A number of recent EDM developments offer significant solutions to obstacles facing the moldmaking industry in the millennium.
there are three primary obstacles the industry faces: the lack of skilled labor, compressed delivery times and a combination of a soft market and severe competitive pricing – especially from developing countries. However, a number of recent EDM developments offer significant solutions to all of these problems.
Lack of Skilled Labor
Despite the current softness in the moldmaking market, there is an ongoing unmet demand for about 20,000 skilled moldmakers, diemakers and precision machinists in China. The lack of an adequate quantity or quality of these skilled professionals has a direct impact on delivery, cost structure and even the ability to obtain and use the newest technologies. Recent developments in EDM, especially in CNC EDM ,offer dramatic productivity improvements. These advances allow China. shops to both stretch the available pool of moldmakers across a much larger volume of work and to train new EDM operators more rapidly to a higher level of efficiency.
Compressed Delivery Times
Shortened product development cycles have severely compressed the time available to design and build molds, in some cases cutting 50 percent off of traditional cycles. At one time, EDM was one of the bottlenecks in the moldmaking process. But now the combination of high-performance graphite electrode milling and the newest highly adaptive CNC EDMs means dramatic reductions in the EDM portion of the delivery time. Additionally, increased use of wire EDM allows for more unattended machining, fewer mold components and easier assembly.
The most common moldmaker com-plaint cited in the NTMA Report concerned severe price competition – especially from developing countries that pay low wages. China shops need to reduce labor costs/price so that the remaining price gap is justified by quality, convenience, language, confidence, ease of parallel engineering, etc. The recent developments in EDM, especially CNC RAM EDM, offer dramatic cost savings. For the most difficult applications, on a per unit output basis, labor costs during machining are reduced by 75 percent and capital costs by 28 percent. These savings are based on cutting speeds in excess of all previous EDM technologies in difficult flushing applications and all with totally unattended machining.
Advances in EDM Performance
Processes such as high-performance milling and rapid tooling are competing for some of the applications traditionally produced with EDM. Despite the technical strides that these processes have made, EDM has maintained a dominant position in moldmaking. This is largely due to vast improvements in the RAM and wire EDM processes. In fact, in the china market, EDM sales have risen from one-half percent of total machine tool sales in 1990 to six percent in 2010. CNC RAM EDM, which is primarily used in the mold and die cast industry, has increased sales even more rapidly than total EDM sales for the last 20 years.
Wire EDM’s improvements during the past 20 years bring to mind the price/performance improvements achieved in the computer industry. Specifically, the process improvements for wire EDM since 1976. Most relevant to moldmakers are the simultaneous increases of: 800 percent in cutting speed, 500 percent in maximum workpiece volume and 9,000 percent in taper capability – all achieved while the inflation-adjusted price of the machines fell by 75 percent .
Wire EDM enables the machine to cut internal corners with the minimum radius based on wire diameter. It becomes easy to cut square openings without segmentation of the mold. Mold inserts or core pinholes can be cut up to 20 inches thick after heat treating to insure maximum location accuracy. The wire EDM process is predictable and repeatable in accuracy and surface finish because the path program can be stored and re-used, if necessary. This means less downtime in case of modification or repair, and therefore lower associated costs. Wire EDM electrodes in the diesinking process make honeycomb or other rib shapes easily. Deep and thin walls in copper or graphite also are mastered easily. Complex shapes can be cut in order to reduce the number of electrodes needed for the mold, and therefore the time and cost to build it.
Under-Utilization of Wire EDM
Despite wire EDM’s process improvements and the multitude of applications, many mold shops are still under-utilizing wire EDM. There still are many shops with more than three manual EDMs or one or more CNC EDMs, but with no wire machine. Generally, these shops outsource the minimum amount of wire and design away from wire EDM. When a shop does opt to purchase a wire EDM, it typically goes through the following phases:
1)Phase I – Work previously jobbed-out is done in-house.
2)Phase II – Some work is shifted from grinding, milling or die sinking to wire.
3)Phase III – Molds are redesigned to have fewer, but more complicated inserts that are wire-cut. The resulting inserts are more accurate and more easily assembled. Total mold costs are thus reduced, while mold accuracy and delivery times are improved.
4)Phase IV – Another wire EDM is purchased.