Home†††††††††† Introduction††††††††††† Team 09F†††††††††††††† Analysis of original††††††††††† Analysis of redesign ††††††††† Fatigue Testing†††††† Technical Article††††††††††††† Final Report †††††††††† Email
C. J. Winter is a world-class machine product vendor that supplies thread forming equipment to machine industries.† A 234SA is a rotary radial threading attachment that is designed to fit into one station of a Hydromat 12-station rotary transfer production machine.† A 234 slide arm within a C. J. Winter model 234SA thread rolling attachment has failed in service.† Through various engineering diagnostic methods, C. J. Winter has determined that the Von Mises stresses in the area of fracture exceeded the maximum allowable stresses in the slide arm.† Our task is to analyze the current design, and propose a redesign that is guaranteed not to fail under normal operating conditions.† The redesign will be used in the existing attachment and may be scaled up for larger attachments.† In addition, we are required to develop a new test fixture, or modify the existing test fixture to allow for repeatable testing of production slide arms.
Note: There are two die axle holes; the base consists of the
block of material containing the two threaded holes; the head is the major portion
of the part containing everything surrounding the pocket except for the sliding
A single 234 slide arm failed in service at a C. J. Winter customer site.† The 234 slide arm is a single part within a 234SA rotary radial threading attachment.† The purpose of each of the two slide arms within the tool is to hold one roller thread die.† Each die is aligned with the other within the 234SA by an alignment chain to prevent thread mismatch on the part.† There is a thick outer ring surrounding the tool.† The ring contains two internal ramps oriented axially, and each ramp coincides with one of the two slide arms contained within the assembly.† The outer radius of the slide arms is designed to clear the inner diameter of the outer ring.† The entire 234SA attachment spins continuously during threading.† As the outer ring is advanced axially by an air cylinder, the ramps press on the roller and pin.† This forces the two slide arm heads, and therefore the roller dies, together around the unthreaded part stock.† The part stock is threaded as it is pinched between the two roller dies.† Once the part is threaded, the air pressure is released, each slide arm returns to its starting position, and the threaded part stock moves on to the next station of the Hydromat machine.† A video of the 234SA rotary tool in action can be seen at C. J. Winterís web site.
In an attempt to prevent future failures, C. J. Winter immediately contracted slide arm destructive testing to IMR test labs.† Two production arms were sacrificed for mechanical destructive testing along with another slide arm that was completely machined from a block of steel.† IMR labs built a makeshift compressive testing fixture to fit an Instron frame with the intent of breaking the slide arms.† The two cast arms failed, and the machined arm showed signs of imminent failure beyond the capabilities of the Instron frame.† This preliminary data, the three sacrificed arms, as well as a new production arm were presented to us at the introductory meeting.† A Finite Element Analysis report of the current design was also presented.
© 2003. Rochester Institute of Technology, Senior Design Team 09F. All rights reserved.