Robot decimates wheelchair assembly time

Citation

(1998), "Robot decimates wheelchair assembly time", Industrial Robot, Vol. 25 No. 6. https://doi.org/10.1108/ir.1998.04925faf.006

Robot decimates wheelchair assembly time

Robot decimates wheelchair assembly time

Keywords Robots, Welding

When wheelchair frames at Quickie Designs were assembled by manual brazing each assembly could take up to 45 minutes. Changing to robot welding slashed assembly time to just 3 minutes (see Plate 5).

Based at Avon Lake, Ohio, Quickie started producing a new design of lightweight steel and aluminium chairs in 1991. In the first year of production eight workers produced 2,500 wheelchairs.

By 1993 production had risen to around 18,000 annually and director of operations, Ken Murphy realised a radically different approach to manufacture was required.

Plate 5 A robot welding cell assembling wheelchair side frames at Quickie Designs, USA

He approached Trico, a distributor of Fanuc Robotics with his problem, which he summarised as "We needed a robot to weld small diameter tubes with wall thickness of 0.049 to 0.065inch. In addition the robot would be required to manoeuvre around tight corners when welding chair joints".

The solution proposed by Trico was welding cells based on a Fanuc ArcMate 100 robot and Lincoln Electronic welding set. To simplify operation, Fanuc ArcTool application software is used to programme the robots. Currently three welding cells have been installed and a fourth is in the pipeline.

Each cell has a rotary index table so that load/unload is taken out-of-cycle. Two cells produce side frames from six components and sub-assemblies as well as foot rests. The third cell takes two side frames and foot rest assemblies from the other cells to complete the wheelchair structure.

Operators who previously manually brazed assemblies now load fixtures on the rotary tables.

After welding, the operator inspects each weld for cosmetic quality. Reject rate is less than one percent and most rejects only require a minor manual touch-up.

Overall the change to robot welding has dramatically increased cosmetic quality. To ensure structural quality, Quickie performs destructive tests on randomly selected samples three times a day.

By 1997, production had risen to 45,000 wheelchairs annually. It is estimated that 45 manual brazers working on two shifts would be required to achieve the same output as the three robot cells.

This provides an incredibly short time to recoup the capital investment. Each cell costs around £60,000 with tooling, plus £12,000 a year for the operator, when this is set against 15 annual wages of £12,000 it shows a payback of well under six months.

For further information contact Maurice Hanley, Fanuc Robotics (UK) Limited, Seven Stars Industrial Estate, Wheler Road, Coventry CV3 4LB. Tel : +44 (0)1203 639669; Fax: +44 (0)1203 304333.