Turning Machines

CNC Upgrades Breathe New Life Into Brownies

Used in lean manufacturing processes, multis can suffer from long setup times. Upgraded Brownies often compete very favorably with multis on medium-length runs.


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In today’s marketplace, there is increasing demand for smaller lot sizes, delivered more frequently. Insert-type form tooling and CNC upgrades extend the economic lot size for Brown & Sharpes into the traditional CNC lathe and multi-spindle territory. Jobs can often be run on upgraded Brownies that are traditionally run on CNC lathes because of their short setup time or extended turning capacity. Multiple-spindle machines are very fast, but for simpler parts and monthly requirements of under 10,000 pieces, production speed alone may not be the issue. Used in lean manufacturing processes, multis can suffer from long setup times. Upgraded Brownies often compete very favorably with multis on medium-length runs (see chart).

The graph illustrates how the faster setups and higher gross-production rates available with CNC upgrades to Brown & Sharpe machine compress the time required to produce a run of parts. It shows part production versus time for a conventional Brownie (blue), a CNC upgraded Brownie (pink) and a conventional multi-spindle machine (yellow). The time axis starts when setup begins. At the end of the setup, each machine produces parts at different rates. In this example, lot sizes of less than 3,700 pieces are finished sooner on an upgraded Brownie than on a multi, resulting in substantial cost savings. And although the multispindle machine takes 1/3 less time to produce 10,000 pieces, totals costs at this lot size are about the same because of setup labor savings and different hourly machine rates.

Even with the current economic downturn, there remains a lack of skilled labor to set up Brown & Sharpe machines. Entry-level workers are not easily attracted to cam-operated screw machines. But upgraded machines run quieter, the skill level is simplified and each skilled worker can produce more parts. CNC upgrades improve productivity while making the job more attractive to current and future employees.

Some of the most successful Brown & Sharpe shops in the marketplace today have done two things to ensure a profitable spot for themselves. One, they have defined a niche market. They concentrate on machining brass, stainless, alloy steel and so on, or they have a product area on which they focus their manufacturing capabilities. Two, they have reduced their costs by reducing setup time, decreasing cycle time, eliminating secondaries and reducing scrap. They have focused on labor cost because it is the one item over which they have significant control. Material, electricity, housing, insurance . . . these are relatively fixed costs. These successful companies have not tackled labor costs by paying lower wages; in fact, many very successful companies pay above-average wages. Rather, they have made a point to keep current on productivity issues, whether they relate to internal or external processes.

How Upgrades Work

On most lead cams, at least 20 percent of the cam surface is wasted on non-cutting time, which is unavoidable. AMT Machine Sysytems (Columbus, Ohio) manufactures a Brownie upgrade system called ServoCam that helps eliminate that wasted time. The standard turret-slide upgrade provides a high-acceleration servomotor and ballscrew drive, controlled by software that is written specifically for single-spindle screw machines.

A Browne & Sharpe that has been upgraded has a true CNC turret slide. All of the conventional turret-slide linkage is removed, along with the RPO mechanism. This eliminates a major source of part-length variation and results in a quieter-operating machine. These changes also enable the use of feed rates developed for CNC lathes. Combined with reductions in non-cutting time, gross production rates are typically doubled.

Removing the mechanical linkage also enables the use of the full stroke of the machine. On #2 Ultramatics, for example, this means a full 7 inches of turret stroke is available. With this increased stroke, many parts can be run on an upgraded Brownie that otherwise would require a CNC lathe. The extra capacity can also eliminate some secondary operations.

As part of a conventional Brown & Sharpe upgrade, AMT can install a new AutoTripper option. This option automatically controls the spindle transmission, bar feeder, turret indexer and the part deflector. Timing of these functions is programmed in software, eliminating the need to set mechanical trip-dogs. Actuation timing is accurate to 0.05 seconds. Automatic tripper timing also makes it quick and easy to optimize feed rates—real-time feed rate changes can be made and tested in only 5 minutes. The improved speed, precision and versatility transform a conventional Brown & Sharpe into a new class of machine.

With the AutoTripper option, ServoCam users generally report total setup time reductions of 50 percent or more. There are no trial-and-error timing adjustments during setup, even for tap reversal. The printed layout sheet specifies the exact lengths that tools should project from the turret, allowing the tooling to be preset. Turret-tool offset adjustments are quick and precise—CNC keypad entry makes this simple, even for inexperienced operators. Because the turret clamp bolts are not loosened for tool adjustments, there is never a risk of losing the tool centers. Precise feed rates and automatic tripping result in high-quality threads on the first try.

Laying out a job using the software provided with ServoCam, including printing the layout sheet and writing the “cam” diskette, takes less than 30 minutes. Cam diskettes can be immediately loaded in the controller, which contributes to process versatility.

No prior cam layout training is necessary to use the cam design software. Most shop personnel can become proficient with the software after only a few layouts. System installation typically takes less than 2 days and can be done on the shop floor. Operator training takes only a couple of hours, and then the machine is back in production.

The payback period for ServoCam upgrades is typically under 1 year. Among the more than 100 Brown & Sharpe shops using this upgrade system, many enjoy payback periods of 6 months or less.

Among the more than 100 shops that have upgraded to ServoCam for Brown & Sharpes is G&G Manufacturing Company in Cincinnati, Ohio. The programmability and rapid changeover provided by the upgrade allows this shop to handle much smaller job lots than were previously feasible.

Replacing much of the mechanical linkage and cam actuation with servo/ballscrew drives reduces parasitic time during the cycle and results in a stronger, more accurate axis feed.


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