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Firstly to understand how perforated metal is quoted, me must learn the manufacturing techniques used to produce perforated metal. A common method requires the use of a CNC punch press. CNC punching involves a set of clamps that hold a flat sheet of metal. The clamps move the sheet rapidly along an X and Y axis. As the sheet moves, a ram forces a tool into the sheet which in turn punches a hole through the material. This works in a similar way that a hole punch is used for punching holes through a piece of paper.
To punch a 10mm diameter hole for example into a piece of metal, multiple factors have to be considered. The main one is the use of tolling. For each different material grade and thickness of material, a different tooling setup is required which needs to be manually setup by the machine operator.
Once the tooling is set, the speed the machine runs is calculated in Hits Per Minute (HPM). Newer punching machines can run anywhere between 800 – 1200 HPM whereas older machines are closer to the 200 HPM mark. The distance between the holes (pitch) also affects the rate of the machine as tighter pitches with holes closer together tend to run at a faster rate as there is less travel distance for the sheet between each hit.
Although a machine may only be able to achieve 200 HPM for a set pattern, this does not restrict the amount of holes each hit produces. Many perforation companies use cluster or multi-punch tooling to increase the speed parts are manufactured. A cluster tool is a single punch tool consisting of multiple individual tools. For example if we wanted to produce a perforated sheet with 5mm diameter holes, at a 8mm staggered pitch, a cluster tool for this particular pattern can be installed into the machine with 10 individual 5mm diameter punch tools within it. This would mean the machine is technically still running at 200 HPM but each hit is now producing 10 holes instead of one.
Although cluster tooling is beneficial, it has certain drawbacks. The first one is the cost. Cluster tools can be 10 – 20x more expensive than regular single hit tooling, meaning large initial quantities of each part are required to make the use of the tool cost effective. Each tool is restricted to one particular pattern meaning the initial outlay of the tool is required for each individual perforated pattern available.
When quoting perforated parts, the main cost is usually the price of the raw materials. This often comes in sheet form. The sales engineer needs to take into technical considerations such as the space required between each part on the sheet and also any free area at the bottom of the sheet for the clamps on the machine to grip from.
