From the earliest days of the concept, Vestshell has been producing prototype castings from three-dimensional computer-generated patterns. To meet the needs of customers, Vestshell developed a proprietary procedure to overcome the inherent difficulties of the first polymer patterns. Today, thanks to ten years of experience and the evolution of pattern materials, Vestshell offers a wide variety of options in materials, configuration detail, surface quality, risk levels and qualification inspection levels. As rapid prototyping gained popularity, many companies have rushed to include it in their list of capabilities. In reality, however, while the process appears easy to understand, this technology is fraught with intricacies known only to the most experienced investment casters. With more than a decade of prototype casting experience as our guide, Vestshell ensures the success of a prototype casting project by addressing these critical questions:
HOW MANY PATTERNS ARE REQUIRED?
As with conventional wax patterns, the gating and process techniques that will yield a sound end product have to be qualified in order to answer this question. If the customer’s objective is speed, pattern quantities should reflect the need to make several reiterations simultaneously. We would then place a probability quotient on success in achieving a sound casting on the first pass. To achieve their timing objective, the customer can choose to run process qualification in parallel, with multiple gating configurations. This minimizes total cycle time but also increases the risk of losing all patterns without a viable end product. If the customer’s objective is minimizing risk, we would recommend running the qualification in series, modifying the gating based on results. This minimizes the risk but lengthens the cycle time.
HOW DOES VESTSHELL MINIMIZE THE RISK OF NOT HAVING A VIABLE END PRODUCT?
In either scenario, it is of paramount importance that the foundry be familiar with the variables inherent in the rapid prototype to casting process. At Vestshell, special gating techniques, cleaning and inspection procedures, and pouring techniques greatly increase the probability of success on the first pass qualification run. Additionally, depending on the pattern material, a completely separate handling requirement may be implemented to ensure dimensional stability.
ARE THE PROTOTYPE PATTERNS MADE AT THE FOUNDRY OR BY AN OUTSIDE VENDOR?
As this production method gained popularity, many independent service bureaus began to offer rapid prototyping. Unfortunately for unsuspecting customers, many of these firms do not fully understand the variables that can be encountered from one foundry to another or even the foundry process itself. As a result, the quality of rapid prototype patterns can cover a wide spectrum and can be an unpleasant surprise for unsuspecting customers. When partnering with service bureaus, Vestshell takes great care to ensure the patterns meet both the customer’s and our own high quality standards.
SHOULD THE CUSTOMER OR FOUNDRY SELECT THE PROTOTYPE PRODUCER?
Vestshell is easily able to take your three-dimensional design files and work with a service bureau to deliver finished castings within the required dimensional envelope. Our proven track record is your guarantee that your product will be delivered on time and as contracted for. However, customers with positive service bureau relationships of their own are welcome to select their own prototype producer.
WHAT KIND OF TRACK RECORD HAS THE FOUNDRY ESTABLISHED WITH THE OUTSIDE VENDOR?
A proven relationship will minimize surprises, constrain costs and ensure that the cycle time is kept to a minimum. Due to our extensive rapid prototype work, we have a number of dependable outside sources which we can either work with directly, or, should you prefer, recommend to you for development of your pattern. To ensure the best possible results at the best price, Vestshell has established trusting relationships with vendors which specialize in particular capabilities, such as patterns made via polypropylene, from plastic or from wax.
HOW DOES ONE SELECT THE APPROPRIATE PATTERN MATERIAL?
There are a wide variety of materials available on the market today, offering a vast array of benefits – as well as significant drawbacks. Before committing to a prototype material, Vestshell encourages three-way discussions between customer, service bureau and foundry. As we are experienced in producing prototypes from of a wide variety of pattern materials, we are happy to share the results of our first-hand experience with you.
IS RAPID PROTOTYPNIG THE MOST COST-EFFECTIVE METHOD FOR YOUR APPLICATION?
The rapid prototype protocol is a cost-effective option in scenarios when engineers require hardware to test a design or when limited test models must be built without a final design. Rapid prototyping can also be ideal for small quantities of complex parts. Here, one takes full advantage of investment casting’s capabilities, without the cost of hard tooling. In other situations, the cost of rapid prototyping can be often be reduced by using conventional methods that are fast-tracked. Part complexity, design stability and design features all play a role in this determination. Frank discussions with our customers often identify these alternatives and ensure similar results with a lower total cost. As is apparent from our discussion points, casting production from rapid prototype patterns is fraught with risk. Vestshell’s experience in this arena is of great value to many of our customers . . . as it eliminates many of the unknowns and delivers exactly the benefits customers seek: cost-effective, low quantity or complex castings in minimal time.
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