Reproduciremos parte de un artículo de Derek Korn acerca de la implementación del sistema MQL en diferentes máquinas de la planta de Ford Van Dyke en USA.
Para poder leer el artículo completo, clicar el enlace al final del mismo.
Clean machining using minimum quantity lubrication has allowed Ford’s Van Dyke transmission plant to become fundamentally more efficient and effective at manufacturing six-speed automatic transmissions.
Ford’s Van Dyke transmission plant implemented minimum quantity lubrication (MQL) for the same primary reasons other big manufacturers have done it. MQL lowers machining costs by eliminating not only the large volume of coolant used in conventional wet operations, but also all the ancillary equipment and electrical power necessary to maintain a big, central coolant system. MQL also creates a cleaner, safer manufacturing environment, which is beneficial to the health of both the equipment used on the shop floor and the employees who work there.
I suspect, though, that the Sterling Heights, Michigan plant initially didn’t realize how changing the way a cutting tool and workpiece are cooled and lubricated during machining would have such an impactful, trickle-down effect on its large-scale manufacturing process beyond the advantages just mentioned. Switching to MQL to machine three types of aluminum components for the company’s 6F line of front-wheel-drive transmissions has ultimately boosted the plant’s flexibility and efficiency, allowing it to more quickly adapt to today’s rapidly changing market demands for different types of vehicles. It also brought machining “out into the open” so it could be located closer to the transmission assembly area, minimizing wasteful part travel throughout the facility.
Luckily for me, I got a chance to see how the tidy Van Dyke plant reaps MQL’s benefits during a visit this summer. While there, I also learned how the plant’s MQL efforts have matured over the past few years as it has become more proficient at near-dry machining.
The Technology of MQL
In short, MQL delivers a very small amount of coolant to a cutter’s edge in the form of an oil mist or aerosol, as opposed to traditional techniques of flooding the workpiece and tool with a substantial volume of liquid coolant. Just a tiny bit of that aerosol is left on the chips, workpiece and machine during the cutting operation. However, it’s nothing like what happens when cutting with flood coolant. (The link under Editors Picks at the right contains additional articles and a helpful video explaining more about the basics of MQL.)
Van Dyke was not the first Ford transmission plant to implement this alternate coolant approach—that was the plant in Livonia, Michigan. In 2002, the Livonia plant began testing MQL machining on intricate valve bodies, which serve as hydraulic control centers for automatic transmissions such as the 6F six-speeds. The tests proved that MQL-machined valve bodies could be produced at or above the requisite tight accuracy and finish requirements, so the plant moved forward and installed a cell consisting of MAG Powertrain Ex-Cell-O XHC 241 linear-motor HMCs. At that time, those four-axis machines offered what the plant felt was the most advanced MQL system available. Installation of those machines, which are designed to deliver aerosol coolant through the spindle and tool, was completed in 2005. A nearly identical cell was subsequently installed at Van Dyke in 2006. Machines at both plants (166 total MQL machines between the two) are fed by gantry robots, while conveyors transport aluminum valve bodies, front cases and converter housings in, out and within the cells.
In 2007, the Van Dyke plant installed its second MQL cell. This second-generation cell uses 54 Specht 500D HMCs from MAG Powertrain and allows the plant to realize even more appreciable benefits of near-dry machining (I’ll touch on those later). This is due in part to machine design elements specifically geared toward MQL machining, which are worth mentioning here.
Each Specht machine has a precision dosing system integrated into its motorized spindle housing to enable effective aerosol delivery through tools. The machine’s CNC communicates directly with the MQL sub-system to adjust a dosing valve to deliver the proper amount of lubricant at the proper duration for a particular operation. (Specifically, a parameter in the part program varies the amount and duration of lubricant delivery). The lubricant is mixed with air to form the desired air/oil aerosol mixture, and the aerosol is then sent to the cutting edge through ducts in the tool. The aerosol is switched off when the tool is not cutting so oil doesn’t collect on the workpiece or machine surfaces.
These machines also enable effective chip handling. After a cutting operation, the machine’s A-axis trunion design enables the table to tilt and dump chips off the part and fixture. Steep, 55-degree walls inside the machine help near-dry chips fall down and into an exiting airstream. An enclosed machining environment kept under negative air pressure enables that airstream to pull chips and any oil mist out of the machine and through a centrifuge and filter system designed by Handte. Dry chips exit this system and collect in a hopper on the side of each machine, while clean, office-quality air is returned to the plant.
Specific, Significant MQL Benefits
MQL has delivered on the two prime drivers for its adoption at Van Dyke. From a total cost of ownership perspective, which considers machine cost, downtime, maintenance, floorspace, electricity usage, coolant management and related factors, MQL has yielded a 13-percent improvement versus comparable wet operations. As for environmental impact, MQL has been a key factor in the plant’s successful efforts in delivering no manufacturing by-products to landfill. But consider these other interesting ways the Van Dyke plant has benefitted from implementing its MQL strategy.
Para leer el artículo completo deben seguir hacia el artículo en MMSonline.