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design & molding

Reducing Time to Market

By James R. Knirsch, President and CEO, RSP Tooling

One of the most pressing requirements for any manufacturer of plastic parts is the need to reduce tooling delivery time. Part production has made many improvements over the years but one thing has stayed substantially the same — the amount of time it takes from concept to going into production. The major cause for this continuing bottleneck is the tooling lead-time. There is a new indirect spray form process now being commercialized to manufacture production quality tooling that will overcome this problem. It is Rapid Solidification Process (RSP^TM) Tooling. This process allows the manufacturer to build production tooling in the time it usually takes to make a prototype tool. And what is sacrificed to get this improved delivery? Nothing. In fact, there is strong evidence to believe this new tooling will increase tool life compared to conventional tooling made from the same alloy.

History

The Rapid Solidification Process (RSP) was developed at the Idaho National Engineering and Environmental Laboratory (INEEL) under grants from the U.S. Department of Energy. The initial patent for the process was written in 1990 and had as its basis the invention or discovery that a liquid could be broken down into small droplets by use of the shearing effect of a flowing gas.

Work on the process resulted in another patent in 1995 which introduced the use of pressurized injection of liquid into a Ventura tube, thereby improving the operational flexibility of the device while producing a more uniform droplet size distribution in the spray. An additional benefit was the ability to control and increase the cooling rate of the droplets, which results in microstructure and material property improvements in the deposited metal. This resulted in two things: a new patent in 1997, and the terminology of RSP Tooling. Additional patent applications have been submitted which refine the actual process to produce tooling.

RSP Tooling, LLC was formed in January 2002 to design, build, use and sell machines that manufacture tooling using this process. The company signed a license agreement with Bechtel BWXT Idaho, LLC (the company managing INEEL) for the exclusive worldwide use of the RSP patents for all tooling applications. The first production machine was designed and built by Belcan Corporation's Specialty Equipment Engineering Division (SEED) of Solon, Ohio. This machine (see Figure 1) is able to produce a 50-pound steel insert (7 inches x 7inches x 4 inches) every three hours. It is designed as a single batch unit so that a different metal can be used for each insert. The spray process is able to spray steel at a rate of about 500 pounds per hour. The machine is located at The Technology House also located in Solon, Ohio and is now producing tools for various industries including forging, die casting, stamping and plastics injection molding.

Figure 1. RSP Tooling beta machine.

The Process

The RSP Tooling technology makes high-quality production tooling from virtually any tooling metal, for any tooling process. The technique eliminates the need for CNC milling, sink EDM, benching, polishing, engraving and conventional heat treatment. The general concept involves converting a mold design described by a CAD file to a tooling master using a suitable additive rapid prototyping technology such as stereolithography, a subtractive method out of a soft material, or even hand-worked clay. A pattern transfer is made to a castable ceramic. This is followed by spray forming a thick deposit of tool steel (or other alloy) on the pattern to capture the desired shape, surface texture, detail and thickness. The resultant metal block is cooled to room temperature and separated from the pattern. Typically, the deposit's exterior walls are machined by wire EDM and any bolt holes and water lines are added as seen in Figure 2.

Figure 2. RSP process.

The high cooling rate of the deposit greatly impedes atomic diffusion, so segregation is very limited compared to cast metal. It also minimizes the erosive interaction of the metal and ceramic tool pattern, allowing the deposited metal to accurately capture surface details of the ceramic that would not be possible if the metal was cast onto the ceramic. The rapid solidification rate also results in non-equilibrium solidification, extended solid solubility and very limited segregation, as can be seen in Figure 3.

Figure 3. RSP H13 at 500x.

Benefits

The benefits of the RSP Tooling process can be summarized as: Reduces tool lead time

The entire operation from receipt of a CAD model to the delivery of a finished tool insert could theoretically be done in 64 hours. Normal delivery time should be approximately seven days. This time savings is compounded when multiple cavities are required, since each cavity would add only two hours (an eight-cavity die with mating halves could be completed in eight days). Another interesting advantage is that complexity is not relevant. The two-hour cycle time is the same for a flat plate or a detailed engraving as seen in Figure 4.

Figure 4. Details as small as 0.003 inch are captured.

There is also a reduction in costs. Since many standard operations are eliminated, costs are less. There is also the financial benefit of reduced tooling lead times and reduced tooling inventories. Significant reduction of energy usage results from the elimination of heat treating and machining. There is very little material waste, since excess material and even old and worn tools can be used as the initial melt material. It is also imperative to design the process, gates, vents and runners prior to making the cavity, since it can all be added to the mold for the same cost.

Improvements

Research continues at RSP Tooling with the goal of improving accuracy and cutting delivery time. Accuracy of the process is approximately +/- 0.002 inch. Dr. James Folkestatd of Colorado State University (CSU) is developing data on the shrink of the ceramic which is expected to improve accuracy by 50 percent. CSU and INEEL are also working on new, faster, more accurate ceramics which will reduce timing and cost and improve accuracy.

Dr. John Frater of Cleveland State University is working on new subtractive methods of making the initial pattern. Initial data indicates that both the time and cost of this pattern could be reduced by 50 percent. This work is being partially funded by the Forging Industry Association.

RSP Tooling is also working on clad tooling with the help of INEEL. This tooling is made by spraying a thin layer of steel and then following up with a copper addition to complete the tool. This has the benefit of both reducing the cost and time to finish an RSP tool and decreasing the cycle time by up to 40 per cent.

For more information about RSP Tooling, LLC, visit www.RSPtooling.com or contact James Knirsch (tel: +1 440 505 6033, email: knirsch@rsptooling.com).