Rapid prototype tooling (RPT) is more than part design — it’s the process, materials, manufacturability, costs and tool designs. From start to finish, rapid prototyping not only overcomes time restraints, but eliminates the questions and variables that can often halt future production at the worst times.
The RPT process is defined as the process utilized to develop a mold, which will produce a plastic, rubber or LIM part using the exact same method that will be utilized during the manufacture of the production tooling and parts. It is the objective of this process to obtain data for the engineering, tooling, and manufacturing groups that will be useful in the production of a customer program, yielding long term valuable results for the complete process. The data can also be shared with the company’s partner, the customer, so they may learn the process as well. An experienced molder having a proven RPT process is in a better position to give the customer a sense of confidence that the part will meet and/or exceed their expectations. Furthermore, a critical factor in the use of RPT is from knowing that prototype parts, tooling, and the molding process will all approximate production-like conditions. The customer is given a strong sense of confidence in what to expect in cost and quality and can prepare accordingly. According to Tom Diaz, director of operations of Inland Technologies, a division of the Hi-Tech Group, “One of the most important practices in the prototype process is found in analyzing the data that comes from our customers in the form of CAD files and other data about their product. The reason this is important is because it is the initial step in our analyzing and planning of the entire program.” Rarely do parts produced with computer model programs, stereo-lithography (SLA), or models made by any other means give the engineer the same data. Many times, parting-lines and gate locations, for example, have an adverse affect on part function. “The reason this is, states Diaz, is that materials used in other processes can not be reliably tested in real world circumstances. This same data produced through the RPT process is shared with the customer to assist them in learning more of the process and its benefits.” Using RPT, Diaz has identified the need for less complex components, smaller parts, more robust packages, or the possible use of thickening of wall sections for improved mold flow. Recommendations like this provide the customer a far superior product when manufactured under production-like conditions. The RPT ProcessDesign Feasibility
The preferred file type from the customer is CAD files in their native format. These files can then be shared with all aspects of the RTP process such as design and CNC programming without losing their parametric relationship that the customer had designed. In the case where any improvements are made to the part data during the RTP process, the changes can then be sent directly to the customer without going through a translation process that might result in misinterpretation. The benefit is that the customer and supplier share a common data base.
Concurrent Tool Build Begins
In this phase, the design may not be finished, however tooling may begin. By beginning the tooling during this phase of the program, the company can give the customer the benefit of decreased lead times. This can normally cut a minimum of two weeks off the delivery because the decision to proceed is made quickly. It is important that tooling does not exceed the point of no return—the point where the design of the part must be locked in, that tooling does not become scrap, resulting in waste and lost time.
Locked-In Final Design
The design needs to be locked in because electrode manufacture and CNC programming needs to begin. Making changes after this phase to the part design would result in an impact to the delivery date and wasted time and money generating CNC programs and electrodes. The customer must commit at some point in order for the tooling to continue and keep on the expedited schedule.
Tooling Completed
The RPT process results in a quick delivery of a mold—ready for limited production—of the first sample prototype parts that will be delivered to the customer. Dimensional studies in the form of first article inspections and capability studies on key dimensions are performed to identify opportunities for improvements as they may relate to a full multi-cavity production tool. Data collected during this stage may include CpK, and Cp studies to show how robust the process of manufacture may be.
Prototyping
The parts are molded, inspected, and reviewed by the customer for design intent and testing. Depending on these process results, the customer may make additional changes to the part, resulting in some of the above processes having to begin again, although these normally move to completion much faster. Typically, mold trials are performed about two or three times in order to evaluate the process and determine the optimal process settings that will yield the most robust molded product in a limited production run. This information is then used in preparing for production mold build timelines.
Conclusion
The RPT process will yield the customer and the manufacturer of the product valuable data that can be used to optimize the design of the product to meet the customer’s expectations of part performance and cost. The goal of the process is to bring product to the manufacturing phase as quickly as possible, and it is dependent on close communication between the customer and the supplier. Rapid prototype tooling provides OEMs an invaluable tooling quality service. As with any technology, this process still requires qualified project engineers, engineering staff, process engineers, and a fully supplied tool room to deliver the results mandated by the complex medical device industry.
Kenneth Dodd is a brand identity consultant at Final Touch Marketing, Temecula, CA. For the past 20 years, he has represented medical device firms promoting strategic brand position and awareness.
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