CrystalDecisions.CrystalReports.Engine.ReportDocument report = new CrystalDecisions.CrystalReports.Engine.ReportDocument();
string repName = string.Empty;
repName = CrystalReportSource1.ReportDocument.FileName;
report.Load(repName);
report.PrintToPrinter(1, false, 0, 0);
It will send your report document direct to the printer without seeing it.
Hope it will help...