This part of ISO 27547 specifies the general principles of test-specimen preparation using mouldless techniques. Sometimes, these techniques are called “tool-less” methods. Common to all these techniques is the fact that the specimens are produced layer by layer. The shape and dimensions of the specimens are defined in terms of a numerical description using CAD techniques. This computer model of the specimen is “sliced” into layers by means of suitable software. The specimen-preparation process then builds up the specimens automatically, layer by layer, using the computer model and a suitable computer-controlled laser-sintering machine. The three software systems used (for CAD, slicing the specimen into layers and machine control) may be independent systems interfacing separately with the machine or they may be integrated with the machine. This part of ISO 27547 also specifies the general principles to be followed when test specimens of thermoplastic materials are prepared by laser sintering. The laser-sintering process is used to prepare specimens layer-wise by sintering the particles of a thermoplastic powder using the energy of a laser beam. This part of ISO 27547 provides a basis for establishing reproducible sintering conditions. Its purpose is to promote uniformity in describing the main parameters of the sintering process and also to establish uniform practice in reporting sintering conditions. The particular conditions required for reproducible preparation of test specimens which will give comparable results will vary for each material used. These conditions shall be as given in the International Standard for the relevant material or shall be agreed upon between the interested parties.