Spring 2009

Surface Junction Boxes

Picture of PSL's Mike Hughes spot welding a junction box
PSL's Mike Hughes spot welding a surface junction box.

PSL is responsible for production of all surface junction boxes required for the IceCube Project. The boxes provide connections for power and signal cables above each vertical string of 60 digital optical modules, with electromagnetic shielding and mechanical protection against personnel and the elements. Brian Pechan had performed the initial design (and first redesign) and coordinated prototyping of a few boxes incorporating custom machined cable clamps, for the first couple of module strings installed plus test systems, training or spares, at PSL and at the South Pole. After Brian left PSL, Ken Kriesel was assigned responsibility for the boxes. The design was refined and extended regularly to improve cost effectiveness, incorporate tethering of attached tools, and improve safety, fit and finish. Glen Gregerson ably provided drafting in SolidWorks® throughout.

Initially enough boxes were built each year for the following polar installation season, while refining the design as each year’s experience indicated. In effect, there are a few “model years.” Following the initial prototypes, in 2005 PSL made 14 boxes. These boxes were spot welded with very occasional TIG rework and included several custom designed formed sheet metal cable clamps. Production rate exceeded expectations, peaking at 5 boxes welded per day. Tools, supplies and spare components were put on pallets and stored in the warehouse until the next year’s run. Eight strings and their boxes were deployed, matching the project’s schedule target. The boxes were revised to eliminate remaining sharp corners and reduce the occurrence of tether tangling.

In 2006 with the final box design revision completed, checked and approved, components for the remaining production quantity were ordered. Preassembly of components on hand for remaining production was also performed. The weld process was changed from spot welding to MIG after qualification on the first boxes of the 2006 batch, yielding higher production rate and lower rework. Then PSL built and crated 12 boxes shipped for the 2006-07 installation season, followed by the remaining 55 boxes starting in December 2006, with the production completed in March 2007. The last 55 boxes will be shipped from warehousing at PSL to the South Pole as needed.

The PSL instrument shop staff did great work as usual throughout this project. PSL also made significant use of subcontractors including Entwistle and Middleton Machining to produce superior sheet metal parts at a good price. The production team also included UW IceCube employees (Jason Krause, Mike Kleist, Jim Baccus and others) and Bit7 employees who were a pleasure to work with.

 

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