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 777a7a3..9e541d3 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
@@ -3,10 +3,16 @@
   <div class="section">
     @if (selectedFile()) {
       <div class="viewer-wrapper">
-         <app-stl-viewer 
-            [file]="selectedFile()"
-            [color]="getSelectedFileColor()">
-         </app-stl-viewer>
+         @if (isStepFile(selectedFile())) {
+             <div class="step-warning">
+                 <p>{{ 'CALC.STEP_WARNING' | translate }}</p>
+             </div>
+         } @else {
+             <app-stl-viewer 
+                [file]="selectedFile()"
+                [color]="getSelectedFileColor()">
+             </app-stl-viewer>
+         }
          <!-- Close button removed as requested -->
       </div>
     }
diff --git a/frontend/src/app/features/calculator/components/upload-form/upload-form.component.scss b/frontend/src/app/features/calculator/components/upload-form/upload-form.component.scss
index 3331860..b7a5d77 100644
--- a/frontend/src/app/features/calculator/components/upload-form/upload-form.component.scss
+++ b/frontend/src/app/features/calculator/components/upload-form/upload-form.component.scss
@@ -202,6 +202,18 @@
 .progress-fill {
     height: 100%;
     background: var(--color-brand);
-    width: 0%;
-    transition: width 0.2s ease-out;
+}
+
+.step-warning {
+    display: flex;
+    justify-content: center;
+    align-items: center;
+    height: 300px;
+    background: var(--color-neutral-100);
+    border: 1px dashed var(--color-border);
+    border-radius: var(--radius-md);
+    padding: var(--space-4);
+    text-align: center;
+    color: var(--color-text-muted);
+    font-weight: 500;
 }
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 917284c..f222937 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
@@ -61,7 +61,13 @@ export class UploadFormComponent implements OnInit {
       }
   }
 
-  acceptedFormats = '.stl,.3mf,.step,.stp,.obj,.amf,.ply,.igs,.iges';
+  acceptedFormats = '.stl,.3mf,.step,.stp';
+
+  isStepFile(file: File | null): boolean {
+      if (!file) return false;
+      const name = file.name.toLowerCase();
+      return name.endsWith('.step') || name.endsWith('.stp');
+  }
 
   constructor() {
     this.form = this.fb.group({
diff --git a/frontend/src/app/features/contact/components/contact-form/contact-form.component.html b/frontend/src/app/features/contact/components/contact-form/contact-form.component.html
index 86a2335..9793ba8 100644
--- a/frontend/src/app/features/contact/components/contact-form/contact-form.component.html
+++ b/frontend/src/app/features/contact/components/contact-form/contact-form.component.html
@@ -51,7 +51,7 @@
       <div class="drop-zone" (click)="fileInput.click()"
            (dragover)="onDragOver($event)" (drop)="onDrop($event)">
         <input #fileInput type="file" multiple (change)="onFileSelected($event)" hidden
-               accept=".jpg,.jpeg,.png,.pdf,.stl,.step,.stp,.3mf,.obj">
+               accept=".jpg,.jpeg,.png,.pdf,.stl,.step,.stp,.3mf">
         <p>{{ 'CONTACT.DROP_FILES' | translate }}</p>
       </div>
 
diff --git a/frontend/src/app/shared/components/app-dropzone/app-dropzone.component.ts b/frontend/src/app/shared/components/app-dropzone/app-dropzone.component.ts
index fd1e563..fbfc442 100644
--- a/frontend/src/app/shared/components/app-dropzone/app-dropzone.component.ts
+++ b/frontend/src/app/shared/components/app-dropzone/app-dropzone.component.ts
@@ -10,8 +10,8 @@ import { CommonModule } from '@angular/common';
 })
 export class AppDropzoneComponent {
   label = input<string>('Drop files here or click to upload');
-  subtext = input<string>('Supports .stl, .obj');
-  accept = input<string>('.stl,.obj');
+  subtext = input<string>('Supports .stl, .3mf, .step');
+  accept = input<string>('.stl,.3mf,.step,.stp');
   multiple = input<boolean>(true);
   
   filesDropped = output<File[]>();
diff --git a/frontend/src/assets/i18n/en.json b/frontend/src/assets/i18n/en.json
index bb9f7a1..3397f0e 100644
--- a/frontend/src/assets/i18n/en.json
+++ b/frontend/src/assets/i18n/en.json
@@ -43,7 +43,7 @@
     "MODE_EASY": "Quick",
     "MODE_ADVANCED": "Advanced",
     "UPLOAD_LABEL": "Drag your 3D file here",
-    "UPLOAD_SUB": "Supports STL, 3MF, STEP, OBJ up to 50MB",
+    "UPLOAD_SUB": "Supports STL, 3MF, STEP up to 50MB",
     "MATERIAL": "Material",
     "QUALITY": "Quality",
     "QUANTITY": "Quantity",
@@ -68,7 +68,8 @@
     "BENEFITS_1": "Automatic quote with instant cost and time",
     "BENEFITS_2": "Selected materials and quality control",
     "BENEFITS_3": "CAD consultation if file needs modifications",
-    "ERR_FILE_REQUIRED": "File is required."
+    "ERR_FILE_REQUIRED": "File is required.",
+    "STEP_WARNING": "3D preview is not available for STEP files, but the calculator works perfectly. You can proceed with the quotation."
   },
   "SHOP": {
     "TITLE": "Technical solutions",
@@ -140,7 +141,7 @@
     "COMPANY_NAME": "Company Name",
     "REF_PERSON": "Reference Person",
     "UPLOAD_LABEL": "Attachments",
-    "UPLOAD_HINT": "Max 15 files. Supported: Images, PDF, STL, STEP, 3MF, OBJ",
+    "UPLOAD_HINT": "Max 15 files. Supported: Images, PDF, STL, STEP, 3MF",
     "DROP_FILES": "Drop files here or click to upload",
     "PLACEHOLDER_NAME": "Your Name",
     "PLACEHOLDER_EMAIL": "your@email.com",
diff --git a/frontend/src/assets/i18n/it.json b/frontend/src/assets/i18n/it.json
index a7655a1..1d0e946 100644
--- a/frontend/src/assets/i18n/it.json
+++ b/frontend/src/assets/i18n/it.json
@@ -58,14 +58,14 @@
   },
   "CALC": {
     "TITLE": "Calcola Preventivo 3D",
-    "SUBTITLE": "Carica il tuo file 3D (STL, 3MF, STEP...) e ricevi una stima immediata di costi e tempi di stampa.",
+    "SUBTITLE": "Carica il tuo file 3D (STL, 3MF, STEP), imposta la qualtà, colore e calcola immediatamente prezzo e tempi.",
     "CTA_START": "Inizia Ora",
     "BUSINESS": "Aziende",
     "PRIVATE": "Privati",
     "MODE_EASY": "Base",
     "MODE_ADVANCED": "Avanzata",
     "UPLOAD_LABEL": "Trascina il tuo file 3D qui",
-    "UPLOAD_SUB": "Supportiamo STL, 3MF, STEP, OBJ fino a 50MB",
+    "UPLOAD_SUB": "Supportiamo STL, 3MF, STEP fino a 50MB",
     "MATERIAL": "Materiale",
     "QUALITY": "Qualità",
     "PRINT_SPEED": "Velocità di Stampa",
@@ -101,7 +101,8 @@
     "UPLOADING": "Caricamento...",
     "PROCESSING": "Elaborazione...",
     "NOTES_PLACEHOLDER": "Istruzioni specifiche...",
-    "SETUP_NOTE": "* Include {{cost}} Costo di Setup"
+    "SETUP_NOTE": "* Include {{cost}} Costo di Setup",
+    "STEP_WARNING": "La visualizzazione 3D non è compatibile con i file STEP, ma il calcolatore funziona."
   },
   "QUOTE": {
     "PROCEED_ORDER": "Procedi con l'ordine",
@@ -203,7 +204,7 @@
     "COMPANY_NAME": "Ragione Sociale",
     "REF_PERSON": "Persona di Riferimento",
     "UPLOAD_LABEL": "Allegati",
-    "UPLOAD_HINT": "Max 15 file. Supportati: Immagini, PDF, STL, STEP, 3MF, OBJ",
+    "UPLOAD_HINT": "Max 15 file. Supportati: Immagini, PDF, STL, STEP, 3MF",
     "DROP_FILES": "Trascina qui i file o clicca per caricare",
     "PLACEHOLDER_NAME": "Il tuo nome",
     "PLACEHOLDER_EMAIL": "tuo@email.com",