What is in this article?:
- Improving Cost Estimating for Metalcasting
- Drilling down into casting cost details
- Quantitative methodologies
- Calculating every aspect
- Eliminating guesstimates
- Labor, materials, setup, tooling, energy
As in much of manufacturing, the casting industry is in a state of flux with competition keen and producers fighting for precious contracts. OEMs and other primary component-makers using casting remain deeply interested in best cost and delivery. But as the stakes ratchet up, there is growing evidence that future success lies in the willingness of suppliers—be they larger foundry operations or smaller investment, sand, and die casting shops—to bring extra value to the quoting process and the supplier-customer relationship.
Over the years, casters have adopted a variety of practices for determining the cost of parts. A number of successful foundries and diecasters use detailed in-house spreadsheets that mirror their manufacturing processes and are built on quantified historical knowledge collected over years of practice. Many others, however, use a more subjective approach that relies on “general rules” and approximations, which simplify, or may even overlook, important factors such as setup labor, energy overhead, and tool wear.
We’ve all seen how reliance on inexact costing methods can lead to misquoting and undesirable consequences. For example, inflated bids—created to cover unknowns—can result in unnecessarily high quotes and lost business. Underbidding, which is also common, may produce wins but hurt the organization in the long run by bleeding its bottom line. Given the current competitive climate and basic business realities, there’s no room for sacrificing potential work or profit.
Negative outcomes can be avoided if the “black art” of costing is replaced by more quantitative methodologies: One design-for-manufacture approach is DFM Concurrent Costing, a software tool developed by Boothroyd Dewhurst, where I am R&D manager. Using this systematic, science-based DFM method, casting operation managers/owners are able to generate extremely accurate piece part and tooling cost estimates for designs that come “as is” from OEMs, or are modified by the casting house to show improvements.
Putting DFM into practice
Every design project starts with a host of manufacturing and material choices. Should the part or component be steel or alloy? What finish specs are required? Is machining, forging, or casting most cost-effective? And for what quantities? OEMs attempt to answer these questions early in the product development cycle. But, often the designs that reach the RFQ stage are still incomplete because the models are not fully cost-optimized for the casting process.
The DFM tool can help fill in the blanks for the design in question. Here’s how it works: When an RFQ arrives, basic part properties from the digital model are easily imported into the software. Using a guided series of questions, DFM then leads you through a calculation of every aspect of part cost, referencing information in the software’s machine library, materials database, and machine/operator rate tables. Product life volumes can be adjusted to illustrate cost-per-part as production volumes shift. Product dimensions and tolerances can be altered, too, so that noteworthy cost implications related to problems or design changes become clear and can be discussed.
When the situation warrants, DFM also can be used to help determine whether the chosen casting process and material are the most cost effective for the given geometry and spec—a useful capability for those casters who are full-service providers and offer, or outsource, other fabrication methods in addition to casting. Using the same extensive libraries of industry data, the software allows you to investigate various fabrication process and material choices, making quick comparisons at different production levels (see p.11, “DFM Concurrent Costing: An Example”.)
In the best of worlds, the DFM process would be applied to concept-stage geometries, upfront in the design cycle where changes are easy to make (rather than once CAD models are finalized.) At this early stage, by entering rough part dimensions into the software’s geometry calculator, the tool can help widen design possibilities and assist engineers sorting through the difficult design trade-offs. It’s not likely this option would be possible for casting suppliers, of course, unless buyers are receptive to feedback. Or, OEM-supplier relationships have been tested and deepened by cost transparency and knowledge exchanges, an area where suppliers excel.
To improve the cost of new and redesigned products, the DFM module can be coupled with Design for Assembly (DFA) Product Simplification software. The focus of this program is to reduce part count (a perfect complement to casting), decrease assembly times, improve performance and quality, and lessen warranty and service issues. Together, the two-part methodology (called DFMA™) results in total cost and product optimization, complementing lean and value engineering initiatives.