3.5. IDeATe Laser Cutter Guide

The IDeATe@Hunt fabrication facility includes three Rabbit laser cutters. These are extremely useful tools for cutting complex 2D forms. The best feature of these tools is the speed with which an idea can be tested: it is possible to conceive of a part, create a 2D drawing, output a DXF, and cut material to make a functional part within minutes.

The laser cuts flat materials such as cardboard, fabric, paper, MDF, plywood, and acrylic. It is however limited to these materials and other commmon materials are unsafe to cut due either to fire or chemical hazard.

Before you begin, please review the IDeATe@Hunt Laser Cutter Policy. You are responsible for understanding and following all details of the policy.

Instructions for preparing design files to cut can be found below under Laser Cutter Files. The general instructions for operating the cutter can be found under IDeATe@Hunt Laser Cutter Procedure.

General information on the cutters can be found under IDeATe@Hunt Rabbit Laser Cutters. Materials available for puchase at the desk can be found at the IDeATe@Hunt Material Inventory.

Dave Touretzky’s lecture slides for the laser cutter from the 15-294 Rapid Prototyping mini-course are an excellent walk through the whole process.

3.5.1. Process Overview

Laser cutters are intrinsically two-dimensional tools: a focused beam of infrared laser light (e.g. invisible to the human eye) moves on an XY gantry under computer control to trace out curves and lines. The beam is turned on and off to start and end lines during cutting. It may also be used in a raster engraving mode in which it sweeps an area while modulating the beam power very quickly to vary the cut and create an image on the surface.

The fundamental cutting process is melting or burning from the heat resulting from absorbing the energy of the light. An air jet blows downwards into the cut area to help move melted material out of the cut before it resolidifies. The cutter bed can be moved up or down prior to cutting to place the top plane of the flat material at the focal point of the laser.

3.5.2. Laser Cutter Files

The most up-to-date hints for preparing files is included in the guide offered by the Rapid Prototyping Technologies course under 15-294 Rabbit Laser Instructions.

A printed copy may also be found in a binder in the laser cutter room, or can be read on a browser on the laser cutter station computers.

3.5.3. File Formats

The best format for a cutting plan drawing is DXF with millimeter units and 1:1 scale. The key rule is that every line on the drawing will create a cut in the material, so make sure there are no stray marks, text, annotations, frames, or labels. These files are 2D drawings, so can be generated from drawing programs such as Inkscape or Illustrator, 2D CAD programs such as DraftSight, or 3D CAD such as SolidWorks or Rhino by creating the appropriate 2D drawing outputs.

3.5.4. Design Rules

The typical kerf in thin acrylic can be 0.005 to 0.010 inches and is slightly tapered, so parts typically are slightly smaller than the designed form and the edges are not perfectly square.

Even though the parts are flat, complex 3D structures can be created by using tabs and slots to connect part edges to part faces.

For other hints, see CAD/CAM Resources.

3.5.5. Best Practices

  1. If the laser cutter catches on fire, use the Carbon Dioxide fire extinguisher (CO2 for Class C fire) located nearby. This is very short-range: the nozzle will need to be approximately over the machine.
  2. Small flames in cardboard can usually just be blown out with your breath. Even acrylic can sometimes generate a brief flame. Never use polycarbonate, it will burn.
  3. Thick acrylic cuts can tend to re-fuse, so it is best to remove your parts promptly from the cutter and use a tool to press out all the small pieces. Careful, acrylic is brittle and can crack.
  4. Be sure to wash your hands after handling freshly cut acrylic, it leaves a residue.

3.5.6. Errata

  1. The instructions refer to checking the “equipment room behind the laser cutters”, but that door is generally locked with physical key access only.