Automatic drilling of small-bore cylinders.

Automatic drilling of small-bore cylinders

When a manufacturer of small-bore pneumatic cylinders decided to automate holemaking operations, results were anything but small time. Compact Air Products Inc, Westminster, SC, makes a broad assortment of small-diameter pneumatic cylinders. Sizes range from 1 1/4 [inches] square to 4.0 [inches] dia round, in lengths from 7/8 [inches] to 4.0 [inches] in several body styles.

According to company president, Larry Yuda, the decision to automate was fairly straightforward. "We drill and tap between 20,000 and 25,000 holes per week. Each cylinder normally has two air ports, two to four mounting holes, and two wire holes. In addition, we drill several types of mounting hardware."

Formerly, all work was performed on a series of bench-mounted drill presses. The sheer volume of work, combined with the accuracy demanded of the drilling department and the amount of labor hours required, led to the development of the factory-assembled ADMs (automatic drilling machines).

Although many people relate dedicated drilling machines to high-volume operations, typical production quantity for Compact Air in a given size is 50 to 250 pieces.

The cylinder-drilling machines are capable of running 3/4 [inches] through 2 [inches] bore, square barrel; and 3/4 [inches] through 3 [inches] bore, round barrel.

Faced with the classic "make or buy" decision, Yuda decided that his engineering department could design the machine, and his shop could build it at a lower cost and with less lead time than required from outside machine-tool builders. Machine bases were fabricated from 2 [inches] plate stock, but the real key was in locating drilling spindles that had the required speed and accuracy for high-volume, close-tolerance holemaking. The company chose a series of automatic modular drilling machines made by Suhner Industrial Products Corp.

Each of four machining tables is set up with three SUmatic self-feed drill units. Generally, each table is designed to accommodate a particular size range of products.

Two of the four work stations are dedicated to standard production drilling, while the third station includes an additional spindle to facilitate left-hand or right-hand ported cylinders. Simply by turning a switch, the operator is able to produce the left-hand version of a standard cylinder.

The fourth station performs the largest range of drilling operations. This station features a programmable peck-feed controller, thus enabling the operator to select a one-, two- or three-stage drilling process.

One major feature of the system is the ability to change tooling quickly to accommodate production shifts. Changeover is accomplished simply by changing drill sizes and collets. Multi-drill heads allow for rapid changeover with minimum downtime. Since many orders call for some type of customization, this ability to respond rapidly has been a major factor in the success of the company.

Aluminum cylinder bodies are manually placed in parts fixtures. From that point, all work is automated. Compact Air Products used its own cylinders to clamp and secure the workpiece in place. Each of three spindles work simultaneously while sensors monitor the process, so that drills cannot operate when the workpiece is not in proper position.

In commenting on the success of the operation and on the performance of the ADMs, Mr Yuda states that "this system allows us to perform in minutes what formerly would have taken a month to do manually." Drilling accuracy is also improved, and, with respect to reliability, one drilling center is equipped with a counter that currently shows over 75,000 cylinders that have been successfully machined.

Compact Air still uses the bench-mounted drill presses for special-purpose and nonstandard cylinders that account for about 30 percent of its orders, and for robotic grippers that account for a growing percentage of its total product line.

For more ADM information, contact Suhner Industrial Products Corp, PO Drawer A, Hwy 411 South-Suhner Dr, Rome, GA 30162-1234.