diff --git a/frontend/src/app/features/calculator/components/upload-form/upload-form.component.html b/frontend/src/app/features/calculator/components/upload-form/upload-form.component.html
index 9e541d3..4956e93 100644
--- a/frontend/src/app/features/calculator/components/upload-form/upload-form.component.html
+++ b/frontend/src/app/features/calculator/components/upload-form/upload-form.component.html
@@ -1,14 +1,14 @@
 <form [formGroup]="form" (ngSubmit)="onSubmit()">
-  
+
   <div class="section">
     @if (selectedFile()) {
       <div class="viewer-wrapper">
-         @if (isStepFile(selectedFile())) {
+         @if (!isStepFile(selectedFile())) {
              <div class="step-warning">
                  <p>{{ 'CALC.STEP_WARNING' | translate }}</p>
              </div>
          } @else {
-             <app-stl-viewer 
+             <app-stl-viewer
                 [file]="selectedFile()"
                 [color]="getSelectedFileColor()">
              </app-stl-viewer>
@@ -16,11 +16,11 @@
          <!-- Close button removed as requested -->
       </div>
     }
-    
+
     <!-- Initial Dropzone (Visible only when no files) -->
     @if (items().length === 0) {
-        <app-dropzone 
-            [label]="'CALC.UPLOAD_LABEL' | translate" 
+        <app-dropzone
+            [label]="'CALC.UPLOAD_LABEL' | translate"
             [subtext]="'CALC.UPLOAD_SUB' | translate"
             [accept]="acceptedFormats"
             [multiple]="true"
@@ -36,14 +36,14 @@
                     <div class="card-header">
                         <span class="file-name" [title]="item.file.name">{{ item.file.name }}</span>
                     </div>
-                    
+
                     <div class="card-body">
                         <div class="card-controls">
                              <div class="qty-group">
                                 <label>{{ 'CALC.QTY_SHORT' | translate }}</label>
-                                <input 
-                                    type="number" 
-                                    min="1" 
+                                <input
+                                    type="number"
+                                    min="1"
                                     [value]="item.quantity"
                                     (change)="updateItemQuantity(i, $event)"
                                     class="qty-input"
@@ -52,14 +52,14 @@
 
                             <div class="color-group">
                                 <label>{{ 'CALC.COLOR_LABEL' | translate }}</label>
-                                <app-color-selector 
-                                    [selectedColor]="item.color" 
+                                <app-color-selector
+                                    [selectedColor]="item.color"
                                     [variants]="currentMaterialVariants()"
                                     (colorSelected)="updateItemColor(i, $event)">
                                 </app-color-selector>
                             </div>
                         </div>
-                        
+
                         <button type="button" class="btn-remove" (click)="removeItem(i); $event.stopPropagation()" title="Remove file">
                             X
                         </button>
@@ -67,17 +67,17 @@
                 </div>
             }
         </div>
-        
+
         <!-- "Add Files" Button (Visible only when files exist) -->
         <div class="add-more-container">
             <input #additionalInput type="file" [accept]="acceptedFormats" multiple hidden (change)="onAdditionalFilesSelected($event)">
-            
+
             <button type="button" class="btn-add-more" (click)="additionalInput.click()">
                 + {{ 'CALC.ADD_FILES' | translate }}
             </button>
         </div>
     }
-    
+
     @if (items().length === 0 && form.get('itemsTouched')?.value) {
       <div class="error-msg">{{ 'CALC.ERR_FILE_REQUIRED' | translate }}</div>
     }
@@ -104,7 +104,7 @@
         ></app-select>
     }
   </div>
-  
+
   <!-- Global quantity removed, now per item -->
 
   @if (mode() === 'advanced') {
@@ -128,7 +128,7 @@
           type="number"
           [label]="'CALC.INFILL' | translate"
         ></app-input>
-        
+
         <div class="checkbox-row">
             <input type="checkbox" formControlName="supportEnabled" id="support">
             <label for="support">{{ 'CALC.SUPPORT' | translate }}</label>
@@ -153,9 +153,9 @@
         </div>
     }
 
-    <app-button 
-      type="submit" 
-      [disabled]="items().length === 0 || loading()" 
+    <app-button
+      type="submit"
+      [disabled]="items().length === 0 || loading()"
       [fullWidth]="true">
       {{ loading() ? (uploadProgress() < 100 ? ('CALC.UPLOADING' | translate) : ('CALC.PROCESSING' | translate)) : ('CALC.CALCULATE' | translate) }}
     </app-button>
diff --git a/frontend/src/app/features/calculator/components/upload-form/upload-form.component.ts b/frontend/src/app/features/calculator/components/upload-form/upload-form.component.ts
index f222937..d251d59 100644
--- a/frontend/src/app/features/calculator/components/upload-form/upload-form.component.ts
+++ b/frontend/src/app/features/calculator/components/upload-form/upload-form.component.ts
@@ -34,7 +34,7 @@ export class UploadFormComponent implements OnInit {
   private fb = inject(FormBuilder);
 
   form: FormGroup;
-  
+
   items = signal<FormItem[]>([]);
   selectedFile = signal<File | null>(null);
 
@@ -44,13 +44,13 @@ export class UploadFormComponent implements OnInit {
   nozzleDiameters = signal<SimpleOption[]>([]);
   infillPatterns = signal<SimpleOption[]>([]);
   layerHeights = signal<SimpleOption[]>([]);
-  
+
   // Store full material options to lookup variants/colors if needed later
   private fullMaterialOptions: MaterialOption[] = [];
-  
+
   // Computed variants for valid material
   currentMaterialVariants = signal<VariantOption[]>([]);
-  
+
   private updateVariants() {
       const matCode = this.form.get('material')?.value;
       if (matCode && this.fullMaterialOptions.length > 0) {
@@ -66,7 +66,7 @@ export class UploadFormComponent implements OnInit {
   isStepFile(file: File | null): boolean {
       if (!file) return false;
       const name = file.name.toLowerCase();
-      return name.endsWith('.step') || name.endsWith('.stp');
+      return name.endsWith('.stl');
   }
 
   constructor() {
@@ -83,7 +83,7 @@ export class UploadFormComponent implements OnInit {
       infillPattern: ['grid'],
       supportEnabled: [false]
     });
-    
+
     // Listen to material changes to update variants
     this.form.get('material')?.valueChanges.subscribe(() => {
         this.updateVariants();
@@ -95,7 +95,7 @@ export class UploadFormComponent implements OnInit {
           next: (options: OptionsResponse) => {
               this.fullMaterialOptions = options.materials;
               this.updateVariants(); // Trigger initial update
-              
+
               this.materials.set(options.materials.map(m => ({ label: m.label, value: m.code })));
               this.qualities.set(options.qualities.map(q => ({ label: q.label, value: q.id })));
               this.infillPatterns.set(options.infillPatterns.map(p => ({ label: p.label, value: p.id })));
@@ -194,7 +194,7 @@ export class UploadFormComponent implements OnInit {
   getSelectedFileColor(): string {
       const file = this.selectedFile();
       if (!file) return '#facf0a'; // Default
-      
+
       const item = this.items().find(i => i.file === file);
       if (item) {
           const vars = this.currentMaterialVariants();
@@ -211,7 +211,7 @@ export class UploadFormComponent implements OnInit {
       const input = event.target as HTMLInputElement;
       let val = parseInt(input.value, 10);
       if (isNaN(val) || val < 1) val = 1;
-      
+
       this.items.update(current => {
           const updated = [...current];
           updated[index] = { ...updated[index], quantity: val };
@@ -255,33 +255,33 @@ export class UploadFormComponent implements OnInit {
 
   patchSettings(settings: any) {
       if (!settings) return;
-      // settings object matches keys in our form? 
+      // settings object matches keys in our form?
       // Session has: materialCode, etc. derived from QuoteSession entity properties
       // We need to map them if names differ.
-      
+
       const patch: any = {};
       if (settings.materialCode) patch.material = settings.materialCode;
-      
+
       // Heuristic for Quality if not explicitly stored as "draft/standard/high"
-      // But we stored it in session creation? 
+      // But we stored it in session creation?
       // QuoteSession entity does NOT store "quality" string directly, only layerHeight/infill.
       // So we might need to deduce it or just set Custom/Advanced.
       // But for Easy mode, we want to show "Standard" etc.
-      
+
       // Actually, let's look at what we have in QuoteSession.
-      // layerHeightMm, infillPercent, etc. 
+      // layerHeightMm, infillPercent, etc.
       // If we are in Easy mode, we might just set the "quality" dropdown to match approx?
       // Or if we stored "quality" in notes or separate field? We didn't.
-      
+
       // Let's try to reverse map or defaults.
       if (settings.layerHeightMm) {
           if (settings.layerHeightMm >= 0.28) patch.quality = 'draft';
           else if (settings.layerHeightMm <= 0.12) patch.quality = 'high';
           else patch.quality = 'standard';
-          
+
           patch.layerHeight = settings.layerHeightMm;
       }
-      
+
       if (settings.nozzleDiameterMm) patch.nozzleDiameter = settings.nozzleDiameterMm;
       if (settings.infillPercent) patch.infillDensity = settings.infillPercent;
       if (settings.infillPattern) patch.infillPattern = settings.infillPattern;
@@ -294,7 +294,7 @@ export class UploadFormComponent implements OnInit {
   onSubmit() {
     console.log('UploadFormComponent: onSubmit triggered');
     console.log('Form Valid:', this.form.valid, 'Items:', this.items().length);
-    
+
     if (this.form.valid && this.items().length > 0) {
       console.log('UploadFormComponent: Emitting submitRequest', this.form.value);
       this.submitRequest.emit({
diff --git a/frontend/src/assets/i18n/it.json b/frontend/src/assets/i18n/it.json
index 1d0e946..d88c877 100644
--- a/frontend/src/assets/i18n/it.json
+++ b/frontend/src/assets/i18n/it.json
@@ -102,7 +102,7 @@
     "PROCESSING": "Elaborazione...",
     "NOTES_PLACEHOLDER": "Istruzioni specifiche...",
     "SETUP_NOTE": "* Include {{cost}} Costo di Setup",
-    "STEP_WARNING": "La visualizzazione 3D non è compatibile con i file STEP, ma il calcolatore funziona."
+    "STEP_WARNING": "La visualizzazione 3D non è compatibile con i file step e 3mf, ma il calcolatore funziona."
   },
   "QUOTE": {
     "PROCEED_ORDER": "Procedi con l'ordine",