Analysis of Assembly Variation by Positioning Between Two Parts using a Hole and a Slot

抄録

This paper discusses the assembly variation that may arise when the positioning between two parts is constrained using a hole and a slot to fit over two locators. This method of controlling mating parts is called “positioning”. Two parts positioned using a hole and a slot fitting over two locators may move relative to each other during assembly because of slight clearances between the locator-hole pair, and/or between the locator-slot pair. The relative motion of two parts using this positioning might simply be considered to be small rotations about the locator-hole joint. However, in many cases, equal locator-hole and locator-slot clearances are toleranced, resulting a motion which is more complex than simple translation or rotation. This paper addresses the motion area that is obtained by positioning using a hole, a slot, and two locators. When the assembly is defined with nominal inter-locator distance of L and locator-hole and locator-slot size clearances of 2δ, the motion area of an arbitrary point (X, Y ) is explicitly described. The motion area corresponding to (X, Y ) is all coordinates (x, y) such that x = 2δ {Y/L(sin θ + 1)+ cos θ }, (tan θ = Y/L), y = 2δ (X≦L), y = 2δ (2X/L-1) (X＞L). This paper presents a tolerance analysis application using the above.