The 41-tonne unit, to be bolted atop a Sydney high-rise, is the largest built by Farra in the past 15 years.
The engineering specialist has designed and constructed almost 100 similar units during the past 30 years.
Project engineer Ken Hill has been putting the massive unit through trials this week, before it is disassembled for delivery to Sydney.
He said while Farra did not come up against any unusual technical difficulties in the construction, it "took some time and working out" to ensure the two-person hanging basket could access the entire building.
"It’ll rotate through 360 degrees, covering the entire building [facades]," Mr Hill said.
The unit is driven by six electric motors and one hydraulic, which drive the arm extension, cables and rotation, of which 8.5 tonnes is the counterweight.
The unit has an extended reach of 33.42m and rotates 360 degrees to give access to all facades of the high-rise, a 33-storey new-build high-rise at 60 Martin Pl, Sydney.
The building itself is a new $A290 million ($NZ304 million) commercial property constructed by Lendlease Corporation, started in November 2017 and due for completion in August.
The building is unusual in that on one side, the first few floors from ground level are concave, so that a neighbouring church has the high-rise looming far above its roof line.
From the basket’s lofty perch, workers will be able to undertake retro-work, window cleaning and maintenance of any other facade.
One of two tower cranes on site will lift the unit, in pieces weighing up to 10 tonnes, on to the building in March, for reassembly in April, which will be overseen by at least two Farra staff.
The basket and its twin-stay cables of 8.4mm can take a total weight of about 2.5 tonnes, giving it a "nine-times" safety factor, Mr Hill said.
"There’s a number of rope [wire cable] restrictive systems for the safety of the cage," Mr HillFarra chief executive Gareth Evans said Farra was at present bidding on larger maintenance units, but for confidentiality reasons, could only say two more contracts for larger units could be secured by this time next year.
