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Lab Testing Proves Blast Processes Effectiveness

April 8, 2010
Questions about finish can be hard to answer by trial-and-error methods, wasting time and money. One blast machinery manufacturer offers free laboratory testing to help customers complete necessary evaluations.
Guyson’s Saratoga Springs, NY, lab offers free blast testing services, including estimates of any out-of-ordinary costs. The tests are conducted confidentially with the understanding that successful results have the potential to open new blasting applications and untapped markets. Visit: freeblastlabttesting.php

Metalcasters aren’t accustomed to using lab testing services in connection with their standard shotblasting requirements. Those processes are well established, and there are rarely questions about the right blasting media or equipment. Often, what leads them to the blast testing lab is when a foundry customer wants something different, such as parts with a distinctive appearance, castings in a new material, or surfaces that are specially prepared for a new type of coating. When a finishing requirement is out of the ordinary, a testing service can help you zero-in on the most promising alternatives.

Guyson Corp. is a blast machinery manufacturer that has addressed the issue by offering free laboratory testing services for 35 years. The company performs hands-on trials to help customers evaluate alternative finishing processes, with no cost other than shipping and no obligation to buy.

Besides its investment in a dedicated lab technician and 14 wellused blast cabinets in the 3,000 ft2 test facility, Guyson stocks close to 100 different shot and grit blast media to support lab operations. The lab equipment includes several automated cabinet-blast machines and a robotic blasting system.

“One thing that customers value most about Guyson’s lab testing program is that it’s a way to tap into some fairly specialized expertise. Our recommendations about blast media are considered more objective than those based on testing by a media manufacturer or a local distributor who is in the business of selling media,” explains Steve Donohue, Guyson’s vice president of sales.

New potential blasting requirements arise in connection with a value-added operation. For instance, casters that offer machining services may encounter a need for deburring of parts, or a good customer may ask the foundry to perform an additional blast finishing step to consolidate work done by separate vendors.

Frequently, the process of evaluating new business opportunities involves specifying new blast equipment that may have to be purchased, or its production capacity assessed — including cycle time for the added process, and estimating labor and operating expenses associated with the proposed operation.

Two major issues addressed by lab testing are media selection and media delivery. The Guyson engineering laboratory keeps all types of blasting materials on hand, including plastic shot and grit, ceramic media, metallic beads in stainless steel and specialty alloys, glass, mineral grit and agricultural media — each in a range of screen sizes. It is also necessary to evaluate options for media delivery, whether suction-blast, pressure-blast, or wheel-blast. This question has major implications for development of a specification of the blasting equipment and identification of costs associated with the process.

“A good deal of the foundry shotblast equipment is for batch processing parts in bulk, such as big tumbleblast machines,” explains Donohue. “For many secondary blasting operations that are part of value-added services, the components have to be blasted one at a time, and our customer may be uncertain about the many sizes and types of automated blast machines that are available in that category. Through lab testing, we can demonstrate the finishes from different blasting methods and help the customer get familiar with them.”

When alternative finishes or cosmetic appearances are being considered, there is no substitute for side-by-side comparison of identical components that have been processed differently. The ability of the test lab to demonstrate a variety of surface conditions produced by alternate blast processes, whether subtle or dramatic, is especially helpful when the customer is striving for an unusual new look, or when the appearance of the parts is of vital importance for marketing purposes.

The laboratory testing is done methodically, with attention to all details of the blast process. Information is captured and recorded that will be needed by application engineers to specify and design a blasting machine to produce the demonstrated finishing results. Besides the type and size of the media used in each test, the lab technician documents specifics such as the blast gun, air jet and nozzle, the blast pressure, the angle of the nozzle to the work surface, the distance or offset of the nozzle, motion of the blast gun and the blasting time.

With complete data from the lab, engineers can confidently make decisions about what specific type of automated blast machine will be recommended for the process. They can also identify any special features of the blasting equipment that may be required for a particular finishing operation.

There are times when the blast media is not in question, for instance, when the customer has already specified and approved the blasting material to be used. In these instances, the lab work may consist of a straightforward mechanical evaluation to discover any difficulties to be overcome and to determine how the desired finish can be produced most efficiently.

“If the customer had to buy a 50-lb bag of each different material to do his own testing, and it costs from one to more than five dollars a pound, you could run up a quite a total with just a few tests. Keeping the lab stocked-up with all the different types of media is an expense for Guyson, but we think it is an important investment that supports an integral part of the application engineering work we do here,” adds Donohue.

The testing lab is a good place to build confidence about the blasting process, both for the customer and for the blast machine builder. Both parties have lot at risk when a new step is to be introduced in a manufacturing operation, and there may be serious consequences if shortcuts are taken or assumptions are made without proof. Lab testing provides physical evidence of the results that can be expected, in the form of actual finished components, and it yields reliable quantitative information to back-up engineering decisions.