Boosting Multi-Spindle Productivity
Here's a look at some of the ways Delta Faucet is taking advantage of off-the-shelf technology to improve multi-spindle screw machining productivity.
Multi-spindle screw machines are the fastest growing part of the machining department at Delta Faucet's newest manufacturing facility in Jackson, Tennessee. The dozen or so multi-spindle machines, all but one of which are automatics, are impressive in their own right, but the real story here is the way that the plant has enhanced the machines with standard, readily available, off-the-shelf technology to fully exploit their productive potential.
A large component of that off-the-shelf technology is the machining attachments used on several of the multi-spindle screw machines. They were provided as parts of turnkey installations by the machine tool manufacturer, Gildemeister Italiana (GITAL), represented in the United States by DMG America Inc. (Schaumburg, Illinois). The machining attachments permit machining faucet components complete in one setup, eliminating the need for secondary machining. It is standard operating procedure at the Jackson plant that all parts be machined complete in one setup. In fact, the plant has no secondary machining capability.
Ken Myers, director of manufacturing services for Delta Faucet, explains that the 390,000-square-foot Jackson plant, built in 1994 and the newest of the firm's three U.S. manufacturing facilities, provides the additional capacity the company needs to expand existing product lines and add new ones. Established sister plants in Greensburg, Indiana, and Chickasha, Oklahoma, are operating at capacity, and as new products come on stream at those two facilities, production of established faucet lines is shifted to Jackson. The Jackson plant is not only expected to machine the components for those faucet lines—and for faucets still being made at its sister plants—but to machine them more efficiently and economically, hence the emphasis on machining parts complete in one setup, and hence the attachments to accomplish that goal.
For example, one of the plant's 35-mm-capacity multi-spindles is used to produce a slip-on tub adaptor (a universal mount for various tub spouts for bathtubs) that requires a drilled and tapped cross hole on the side of the part and a chamfer and counterbore on its back end. Mr. Myers explains that the part was previously produced as a multi-spindle part at the company's Greensburg plant. However, the cross-drilled and tapped hole and the back end chamfer and counterbore were machined in secondary operations.
As originally machined, the part required extensive handling: “We'd machine the part on the multi-spindle, put it in a pan, take it to the degreaser, clean it, and then move it to a staging area for the secondary work. There was more handling of the parts through the secondary machining operations and then through cleaning again. The process not only created work-in-process inventory that took up space and had to be accounted for, but it also created increased opportunity for operators to make machining errors and for the parts to be nicked and scratched because of all the handling,” he recalls.
At Jackson, the problem was solved by equipping a new six-spindle screw machine with two attachments, shown in the photos at left, that permit the slip-on tub adaptor to be completely machined in a single setup. The first attachment is a cross-drilling and tapping attachment. When the carriage rotates the bar to the fourth station, the spindle slips out of gear, and the bar stops rotating. The attachment then drills and taps the cross hole in the part. The carriage then revolves the bar to the next station where it resumes rotating. After the front-end machining is complete and the part has been cut off, a second attachment picks off the part and presents it to a combination tool that chamfers and counterbores the back end.
“By producing the part complete in one setup on the multi-spindle, we have reduced inventory and scrap costs for the part,” Mr. Myers notes. “By eliminating the need to run the part over another machine for secondary operations, we save the setup costs, operating costs and labor costs associated with that machine; we eliminate the scrap that can result from operator errors, and the additional part handling . . . the savings are substantial.”
A few machines over, another attachment is used to drill and tap the back end of a center body adaptor for the spout for a kitchen faucet. And at the head of the line, an angular drilling attachment, as seen in the photo on this page, is mounted on one of the turrets of the plant's only CNC multi-spindle screw machine.
Asked the rationale by which jobs are assigned to the various multi-spindle screw machines at Jackson, Mr. Myers explains that parts are grouped into families of parts that may require a drilled and tapped hole on the side, a chamfered and counterbored back end, and so forth. The family of parts production methodology helps the machining department set up faster for the next job. Frequently, changing a tool or two is the only change needed to run the next part.
Jackson is geared to maintaining a buffer of several days worth of parts for its own assembly department as well as producing parts for its sister plants. Production is spread over many parts for many different products, which limits the quantity that can be made of any particular part before the machine that it is running on must be changed over to run another part.
“When Jackson opened in 1994, changeovers averaged about two per week,” notes Larry Love, the Jackson plant's primary production manager. “Of course we were making fewer parts on fewer multi-spindle machines. Today our changeovers average about two per day. There is constant pressure to move on to the next part, so it becomes imperative to run the parts in families to permit the changeovers to be made as quickly as possible.”
The machining attachments are just one arrow in Jackson's quiver of multi-spindle-productivity-enhancing tools. The Jackson plant typically assigns an operator to multiple machines to hold down labor costs. The plant is ISO 9001 certified, however, which requires that all machine operators gauge X number of parts per hour as indicated by the work instructions. That becomes difficult when part cycle times are short and the operators must divide their time between loading bars into the machine manually and checking a number of features per part for a given job. To ensure that operators have enough time to adequately inspect the parts, the machining department has installed bar loaders on selected multi-spindle machines to save the operators the time they would otherwise need to load the bars into the machines manually.
No Stopping To Load Bars
The bar loaders increase the productivity of the machines on which they are installed because they permit continuous operation. As the photo shows, a bar loader can be loaded with a bundle of bars weighing thousands of pounds. It then automatically feeds the bars one at a time as needed to the multi-spindle screw machine, permitting the machine to run continuously during breaks, during lunch, between shifts . . . even at night, during holidays and at other periods when the plant would normally be closed and the machines idle.
By contrast, the productivity of a manually loaded multi-spindle screw machine is constrained because each time the machine consumes a bar it must be shut down for the time it takes the operator to coax a fresh bar into the machine. When the cycle time of the part being run is short and fresh bars must be loaded at frequent intervals, the multi-spindle machine may stand idle for many minutes before the operator, who may be measuring parts or away from the immediate area for some other reason, can get back to the machine to load a fresh bar.
Another reason for installing the bar loaders is that Jackson is standardized on 16-foot-long bars instead of the more commonly used 12-foot lengths. The longer bars permit the machines to run for longer periods before another bar is loaded, but when they must be loaded manually, their additional weight can cause fatigue as the shift wears on. The bar loaders take the weight-lifting challenge out of operating a multi-spindle machine. The arrangement has also increased the pool of potential machine operators in the Jackson area. At the Delta Faucet plant, both women and men are operating multi-spindle screw machines.
Accumulators Pamper Parts
Delta Faucet has also made the task of running multi-spindle screw machines easier by adding accumulators, which in this case are large rotating tables that receive the machined parts as they automatically exit the machines. The accumulators can hold from a few dozen to a few hundred parts at a time, depending on their size, allowing the operator to attend to additional machines and/or other duties away from the machine for extended periods.
High tech? Maybe not, but operators are spared the need to constantly attend a machine and deal with a steady stream of parts—the stressful situation that was parodied so well in the I Love Lucy episode where Lucy gets a job taking candy from a conveyor line and loading it into boxes. With the accumulators, the Delta Faucet operators can perform the number of part inspections required, monitor the operations of the machines, keep the work area clean, even take a break, knowing that the machined parts are being safely stored.
A second advantage of the accumulators is that the parts are handled gently instead of being allowed to free-fall into a pan. Many of the machined parts are external parts, which for reasons of appearance cannot have dings or scratches. The accumulators provide the gentle handling that such parts require. And although external parts typically go through buffing before plating, the improved handling of parts in the machining department permits less aggressive mechanical finishing.
Insert-Type Cutting Tools
No aspect of the Jackson plant's machining operation has been overlooked in the effort to boost productivity. Cutting tools used on the multi-spindles are a case in point. The machining department produces some parts on a near-continuous basis, and form tools continue to be the most efficient way to produce them. However, for many other parts produced on the plant's multi-spindle machines, the more traditional brazed tools have given way to insert-type tools. And on the plant's newest multi-spindle, a CNC machine used for relatively short runs of large-diameter parts, insert-type tooling is used almost exclusively. Delta Faucet's Mr. Love explains that the insert-type tooling is easier to set, saving time during setups—an important consideration because the CNC is the machine that the department goes to when turnaround time for a job is critical.
Most of the off-the-shelf technology that Delta Faucet has purchased is portable. That is, the bar loaders, accumulators and machining attachments can be removed from one multi-spindle machine and installed on another, enabling the plant to adjust easily to future changes in the company's product lines. The firm will purchase additional multi-spindle machines as sales growth dictates more production capacity. Jackson's strategy of using readily available technology to get the most productivity from its machine tools, which has served the plant so well in the 6 years it has been in operation, will continue to prevail.
35-45 Percent Savings
The three parts shown in the photo were “inherited” by Jackson from sister plants at various times during the past 6 years. Delta Faucet's Mr. Myers reports that the savings realized by machining them complete in one setup ranged from 35 to 45 percent, mostly through elimination of secondary machining operations. He adds that the Jackson plant is completely machining the parts in less time than was required for either the primary or secondary machining operations previously used to produce the parts.
The numbers provided do not include the savings achieved through elimination of work-in-process inventory. And while the company has not attached a dollar value to the improvement, Mr. Myers attaches great importance to the fact that the machining department is able to deliver parts to its customers, its assembly operations and its sister plants' assembly operations, much faster than ever before.
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