error(&mesh->stl);
         stl_allocate(&mesh->stl);
 
         // Assign the facets to the new mesh.
diff --git a/src/libslic3r/TriangleMesh.hpp b/src/libslic3r/TriangleMesh.hpp
index 4de1f5989..c16f4a664 100644
--- a/src/libslic3r/TriangleMesh.hpp
+++ b/src/libslic3r/TriangleMesh.hpp
@@ -21,18 +21,18 @@ typedef std::vector<TriangleMesh*> TriangleMeshPtrs;
 class TriangleMesh
 {
 public:
-    TriangleMesh() : repaired(false) { stl_initialize(&this->stl); }
+    TriangleMesh() : repaired(false) { stl_reset(&this->stl); }
     TriangleMesh(const Pointf3s &points, const std::vector<Vec3crd> &facets);
-    TriangleMesh(const TriangleMesh &other) : repaired(false) { stl_initialize(&this->stl); *this = other; }
-    TriangleMesh(TriangleMesh &&other) : repaired(false) { stl_initialize(&this->stl); this->swap(other); }
+    TriangleMesh(const TriangleMesh &other) : repaired(false) { stl_reset(&this->stl); *this = other; }
+    TriangleMesh(TriangleMesh &&other) : repaired(false) { stl_reset(&this->stl); this->swap(other); }
     ~TriangleMesh() { clear(); }
     TriangleMesh& operator=(const TriangleMesh &other);
     TriangleMesh& operator=(TriangleMesh &&other) { this->swap(other); return *this; }
-    void clear() { stl_close(&this->stl); this->repaired = false; }
+    void clear() { stl_reset(&this->stl); this->repaired = false; }
     void swap(TriangleMesh &other) { std::swap(this->stl, other.stl); std::swap(this->repaired, other.repaired); }
-    void ReadSTLFile(const char* input_file) { stl_open(&stl, input_file); }
-    void write_ascii(const char* output_file) { stl_write_ascii(&this->stl, output_file, ""); }
-    void write_binary(const char* output_file) { stl_write_binary(&this->stl, output_file, ""); }
+    bool ReadSTLFile(const char* input_file) { return stl_open(&stl, input_file); }
+    bool write_ascii(const char* output_file) { return stl_write_ascii(&this->stl, output_file, ""); }
+    bool write_binary(const char* output_file) { return stl_write_binary(&this->stl, output_file, ""); }
     void repair();
     float volume();
     void check_topology();
diff --git a/xs/xsp/TriangleMesh.xsp b/xs/xsp/TriangleMesh.xsp
index a188e0b8d..3cfbaa54d 100644
--- a/xs/xsp/TriangleMesh.xsp
+++ b/xs/xsp/TriangleMesh.xsp
@@ -46,7 +46,6 @@ TriangleMesh::ReadFromPerl(vertices, facets)
     SV* facets
     CODE:
         stl_file &stl = THIS->stl;
-        stl.error = 0;
         stl.stats.type = inmemory;
     
         // count facets and allocate memory