diff --git a/app/config/service/loader.yml b/app/config/service/loader.yml
index 19aca24..8d04f63 100644
--- a/app/config/service/loader.yml
+++ b/app/config/service/loader.yml
@@ -17,7 +17,7 @@ services:
 
     service.loader.relation:
         class: AppBundle\Service\Loader\RelationLoader
-        arguments: ['@api.manager.rebrickable', '@app.relation.mapper']
+        arguments: ['@app.relation.mapper','@repository.ldraw.model', '@repository.rebrickable.part']
         parent: service.loader.base
 
     service.loader.image:
diff --git a/src/AppBundle/Exception/RelationMapper/InvalidResourceException.php b/src/AppBundle/Exception/RelationMapper/InvalidResourceException.php
new file mode 100644
index 0000000..c653577
--- /dev/null
+++ b/src/AppBundle/Exception/RelationMapper/InvalidResourceException.php
@@ -0,0 +1,7 @@
+<?php
+
+namespace AppBundle\Exception\RelationMapper;
+
+class InvalidResourceException extends \LogicException
+{
+}
diff --git a/src/AppBundle/Exception/RelationMapper/ResourceNotFoundException.php b/src/AppBundle/Exception/RelationMapper/ResourceNotFoundException.php
new file mode 100644
index 0000000..7676ffd
--- /dev/null
+++ b/src/AppBundle/Exception/RelationMapper/ResourceNotFoundException.php
@@ -0,0 +1,16 @@
+<?php
+
+namespace AppBundle\Exception\RelationMapper;
+
+use AppBundle\Exception\FileException;
+use Throwable;
+
+class ResourceNotFoundException extends FileException
+{
+    public function __construct($path, $message = '', $code = 0, Throwable $previous = null)
+    {
+        $message = sprintf('Resource "%s" not found.', $path);
+
+        parent::__construct($path, $message, $code, $previous);
+    }
+}
diff --git a/src/AppBundle/Exception/Stl/LDLibraryMissingException.php b/src/AppBundle/Exception/Stl/LDLibraryMissingException.php
new file mode 100644
index 0000000..460411c
--- /dev/null
+++ b/src/AppBundle/Exception/Stl/LDLibraryMissingException.php
@@ -0,0 +1,16 @@
+<?php
+
+namespace AppBundle\Exception\Stl;
+
+use Symfony\Component\Form\Exception\LogicException;
+use Throwable;
+
+class LDLibraryMissingException extends LogicException
+{
+    public function __construct($message = '', $code = 0, Throwable $previous = null)
+    {
+        $message = 'Invalid LDraw library.';
+
+        parent::__construct($message, $code, $previous);
+    }
+}
diff --git a/src/AppBundle/Service/Loader/RelationLoader.php b/src/AppBundle/Service/Loader/RelationLoader.php
index f778019..146a627 100644
--- a/src/AppBundle/Service/Loader/RelationLoader.php
+++ b/src/AppBundle/Service/Loader/RelationLoader.php
@@ -2,40 +2,46 @@
 
 namespace AppBundle\Service\Loader;
 
-use AppBundle\Api\Manager\RebrickableManager;
 use AppBundle\Entity\LDraw\Model;
 use AppBundle\Entity\Rebrickable\Part;
-use AppBundle\Utils\RelationMapper;
+use AppBundle\Repository\LDraw\ModelRepository;
+use AppBundle\Repository\Rebrickable\PartRepository;
+use AppBundle\Util\RelationMapper;
 
 class RelationLoader extends BaseLoader
 {
     /** @var RelationMapper */
     private $relationMapper;
 
-    /** @var RebrickableManager */
-    private $rebrickableAPIManager;
+    /** @var ModelRepository */
+    private $modelRepository;
+
+    /** @var PartRepository */
+    private $partRepository;
 
     /**
      * RelationLoader constructor.
      *
-     * @param RebrickableManager $rebrickableApiManager
-     * @param RelationMapper     $relationMapper
+     * @param RelationMapper  $relationMapper
+     * @param ModelRepository $modelRepository
+     * @param PartRepository  $partRepository
      */
-    public function __construct($rebrickableApiManager, $relationMapper)
+    public function __construct($relationMapper, $modelRepository, $partRepository)
     {
-        $this->rebrickableAPIManager = $rebrickableApiManager;
         $this->relationMapper = $relationMapper;
+        $this->modelRepository = $modelRepository;
+        $this->partRepository = $partRepository;
     }
 
     public function loadAll()
     {
-        $parts = $this->em->getRepository(Part::class)->findAll();
+        $parts = $this->partRepository->findAll();
         $this->load($parts);
     }
 
     public function loadNotPaired($parts)
     {
-        $parts = $this->em->getRepository(Part::class)->findAllNotPaired();
+        $parts = $this->partRepository->findAllNotPaired();
         $this->load($parts);
     }
 
@@ -44,7 +50,13 @@ class RelationLoader extends BaseLoader
         $this->initProgressBar(count($parts));
         /** @var Part $part */
         foreach ($parts as $part) {
-            $this->loadPartRelation($part);
+            $model = $this->loadPartRelation($part);
+
+            if ($model) {
+                $part->setModel($model);
+                $this->partRepository->save($part);
+            }
+
             $this->progressBar->setMessage($part->getNumber());
             $this->progressBar->advance();
         }
@@ -56,33 +68,28 @@ class RelationLoader extends BaseLoader
      *
      * @param Part $part
      *
-     * @return Model $m
+     * @return Model|null
      */
     private function loadPartRelation(Part $part)
     {
-        $modelRepository = $this->em->getRepository(Model::class);
-
         $number = $part->getNumber();
-        $model = $modelRepository->findOneByNumber($number);
+        $model = $this->modelRepository->findOneByNumber($number);
         if (!$model) {
             $number = $this->relationMapper->find($this->getPrintedParentId($number), 'part_model');
-            $model = $modelRepository->findOneByNumber($number);
+            $model = $this->modelRepository->findOneByNumber($number);
 
             if (!$model) {
-                $model = $modelRepository->findOneByName($part->getName());
+                $model = $this->modelRepository->findOneByName($part->getName());
             }
         }
 
-        if ($model) {
-            $part->setModel($model);
-            $this->em->getRepository(Part::class)->save($part);
-        }
+        return $model;
     }
 
     /**
-     * Get printed part parent number.
+     * Get id of parent for printed parts form part id.
      *
-     * @param $id
+     * @param $number
      *
      * @return string|null LDraw number of printed part parent
      */
diff --git a/src/AppBundle/Util/LDModelParser.php b/src/AppBundle/Util/LDModelParser.php
index b4c6df8..516bfc4 100644
--- a/src/AppBundle/Util/LDModelParser.php
+++ b/src/AppBundle/Util/LDModelParser.php
@@ -101,16 +101,16 @@ class LDModelParser
                     $model['license'] = preg_replace('/(^!LICENSE )(.*) : (.*)$/', '$2', $line);
                 }
             } elseif (strpos($line, '1 ') === 0) {
-                $reference = $this->getReferencedModelNumber($line);
+                if ($reference = $this->getReferencedModelNumber($line)) {
+                    $id = strtolower($reference['id']);
+                    $color = strtolower($reference['color']);
 
-                $id = strtolower($reference['id']);
-                $color = strtolower($reference['color']);
-
-                // group subparts by color and id
-                if (isset($model['subparts'][$id][$color])) {
-                    $model['subparts'][$id][$color] = $model['subparts'][$id][$color] + 1;
-                } else {
-                    $model['subparts'][$id][$color] = 1;
+                    // group subparts by color and id
+                    if (isset($model['subparts'][$id][$color])) {
+                        $model['subparts'][$id][$color] = $model['subparts'][$id][$color] + 1;
+                    } else {
+                        $model['subparts'][$id][$color] = 1;
+                    }
                 }
             } elseif (!empty($line) && !in_array($line[0], ['2', '3', '4', '5'])) {
                 throw new ErrorParsingLineException($model['id'], $line);
@@ -141,13 +141,16 @@ class LDModelParser
      *
      * @param $line
      *
-     * @return string|null Filename of referenced part
+     * @return array|null Filename of referenced part
      */
     public function getReferencedModelNumber($line)
     {
         $line = strtolower(preg_replace('!\s+!', ' ', $line));
 
-        if (preg_match('/^1 ([0-9]{1,3}) (.*) (.*)\.dat$/', $line, $matches)) {
+        // Do not load inverse part as subpart of model
+        if (preg_match('/^1 ([0-9]{1,3}) (0 0 0 -1 0 0 0 1 0 0 0 1) (.*)\.dat$/', $line, $matches)) {
+            return null;
+        } elseif (preg_match('/^1 ([0-9]{1,3}) (.*) (.*)\.dat$/', $line, $matches)) {
             $id = str_replace('\\', DIRECTORY_SEPARATOR, $matches[3]);
             $color = $matches[1];