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by Phil Bryant
February/March 2009
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| Ed Pollitt, John Klocek and Ed Masino of Lehigh Valley Plastics inspect UHMW-PE parts to a customer’s requirements. |
Lehigh Valley Plastics, a fabricator and distributor of specialized plastics based in Bethlehem, PA, USA, made a decision to improve the capability and productivity of its critical CNC machining operations. Management had long sought a comprehensive solution to reduce high-volume machining time for existing parts, increase throughput and expand their overall CNC capacity in order to undertake new, more complex projects.
Up to this point, the majority of machining was being accomplished on dedicated CNC milling equipment through a multiple-step process. LVP knew that the productivity and expansion potential for many of its most repeated and requested parts was already being severely restricted by the speed of these machines. Compounding the situation, this multi-step production process relied heavily on a highly intensive material handling (material staging and movement) support system susceptible to frequent and incapacitating bottlenecks.
The solution was clear: the company needed to divert a significant amount of the time currently allotted to the CNC mills so that new jobs, as well as those better suited to the mills could be added, and the existing, most often-repeated jobs would be more efficiently processed by a new CNC router. To gauge the value potential of this expense as well as justify reorganizing its vital milling operations, a new efficiency benchmark had to be established through a time comparison of the current process to the same part created on a CNC router.
To establish the baseline, workers at LVP first followed the traditional method of creating “blanks” from a full sheet of material on a saw. As usual, the mass of cut blanks were moved across the large facility to the CNC mills and manually secured in part-specific vices before being milled. Depending on the part’s size, from one to a maximum of 12 parts could be loaded at one time, requiring several cycles and significant changeover time to complete the run.
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| A SCM panel saw cuts parts that were drilled on the SCM router. |
After careful consideration, LVP decided to partner with a large international CNC router manufacturer to see what kind of improvement the new machines could make. The vendor quickly was given two challenges. First, they would have to demonstrate significant cost savings through a reduction in overall fabrication time. Second, their machines would have to meet LVP’s stringent quality standards on a vast range of parts, including many that are small and difficult to hold without a specialized fixture.
Precise solutions to the challenges
The first step to proving the new technology’s viability involved creating simulated time projections and sample parts in order to determine the most efficient machining sequences. Using technical drawings provided by LVP, the vendor’s engineering team used CAD/CAM modeling software to create animated time studies mimicking the actual machining of the part on their CNC machines. By also considering finish requirements and material properties, the engineers were able to pinpoint the best tool speeds and machining paths to produce a quality part in the fastest possible time.
The simulated results were then taken to the 5' by 10' CNC router, which was equipped by the vendor with a single 15hp electro-spindle, automatic tool changer and vacuum table system. Beyond representing the best throughput capabilities for LVP’s parts, this configuration also benefited production by allowing the operator to choose between machining an entire sheet at once or, when working with multiple materials, to utilize a pendulum sequence to unload and reload one side of the table while the other side is being machined.
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| The LVP team inspect parts that were routed into single unit kits. This process allows Lehigh Valley Plastics flexibility to meet its customer’s parts requirement and is one of its many lean initiatives. |
Making use of a process known as “nesting,” whereby the CAD/CAM software arranges parts from several jobs to achieve optimal yield from each piece of raw material, the test was set to commence. With a 4' x 10' sheet of material securely vacuumed into place, all of the required machining operations were then completed in one continuous phase, quickly producing an entire sheet of parts with no operator intervention. As designed, the part program called for the CNC router to execute the following steps:
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Rout the inside diameter of an open
ing for each part.
- Rout the outside diameter of a countersink for the previously made
openings.
- Rout any remaining holes, grooves,
bevels or other requirements.
- Rout the final outside dimensions.
After years of milling individually cut blanks, the CNC router had managed to produce an entire sheet of parts with remarkably little waste. After a few quick calculations it was determined that the new machine had reduced overall processing time by well over 30 percent while maintaining quality levels well within the customer’s tight standards. Based on the initial productivity improvements using this process, LVP subsequently decided to further hone the new process by completing the final step (No. 4) on its CNC panel saw to allow even more throughput on the new router.
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| Lehigh Valley Plastics chose SCM Group’s Routech R125 CNC Router to improve value-added offerings to its customers. |
“Because both machines hold very tight tolerances, we were able to use a combination approach to achieve productivity increases of over 60 percent of our previous process,” states LVP Engineer Tam Tran. Since those first trials, the company has moved a number of high-volume projects to its router and continues to partner with customers on new opportunities and finding innovative uses for the technology.
The CNC router also provides the versatility to rout almost all types of thermoplastic, thermoset and composite materials for many applications.
“Lehigh Valley Plastics is a customer-driven company and therefore we must utilize technology that allows us to deliver precise solutions in a timely manner,” said LVP President David Keim. “We consider a number of vital factors when choosing a new piece of equipment from a vendor, including technology, reliability, support capability and training. In the end, we chose a vendor who has a similar approach to their customers as we do.”
Phil Bryant is the plastics division manager for SCM Group USA. For further information, contact SCM Group USA, 2475 Satellite Boulevard, Duluth, GA 30096 USA; (800) 292-1850, fax (770) 813-8819, www.scmplastics.com. For information on Lehigh Valley Plastics, visit www.lehighvalleyplastics.com.
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