Ten years ago, it would not have been uncommon for the leadtime to manufacture a mold to be in the 12 to 16 week range—three to four months. However, over the past decade significant technological advancements in both machine tools technologies and manufacturing techniques have drastically reduced production times.

Today, the leadtime to manufacture the same mold would be two to four weeks—often less than one month. Trial parts can be quickly molded using rapid prototype cavities created in a day or two. Now, time-to-market concerns often require production in weeks or even days, something that would have been thought unrealistic only a few years ago.

  In addition to demanding faster cycle times and shorter leadtimes, customers expect tighter tolerances and higher quality surface finishes. Typically, doing a job faster produces a lower-quality product. Unfortunately, in this industry, quality defines who a moldmaker is. If quality suffers, business suffers.

  Machine Tool Technology
 As a result, moldmakers are turning to the machine tool builder for products that deliver higher productivity, greater precision, better surface finishes, and eliminate additional time-consuming hand finishing work. To meet this need, machine tool builders have dramatically increased machine axis velocities and accelerations, greatly expanded spindle rpm, while tightening positioning accuracy, repeatability and geometric tolerances. Control enhancements also have facilitated high-speed machining of complex, three-dimensional mold shapes to tighter tolerances.

  A decade ago, 10,000 rpm was considered a fast spindle and 10 ipm federates were acceptable. Today, machines routinely incorporate 20,000, 30,000 and even 40,000 rpm spindles, and feedrates of 200, 300 and 400 ipm are commonplace. Combining these advanced machine tools with new manufacturing techniques—such as high-speed milling routines and tooling, hard-milling to eliminate multiple steps of machining, and high performance machining utilizing programming tricks and machine capabilities have provide the moldmaker with the necessary tools to compete and win.

  In the past, it was virtually impossible to get a finished mold directly from a machine tool. A moldmaker would first machine the mold in the steel’s soft state, cutting a mold cavity that was fairly rough. After heat treating, the mold would be finished machined to as close to the final tolerances as possible. Ten years ago, the typical tolerance that might be achieved was +/- 0.002 inches. After hours of cleaning up the core and cavity by hand, the mold components would be ready for initial assembly. The two mold halves would be fit together and additional hand working would be required to actually create the proper fit and clearances between the working parts of the mold. Only after this labor intensive and time-consuming process was it actually ready for a test shot.

  Once again, after the initial parts were molded—typically, there would be additional hand-polishing required to meet part finish requirements and some additional fitting work to insure proper match-lines, seams and no flash on the finished part. Not to mention the fact that the mold would often have to be machined twice—once for the initial geometries and a second time after heat-treating to harden the mold.

  Machining in the Hardened State
 Perhaps the biggest step forward to reduce the time of recent years is the ability to cut the mold in the hardened state, often eliminating the two rounds of machining required and the wait-time for heat treating. A decade ago, it was understood that hardened steels were typically to be finish machined, and more often than not, hand finished. Today’s machines1 are capable of machining materials in the 60+ Rockwell range, and have even successfully machined carbide at 80+ HRc.

  Given this ability, machining in the hardened state is not only possible, but preferable, because it frequently eliminates the time consuming EDM process. However, there is still a place for EDM. This is especially true for difficult-to-machine areas, such as deep ribs, tough radii, and very tight-tolerance features.

  Burning on a Ram EDM is very accurate, but it also is very slow, particularly on a complex or large mold. Having the ability to mill in the hardened state without the use of Ram EDM saves overall mold production time and aids in the timely delivery of the mold, thanks to the simplified process and cutting directly to zero on the milling machine. A hardened block goes into one machine and a finished mold comes out.

  By using advanced machine tools, moldmakers can eliminate additional, labor intensive, time-consuming, expensive steps and cut mold components to zero with accuracies to +/- 0.0005 inches or less in materials of 60 HRc and harder. Using machine tools that allow them to reach these tolerances and mill in the hardened state eliminates additional hand finishing and fitting, provides outstanding surface finishes, helps shops shorten leadtimes and reduce costs dramatically, giving them a definite advantage relative to overseas competition.

  Many customers report that the primary reason they’re still successful, even after losing simple work to lower-cost providers, is due to their ability to turn out high quality molds quickly. They credit their teams of innovative engineers, new processing techniques and tooling, along with the ever-advancing machine tool, which allows them to produce molds faster and without the need for re-work, as is all-too common when work is sent overseas.

About First-rate Mold Solution Co., Ltd.
First-rate Mold Solution Co., Ltd. in China, provide industry design,mold design,mold manufacturing,molding analysis,project management service.

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