diff --git a/nhf/touhou/houjuu_nue/joints.py b/nhf/touhou/houjuu_nue/joints.py
index e3d5595..76d6ccb 100644
--- a/nhf/touhou/houjuu_nue/joints.py
+++ b/nhf/touhou/houjuu_nue/joints.py
@@ -599,6 +599,8 @@ class DiskJoint(Model):
 
     # Angular span of movement
     movement_angle: float = 120.0
+    # leave some gap for cushion
+    movement_gap: float = 5.0
     # Angular span of tongue on disk
     tongue_span: float = 30.0
     tongue_length: float = 10.0
@@ -704,11 +706,11 @@ class DiskJoint(Model):
         wall = Cq.Solid.makeCylinder(
             radius=self.radius_housing,
             height=height,
-            angleDegrees=360 - self.opening_span,
+            angleDegrees=360 - self.opening_span - self.movement_gap*2,
         ).cut(Cq.Solid.makeCylinder(
             radius=self.radius_disk,
             height=height,
-        )).rotate((0, 0, 0), (0, 0, 1), self.opening_span)
+        )).rotate((0, 0, 0), (0, 0, 1), self.opening_span+self.movement_gap)
         return wall
 
     @target(name="housing-lower")