product development | DFM
Figure 1: Typical savings resulting from a structured DFM approach Potential cost savings
Material savings 5% - 25% Moulding cycle time reduction 5% - 45%
Reduction in mould costs through standardisation 10% - 55% Yield improvement by eliminating part defects 5% - 25%
Leadtime reduction
Component design development 10% - 35% Tool design approval process 5% - 40% Mould manufacturing time 10% - 65%
Mould de-bugging time at the toolmaker 20%-50% Mould validation 10% - 30%
quence, it is highly unusual to fi nd a mechanical designer who is highly skilled in every area of required expertise. In general, suppliers such as mouldmakers and moulders are relied upon to provide this kind of specifi c technical input. However, because the sup- plier’s main focus is always going to be on their own business, their feedback may not be as independent or as comprehensive as is needed. For example, some tool makers may not be very interested in the moulder’s problems during production once the tool has been approved by the customer and has gone out the door. The bottom line is that somebody has to oversee and manage all feedback during the product development process to ensure the right decisions are made. This can either be done internally by one of the members of the product development process chain, or it can be outsourced to an external third party with the required in-house expertise to oversee all areas from DFM (Design for Manufacturing) and tooling manufacture through to processing. Using a structured DFM approach will allow the
component and product design to be developed in a positive way with regard to cost and reliability. In addition, it will enable the customer to meet desired timelines for product launch. Missing a product launch and having the product not sitting on the shelves at the appropriate time can cost an OEM millions of euros. Reputations can also be damaged if a competitive product does not make it into the shops on time. For example, material selection will determine a
whole raft of product and processing criteria, including physical properties, fi lling of the component and component design features along the fl ow path, as well as the costs at any specifi c production volume. Analyzing component geometry is the next important step, ensuring that the part can be fi lled and demoulded
52 INJECTION WORLD | September 2012
according to specifi cation. By using tools such as CAD for demoulding and thickness analysis, fl ow analysis applications, and FEM and combining that with hands-on moulding experience, it is possible to optimise the design to ensure optimal material (resin) usage, fast cycle times and to deliver the expected part quality with high yields in production. It has been shown in previous projects that cycle time savings of up to 65% can be achieved. Also, information gained at this stage can be used to perform a precise prediction of produc- tion cost, giving regard to cycle time, tool concept, number of cavities or tools, and moulding equipment. At the end of the DFM phase, all this data is collected
before the tool is designed so it is possible to estimate the direct impact on cost and quality if some signifi cant design changes take place. Cost-wise, it is worth taking the time during the DFM process to investigate new tooling technologies that can be incorporated into the component design because they could ultimately simplify the tool build and aid in production. For instance, in several cases in the caps and closures industry it has been found that the use of collapsing cores rather than unscrewing mechanisms can allow the wall thickness to be reduced as the caps will not have to withstand torque force during demoulding. Looking at only a 1% material saving on a production volume of 200 million caps per year will result in huge cost savings. Most production problems can be determined and
eliminated just by looking at the product design and specifi cations. Unfortunately, only 25-30% of all projects will follow a structured DFM approach. Troubleshooting moulds that are already in production or are close to being ramped up is always an expensive exercise. Implementing a proper DFM analysis will reduce the risk of failure and keep the project and production costs low and controlled. Figure 1 shows the potential scope for cost and lead time savings through successful adoption of DFM. So how does this translate into practice? Figure 2
shows a real example of a component - part of an overall assembly - where it was necessary to invest in new tooling for all components because the tools had reached the end of their serviceable life. All of the parts had similar issues, including relatively poor visual quality, long moulding cycle times and high component costs. DFM and process development was carried out to correct these issues. Working with the customer, all of the moulded
components and mating parts were re designed to keep the same function and performance while making signifi cant cost and effi ciency improvements. The fi nal result was an annual total cost saving of €147,000. This was achieved by cutting quality defects to less than 0.2%, saving on raw material usage, and reducing
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