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How to Create Screw Threads in Pro Engineer

written by: Suvo • edited by: Lamar Stonecypher • updated: 8/26/2010

Pro Engineer has made life simple for the designers of fasteners fields: a special sweep command called helical sweep is available for all sort of threads.

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    Helical sweep is extensively used option in pro engineer for making protrusion or cut outs for screw threads. This option could also be used for making coil springs.

    Like sweep, helical sweep also needs to have section and trajectory. But, here you need not to directly sketch the helical trajectory. Instead pro engineer got the helical trajectory from the surface of revolution and the pitch. Surface of revolution defines the distances between centre of threads and the axis of revolution.

    Creating helical sweep

    Go to insert>helical sweep, you will find the helical sweep dialogue box opened.

    Here the following attributes needs to be defined:

    Constant: choose this attribute if you are going to model for constant pitch.

    Variable: Here the pitch will be variable and will be controlled by a graph. By default the graph will be having two control points but if you want some more control points in the graph, you have to add it while sketching the trajectory.

    Through axis: If you wish to pass the plane of the cross section of the profile through the axis of revolution, then go for this option.

    Normal to Traj: Here the cross section of the threaded geometry remains normal to the trajectory or the surface of revolution.

    Right handed: The threaded geometry will be following right hand direction, means if you place your right hand thumb towards the axis of revolution then the direction of the remaining fingers will show the thread direction.

    Left handed: The direction threaded geometry will be following left hand rule.

    In the helical sweep dialogue box, you need to define the trajectory and the section now. The trajectory must be open type of geometry. Pro engineer will consider the surface created by revolving the trajectory as surface of revolution of the threads. Make sure that you have sketched a centerline; abut which the threads will be revolved. You can draw any shape of profile, provided it is open and tangent at any point is not normal to the centre line.

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    Example

    Suppose you need to create a coil spring, whose surface of revolution is at inclination of 10 degrees with the axis of revolution and pitch at starting point is 10, at mid point is 15 and at the end is 20. The dia of the cross section is 10.

    For modeling this spring, go to insert>helical sweep select the variable, through axis and right handed respectively.

    Now while sketching the trajectory make the angle of 10 degree and add a point at the mid of the trajectory. Sketch the cross section of dia. 10.

    While defining the pitch, add the middle point and give pitch values as 10, 15 and 20 for the three points respectively.

    While working with helical sweep cut you may experience failure due to the material removal side selection, please take care about that.