diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..9f31f51
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,16 @@
+PARAMSETS != cat params.json | jq -r '.parameterSets | keys[] | select(length > 0)'
+OUTPUTS = $(PARAMSETS:%=%.3mf)
+
+all: $(OUTPUTS)
+
+clean:
+	rm -f $(OUTPUTS) *.bare.3mf *.log
+
+targets:
+	@for i in $(PARAMSETS); do echo $$i.3mf; done
+
+%.bare.3mf %.log: temp-tower.scad params.json
+	openscad -o $*.bare.3mf -P $* -p params.json temp-tower.scad 2>$*.log
+
+%.3mf: %.bare.3mf %.log postprocess.sh
+	./postprocess.sh $@ $*.bare.3mf $*.log
diff --git a/README.md b/README.md
index f0f8eb6..ae0ef32 100644
--- a/README.md
+++ b/README.md
@@ -4,14 +4,31 @@ A Tiny Temperature Tower
 This is a tiny temperature tower.
 I made it because I suspected my printer's hotend thermistor was reporting too cold.
 
-`build.sh` generates `.3mf` files 
-with extra code to make PrusaSlicer change temperatures automatically.
+(I think I was right.)
 
-Defining A New Model
-======================
 
-You can add a new set of model parameters to `params.json`.
+Building
+----------
+
+This uses make(1).
+If you've never used make(1) before,
+here's a quick introduction:
+
+    make all      # Build everything
+    make clean    # Remove build files
+    make targets  # List everything you can build
+
+
+Building A New Model
+---------------------------
+
+You can add a new set of model parameters to [params.json](params.json).
 
 Let's say you named your new parameters `my-new-parameters`.
-`build.sh my-new-parameters` will generate `my-new-parameters.3mf`,
-with PrusaSlicer temperature changes and ponies and everything.
+
+    make my-new-parameters.3mf  # Build only your model
+
+The resulting 3mf file will have 
+temperature changes for PrusaSlicer
+and ponies
+and everything!
diff --git a/build.sh b/build.sh
deleted file mode 100755
index 9d4506a..0000000
--- a/build.sh
+++ /dev/null
@@ -1,69 +0,0 @@
-#! /bin/sh
-
-set -e
-
-# paramsets contains the location of the OpenSCAD parameter sets.
-# see https://en.wikibooks.org/wiki/OpenSCAD_User_Manual/Customizer#Saving_Parameters_value_in_JSON_file
-paramsets=params.json
-
-# run executes a program after printing the commandline to stdout.
-run () {
-    echo "=== $*"
-    "$@"
-}
-
-# render turns OpenSCAD echo into 3mf temperature changes.
-# 
-# It does this by kludging together a PrusaSlicer-specific Metadata file.
-render () {
-    basename=$1; shift
-    logfile=$basename.log
-    run openscad -o $basename "$@" temp-tower.scad 2>&1 | tee $logfile
-
-    rm -rf Metadata
-    mkdir -p Metadata
-    cat $logfile | while IFS=# read _ _ custom type path text _; do
-        [ "$custom#$type" = "CUSTOM#3mf" ] || continue
-        echo $text >> $path
-    done
-
-    run zip $basename $custom
-    
-    rm $custom $logfile
-    rmdir Metadata
-}
-
-# paramsets lists all defined parameter sets, one per line.
-paramsets () {
-    cat $paramsets | jq -r '.parameterSets | keys[] | select(length > 0)'
-}
-
-case "$1" in
-    -h|-help|--help)
-        cat <<EOD
-Usage: $0 [-paramsets] [PARAMSET ...]
-
-Generates .3mf files with temperature changes
-for each given parameter set.
-
-Parameter sets are specified in $paramsets.
-
--paramsets   List all defined parameter sets, and exit.
-EOD
-        exit 1
-        ;; 
-    -p*|--p*)
-        paramsets
-        exit
-        ;;
-    "")
-        paramsets | while read paramset; do
-            render $paramset.3mf -P $paramset -p $paramsets
-        done
-        ;;
-    *)
-        for paramset in "$@"; do
-            render $paramset.3mf -P $paramset -p $paramsets
-        done
-        ;;
-esac
diff --git a/postprocess.sh b/postprocess.sh
new file mode 100755
index 0000000..fb28b73
--- /dev/null
+++ b/postprocess.sh
@@ -0,0 +1,23 @@
+#! /bin/sh
+
+## Postprocess a 3mf file, adding in anything in the log
+
+set -e
+
+outfile=$(realpath $1)
+infile=$(realpath $2)
+logfile=$(realpath $3)
+
+tmpdir=$(mktemp -d --tmpdir 3mf.XXXXXXXXXX)
+trap "rm -rf $tmpdir" EXIT
+
+(cd $tmpdir && unzip $infile)
+
+cat $logfile | while IFS=# read _ _ custom type path text _; do
+    [ "$custom#$type" = "CUSTOM#3mf" ] || continue
+    basepath=$(dirname $path)
+    mkdir -p $tmpdir/$basepath
+    echo $text >> $tmpdir/$path
+done
+
+(cd $tmpdir && zip -r $outfile .)