Accuracy of Setting Work-pieces on Automatic Lines with Pallet-fixtures

Abstract

The accuracy of positioning surfaces to be processed on automatic lines with pallet-fixtures essentially depends on the setting error of the pallet-fixtures with work-pieces in ready-to-work position.

The applied methods for calculating the setting error do not give a complete picture of the possible coordinates of the point when in the pallet is displaced in different directions.

The aim of the work was to determine an accuracy of the setting work-pieces on automatic lines with pallets-fixtures, using a computational and analytical method, to improve a manufacturing precision of parts.

The currently used methods to calculate the setting error do not give a complete picture of the possible coordinates of the point of the pallet displacement in different directions. The paper offers a method of equivalent mechanism to determine all the variety of options for displacements in the horizontal plane with a diverse combination of angular and plane-parallel displacements.

Using a four-bar linkage, as an equivalent mechanism, allows us to define a zone of the possible positions of any point of the work-piece pallet platform, as the zone bounded by the coupler curve. In case the gaps in the nodes of the two fixtures are equal the zone of possible positions of the point in the parallel displacement of the platform is determined by the circumference and at an angular displacement by the ellipse.

The obtained analytical dependences allow us to determine the error at the stage of design with the certain gaps in the fixture nodes.

The above method of calculation makes it possible to define a zone of the appropriate placement of the work-piece on its platform for the specified parameters of the pallet to meet conditions for ensuring the coordinate accuracy of the processed axes of holes.