Utveckling av blindnittång : med avseende på kraftåtgång, greppbredd och omtag

• Main Authors: Parsmo, Pontus, Blomqvist, Jonas
• Format: Others
• Language: Swedish
• Published: Tekniska Högskolan, Högskolan i Jönköping, JTH, Maskinteknik 2018
• Subjects: nitning; blindnittång; hävarm; handverktyg; kraftreducering; Other Mechanical Engineering; Annan maskinteknik
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-40827

For three years, Isaberg Rapid AB have acquired rivet pliers in their range of products, Rapid have seen a potential in developing rivet pliers and have therefor combined an exam work that will investigate the potential and attempt to find a solution to three given problem areas. The primary purpose of this study is to reduce the force needed when using rivet pliers for riveting, which is done to reduce injury on muscles and joints that can occur during heavy and repetitive work. The primary purpose has been given two subordinate purposes which are desired to be solved without violating the primary purpose. The first subordinate purpose is to reduce the number of re-grips that the plier needs to make about the rivet pin, the second subordinate problem is to reduce the gripping distance between the handles to encourage one hand usage.   To answer the research questions of this study, the work has been performed in three steps, which are problem identification, problem solving and lastly verification of solutions. The problem identification consisted of a pilot study and a product specification, which provided a foundation for the work, gave understanding and defined the problem. In the pilot study, an analysis of the products features and mechanics, a market research and a survey were conducted. The product specification was formulated based on the requirements provided by Rapid and from this a functional specification was created. The second step, problem identification, consisted of concept generation and concept selection. The concept generation method used was a variant of brainstorming, which was the basis for the subsequent concept selection phase. The concept selection was performed with Pahl’s and Beitz’s elimination matrix and this matrix was used to eliminate the concepts and indicated which concepts that supposedly meets the requirements for further development. The concepts that was not eliminated was designed further and was evaluated with Pughs decision matrix and Kesselring’s criterion weighting method. From these two, concepts were obtained that most advantageous meet the requirements. Further on, calculations were performed based on the theory of leverage principle on the concept and this was done in order to theoretically determine the force exchange. To enable a verification of the solution, 3D printed prototypes were made to provide feeling and a first confirmation that the solution has potential to solve the problem. Later, a prototype was made by a milling machine to enable a force measurement, which was not possible with the 3D-printed prototype. To answer the research questions, this study reports two concepts together with theories. One of the concepts has a solution that reduces the force needed to use the plier, increases the force exchange and reduces the grip distance based on theories.  According to the calculations that was performed, the increased force exchange shall result in a lowered force by 24 % that is needed by the user to perform riveting.  The measurements performed on the prototype made by the milling machine, showed a reduced force value, but these values did not match the calculated values. The reason to why the values didn’t match is thought to be the friction.  Further development was needed on the concept to enable a verification of the force and before this development it is considered not reasonable to reject the concept. The friction is thought to be lowered by designing an insert and a new fastener.  In the study it was also discovered that an increased force exchange to reduce the force needed by the user to perform, could result in a reduced stroke length. The second concept was created to reduce the number of re-grips that the plier needs to do about the rivet pin. This concept is considered a solution to the problem but could counteract the desired force reduction and is therefore considered not to qualify for further development as the previously mentioned concept. The three research questions cover three different problems and it was discovered that the solution to these counteracts each other.  The delimitations of this study were made to one of Rapid’s rivet pliers with non-rotating heads to enable focus on the mechanics and shape of the product. The potential improvements and development performed on one of Rapid’s rivet pliers are intended to be applicable to other rivet pliers with same features and function.