Twin Spindle Lathe Increases Throughput With Better Quality

This company was growing at a rate of 25 to 40 percent per year since 1990 and needed to find a better way to produce turned parts. Now it produces from 40,000 to 60,000 parts per week.

Case Study From: 10/15/1998 Modern Machine Shop

Tilson Machine Works, Inc., of Old Fort, North Carolina, started with one associate in a 960-square foot shop behind the family home. It was a part-time job shop operated by John Tilson. Production was done on manual lathes, and the company served local clients. In 1988, Tilson and his three sons (Rodney, Alan and Mark) formed a partnership and new company.

The company bought its first CNC lathe, a Mazak Quick Turn 15, and one production band saw. It began producing work for a large bearing manufacturer. As its client grew, so did Tilson. Because of its production quality, quick part turnaround and willingness to take on new work, it quickly became the top supplier.

Tilson, which currently employs 70 associates, outgrew its physical space four times, ending up with two 30,000 square foot facilities, one still located behind the family home. It was a growth rate of 25 to 40 percent per year since 1990 that led Tilson to find a better way to produce turned parts rather than using one operator to run cells consisting of two CNC lathes to machine ball bearing components.

Most parts are turned components with some milling and drilling done on horizontal machining centers. Parts range in size from 3.8 inches to 12.5 inches in diameter with 90 percent of them made from 52100 steel and the balance from stainless steel. They are usually produced with stock left from final grinding after they've been heat-treated.

To produce these parts, Mazak Quick Turns were originally used. "We had previous experience with the dependability of Mazak machines before we went into business together," said Rodney Tilson, vice president of milling and maintenance. "This gave us the confidence to buy our first Quick Turn. Over the years, they've proven themselves with ease of use and endurance."

Tilson now produces from 40,000 to 60,000 parts per week with 3,000 different part numbers in lot quantities from 10 to 10,000 with an average of 250. With these new production demands, Tilson needed a turning center with even greater efficiency.

It found what it needed, a Mazak Dual Turn 20, twin spindle, twin turret lathe, through Marshall Machinery, a Mazak distributor in North Carolina. With the automatic part loader/unloader, the Dual Turn met Tilson's needs. The company bought the first two in 1996 and has added 12 more.

Mazak's Dual Turns are said to have given many benefits. The company has more throughput because of the twin spindle design. They offer greater part consistency and quality since the part is finished in a two-step process without operator handling. There are less labor requirements because automatic part loader/unloaders allow one person to run two Dual Turns, substantially increasing productivity over the previous CNC lathe cell setups.

"Mazak's machine tool technology has always been in the forefront, which allows us to have the most efficient machining operations," Mr. Tilson added. "Because of these benefits, all 35 of our machine tools are Mazaks."

With two independently controlled spindles and turrets constructed on a single base, the Dual Turn 20 delivers up to twice the output by the same operator. It automatically increases throughput by transferring the workpiece from the first spindle to the second spindle to complete both ends of a turned part.

Of the 12 tools in the turret, Tilson only uses four to five tools with redundant tools used in the other pockets for maximum spindle uptime. When a tool is near its life cycle, Mazak's tool management system automatically selects a redundant tool, allowing continuous operation.

Mazak's Tool Eye, an automatic tool presetter that automates tool measurement and reduces tool setup time, is also used to increase machining efficiency. The Tool Eye records the offset values as it contacts the tool and automatically updates tool data in the CNC control.

Mazak's DT-20 features an integral spindle/motor construction that eliminates drive belts, pulleys, gear boxes and other sources of vibration. The 2-hp spindle runs up to 4750 rpm top speed. Maximum cutting diameter is 12.6 inches. Shorter cycle time is also ensured through a quick 1.4-second tool-to-tool time and a rapid traverse rate of 1200 ipm with the X-axis and 1300 ipm with the Z-axis.

He said that Mazak's Mazatrol controller allows the company to program parts quickly because of its ease-of-use and interactive programming. The company trains CNC operators from scratch. The Mazatrol helps get the machine operators programming quickly and efficiently.

Even though Tilson devotes most of its production to serving four plants for only one customer, Mr. Tilson said this helps the company in the long term. "Other job shops must look at each job to see how it fits their equipment and people," he said. "Plus there can be many unknowns with a particular part because of a lack of experience with it." By focusing on one client, the company can offer the best efficiencies for machine use, tooling, part set-ups and personnel.

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