diff --git a/parametric_cad/primitives/cylinder.py b/parametric_cad/primitives/cylinder.py
new file mode 100644
index 0000000..4731cd9
--- /dev/null
+++ b/parametric_cad/primitives/cylinder.py
@@ -0,0 +1,18 @@
+import trimesh
+
+class Cylinder:
+    def __init__(self, radius, height, sections=32):
+        self.radius = radius
+        self.height = height
+        self.sections = sections
+        self._position = (0, 0, 0)
+
+    def at(self, x, y, z):
+        self._position = (x, y, z)
+        return self
+
+    def mesh(self):
+        cyl = trimesh.creation.cylinder(radius=self.radius, height=self.height,
+                                        sections=self.sections)
+        cyl.apply_translation(self._position)
+        return cyl
diff --git a/parametric_cad/primitives/sphere.py b/parametric_cad/primitives/sphere.py
new file mode 100644
index 0000000..96b73bc
--- /dev/null
+++ b/parametric_cad/primitives/sphere.py
@@ -0,0 +1,17 @@
+import trimesh
+
+class Sphere:
+    def __init__(self, radius, subdivisions=3):
+        self.radius = radius
+        self.subdivisions = subdivisions
+        self._position = (0, 0, 0)
+
+    def at(self, x, y, z):
+        self._position = (x, y, z)
+        return self
+
+    def mesh(self):
+        sph = trimesh.creation.icosphere(subdivisions=self.subdivisions,
+                                         radius=self.radius)
+        sph.apply_translation(self._position)
+        return sph
diff --git a/tests/test_export.py b/tests/test_export.py
index ea3d686..d8dd6fd 100644
--- a/tests/test_export.py
+++ b/tests/test_export.py
@@ -2,6 +2,8 @@ import os
 import pytest
 import trimesh
 from parametric_cad.primitives.box import Box
+from parametric_cad.primitives.cylinder import Cylinder
+from parametric_cad.primitives.sphere import Sphere
 from parametric_cad.export.stl import STLExporter
 
 
@@ -11,3 +13,16 @@ def test_stl_exporter(tmp_path):
     path = exporter.export_mesh(box, "test_box", preview=False)
     assert os.path.isfile(path)
     assert path == str(tmp_path / "test_box.stl")
+
+
+def test_ascii_stl_multiple_objects(tmp_path):
+    exporter = STLExporter(output_dir=tmp_path, binary=False)
+    box = Box(1.0, 2.0, 1.0)
+    cyl = Cylinder(radius=0.5, height=1.0)
+    sph = Sphere(radius=0.25)
+    path = exporter.export_meshes([box, cyl, sph], "combo", preview=False)
+    assert os.path.isfile(path)
+    assert path == str(tmp_path / "combo.stl")
+    with open(path, "r", encoding="utf-8") as f:
+        first_line = f.readline().strip()
+    assert first_line.startswith("solid")
diff --git a/tests/test_primitives.py b/tests/test_primitives.py
index e25f248..20e8cd7 100644
--- a/tests/test_primitives.py
+++ b/tests/test_primitives.py
@@ -5,6 +5,8 @@ from math import cos, pi
 
 from parametric_cad.primitives.box import Box
 from parametric_cad.primitives.gear import SpurGear
+from parametric_cad.primitives.cylinder import Cylinder
+from parametric_cad.primitives.sphere import Sphere
 
 
 def test_box_mesh_extents_and_position():
@@ -21,3 +23,14 @@ def test_spur_gear_diameters():
     assert gear.pitch_diameter == pytest.approx(20.0)
     expected_base = gear.pitch_diameter * cos(20 * pi / 180)
     assert gear.base_diameter == pytest.approx(expected_base)
+
+
+def test_cylinder_and_sphere_meshes():
+    cyl = Cylinder(radius=1.0, height=2.0).at(0.5, 0.5, 0)
+    sph = Sphere(radius=1.0).at(-0.5, -0.5, 0)
+    cyl_mesh = cyl.mesh()
+    sph_mesh = sph.mesh()
+    assert isinstance(cyl_mesh, trimesh.Trimesh)
+    assert isinstance(sph_mesh, trimesh.Trimesh)
+    assert cyl_mesh.is_watertight
+    assert sph_mesh.is_watertight