Shop floor improves machine tool design

Modern Machine Shop, Feb, 1989

Shop Floor Input Improves Machine Tool Design

In 1987, Kearney & Trecker Corp., 11000 Theodore Trecker Way, Milwaukee, WI 53214, and four other companies, including three manufacturers and a tool-and-die shop, embarked on a cooperative program called the Beta Test. K&T placed prototypes of its Milwaukee Matic Orion series horizontal-spindle machining center in an actual work site to better determine the needs of its customers. The program was successful for all participants, including the Bell Helicopter Textron plant in Ft. Worth, Texas.

Through the Beta Test Program, Bell manufacturing engineers and operators suggested numerous design changes while using the machine for six months. Orion's full-scale production models now incorporate suggestions from Bell and three other manufacturers who took part in the program.

At a plant running three shifts, five days a week, Bell committed production time, materials and manpower to the program. They agreed to use the machine a minimum of 40 hours a week to provide working data for K&T's equipment evaluators. Bell personnel were also required to note in a test log book all test results, maintenance procedures, adjustments and workpiece materials. In addition, Bell was obliged to allow K&T personnel access to the plant and the machine to inspect and test it during regular business hours.

The Orion unit was set up to machine metals and composite material used in critical components of the aircraft propulsion systems such as gear boxes and transmission parts. Operational efficiency improved a minimum of 30 percent to as much as 700 percent on some parts.

Four completely different part numbers, comprising as many as 14 parts, are now run in a single NC program run. Small modular fixtures are loaded on a four-sided base fixture. The parts are probed to identify their location and compensate for crooked or misaligned fixturing. The NC program then directs the machining operations for those specific parts.

To speed the process further another fixture and parts are loaded on the second pallet while parts are being machined. An expanded tool storage capacity helps further. Bell took advantage of the machine's modular design by combining two 60-tool magazines to create a system with 120 ready tools.

The machine's precision showed Bell other ways to increase efficiency. The machine was tested on a critical boring operation, which involved boring holes that intersect. The work was done previously on a jig borer--until the test machine demonstrated its capability. The time for this operation was reduced by more than 30 percent.

Bell engineers point to the machine's control and its KT-APL Advanced Programming Language as a key feature for fitting the machine to their desired operation. With the help of K&T training and application engineers provided in the program, Bell modified the system to fit its production demands.

However, as expected, the test machine needed some modifications before full production commenced. What was not resolved in design and testing at K&T became apparent on Bell's machine shop floor.

For example, the fast axis movement was impeded when the machine had to stop for a brief moment to wait for the coolant enclosure's door to open. It took more time for the door to operate at tool change than it did for the column to go back and forth. The tool-change cycle was optimized and is now standard on all Orion machines.

Other areas that were suggested for improvement: * leaks from the coolant enclosure; * way covers that buckled; * cavities that collected chips; * unclamp switches that operated with difficulty; * an enclosure door that limited visibility and access to the work space; * a portable control box cord that was too short; * a tool chain that moved backwards in the manual mode.

Bell had some additional suggestions for features not appearing on the machine: * Place a window on the tool side of the enclosure to improve visibility. * Improve access to the B-axis motor and junction box, as well as to the Z-axis motor. * Improve access to the emergency stop button.

Other suggestions came in from the three other participants in the Beta Test Program.

PHOTO : J.R. Swanner, Programming Supervisor at Bell Helicopter Textron, review a program with the

PHOTO : operator of the Orion 2300.