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Simultaneous engineering spells cell success.

A cross-functional approach to planning and clear, well-defined performance objectives are crucial to the success of a manufacturing cell.

To produce its KM quick-change tooling system, Kennametal Inc developed two identical manufacturing cells located in plants in Cleveland, OH, and the United Kingdom. The KM system consists of a cutting unit with a tapered quick-change connection and a matching clamping unit. With the system available in four standard sizes and a range of cutting units, the cells had to be designed to machine any of 1200 different standard parts and several hundred specials.

Prior planning

Planning for the KM product--and for the cells to manufacture it--began when a team of Kennametal manufacturing engineers met with representatives from the company's new product design team. Marketing representatives also offered several market-driven parameters for the manufacturing group to consider.

The cross-functional team clearly defined project objectives in seven areas, including:

* Product quality

* Manufacturing cost

* Leadtimes

* Lot sizes

* Cell expendability, flexibility, and adaptability

The team developed a number of processing alternatives and assigned members to evaluate the choices. All the machines eventually purchased included features to facilitate minimally manned or unmanned operation as well as fast changeover. The machines, and some key features that help the system meet the objectives, were:

* A 25-hp CNC turning center, with 26-station workfeeder and robot, 30-tool automatic toolchanger, tool management, and a quick-change chuck.

* A CNC four-axis horizontal machining center with 50-tool automatic toolchanger and tool management for milling and drilling on the taper end of the cutting unit.

* A five-axis machining center with 120-tool automatic toolchanger and 40-pallet automatic workchanger. The workchanger uses Kennametal's Microlog system to recognize the part being loaded and activate the proper program in the machine control.

* A CNC cylindrical grinder finishes the OD taper. The grinder is equipped with a gaging system, variable-speed wheel, and a door open/close feature.

* A CNC grinder with four high-frequency spindles and four axes under program control for ID grinding. The fourth axis allows for swivel of the workhead under program control to permit rapid changeover from straight to taper grinding.

The basic cell layout guideline was that all operations except heat treating were to be completed within the cell. The team examined work flow with the goals of eliminating material handling equipment and large work-in-process inventories. The design also lets attendants, who are cross-trained to operate any of the six machines in the cell, integrate quality checks, tool presetting, work scheduling, and cooperative problem solving with their normal machine load/unload and tool maintenance responsibilities.

Precise performance

In operation, work flows from the CNC lathe into the four-axis machining center. After initial milling, the parts are loaded into either of two five-axis machining centers for front-end pocketing operations. The parts are then heat treated before final grinding.

Cell control is by a distributed numerical control (DNC) system called NCNet from RWT Corp. The DNC system provides access via an Ethernet network to the host computer for CNC programs and other process documentation.

Unigraphics CAD/CAM software is used for CNC programming, and programmers can access standardized 3D models created by design engineers in Raleigh, NC. Completed programs reside in the host computer and are available through the DNC network to cells on the shop floor. Programs created in Cleveland can be used in the UK and vice versa.

Each machine in the cell also has a specially designed workholding system. The CNC turning center was purchased with a quick-change chuck, and Kennametal tooling engineers designed quick-change collet pads to handle a range of part diameters. Attendants can rapidly replace the chuck jaws to handle non-standard parts. A hydraulically operated, multiple-part tombstone fixture mounts on the pallet shuttle system of the four-axis machining center.

A number of different fixtures are required on the five-axis machines. For pocket milling, a modified KM clamping unit holds the cutting unit blank for machining. Parts are inspected 100%, and results are logged by fixture number into a computer in the cell to permit monitoring of fixture wear and help attendants pin-point repair needs.

On the OD grinder, a unique expanding mandrel holds the part in an area that is consistent part to part regardless of front-end design. Changeovers, performed only when changing basic system sizes, require only a change of the expanding mandrel. For the ID grinder, Kennametal purchased a workhead fitted with a camlock #6 spindle nose and commissioned the grinder builder to develop a quick-change holding system to fit.

Cell attendants are responsible for product inspection. Granite surface plates and a digital height gage, as well as several functional hard gages, are provided in each cell. Cell attendants also perform statistical process control (SPC) charting. Quality engineers work closely with the attendants to improve quality levels and ensure consistency.

Follow up

Successful implementation of the cell concept for machining KM tooling was the result of the work of a cross-functional team consisting of manufacturing, design, and quality engineers, programmers, tool designers, and cell attendants. The team's careful planning paid off with twin cells that have consistently met the objectives set by the planning team. Working five days a week, 24 hours a day, they have operated at 99.4% of the production plan for standard and special products.

Manufacturing costs have been consistent with the goals set by Kennametal's marketing group, and the short, dependable leadtimes for products destined for stock permit small finished goods inventories.

Product quality has been consistent, and efforts at reducing setup time have paid off in the ability to economically produce lot sizes as small as one part for repeat orders where fixturing, programming, and tooling are already proven. Lot sizes average 17 parts for standard products and seven for specials.
COPYRIGHT 1993 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1993 Gale, Cengage Learning. All rights reserved.

Article Details
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Author:Martin, Steven E.
Publication:Tooling & Production
Date:Apr 1, 1993
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