- October 26, 2020
- Case Study
Railway machine tool builder needed robust 5-axis machine to ensure uptime, accuracy, and precision in cutter tool manufacturing.
Simmons Machine Tool Corporation, a machine tool builder for the railway industry, was faced with the need to purchase a new 5-axis mill-turn machining center for their machine tool manufacturing processes. Due to concerns about chip fall, robustness, accuracy, and consistency, many 5-axis machines designed for tool and die mold applications failed to meet Simmons’ needs. The company ultimately decided to purchase the GROB G550T 5-axis universal mill-turn machining center, which is built for more highly-demanding manufacturing settings. The G550T has enabled Simmons to not only meet but exceed their ROI goals in the first three years of operation.
Simmons Machine Tool Corporation is a machine tool and automation builder, producing specialized machine tools for railway wheel set maintenance and production around the world.
Machining for machine tools
Simmons Machine Tool Corporation, part of the NSH Group, is a machine tool and automation builder that produces specialized machine tools for railway wheel set maintenance and production worldwide. The company manufactures machine tools for high-speed, metro, passenger transit, and freight railway applications. Given the heavy-duty nature of these applications, and an industry trend of forgoing preventative maintenance in favor of selecting machines that can take the heavy wear-and-tear, Simmons Machine Tool Corporation’s products must be extremely robust. In order to ensure maximum reliability and robustness for their customers, Simmons Machine Tool Corporation must itself rely on robust processes and machines to manufacture their own products.
Simmons Machine Tool Corporation’s place as a machine tool builder in a highly demanding industry meant that, when it came time for them to select a 5-axis machine for their own shop, the company and its leadership had a unique perspective on the purchasing process. Simmons needed a 5-axis machine to turn and mill precise products like their profile milling cutters for underfloor wheel re-profiling machines. Over the past 12 years of using various 5-axis machine technology, though, leaders in the company realized that standard tool and die mold machines couldn’t “cut it,” so to speak, with the hardened cutter bodies and other extremely robust tools and components they were manufacturing.
What’s more, as machine tool builders themselves, the experts at Simmons were able to look at prospective machines and consider specific challenges in terms of fit and finish, chip evacuation and containment, and more. Finally, having seen warranty claims and service calls come in from their own customers, the experts at Simmons knew to look at indirect performance factors and aspects of user experience factors that would determine the machine’s value and ease of use across its lifespan.
With these criteria in mind, Simmons Machine Tool Corporation began searching for a new 5-axis machine in 2016. The machine would be used to produce profile milling cutters for in-situ wheel re-profiling of locomotives, transit vehicles, and high speed trains. The company turns and mills these cutters from a 12” diameter solid stock 4150 steel, hardened to about 300 BHN. The cutters are then used on Simmons’ Stanray machines, supplied to freight railway, metro, and transit passenger railway customers around the world.
Challenges of selecting a 5-axis machine for a uniquely demanding application
Weighing 22.5 tons, the Stanray machine is mounted in a pit under the rail so that a locomotive can be positioned on top of the machine. The profile milling cutters then re-profile the wheels, which are often in poor condition with flat spots on the tread caused by wheel slippage or emergency braking. The flat spots – work hardened areas about the size of a quarter–are far higher in measured hardness compared to the rest of the wheel surface. The cutters themselves, then, must be extremely robust, just as the machines that produce them must be. In addition to robustness, the experts at Simmons had a number of other criteria with which they evaluated possible 5-axis machines.
“We reviewed several different 5-axis machines, and most couldn’t keep up with the demands of our application,” said David William Davis, President & COO at Simmons Machine Tool Corporation. “We make a lot chips when we make a cutter, so chip containment and evacuation from the machine tool is important, and many just didn’t measure up.”
The company found that 5-axis machining centers with vertical spindle orientations tended to have more surfaces and areas for chips to collect on, which prevented easy chip evacuation. Additionally, many 5-axis machines were focused on die and mold production rather than heavy duty metal cutting, and so couldn’t hold up to this demanding railway machine application.
“Overall machine robustness and dependability was also an issue, primarily involving spindle bearing contamination and related failures,” Davis added. “Last, we found that with many 5 axis machine builders, locally available service plus quality remote or virtual service was often simply not available.”
As machine experts themselves, the team at Simmons was interested in flexible service and repair options, since they knew they would be able to fix some issues themselves with remote support.
Finding a good fit with GROB
After rejecting several different 5-axis machines that did not meet their needs, the team at Simmons met with a representative from GROB, who presented the company’s horizontal spindle 5-axis universal mill-turn machines. Satisfied that one of these machines would be robust enough to meet their needs, and that GROB’s service offerings would be suitable in their unique position, the leadership at Simmons purchased the GROB G550T 5-axis universal mill-turn machining center in Spring 2017, and traveled to GROB’s factory in Mindelheim, Germany, for demonstrations in Fall 2017. Ultimately, the machine was put into full production late 2017 and GROB Systems in Bluffton, OH, facilited training at Simmons’ facility.
“We knew that we wanted a production machine that was built Stanray tough. We were aware of GROB from automotive, high volume machining installations, as our sister companies in Germany build machine tools for manufacturing automotive crankshafts and other engine components,” Davis said. “GROB’s reputation as a reliable manufacturer of extremely dependable and robust machines in a demanding production environment was well-known to us.”
Simmons chose GROB’s 5-axis machining technology because it was production ready, has a horizontal spindle configuration allowing for optimal chip flow, features intuitive programming, and delivers reliable consistency and accuracy. The GROB 5-axis machining technology has been an excellent fit for Simmons’ demanding and precise manufacturing practices.
“We achieve better dimensional consistency with the G550T compared to other 5-axis machines. As an example, one key dimension on the Stanray profile milling cutter has to be turned to +0.0000, -0.0005”. After a short time using the G550T, we simply eliminated probing this feature because our confidence in hitting this dimension repeatedly is so high,” Davis said.
Part of the precision and accuracy benefits of the GROB machining center comes from its programming environment, which Davis said machinists have found to be very intuitive for 5-axis machining. The programming environment, specifically the Siemens NX CAM software paired with Siemens controls, enables machinists to simulate parts of a virtual machine. As a result, Simmons machinists report high levels of confidence in products machined by the G550T, even with first-of-its-kind parts.
One of the key factors for deciding to purchase the GROB 5-axis machine was its horizontal spindle axis.
“Before we decided to purchase the GROB product, we talked with other machine shops and manufacturers about whether vertical or horizontal spindle orientation is better. Sometimes people are intimidated by a horizontal orientation, since it’s not as common in tool-and-die mold machining technology, but our machinists found there was little to no barrier to entry thanks to the digital tools that are part of GROB’s machine package,” Davis said.
“The horizontal spindle configuration, plus the overall design of the machining area, permits optimal chip flow and evacuation and unattended running, all of which are extremely important in our manufacturing processes.”
In addition, Simmons has found the GROB spindle to be extremely robust.The spindles are built in-house by GROB and can be easily repaired or replaced, which can be critical to maintaining uptime.
Saving time, saving money
Implementing GROB’s 5-axis machining technology has translated into cost savings and efficiency benefits over the last nearly three years for Simmons Machine Tool Corporation. Downtime was dramatically reduced over previous 5-axis machining, since the GROB G550T is better built to withstand the demands of Simmons’ manufacturing processes and materials. Given that they are used to machine consumable parts, the G550T’s design factors for uptime are extremely important to manufacturing efficiency and cost optimization. In addition, the GROB machine can be operated unattended, saving on man-hours for manufacturing and enabling machinist labor to be put to use elsewhere in the process, as a result, Davis reports, Simmons has not only realized their ROI goals but far exceeded them in these first three years.
Another important ingredient for meeting and exceeding ROI goals has been the G550T’s accuracy and consistency; the machine is so accurate that individual components do not need to be measured for accuracy, thus reducing measuring time as well as non-value-added time in the production stream. What’s more, reduced vibration at the tool tip translates into extended tool life, accuracy, and consistency.
Finally, Davis reports, GROB’s service team has consistently responded rapidly and, in most cases, has been able to service the machine remotely. When a field service technician has been needed, highly trained service providers with extensive, hands-on experience with the machines has been dispatched quickly in order to ensure consistent uptime. Although, as a machine tool builder, Simmons has historically been more self-sufficient than most in terms of troubleshooting their machining technology, GROB’s expertise and responsiveness have led the Simmons team to feel comfortable handing over the reins for service and maintenance.
Uniquely positioned as a machine tool building seeking equipment from another machine tool builder to enable accurate and efficient tool manufacturing, Simmons Machine Tool Corporation had stringent standards when they researched 5-axis machines for their manufacturing floor. Given the highly demanding nature of their railway applications, they were seeking a 5-axis machine that could keep up with difficult materials and processes. After extensive research, the company purchased the GROB G550T 5-axis universal mill-turn machining center and, in the three years since, has seen extensive success in integrating the product into their manufacturing processes. With particular benefits in terms of chip fall and evacuation, service, intuitive programming, and exceptional reliability and consistency, the GROB machine has met Simmons’ demanding machining needs. The entire project was facilitated through GROB Systems’ Bluffton, OH, facility, which helped ensure Simmons had a quick and successful startup.
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