Case Study : Magazine System for Robot Assembly

This is a  design proposal that I was asked to carry out for a Swedish world leading manufacturer of compressors, generators, construction and mining equipment, industrial tools and assembly systems.  They required a magazine system to present end-pieces for the pre-assembly of pneumatic cylinders.

The second stage for the robot assembly of pneumatic cylinders involves the sub-assembly of end-pieces and half-pistons.  End-pieces need to be handled by a magazine system because they are too large for conventional vibratory feeders.  A magazine system is required at the pre-production facilities that is a scaled-down version of the future production system, within budget limitations.  The cost of the system is split between the fixed cost for the transfer of parts to the robot and the variable cost of end-piece storage.  The variable storage cost is proportional to the capacity of the magazine system. There is also an indirect labour cost for the filling and transport of magazines, in addition to the equipment material cost. The prototype can have the same transfer device as the production model, but with a smaller capacity.

MAGAZINE FILLING

The only economical method of magazine loading is to fill them at the point of final manufacture. This is because the time taken to insert a part into a magazine can approach the time taken to insert it into the part-built assembly.  Nevertheless, end-pieces have to be transported from manufacture to assembly and magazines are the best way of doing this, whilst also giving protection to the surface finish.

MAGAZINE CAPACITY

The capacity of the magazine is as large as possible to achieve the minimum number of journeys from manufacturing to assembly during the shift.  If demand for each cylinder diameter is equal then the magazine must contain in excess of sixty parts for a refill only once a shift.  A single vertical stack magazine would be in excess of three metres high. It is therefore proposed that a number of units should be combined to form one magazine. Three magazines of twenty end-pieces seems reasonable.

PROPOSED SYSTEM

The system shown is one method of end-piece distribution. The illustration shows one magazine to store one style of end-piece.  The production version for the Swedish manufacturing plant would have three magazines per end-piece, each behind the another.