The operation has timed out.

This error come when we try to access a web service method and this method takes more than 2 minutes to response. Because IIS default timeout is 120 seconds.
To resolve this problem set the web service timeout at runtime
as below....

SheetCuttingWebService.Service objWeb;
objWeb = new UserInterfaceLayer.SheetCuttingWebService.Service();
objWeb.Timeout = 3600000(mili seconds);
dsPlate = objWeb.GetPlates(origin_id, specification, length, width, thickness, do_number, heat_no, plate_no, drawing_no, certificate_no, percentage_free, balance_wt, order_by_column, user_id, plate_id, reqLengthFrom, reqLengthTo, reqWidthFrom, reqWidthTo, IsDiscarded);