From a697950a369ebcc9da7c0bee99157eafb90fe3d2 Mon Sep 17 00:00:00 2001
From: Stewart Allen <stewart.allen@gmail.com>
Date: Sun, 5 Oct 2025 10:22:14 -0400
Subject: [PATCH] lower fan speed for bridge layers

---
 src/kiri/mode/fdm/export.js  | 5 +++--
 src/kiri/mode/fdm/prepare.js | 8 ++++++++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/src/kiri/mode/fdm/export.js b/src/kiri/mode/fdm/export.js
index b6768e4b..6b359f56 100644
--- a/src/kiri/mode/fdm/export.js
+++ b/src/kiri/mode/fdm/export.js
@@ -613,6 +613,7 @@ export function fdm_export(print, online, ondone, ondebug) {
         for (pidx=0; pidx<path.length; pidx++) {
             out = path[pidx];
             speedMMM = (out.speed || process.outputFeedrate) * 60; // range
+            fanSpeed = out.fan ?? fanSpeed;
 
             // hint to controller that we're working on a specific object
             // so that gcode between start/stop comments can be cancelled
@@ -685,13 +686,13 @@ export function fdm_export(print, online, ondone, ondebug) {
             }
 
             // in belt mode, fan can change per segment (for base)
-            if (isBelt) {
+            // if (isBelt) {
                 setTempFanSpeed(out.fan);
                 if (fanSpeed !== lastFanSpeed) {
                     appendAllSub(gcodeFan);
                     lastFanSpeed = fanSpeed;
                 }
-            }
+            // }
 
             if (lastp && out.emit) {
                 if (arcDist) {
diff --git a/src/kiri/mode/fdm/prepare.js b/src/kiri/mode/fdm/prepare.js
index c1453b77..301d47fb 100644
--- a/src/kiri/mode/fdm/prepare.js
+++ b/src/kiri/mode/fdm/prepare.js
@@ -814,6 +814,7 @@ function slicePrintPath(print, slice, startPoint, offset, output, opt = {}) {
         shellOrder = {"out-in":-1,"in-out":1,"alternate":-2}[process.sliceShellOrder] || -1,
         sparseMult = process.outputSparseMult,
         coastDist = process.outputCoastDist || 0,
+        fanSpeed = process.outputFanSpeed,
         firstShellSpeed = process.firstLayerRate,
         firstFillSpeed = process.firstLayerFillRate,
         firstPrintMult = process.firstLayerPrintMult,
@@ -863,6 +864,7 @@ function slicePrintPath(print, slice, startPoint, offset, output, opt = {}) {
     // override: adapt bridge layer speed
     if (slice.isBridgeLayer) {
         fillSpeed /= 2;
+        printSpeed /= 2;
     }
 
     // apply first layer extrusion multipliers
@@ -1614,6 +1616,12 @@ function slicePrintPath(print, slice, startPoint, offset, output, opt = {}) {
     // add offset points to total print
     print.addPrintPoints(preout, output);
 
+    // bridge layer fan change
+    if (slice.isBridgeLayer) {
+        preout[0].fan = Math.round(fanSpeed / 3);
+        preout.peek().fan = fanSpeed;
+    }
+
     // create next layer start point and annotate
     // with print time for previous layer (hack to
     // avoid changing return signature rn)