Comparison of command language and direct manipulation interfaces for CNC milling machines

Abstract

Abstract This paper reports a human factors study comparing the usability of command language and direct manipulation interfaces for computer numerically-controlled (CNC) milling machines. The operator-machine interfaces were assessed in terms of task completion time, operator retention of training knowledge, and subjective preference judgements. Four factors were manipulated in the study: (1) work session (two sessions separated by a one week interval); (2) level of operator expertise (novices and experts); (3) programming task (copy and modify); and (4) trial number. The one week interval between work sessions degraded task completion time for the command language interface, but not for the direct manipulation interface. Moreover, operators knowledge of CNC programming was retained better with the direct manipulation interface as compared to the command language interface. Additionally operators' subjective ratings indicated a strong preference for the direct manipulation interface rather than the command language interface across several categories of usability attributes.