&gt; they just don&#x27;t do anything useful.<p>We use a cheap 3D printer weekly to make little fixtures, brackets and mounts for robots. These we use for months or years. They are also incredibly great for prototyping: print the doohickey in crappy plastic, check it fits together right, then get it made for real. It&#x27;s amazing how helpful it is to have a model in your hand for debugging before spending a fortune.