March 2012 / Volume 64 / Issue 3|
Working in a coal mine
By CTE Staff
Cincinnati Mine Machinery Co. produces OEM and replacement components for several of the world’s largest mining equipment manufacturers, with an emphasis on conveyor systems.
When facing increasing sales activity and limited production capacity, the Cincinnati-based company began researching new machining technologies that would enable it to improve throughput and maintain higher part-quality consistency. The company’s solution was a Makino Machining Complex (MMC2) with 24 pallets and two a71 horizontal machining centers.
Courtesy of All images: Cincinnati Mine Machinery
“Our five previous milling machines from 1995 weren’t cutting it anymore with regard to reliability, consistency and productivity,” said Tim Jent, production supervisor at Cincinnati Mine. “The installation of the Makino machining cell enabled us to replace five machines with two, while doubling production capacity, redeploying labor and improving overall quality and flexibility.”
While advances in technology have made coal mines safer for miners, the environment still causes harsh wear and tear on mining equipment. Chain assemblies, such as those made by Cincinnati Mine, face daily abuse from mechanical interferences and from conveying large volumes of coal and rock.
“Consistent quality is essential to our chain assemblies,” Jent said. “The materials we work with are typically heat-treated, high-alloy steel forgings, ranging from 40 to 50 HRC.”
The investment in automated capabilities was a new direction for Cincinnati Mine and the largest capital investment in its history.
“Automation at this level was a giant leap for our company, but one that needed to happen,” Jent said. “Makino—understanding our limited exposure to automation—offered us a tremendous level of support during implementation. Within 3 weeks, their engineering services were producing initial runs of the key steel forging at their facility. Together, we fine-tuned the machining cell and its accessories for optimal performance.”
After about 3 months, Makino Inc., Mason, Ohio, installed the automated equipment.
“The completed solution addresses all of our needs, from top to bottom,” said Randy Morris, Cincinnati Mine’s manager of engineering. “Prior to this, hard milling processes were punishing our hydraulic fixtures, causing frequent fluid leakage and reduced rigidity. The new custom mechanical fixture designs remove these issues.”
Cincinnati Mine’s initial production runs involved a single chain assembly—an important component because such assemblies make up 65 percent of its conveyor business. Since then, the company has added several part families to the machining cell.
“Prior to the integration of the MMC2, our production philosophy focused on large batches,” Jent said. “The variety of parts produced on the cell eventually became so great that we decided to take advantage of our increased flexibility and move to a kanban system, where we can schedule part orders on the fly.”
The cell’s MAS-A5 control system enables the company to instantaneously coordinate production schedules for increased flexibility. When high-priority orders come through, the operator is able to suspend current processes and call up the new job in 30 seconds. Once completed, the suspended job can resume without any concerns related to positioning inaccuracies.
The improved production planning capabilities give Cincinnati Mine the ability to continuously alternate batches. Whereas operators were once required to load and unload parts in less than 15 minutes on some large orders, they can now juggle batches of longer and shorter run times to afford additional changeover time between jobs.
“Even with more than 25 part varie-ties, we’re still running more efficiently than ever, producing about 20,000 parts each month while running two shifts,” Morris said. “The cell’s scheduling software and unattended reliability have reduced our overall cycle times by 70 percent compared to previous processes and have enabled us to run parts overnight and some weekends when our orders are even higher.”
While previous machines required a high level of operator involvement that resulted in some human error, the a71 cell has removed a large percentage of manual involvement.
“The a71 cell’s tool presetter, part probing and BTSOMA (Broken Tool Sensor Outside of Machining Area) have enabled us to produce parts that look the same as our first run,” Morris said. “We no longer run into issues of operators loading tools, inserting fixtures or programming macros uniquely. Everything is preset one time within the cell’s controller and monitored for accuracy with each new load. If any measurements deviate from the preprogrammed specifications, the control signals the machine to postpone production or change tooling.”
Cincinnati Mine also reports that the programming, monitoring and probing support within the MMC2 and a71 machining centers have contributed to extended tool life and reduced tool breakage. This has decreased the company’s overall tool spending by 30 percent despite new investments in more expensive, high-efficiency tools.
“By changing our tooling approach, we’re now able to share tools between jobs, freeing up space in the toolchanger for more applications and optimizing our tool usage,” Morris said. “We’re also taking advantage of the a71’s faster feed rates, using shorter tools with more aggressive cutting for higher metal-removal rates. In total, parts are now running at least two to three times faster, even with more tools touching each part.”
Cincinnati Mine has no intention of slowing its advancements. The company is working on tackling an automated solution for transporting material to and from the cell for improved efficiency in fixture loading and finished part delivery to other departments.
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