diff --git a/release.md b/release.md
index 7fec94b2..b3c637c6 100644
--- a/release.md
+++ b/release.md
@@ -17,6 +17,7 @@ Full docs @ https://docs.grid.space/projects/kiri-moto
 * add bridging option in CAM contouring
 * add option to force z max routing in CAM
 * add option to ignore z bottom in CAM contouring
+* add CAM Z bottom visualization, make it relative to stock instead of part
 * extend url loading of workspaces to all formats
 * alert when healing is enabled and non-manifold geometries are detected
 * fix thin output start and end point tracking which broke retraction
diff --git a/src/kiri-mode/cam/client.js b/src/kiri-mode/cam/client.js
index a283f264..5f2c9069 100644
--- a/src/kiri-mode/cam/client.js
+++ b/src/kiri-mode/cam/client.js
@@ -16,6 +16,7 @@ let isAnimate,
     isCamMode,
     isParsed,
     camStock,
+    camZBottom,
     current,
     poppedRec,
     hoveredOp,
@@ -1314,10 +1315,10 @@ function updateStock(args, event) {
     }
 
     if (!isCamMode) {
-        if (camStock) {
-            SPACE.world.remove(camStock);
-            camStock = null;
-        }
+        SPACE.world.remove(camZBottom);
+        SPACE.world.remove(camStock);
+        camStock = null;
+        camZBottom = null;
         return;
     }
 
@@ -1339,11 +1340,11 @@ function updateStock(args, event) {
     UI.func.animate.classList.add('disabled');
 
     // create/inject cam stock if stock size other than default
+    let csx = proc.camStockX;
+    let csy = proc.camStockY;
+    let csz = proc.camStockZ;
     if (compute) {
         UI.func.animate.classList.remove('disabled');
-        let csx = proc.camStockX;
-        let csy = proc.camStockY;
-        let csz = proc.camStockZ;
         if (offset) {
             let min = { x: Infinity, y: Infinity, z: 0 };
             let max = { x: -Infinity, y: -Infinity, z: -Infinity };
@@ -1402,6 +1403,28 @@ function updateStock(args, event) {
         delta = 0;
     }
 
+    SPACE.world.remove(camZBottom);
+    if (proc.camZBottom) {
+        let max = { x: csx, y: csy };
+        for (let w of widgets) {
+            max.x = Math.max(max.x, w.track.box.w);
+            max.y = Math.max(max.y, w.track.box.h);
+        }
+        let geo = new THREE.PlaneGeometry(max.x, max.y);
+        let mat = new THREE.MeshBasicMaterial({
+            color: 0x777777,
+            opacity: 0.55,
+            transparent: true,
+            side:THREE.DoubleSide
+        });
+        camZBottom = new THREE.Mesh(geo, mat);
+        camZBottom.renderOrder = 1;
+        camZBottom.position.z = proc.camZBottom;
+        SPACE.world.add(camZBottom);
+    } else {
+        camZBottom = undefined;
+    }
+
     const {x, y, z} = stock;
     if (x && y && z && !STACKS.getStack('bounds')) {
         const render = new kiri.Layers().setLayer('bounds', { face: 0xaaaaaa, line: 0xaaaaaa });
diff --git a/src/kiri-mode/cam/slice.js b/src/kiri-mode/cam/slice.js
index c88d8b85..67f498eb 100644
--- a/src/kiri-mode/cam/slice.js
+++ b/src/kiri-mode/cam/slice.js
@@ -34,12 +34,13 @@ CAM.slice = function(settings, widget, onupdate, ondone) {
         camOps = widget.camops = [],
         sliceAll = widget.slices = [],
         bounds = widget.getBoundingBox(),
-        zBottom = proc.camZBottom,
+        wztop = widget.track.top,
+        ztOff = hasStock ? stock.z - wztop : 0,
+        zbOff = hasStock ? wztop - widget.track.box.d : 0,
+        zBottom = proc.camZBottom - zbOff,
         zMin = Math.max(bounds.min.z, zBottom),
         zMax = bounds.max.z,
         zThru = zBottom === 0 ? (proc.camZThru || 0) : 0,
-        wztop = widget.track.top,
-        ztOff = hasStock ? stock.z - wztop : 0,
         zTop = zMax + ztOff,
         minToolDiam = Infinity,
         maxToolDiam = -Infinity,
diff --git a/src/kiri-mode/cam/topo.js b/src/kiri-mode/cam/topo.js
index f54c9d78..5b7f1ac9 100644
--- a/src/kiri-mode/cam/topo.js
+++ b/src/kiri-mode/cam/topo.js
@@ -39,7 +39,7 @@ class Topo {
             maxX = bounds.max.x,
             minY = bounds.min.y,
             maxY = bounds.max.y,
-            zBottom = contour.bottom ? proc.camZBottom : 0,
+            zBottom = contour.bottom ? state.zBottom : 0,
             zMin = Math.max(bounds.min.z, zBottom) + 0.0001,
             boundsX = maxX - minX,
             boundsY = maxY - minY,