TECHNOLOGY OF BROACHING – RESEARCH OF THE ROUGHNESS AND MACHINE CAPABILITY

The work deals with the technology of metal machining with a focus on the technology of broaching the internal shaped surfaces. The design of the drawing tools is a tool with several cutting edges, whereby the final shape of the inner shaped surface is made for one rectilinear movement of the tool. The cost of broaching tools is higher. For these reasons, the broaching technology is suitable for series production. One part of the paper covers the research of the achieved roughness of the internal grooves when changing the cutting environment, an emulsion was used instead of oil. The second part involves the use of statistical methods in the technology of broaching internal contoured surfaces. The research is focused on the machine capability. The results of measuring the accuracy of the tolerated dimension of the inner holes after broaching are used as input values to this statistic.

Objective and subjective evaluation of a new airplane seat with an optimally pre-shaped foam support

BACKGROUND: Aircraft seat manufacturers are making efforts to reduce seat weight while continuously increasing seating comfort. OBJECTIVES: To verify if seats with an optimally pre-shaped foam support could improve seating comfort while reducing seat weight. METHODS: The optimally pre-shaped surface was obtained from a synthesis of 95% of individually optimized compressed seat pan surfaces of a target population. Two new seats were proposed with two different cushions, one slightly softer and the other harder. Nineteen differently sized volunteers tested the two new seats and an existing seat randomly. After an assessment of initial discomfort, participants were instructed to watch a TV series for 50 minutes. A same questionnaire was used to assess both initial and longer-term discomfort. Contact forces and pressure distribution were analysed as well in-chair movements (ICM) during sitting. RESULTS: The two new seats exhibited lower shear, lower peak pressure and larger contact area on the seat pan as well lower number of ICM during the 50 minutes sitting. They also had lower initial overall discomfort, though significant differences between the seats were not found after the long sitting. CONCLUSIONS: Properly pre-shaped surface could be used as foam support to reduce the amount of foam while reducing seating discomfort.

Kinematic calculation and plotting of lifting height and speed of the tangential cam pusher using MATHCAD program

The article shows the design features of tangential cams with a rounded top, provides a method for determining the lifting height and speed of the pusher when the roller is rolling in a straight line and in contact with the actual profile of the cam. The formulas for the kinematic calculation of the tangential cam are refined taking into account the radius of the initial circumference of the shaft, the radius of the rounding of the cam tip and the value of the radius of the pusher roller. Calculations are given to determine the stroke and speed of the pusher when the roller is rolling on the sections of the straight and arc-shaped surface of tangential cams with a radius of rounding of 6 and 10 mm. Formulas are proposed for determining the lift of the pusher in the rolling section of the roller along the radius of the cam tip at a constant coefficient λ = 1 and λ = 1,5. Using the Mathcad program calculations are performed and combined graphs of the pusher lift and the change in its speed are constructed for two types of tangential cams