diff --git a/resources/views/rd/fire-shutter-drawing/index.blade.php b/resources/views/rd/fire-shutter-drawing/index.blade.php
index 4ce1f1af..5206d9a8 100644
--- a/resources/views/rd/fire-shutter-drawing/index.blade.php
+++ b/resources/views/rd/fire-shutter-drawing/index.blade.php
@@ -556,7 +556,7 @@ function renderSettingsPreview() {
             <rect x="${ox - 20}" y="${oy - 20}" width="${sw + 40}" height="20" fill="url(#hatch)" stroke="#8b7355" stroke-width="1"/>
             <!-- Shutter Box -->
             <rect x="${ox}" y="${oy}" width="${sw}" height="${boxH}" fill="#374151" stroke="#94a3b8" stroke-width="2" rx="3"/>
-            <text x="${ox + sw/2}" y="${oy + boxH/2 + 4}" fill="#60a5fa" font-size="11" font-weight="900" text-anchor="middle" font-family="Pretendard">셔터박스 (HEAD BOX)</text>
+            <text x="${ox + sw/2}" y="${oy + boxH/2 + 4}" fill="#60a5fa" font-size="11" font-weight="900" text-anchor="middle" font-family="Pretendard">셔터박스 (CASE)</text>
             <!-- Shaft circle -->
             <circle cx="${ox + sw/2}" cy="${oy + boxH/2}" r="18" fill="none" stroke="#64748b" stroke-width="2" stroke-dasharray="4 2"/>
             <!-- Guide Rails -->
@@ -809,7 +809,7 @@ function renderSbFront() {
             <line x1="${ox + sw + 20}" y1="${oy}" x2="${ox + sw + 20}" y2="${oy + sh}" stroke="#3b82f6" stroke-width="1"/>
             <text x="${ox + sw + 35}" y="${oy + sh/2 + 4}" fill="#3b82f6" font-size="11" font-weight="900" text-anchor="start" font-family="Pretendard">${b.height} mm</text>
             <!-- Case label -->
-            <text x="${ox + sw/2}" y="${oy - 10}" fill="#94a3b8" font-size="11" font-weight="900" text-anchor="middle" font-family="Pretendard">HEAD BOX / CASE — t=${b.thickness}mm</text>
+            <text x="${ox + sw/2}" y="${oy - 10}" fill="#94a3b8" font-size="11" font-weight="900" text-anchor="middle" font-family="Pretendard">셔터박스 (CASE) — t=${b.thickness}mm</text>
         </svg>`;
 
         displaySvg(svg);
@@ -1065,13 +1065,14 @@ function fs3dBuild() {
         meshes.slats.position.set(0, H - shutterH / 2, 0);
         scene.add(meshes.slats);
 
-        // Slat lines (horizontal grooves for steel type)
+        // Slat lines (horizontal grooves for steel type) — local coords relative to meshes.slats
         if (S.productType === 'steel') {
             const lineGroup = new THREE.Group();
             const slatPitch = 80; // mm
             const lineCount = Math.floor(shutterH / slatPitch);
             for (let i = 1; i < lineCount; i++) {
-                const y = H - i * slatPitch;
+                const y = shutterH / 2 - i * slatPitch; // local Y: top of plane → down
+                if (y < -shutterH / 2) break;
                 const lineGeo = new THREE.BufferGeometry().setFromPoints([
                     new THREE.Vector3(-W/2 + 10, y, 1),
                     new THREE.Vector3(W/2 - 10, y, 1)