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Long Run Diecasting Tooling - It Pays to Pay More!

Tool amortisation cost is critical

Where long production runs are concerned, tool amortisation costs can make a major difference to profitability. Because the cost of tool steel is a relatively small element in the total cost of tool production, the cost/benefits of improved material technology can be dramatic. Typically, a 20% increase in units produced from a given tool will justify an increase of around 500% in material cost but can probably be achieved by an increase of perhaps 100%. Diecasters should take great care to specify the optimum material to be used for tooling.

The table below relates unit production to tool costs. Compared with the base case where the tool manages 50,000 units at a tool amortisation cost of £2.00, a 10% increase in output to 55,000 units resulting from improved tool steel quality justifies a threefold increase in the value of the tool steel (from £4,000 to £12,000). In most cases, this 10% improvement would be expected from a much lower material cost increment. Experience with the latest "super quality" diecasting steels such as Carrs TQ1, suggests that improvements of at least 20% are readily available with the likelihood of significantly more to come.

Extended production runs are not the only benefits

Using higher specification material for tooling will provide two further benefits over and above extended production runs.

• Much greater resistance to heat checking will ensure that the integrity of the working surface remains good for much longer. This will improve product quality and avoid sticking.

• The improved toughness of the steel will dramatically reduce the risk of gross cracking arising from production or design problems.

The steel quality ladder

It is often not realised that specifications such as BS4659 BH13 (now replaced by ISO4957 40CrMoV5-1) are, broadly speaking, only specifications for the chemical analysis of the material concerned. Quality enhancements that will make a vital impact on the performance of the material are dependent on a much wider range of considerations.

Quality	Optimisation of all aspects		Carrs TQ1 “Super Quality”
	Inspection		Rejection of sub-standard material
	ESR Secondary refining		Extra clean and homogenous material
	Bar heat treatment		Consistency through section
	Sound forging practice		Optimum grain flow and structure
	Ingot stage heat treatment		Homogeneity & grain size
	Adequacy of the steelmaking		Avoidance of inclusions and voids

The first six enhancements (from bottom up) are applied to the standard tool steels such as X40CrMoV5-1 (H13) and X37CrMoV5-1 (H11) to a greater or lesser extent but over and above these; there are new "super quality" diecasting steels such as Carrs TQ1. These materials are produced to an entirely new and exacting metallurgical specification that is designed to produce the best possible performance. When long production runs are needed it is this specification that should be selected. OK, so it costs considerably more than the standard material, perhaps double. But in widespread production across the EC and elsewhere, tool life increases of at least 20% have been reported and, in all these cases, the tools are still in use and showing little or no degradation.

Partnership in material selection

Given the importance of the selection of the correct material for tooling, it is surprising that there is so little attention paid to it. Ideally, the diecaster, selected toolmaker, heat treater and tool steel supplier should discuss and agree the most appropriate material for the job at an early date. This is particularly true of larger and more exacting tooling.