A Ladbrook volume stamping contract to produce a simple mild steel cleat for a tinplate paint can manufacturing company proved to be a challenge. Impending European legislation called for can handles to be fastened on to the outside of the can instead of the usual practice of inserting two rivets through two holes to be peened over on the inside of the can.
Production requirement was for 70 cans per minute complete with assembled handle and two cleats from each assemble and weld unit. Projection welding was deemed possible at the outset and would be the can companies chosen method of fastening to be investigated.
An order for the design and production of a single stage progression tool was placed with Ladbrook and 10,000 prototype cleats as illustrated were produced. Some two years later after experimental welding by the can company was complete. The feasibility of producing the smaller cleat illustrated was discussed with Ladbrook.
The principle of Projection Welding is based on a good flow of electricity from the cleat to the outer surface of the can. Four points on the cleat were deemed suitable for providing the contacts between it and the can. It was found that the points needed to be of constant sharpness to create a good electrical contact for the projection welding process. The resistance to electrical flow offered at the four points generates heat to melt them and thus fasten the cleat to the can. Ladbrook provided a novel press tooling solution to maintaining the sharpness of points resulting some five years later in an order for two progression tools for continuous production of one million cleats per day automatically counted and packed in 10,000 lots in to automatically handled perforated stainless steel degreasing cassettes at 7 minutes per cassette. See illustration of scrap strip which produces five components per blow.
Full production started some months after the first tool was commissioned to enable the can company to commission the two assembly machines which would simultaneously produce a can handle from plastic strip which would be precisely presented to the assembly and welding head to unite with the tinplate can and two cleats.
Whilst the cleat was seemingly an insignificant component part when compared to the multi million pound investment in the prototype assembly & welding machine and subsequent two production machines, the speed and small size of the cleat called for some very demanding tolerances for successful feeding and placing of the cleat in the assembly process. The Bruderer 25T High Speed Press was fitted with numerous devices to monitor the five separate components. Finite analysis was used in the inspection process. Ladbrook maintained continuous production of this product for some four years. Tooling performance was continuously improved with the application of modern coatings on the punch and die cutting edges and continuous improvements in die cutting configurations and maintenance.