Trigger mechanism design in power hand tools is of great importance for communicating with the operator and for providing feedback on operational functioning. Therefore, for a successful power hand tool design, knowledge about how the trigger mechanism feels is required.
This study aims to define and investigate the design factors related with trigger tactile feeling for electrical right angled nutrunners. A Kansei Engineering (Affective Engineering) study has been conducted for a comparison between users´ (operators that work at an automotive assembly plant) and product developers´ (product development group of a power hand tool manufacturer) to find common and differing semantic expression dimensions for that. 124 Kansei words (descriptors) were collected from literature, interviews and workshops. These words were reduced to 52 by affinity analysis and evaluated by operators and product developers using semantic differential technique.
From the operator group`s responses six factors (explain 87% of variation ) were extracted as, “professional performance”, “safety and tactile feeling”, “usability”, “smooth operation”, ”communication and durability”, “convenient and comfortable” to define trigger feeling. Correspondingly, five factors (explain 89% of variation) “robust and appealing”, “ergonomics and operator performance”, “controllability and predictability”, “creativity and modern” and“powerful” were distinguished for the product development group. Results showed that the start phase and especially quick start of trigger mechanism is more important to operators, while end feedback is more important to product developers. Soft start of the trigger is correlated with ergonomics, optimal, clear operation and performance for product developers while soft start together with end feedback are associated with well-built, convenient and safe trigger characteristics for operators. According to the results from average ratings the Kansei word “ergonomic” has been rated as the most important descriptor for trigger feeling together with “user-friendly”, “easy to use”, “long life time” and “comfortable” for both groups. By developing a questionnaire using the factors and variables identified; this questionnaire can be used to assess views of operators about trigger functioning and to know how do operators feel about new types of trigger mechanisms.