I have a stand up freezer which keeps forming large icicles around the door. i have defrosted it twice and it continues to ice up
Sounds like you may need a new door seal.
Check/clean the seal.
Refrigerator Repair Guide: How to Check the Door Seals - ACME HOW TO.com
Check that the door closure ramp ( Item 36 in Section 2) is OK.
Sometimes the seal will grab on the hinge side when closing, a light coating of petroleum jelly or white lithium grease will prevent this.