Original commitment was made in good faith following successful previous production of tubes with yield rate running at approx. 75% work was scheduled and process launch with this yield rate being allowed for. Following a face to face review in week 20 (after initial mandrel failures) It was agreed that securing the furnace qty in July was to take precedent over the 68 for spares and schedules were switched to leave the 68 until wk1 sept. Following the poor yield issues it was necessary to use the 68 qty in order to complete the 308 required for the furnace these were pulled fwd to complete the 308 one week late. Distribution route then caused a further slippage. Revision 2 the extrusion run to produce the qty 68 ran week 33 but broke the extrusion stem. This extrusion run was completed week35, with 4 weeks manufacturing time this creates a delivery date of week39.